JPS62252522A - Base film for magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a base film which excels in both of an electromagnetic conversion characteristic and runnability by incorporating inert pulverized inorg. particles having a specific average grain size and grain size distribution into a specific polyester. CONSTITUTION:This base film is a biaxially oriented film essentially consisting of the polyester having the structural unit expressed by the formula I as a main repeating unit and the compsn. contg. 0.03-2.0wt% pulverized inorg. particles having 0.03-2.5mum average grain size. The volumetric fraction of the particles sized >=1.3 times the average grain size of the pulverized inorg. particles is 5-45% of the entire part and the average grain size in 5% (vol%) of the particles of the larger grain sizes is 1.3-10 times the average grain size of the entire particle. The base film for the magnetic recording medium having the excellent runnability is thus obtd. without spoiling the electromagnetic conversion characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a base film for magnetic recording media, and more particularly to a base film suitable for video tapes and floppy disks.

[Prior Art] As a base film for a magnetic recording medium, a polyethylene terephthalate film containing inert inorganic particles is known (for example, Japanese Patent Publication No. 31205/1983).

[Problems to be solved by the invention] However, the above-mentioned conventional base film for magnetic recording media has the following problems:
In order to reduce the cost of video tapes, especially video tapes, there has been a drawback that the running properties of video tapes used without back coating are insufficient.

An object of the present invention is to improve such problems and provide a base film for a magnetic recording medium that has excellent running properties without impairing electromagnetic conversion characteristics when used as a magnetic recording medium.

[Means for Solving the Problems] The present invention comprises a polyester having the following structural unit as a main repeating unit and 0.03 to 2.0% by weight of inorganic fine particles having an average particle size of 0.03 to 2.5 μm. A biaxially oriented film mainly composed of a composition in which the inorganic fine particles have a volume fraction of particles having a particle size of 1.3 times or more the average particle size of the whole.
~45%, and the average particle size of 5% (volume %) of particles from the largest particle size is 1% of the average particle size of all particles.
The present invention relates to a base film for a magnetic recording medium, which is characterized by having a magnetic recording medium thickness of 3 to 10 times.

-G-0 (at least one type of dicarboxylic acid residue selected from -CH2hO-Q-).

In the present invention, "Bolier" stell is a polyester having the above structural unit as a main repeating unit, and R is (Σ
, "] springT+0+CHsρ(), where R is -).

CD.

This is particularly desirable because the running properties become even better. Also, within a range that does not impede the present invention, preferably 10
Other components other than the above may be copolymerized as long as the amount is within mol%.

The average particle size of the inorganic fine particles in the present invention is 0.03 to 2.
It needs to be in the range of 5 μm, preferably 0.07 to 2.3 μm, more preferably 0.10 to 2.0 μm. If the average particle size is smaller than the above range, the runnability will be poor, whereas if it is larger than the above range, the electromagnetic conversion characteristics will be poor, which is not preferable.

The composition used in the present invention contains the above-mentioned inorganic fine particles at a concentration of 0°03 to
It is necessary to contain 2.0% by weight, preferably 0.05 to 1.5% by weight, and preferably 0.1 to 1.0% by weight. If the content is less than the above range, the runnability will be poor, and if it is too much, the electromagnetic conversion characteristics will be poor, which is not preferable.

When using two or more types of inorganic fine particles, it is necessary that the total amount thereof satisfies the above content.

Further, the inorganic fine particles in the present invention have an average particle size of 1.3
It is necessary that the volume fraction of particles having twice or more the particle size is 5 to 45% of the total, preferably 10 to 40%. If the above volume fraction is smaller than the above range, running properties will be poor;
On the other hand, if it is large, the electromagnetic conversion characteristics will be poor, which is not preferable.

Further, in the inorganic fine particles in the present invention, the average particle size of 5% (volume %) of particles from the largest particle size is 1.3 to 10 times, preferably 1.5 to 8 times, the average particle size of all particles. .0
It is necessary that the amount is approximately 1.5 times to 6.0 times. If the average particle size of 5% (volume %) of particles from the largest particle size is smaller than the above range, runnability will be poor, whereas if it is large, electromagnetic conversion characteristics will be poor, which is not preferable.

In addition, the average particle size (μm) of 5% (volume %) of particles from the larger particle size of the inorganic fine particles in the present invention is 02
When the thickness of the magnetic layer (μm) is χ3, a magnetic recording medium with a ratio of da2 to g3 (e3/952> in the range of 0°2 to 8.0) has good running properties and electromagnetic conversion characteristics. This is particularly desirable because it provides even better results.

The fine particles used in the present invention are particularly desirable when they have a Mohs hardness of 5 or less, since the improvement in runnability is particularly remarkable due to the limitation of particle size characteristics.

The inorganic fine particles in the present invention are not particularly limited, but when they are metal halide compounds having a fluorite structure or a rutile structure, the runnability is particularly markedly improved by limiting the particle size characteristics of the inorganic fine particles as described above. In particular, when the halogen is fluorine, the effect of limiting the particle size characteristics is quite remarkable;
VIQFz.

MnF2 is particularly desirable because the running properties are even better due to its roughness.

The film of the present invention has the above-mentioned composition as its main component, but other polymers may be blended within the range that does not impede the purpose of the present invention, and antioxidants, heat stabilizers, lubricants, and ultraviolet absorbers may be added. , nucleating agents, and other inorganic or organic additives may be added to the extent that they are normally added. Further, inorganic particles outside the scope of the present invention may be added within a range that does not impede the purpose of the present invention.

The film of the present invention is a film in which the above composition is biaxially oriented. An unoriented film or a -axis oriented film is not preferable because it results in poor running properties and electromagnetic conversion characteristics.

In addition, the plane orientation index of the film of the present invention is 0.935 to 0.
．． 975, especially 0.940-0.970, is particularly desirable because the running properties are even better.

Further, the density index of the film of the present invention is 0.02 to 0.0
A range of 5 is particularly desirable because the running properties become even better.

The film of the present invention has a static friction coefficient of 0.4 to 4 in the width direction between the films. It is particularly desirable that the OI is in the range of 0.6 to 3.0, since the runnability becomes even better.

The film of the present invention has an average surface roughness Ra of 0.0 in the width direction.
04-0.025μm, especially 0.005-0.020μm
A range of m is particularly desirable because running properties and Nwi conversion characteristics become even better.

The film of the present invention has a melt viscosity of 800 to 10,000' poise at 290°C and 200 sec-1, particularly 1,000 to 10,000' poise.
A range of 7,000 poise is particularly desirable because running properties and electromagnetic conversion characteristics are even better.

Next, a method for manufacturing the base film for magnetic recording media of the present invention will be explained.

First, the method of incorporating inert inorganic fine particles having a predetermined average particle size can be carried out by a known method.
A method of mixing and dispersing in the diol component of polyester in the form of a slurry is effective for obtaining the average particle size of the present invention. In addition, the method for obtaining the particle size characteristic range of the present invention, that is, the volume fraction of particles with a particle size of 1.3 times or more the average particle size is 5 to 45% of the gold body, and the particle size is larger. 5% (from
To make the average particle size of the particles (volume %) 1.3 to 10 times the average particle size of all particles, two or more types of particles with different average particle sizes are slurried in the diol component of polyester. Alternatively, inorganic particles having an average particle size approximately 1.5 to 30 times larger than the average particle size range of the present invention are dispersed in the form of a slurry in the diol component of polyester, and the mixture is mixed 1 to 50 times per minute. An effective method is to use a mixer that repeatedly turns on and off at the frequency of
The latter method is particularly effective, and the appropriate mixer rotational speed in that case is 10 to 11,000 rpm.

Next, the diol component containing the thus obtained inorganic particles and a predetermined dicarbon ri (or its ester) are polycondensed by a known method to obtain a predetermined polyester.

After thoroughly drying the polyester pellets, the polyester pellets are fed into a known melt extruder and extruded into a sheet through a slit die at a temperature above the melting temperature of the pellets and below the temperature at which the polymer decomposes, and then cooled and solidified. to make an unstretched film. In this case, the method of temporarily extruding through a filter whose 95% cut diameter measured by the coulter counter 7 is 2 to 40 times, particularly 3 to 20 times, the desired average particle diameter is suitable for adjusting the particle size characteristics to the range of the present invention. That is, the volume fraction of particles with a particle size of 1.3 times or more than the average particle size is 5 to 45% of the total, and the average particle size of the particles in 5% (volume %) from the larger particle size. It is extremely effective in making the average particle size of all particles 1.3 to 10 times.

Next, this unstretched film is biaxially stretched and oriented. As the stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used, but a sequential biaxial stretching method is particularly preferred. In this case, the stretching conditions include longitudinal direction,
A method in which the material is stretched 3.0 to 4.0 times in the longitudinal direction and then 3.2 to 4.5 times in the width direction at a temperature in the range of not less than the glass transition point of the polymer and not more than the cold crystallization temperature in both width directions. is suitable. The stretching speed is preferably in the range of 103 to 107%/min. Further, a method of roughly stretching the stretched film in at least one direction is effective for further improving the running properties of the film.

Next, the stretched film is heat treated, and the heat treatment conditions in this case include a temperature of 180°C to 230°C, preferably 19°C.
A method of heat treatment in the range of 0° C. to 220° C. for 0.5 to 60 seconds is effective for further improving the running properties of the film. In addition, it is effective to perform the heat treatment under a fixed length to further improve running properties.

Although the base film for magnetic recording media of the present invention has been described below, the film of the present invention may be subjected to a known corona discharge treatment, or may be imparted with adhesion, moisture resistance, heat sealability, slipperiness, etc. For this purpose, the trusted polymers may be used in the form of a laminate or coated with other organic or inorganic compositions.

[Function] Since the present invention is a film made of polyester containing inert inorganic particles having a specific average particle size and particle size distribution, the accompanying airflow that accompanies the running of a magnetic tape etc. will affect the running properties of the tape. This shows that the effects of the present invention can be obtained.

[Method of Measuring Physical Properties and Evaluating Effects] The methods of measuring the characteristic values and evaluating the effects of the present invention are as follows.

(1) Polyester is removed from a film with an average particle size of inorganic fine particles using a plasma ashing treatment method or an O-chlorophenol dissolution method, and this is dispersed in ethanol, followed by a stretch sedimentation method (Horiba, CAPA5
00) is the volume average diameter measured.

(2) Content of inorganic fine particles: 1°OD of O-chlorophenol per 100g of polyester
, and heated at 120℃ for 3 hours, Hitachi Koki Co., Ltd.
Using bean paste centrifuge 55P-72, 30° o o o r
Centrifugation was performed at pm for 40 minutes, and the resulting particles were
Vacuum dry at 0°C. When the fine particles are measured using a scanning differential calorimeter, if a melting peak corresponding to the polymer is observed, the fine particles are heated and cooled with O-chlorophenol and then centrifuged again. When the melting peak is no longer observed, the fine particles are considered to be precipitated particles. Normally centrifugation operation is 2
times is enough.

(3) Glass transition point Tg, cooling temperature TCC Measured using a DSC (Differential Scanning Calorimeter) Model 2 manufactured by PerkinElmer. The DSC measurement conditions are as follows. That is, a 10 mm sample film is set in a DSG device, melted at a temperature of +30° C. (melting point +30° C.) for 5 minutes, and then placed in liquid nitrogen at vital points. This rapidly cooled sample is heated at a rate of 10° C./min, and the glass transition point g is detected. The temperature was continued to rise gradually, and the peak temperature of crystallization exotherm from the glass state was defined as the cold crystallization temperature TCC.

(4) Planar orientation index Using a refractometer with sodium D line (wavelength 589 nm) as a light source, measure the refractive index in the thickness direction of the biaxially oriented film (referred to as A) and place it in water at 10°C after melt pressing. The refractive index (referred to as B) in the thickness direction of the non-oriented (amorphous) film produced by rapid cooling was measured, and A/B was taken as the plane orientation index. Using methylene iodide as the mounting solution,
Measurement was performed at 5° C. and 65% RH.

(5) Density index The density of the film measured using a density gradient tube made of n-hebutane/carbon tetrachloride was set as dl (Q/cm), and the film was melt-pressed and quenched in water at 10'C. The difference from the density d2 of the non-oriented amorphous film made by the method, (dl-d2 >), was taken as the density index.

(6) Static friction coefficient (width direction) Using a slip tester made by Toyo Testa, ASTM-D-
Measurements were made by sliding the film in the width direction according to 1894-63.

(7) Using a melt viscosity enhancement type flow tester, measurement was performed at a temperature of 290° C. and a speed of 200 sec-x.

(8) Surface average roughness Ra Measured using a stylus type surface roughness meter according to JIS-B-0601. However, the cutoff is o, oamm,
The measurement length was 1 mm.

(9) Electromagnetic conversion characteristics γ-F0203100 interspace, 15 parts by weight of vinyl chloride-vinyl acetate copolymer, 15 parts by weight of polyurethane elastomer, 8 parts by weight of carbon black, 120 parts by weight of methyl ethyl ketone, 130 parts by weight of methyl isobutyl ketone,
A magnetic paint was prepared by thoroughly mixing and dispersing a mixture of 2 parts by weight of myristylic acid in a sand mill, 15 parts by weight of polyisocyanate (Coronate L) was added to this magnetic paint, and this was applied to a sample polyester film to a thickness of 4. 0 μm (
After coating (dry thickness) and calendering (at 90 degrees Celsius, linear pressure 200 kq/cm), the tape was slit into 1/2 inch width. This tape was incorporated into a VH3 video cassette (120 minutes) to create a video cassette tape.

Using a VTR on this tape, a TV test signal generator ((
After recording the signal from Shibaku ITG-7/1), it was recorded for 100 passes (120 minutes x
100 passes). Using this tape, a dropout counter was used to pick up and drop out signals with a dropout width of 5 microseconds or more and a reproduced signal attenuation of -16 dB or more. The measurement was carried out on 10 volumes of video cassettes, and when the number of dropouts per minute was less than 10, the electromagnetic conversion characteristics were considered to be good, and when it was 10 or more, the electromagnetic conversion characteristics were judged to be poor.

00) Running properties: Set the above tape on a VTR, 25°C, 50% RH.
After running 100 passes at 40°C and 80% RH, rank each of the following items on a 5-point scale, and if the total score for all items is 15 to 10, the running performance is good; If it was 9 or less, the running performance was determined to be poor.

The five-level ranking is based on the number of samples that do not satisfy each of the following items among the 50 volumes: 0 to 1.
5 points for 2 to 3 pieces, 4 points for 4 to 6 pieces, 3 points for 4 to 6 pieces, 2 points for 7 to 9 pieces, and 1 point for 10 or more pieces.

a) The edges of the tape do not break (do not buckle) b) The tape does not stretch and become seaweed-like C) There is no generation of fine powder due to tape abrasion (magnetic layer and base film layer) [Example: The present invention was carried out] Let's explain based on an example.

Examples 1 to 4, Comparative Examples 1 to 8 Calcium fluoride (CaF2, reagent grade) manufactured by Kanto Chemical Co., Ltd.
Alternatively, silica (TT-600> manufactured by Nippon Aerosil) was mixed and dispersed in the form of a slurry by changing the dispersion method in various ways, and transesterified and polycondensed with dimethyl terephthalate, as shown in Table 1. average particle size,
Polyethylene terephthalate containing calcium fluoride and silica having particle size characteristics in amounts shown in Table 1 was prepared.

This polyethylene terephthalate pellet was heated to 180°C.
The mixture was dried under reduced pressure (3 Torr) for 3 hours.

The pellets were fed to an extruder and melted and extruded at 300°C.
Using an electrostatic casting method, it is wound around a casting drum with a surface temperature of 30°C, cooled and solidified, to a thickness of approximately 170°C.
An unstretched film of μm was made. This unstretched film was stretched 3.4 times in the longitudinal direction at 90°C.

This stretching was carried out using a difference in peripheral speed between two sets of rolls, and the stretching speed was 10,000%/min. This -axis film was stretched 3.6 times in the width direction at 100°C at a stretching rate of 2000%/min using a stenter, and heat treated at 210°C for 5 seconds under constant length to obtain a film with a thickness of 14 μm. . The average particle size, particle size characteristics, and content of inorganic particles in this film were as shown in Table 1.

When this base film is used as a magnetic recording medium, the running properties and electromagnetic conversion characteristics are as shown in Table 1. If the volume fraction and average particle size of 5% (volume %) of particles from the largest particle size are within the range of the present invention, a product with excellent running properties and electromagnetic conversion characteristics can be obtained, as shown in Table 1. Examples 1 to 4) However, when the particle size characteristics were outside the range of the present invention, it was not possible to obtain a product that had both runnability and electromagnetic conversion characteristics (Table 1, Comparative Examples 1 to 8).

Examples 5 to 10 Magnesium fluoride (MQF2, reagent Ex
pure grade) and calcium carbonate (C
aCO3) etc. were mixed and dispersed in ethylene glycol in the form of a slurry, followed by transesterification and polycondensation with α,β-bis(2-chlorophenoxy)ethane 4,4-dicarboxylic acid dimethyl, as shown in Table 2. Polyethylene containing magnesium fluoride, calcium carbonate, etc. in the amounts shown in Table 2, having the average particle size and particle size characteristics.
α,β-bis(2-chlorophenoxy)ethane 4,4′-dicarboxylate was obtained.

This polyester pellet was dried under reduced pressure (3 Torr) at 180° C. for 3 hours. This pellet was fed into an extruder and melt-extruded at 300°C, then wound around a casting drum with a surface temperature of 30°C using electrostatic and force casting methods, and cooled and solidified to produce an unstretched film with a thickness of approximately 220 μm. Ta. This unstretched film was heated at 120°C for 3
．． It was stretched 8 times.

It is preferable to use it for tape etc.

This stretching was carried out using a difference in peripheral speed between two sets of rolls, and the stretching speed was 10,000%/min. This -axis film was stretched 4.2 times in the width direction at 120°C at a stretching rate of 2000%/min using a stenter, and heat treated at 210°C for 5 seconds under constant length to obtain a film with a thickness of 14 μm. . The average particle size, particle size characteristics, and content of inorganic particles in this film were as shown in Table 2.

When these base films were used as magnetic recording media, the running properties and electromagnetic conversion characteristics were both good as shown in Table 2.

[Effects of the Invention] Since the present invention uses a polyester film having a specific particle size and particle size parameters, a base film with excellent electromagnetic conversion characteristics and runnability when used as a magnetic recording medium can be obtained. be.

Claims (1)

[Scope of Claims] Polyester having the following structural unit as a main repeating unit and inorganic fine particles with an average particle size of 0.03 to 2.5 μm.
03 to 2.0% by weight, the inorganic fine particles have an average particle size of 1.0% by weight.
The volume fraction of particles with a particle size of 3 times or more is 5 to 45% of the total, and the average particle size of 5% (volume %) of particles from the largest particle size is the average particle size of all particles. 1.3-10
A base film for magnetic recording media, which is characterized by being twice as thick. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ Here, R is ▲There are mathematical formulas, chemical formulas, tables, etc.▼, ▲There are mathematical formulas, chemical formulas, tables, etc.▼, ▲There are mathematical formulas, chemical formulas, tables, etc.▼ ▲Mathematical formulas, There are chemical formulas, tables, etc. ▼ At least one type of dicarboxylic acid residue selected from.