JPH0229437A - Biaxially oriented polyester film - Google Patents

Abstract

PURPOSE:To improve running durability and chipping resistance in repeated use, by dispersing a specific magnetic powder in a polyester, molding the dispersion into film and biaxially orienting the film. CONSTITUTION:In a polyester with an intrinsic viscosity (in o-chlorophenol, 35 deg.C) of pref.0.4-0.9, prepd. from an acid component comprising mainly an arom. dicarboxylic acid and a glycol component comprising mainly an aliph. glycol (e.g., polyethylene terephthalate) is dispersed 0.01-1.0wt.%(based on said polyes ter) magnetic powder with a mean particle diameter of 0.05-2.0 and an aspect ratio (long diameter/short diameter) of 1.1-2.7, pref.1.1-2.0, selected from the group consisting of ferromagnetic iron oxide, ferromagnetic chromium dioxide and ferromagnetic alloy powder. The dispersion is fused and molded into film to give an amorphous nonoriented film, which is then biaxially oriented, heat set and, if necessary, annealed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a biaxially oriented polyester film, and more specifically, the present invention relates to a biaxially oriented polyester film, and more specifically, it contains magnetic powder having a specific average particle size ratio in the polyester, and when used repeatedly. This invention relates to a biaxially oriented polyester film with excellent running durability and abrasion resistance.

[Prior Art] As magnetic recording media based on polyester films, for example, video tapes, audio tapes, computer tapes, floppy disks, etc. are known and widely used.

In recent years, demands for high-density recording and high quality have been increasing in these application fields, and as a result, the polyester film that serves as the base has a flat surface, excellent slipperiness, durable running performance, and durability. There is an increasing demand for excellent breakability.

Conventionally, methods for improving slipperiness have been proposed, including adding inorganic particles such as calcium carbonate to polyester, or precipitating fine particles containing calcium, lithium, or phosphorus within the polymerization system during polyester synthesis. In either method, when polyester is molded and stretched to form a film, projections are formed on the surface of the film due to fine particles, thereby improving the slipperiness of the film.

However, in the above-mentioned method of improving the slipperiness of a film using protrusions made of fine particles, the slipperiness usually improves as the film surface becomes rougher; The subsequent surface tends to become rough and the electromagnetic conversion characteristics deteriorate.

As one of the measures to solve these contradictory problems of flatness and slipperiness, many methods have been proposed, including the use of composite inorganic particles in which large-sized particles and small-sized particles coexist. However, these methods also have problems, and if they are not used as they are, it will not be possible to achieve higher grade magnetic recording media, such as higher density,
The reason why it is difficult to meet the demand for higher quality is that the size of the large particles used for composite inorganic particles is coarser than the quality required for high-grade grades. As the protrusions on the surface become taller, the voids surrounding the particles also become larger, and during the cleaning process with nonwoven fabric or the calendering process, the tall protrusions are scraped off, causing dropouts (missing information that occurs during recording and playback). Furthermore, it causes calender stains during the processing process and dust fabric stains for cleaning the base film surface, which greatly impairs the properties of the magnetic recording medium.

[Object of the Invention] An object of the present invention is to solve the above-mentioned problems and provide a biaxially oriented polyester film that has excellent flatness, easy sliding properties, and abrasion resistance, and furthermore, (1) The coefficient of friction during running is small, and there is very little abrasion of the base film due to the processing of F21 magnetic recording media and contact with parts of magnetic recording and reproducing devices, making it useful for manufacturing magnetic recording media that are not durable due to continuous use. An object of the present invention is to provide a biaxially oriented polyester film.

[Configuration and Effects of the Invention] According to the present invention, an object of the present invention is that the average particle diameter is 0.05.
0.01% by weight or more 1
．． This is achieved with biaxially oriented polyester films containing less than 0% by weight dispersed content.

The polyester in the present invention is a polyester containing an aromatic dicarboxylic acid as a main acid component and an aliphatic glycol as a main glycol component.

Such polyesters are substantially linear and have film forming properties, particularly by melt molding. Examples of aromatic dicarboxylic acids include terephthalic acid,
Naphthalene dicarboxylic acid, isophthalic acid, diphenoxyethane dicarboxylic acid.

Diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid.

Examples include diphenylketone dicarboxylic acid and anthracene dicarboxylic acid. Examples of aliphatic glycols include polymethylene glycols having 2 to 10 carbon atoms such as ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, and decamethylene glycol, or alicyclic glycols such as cyclohexane dimetatool. Diols and the like can be mentioned.

In the present invention, polyesters containing, for example, alkylene terephthalate and/or alkylene naphthalate as main constituents are preferably used.

Among such polyesters, for example, polyethylene terephthalate and polyethylene-2,6-naphthalate, for example, 80 mol% of the total dicarphonic acid component.
A copolymer in which the above is terephthalic acid and/or 26-naphthalene dicarboxylic acid and 80 mol% or more of the total glycol component is ethylene glycol is preferred. In this case, up to 20 mol % of the dicarboxylic acid based on the total acid component can be a P aromatic dicarboxylic acid, and for example, adipic acid,
Aliphatic dicarboxylic acids such as sepatic acid; alicyclic dicarboxylic acids such as cyclohexane-1,4-dicarboxylic acid, and the like. In addition, up to 20 mol% of the total glycol component can be the above-mentioned glycols other than ethylene glycol, or aromatic diols such as hydroquinone, resorcinol, 2.2bis(4-hydroxyphenyl)propane, etc.; Aliphatic diols having an aromatic ring such as 4-dihydroxymethylbenzene; polyalkylene glycols (polyoxyalkylene glycols) such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc. can also be used.

Furthermore, in the polyester used in the present invention, a component derived from an oxycarboxylic acid such as an aromatic oxyacid such as hydroxybenzoic acid; an aliphatic oxyacid such as ω-hydroxycaproic acid, a dicarboxylic acid component and an oxycarboxylic acid component. Those copolymerized or combined in an amount of 20 mol % or less based on the total amount of components are also included.

Furthermore, the polyester in the present invention contains a substantially linear amount of polycarboxylic acid or polyhydroxy compound, such as trimellitic acid, pentamellitic acid, etc., in an amount of 2 mol% or less based on the total acid component. Also included are those copolymerized with erinritol and the like.

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

The above polyester has an intrinsic viscosity of about 0.4 measured as a solution in 0-talolophenol at 35°C.
~0.9 is preferred.

The biaxially stretched polyester film of the present invention has many fine protrusions on its surface.

According to the present invention, these many fine protrusions originate from a large number of magnetic powders dispersed and contained in the polyester.

Polyester containing dispersed magnetic powder can be prepared at any time during the reaction to form polyester, for example, during the transesterification reaction or polycondensation reaction when using the transesterification method, or at any time when using the direct polymerization method. To,
Magnetic powder (preferably as a slurry in glycol)
It can be produced by adding into the reaction system. Preferably, the initial stage of the polycondensation reaction, for example, when the intrinsic viscosity is about 0
It is preferable to add magnetic powder to the reaction system until the temperature reaches 3°.

In the present invention, the magnetic powder dispersed in the polyester has a particle size ratio (major axis/minor axis) of 1.1 to 2.7, preferably 1.1 to 2.5. More preferably, it is 1.1 to 2.0.If the particle size ratio exceeds 2.7, it is difficult to knead the particles well and uniformly into the polymer (polyester), which is not preferable.

This magnetic powder book has an average particle size of 0.05μ to 2.0μ, preferably 0.20 to 0.9μ, and more preferably 0.05μ to 2.0μ.
It is 3 to 0.7μ.

If the average particle size of the magnetic powder is less than 0.05 μm, the effect of improving slipperiness will be insufficient, which is not preferable.

On the other hand, if the average particle size exceeds 2.0 μm, the surface flatness becomes insufficient, which is not preferable.

Here, the major axis and minor axis of the magnetic powder are determined from an image magnified 10,000 to 30,000 times with an electron microscope after depositing metal on the particle surface, and are the average particle diameter.

The particle size ratio is determined by the following formula.

Average particle diameter = Sum of area circle equivalent diameters of magnetic powder / Several particle diameter ratio of measured particles = Average major axis of magnetic powder / Average minor axis of the particles In the present invention, ferromagnetic iron oxide is used as the magnetic powder. , ferromagnetic chromium dioxide, ferromagnetic alloy powder, etc. can be applied. Here, ferromagnetic iron oxides include γ-Fe2O3, magnetite (Fe
304) and mixtures thereof. These ferromagnetic iron oxides contain divalent Cr.

Mn, Co, Ni, Cu, Zn, etc. may be included, and ferromagnetic CrO□ may contain K, which is another component.

Metals such as Na, Ti, V, Mn, Fe, Co, Ni, Te, etc. and semiconductors such as P, Sb, Te, etc. may be included.9 The present invention includes a range in which they are dispersed in polyester and do not alter the quality of the polymer. In this case, known magnetic powder exhibiting ferromagnetism can be applied.

In the present invention, the amount of magnetic powder added is 0.01% by weight or more and less than 1.0% by weight based on the polyester, preferably 0.05 to 0.8% by weight, more preferably 0.0% by weight.
It is 1 to 0.7% by weight. Addition amount of magnetic powder is 0.01
If it is less than 1.0% by weight, the effect of improving lubricity and abrasion resistance is insufficient, and if it is more than 1.0% by weight, surface flatness decreases, which is not preferable.

The polyester film of the present invention can be manufactured in accordance with the conventional manufacturing method of biaxially stretched films. The unstretched film is then biaxially stretched, heat-set, and if necessary subjected to relaxation heat treatment. At this time, since the film surface retention varies depending on the particle size, fi, etc. of the magnetic powder, and also depending on the stretching conditions, it is appropriately selected from conventional stretching conditions. In addition, density, heat shrinkage rate, etc. are also stretched.

The temperature during heat treatment varies depending on the magnification, speed, etc.
0, which defines the conditions that satisfy these characteristics simultaneously,
The stretching temperature is the first stage stretching temperature (e.g. longitudinal stretching temperature: T
1) is in the range of (Tg-10) to (7g+45)'C (where Tg is the glass transition temperature of polyester), the second-stage stretching temperature is ('I'1+15) to (T1+40)'C
In addition, the stretching ratio is preferably selected from a range in which the uniaxial stretching ratio is 2.5 times or more, especially 3 times or more, and the area magnification is 8 times or more, especially 10 times or more. The heat setting temperature is preferably selected from the range of 180 to 250°C, more preferably 200 to 230°C.

The thickness of the film is preferably 1 to 100 microns.

[Example] The present invention will be further explained below with reference to Examples.

Note that various physical property values and characteristics in the present invention were measured as follows.

(1) Particle size of particles There are the following conditions for particle size measurement.

1) When determining the average particle size, particle size ratio, etc. from powder 2) When determining the average particle size, particle size ratio, etc. of particles in a film.

1) From powder: Scatter the powder on an electron microscope sample stage so that the individual particles do not overlap as much as possible, and form a thin gold film vapor deposited layer on the surface using a gold sputtering device to a thickness of 200 to 300 people. Observe with a scanning electron microscope at 10,000 to 30,000 times magnification, and determine the major axis (Dli), minor axis (Dsi), and area equivalent diameter (Di) of at least 100 particles using Luzex 500 manufactured by Nippon Regulator ■. . The major diameter (DI), minor diameter (Ds), and average particle diameter (D> of the particles are expressed by the number average value expressed by the following formula).

n
nD 1 = (Σ Dli)/n, Ds=
(Σ Dsi)/n=1
1 = 1D = (Σ Dt ), /n 1 = 1 2) In the case of particles in a film: A small piece of sample film was fixed on a sample stage for a scanning electron microscope, and sputtered using a sputtering device (JFC-110) manufactured by JEOL ■.
The surface of the film was subjected to ion etching using a 0-type ion sputtering device under the following conditions. The conditions were to place the sample in a Pelger and to apply a pressure of approximately 10”3 Torr.
The degree of vacuum was increased to the vacuum state a', and ion etching was carried out for about 10 minutes at a voltage of 0.25 KV and a current of 1.2511 A. Furthermore, gold sputtering was applied to the film surface using the same equipment, and the film was observed using a scanning electron microscope at a magnification of 10,000 to 30,000 times.
The major axis (Dli), minor axis (Dsi), and area equivalent diameter (Di) of at least 100 particles are determined. below,
Proceed in the same manner as 1) above.

(2) Film surface roughness (Ra) This is the value defined in JIS-80601 as the center line average roughness (Ra), and in the present invention ). The measurement conditions are as follows. .

a Stylus tip radius: 2μm b Measurement pressure = 30■ C cutoff: 0.25m+nd Measurement length:
0.5 Ue How to summarize the data - Repeat the measurement for the sample 5 times and select the largest value as 1
The average value of the remaining four data is rounded off to the fourth decimal place and displayed to the third decimal place.

(3) Film friction coefficient (μk) In an environment with a temperature of 20°C and a humidity of 60%, a film cut to a width of 1/2 inch is held at an angle θ = (152/ 180) π radian (152
When the tension controller is adjusted so that the inlet tension T1 is 35 g, the outlet tension (T
z:g> is detected by an outlet tension detector after the film has traveled 90 m, and the running wear coefficient μk is calculated using the following formula.

μ k = (2,303/θ) IOg
(T2 /Tt)=0.86810(J(Tz
/35) (4) Scrapability The scratchability of the running surface of the base film was evaluated using a 5-stage mini super calendar. The calendar is a 5-stage calender with nylon rolls and steel rolls, the processing temperature is 80'C, and the linear pressure applied to the film is 200 kI.
r/all, film speed was 50 m/min. After running the running film for a total length of 2000 m, the abrasion resistance of the base film was evaluated based on the dirt adhering to the top roller of the calendar.

<Four-level judgment> ◎ No stains on the nylon roll ○ Almost no stains on the nylon roll
Using a TR, record a signal in which a 100% chroma level signal is superimposed on a 50% white level signal (a 100% white level signal has a peak-to-peak voltage of 0.714 volts), and then record the reproduced signal. Shibatsuku Noise Meter Type
The definition of chroma S/H, which is measured using e 952 R, is as follows according to the definition of Sibak.

E S (1)-+3) Chroma S/N (dB) = 2010 (1EN(rn
s) Here, BS(+)-D) is the peak:to:peak voltage degree (p-p) of the reproduced signal of the white level signal.

E S (t]-1])=0.714ν(p-p) Furthermore, EN(rls) is the square root value of the peak voltage of the reproduced signal of the chroma level signal.

EN (rns) = AM noise effective value voltage (V) (6)
Dropout counters available commercially (e.g. Shibatsu VH
5) tS[3CX 10 dB dropout was counted with OIB7 type) and the number of counts per minute was calculated.

(7) Slit the scratch judgment base film into 1/2 inch width and
), the film was placed on the fixed rod at an angle of 125°, and the film speed was 20 cm/sec.
After repeating this process 50 times, judge the thickness, depth, and number of scratches on the surface of the base film in the following five steps.

5-level judgment> ◎ No scratches are observed on the base film ○ Almost no scratches are observed on the base film Δ Scratches are observed on the base film (several scratches) X Several thick scratches are observed on the base film ×X Comparative example 1 where many thick and deep scratches are observed on the entire surface of the base film Dimethyl terephthalate and ethylene glycol, manganese acetate as a transesterification catalyst, antimony trioxide as a polymerization catalyst, subphosphoric acid as a stabilizer, and Polyethylene terephthalate with an intrinsic viscosity (orthochlorophenol, 35° C.) of 0.62 was obtained by polymerization in a conventional manner using carrion having an average particle size of 0.9 μm and a particle size ratio of 10.0 as a lubricant.

This polyethylene terephthalate pellet was heated to 170°C.
, after drying for 3 hours, fed to the extruder hopper, melting temperature 28
The molten polymer is melted at 0-300°C and passed through a 1 mm slit die with a surface finish of 0. BS grade, formed and extruded on a rotating cooling drum with a surface temperature of 20°C, 200μm
An unstretched film was obtained.

The unstretched film thus obtained was preheated at 80°C, and further heated with one IR heater with a surface temperature of 900°C from 15++ m above between low-speed and high-speed rolls.
, stretched 4 times, quenched, then supplied to a stenter and stretched 3.8 times in the transverse direction at 105°C. The resulting biaxially oriented film was subjected to thermal testing at a temperature of 210° C. for 5 seconds to obtain a biaxially oriented polyester film with a thickness of 15 μm.

Although the obtained film showed good results when calendered, it had poor runnability and scratches, and was unsatisfactory. The properties of this film are shown in Table 1.

Further, on this film, 100 parts by weight of Co-containing iron oxide powder with the following composition S-LEC A (manufactured by Sekisui Chemical Co., Ltd.: vinyl chloride-vinyl acetate copolymer) 10+1 Nituboran 2
304 (Japan Polyurethane!!!: polyurethane elastomer) ioll Coronate L (made by Nippon Polyurethane: polyisocyanate) 5 n lecithin 1 Tsunomethyl ethyl ketone 7511 Methyl isobutyl ketone 7511 Toluene
75 Horn additive (lubricant, silicone resin) 0.15 Apply the magnetic powder paint of II using a gravure roll, smooth the magnetic paint layer with a doctor knife, and magnetically orient it by a conventional method while the magnetic paint is still dry. After that, it was introduced into an oven for dry curing, further calendered to make the coated surface uniform, and slit to form a magnetic layer with a thickness of about 5μ.
Created a magnetic tape of 1 inch. The characteristics of this magnetic tape are shown in Table 1.

Comparative Example 2 Instead of kaolin, average particle size 0.65 μm, particle size ratio 1.7
A pellet of polyethylene terephthalate was obtained in the same manner as in Comparative Example 1 except that calcium carbonate was used.

Using this pellet, the thickness was 15 mm in the same manner as in Comparative Example 1.
A micrometer biaxially oriented film was obtained. Although this film had good running properties, white powder was generated during the calendering process.

The properties of this film are shown in Table 1.

Furthermore, a magnetic tape was produced in the same manner as in Comparative Example 1 except that this film was used. The first characteristic of this magnetic tape is
Shown below.

Comparative Example 3 An unstretched film was obtained in the same manner as Comparative Example 2, but in order to further increase the strength in the machine direction, the unstretched film was preheated with a low-speed roll whose surface temperature was controlled at 70°C, and the film was heated between the high-speed roll and the unstretched film. Three IR heaters were installed, and the stretching ratio was 4.2.
The biaxially oriented film was stretched twice, then passed through a stenter, preheated to 108° C., and stretched 3.6 times in the transverse direction.

Furthermore, a magnetic tape was prepared in the same manner as in Comparative Example 1 except for using this film. The characteristics of this magnetic tape are shown in Table 1.

Comparative Example 4 A polyethylene terephthalate biaxially oriented film (thickness 15 μm
Get m). Furthermore, a magnetic tape was produced in the same manner as in Comparative Example 1 except that this film was used.

The properties of the film and magnetic tape are shown in Table 1.

Although this film improved electromagnetic performance due to its flat surface, it had a high coefficient of friction and suffered from calender abrasion, making it unsatisfactory as a magnetic recording medium.

Examples 1 to 3 Polyethylene terephthalate was obtained in the same manner as in Comparative Example 1, except that magnetic powder having the average particle size and particle size ratio shown in Table 1 was used instead of kaolin.

A biaxially oriented polyester film having a thickness of 15 μm was obtained in the same manner as Comparative Example 1 or Comparative Example 4 except for using this slit. The properties of this film are shown in Table 1.

The biaxially oriented films obtained in Examples 1 to 3 all exhibit excellent slipperiness despite having flat surfaces, so magnetic tapes using these films have extremely improved electromagnetic properties, and are not easily calendered. It is also strong, with almost no wear observed.
Therefore, Dlo caused by tape scraping is also reduced, making it an extremely good magnetic recording medium.

Claims (1)

[Claims] Magnetic powder with an average particle size of 0.05μ or more and 2.0μ or less and a particle size ratio (major axis/breadth axis) of 1.1 to 2.7 is
．． A biaxially oriented polyester film containing dispersed content of 0.01% by weight or more and less than 1.0% by weight.