JPS61209127A - Manufacture of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium excellent in running propery and electromagnetic conversion characteristic by a method wherein polyester film, the degree of surface roughness of which lines within he range of a certain value and the number of secondary Moire fringes measured with the multiple interference method before and after the calendering treatment of which satisfies a certain formula, is employed. CONSTITUTION:Polyester film, of which the degree of surface roughness Ra measured with the tracer type roughness degree meter lies within the range of 0.015-0.025mum, Ra of which does not substantially change before and after the calendering treatment, and of which the number of secondary Moire fringes, H2/mm<2>, measured with the multiple interference method before and after the calendering treatment satisfies the formula (1), is employed. As for the polyester film, no limitation exists as long as the raw polyester material contains at least one kind of such inactive particles and consequently H2 before the calendering treatment is 50-300/mm<2> and H2 after the calendering treatment satisfies the formula (a) and preferably separates out particles, in which calcium and phosphorous atoms or barium sulfate are contained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides a polyester film having novel properties, in particular a specific surface roughness and a number H of secondary interference fringes measured by multiple interferometry! The present invention relates to a method for manufacturing a magnetic recording medium using a polyester film having the following properties.

Conventional technology and problems to be solved A so-called binder-type magnetic tape, which is based on a film and coated with a magnetic paint containing magnetic powder and a binder as its main components, is manufactured using a coating process and coating process. surface finishing process,
Manufactured through processes such as super calendering. In these steps, smooth running of the film without meandering or wrinkling is an important property in producing a homogeneous magnetic recording medium. For this purpose, it is known to reduce the coefficient of friction by imparting appropriate irregularities to the surface of the film.

On the other hand, magnetic recording media, especially for video cassettes, are required to have higher performance electromagnetic conversion characteristics and higher image quality, and for this reason, the base film is required to have a flatter surface roughness.

Therefore, conventionally, video tapes using base films with good running properties and moderate roughness have a luminance output distortion ratio (Y/
N') It has the disadvantage of a low color output distortion ratio CC/N'), and in pursuit of high image quality, methods such as producing video tapes using base films with flat surfaces have been taken. However, Kolera's method had the drawbacks of increased costs and concerns about running durability.

Various attempts have been made to satisfy the trade-offs between flatness and runnability, but in practice it is still difficult to measure the surface roughness of the base film by using a stylus roughness meter, for example. The measured surface roughness Ra is 0.015 to 0.0
The current situation is that a method is used to provide a roughness of 25 μm.

As a method for appropriately roughening the film surface, from the viewpoint of economic efficiency and the effects it can bring, a method of pre-existing organic or inorganic fine particles that are inert to the polyester in the raw material polyester used for film formation is recommended. Widely adopted. Among the protrusions on the film surface produced by this method, relatively tall protrusions, for example, protrusions with a height of 0.54 to 0.71 μ that give secondary interference fringes when measured by multiple interference (hereinafter abbreviated as H2) are not suitable for traveling. Although it has a remarkable effect on improving properties, on the other hand it has a negative effect on electromagnetic conversion properties.

Conventionally, in order to impart roughness to the film surface, a method has been used in which precipitated particles or additive particles are added and protrusions are formed on the film surface through a biaxial stretching process. Since the added particles inevitably have a certain particle size distribution and number distribution, they will include protrusions of unnecessary height (large protrusions), but such large protrusions are Electromagnetic conversion characteristics of tape, especially color S/
This results in a decrease in N.

Means for Solving the Problems It is an object of the present invention to manufacture a magnetic recording medium that is excellent in both running properties and electromagnetic conversion properties, which are considered to be difficult to achieve as described above.

In order to obtain a magnetic recording medium with excellent runnability and electromagnetic conversion characteristics, the present inventors have conducted extensive research and found that the conventional method of adding precipitated particles or additive particles to impart film surface roughness is not sufficient. Unnecessarily high protrusions (large protrusions) occur, and this affects the electromagnetic characteristics of videotape, especially color S/
This book investigates the factors that reduce N, and also discovers that these large protrusions (H2) are usually slightly reduced during the surface finishing process, resulting in a magnetic coated body with excellent running properties and electromagnetic conversion characteristics They had arrived at an inventive method. That is, before the surface finishing process, there are many large protrusions (Hl), so excellent running properties are obtained, and after the treatment, the large protrusions are reduced to 1/3 to 174 of that of conventional products, so the surface protrusions are They obtained new knowledge that a base film can be obtained that makes it possible to manufacture a magnetic recording medium with excellent electromagnetic conversion characteristics, despite the large number of Normally, in order to manufacture a magnetic recording material, magnetic layer coating, magnetic orientation, drying, and surface treatment, that is, calendering steps are performed. It is important to study changes in the surface roughness of the film, and if a base film in which H2 can change before and after the calendering process is used,
Gaining new knowledge that these problems can be solved all at once,
The present invention has now been completed.

The present invention is particularly suitable for Ra=0.015 to 0.025 in the step before the calendering step where runnability is required.
This is satisfied by providing a suitable average roughness expressed in μm and by the presence of a specific amount of H2,
Moreover, by reducing the H2 in the calendering process, excellent electromagnetic conversion characteristics necessary for the final product can be imparted.

That is, the present invention provides a magnetic layer on a polyester film,
In the method of manufacturing a magnetic recording medium by subsequently calendering, the surface roughness Ra measured using a stylus roughness meter is 0.015 μm to 0.025 μm, and Ra is substantially A magnetic material characterized by using a polyester film which does not change in color and the number H2 (pieces/dragon 2) of secondary interference fringes measured by multiple interferometry satisfies the following formula before and after calendering. The present invention relates to a method for manufacturing a recording medium.

The present invention will be explained in more detail below.

The polyester in the present invention refers to a polyester containing 80 moles or more, preferably 90 moles or more of ethylene terephthalate units, and the polyester contains 50 to 300 ethylene terephthalate units/2 rows when formed into a film.

It is necessary to contain organic or inorganic fine particles that are inert to the polyester.

The polyethylene terephthalate referred to in the present invention is
A polyethylene terephthalate containing polyethylene terephthalate and a third component of 20 or less. Generally, polyethylene terephthalate is produced by condensing terephthalic acid or a functional derivative thereof and ethylene glycol or a functional derivative thereof in the presence of a catalyst under appropriate conditions. Before or after the completion of the polymerization of polyethylene terephthalate, one or more suitable third components may be added to form a copolymerization or a mixed product. The polymer may also contain stabilizers such as phosphoric acid, phosphorous acid and their esters, titanium oxide lubricants, and the like. Preferable intrinsic viscosity is 0.5-1.0
and more preferably 0.55 to 0.80.

The biaxially stretched polyethylene terephthalate film of the present invention is obtained by melt-extruding the above-mentioned polyethylene terephthalate, and then biaxially stretching and orientating it.

As organic fine particles, one or more metal compounds such as lithium or calcium are made to exist during or after the esterification or transesterification reaction, and after the esterification or transesterification reaction is substantially completed, trivalent and/or trivalent Particle size O11 to 5 formed in polyester with or without addition of one or more phosphorus compounds of
Examples include so-called precipitated particles of about μm size. It is also a hot theory that a salt of an organic carboxylic acid such as calcium terephthalate or a fine powder of a crosslinked polymer compound may be added.

On the other hand, as inorganic fine particles, there are many inorganic compounds known to be added to polyester, such as LiF,
Lis PO4, Mg80. , '3aSO4°CaCO3, Sio□, TiO2, kaolin, celite, etc. These inorganic compounds are usually added to a uniform particle size by pulverization and/or classification treatment.

In the present invention, the polyester film that can be used as the base film of the magnetic recording material contains one or more types of such inert particles in the raw polyester, and as a result, when the film is made, the H, before calendering is 50 to 50.
There is no particular restriction as long as the number of polyesters is 300/dragon 2 and the H2 after treatment satisfies the formula (1), but these are preferably achieved effectively when the following polyesters are used.

One of them is a polyester containing calcium and phosphorus elements in the precipitated particles, and specifically, this polyester can be produced by the following method.

That is, at any point before the start of the polycondensation reaction, the following two
Types of phosphorus compounds (1) Trimethyl phosphate and/or triethyl phosphate (n) Trialkyl phosphite or phosphorous acid represented by P(OR), (R represents an alkyl group having 1 to 4 carbon atoms) Both types have a molar ratio of the phosphorus compound of (1) to the phosphorus compound of (11) from 1 to 20,
and the total amount of the phosphorus compounds (1) and (1) is 0.17 to 4 times the mole of the calcium compound, preferably 0.9 to 3.
It can be produced by adding twice the molar amount.

The polyester obtained by this method contains 1% by weight or more of each of calcium and phosphorus elements and has an average particle size of 0.
．． Particles of about 3 to 3 μm are precipitated and precipitated in an amount of about 0.05 to Q, 5 wt%, and these precipitated particles contribute to improvement of various physical properties of the film including runnability.

Also, one of the polyesters suitable for achieving the present invention is a polyester containing barium sulfate. In this case, barium sulfate is usually added as an ethylene glycol slurry at some point in the polyester manufacturing process, for example before the start of the polycondensation reaction, in order to improve dispersibility in the polyester. 0.2～
5 μm.

Preferably 0.5 to 1.2 μm, the amount added is 0.003 to
It is selected from the range of 1.0% by weight, preferably from 0.01 to 0.5% by weight.

By such a method, a polyester film with a large change in H2 required in the present invention can be obtained, but in this case, the H2 value before calendering needs to be 50 to 300 pieces/2.

If this value is less than Seki, Ra is 0.015 to 0.02
Although it is within the range of 5 μm, the runnability is insufficient, and when this value exceeds 300, the number of interference fringes that give third order or higher order increases when measured by multiple interferometry, and the calendar Even after a processing step, the electromagnetic conversion characteristics deteriorate, and recording signal dropouts, that is, dropouts, occur frequently.

or less than 0.25. This is because, in the case of polyester films containing well-known additive particles such as calcium carbonate and kaolin, this value is usually about 0.7 to 0.9;
This is because if it exceeds 5, the effect of the present invention on the electromagnetic conversion characteristics will not be noticeable.

This value changes not only depending on the particles contained in the polyester film but also on the calendering conditions, and the lower the better, however, even if the polyester film of the present invention is used, it is difficult to completely eliminate H2 in the calendering process. Generally, the practical lower limit of this value is about 0.05.

The features of the present invention have been mainly described above with reference to H2, but another feature of the present invention is the surface roughness Ra of the film.

That is, in the present invention, the surface roughness Ra of the film is 0.
It must be between 0.015 and 0.025 μm. If this value is less than 01015 μm, H8 is added in an appropriate amount, for example 50 to 3
Even if 00 pieces/tomo2 are present, the runnability will be insufficient. On the other hand, if Ra exceeds 0.025 μm, the runnability will be excellent, but the roughness will become too large and the electromagnetic conversion characteristics will deteriorate. become.

One of the features regarding Ra in the present invention is that this value does not substantially change before and after the calendering process.

That is, although relatively large protrusions, ie, H2, are drastically reduced in calendering, many smaller protrusions that contribute to Ra remain as they are, so it is considered that Ra does not substantially change. It is desirable for Ra to remain essentially unchanged in terms of stability of the electromagnetic conversion characteristics of the magnetic tape.

Although any treatment method can be applied to the calendering process in the present invention, supercalendaring process is usually applied.

The supercalender treatment is a surface finishing treatment consisting of an elastic roll and a mirror roll, and has the effect of not only smoothing the surface on which the magnetic layer is coated, but also reducing protrusions on the back surface. It is known that the protrusions on the back surface are transferred to the surface of the magnetic layer when the coated magnetic layer is wound up into a roll, and smoothness is required.

The calendering conditions were a roll temperature of 70 to 100°C, a linear pressure of 100 to 300 kg/cIrL1 speed of 50 to 70 m.
/ min, 5-stage supercalender, hard chrome surface roughness, RIZ = 0.02 fim-0,05μ
A nylon resin roll can be used to set the surface roughness Ra of the elastic roll to 0.5 to 0.7 μm.

In order to obtain the film used in the present invention, the raw material polyester must be subjected to a known film forming method, for example, usually from 270°C to 29°C.
After melting and extruding into a film at 5°C, cooling and solidifying at 50 to 70°C to form an amorphous sheet, it is lengthwise.

Transversely biaxial stretching or simultaneous biaxial stretching, 160~2
Methods such as heat treatment at 40°C (for example,
A film can be formed by applying the method described in Japanese Patent No. 639.

Function The present invention provides a polyester film for a base of a magnetic recording medium with a surface roughness [Ra of 0.015μfrl].
By being ~0.025 μm, the runnability is excellent, and by setting the number H2 ratio of secondary interference fringes before and after calendering to 0105 to 0.5,
This provides excellent electromagnetic conversion characteristics.

EXAMPLES Hereinafter, the present invention will be explained in more detail based on Examples and Comparative Examples. However, it goes without saying that the present invention is not limited to these.

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

The method for measuring each physical property of the film is shown below.

Quantification of the number of secondary interference fringes by multiple interference method: Measurement was performed using a surface finish manufactured by Nippon Kogaku Co., Ltd. and an attached multiple interference device.

The measurement wavelength is 0354 μm, and the number of interference fringes that provide a secondary link per unit area (mm2) is H1, H,.

H3 was measured. In this case H1 is 0.27~0.54μ
tn, H, is 0.54 to 0.71 μm, H3 is 0.
This corresponds to the number of pieces with a height of 71 to 0.98 μm.

Coefficient of friction (μd) F/Me Fixed hard chrome plated metal roll (diameter 6mm, 2s
) with a wrapping angle of 135° (θ),
Apply a load of s3.1Tz) to one end and run it at a speed of 1m/lnm to calculate the resistance force (T, (1)) at the other end.
) was measured, and the coefficient of friction (μm) during running was determined using the following formula.

Sample 200 ~ phenol/tetrachloroethane = 50
Add to 20 frLl of mixed solution of 150 and 1
After heating and dissolving for a period of time, measurement was performed at 30'O.

A sample film with an F5 value of 1/2 inch width and a length of 5OffilI between chucks was placed in a Tensilon (UTM) manufactured by Toyo Baldwin Co., Ltd.
■), 50m1t/at 20'0165%RH
The load at 5% elongation was divided by the initial cross-sectional area and expressed in kg/home.

It was determined as follows using a surface roughness measuring device (SR-3FK) manufactured by Koita Research Institute. The tip radius of the stylus was 2 μm, and the load was 30 mg. A part with a reference length L (2, smm) is extracted from the film cross-sectional curve in the direction of its center line, and the roughness curve y = f (with the center line of this extracted part as the X axis and the direction of vertical magnification as the Y axis) x), the value given by the following formula is expressed in μm. However, the cut-off value was 80 μm.For 0E%H1, the average value of a total of 10 points, 5 points in the vertical direction and 5 points in the horizontal direction, was determined.

After aluminum evaporation is applied to the film surface, interference fringes are produced at a measurement wavelength of 0.54 μm by multiple interference method using a surface finish microscope manufactured by Nippon Kogaku Co., Ltd., and the interference fringes are photographed to determine the n-order interference. Count the number of stripes and convert to 1 mm. During the measurement, the mirror reflectance was 65 inches and the microscope magnification was 200 times.

Using a commercially available household VTFt, chroma 8/N was measured with a Shibaku NTSC video noise measuring device Q25R.

A tape made of a base film of a known technique having no depressions was used as a reference tape and designated as 0cZB.

Example 1 100 parts of dimethyl terephthalate, 70 parts of ethylene glycol, and 1,000 parts of calcium acetate hydrate were placed in a reactor, and the temperature was raised to distill off methanol to carry out a transesterification reaction. It took about 4 hours after the start of the reaction to reach 225
°C, substantially completing the transesterification reaction.

Next, 0.35 part of calcium acetate hydrate and 0.36 part of triethyl phosphite were simultaneously added, and about 8 minutes later, 0.08 part of triethyl phosphite was added. After a further 5 minutes, 0.05 part of antimony trioxide was added as a polymerization catalyst, and then the temperature was started to rise, and after 40 minutes, the internal temperature of the yarn reached 245°C.

Next, at this point, 0.22 parts of magnesium acetate tetrahydrate was added, and then a polycondensation reaction was carried out in a conventional manner.

That is, the temperature gradually increases from 245°C and finally reaches 28°C.
The temperature was allowed to reach 5°C, and the pressure was gradually reduced from normal pressure to reach Q, 5 mx Hy. After 4 hours, the reaction was stopped and a polyester having an intrinsic viscosity of 0.63 was obtained.

In the polyester, many uniform and fine precipitated particles containing Cα and P with an average diameter of about 1 μm were observed.

After drying the polyester in vacuum at 180° C. for 6 hours, a biaxially stretched film was obtained by a conventional method. That is, after extruding a polyester resin onto a rotating cooling roll to form an amorphous film, it was stretched 3.7 times in the machine direction at 80°C, then stretched 3.8 times in the transverse direction at 90°C, Further heat setting was performed at 220°C for 5 seconds to obtain a film with a thickness of 15 μm.

The surface roughness of this product was as shown in Table 1.

Next, when the film was calendered, the secondary protrusions were significantly reduced, and when it was made into a videotape, the output C
/N was obtained.

Comparative Example 1 100 parts of dimethyl terephthalate, 70 parts of ethylene glycol, and 0.1 part of calcium acetate hydrate were placed in a reactor, heated to an elevated temperature, methanol was distilled off, and a transesterification reaction was carried out. It took 4 hours after the start of the reaction to raise the system internal temperature to 230°C, and the transesterification reaction was substantially completed.

Next, 0.4 parts of kaolin particles with an average particle size of 1.1 μm were added, and further 0.04 parts of phosphoric acid and 0.04 parts of antimony trioxide were added.
After adding 0.4 parts, the pressure inside the system was reduced and the temperature was started to increase.Finally, the reaction was carried out at 0.05 mmH1, 280° C. for 4 hours to obtain polyester chips with an intrinsic viscosity of 0.64.

The polyester pubic part and the polyester blade part substantially free of particles were mixed, and after vacuum drying at 180° C. for 6 hours, a biaxially stretched film was obtained by a conventional method. That is, after extruding a polyester resin onto a rotating cooling roll to form an amorphous film, it was stretched 3.7 times in the machine direction at 8°C, then stretched 3.8 times in the transverse direction at 90'O, and then 5 at 220℃
Heat setting was performed for seconds to obtain a film with a thickness of 15 μm.

The surface roughness of the obtained film was as shown in Table 1. When the film was then calendered, the results shown in Table 1 were as follows: the residual rate of secondary and higher protrusions was high, and when it was made into a videotape, the output C/N was reduced.

Comparative example 2゜Comparative example 1. In the same manner as above, a 15 μm thick polyester film containing 0.02 parts of kaolin with an average particle size of 1.1 μm and o, o s parts of calcium carbonate with an average particle size of 1.4 μm was produced.

The properties of the film are listed in Table 1.

Example 2゜Comparative example 1. In the same manner as above, a 15 μm thick polyester film containing 0.02 parts of kaolin particles with an average particle size of 1.1 μm and 0.08 parts of barium sulfate with an average particle size of 1.4 μm was prepared. When the film was then calendered, the residual rate of secondary or higher protrusions was relatively small, at 38 cm. The improvement in C/N was only QJd13.

Films containing barium sulfate with a particle size of around 1 μm are considered to have good properties in terms of surface roughness, etc., but 27M,
Q... is high and running performance is poor. Addition of particles with a diameter of 1.4 mm or more improves running properties, but it significantly deteriorates electromagnetic conversion characteristics, and it is generally considered that their addition is undesirable. Addition of particles having properties such as those observed in this example is useful as a method of satisfying both the conflicting properties of runnability and electromagnetic conversion properties.

Table 1 Effects of the Invention As detailed above, the present invention provides a magnetic recording medium obtained by providing a magnetic layer on a polyester film and then calendering the surface roughness measured using a stylus roughness meter. Ra is 0015 μm to 0.025 μm, and this Ra does not substantially change before and after calendering,
In addition, by using a polyester film whose number H2 ratio of secondary interference fringes measured by multiple interferometry is 0.05 to 0.5 before and after calendering, it is possible to improve runnability and electromagnetic properties, which had been difficult to achieve at the same time. A magnetic recording medium with excellent conversion characteristics can be obtained. It can be said that this invention can produce excellent effects.

Claims (2)

[Claims] (1) Surface roughness R measured using a stylus roughness meter in a method of manufacturing a magnetic recording medium by providing a magnetic layer on a polyester film and then calendering it.
a is 0.015 μm-0.025 μm, Ra does not substantially change before and after calendering, and the number of secondary interference fringes H_2 (pieces/mm^2) measured by multiple interferometry before and after calendering 1. A method for producing a magnetic recording medium, characterized in that a polyester film is used in which the following formula is satisfied: 0.05≦H_2 (after treatment)/H_2 (before treatment)≦0.
5...(1) (2) The method for producing a magnetic recording medium according to claim 1, wherein the polyester film is a film containing precipitated particles containing calcium and phosphorus elements and/or barium sulfate particles.