KR100297388B1 - Magnetic recording medium - Google Patents

Abstract

The present invention discloses a magnetic recording medium capable of high-density magnetic recording as well as being excellent in electron conversion characteristics, running properties, and light transmission suppression. The magnetic recording medium according to the present invention includes a base film layer, a metal deposition layer formed of any one or more metals selected from the group consisting of aluminum, copper, chromium and titanium, formed on any one or more surfaces of the base film, and the metal. It is formed on top of the deposition layer and comprises an easy-adhesion layer made of at least one selected from the group consisting of a polyester resin or a silicone resin and a magnetic layer formed on an upper part of the easy-adhesive layer and containing a magnetic body and a binder. .

Description

Magnetic recording medium

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium, and more particularly, to a magnetic recording medium capable of thinning due to excellent electronic conversion characteristics and running characteristics, and excellent light transmittance.

Magnetic recording media such as magnetic tapes and floppy disks are widely used in audio, video and computer fields. In general, a magnetic recording medium is manufactured by applying a magnetic paint obtained by dispersing a magnetic material together with a binder (binder) in a solvent and applying it on a nonmagnetic substrate to form a magnetic layer.

Recently, in accordance with the miniaturization of information and communication-related media, it is required to increase the fineness of the magnetic material, to increase the filling rate, and to super-smooth the magnetic recording medium to improve the high-density recording and electronic conversion characteristics in the magnetic recording medium. Magnetic recording media are required.

Meanwhile, in the VHS video system, a method of detecting the start and end of a cassette tape by the light transmittance of the tape is used. In other words, a magnetic tape is not applied to the beginning and the end of the video cassette tape for VHS, so that a leader tape that transmits light almost 100% is provided. When the leader tape travels in front of the sensor, light is transmitted and light is received by the sensor. The sensor then issues an output signal to stop the video drive motor so that the video tape automatically stops. Therefore, the portion where the magnetic layer is formed in the video tape should not transmit light above the reference value. If a part of the magnetic layer is peeled off or the thickness of the magnetic layer is too small, and there is a defect in the part where the magnetic layer is formed, the sensor receives light above the reference value even when the part where the magnetic layer is formed is traveling in front of the sensor. The video tape being used causes a freezing malfunction.

In order to solve this problem, a method of using a black magnetic material such as chromium dioxide or magnetite, a method of using a colorant such as carbon black mixed with a magnetic material, or adjusting the thickness of the magnetic layer to about 2 to 4 μm when forming a magnetic layer of a video tape A method has been proposed.

However, these methods have practical problems. That is, since the black magnetic material is expensive, the economic efficiency is low, and the filling rate of the magnetic material is lowered due to the addition of carbon black having a low specific gravity, and the economic thickness is low because the coating thickness of the magnetic layer should be thick. Can be mentioned. In addition, there is a problem that the purity of the magnetic layer is lowered, making high density recording and large capacity difficult.

Accordingly, the present invention has been made in an effort to provide a magnetic recording medium capable of high-density magnetic recording as well as being excellent in electron conversion characteristics, running performance, and light transmission suppression.

1 is a conceptual diagram of an apparatus used to measure the surface resistance of a magnetic recording medium (magnetic tape).

The present invention in order to achieve the technical problem of the present invention; A metal deposition layer formed on at least one surface of the base film and made of at least one metal selected from the group consisting of aluminum, copper, chromium and titanium; An easy adhesion layer formed on the metal deposition layer and made of at least one selected from the group consisting of a polyester resin or a silicone resin; And a magnetic layer formed on the adhesive layer and containing a magnetic material and a binder.

In the magnetic recording medium according to the present invention, the metal deposition layer preferably has a thickness of 400 to 500 kPa. If the thickness of the metal deposition layer is less than 400 GPa, there is a problem that the light transmission suppression function and the function as the conductive layer are deteriorated. If the metal deposition layer is more than 500 GPa, cracks are easily generated in the metal deposition layer and the metal deposition layer is easily peeled off.

In the magnetic recording medium according to the present invention, the thickness of the easily adhesive layer is preferably 0.2 to 0.5 mu m. If the thickness of the easily adhesive layer is less than 0.2 μm, there is a problem that the possibility of separating the metal deposition layer and the magnetic layer increases, and if it exceeds 0.5 μm, there is a problem in driving durability under high temperature and high humidity environment.

In the magnetic recording medium according to the present invention, the magnetic material is γ-Fe ₂ O ₃ , Fe ₃ O ₄ , Co containing γ-Fe ₂ O ₃ , Co containing Fe ₃ O ₄ , FeO _x , Co containing FeO _x , CrO At least one selected from the group consisting of ₂ , α-Fe, and Ba-Fe is preferable.

In the magnetic recording medium according to the present invention, the magnetic material preferably has an average particle diameter of 0.005 to 1 mu m, an axial ratio of 1 to 50, and a specific surface area of 1 to 70 m 2 / g.

In the magnetic recording medium according to the present invention, the binder is a thermoplastic resin having an average molecular weight of 10,000 to 300,000, a thermosetting resin having an average molecular weight of 200,000 or less in the coating liquid state and having an infinite molecular weight after curing, and in the coating liquid state. It is preferable that the average molecular weight is 200,000 or less, and at least one selected from the group consisting of reactive resins whose molecular weight becomes infinite by chemical reaction.

The binder may have a carboxyl group, a sulfonic acid group, a phosphoric acid group, a sulfuric acid group, or the like as a functional group.

In the magnetic recording medium according to the present invention, the magnetic layer may include other additives in addition to the magnetic material and the binder. As said additive, a dispersing agent, surfactant, a lubricating agent, an abrasive | polishing agent, a hardening | curing agent, etc. are mentioned, The content should just be a normal level.

As the surfactant, fatty acids, alcohols, esters, alkali metals, and the like are used. As lubricants, inorganic powders, resin powders, fatty acids having 10 to 20 carbon atoms, alcohols having 3 to 12 carbon atoms and fatty acid esters may be used. Can be.

As the abrasive, an alumina, chromium oxide, iron oxide or titanium dioxide having an Mohs hardness of 6 or more and an average particle diameter of 0.05 to 5 μm may be used. The antistatic agent has an average particle diameter of 5 to 1000 nm and a nitrogen adsorption specific surface area of 1 to 1. Carbon black, electroconductive powder, etc. which are 1500 m <2> / g are used.

Meanwhile, as the curing agent, polyisocyanates having an average molecular weight of 100 to 20,000 may be used.

Hereinafter, the manufacturing method of the magnetic recording medium according to the present invention will be described in detail.

In addition to the magnetic body and the binder, various additives including colorants, lubricants, abrasives, antistatic agents, and the like are mixed with the solvent, and then dispersed and filtered to prepare a composition for forming a magnetic layer. In this case, as the solvent, ketone-based, alcohol-based, ester-based, aromatic hydrocarbon-based, and chlorinated hydrocarbon-based solvents may be used. Subsequently, the composition is applied to a base film on which a metal deposition layer on which aluminum, copper, chromium or titanium is deposited, and an easily bonding layer composed of a resin such as a polyester resin or a silicone resin are formed in turn, followed by self-orientation and drying. do. When the drying is completed, the calendar, curing and slitting processes are sequentially performed to complete the magnetic recording medium.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the scope of the present invention is not limited to the following Examples. Performance evaluation of the film produced in the following Examples was carried out by the following method.

(1) electronic characteristics

JVC's VHS reference tape VRT-2 was used to evaluate the relative RF output of 4.2 MHz in VHS normal mode.

(2) light transmittance

The light transmittance of the tape was evaluated using the traveling light transmittance measuring instrument of JVC, with the running speed of the tape being 3.3 cm / s.

(3) runability

The tape was subjected to environmental treatment for 72 hours under conditions of a temperature of 60 ° C. and a relative humidity of 80%, and then running performance was measured using a tape running tester (TBT-3000) manufactured by Yokohama Systems, Japan. The tape was subjected to a running speed of 3.3 cm / s, a pull-out force of 30 g, and a contact angle of 180 degrees at room temperature, and a burnishing tape coated with alumina particles uniformly on a head drum for VHS having a diameter of 62Φ was rotated at 40 rpm for 1 hour. By running for a while, the degree of change in the winding tension was observed to evaluate the runability as follows.

When there is little change of winding tension: ◎

When the change in winding tension is within 3% of the total size: ○

When the change in winding tension is 3 to 10% of the total size: △

When the change in winding tension is more than 10% of the total size: ×

When not traveling: ××

(4) adhesion

The adhesive force of the tape was evaluated by attaching the splicing tape to 5 cm of the specimen slits to be 0.5 inches wide and 10 cm long, and then reading the load when the coating film was separated while tensioning with a tensioner.

(5) surface resistance

As shown in FIG. 1, two copper rods obtained by dividing a cylindrical copper rod having a radius of 10 cm into four parts were placed at a certain distance from each other, and a tape having a constant length and width was placed thereon. At this time, by hanging the weight on both ends of the tape was hung in the longitudinal direction of 5N / mm ² , the anode and the cathode was put on the copper rod, respectively, and the electrical resistance between the positive electrode was measured to measure the surface resistance of the tape.

Example 1

Three types of compositions each having the following composition were prepared.

<First composition>:

Co-containing Fe ₃ O ₄ magnetic material (nitrogen adsorption specific surface area 35 m 2 / g, powder Hc 720 Oe, Fe ⁺² content 17% by weight; hereinafter referred to as "magnetic body A") 100.0 g

Vinyl chloride resin (MR110, Nippon Zeon) 10.0 g

Alumina (AKP50, Sumitomosa, Japan) 2.0g

Iron oxide (α-Fe ₂ O ₃ ) (Bayferrox, Germany bayer) 4.0g

Carbon Black (MA100, Mitsubishi Corporation, Japan) 3.0g

53.5 g of methyl ethyl ketone

Cyclohexanone 61.8 g

<Second composition>:

Polyurethane resin (KU2010, Dongyang Spinning Yarn, Japan) 6.7g

Myristic acid 2.0g

Butyl stearate 1.0 g

Cyclohexanone 7.8g

29.5 g of methyl ethyl ketone

Toluene 29.5g

<Third composition>:

3.0 g of polyisocyanate (D103H, Takeda Japan)

1.7 g of methyl ethyl ketone

Toluene 1.7g

First, the first composition was placed in a kneader and sufficiently dispersed, and then the second composition was further added and dispersed. Next, the 3rd composition was further added just before apply | coating to the following base film, and it fully disperse | distributed and mixed. The mixed composition thus prepared was uniformly applied on top of the base film on which the metal was deposited and easily adhered to form a magnetic layer having a thickness of 1.5 μm. The base film is formed of a deposition layer of aluminum or copper having a thickness of 400 to 500 mm and an easily bonding layer made of a polyester or silicone resin having a thickness of 0.2 to 0.5 µm to a 14 µm thick PET film.

Subsequently, the base film on which the magnetic layer was formed was self-oriented at 5000 gauss, and then hot air dried at 115 ° C. for 10 seconds or more. Subsequently, calendering was carried out under conditions of a temperature of 110 ° C. and a linear pressure of 300 kg / cm, sufficiently cured at 60 ° C. for 24 hours, and slitting to a width of 0.5 inches to complete the magnetic tape.

Example 2

The first composition using Co ₃ containing Fe ₃ O ₄ (hereinafter referred to as “magnetic body B”) having a nitrogen adsorption specific surface area of 45 m 2 / g, powder Hc of 800 Oe, and Fe ^{+ 2} content of 5% by weight instead of the magnetic material A A magnetic tape was prepared in the same manner as in Example 1 except that was prepared.

Comparative Example 1

Except for using a conventional PET film without both the metal deposition layer and the easily-adhesive layer as a base film, and increasing the addition amount of carbon black to 7.0g in order to control the light transmittance of the film during the preparation of the first composition The magnetic tape was prepared in the same manner as in Example 1.

Comparative Example 2

Example 1 except for using a conventional PET film without a metal deposition layer and an easily-adhesive layer as a base film, and using magnetic material B instead of magnetic material A and increasing the amount of carbon black added to 7.0 g when preparing the first composition. Magnetic tape was prepared according to the same method as described above.

Comparative Example 3

The magnetic tape was prepared in the same manner as in Example 1, except that the PET film having only the metal deposition layer without the adhesive layer was formed as the base film, and the addition amount of carbon black was increased to 7.0 g when preparing the first composition. Was prepared.

Comparative Example 4

According to the same method as in Example 1, except that a PET film having only an adhesive layer and no metal deposition layer was used as the base film, and the amount of carbon black added was increased to 7.0 g when preparing the first composition. Magnetic tape was prepared.

The electronic properties, light transmittance, runability, adhesive force and surface resistance of the magnetic tapes prepared according to Examples 1 to 2 and Comparative Examples 1 to 4 were measured and shown in Table 1 below.

division RF-OUT (dB) Light transmittance (%) Run Adhesive strength (g) Surface resistance (Ω) Example 1 1.6 0.5 ◎ More than 100 2 × 10 ⁹ Example 2 2.4 0.9 ○ ~ ◎ More than 100 5 × 10 ⁹ Comparative Example 1 1.0 4.3 ◎ 60 2 × 10 ⁸ Comparative Example 2 1.6 14.8 × 40 8 × 10 ⁸ Comparative Example 3 1.3 0.6 ◎ 3 1 × 10 ⁵ or less Comparative Example 4 1.4 1.4 ◎ More than 100 2 × 10 ⁸

Referring to Table 1, in the case of the magnetic tape that does not correspond to the claims of the present invention of Comparative Examples 1 to 4 it can be seen that any one or more of the physical properties that the magnetic tape is to be very poor. That is, in the case of Comparative Examples 1 and 2, since the magnetic layer is formed on the conventional PET film, it is understood that the light transmittance is very high and the probability of malfunction is high. In particular, in the case of Comparative Example 2 using the magnetic body B, the electron conversion characteristics are improved, but the Fe ²⁺ ion content in the magnetic body is lowered, the higher the light transmittance, it can be seen that the probability of malfunction is higher. The same applies to the case where the magnetic layer is formed on the PET film in which only the easily adhesive layer is formed as in Comparative Example 4. In the case of Comparative Example 3, since the magnetic layer is formed on the PET film on which only the metal deposition layer is formed, the light transmittance is very low, and thus the probability of malfunction is lowered, but the adhesion is very poor, resulting in very poor driving durability. .

On the other hand, as described in Examples 1 to 2 corresponding to the claims of the present invention, the magnetic tape prepared by forming a magnetic layer on the base film on which the metal deposition layer and the easily-adhesive layer are formed is excellent in electronic properties, runability, and adhesion. The light transmittance is less than 1%, there is no fear of malfunction and it can be seen that the surface resistance is stabilized. In addition, the magnetic tapes of Examples 1 to 2 significantly improve the electronic properties because the metal deposition layer significantly improves the light transmittance and the electrical resistance, thereby reducing the carbon black content used as the antistatic agent and increasing the magnetic content. You can also improve.

As described above, the magnetic recording medium according to the present invention, while reducing the amount of additives such as carbon black, is excellent in running and light transmission suppression and has a low surface resistance, thereby increasing the purity of the magnetic layer to enable stable high output thin film. Do. In addition, a back coating for coating carbon black on the opposite side of the base film on which the magnetic coating film is formed is not necessary, and high density recording is possible without additional additives such as an additional abrasive.

Claims (6)

A base film layer; A metal deposition layer formed on at least one surface of the base film and made of at least one metal selected from the group consisting of aluminum, copper, chromium and titanium; An easy adhesion layer formed on the metal deposition layer and made of at least one selected from the group consisting of a polyester resin or a silicone resin; And And a magnetic layer formed on the adhesive layer and containing a magnetic material and a binder. 2. The magnetic recording medium of claim 1, wherein the metal deposition layer has a thickness of 400 to 500 mW. The magnetic recording medium according to claim 1 or 2, wherein the thickness of the easily adhesive layer is 0.2 to 0.5 mu m. The magnetic material of claim 1 or 2, wherein the magnetic material is selected from the group consisting of γ-Fe2O3, Fe3O4, Co-containing γ-Fe2O3, Co-containing Fe3O4, FeOx, Co-containing FeOx, CrO2, α-Fe, and Ba-Fe. Magnetic recording medium, characterized in that any one or more. The magnetic recording medium of claim 4, wherein the magnetic material has an average particle diameter of 0.005 to 1 mu m, an axial ratio of 1 to 50, and a specific surface area of 1 to 70 m 2 / g. The method according to claim 1 or 2, wherein the binder is a thermoplastic resin having an average molecular weight of 10,000 to 300,000, a thermosetting resin having an average molecular weight of 200,000 or less in the coating liquid state and having an infinite molecular weight after curing, and in the coating liquid state. A magnetic recording medium having an average molecular weight of 200,000 or less and at least one selected from the group consisting of reactive resins whose molecular weight becomes infinite by chemical reaction.