JPH02137118A - Magnetic recording medium and production thereof - Google Patents

Abstract

PURPOSE:To obviate the generation of blocking, wrinkling and chipping of a biaxially oriented polyester film contg. org. nitrogen and to eliminate the need for a primer coating layer by providing the above-metioned film and a magnetic layer which is provided on the surface thereof and contains <=25wt.% binder component. CONSTITUTION:The magnetic recording medium has the biaxially oriented polyester film and the magnetic layer. The film contains >=1 pieces of the org. nitrogen per 100 pieces of carbon atoms as the measured value by an ESCA method in the surface layer part within at least 10nm from one surface. The magnetic layer is provided on the surface of the film and contains <=25wt.% binder component. The weight % of the binder component in the magnetic layer is based on the state after drying. Namely, this weight % refers to the weight % in the state after the solvent, etc., used at the time of providing the magnetic layer by coating, etc., are removed by drying. The generation of the blocking, wrinkling and chipping of the film is obviated in this way and the need for the primer coating layer is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium and a method for manufacturing the same, and particularly to a magnetic recording medium based on a biaxially oriented polyester film and a method for manufacturing the same.

[Conventional technology]

Conventionally, as magnetic recording media such as magnetic tapes and floppy disks for audio and video, media based on biaxially oriented polyester films and coated with a magnetic layer on at least one side have been known. Here, the magnetic layer is one in which a magnetic material is dispersed in a binder. Corona treatment has been adopted as a general method for adhering this magnetic layer and film.

However, with the recent demand for increasing magnetic recording density, it has become necessary to highly fill the magnetic layer with a magnetic material. Therefore, when the magnetic material is highly filled, the amount of binder in the magnetic layer decreases accordingly, and the adhesion between the film and the magnetic layer deteriorates.

Therefore, the following measures have already been proposed as countermeasures.

(1) Before applying a magnetic layer to a polyester base, an adhesive layer is undercoated (Japanese Patent Publication No. 63-29331).

(2) Provide adhesive properties to the polyester base itself.

(a) An easy-adhesive layer has already been applied to the polyester film (Japanese Patent Application Laid-open No. 43017/1983).

(b) A polyester film contains a polymer that has easy adhesion (Japanese Patent Publication No. 51462/1983).

(C) A polyester film is subjected to corona treatment and an easily adhesive layer is applied (Japanese Patent Publication No. 37824/1983).

[Problem to be solved by the invention]

In the conventional configuration (1), it is necessary to add a new undercoating process, which not only makes the equipment difficult but also increases the manufacturing cost.

Further, the conventional configuration (2) can be manufactured at a lower cost than the configuration (1) by using (a), (b), or (C).

However, in configuration (a) or (C), since an easily adhesive film is used, the coefficient of friction becomes large.

Therefore, in the magnetic layer coating process, the friction with the roller is large (which causes blocking, wrinkles, and scraping of the film).In configuration (b), the film contains a polymer. As a result, a problem arises in that the strength of the film decreases.

An object of the present invention is to provide a magnetic recording medium that can improve blocking, wrinkles, and abrasion of the film during the manufacturing process, does not require an undercoat layer (adhesive layer), and does not cause a decrease in strength, and a method for manufacturing the same. There is a particular thing.

[Means to solve the problem]

(1) The magnetic recording medium according to the present invention includes a biaxially oriented polyester film and a magnetic layer. The film contains a small amount of organic nitrogen (in the surface layer within 10 nm from the surface of one side, as measured by the ESCA method, one or more organic nitrogen atoms per 100 carbon atoms. is provided on the surface of the binder component, and the binder component is
It is 5% by weight or less.

In the present invention, the weight percent of the binder component in the magnetic layer is based on the state after drying. In other words, it refers to the weight percent after removing the solvent and the like used when forming the magnetic layer by coating or the like by drying.

(2) The method for manufacturing a magnetic recording medium according to the present invention includes the following steps.

(a) At least one side of the biaxially oriented polyester film is substantially composed of nitrogen and has an oxygen concentration of 0°1% by volume.
Perform corona discharge treatment at 10 to 100,100 W-/n'f in the following atmosphere.

(b) Providing a magnetic layer containing a binder component of 25% by weight or less on the surface of the film obtained by corona discharge treatment; the weight% of the binder component here is also the same as that of the present invention (1). It has meaning.

＊＊＊＊＊＊＊ In the magnetic recording medium according to the present invention, the biaxially oriented polyester film is a film obtained, for example, as follows. Polycondensing an aromatic dicarboxylic acid such as terephthalic acid, isophthalic acid, or naphthalene-2,6-dicarboxylic acid or an ester thereof with a glycol such as ethylene glycol, diethylene glycol, tetramethylene glycol, neopentyl glycol, etc., Obtain polyester. The obtained polyester was biaxially stretched by a known method and heat treated by a known method to obtain polyester 2.
Obtain an axially oriented film. In addition, more specifically, it is shown in Unexamined-Japanese-Patent No. 54-148869. This film may be blended with small proportions of other resins and may also contain additives consisting of organic or inorganic substances.

The thickness of the polyester biaxially oriented film used is basically not limited, but 4. A range of 150 μm to 150 μm is preferred. Furthermore, the surface roughness of the film, which is preferably in the range of 6 to 75 μm, can be arbitrarily set depending on the diameter and amount of organic particles or inorganic particles used as additives, and stretching conditions.

However, the cutoff of JIS BO601 is 0.25m.
Center line average roughness HRa of m, 0.002 to 0.0
Preferably, the thickness is 40 μm.

In addition, this film has a small
The surface layer within 0 nm contains one or more organic nitrogen atoms per 100 carbon atoms, as measured by the ESCA method.

Here, "at least one side" means "one side or both sides."
This is the meaning of Depending on the purpose of the magnetic recording medium, for example, if a magnetic tape is provided with a magnetic layer on one side, the medium is single-sided, and if a floppy disk is provided with magnetic layers on both sides, it is provided with both sides. Furthermore, even when a magnetic layer is provided on one side, when a back coat is applied to the other side, that side may be included.

ESCA is an abbreviation for soft X-ray excitation photoelectron spectroscopy, which uses the energy spectrum of photoelectrons emitted from atoms in a sample compound by irradiation with soft X-rays to determine the type and chemistry of elements near the surface of the sample. This is a method to analyze the bond state. This method can be used within 10 nm from the surface of the polymer base material because the photoelectron penetration ability in hydrocarbon polymers is small.
In particular, it has the characteristic that the upper part of the extreme surface layer is relatively strong.

Organic nitrogen is a bonded nitrogen identified by the ESCA method, and is represented by an amide group, an amino group, and an imino group. This nitrogen is in the 1s orbit (
N1. ) The binding energy of the spectrum is 398.1-4
It has a peak in the range of 0.01.1 eV. However, the main beak (corresponding to the carbon of the benzene ring) of C1m of polyester is 285. OeV.

Further, the concentration of organic nitrogen is expressed by the number per 100 carbon atoms of the polyester polymer, or the number ratio of nitrogen to carbon (N/C ratio). In the present invention, as measured values by the ESCA method, one or more carbon atoms per 100 carbon atoms,
In other words, it is essential to contain organic nitrogen with an N/C ratio of 0.01 or more, but it is more preferable to have an N/C ratio of 0.015 or more.The upper limit of the nitrogen concentration depends on the required characteristics and Since it differs depending on the purpose, etc., it is difficult to limit it to a specific rule.

However, the N/C ratio is preferably 0.1 or less, and more preferably 0°06
The following is preferable; if this nitrogen concentration is too large, physical properties such as slipperiness and anti-blocking properties will deteriorate. Also,
If the nitrogen concentration becomes less than 0°01 in terms of N/C ratio, the adhesion will be significantly reduced. From the physical properties of the film,
Only in the surface layer within a depth of 10 nm from the surface of the film,
It is preferable that the organic nitrogen is present at a concentration of 0°01 or more in N/C ratio. It is preferable that the depth at which organic nitrogen exists at a concentration of 0.01 or more is as shallow as possible.

When organic nitrogen with a concentration of 0.01 or more in N/C ratio exists at a depth of more than 10 nm from the surface of the film,
The surface layer of the film becomes susceptible to cohesive failure, resulting in poor slipperiness and anti-blocking properties.

In the magnetic recording medium according to the present invention, a magnetic layer containing a dry binder component of 25% by weight or less is provided on the surface of the biaxially oriented polyester film as described above. here,
The magnetic layer consists of a magnetic material and a binder.

There are no particular limitations on the magnetic material, but examples include CO-doped r-FewOs, Ba ferrite, and CrO□.
, Fe metal, etc. are used. These materials can be used alone or in combination. This magnetic material is dispersed in a binder dissolved in a solvent and applied to the surface of the film by a known method.

As the binder, resins such as thermoplastic polyester resin, vinylidene chloride, polyurethane, phenol, acrylonitrile, etc. can be used. These resins can be used alone or in combination.

As the solvent, organic solvents such as methyl ethyl ketone, toluene, cyclohexane, methylene chloride, and xylene can be used depending on the resin used.

Each of these resins may contain a suitable curing agent. Further, when using a magnetic recording medium, a more suitable magnetic recording medium can be realized by adding a lubricant or particles to maintain the running properties of the surface of the magnetic layer, particles to provide light-shielding properties, etc. If such a binder exceeds 25% by weight of the entire magnetic layer after drying, the electromagnetic conversion characteristics will be insufficient. If this value is 25% by weight or less, sufficient electromagnetic conversion characteristics and also sufficient adhesiveness can be obtained. There is no particular lower limit to the content of the binder, but if it is less than 10%, the magnetic layer itself becomes brittle;
% or more is preferable.

The obtained magnetic recording medium does not have an undercoat layer. Furthermore, since this recording medium does not contain a polymer for providing easy adhesion in the film, there is no problem of a decrease in strength.

In the method for manufacturing a magnetic recording medium according to the present invention, first, the medium is substantially made of nitrogen and has an oxygen concentration of 0. The film was subjected to corona discharge treatment (hereinafter referred to as N
(referred to as CD processing). This NCD treatment may be performed immediately after manufacturing the film in the film manufacturing process, or
It may be performed in another step after the manufactured film is once wound up.

Further, in the step of applying the magnetic layer, it may be performed immediately before applying the magnetic layer.

In this NCD processing, the processing atmosphere, particularly the residual oxygen concentration, is an important factor. When the oxygen concentration exceeds 0.1% by volume, there is little improvement in adhesion and hardening, and oral changes are large. Therefore, the oxygen concentration needs to be 0.1% by volume or less, o.

More preferably, it is 5% by volume or less, which results in a film with substantially no change in adhesive properties.

Here, "substantially consisting of nitrogen" means that it may contain trace amounts of other elements that cannot be removed, for example, when nitrogen is produced by liquefaction separation from air.

As the voltage applied to the electrodes during NCD processing, alternating current with any waveform can be used, but voltages of 5 to 70 k
V (peak to peak), frequency 50H
A sine wave of 50 MHz to 50 MHz is preferred. The total electrical energy applied to the film is typically 10 to 100 W-min per m'' of treated film surface, more preferably 15 to 60 W-min.

This electrical energy is applied once or multiple times. For extremely thin substrates, it is preferable to apply the liquid in multiple doses in order to prevent wrinkles and pinholes from forming in the film. The electrical energy to be applied is 1゜W - min / m
If it is less than 10'OW-mi, the magnetic layer cannot be bonded sufficiently, and from the viewpoint of slipperiness and wrinkle prevention,
It is preferably less than n7m''.

It is preferable to perform the NCD treatment between the biaxial stretching process of the film and the film winding process in order to maximize the treatment effect, but it may also be performed after the film is wound up.

After the NCD treatment, a magnetic layer is formed on the surface of the film so that the binder component after drying is 25% by weight or less. The contents of the magnetic layer here are the same as those of the magnetic layer regarding the above-mentioned magnetic recording medium, so a description thereof will be omitted here.

In the step of forming the magnetic layer, the base film is not coated with a conventional adhesive layer, so blocking, wrinkles, and abrasion of the film are improved.

〔Example〕

The results of concrete implementation of the present invention will be explained below.

First, a biaxially oriented polyethylene terephthalate (PET) film having a thickness of 14.5 μm and having a vertically and horizontally balanced type was prepared. This film was subjected to corona discharge treatment in an atmosphere consisting mainly of nitrogen.

On the other hand, γ-Fe2O3 doped with Co as a magnetic material,
A magnetic paint was prepared using polyurethane as a binder, methyl ethyl ketone as a solvent, and a compatible curing agent, lubricant, etc. The obtained magnetic paint was applied onto a biaxially oriented film so that the dry film thickness was 4 μm.

Then, it was dried at 95°C to form a magnetic layer on the biaxially oriented film. Note that because the base film was not coated with an easy-to-adhesive layer like in the past, there was no blocking, wrinkling, or scraping of the film.

In these manufacturing processes, the atmosphere, applied energy,
Samples as shown in Table 1 were obtained by variously changing the oxygen concentration, nitrogen concentration, and binder concentration of the atmosphere. In Table 1, the unit of applied energy is W-min7m"
, oxygen concentration is volume %, and binder concentration is weight %.

For the samples obtained in Table 1, the N/C ratio was measured, and an adhesion test and an electromagnetic conversion property test were conducted.

The results obtained are shown in Table 2. Adhesiveness is the result of a 180° peel test with adhesive tape attached to the magnetic layer. Further, regarding the electromagnetic conversion characteristics, in the 0 table obtained by measuring the S/N ratio, O indicates that the characteristics were sufficient, and × indicates that the characteristics were insufficient.

System Nitrogen in Table 1 is commercially available cylinder nitrogen.

Table 2 Note that the obtained sample did not contain a polymer that has easy adhesion as in the past, so there was no problem of a decrease in film strength.

〔Effect of the invention〕

According to the magnetic recording medium and the manufacturing method thereof according to the present invention,
A magnetic recording medium that does not require an undercoat layer (adhesive layer) and has good adhesiveness between the film and the magnetic layer can be realized. In addition, blocking, wrinkles, and abrasion of the film can be improved in the manufacturing process, and the process of forming an undercoat layer is not necessary.

Claims (2)

[Claims] (1) A biaxially oriented polyester film containing at least one organic nitrogen per 100 carbon atoms in the surface layer within 10 nm from the surface of at least one side, as measured by the ESCA method; In addition, the binder component is 2
A magnetic recording medium comprising: a magnetic layer of 5% by weight or less; (2) At least one side of the biaxially oriented polyester film is substantially composed of nitrogen and has an oxygen concentration of 0.1% by volume.
Performing corona discharge treatment at 10 to 100 W min/m^2 in the following atmosphere, and providing a magnetic layer containing 25% by weight or less of a binder component on the surface of the film obtained by the corona discharge treatment. , A method for manufacturing a magnetic recording medium, comprising: