JPS63199244A - Biaxially oriented polyester film - Google Patents

Abstract

PURPOSE:To obtain a film having excellent abrasion resistance and slipperiness with scarce dropout, by containing inert particles and fine silica particles in a polyester deposited in a reaction system. CONSTITUTION:A biaxially oriented polyester film obtained by containing 0.05-1.0wt.% inert particles and 0.001-5wt.% monodisperse fine silica particles having a volume shape coefficient satisfying the formula 0.4<=(V/D<3>)<=pi/6 [V is particle volume (mu<3>); D is the maximum diameter (mu) in the plane of projection], 0.1-5mu average particle diameter and <=5% deviation therefrom. The inert particles are particles respectively containing >=1.0wt.% calcium, lithium and phosphorus. The number of the n-order interference fringes is Hn (fringes/ cm<2>) obtained by measuring the film surface by a two-beam interference method satisfies the formula SIGMAHn<=20, n>=3 and Hn/Hn+1>=10.

Description

[Detailed description of the invention] (Industrial application field) The present invention is directed to polyester films.

More specifically, ifCjA is a nine-biaxially stretched polyester film that is particularly suitable for use as a base film for magnetic tapes with excellent abrasion resistance and extremely low drop-act.
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(Problems to be solved by conventional technology and the invention) Polyester films used today have different required properties depending on their use. It is required to have excellent wear resistance and to have few rough protrusions on the surface that cause drop-act.

The abrasion resistance is also a necessary property in the b-shifting process before and after applying the magnetic layer, and it is necessary to suppress the formation of white powdery substances due to friction and abrasion between the polyester film and the roll or at the guide portion as much as possible.

In addition, the magnetic tape film that has become a product is exposed to harsh conditions such as repeated running, sudden stops, and sudden starts. A white powdery substance may be formed due to friction.

The production of this white powdery substance causes so-called dropout, that is, the loss of audio, image, and other signals, which is a fatal defect in magnetic tape films.

It is known that in order to improve the abrasion resistance of a film, fine particles inactive to polyester may be present in the polyester film to appropriately roughen the film.

Furthermore, as a base film for magnetic tape, in addition to good abrasion resistance, it is also required to have particularly good cleanability and to have little dropout when made into a product.

The present inventors have previously developed a method for effectively improving these properties, including wear resistance. j-4t09-9
Publication and JP-A-Sho! This was proposed in the method described in JP 7-201217.

These methods involve the presence of multiple particles inert to polyester in the polyester film;
In recent years, base films have been required to have more excellent properties than ever before, and in order to satisfy these demands, even higher quality improvements are required.

(Means for Solving the Problems) The present inventors have developed a magnetic tape that has extremely excellent abrasion resistance that has not been achieved hitherto, satisfactorily satisfies lubricity, and has low drop-act. The present invention was achieved as a result of intensive research aimed at providing a polyester base film.

HIJ, the gist of the present invention is to use particles of 0.02 to 7.0 weight #, %, inert to the polyester precipitated in the reaction system.
And the volume shape coefficient satisfies the following formula F11, the average particle size is o, i~! Monodispersed silica fine particles with μ and a deviation from the average particle size of j% or less are 0.00/~! It is a biaxially stretched polyester film specially designed to contain S.

θ-4t≦φ7≦7 (11 and below, the present invention will be described in detail.

In the present invention, it is necessary to contain 0.0j to 7.01% by weight of inert particles with respect to the polyester precipitated in the reaction system. The content of the inert particles is 0. If O is less than 1% by weight, the surface roughness will be too low and the lubricity will deteriorate, which is not preferable. On the contrary, OJ! If the amount is too large, the surface degree will be too rough and the electrical properties of the magnetic tape will deteriorate, which is undesirable. In addition, the average particle diameter θ・so that the volume shape coefficient satisfies the above formula (1) in combination with the inert particles
/~! , Qμ, and the deviation from the average particle size is j% or less, monodispersed spherical silica fine particles are 0.00/~! It is necessary to contain it by weight%.

If the average particle diameter of the silica fine particles is smaller than 0./μ, the silica fine particles will aggregate and become coarse protrusions when formed into a tape, which is not preferable. vice versa! If it is larger than μ, it is not preferable because it will result in coarse protrusions when formed into a tape. In addition, the content is 0.
0θ/fti: This is not preferable because h is smaller than X and no effect of improving wear resistance is observed. On the other hand, if the amount is more than 1% by weight, it is not preferable because the uneven surface roughness becomes rough and causes a decrease in stain resistance and drop-out.

In addition, examples of inert particles precipitated in the reaction system include:
Examples include those made of calcium and a phosphorus compound, or those made of calcium, magnesium and a phosphorus compound, but particularly preferred in the present invention are those made of calcium, lithium and a phosphorus compound.
Furthermore, each of these is contained in an amount of 0 weight or more based on the precipitated particles. This is related to the formation of fine irregularities on the film surface and will be described in detail later.

Furthermore, when the number of n-th interference fringes when the film surface is measured by two-beam interferometry is Kn [pieces/d], if the following formulas (2) and (3) are simultaneously satisfied, the resistance This is preferable because it is possible to obtain an extremely high quality base film that has excellent abrasion resistance and has an extremely small number of dropouts.

ΣHn≦λo, n≧3 (2) Kn +1≧″・rs”j−j −−−−= (31 The feature of the biaxially stretched polyester film of the present invention is that the film This is due to the structure of the particles that create unevenness on the surface.

Conventionally, in order to control the surface roughness of a polyester film, there have been known methods in which fine particles inert to polyester are present in the film, such as the so-called particle addition method and particle precipitation method, but in the present invention, the latter method is used. A particle precipitation method is employed.

The particle addition method involves pulverizing and classifying kaolin, talc, calcium carbonate, calcium phosphate, etc. to a certain particle size, and then adding it to the polyester reaction system or during molding.

In addition, the particle precipitation method is a method in which metal compounds such as calcium compounds and lithium compounds that are soluble in ethylene glycol and polyester oligomers are precipitated as fine compounds during the polyester formation reaction in the presence or absence of phosphorus compounds. . Of course, when these metal compounds are added at the beginning of the transesterification reaction, they can also function as a catalyst.

Comparing the particle addition method and the particle precipitation method, the particle precipitation method makes it relatively easier to create many critical irregularities on the film surface, improving lubricity without impairing dropout characteristics. can be done. In the particle precipitation method of the present invention, it is particularly preferable that a phosphorus compound be present in an amount substantially equal to or greater than the metal compound added to precipitate fine particles of phosphoric acid or phosphite derivatives. This is because, in this case, unlike fine particles of metal salt derivatives of polyester oligomers, they generally have good affinity with polyester, so when stretched, the voids generated around the particles are small, and therefore they are not preferred as base films for magnetic tapes. This is because the phenomenon of gentle spreading around particles is reduced.

In the present invention, calsilafutolithium is used in combination as the above metal compound, and particles are further precipitated in the presence of a phosphorus compound, so that calcium, lithium, and phosphorus elements each contain 7.0% by weight or more based on the precipitated particles. It is particularly preferable that

In this case, a large number of steep and uniform fine protrusions can be formed on the film surface, and the effect of improving lubricity is extremely large.

Although it is possible to improve the lubricity without impairing the drop-act properties by using the above-mentioned precipitated particles, the wear resistance is not necessarily satisfactory.

As a result of intensive studies on improving the abrasion resistance of the film, we found that the abrasion resistance could be improved by adding new particles that give large irregularities to the fine surface irregularities formed on the film surface (using the particle precipitation method). It became clear that Therefore, various particles were investigated as additive particles, but in most cases it was difficult to satisfy both wear resistance and drop-act characteristics. That is, this is because coarse protrusions caused by coarse particles or aggregates in the particles added to improve abrasion resistance appear on the film surface, significantly increasing drop act. Note that the coarse protrusions on the film surface herein refer to protrusions that give rise to third-order or higher-order interference fringes when measured by the two-beam interferometry described above.

As a result of careful consideration regarding the selection of additive particles, it was found that silica fine particles that satisfy specific conditions are not found in other particles and provide extremely excellent properties.

That is, in the present invention, a coaxially stretched film is obtained using polyester containing precipitated particles and additive particles as a raw material, but in this case, as the additive particles, the volume shape coefficient is expressed by the following formula (1).
By adopting a special combination of using monodispersed spherical silica particles with an average particle diameter of 0,/~jμ that satisfies You can obtain a film that satisfies you.

0.4t≦φ7≦−7:::・・・・・・(13The volume shape factor represents the degree of sphericity of the particle.
/6, close to a seed ball shape. (If it is perfectly spherical, it will be π/b) Also, the degree of monodispersity here refers to the deviation of the particle size of each particle from the average particle size! It shall be less than or equal to X.

Note that the particle size of the silica fine particles is a value determined by observing the particles using an 81CM (scanning heavy electric semi-microscope).

These spherical silica particles are different from conventional silica particles.
It was only possible to manufacture it using a special method as described below.

That is, it is produced by a hydrolysis reaction and a condensation reaction using an amine catalyst using disilane in alcohol as a starting material.

As the alkoxysilane compound, compounds of the general formula % formula % are used, specifically compounds such as disilane in tetrameth, tetraethoxysilane, and tetrapropoxysilane.

As the amine catalyst, ammonia, trinotylamine, tetraethylammonium, urea, etc. can be used, but an ammonium aqueous solution is particularly preferably used.

A precipitate of liquefied fine particles is produced by adding an amine catalyst to the above-mentioned alkoxysilane compound and causing a hydrolysis and condensation reaction.

After the reaction is completed, ethylene glycol is added to the suspension and then distilled to remove moisture and the like, yielding an ethylene glycol dispersion of silica fine particles.

The silica fine particles used in the present invention have the following practical advantages compared to other additive particles.

(2) Since they are almost perfectly spherical monodisperse particles having a volume shape coefficient that satisfies the above formula (1), there are no coarse particles with abnormally different particle sizes or shapes.

(2) Individual particles are stable in a particle dispersion (examples of dispersion medium include water or ethylene glycol), and no aggregation of particles is observed.

In films to which particles other than spherical silica particles are added, coarse protrusions are formed on the film surface, where coarse particles and aggregates of particles in the added particles become M-traps, and these coarse protrusions cause dropouts. Ta.

In addition, these coarse protrusions were easily scraped off by friction between the film and the base material, and in some cases showed a tendency to deteriorate the wear resistance.

On the other hand, in the case of the film of the present invention to which spherical silica fine particles having the above-mentioned characteristics are added, in order to further improve the abrasion resistance, the particle size of the silica fine particles to be added is increased or the film is added. Even if the total amount is increased, the number of coarse protrusions on the film surface is extremely small. Therefore, it is possible to simultaneously and highly improve both wear resistance and drop properties.

In addition, when the protrusions formed on the film surface are observed in detail, the protrusions are much steeper than in the case of other additive particles, which is why it is thought that the effect of improving wear resistance is extremely large.

Next, an example of a method for producing a polyester containing precipitated particles particularly suitable for use in the present invention will be described in more detail below.

For example, the polyester containing such particles is prepared by carrying out a transesterification reaction in the presence of a lithium compound and a calcium compound, and after completion of the transesterification reaction, a polyester containing phosphoric acid, phosphorous acid, or an alkyl ester thereof or an aryl ester thereof. It can be obtained by adding one or more selected compounds in an equivalent amount of 0.6 to 3 times the total amount of these metal compounds, and then performing a polycondensation reaction.

The lithium compound used in this case may be one that dissolves in the esterification or transesterification reaction product.
Examples include salts of aliphatic carboxylic acids such as acetic acid, propionic acid and butyric acid, salts of aromatic carboxylic acids such as benzoic acid and p-methylbenzoic acid, and lithium glycolates such as ethylene glycol and propylene glycol. can.

Among these, lithium aliphatic carboxylates, particularly lithium acetate, are preferred. The amount used is preferably from 0.03 to 0.0 mol S, particularly 0.07 to 0.3 mol S, based on the aromatic dicarboxylic acid component.

There are no particular restrictions on the calcium compound as long as it is soluble in the esterification or transesterification reaction product, such as salts of aliphatic carboxylic acids such as acetic acid, propionic acid, butyric acid, benzoic acid, p-methyl Examples include salts of aromatic carboxylic acids such as benzoic acid, as well as calcium hydroxide such as ethylene glycol and propylene glycol. Among the aliphatic carboxylic acids, calcium 9
In particular, calcium acetate is preferably used.

In addition, the amount of the nuclear lucium compound is 0.0j to 0.3 mol S1, especially 0.0r to θ.
/! Mol S is preferably used.

The phosphorus compound may be any compound as long as it reacts with the above-mentioned metal compound and converts part or all of it into a phosphate or phosphite derivative, but especially phosphoric acid and trialkyl esters of phosphoric acid. , a partial alkyl ester of phosphoric acid, phosphorous acid, a trialkyl ester of phosphorous acid, and a partial alkyl ester of phosphorous acid are preferably used.

The amount of these phosphorus compounds added is 0.4 to 3 times equivalent, preferably o, r to co times equivalent, more preferably 0.4 to 3 times the amount of the total amount of the metal compounds. Ri~hachi! Double equivalents are used.

Here, the equivalent ratio of the phosphorus compound to the metal compound is expressed by the following formula % (in the formula, p, a6, and Ll represent the number of moles of the phosphorus compound, calcium compound, and lithium compound, respectively).

By using a metal compound and a phosphorus compound in combination as described above, precipitated particles containing the metal element and phosphorus element used in the particles can be obtained.

Of course, part or all of the lithium compound or calcium compound may be added after the transesterification reaction is completed.

In order to achieve the object of the present invention, the amount of particles containing lithium, calcium and phosphorus elements precipitated in this polyester should be 0.00000000000000 with respect to the polyester film. Oj〜/・
0 weight S1 preferably 0, Oj -0,4I weight S, more preferably 0.0≦~o,i selected from the range of weight %. In this case, the amount of precipitated particles is determined as follows.

(Quantification of precipitated particles in polyester film: Polyester/00 JF Ko-chlorophenol/・OL
was added and heated at 710°C for 3 hours.
Centrifugation is performed for tO minutes and the resulting particles are vacuum dried at 100°C. The particles are measured using a scanning differential calorimeter, and if a melting peak corresponding to the polymer is observed at 9 o'clock, 0-dichlorophenol is added to the particles, and after heating and cooling, centrifugation is performed again. When the melting peak is no longer observed, the particles are treated as precipitated particles and the weight ratio to the polyester is calculated. ) The polyester constituting the biaxially stretched polyester film of the present invention has a main repeating unit, that is, at least /
The polyester is made of polyester having ethylene terephthalate in θ mole %, and may contain less than 20 mole % of a dicarboxylic acid component, a glycol component, or an ino dicarboxylic acid component as other constituent components.

Additive particles such as spherical silica particles can be added before, during, or after polyester polycondensation reaction, but it is especially preferable to disperse them well and add them in a large state as ethylene glycol slurry before polycondensation reaction. . In this case, effective dispersion can be achieved by performing high-speed stirring or ultrasonic dispersion, if necessary.

Biaxially oriented polyester film is made by melt extruding polyester in a conventional manner, then sequentially or simultaneously biaxially stretching, and if necessary, stretching again in the longitudinal or transverse direction, at a temperature of /30 to a4 ta℃. obtained by heat setting.

As detailed above, the present invention requires the use of spherical silica fine particles that meet specific conditions among many particles that are inert to polyester, and by making the polyester film develop a specific surface condition, This film achieves an extremely high degree of improvement in the abrasion resistance and dropout characteristics of the film without impairing the properties necessary for a base film for magnetic tape.

The film obtained by the method of the present invention is particularly effective in improving properties in areas with small surface roughness, and is particularly suitable as a base film for video.

(Examples) Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples as long as the gist thereof is not exceeded.

In addition, "parts" in Examples and Comparative Examples indicate "parts by weight."

The method for measuring this characteristic is as follows.

/) Abrasion resistance The film was run for 7,000 ryh using the running system shown in Figure 1, and the abrasion white powder t adhering to a fixed bottle made of hard chrome with a diameter of 3 was visually measured, and good examples were conducted according to the ranks shown below.

The film speed is /θ-/min, and the tension is approximately 2007
71θ=/3o0.

Rank A: No adhesion Rank C: A small amount of adhesion Rank C: A small amount of adhesion (more than rank B) Adhesion Rank D = Very much adhesion 2) Smoothness Is the slickness of the film ASTM D/r? Evaluation was made by measuring the coefficient of friction according to the method of 4t-43.

3) A magnetic layer was coated on the film using a known drop-at method (for example, the method described in Japanese Patent Application Laid-Open No. 2003-120001-4T!302) so that a dry thickness of 4 was reduced to scraps, and the film was dried.

Next, the obtained magnetic tape is supercalendered, slit into % inch width tapes, and a signal is output using a Drop Act Katsunta manufactured by Japan Automatic Control Co., Ltd.!
Those with a θ ratio or lower that were due to the base film were counted.

(i) Added particle size The spherical silica fine particles were directly measured by 8XM (scanning electron microscope) observation. Other added particles were measured by centrifugal sedimentation.

Interference fringes were produced at measurement wavelengths θ and j4tμ for a sample in which aluminum was vapor-deposited on the surface of a two-beam interferometry film, and the number (Hn)' of interference fringes of the nth order was counted.

(Example/) 700 parts of dimethyl teretalate, 20 parts of ethylene glycol, 0.170 parts of calcium acetate hydrate, and 0.17 parts of lyticum acetate hydrate were placed in a reactor, heated to raise the temperature, and methanol was removed. Perform transesterification reaction,
After the reaction starts, it takes about 10 hours to reach 130℃! The transesterification reaction was substantially completed.

Next, after heating the reaction product to λjj'c, 0.30 parts of triethyl phosphate (62 times equivalent to the metal compound) was added, and further 0.0 part of antimony dioxide was added, and then the reaction product was heated according to a conventional method. A polyester was obtained by combining the polyester. (Raw material) In the polyester, many uniform and fine precipitated particles containing calcium, lithium, and phosphorus elements with a particle size of O0j~/μ are observed, and the amount is O-9 heavy iX with respect to the polyester.
Met.

On the other hand, in the production of raw material, calcium acetate hydrate 0. /
After carrying out the transesterification reaction using only 0 parts, 1 part of phosphoric acid O, O4, 0.0 part of spherical silica fine particles with a particle size of 0.2 μ, and 0.0 part of antimony trioxide were added. A polyester containing spherical silica particles was obtained in the same manner as the raw material. (Raw material B) Next, raw material A1 B'ij ge! After mixing in a blender to achieve a weight ratio of 0 and drying, M melt extrusion was performed at 221°C to obtain a thickness/l! An amorphous film of μ was obtained.

The film was then stretched 3.1 times in the longitudinal and transverse directions, heat-set at 0° C., and then cooled to obtain a biaxially stretched film of /jμ.

As a result of measuring the narrow surface protrusions of the film by two-beam interferometry, the number of coarse protrusions that produce third-order or higher order interference fringes was 12/d. Table 7 shows the evaluation results of abrasion resistance, lubricity, and dropout for this film.

(Example 2) A biaxially stretched polyester film was obtained in the same manner as in Example 1, except that the particle size and content of the spherical silica fine particles contained in the polyester film were changed as shown in Section 1i). The evaluation results for this film are shown in Table 1.

(Example 3) A coaxially stretched polyester film was obtained in the same manner as in Example, except that the particle size and content of the spherical silica fine particles contained in the polyester film were as shown in Table 2. The evaluation results for this film are shown in Table 7.

(Comparative Example/) A polyester film was obtained in the same manner as in Example/, except that raw material A was used alone. The evaluation results of the film are shown in the first difference.

(Comparative Examples 2 to 6) Examples/Examples except that the type, particle size, and content of the additive particles contained in the polyester film are shown in Table 7.
A coaxially oriented polyester film was obtained in the same manner as above.

The evaluation results for this film are shown in m/i.

Examples/--3 were all cases in which spherical silica particles were added, and the abrasion resistance was extremely excellent. Furthermore, there were few coarse protrusions on the different surface of the film, and the number of drops was also significantly reduced. It also has excellent lubricity.

In addition, in Example 3, the particle size was 1. ! Since # and large particles are added, the lubricity is even better, but the number of coarse protrusions is different from that in Example 1. - The number of dropouts has increased slightly since the number of dropouts has increased compared to -. However, it is much better than cases where other additive particles are added.

Comparative example is a case of only precipitated particles and no added particles.
o, abrasion resistance is extremely poor. As a result, abrasion white powder generated (due to abrasion) is transferred to the magnetic layer side of the tape, and dropouts are extremely common even though there are few rough protrusions on the six sides of the film.

Comparative Examples λ to B generally have inferior abrasion resistance compared to the case where spherical silica fine particles are added, and moreover, there are many coarse protrusions on different surfaces of the film, and dropouts are extremely frequent. Even in the case of lithium fluoride, which has a relatively good effect of improving wear resistance, when trying to achieve wear resistance equivalent to that of spherical silica fine particles, the number of coarse protrusions increases and dropouts increase. (Comparative Example 3) (Effects of the Invention) The two-wheel stretched polyester film of the present invention has highly improved abrasion resistance and dropout characteristics, and is suitable as a base film for magnetic tape.

[Brief explanation of the drawing]

Claims (3)

[Claims] (1) 0.05 to 1.0% by weight of particles that are inert to the polyester precipitated in the reaction system, and a volume shape coefficient that satisfies the following formula (1) and an average particle size of 0.1 to 5μ A biaxially stretched polyester film containing 0.001 to 5% by weight of monodispersed silica fine particles having a deviation from an average particle size of 5% or less. 0.4≦φ_v≦π/6……(1) (However, it shall be defined as φ_v=V/D^2. V: Particle volume [μ^2], D: In the projection plane of the particle Maximum diameter [μ]) (2) A patent characterized in that the particles inert to the polyester precipitated in the reaction system are particles containing 1.0% by weight or more of each of the elements calcium, lithium, and phosphorus relative to the inert particles. A biaxially stretched polyester film according to claim 1. (3) When the number of n-th interference fringes when the film surface is measured by two-beam interferometry is H_n [pieces/cm^2], the following formulas (2) and (3) are satisfied. A biaxially stretched polyester film according to claim 1 or 2. ΣH_n≦20, n≧3……(2) H_n/H_n_+_1≧10, n≧3……(3)