JPS63284231A - Biaxially oriented polyester film - Google Patents

Abstract

PURPOSE:To obtain the title film for magnetic recording media, having a low light transmittance and excelling in running and abrasion performance, by adding carbon black specified in shape, amount of addition, etc., and spherical silica to a polyester, forming the mixture into a film and biaxially stretching this film. CONSTITUTION:0.15-7wt.% carbon black of an average particle diameter of 0.01-0.6mum and 0.005-1wt.% spherical silica of an average particle diameter of 0.1-1.2mum and an aspect ratio as defined by a major diameter to minor diameter ratio of 1-1.4 are added to a polyester (e.g., polyethylene terephthalate). This polyester is melt-molded into an unstretched film, and this film is biaxially stretched to obtain the purpose biaxially oriented polyester film. When this film is used as a base film of a magnetic recording medium, the detection of the trailer of the medium can be performed in good precision without any special treatment because of its low light transmittance.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a biaxially oriented polynisder film, and more particularly, it is used as a magnetic recording medium that has excellent running properties and abrasion resistance as well as low light transmission. The present invention relates to a biaxially oriented polyester film for use.

[Prior art]

Biaxially oriented polyester films, typified by polyethylene tele-7 tallate film, are used in a wide range of applications due to their familiar physical and chemical properties, and are widely used in magnetic recording applications such as video, audio, computers, and 70-inch disks. Widely used as base film for media. In recent years, there has been a remarkable increase in AiWj[+ffi recording in these applications, and in order to improve the electromagnetic conversion characteristics, the powder used in magnetic desolation has become finer. When the magnetic powder becomes fine powder, the yellow light of tlL length becomes less scattered by the magnetic powder and the light transmittance increases. Magnetic recording media that use the difference in the light transmittance of the base film to detect the end of the magnetic recording medium have problems, and there is a need to reduce the light transmittance of the base film.

Many attempts have been made to add carbon black to the base film in order to impart light-shielding properties, but none of them maintain sufficient performance in terms of flatness, runnability, abrasion resistance, etc. required for magnetic recording media. However, it has not yet been industrialized.

Also carbon black and calcium carbonate.

Attempts have been made to improve the above-mentioned properties by adding a two-component bulking agent with titanium oxide, but they are still in progress.

[Purpose of the invention]

An object of the present invention is to provide a biaxially oriented polyester film that can compensate for these drawbacks and has a low light transmittance and has sufficient flatness, runnability, and abrasion resistance for use as a hunting depth.

[Achievements and effects of the invention]

According to the invention, the object of the present invention is to
0.6 am carbon black? :0.15~7
．． Contains 0% by weight and has an average particle size of 0.1 to 1.2 μm
and the particle size ratio defined by major axis/minor axis is 1.0 to 1.
This is achieved by a biaxially oriented polyester film characterized by containing 0.005 to 1.0 heavy electric percent of spherical silica of No. 4.

The polyester in the present invention is a polynisdel having an aromatic dicarboxylic acid as the main acid component and an aliphatic glycol as the main glycol component. Such polyesters are linear in nature and have film forming properties, particularly by melt molding. Examples of aromatic dicarboxylic acids include terephthalic acid, naphthalenedicarboxylic acid, inphthalic acid #diphenylethanedicarboxylic acid,
Examples include diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid, diphenyl ketone dicarboxylic acid, and 7-thracene dicarboxylic acid rR. Examples of fatty glycols include evapoethylene glycol, trimethylene glycol, detramethylene glycol, pentamethylene glycol, and hexamethylene glycol.

Examples include fullylene glycols having carbon vL2 to 10, such as decamethylene glycol, and alicyclic diols, such as cyclohexane dimetatool.

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

Among such polynisdels, for example, not only polyethylene terephthalate and polyethylene-2,6-naphthalate, but also those in which 80 mol% or more of the total dicarboxylic acid components are terephthalic acid and/or 2,6-7thalene dicarboxylic acid. , 80 moles or more of the total glycol component is ethylene glycol! A split is preferred. The dicarboxylic acid may be an aromatic dicarboxylic acid, or an aliphatic dicarboxylic acid such as dipic acid or sepatic acid; or an alicyclic dicarboxylic acid such as cyclohexane-1,4-dicarboxylic acid. In addition, 2 of the total glycol components
Up to 0 mol% can be the above glycols other than ethylene glycol, or aromatic diols such as hydroquinone, resorcinol, 2,2-bis(4-hydroxyphenyl)propane, etc.; 1,4-dihydroxymethylbenzene Aliphatic diols having an aromatic ring such as; polyalkylene glycols (polyoxyalkylene glycols) such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc. can also be used.

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

Furthermore, the polyester in the present invention may contain a trifunctional or higher functional polycarboxylic acid or polyhydroxy compound 1, such as trimellitic acid, in an amount in a substantially linear range, for example, 2 mol% or less based on the total number of components. Copolymerized products such as pesotaerythritol are also included.

The polyesters mentioned above are known per se and can be dressed in a manner known per se.

The above polyester has an intrinsic viscosity of about 0 when measured as a bath solution in -o-chlorophenol at 35°C.
．． 4 to about 0.9 is preferred.

In the present invention, the average particle size of the polyester is 0.
．． 0.1 A-0.6 μm carbon black
5 to 7.0% by weight. When the carbon black content is less than 0.15%, the optical transmittance decreases insufficiently for a film generally used for magnetic recording media. Moreover, the carbon black content is 7. Om
If it exceeds t%, the flatness of the surface of the film deteriorates, leading to deterioration of the electromagnetic conversion characteristics used in magnetic recording media. The content of carbon black necessarily changes depending on the thickness of the film, but it may be set within the above range so that it is 40% or less, preferably 30% or less in terms of light transmission.

In the present invention, the average particle diameter is O91 to 1.2 μ and 1 & diameter /
0.005 to 1.0% of spherical silica particles defined by the short diameter and having a particle diameter ratio of 1.0 to 1.4 are contained. These spherical silica particles have individual shapes very similar to pearls, and may be conventionally known as silica particles known as lubricants, or fine lumpy particles of about 10 μm in size, which are aggregated to form 0.0 μm particles. It is distinctive in that it forms aggregates (agglomerated particles) with a diameter of about 5 μm.

The average particle size of the spherical silica particles is necessarily 0.1-1.2 .mu.m, preferably 0.2-1.0 .mu.m.

If the average particle size is less than 0.1 μm (evening), the effect of improving the runnability and abrasion resistance of the film is insufficient, which is not preferable.

Moreover, if the average particle diameter exceeds 1.2 μm, the surface of the film becomes too rough, which is not preferable.

The particle size ratio of the spherical silica is 1.0 to 1.4, preferably 1.0 to 1.4.
It needs to be 0 to 1.2. This particle size ratio is 1.4
If it exceeds this amount, large voids will occur around the spherical silica in the film after biaxial stretching, and the above-mentioned effects on runnability and N1 stain resistance will decrease. In addition, it is desirable that the average particle size of the spherical silica be equal to or larger than the average particle size of the carbon black added at the same time, and it is preferable that the particle size distribution of the spherical silica be sharp. It is preferable that the relative standard deviation representing the degree of KO is 0.5 or less, more preferably 0.3 or less, and especially KO, 15 or less. This relative standard deviation is expressed by the following formula.

Here, Dl - the surface equivalent diameter of an individual particle (μ) D = surface area circle diameter average value n: Measured number of particles It is.

In addition, the major axis and minor axis of the spherical silica particles are determined from an image magnified, for example, 10,000 to 30,000 times with an electron microscope after depositing gold on the particle surface. The ri diameter ratio can be calculated using the following formula.

Average diameter ηm=sum of area circle equivalent diameters of measured particles/measured particles r! 14 times = average major axis of silica particles/average minor axis of core particles By containing spherical silica particles, H adhesion property is higher than that of a film containing only carbon black.

The wear resistance is improved, but the effect becomes greater by making the average particle size of the spherical silica particles equal to or larger than the average particle size of the carbon black. In addition, when the distribution of spherical silica particles becomes steep, the height of the large protrusions caused by the spherical silica particles on the film surface becomes uniform, and the height of the protrusions caused by carbon black becomes uneven. The improvement effect will be greater.

The R-shaped silica particles are not limited in any way, including their manufacturing method, as long as they satisfy the above-mentioned conditions.

For example, spherical silica particles are made of ethyl orthosilicate (5t(
octL)n) from the decomposition of hydrated silica (81
(Of(in) A monodisperse method is created, and this hydrated silica monodisperse method is further dehydrated to form a silica bond (WEMSt -
It can be produced by three-dimensionally growing 0-8t microorganisms (Journal of the Chemical Society of Japan °81.m9゜P1503).

81(QC,H,), +4)I,O→S i (O
) I), + 4 C,H,01(EMsi -oa+
The biaxially oriented polyester film of the present invention can be produced according to the conventional method for producing biaxially oriented films. for example,
A polyester containing carbon black particles and spherical silicone particles is melt-formed to form an amorphous unstretched film, and then the unstretched film is biaxially stretched and heat-set. Manufactured by relaxation heat treatment. Other than that, the surface properties of the film vary depending on the particle diameter of carbon black particles and spherical silica particles, the content ii, etc., and also depending on the stretching conditions, so they are appropriately selected from conventional stretching conditions. Furthermore, since the density, thermal shrinkage rate, etc. change depending on the temperature magnification, speed, etc. during stretching and heat treatment, conditions are determined to satisfy these characteristics at the same time.

For example, the stretching temperature ranges from (Tg - 10) to (Tg + 45) °C (Tg: glass transition temperature of polyester) at the first stage stretching temperature (e.g. longitudinal stretching temperature 2 T1) to the second stage stretching temperature. (For example, lateral direction stretching temperature *:'rt) is preferably selected from the range of (T, +15) to (T, +40)°C. In addition, the stretching magnification in one direction is 2.5 or more, sometimes 3 times 1.
It is preferable to select from a range where the area magnification is 8 times or more, particularly 10 times or more on the table. Historically, the heat fixation temperature is 18
It is preferable to select from the range of 0 to 250°C, preferably 200 to 230°C.

The biaxially oriented polynis glue film of the present invention is.

Compared to conventional products, it not only has excellent light-shielding properties due to the inclusion of carbon black, but also has high uniformity due to the spherical silica particles with extremely sharp particle size distribution in addition to the carbon black protrusions. It has protrusions and has excellent running properties and wear resistance. Therefore, when the biaxially oriented polyester film of the present invention is used as a base film for a magnetic recording medium, it has excellent electromagnetic conversion characteristics, runnability, abrasion resistance, etc., and can be used as a base film for magnetic recording media. A magnetic recording medium with detectable light blocking properties can be manufactured.

〔Example〕

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

Incidentally, the physical a value and characteristics of cypress in the present invention were measured as follows.

(1) Particle size of particles There is a long history of measuring particle size.

l) When extracting the average a diameter 1 particle size ratio etc. from the powder 2) When calculating the average particle size of the particles in the film, the rice diameter, etc. l) When using the powder A thin gold film JI layer is formed on the surface with a thickness of 200 to 300 Å using a gold sputtering device, and a thickness of 1 O, 000 to 300 Å is measured using a scanning electron microscope.
Observe at a magnification of 1,000 times, and measure the length of at least 100 particles (
Dli), *diameter (Dsl), and round grade circle equivalent (Di) are determined. Then, the major axis (DI), minor axis (Da), and average particle diameter (D) of the particles are fitted using the number average values expressed by these following equations.

D=(ΣDi)/n! ++1 2) In the case of particles in a film, a small piece of the sample film was fixed on a sample stage for scanning electron microscopy, and sputtering device it (JF'C-
The surface of the film is subjected to ion etching treatment using a 1100al ion etching apparatus i) under the following conditions.

The conditions were to place the sample in a Pel jar and apply a pressure of approximately 10-3To.
Raise the degree of vacuum to a vacuum state of rr, voltage 0.25 kV,
Ion etching is carried out for about 10 minutes at a current of 12.5 mA. Previously, using the same equipment, gold sputtering was applied to the film surface, and a scanning electron microscope was used to measure, for example, lO,0.
Observe at 00 to 30.000 times magnification, and use the Japanese regulator■
The major diameter (Dli) of at least 100 particles at Ura Luzenkus 500.

Combine the short diameter (Dgi) and the equivalent diameter for area (Di).

The following steps are carried out in the same manner as in 1) above.

(2) Film surface roughness (Ra) Center line average roughness (Ra) as JIS-Ba2O3
In the present invention, 61Q is determined using a stylus-type surface roughness needle (5URFCORDER8E-30C) manufactured by Koita Research Institute. The measurement condition number is as before.

ta + Stylus tip radius = 2 μm (bl Measurement pressure: 30 da (e) Cut-off': 0.25 m (di Measurement length: 2.5 mm (・) How to summarize the data - Repeat 6 + lj for the same sample 5 times, and determine the most Exclude one large value, round off the average value of the remaining four Daegoos to the fourth decimal place, and display it to the third decimal place.

(3) Coefficient of friction (μk) of film @ In an environment of 0°C and 60% humidity, a film cut to a width of 172 inches was placed on a fixed rod (surface roughness 0.3 pm) at an angle θ = (1
52/l 8. Contact with radian (152°) and move at a speed of 200α/min hh<*rubbing). The exit tension (T,:,V) when the tension controller is adjusted so that the entrance tension T1 is 35y is detected by the exit tension detector after the film has traveled 90m, and the following formula is used to determine the exit tension #! Calculate the friction coefficient μk.

μ = (2,303/θ) +og (Tl/ TI
)=Oj1681■(Tt/as) (4) The abrasion resistance of the walking surface of the abrasion-resistant film is evaluated using a 5-stage mini super calendar. The calender is a five-stage calender consisting of nylon rolls and steel rolls, and the treatment temperature is 80°C, the linear pressure applied to the film is 2001 tg/α, and the film is run at a speed of 50 m/min. After running the running film for a total length of 2,000 m, the abrasion resistance of the base film was determined to be #111 due to dirt that adhered to the top roller of the calendar.

4-level judgment> ◎ No stains on the nylon roll 0 Almost no stains on the nylon roll
) to measure the light transmittance of the film at a wave i of 900 nm.

Examples 1 to 3 and Comparative Example 1 Polyethylene terephthalate containing carbon black with different average particle sizes, and an average particle size of 0.60 μm,
Polyethylene derephthalate containing spherical silica particles with a particle size ratio of 1.15 and a relative standard deviation of 0.25 was blended so as to have the additive chastity shown in Table 1, and In this case, polyethylene terephthalate containing substantially no lubricant was blended in a VTI grinder to obtain a two-layer polyester film having a thickness of 14 μm using a conventional method.

Table 1 shows the % characteristic measurement results of this film.

il Examples 4 to 7 and Comparative Example 2 Although the average particle size is different from polyethylene terephthalate containing carbon black with an average particle size of 0.30 μm, the particle size ratio and relative a difference are 1.2 and 0, respectively. .2
Polyethylene terephthalate containing spherical silica particles of No. 5 was prepared to a thickness of 14 μm in the same manner as in Example 1.
A biaxially wound polyethylene terephthalate film of m was obtained.

The results of measuring each characteristic of this film are shown in Figure 2.

Fitting 2 Examples 8 to 10 and Comparative Example 3.4 Polyethylene terephthalate containing carbon black with an average particle size of 0.30 μm, average particle size 9 particle size ratio and relative standard deviation of 0.60. 1.15.0.
A two-way oriented polyethylene terephthalate film having a thickness of 75 μm was obtained in the same manner as in Example 1, using polyethylene pre-7 tallate containing spherical silica particles of No. 25 and varying the carbon black content. Table 3 shows the results of each characteristic of this film.

Table 3 Example 11 and Comparative Example 5.6 Polyethylene terephthalate containing carbon black with an average particle size of 0.30 μm and polyethylene terephthalate containing carbon black with an average particle size of 0.60 μm
A thickness of 14 μm was prepared in the same manner as in Example 1 using polyethylene pre-7 tallate containing spherical silica particles with different diameter ratios or different relative standard deviations.
A biaxial MrO] polyethylene terephthalate film of μm was obtained. Comparative Example 7 A film with a thickness of 14 μm was prepared in the same manner as in Example 1 using only polyethylene terephthalate containing carbon black with an average particle size of 0.3 μm. An axially oriented polyethylene terephthalate film was obtained. Q of this film! rI
#Sex measurement results are shown in Acupuncture 4.

Table 4 As shown in the Examples and Comparative Examples above, according to the present invention, a biaxially oriented fixed ester film that has low light transmittance, is flat, has excellent running properties, and has excellent abrasion resistance is produced. can get.

Claims (1)

[Claims] 1. Contains 0.15 to 7.0% by weight of carbon black with an average particle size of 0.01 to 0.6 μm, and has an average particle size of 0.01 to 0.6 μm.
Spherical silica having a diameter of 1 to 1.2 μm and a particle size ratio defined by major axis / minor axis of 1.0 to 1.4 is 0.005 to 1.0
A biaxially oriented polyester film characterized by containing % by weight. 2. The biaxially oriented polyester film according to claim 1, wherein the average particle size of the spherical silica is the same as or larger than the average particle size of the carbon black. 3. The biaxially oriented polyester film according to claim 1 or 2, wherein the relative standard deviation of the spherical silica particles expressed by the following formula is 0.5 or less. Relative standard deviation=√[(Σ＾n_i_=_1)(Di-@
D@) ＾2/n]/@D@where Di; diameter equivalent to area circle of each particle (μm) @D@; average value of diameter equivalent to area circle @D@=(Σ＾n_i_=_1) Di/n (μm)n;
Represents the number of particles.