JP2528959B2 - Polyethylene-2,6-naphthalate film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a polyethylene-2,6-naphthalate film for magnetic recording tape, and more specifically, it enables long-time recording, has little output fluctuation, and has a low skew. The present invention relates to a polyethylene-2,6-naphthalate film useful for producing a magnetic recording tape which is improved and has excellent slipperiness and durability.

[Prior Art] Magnetic recording tape has recently been extended in recording time (longer time).
In order to prolong the recording time, it is necessary to reduce the total thickness of the magnetic recording tape and store it in the supply reel longer. However, in order to reduce the total thickness of the tape, it is necessary to reduce the thickness of the base film, but in reality the stiffness of the tape decreases and the edges of the tape are easily scratched during loading and unloading. In some cases, when a high tensile force is applied, the tape is deformed and the recording is distorted.

Therefore, a film as a base of a magnetic recording tape for long-time recording is required to have a high Young's modulus.

In addition, with the recent widespread use of VTRs with built-in cameras, the tape is often exposed to severe temperature conditions such as taking it out of the door or bringing it into the car, and the dimensional stability of the tape does not cause skew distortion. As a result, the demand for dimensional stability of the base film is increasing.

Biaxially oriented polyethylene terephthalate film has been conventionally used as a base film of a magnetic recording tape, and a so-called super tension film having a high Young's modulus in the longitudinal direction is used particularly for long-time recording. However, in the polyethylene terephthalate film, the Young's modulus in the machine direction is at most 850 kg / mm ² , in which case the Young's modulus in the machine direction is at most 450 kg / mm ² . On the other hand, when the Young's modulus in the longitudinal direction is increased, the Young's modulus in the lateral direction is inevitably lowered, so that the tape is easily damaged at the edge portion during running. On the other hand, if an attempt is made to increase the width (lateral) direction Young's modulus in the production of the film, a sufficient vertical direction Young's modulus is not necessarily obtained in this case as well, and the touch with the magnetic head becomes poor, resulting in output fluctuation.

Further, if the Young's modulus in only one direction is increased, the tear strength in that direction decreases, and there is another problem that the tape is cut in the magnetic tape.

Further, the base film having a higher Young's modulus which has been stretched at a higher ratio has a problem that the strain generated during molding remains and the dimensional stability is low. In addition, there is another problem that a high-magnification stretching process lowers the product yield.

In the prior art, a process for removing residual strain such as a relaxation heat treatment or an aging process is indispensable in the base film forming process or the tape processing process, and selection and combination of manufacturing conditions are complicated.

On the other hand, in the field of magnetic recording tapes, the demand for high-density recording and high quality has increased more and more in recent years, and along with this, the base polyester film has a flat surface and is excellent in slipperiness, durability and running resistance. The demand for excellent sharpness is becoming stronger.

Conventionally, a method of adding inorganic particles such as silicon oxide and calcium carbonate to polyester as a method of improving slipperiness, or a method of precipitating fine particles containing calcium, lithium or phosphorus in the polymer during the synthesis of polyester has been proposed. There is. In any of these methods, when a polyester film is formed, projections are formed on the film surface due to fine particles to improve the film's slipperiness.

However, in the method of improving the slipperiness of the film by the projections by the fine particles as described above, the slipperiness is usually improved as the film surface is roughened, but on the other hand, the magnetic coating is applied due to the roughening. The resulting surface tends to be rough and the electromagnetic conversion characteristics tend to deteriorate.

As one of the measures for solving these contradictory flatness and slipperiness, there have been proposed a number of means for utilizing composite inorganic particles in which large-sized particles and small-sized particles coexist. However, these means also have problems, and it is difficult to meet the demands for high-grade grade magnetic recording tapes such as high density and high quality. The reason for this is that the size of the large-sized particles used for the composite inorganic particles is coarser than the quality required for high-grade grading, and the larger the particles, the higher the protrusions on the film surface and the particle size. The voids become larger, and the high protrusions are scraped off in the calendering process, causing the cause of dropout.In addition, it is difficult to control the distribution of the added particles and it is difficult to adjust the protrusions on the film surface as designed. is there.

The present inventor has solved the above-mentioned problems, and recorded for a long time,
We have succeeded in developing a film that has flatness, slipperiness and durability that can be applied to the production of high quality magnetic recording tape.

[Object of the Invention] An object of the present invention is to solve the above-mentioned drawbacks, to enable magnetic recording to be performed for a long time, to reduce output fluctuation and to improve skew, and to provide magnetic recording excellent in slipperiness and durability. An object of the present invention is to provide a polyethylene-2,6-naphthalate film for tape. Another object of the present invention is (1) there is no large protrusion on the surface of the film, and there is a minute protrusion that is flat but does not cause noise such as dropout, and friction during running. The biaxially oriented polyethylene-2 has a small coefficient, and further, (2) the base film has very little abrasion in the magnetic recording tape due to this processing step and contact with the magnetic recording / reproducing device, and has good durability in continuous use. To provide a 6,6-naphthalate film.

[Structure and Effect of the Invention] The inventors of the present invention have conducted extensive studies to achieve the above object, and as a result, as a base film of a magnetic recording tape, a biaxially oriented polyethylene-2,6-naphthalate film was used.
The Young's modulus and the heat shrinkage rate are adjusted, and the above properties are simultaneously satisfied by adjusting the surface of the film to a specific roughness, preferably by incorporating specific fine particles in the film to adjust the surface to a specific surface state. It has been found that this can be done.

That is, the present invention has a longitudinal Young's modulus (EM) of 650.
In kg / mm ² or more, lateral Young's modulus (ET) is and the difference between both is 650 kg / mm ² or more | EM-ET | is at 200 kg / mm ² or less, 7
Thermal shrinkage in the machine direction is 0.15% or less when left unloaded for 1 hour at 0 ℃, and surface roughness Ra is 0.01μm
The polyethylene-2,6-naphthalate film for magnetic recording tape is characterized by having a thickness of 0.05 μm or more.

The polyethylene-2,6-naphthalate referred to in the present invention may be any one whose repeating structural unit is substantially composed of ethylene-2,6-naphthalenedicarboxylate units, and polyethylene-2 which is not copolymerized. , 6-
Not only naphthalene dicarboxylate but also copolymers in which 10% or less, preferably 5% or less, of the number of repeating structural units are modified with other components, and mixtures and compositions with other polymers are included. .

Polyethylene-2,6-naphthalate is naphthalene-2,6
-Dicarboxylic acid or a functional derivative thereof and ethylene glycol or a functional derivative thereof are synthesized by binding them under suitable reaction conditions in the presence of a catalyst. May be a copolymerized or mixed polyester prepared by adding one or more suitable third components (modifying agents) before the completion of the polymerization of the polyethylene-2,6-naphthalate. Suitable third component is a compound having a divalent ester-forming functional group, such as oxalic acid, adipic acid, phthalic acid, isophthalic acid, terephthalic acid, naphthalene-2,7-dicarboxylic acid, succinic acid, diphenyl ether dicarboxylic acid. Dicarboxylic acids such as oxycarboxylic acids such as lower alkyl esters thereof, P-oxybenzoic acid, P-oxyethoxybenzoic acid or lower alkyl esters thereof, dihydric alcohols such as propylene glycol and trimethylene glycol, etc. Compounds. Polyethylene-2,6-naphthalate or a modified polymer thereof is obtained by blocking the terminal hydroxyl group and / or carboxyl group with a monofunctional compound such as benzoic acid, benzoylbenzoic acid, benzyloxybenzoic acid or methoxypolyalkylene glycol. Or a compound modified with a trifunctional or tetrafunctional ester-forming compound such as glycerin or pentaerythritol in an extremely small amount within a range where a substantially linear copolymer can be obtained.

The polyester is known per se and can be produced by a method known per se.

As the above polyester, phenol 60%, 1,1,2,2
It is preferable that the intrinsic viscosity of the mixed solution of 40% of tetrachloroethane is about 0.4 to about 0.9 measured at 35 ° C.

Polyethylene-2,6-naphthalate film of the present invention is the longitudinal direction of the Young's modulus is 650 kg / mm ² or more, preferably 680 kg / mm ² or more, more preferably 720 kg / mm ² or more, the lateral Young's modulus 650kg / mm ² or more, preferably 680
kg / mm ² or more, more preferably 720 kg / mm ² or more. However, if the Young's modulus is too high in only one direction, the tear strength in that direction will decrease, and for applications such as magnetic tape, there is concern that the tape may be cut, and it is preferable that the Young's modulus is high in only one direction. Absent. Therefore, the difference between the longitudinal Young's modulus (EM) and the lateral Young's modulus (ET) is 20.
It is 0 kg / mm ² or less, preferably 150 kg / mm ² or less, and more preferably 100 kg / mm ² or less. When the magnetic tape is used, if the Young's modulus is particularly high only in one direction (longitudinal direction), the balance of the stiffness cannot be obtained, and the head touch becomes poor as a tape, resulting in a high-quality tape with high electromagnetic conversion characteristics. I can't get it. The Young's modulus in the lateral direction is preferably 1000 kg / mm ² or less.

If the Young's modulus is 650 kg / mm ² or less in both the vertical and horizontal directions, the base film thickness of 10 μm or less does not provide sufficient stability when processed into a tape, making it difficult to make a thin tape for a long time. Becomes When the tape becomes thin, edge damage occurs in which the end surface of the tape is damaged during use (running). If the Young's modulus in the lateral direction is increased to 1000 kg / mm ² or more, the film becomes extremely laterally oriented and the tear strength of the tape is lowered, which is not preferable.

The polyethylene-2,6-naphthalate film of the present invention has a heat shrinkage ratio of 0.15% or less, preferably 0.10% or less, more preferably 0.06% or less when heat-treated at 70 ° C. for 1 hour under no load. When the heat shrinkage ratio is larger than 0.15%, the skew of the magnetic recording tape becomes large, and the distortion may appear on the screen depending on the image receiver, and even valuable recording may be spoiled, which is not preferable.

The polyethylene-2,6-naphthalate film of the present invention has a surface roughness Ra of 0.01 μm or more and 0.05 μm or more.
It is preferably 0.01 μm or more and 0.03 μm or less. If this Ra is less than 0.01 μm, the slipperiness (running property) will be poor,
On the other hand, if it is larger than 0.05 μm, the surface flatness is lowered and the electrode conversion characteristics are deteriorated, which is not preferable.

The polyethylene-2,6-naphthalate film of the present invention has a large number of fine projections on the surface of the film.
According to the present invention, a large number of these fine projections are derived from a large number of spherical fine particles dispersed in the polyester, preferably spherical silica particles, spherical silicone resin particles, spherical crosslinked polystyrene particles, etc. is there.

A polyester containing such spherical fine particles dispersed therein (preferably as a slurry in glycol) is usually used at any reaction time for forming a polyester, for example, during a transesterification reaction or a polycondensation reaction in the case of a transesterification method. It can be produced by adding spherical fine particles into the reaction system at any time, or at any time in the case of the direct polymerization method. Preferably, the spherical fine particles are added to the reaction system at the initial stage of the polycondensation reaction, for example, until the intrinsic viscosity reaches about 0.3.

The spherical fine particles used in the present invention have the following formula f = V / D ³ The volume shape factor (f) defined by is 0.4 to π / 6.

In the above definition, the average maximum particle size of the particles of D should be understood to mean the distance having the maximum length of the distance between any two points where any straight line across the particle intersects the perimeter of the particle.

Particles having a volume shape factor (f) value of π / 6 are true spheres. The use of fine particles having an f value smaller than 0.4 makes it extremely difficult to control various film surface characteristics.

The spherical fine particles have an average particle size of 0.3 to 2.5 μm, preferably 0.4 to 1.0 μm, and more preferably 0.4 to 0.8 μm.

If the average particle size of the spherical fine particles is less than 0.3 μm, sufficient slidability of the film cannot be obtained, which is not preferable. On the other hand, if the average particle size exceeds 2.5 μm, the projections on the surface of the film become high, and sufficient electromagnetic conversion characteristics cannot be obtained, which is not preferable.

The spherical fine particles preferably have a sharp particle size distribution, and the relative standard deviation indicating the steepness of the distribution is 0.3 or less, preferably 0.12 or less.

This relative standard deviation is given by When using spherical fine particles having a relative standard deviation of 0.3 or less, since the particles are truly spherical and the particle size distribution is extremely steep, the distribution of projections formed on the surface of the film is extremely uniform, A polyethylene-2,6-naphthalate film of uniform height and excellent in slipperiness can be obtained.

The amount of spherical fine particles added is 0.005 to 2.0% by weight, preferably 0.01 to 0.6% by weight, and more preferably 0.05 to 0.5% by weight, based on polyethylene-2,6-naphthalate. If the amount added is less than 0.005% by weight, the effect of improving the slipperiness and abrasion resistance becomes insufficient, while if it exceeds 2.0% by weight, the surface flatness is lowered, which is not preferable.

The spherical silica particles used in the present invention are not limited to the production method and the like as long as the above-mentioned conditions are satisfied. For example, spherical silica particles are produced by hydrolyzing ethyl orthosilicate [Si (OC ₂ H ₅ ) ₄ ] into hydrous silica [Si (OH) ₄ ] monodisperse spheres, which are then dehydrated. It can be produced by three-dimensionally growing a silica bond [≡Si-O-Si≡] (Journal of the Science Society of Japan '81, NO.9, P1503).

Si (OC ₂ H ₅ ) ₄ + 4H ₂ O → Si (OH) ₄ + 4C ₂ H ₅ OH ≡Si-OH + HO-Si ≡ → ≡Si-O-Si≡ + H ₂ O Such spherical silica particles have hitherto been used as a lubricant. It is characterized in that the known silica particles are remarkably different from ultrafine soul-like particles having a size of about 10 nm or agglomerates (aggregated particles) having a size of about 0.5 μm.

Further, the spherical silicone resin particles used in the present invention are not limited to the production thereof as long as the above-mentioned conditions are satisfied. Having a composition represented by

R in the above (A) is a hydrocarbon group having 1 to 7 carbon atoms, and for example, an alkyl group having 1 to 7 carbon atoms, a phenyl group or a tolyl group is preferable. The alkyl group having 1 to 7 carbon atoms may be linear or branched, and examples thereof include methyl, ethyl, n-propyl, iso-propyl, n-butyl, i.
Examples thereof include so-butyl, tert-butyl, n-pentyl, n-heptyl and the like.

Among these, methyl and phenyl are preferable as R, and methyl is particularly preferable.

X in the above formula is a number from 1 to 1.2. When x is 1 in the above formula (A), the above formula (A) is represented by the following formula (A) -1 R SiO _1.5 (A) -1 [wherein R is the same as defined above]. . ] Can be represented by

The composition of the above formula (A) -1 has the following structural portion in the three-dimensional polymer chain structure of a silicone resin; It is derived from.

When x is 1.2 in the above formula (A), the above formula (A) is represented by the following formula (A) -2 R _1.2 SiO _1.4 (A) -2 [where R is the same as above]. Is. ] Can be represented by

The composition of the above formula (A) -2 has the structure of the above formula (A) -1.
0.8 mol and the following formula (A) ′ R ₂ SiO ... (A) ′ [where R is the same as defined above]. ] It can be understood that the structure is represented by 0.2 mol.

The above formula (A) ′ represents the following structural portion in the three-dimensional polymer chain of the silicone resin; Derived from

As will be understood from the above description, the composition of the above formula (A) of the present invention consists essentially of, for example, only the structure of the above formula (A) -1, or the structure of the above formula (A) -1. It can be seen that and the structure of the above formula (A) -2 is a structure that coexists in a state in which they are randomly bonded at an appropriate ratio.

The spherical silicon resin fine particles preferably have a value of x between 1 and 1.1 in the above formula (A).

The silicone resin fine particles have, for example, the following formula RSi (OR ′) ₃ Can be produced by hydrolyzing and condensing a trialkoxysilane represented by or a partial hydrolysis-condensation product thereof in the presence of ammonia or an amine such as methylamine, dimethylamine, ethylenediamine or the like with stirring. According to the above-mentioned method using the above-mentioned starting materials, silicone resin fine particles having a composition represented by the above formula (A) -1 can be produced.

In the above method, for example, the following formula R ₂ Si (OR ′) ₂ [wherein R and R ′ are the same as defined above. ] By using the dialkoxysilane represented by the following together with the above trialkoxysilane and following the above method, the silicone resin fine particles having the composition represented by the above formula (A) -2 can be produced.

Further, the spherical crosslinked polystyrene particles used in the present invention,
As long as the above conditions are satisfied, the manufacturing method and the like are not limited.

For example, spherical crosslinked polystyrene particles include styrene derivative monomers such as styrene monomer, methylstyrene monomer, α-methylstyrene monomer and dichlorostyrene monomer, as well as conjugated diene monomer of butadiene, unsaturated nitrile monomer such as acrylonitrile, and methyl styrene monomer. Monomers such as methacrylic acid esters such as methacrylate, functional monomers such as unsaturated carboxylic acids, monomers having hydroxyls such as hydroxyethyl methacrylate, monomers having epoxide groups such as glycidyl methacrylate, unsaturated One or more monomers selected from sulfonic acid and the like, and a polyfunctional vinyl compound such as divinylbenzene or ethylene glycol dimeta as a cross-linking agent for forming polymer particles into a three-dimensional structure. Relate, trimethylolpropane triacrylate, and diallyl phthalate,
An emulsion of polymer particles is prepared by emulsion polymerization in an aqueous medium in which a water-soluble polymer is dissolved as a protective colloid,
It is obtained by recovering polymer particles from this emulsion, drying them, and then crushing them with a jet mill and then classifying them.

The spherical crosslinked polystyrene particles in the present invention do not dissolve or melt during the polymerization of the aromatic polyester,
Moreover, it does not melt when the polymer is melted during film formation.

Spherical fine particles used in the present invention, preferably spherical silica particles, spherical silicone resin particles, spherical cross-linked polystyrene particles, etc., are spherical and the particle size distribution is extremely steep, so that the height of the film surface protrusions becomes extremely uniform. Furthermore, the individual projections on the film surface have very small projection spheres because the voids around the fine particles are small, so even if the number of projections is the same, the slipperiness is extremely good. Play. These can be used alone or in combination of two or more kinds, and can also be used in combination with other inert solid fine particles or internally precipitated particles.

Inert solid fine particles that can be used in combination with the above-mentioned spherical fine particles are preferably, in the present invention, conventional silicon dioxide; alumina; silicates containing 30% by weight or more of SiO ₂ content (for example, non-modified). Or crystalline clay minerals, aluminosilicates (including fired products and hydrates), hot asbestos, zircon, fly ash, etc .; Mg, Z
Oxides of n, Zr and Ti; Sulfates of Ca and Ba; Phosphates of Li, Ba and Ca (including monohydrogen salts and dihydrogen salts); Li, N
a and K benzoates; Ca, Ba, Zn and Mn terephthalates; Mg, Ca, Ba, Zn, Cd, Pb, Sr, Mn, Fe, Co and Ni titanates; Ba and Pb Examples include chromate; carbon (for example, carbon black and graphite); glass (for example, glass powder and glass beads); Ca and Mg carbonates; fluorite; and ZnS. More preferably, silicic acid anhydride, hydrous silicic acid, aluminum oxide, aluminum silicate (including calcined products, hydrates, etc.), 1 lithium phosphate, 3 lithium phosphate, sodium phosphate, calcium phosphate, barium sulfate, titanium oxide, Lithium benzoate, double salts of these compounds (including hydrates), glass powder, clay (including kaolin, bentonite, clay etc.), talc,
Examples are diatomaceous earth and calcium carbonate. Particularly preferred are silicon dioxide and calcium carbonate.

The inert solid particles have an average particle size of 0.01 to 2.5 μm,
Furthermore, 0.05-2.0 μm, especially 0.1-1.5 μm, especially 0.1-
It is preferably 1.0 μm. The amount added is 0.005 to 2.0% by weight, and 0.01 to 1% by weight based on the polyester.
It is preferably 0.01% to 0.5% by weight, especially 0.05 to 0.3% by weight.

Further, the internally precipitated particles that can be used in combination with the spherical fine particles are produced and precipitated from a catalyst residue or the like during the production of polyester, and are contained in the polymer, and it is conventionally known that they are dispersed and contained. The method of forming internally precipitated particles can be used. For example, JP
-61556, JP-A-51-112860, JP-A-51-1
15803, JP-A-53-41355, JP-A-54-9039
The method disclosed in Japanese Patent Publication No. 7 can be used. The internally precipitated particles are preferably formed between the stage at which the monomer formation reaction is substantially completed and the initial stage of the polycondensation reaction. The catalyst used in the monomer formation reaction and the compound added in this reaction step include calcium compounds,
Preferable examples are lithium compounds and the like. Further, examples of components that form the calcium compound and the lithium compound include aliphatic carboxylic acids such as acetic acid, propionic acid and butyric acid; aromatic carboxylic acids such as benzoic acid, p-methylbenzoic acid and naphthoic acid; methyl. Examples thereof include alcohols such as alcohol, ethyl alcohol, propyl alcohol and butyl alcohol; glycols such as ethylene glycol and propylene glycol; chlorine, hydrogen and the like.

The formation of internally deposited particles is usually carried out by adding a phosphorus compound to the system in which the above compound is present. Examples of phosphorus compounds include phosphoric acid, phosphorous acid, and their esters (for example, alkyl esters, aryl esters, etc.). Further, other additives (for example, lithium phosphate) can be used for the generation, particle size, stabilization and the like of the internally precipitated particles. Among the internally deposited particles, those containing calcium, lithium and phosphorus have a relatively large particle size,
Further, since the particles containing lithium and phosphorus have a relatively small particle size, the composition can be changed according to the desired particle size. As a preferable example of the internally deposited particles, lithium element
Particles containing 0.03 to 5% by weight, calcium element 0.03 to 5% by weight and phosphorus element 0.03 to 10% by weight can be mentioned.

In the present invention, the internally precipitated particles have an average particle size of 0.01 to 2.5.
μm, preferably 0.05 to 2.0 μm, more preferably 0.1 to
The thickness is 1.5 μm, particularly preferably 0.1 to 1.0 μm.
If the average particle size is less than 0.01 μm, the surface irregularities sufficient to satisfy the slipperiness will not appear on the film surface, and the generation of white powder cannot be prevented. On the other hand, if the average particle size exceeds 2.5 μm, the generation of white powder becomes remarkable. Not preferable.

The film of the present invention contains 0.005 to 2.0% by weight of internally deposited particles.
(Relative to the aromatic polyester). When the amount of the particles is less than 0.005% by weight, the slipperiness is not sufficiently imparted, while when it exceeds 2.0% by weight, the surface flatness of the film is deteriorated, which is not preferable.

The amount of the particles is 0.01 to 1% by weight (based on the aromatic polyester), further 0.01 to 0.5% by weight (same), and particularly 0.05.
~ 0.3 wt% (the same) is preferred.

The internally precipitated particles in the present invention can be separated from the polymer, for example, by the method described below, and the particle size, amount, etc. can be determined.

[Particle Separation Method] Polyester or polyester film is thoroughly washed with methanol to remove surface deposits, washed with water and dried. 500 g of the film was sampled, 4.5 kg of o-chlorophenol was added thereto, the temperature was raised to 100 ° C. with stirring, and after the temperature was raised, the polyester portion was dissolved by leaving it for 1 hour. However, if the polyester part does not dissolve, such as when it is highly crystallized, melt it once and quench it, then perform the dissolving operation in the previous term.

Then, in order to remove coarse impurities other than internal particles such as dust contained in the polyester or added reinforcing agent, the pre-dissolved solution is separated with a C-1 glass filter, and this weight is subtracted from the sample weight.

The separation is completed after about 40 minutes, but if necessary, this confirmation is carried out when the light transmittance at 375 mμ of the liquid after the separation becomes a constant value higher than that before the separation. After separation, the supernatant is removed by a gradient method to obtain separated particles.

Since polyester particles may be mixed in the separated particles due to insufficient separation, o-chlorophenol at room temperature is added to the collected particles, and the particles are almost uniformly suspended, and again subjected to ultracentrifugation. This operation needs to be repeated until the particles described later are dried and then subjected to scanning differential calorimetry to detect a melting peak corresponding to the polymer. Finally, the separated particles thus obtained are treated at 120 ° C.,
Vacuum dry for 16 hours and weigh.

The separated particles obtained by the above operation include both internally precipitated particles and spherical silica particles. Therefore, it is necessary to separately determine the amount of internal particles and the amount of spherical silica particles. First, the separated particles are quantitatively analyzed for the metal content to determine the Ca and Li contents and the metal contents other than Ca and Li. Next, the separated particles are heated under reflux in a three-fold molar amount of ethylene glycol for 6 hours or more, and then ethylene glycol is distilled off to 200 ° C. or more to depolymerize, whereby only the internal particles are dissolved. The separated particles obtained by centrifuging the remaining particles are dried and weighed to obtain the external particle amount, and the difference from the initial total separated particle amount is taken as the internal precipitation amount.

The internally precipitated particles may contain a trace amount of other metal components, such as zinc, manganese, magnesium, cobalt, or antimony, germanium, titanium, etc., as long as the effect of the present invention is not impaired.

In the production of the biaxially oriented film of the present invention, spherical fine particles, or this and other inert solid fine particles or internally precipitated particles, in a polymerization kettle before or during the polymerization of polyethylene-2,6-naphthalate. When pelletizing after the completion of the polymerization, the polyethylene-2,6-naphthalate may be sufficiently kneaded in the extruder or in the extruder when the sheet is melt-extruded.

The polyethylene-2,6-naphthalate film of the present invention has a fixed viscosity of 0.35 to 0.9 dl / g obtained by melt-extruding polyethylene-2,6-naphthalate at a temperature of, for example, a melting point (Tm: ° C) to (Tm + 70) ° C. A stretched film is obtained, and the unstretched film is uniaxially (longitudinal or transverse) (Tg-10) to
Stretching at a temperature of (Tg + 70) ° C. (Tg: glass transition temperature of polyethylene-2,6-naphthalate) at a draw ratio of 2.5 to 5.0, and then in the direction perpendicular to the stretching direction (when the first stage stretching is in the longitudinal direction). The second stage drawing is in the transverse direction)
It can be manufactured by stretching at a temperature of (° C.) to (Tg + 70) ° C. at a magnification of 2.5 to 5.0 times. In this case, the area stretching ratio is 9 to
It is preferably 22 times, more preferably 12 to 22 times. The stretching means may be simultaneous biaxial stretching or sequential biaxial stretching.

Furthermore, the biaxially oriented film is (Tg + 70) ° C to Tm (° C)
Can be heat-set at a temperature of, preferably 190 to 240 ° C. The heat setting time is, for example, 1 to 60 seconds.

When the mechanical properties are to be increased, the heat setting temperature of these biaxially stretched films should be (Tg + 20) ° C to (Tg + 7).
0) ℃ and heat set, then 10 ~ 40
Stretching vertically or horizontally at a temperature higher than 0 ° C, and then further stretching horizontally or vertically at a temperature 20 to 50 ° C higher than this temperature. 5.0
It can be obtained by setting ˜6.9 times.

The stretching method may be sequential biaxial stretching or simultaneous biaxial stretching. The number of times of stretching in the machine direction and the transverse direction is not limited to this, but can be obtained by stretching several times in the machine direction and the transverse direction, and is not limited to the number of times.

In either method, finally, the biaxially oriented film is preferably heat set at a temperature of (Tg + 70) ° C. to Tm ° C., preferably 190 to 240 ° C., and the heat setting time is, for example, 1 to 60 seconds.

Furthermore, the heat shrinkage of the base film when heat-treated at 70 ° C for 1 hour under no load is 0.15% or less, preferably 0.10%
Or less, more preferably 0.06 or less. This heat shrinkage rate
When it is more than 0.15%, the skew of the magnetic tape becomes large, the distortion appears on the screen depending on the receiver, and even valuable recording may be spoiled, which is not preferable.

In order to reduce the heat shrinkage rate of the high Young's modulus film in this way, the film after heat treatment is heated under low tension,
This can be done by relaxing in the longitudinal direction. As a method of relaxing in the longitudinal direction, for example, a method of relaxing in a non-contact state under heating and low tension by a floating treatment method by aerodynamic force; a method of relaxing by giving a speed difference between a heating roll and a cooling roll each having a nip roll. Alternatively, there is a method of loosening in the vertical direction by gradually slowing down the moving speed of the clip holding the film in the tenter, but any method can be used as long as it can loosen in the vertical direction.

The thickness of the polyethylene-2,6-naphthalate film is preferably 1 to 15 μm.

The polyethylene-2,6-naphthalate film of the present invention has a small coefficient of friction during running and has very good operability. When this film is used as the base of a magnetic tape, the base film is scarcely scraped off due to contact friction with the running portion of the magnetic recording / reproducing apparatus (hardware), and the durability is good and high electromagnetic conversion is obtained.

Further, the biaxially oriented polyethylene-2,6-naphthalate film of the present invention has a good winding property during film formation, is less likely to cause wrinkles, and is dimensionally stable and sharply cut in the slit stage. It has the advantage of being

Due to the combination of the above advantages as a film product and the advantages at the time of film formation, the film of the present invention is extremely useful particularly as a base film of a high-grade magnetic tape, and the product is easily and stably produced. With the advantage that you can.

The polyethylene-2,6-naphthalate film of the present invention is a high-grade magnetic recording tape, for example, an ultrathin film for long-time recording of audio and video, a high-density recording magnetic tape, and a magnetic recording tape for high-quality image recording / reproducing. For example, it is suitable as a base film for metal or vapor-deposited magnetic recording tape.

Therefore, according to the present invention, a magnetic recording medium provided with a magnetic layer on one side or both sides of the biaxially oriented polyester film of the present invention is also provided.

The magnetic layer and the method of providing the magnetic layer on the base film are known per se, and the present invention can employ a known magnetic layer and a method of providing the same.

For example, when a magnetic layer is provided by a method of coating a base film with a magnetic coating, the ferromagnetic powder used for the magnetic layer contains γ-Fe ₂ O ₃ , Co-containing γ-Fe ₃ O ₄ , Co-containing. Known ferromagnetic materials such as Fe ₃ O ₄ , CrO ₂ and barium ferrite can be used.

The binder used together with the magnetic powder is a known thermoplastic resin, thermosetting resin, reactive resin, or a mixture thereof. Examples of these resins include vinyl chloride-vinyl acetate copolymers and polyurethane elastomers.

The magnetic coating material further includes an abrasive (eg α-Al ₂ O ₃ etc.), a conductive agent (eg carbon black etc.), a dispersant (eg lecithin etc.), a lubricant (eg n-butyl stearate,
Lecithin acid, etc.), a curing agent (eg epoxy resin etc.) and a solvent (eg methyl ethyl ketone, methyl isobutyl ketone, toluene etc.) and the like.

[Effect of the Invention] The polyethylene-2,6-naphthalate film of the present invention is 1
Although the thickness is as thin as 5 μm or less, the running property and durability of the tape are good, the output fluctuation is small, and the skew distortion is also improved. As a result, even in the long-time recording cassette of the home VTR, the thickness of the magnetic recording tarp can be reduced and long-time recording can be performed.

[Examples] The present invention will be further described with reference to Examples.

The measurement methods and definitions of various physical property values and characteristics in the present invention are as follows.

(1) Young's modulus The film is cut into a sample with a width of 10 mm and a length of 15 cm.
The tensile strength was set to 00 mm and the tensile speed was 10 mm / min and the chart speed was 500 mm / min. The Young's modulus was calculated from the tangent line of the rising portion of the obtained load-elongation curve.

(2) Heat shrinkage rate First, measure the length of the sample, and then heat-treat the sample by leaving it in an air thermostat held at 70 ° C for 1 hour in a tension-free state for a heat treatment, and then measuring the length after cooling. Is measured at room temperature. Then, the heat shrinkage is determined from each length before and after the heat treatment.

(3) Skew characteristics As for the skew characteristics, a video tape recorded at room temperature (20 ° C) and normal humidity is heat-treated at 70 ° C for 1 hour and then reproduced again at normal temperature and normal humidity to read the amount of deviation at the head switching point.

(4) Area-equivalent diameter of spherical fine particles, average particle diameter, etc. (4-1) Area-equivalent system of spherical fine particles, measurement of average particle diameter, etc. have the following states.

1) When obtaining from fine powder.

2) When obtaining from the fine particles in the film.

1) From fine powder: Scatter fine powder on the electron microscope sample stand so that individual particles do not overlap as much as possible, and form a gold thin film vapor deposition layer on this surface with a thickness of 200 to 300 Å using a gold sputtering device, and scan. With a scanning electron microscope at 10000 to 30000 times and at least 100 with a Luzex 500 manufactured by Nippon Regulator Co., Ltd.
Obtain the area equivalent circle diameter (Di) of each particle. Then, the average particle size () is represented by the number average value represented by the following equation.

2) From fine particles in the film: A small piece of the sample film is fixed on a sample stand for a scanning electron microscope, and a sputtering device manufactured by JEOL Ltd. (JFC-110) is used.
The film surface is subjected to ion etching under the following conditions using a 0-type ion sputtering device). As for the conditions, the sample is set in a bell jar, the degree of vacuum is raised to a vacuum state of about 10 ^-3 Torr, and ion etching is performed for about 10 minutes at a voltage of 0.25 KV and a current of 12.5 mA. Further, gold spatter is applied to the film surface with the same device, and 1000 is taken with a scanning electron microscope.
Observe at 0 to 30,000 times, and find the area equivalent circle diameter (Di) of at least 100 pieces with Luzex 500 manufactured by Nippon Regulator Co., Ltd. Thereafter, the same procedure as 1) above is performed.

(4-2) Other inert particles Average particle size (DP) Shimadzu CP-50 type Centrifugal particle size analyzer (Centrifugal Particle Siz
e Analyser). The particle diameter corresponding to 50 mass% is read from the integrated curve of the particles of each particle diameter calculated based on the obtained centrifugal sedimentation curve and the abundance thereof, and this value is taken as the above average particle diameter (Book Measurement technology ", published by Nikkan Kogyo Shimbun, 1975, pp. 242-247).

(5) Relative Standard Deviation of Particles 1) Relative Standard Deviation of Spherical Fine Particles Calculated based on the following formula using the area equivalent circle diameter (Di) and the average particle diameter () obtained in the above (4-1). .

2) Relative standard deviation of other inert particles The difference particle size distribution is obtained from the integrated curve obtained in the above (4-2), and the relative standard deviation is calculated based on the following definition formula of relative standard deviation.

Here, each particle diameter obtained in the term of Di; (4-2); average particle diameter obtained in the term of (4-2) n; number of divisions when the integrated curve in the term of (4-2) is obtained φi ; Indicates the existence probability (mass percent) of particles of each particle size.

(6) Film surface roughness (Ra) It is a value defined by JIS-B0601 as the center line average roughness (Ra), and in the present invention, a stylus type surface roughness meter (SURFCORDER SE of Kosaka Laboratory Ltd.) -30C). The measurement conditions are as follows.

(A) Stylus tip radius: 2 μm (b) Measuring pressure: 30 mg (c) Cutoff: 0.25 mm (d) Measuring length: 0.5 mm (e) Data compilation method The same sample was repeatedly measured 5 times, and the largest Except for one value, the decimal point of the average value of the remaining 4 data 4
Round the digits to the third decimal place.

(7) Film friction coefficient (μk) A fixed rod made of stainless steel (SUS304) with a width of 1/2 inch cut in an environment of temperature 20 ° C and humidity 60% (equivalent to a surface roughness of 0.1 to 1.0S; Angle θ = (152/180) for outer diameter 5 mm
It is brought into contact with π radians (152 °) and moved (rubbed) at a speed of 200 cm per minute. The exit tension (T ₂ : g) when adjusting the tension and controller so that the entrance tension T ₁ is 35g is detected by the exit tension detector after the film has run 90m, and the running wear coefficient μk is calculated by the following formula. To calculate.

μk = (2.303 / θ) log (T 2 / T 1) = 0.868 log (T 2/35) (8) scraping of the running surface of the abrasion resistance of the film is evaluated using a 5-stage mini-super calendar. The calender is a five-stage calender consisting of a nylon roll and a steel roll. The processing temperature is 80 ° C, the linear pressure applied to the film is 200 kg / cm, and the film speed is 50 m / min. Running film length 2000
Scratchability of the base film is evaluated by the dirt that adheres to the top roller of the calendar when it is run.

<Four-level judgment> ◎ Nylon roll is not soiled at all ○ Nylon roll is barely soiled × Nylon roll is soiled × × Nylon roll is heavily soiled (9) Frequency of scratches on tape Use a commercially available VHS type VTR tape Set 1
Run for minutes. After that, the running was stopped, the tape was taken out, and the running part, loading, and unloading were performed.
Repeat times. The used portion was visually inspected to check whether the tape surface had scratches.

30 tapes were tested in the same manner. As a result, scratches occurred in 5 or more volumes × scratches occurred in 3 to 4 volumes △ △ scratches occurred in 2 or less volumes

(10) Electromagnetic conversion characteristics (chroma S / N) Using a commercially available VTR for home use, 50% white level signal (100% white level signal is peak: two: peak voltage is 0.714 volt), 100% chroma A signal on which a level signal is superimposed is recorded, and the reproduced signal is recorded as a Shibasoku Noise Meter Type.
Measure with 925R. The definition of chroma S / N is as follows according to the definition of Shibasoku.

Here, ES (p-p) is the peak-to-peak voltage difference (p-p) of the reproduction signal of the white level signal.

ES (p-p) = 0.714V (p-p) EN (rms) is the square root value of the peak voltage of the reproduction signal of the chroma level signal.

EN (rms) = AM noise effective value voltage (V) (11) Dropout Commercially available dropout counter (eg Shibasoku VH
The O1BZ type) was used to count dropouts of 5 μsec × 10 dB and calculate the number of counts per minute.

(12) Skew For skew characteristics, a videotape recorded at room temperature (20 ° C) and normal humidity is heat-treated at 70 ° C for 1 hour and then replayed at normal temperature and normal humidity to read the amount of deviation at the head switching point.

Example 1 A polyethylene-2,6-naphthalate (homopolymer) pellet having an intrinsic viscosity of 0.62 containing 0.3% by weight of spherical silica fine particles having an average particle diameter of 0.5 μm was dried at 170 ° C. for 4 hours.

This polyethylene-2,6-naphthalate was melt-extruded by a usual method to obtain an unstretched film having a thickness of 255 μm.
This unstretched film was sequentially biaxially stretched in the longitudinal direction at 120 ° C for 4.8 times, then in the transverse direction at 135 ° C for 4.6 times, and further 200 times.
It was stretched horizontally by 15% while heat-setting at ℃. Then, the heat-fixed biaxially oriented polyethylene-2,6-naphthalate film was heated to 120 ° C. with a heating roll and the tension was adjusted between the cooling roll and the cooling roll to reduce the heat shrinkage ratio in the longitudinal direction to about 0.
Adjusted to 06%. The film thickness obtained is 10 μm.

Further, on this film, iron oxide powder having the following composition Co 100 parts by weight S-REC A (vinyl chloride-vinyl acetate copolymer manufactured by Sekisui Chemical Co., Ltd.) 10 parts by weight Nipporan 2304 (polyurethane elastomer made by Nippon Polyurethane) 10 parts by weight Coronate L ( Nippon Polyurethane Polyisocyanate) 5 parts by weight Lecithin 1 part by weight Methyl ethyl ketone 75 parts by weight Methyl isobutyl ketone 75 parts by weight Toluene 75 parts by weight Magnetic powder coating with 0.15 parts by weight of additives (lubricant, silicone resin) is applied by gravure roll. The magnetic coating layer was smoothed with a doctor knife, magnetically oriented by a conventional method while the magnetic coating was still dry, and then the magnetic coating layer was guided to an oven and dried and cured. Further, calendering was performed to make the coated surface uniform, and slitting was performed to prepare a 1/2 inch wide magnetic tape on which a magnetic layer having a thickness of about 4 μm was formed. The characteristics of this magnetic tape are shown in Table 1.

In this case, although the tape thickness was relatively thin as 14 μm, there were few scratches on the tape and the effect on the screen was small, and a good tape was obtained.

Example 2 Pellets containing spherical silica particles were prepared according to Example 1.
It was dried at 170 ° C. for 4 hours.

This polyethylene-2,6-naphthalate was melt-extruded by a usual method to obtain an unstretched film having a thickness of 265 μm. This unstretched film was stretched 2.3 times in the longitudinal direction at 120 ° C. and then 3.7 times in the transverse direction at 135 ° C., and then heat-set at the first stage at 160 ° C. as it was. The film was heated to 180 ° C. by passing it through several heating rolls and further stretched 2.6 times in the machine direction. Then, this film is fed into a tenter oven and gradually cooled to 1.6 to 1.6 in an atmosphere of 190 to 200 ° C.
The film was stretched twice and heat-treated at 20 ° C. as it was.

Subsequent processing was performed in exactly the same manner as in Example 1 and tape thickness
14 μm was obtained. The tape characteristics were good, and there was no damage to the tape, and good electromagnetic conversion characteristics were obtained. Also, the skew characteristic was 3 μsec, which was extremely good.

Examples 3 to 4 The same procedure as in Example 1 was carried out, but the additive fine powder was added in Example 3 with silicone resin particles. In Example 4, crosslinked polystyrene particles were added to obtain a film according to Example 1.

Comparative Examples 1 to 2 It was carried out according to Example 1. At this time, the particle size as added particles
It is the one in which 0.2 wt% of 0.6 μm calcium carbonate particles is added and the one in which 0.25 wt% of kaolin particles having an average particle size of 0.6 μm is added.

This film was formed into a tape according to Example 1, but the tape characteristics had problems in running property and scraping property, and satisfactory electromagnetic conversion characteristics could not be obtained.

Comparative Example 3 To 85 parts by weight of ethylene glycol (hereinafter abbreviated as EG), 15 parts by weight of spherical silica fine particles (average particle size 0.5 μm) having a weight loss rate at 500 ° C. of 1.0% by weight were added, followed by mixing and stirring to obtain a slurry. Got The fine content of the slurry by the filter was 800 ppm.

Next, 100 parts by weight of dimethyl terephthalate and 70 parts by weight of EG were transesterified with 0.035 parts by weight of manganese acetate tetrahydrate as a catalyst in a conventional manner, and then the calcium carbonate obtained above (concentration: 0.3% by weight to polymer) Was added with stirring. Subsequently, 0.03 part by weight of trimethyl phosphate and 0.03 part by weight of antimony trioxide were added, and then polycondensation reaction was carried out under a high temperature vacuum in a usual manner to obtain polyethylene terephthalate pellets having an intrinsic viscosity of 0.620. Furthermore, the obtained polyethylene terephthalate (hereinafter abbreviated as PET) pellets were dried at 170 ° C for 3 hours, then fed to an extruder hopper and melted at a melting temperature of 280 to 300 ° C. The molten polymer was surface-finished through a slit die of 1 mm. Molded and extruded on a rotary cooling drum having a surface temperature of 20 ° C. of about S to obtain a 260 μm unstretched film.

The unstretched film obtained in this way is preheated at 75 ° C and then heated by a single IR heater with a surface temperature of 900 ° C from 15 mm above between low speed and high speed rolls to obtain low and high roll surface speeds. Was stretched 1.8 times, quenched, further supplied to a stenter, and stretched 3.5 times in the transverse direction at 120 ° C. The obtained biaxially stretched film was heat-set at a temperature of 100 ° C. for 5 seconds, and the biaxially stretched heat-set film was reheated to 90 ° C. (the speed difference between the heating roll and the cooling roll) in the longitudinal direction. 2.
The film was stretched 8 times, and the resulting film was further stretched 1.5 times in the transverse direction at 150 to 180 ° C., and heat fixed at 220 ° C. again.

The obtained biaxially oriented polyethylene terephthalate film was subjected to a longitudinal relaxation treatment under the conditions of a temperature of 120 ° C and a tension of 30 kg / cm ₂ (film cross-sectional area). The thickness of the obtained film is
It was 10 μm. This film was coated with a magnetic substance according to Example 1.

Comparative Example 4 The film after heat-setting at the first stage at 160 ° C. in Example 2 was passed through several heating rolls, stretched 3 times in the longitudinal direction, and then heat-setting at the second stage was performed at 220 ° C. A 10 μm film was obtained. Further 120 ℃, 30kg / cm ₂ (film section)
It was relaxed vertically.

A magnetic substance was applied to this film to obtain a 14 μm tape.

Example 5 In Example 1, 0.2 wt% of spherical silica having a particle size of 0.5 μm and 0.3 wt% of titanium oxide having a particle size of 0.3 μm were added to the additive particles, and a tape of 14 μm was obtained in the same manner as in Example 1.
The results are shown below.

Example 6 In Example 1, the average particle size was 0.6 μ for surface formation.
m spherical silicone resin particles were added, and the surface was formed by mixed particles with internally precipitated particles generated from the inside of the polymer to obtain a film of 10 μm. Others are Example 1
Is the same as

Example 7 0.1 wt% of silicone resin particles having an average particle size of 0.6 μm and 0.3 wt% of titanium oxide particles having an average particle size of 0.3 μm in Example 2
%, A tape was similarly obtained, and as a result of evaluation, a tape having relatively good scraping property and good electromagnetic conversion characteristics was obtained.

Comparative Examples 5 to 6 In Comparative Example 4, the added particles were replaced by spherical silica instead of silicone resin having an average particle size of about 0.5 μm and crosslinked polystyrene particles.

If the Young's modulus increases in one direction, the abrasion resistance of the film tends to deteriorate, the tape characteristics deteriorate, the electromagnetic conversion characteristics do not rise, and the tape damage becomes large, which is not preferable.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location C08L 67:00 C08L 67:00 (72) Inventor Hideo Kato 3-37-19 Oyama, Sagamihara City, Kanagawa Prefecture Issue: Teijin Ltd. Plastics Research Laboratory (56) Reference JP 62-136013 (JP, A) JP 62-135339 (JP, A) JP 63-289029 (JP, A)

Claims (6)

(57) [Claims] 1. A Young's modulus in the longitudinal direction (EM) is 650 kg / mm ² or more, a Young's modulus in the transverse direction (ET) is 650 kg / mm ² or more, and the difference | EM-ET | of both is 200 kg / mm ² The heat shrinkage ratio in the longitudinal direction is 0.15 when left unloaded at 70 ° C for 1 hour.
% Or less, and the surface roughness Ra is 0.01 μm or more and 0.05 μm or more.
A polyethylene-2,6-naphthalate film for magnetic recording tape, characterized by having a thickness of m or less. 2. The Young's modulus in the longitudinal direction (EM) is 680 kg / mm ² or more, the Young's modulus in the transverse direction (EM) is 680 kg / mm ² or more, and the difference | EM-ET | between them is 100 kg / mm ² A polyethylene-2,6-naphthalate film for a magnetic recording tape according to claim 1. 3. The polyethylene-2,6-naphthalate film for magnetic recording tape according to claim 1, which has a thermal shrinkage of 0.10% or less when left at 70 ° C. for 1 hour without load. 4. Fine particles having a volume shape factor of 0.4 to π / 6 and a relative standard deviation of the particles defined below of 0.3 or less, and having an average particle size () of 0.3 to 2.5 μm. To
A polyethylene-2,6-naphthalate film for magnetic recording tape, characterized by containing 0.005-2.0 wt%. Here, Di: area circle equivalent diameter of individual particles (μm) n: represents the number of particles. 5. The polyethylene for magnetic recording tape according to claim 1, wherein the fine particles are one or more selected from the group consisting of silica, silicone resin particles and crosslinked polystyrene particles.
2,6-naphthalate film. 6. The polyethylene-2,6 for magnetic recording tape according to claim 1 or 5, which contains other inert particles and / or internally precipitated particles as other components simultaneously with the fine particles.
-Naphthalate film.