KR100231104B1 - Magnetic recording media - Google Patents

Abstract

The present invention relates to a magnetic recording medium. A first polyester film containing carbon black and laminated on one surface of the first polyester film, the second polyester film containing inert particles having an average particle diameter of 0.001 to 1 μm, and the It is laminated | stacked on the other surface of the 1st polyester film, and is apply | coated on the base film containing the 3rd polyester film containing inert particle whose average particle diameter is 0.01-3 micrometers, and the said 2nd polyester film of the said base film. In a magnetic recording medium comprising a magnetic layer, the magnetic recording medium having an adhesive layer whose main component is a polyester-based polyurethane resin is formed between the second polyester film and the magnetic layer is excellent in light blocking property and can malfunction. In addition to being small, the strong adhesion between the magnetic material and the base film allows for long-term storage of records. Neunghada.

Description

Magnetic recording media

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 long-term storage of recordings due to its excellent light blocking property and less possibility of malfunction, as well as strong adhesion between the magnetic material and the base film.

Saturated linear polyester films represented by polyethylene terephthalate have excellent mechanical properties, heat resistance, weather resistance, electrical insulation, chemical resistance, and the like, and are widely used in packaging, photographic films, insulating materials, magnetic recording media, and the like.

In particular, with the increase in the popularity of video tape recorders (VTRs), the demand for video base films is greatly increased. With the progress of science and technology, information and communication media are becoming smaller, and recording density is required for magnetic recording media. In accordance with this trend, the demand for polyester films suitable for use as the base film of magnetic recording media is constantly increasing.

Currently, when employing a VHS system in video, a method of detecting the start and end of a cassette tape by the light transmittance of the tape is used. At the beginning and the end of the tape, a leader tape without a magnetic layer is connected so that light passes through when the leader tape passes through the sensor. In the VHS system, the video tape is automatically stopped in response to the signal output by the light-sensitive sensor.

Therefore, the video tape must be kept at a light transmittance below a certain degree. If the light transmittance is too high, the sensor may mistake the video tape as the leader tape and stop the operation. This malfunction can occur if the tape is defective. For example, when a part of the magnetic layer is peeled off or the thickness of the magnetic layer is thin, more than a certain amount of light passes through the tape, and a malfunction may occur in which the sensor detects the light and stops the video tech in operation.

In order to solve the problem that the sensor detects light, a method of coating the base film with a magnetic material of about 3-5 μm, and mixing a colorant with a magnetic material to block light is proposed. However, according to this method, since the purity of the magnetic material is reduced, and the coating layer must be thick, it is not preferable in terms of cost reduction.

On the other hand, when applying a magnetic body to a polyester film, in order to improve the adhesive force between a film and a magnetic body, the method of adding binder resin, such as an acrylic resin and a polyurethane resin, to a magnetic paint was proposed. However, this method has a disadvantage in that the purity of the magnetic material is lowered and the electronic characteristics are lowered.

The technical problem to be solved by the present invention is to provide a magnetic recording medium having excellent recording integrity by solving the above problems and reducing the possibility of malfunction due to the light blocking property, as well as the strong bonding force between the magnetic material and the film.

Technical problem of the present invention is a first polyester film containing carbon black, laminated on one surface of the first polyester film, and containing an inert particle having an average particle diameter of 0.001 to 1 μm. A base film comprising a second polyester film and a third polyester film laminated on the other side of the first polyester film and containing inert particles having an average particle diameter of 0.01 to 3 μm, and the base film 2. A magnetic recording medium comprising a magnetic layer coated on a polyester film, wherein the adhesive layer of a polyester polyurethane resin whose main component is a polyester polyurethane resin is formed between the second polyester film and the magnetic layer. Is provided.

In particular, the polyester-based polyurethane resin is preferably obtained by copolymerizing a dicarboxylic acid component, a glycol component, a diisocyanate component represented by the following formula (1) and a carboxylic acid glycol component represented by the following formula (2).

Wherein R ₁ , R ₂ and R ₃ each represent an aliphatic hydrocarbon group.

Wherein R represents an aliphatic hydrocarbon group and n and m each represent an integer between 1 and 5.

The polyester resin is a polycondensation of an aromatic dicarboxylic acid component and a glycol component, and there is no particular limitation as long as it is usually used for a base film for magnetic recording media. In particular, it is preferable that the repeating unit consists of ethylene terephthalate or ethylene naphthalate.

In the present invention, the base film is a film composed of second and third polyester resins containing inert particles on both sides of the film made of the first polyester resin containing carbon black and having light blocking properties Is laminated. Here, the size of the inert particles contained in the second polyester film is relatively small compared to the size of the inert particles contained in the third polyester film. This is because the second polyester film is coated with a magnetic material, so the roughness needs to be small, and the third polyester film needs to have a large roughness because a large amount of active activity is required without coating the magnetic material.

There is no particular limitation on the kind of carbon black added to have light blocking properties, and it is preferable to be used as a conventional colorant. For example, there are channel carbon, Fannes carbon, and the like.

Inert particles include inorganic particles or organic particles which are inert to polyester. For example, the inorganic particles include calcium carbonate, dolomite, glass spare, fiberglass, talc, kaolin, mica, silica, barium sulfate, aluminosilicate, alumina, titanium dioxide, and the like, but are not limited thereto. In addition, organic particles insoluble in polyester include a copolymer of a monovinyl compound having one aliphatic unsaturated bond in a molecule and a compound having two or more aliphatic unsaturated bonds in a molecule with a crosslinking agent, a thermosetting phenol resin, a thermosetting epoxy resin, One or two or more kinds of fine powders of thermosetting urea resins, benzoguanamine resins and fluorine-based resins may be used, but are not limited thereto.

In the present invention, the main component of the dispersion liquid for forming the adhesive layer is a water-dispersible polyester-based polyurethane resin, a dicarboxylic acid component, a glycol component, a diisocyanate component composed of a polyurethane component as represented by the formula (1), and It is prepared by copolymerizing the compound represented by the formula (2) containing a hydroxyl group and a carboxyl group.

The dicarboxylic acid component that is one component of the copolymer is aromatic dicarboxylic acid such as terephthalic acid, isophthalic acid, 1,4-naphthalene dicarboxylic acid, 2,5-methyl terephthalic acid, dimethyl isophthalic acid, 1,3- Alicyclic dicarboxylic acids such as cyclopentane dicarboxylic acid, 1,3-cyclohexane dicarboxylic acid, and the like, and aliphatic dicarboxylic acids such as adipic acid, sebacic acid, and the like.

As a glycol component, C2-C8 aliphatic glycol and C6-C12 alicyclic glycol are preferable. For example, ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, 1,2-cyclohexane dimethanol, 1,3 -Cyclohexane dimethanol, 1,4-cyclohexane dimethanol, p-xylene glycol, diethylene glycol, triethylene glycol and the like.

The diisocyanate is as represented by the formula (1). In particular, in the general formula (1), it is preferable that R ₁ , R ₂ and R ₃ are each a methyl group, an ethyl group, a propyl group or a butyl group, and more preferably R ₁ , R ₂ and R ₃ are all methyl groups. In addition, the carboxylic acid glycol component is as represented by the formula (2), it is particularly preferable that R is a methyl group, ethyl group, propyl group or butyl group.

In the present invention, the repeating unit of the polyester-based polyurethane resin consists of a polyester-based component and a polyurethane component. The polyester-based component is formed from dicarboxylic acid and glycol, and the polyurethane component is formed from diisocyanate represented by formula (1) and carboxylic acid glycol component represented by formula (2). In the polyester-based polyurethane resin, the molar ratio of the polyester-based component and the polyurethane component is 90:10 to 10:90, preferably 30:70 to 20:80.

When the resultant obtained by copolymerizing the composition as described above is dispersed in a polar solvent such as water, a dispersion for forming an adhesive layer is prepared. In particular, it is preferable to add surfactant further in preparation of dispersion. Herein, the polyester-based polyurethane resin and the surfactant are preferably 1 to 10% by weight and 0.01 to 0.5% by weight based on the polar solvent, respectively.

In this invention, another additive can be added to a dispersion liquid within the range which does not reduce the adhesive force between a magnetic layer and a base film. For example, antistatic agents, wetting agents, pH adjusting agents, antioxidants, dyes, pigments, slip agents and the like can be added.

Hereinafter, the present invention will be described in detail through the manufacturing process of the magnetic recording medium.

The base film of the magnetic recording medium is produced by co-extruding the second and third polyester resins on both sides of the first polyester resin produced as described below.

In the present invention, in order to manufacture the first polyester resin, first, the polyester resin chip is pulverized, and then kneaded with carbon black to prepare a master polyester resin containing a high concentration of carbon black. Then, the master polyester resin is mixed with the polyester resin not containing carbon black to prepare a first polyester resin containing an appropriate content of carbon black. The content of carbon black is preferably 0.01 to 30% with respect to the polyester resin. When the carbon black content is less than 0.01% by weight, the light blocking effect is insignificant, and when the content of the carbon black exceeds 30% by weight, the difference in physical properties between layers is large, and when the external force is applied to the base film, layer separation may occur.

The second and third polyester resins can be prepared by conventional methods except for the size and content of the inert particles. That is, it can be prepared by adding inert particles of the size and content required during the polycondensation process for producing the polyester resin. Alternatively, as in the manufacturing process of the first polyester resin containing carbon black, the polyester resin chip may be ground and then kneaded with the inert particles.

Specifically, the size of the inert particles contained in the second polyester resin is, respectively, 0.001 to 1 ㎛ average particle diameter. If less than 0.001 μm, this activity is poor, and if more than 1 μm, the surface of the film is roughened, and when the magnetic material is applied, dropout may occur. In addition, the content of the inert particles is preferably 0.001 to 0.5% by weight relative to the polyester resin in the second polyester resin. This is because if the content of the particles is less than 0.001% by weight, this activity is very poor, and if the content of the particles is more than 0.5% by weight, the surface of the film is roughened, making it unsuitable for applying the magnetic material.

The average particle diameter of the size of the inert particle contained in 3rd polyester resin is 0.01-3 micrometers, respectively. If the thickness is less than 0.01 µm, it is difficult to have the required activity in the magnetic recording medium. If the thickness is greater than 3 µm, the surface of the film is too roughened, and the surface irregularities are transferred to the magnetic layer while the magnetic tape is wound, causing dropout. Because it can. In addition, the content of the inert particles is preferably 0.01 to 2.0% by weight relative to the polyester resin in the third polyester resin. This is because when the content of the particles is less than 0.01% by weight, it is difficult to have the diactivity required in the magnetic recording medium, and when the content of the particles exceeds 2.0% by weight, the surface of the film is too rough.

In the present invention, when each of the above-mentioned resins are produced, they are first produced in a multilayer sheet by a coextrusion method. For example, each molten resin is extruded through a multi-manifold die or feed block die so that the first polyester resin is in the middle layer and the second and third polyester resins are in both, and then cooled Solidification produces a multilayer sheet. Then, when longitudinal stretching, lateral stretching, or biaxial stretching, a stretched film is produced. The obtained film is composed of a middle layer serving as a light blocking layer, one outer layer suitable for applying a magnetic substance, and another outer layer having excellent activating properties, and are suitable for use as a base film for magnetic recording media.

In the present invention, the thickness of the first polyester film containing carbon black may be relatively thin compared to the thickness of the film produced according to the conventional method. This is because the carbon black is evenly dispersed, so that light can be evenly shielded over the entire surface even by a thin thickness. That is, in the conventional film, the thickness of the polyester film containing carbon black needs to be 3 micrometers or more, but 0.5 micrometer or more is enough in this invention. When the thickness is less than 0.5 µm, it is difficult to uniformly adjust the thickness, and even a slight thickness variation causes variation in the light blocking effect and the film appears to be stained. Therefore, the minimum thickness needs to be 0.5 µm.

Moreover, the thickness of a 2nd polyester film and a 3rd polyester film also needs to be 1 micrometer or more. This is because when the thickness of the second and third polyester films is less than 1 μm, the surface may be roughened under the influence of the first polyester film layer, which is the middle layer.

As can be seen from the above, if the thickness of the base film for a magnetic recording medium of the present invention is 2.5 탆 without considering the tensile strength, it can have the required light transmittance and activity. Compared to the conventional method, the thickness of the film can be made very thin, and when the magnetic recording medium is manufactured using the film, the tape wound in a case of a certain size can be very long. On the other hand, in order to satisfy the tensile strength of the film required in a magnetic recording medium such as a video tape, the thickness of the film produced according to the present invention needs to be 5 µm or more, preferably 5 to 15 µm.

Meanwhile, according to the present invention, an adhesive layer is formed on the second polyester film of the base film. The coating amount of the adhesive layer is suitably 0.01 to 1.0 g / m 2 based on the polyester-based polyurethane resin solid content. If the coating amount is less than 0.01 g / m 2, the adhesive force is insufficient, and if it is 1.0 g / m 2 or more, a large amount of dispersion should be applied, so that the size of the drying equipment is increased. The adhesive layer is formed by applying the dispersion of the present invention, which can be applied to any of the coextruded unburned sheet, uniaxially or biaxially stretched film. In addition, the coating method includes a method using a roll such as gravure roll, reverse gravure roll, a method using a bar such as a mayer bar, a method using an air knife method, and the like, but is not limited thereto.

When the adhesive layer is formed on the base film through the above steps, a magnetic layer is formed to manufacture a magnetic recording medium. The magnetic layer is formed by applying and drying a conventional magnetic paint prepared on the substrate by dispersing the magnetic substance, the binder, the curing agent and other additives.

Hereinafter, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited to this.

Evaluation of the physical properties of the film in the present invention was performed by the following method.

1) layer thickness

After cutting the film with a microtop, the cross section was observed under an electron microscope.

2) light transmittance

It was measured using Murakami Color Co., Ltd. Clarity Meta T, M-1D.

3) Average particle diameter

Using a scanning microscope, the size of the particles was magnified by 50,000 times, and then the arithmetic average of the values obtained by measuring the particle size of each part by an image analyzer.

4) active activity

Using the TBT-300D (manufactured by Yokohama Systems Research Institute, Japan), a running tester, the tape slitting the film ½ inch in width was 3.3 (cm / sec), the pulling force was 30 g, and the contact angle with the pin was 135 °. The running friction coefficient was measured using the following equation 1 from the winding tension after passing the fixed guide pin (material SUS303) by 90 m.

μK = [2.303 / θ] × log [Ti / To]

Where θ is the contact angle between the film and the guide pin, and Ti and To are the pulling and winding tensions, respectively.

5) wear resistance

After completion of the activity measurement, the degree of the amount of powder deposited on the surface of the fixed guide pin was evaluated by dividing it into four grades as follows.

◎: Almost no powder on guide pin

(Circle): When the powder adheres to 5% or less of guide pin area

(Triangle | delta): When a powder adheres to the area of 10% or less of the guide pin area.

X: When powders are deposited in an area exceeding 10% of the guide pin area

6) Electronic property

A video tape was prepared using a polyester film, and then the size (S / N ratio) of the noise signal to the signal output at a measurement frequency of 4 MHz was measured using a BR6400U VTR deck made by Nippon VIC.

7) Adhesiveness with magnetic layer

An unstretched polyethylene sheet having a thickness of 60 μm was laminated on the surface of the polyester film to which the magnetic layer was applied by a general dry lamination method, and then left at 50 ° C. for 24 hours for aging treatment. After the aging treatment, the laminate was cut into 15 mm pieces, one part of the polyester film and the polyethylene sheet with a magnetic layer was peeled off, and then the force required for T-type peeling at a constant speed was measured using an Instron.

<Example 1>

1) Polyester manufacture

In the reactor, dimethyl terephthalate, ethyleneglycone and calcium acetate (70 and 0.05% by weight relative to dimethyl terephthalate, respectively) were transesterified. After 4 hours, trimethyl phosphate and antimony trioxide (0.06 and 0.04% by weight relative to dimethyl terephthalate) were added to the reactor and polycondensation was carried out for 5 hours to prepare polyester (polyester a).

2) Preparation of Polyester Containing Inorganic Particles

After the transesterification reaction, polyester (each poly) was added in the same manner as in step 1, except that 5 wt% of calcium carbonate having an average particle diameter of 0.5 µm and calcium carbonate having 0.8 µm were further added to dimethyl terephthalate. Esters b and b ') were prepared.

3) Preparation of polyester containing carbon black

The polyester a prepared in the above step was pulverized into a powder having a size of about 1 mm, and then kneaded in a compounder with carbon black to prepare a master polyester (polyester c) containing 50% by weight of carbon black.

4) Manufacture of aqueous dispersion

Dicarboxylic acid component [molar ratio 80/20] consisting of dimethyl terephthalic acid and dimethyl isophthalic acid, glycol component [molar ratio 95/5] consisting of ethylene glycol and diethylene glycol, 5-isocyanate-1-isocyanatemethyl 1,3,3-trimethyl cyclohexane and methylcarboxylic acid ethylene glycol were copolymerized in a molar ratio of 1: 2: 3: 3 to prepare a polyester-based polyurethane resin having a molar ratio of 25:75 of a polyester component and a polyurethane component. Prepared. The obtained polyester-based polyurethane resin and surfactant (Union Carbide, Triron X100) were dispersed in water to prepare an aqueous dispersion containing 1 wt% (solid content) and 0.05 wt%, respectively.

5) film manufacturing

The outer layer resin (A layer) in which polyester a and polyester b were mixed, the middle layer resin (B layer) and poly in which polyester a and polyester c were mixed so that it may become a ratio as shown in Table 1. Another outer layer resin (C layer) in which ester a and polyester b 'were mixed was prepared. An amorphous sheet consisting of three layers was produced through a die provided with a feed block so that the resin for the B layer was located in the outer layer of the B layer in the middle layer. At this time, each resin temperature extruded was 290 ° C. The sheet thus obtained was stretched 3.5 times at 90 ° C. in the longitudinal direction, and then the aqueous dispersion was applied so that the thickness of the coating layer before drying was 5 μm. Subsequently, the film was stretched 4.3 times at 120 ° C. in the transverse direction and then heat-treated at 220 ° C. for 3 seconds, and the film having the adhesive layer containing 0.06 g / m 2 of polyester-based polyurethane resin solid content as shown in Table 1 was shown. Was prepared. The physical properties of the prepared film were measured in the same manner as described above, and the light transmittance, the activity, and the wear resistance were excellent.

Finally, a magnetic tape containing magnetic powder, polyurethane, and nitrocellulose was coated on the A layer of the film to prepare a magnetic tape, and then the S / N ratio was measured. The electronic properties were excellent as 1.4 dB.

<Example 2-7>

As shown in Table 1, except that the content of the carbon black contained in the B layer, and the type, content and size of the inorganic particles contained in the A and C layers are different within the scope of the present invention, Films and magnetic tapes were prepared in the same manner as in Example 1. The properties of the produced film and magnetic tape were evaluated and shown in Table 1. As shown in Table 1, not only the overall light transmittance, the activity, the wear resistance, etc. of the physical properties of the film were excellent, but also the electronic properties were excellent.

<Comparative Example 1-8>

The polyester containing carbon black is the same as the conventional method, except that the method for producing polyester containing inorganic particles is used, and the content and content of the inorganic particles contained in the A and C layers. And the size was kept within the scope of the present invention to produce a film and magnetic tape. The properties of the produced film and magnetic tape were evaluated and shown in Table 1, but at least one of physical properties and electronic properties of the film was poor.

<Comparative Example 9>

As shown in Table 1, the film was prepared in the same manner as shown in Example 1, except that the content of carbon black (40% by weight) in the B layer resin was out of the range of the present invention. The produced film has the advantage that the light transmittance is very low as 1.90%, but there is a problem that the magnetic tape can not be produced by using the drop off of the carbon black layer by layer separation.

<Comparative Example 10>

A magnetic recording medium was produced in the same manner as in Example 1 except that the dispersion liquid for forming the adhesive layer was not applied. The adhesion to the magnetic recording medium produced was measured, which was 68 g, which was weaker than the magnetic recording medium prepared according to the present invention.

<Comparative Example 11>

A magnetic recording medium was produced in the same manner as in Example 1, except that acrylic resin (trade name: AC503, Rohm and Haas Co., Ltd.) was used instead of the polyester-based polyurethane resin as the main component of the dispersion for forming the adhesive layer. The adhesion to the prepared magnetic recording medium was measured, which was 270 g, which was weaker than the magnetic recording medium prepared according to the present invention.

<Comparative Example 12>

A dispersion was prepared in the same manner as in Example 1 except that no diisocyanate was added. In other methods, a magnetic recording medium was produced in the same manner as in Example 1. The adhesion to the prepared magnetic recording medium was measured, which was 270 g, which was weaker than the magnetic recording medium prepared according to the present invention.

As can be seen from the above, the magnetic recording medium of the present invention is excellent in light blocking property as a whole, less likely to malfunction, and also has a strong adhesive force between the magnetic material and the base film, so that the recording can be stored for a long time.

Claims (6)

A first polyester film containing carbon black and having light blocking properties; A second polyester film laminated on one surface of the first polyester film and containing inert particles having an average particle diameter of 0.001 to 1 µm; And A base film laminated on the other surface of the first polyester film and including a third polyester film containing inert particles having an average particle diameter of 0.01 to 3 µm; And A magnetic recording medium comprising a magnetic layer applied on a second polyester film of the base film, Polyester having a main component obtained by copolymerizing a dicarboxylic acid component, a glycol component, the diisocyanate component represented by following formula (1), and the carboxylic acid glycol component represented by following formula (2) between a said 2nd polyester film and a magnetic layer A magnetic recording medium having an adhesive layer formed of a polyurethane resin. <Formula 1>

Wherein R ₁ , R ₂ and R ₃ each represent an aliphatic hydrocarbon group selected from the group consisting of a methyl group, an ethyl group, a propyl group and a butyl group. <Formula 2>

Wherein R represents an aliphatic hydrocarbon group selected from the group consisting of a methyl group, an ethyl group, a propyl group and a butyl group, and the subscripts n and m each represent an integer between 1 and 5. The magnetic recording medium of claim 1, wherein the polyester has at least one major repeating unit selected from the group consisting of ethylene terephthalate and ethylene naphthalate. The magnetic recording medium of claim 1, wherein the carbon black is present in an amount of 0.01 to 30% by weight based on the polyester resin contained in the first polyester film. The magnetic recording medium of claim 1, wherein the content of the inert particles contained in the second polyester film is 0.001 to 0.5% by weight based on the polyester resin contained in the second polyester film. The magnetic recording medium according to claim 1, wherein the content of the inert particles contained in the third polyester film is 0.01 to 2.0 wt% based on the polyester resin contained in the third polyester film. 2. The polyurethane according to claim 1, wherein the polyester-based polyurethane resin is formed from the polyester component (a) formed from the dicarboxylic acid component and the glycol component and the diisocyanate component and the carboxylic acid glycol component. And a molar ratio of component (b) of 90:10 to 10:90.