JPH076345A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium excellent in durability and contact with a head by regulating the stiffness of the nonmagnetic substrate of a magnetic recording medium with a magnetic coating film on the nonmagnetic substrate and the stiffness of the entire magnetic recording medium to a prescribed value each. CONSTITUTION:The stiffness of the nonmagnetic substrate of a magnetic recording medium with a magnetic coating film on the nonmagnetic substrate is regulated to 15 to <22 and the stiffness of the entire magnetic recording medium is regulated to 50 to <60 to improve contact with a head. The film energy of the magnetic coating film is regulated to 55-7kg.mm/mm<2> to improve durability. Since this method improves both durability and contact with a head unlike the conventional method, the objective magnetic recording medium performing high quality recording and reproduction even in a severer environment is obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium such as a cassette tape, a video tape and a magnetic disk.

[0002]

2. Description of the Related Art A magnetic recording medium such as a cassette tape, a video tape or a magnetic disk is composed of a non-magnetic support such as a polyester film and a magnetic layer formed on the non-magnetic support. The magnetic layer is generally formed by coating a non-magnetic support with a magnetic paint prepared by dispersing and kneading a ferromagnetic powder, a binder, a dispersant, a lubricant, etc. in an organic solvent, or by applying a ferromagnetic metal by vacuum deposition or the like. It is formed on the non-magnetic support by directly applying it on the non-magnetic support.

By the way, it is known that the stronger the strength of the magnetic layer is, the harder the magnetic recording medium is to fall off of the magnetic powder and the like, and the better the durability of the magnetic recording medium is. However, on the other hand, if the strength of the magnetic layer is too strong, the stiffness of the entire magnetic recording medium becomes too large, and the contactability of the reproducing (or recording / reproducing) head deteriorates, resulting in sufficient reproduction (or recording / reproducing) of information. Will not be possible. Therefore, in the conventional magnetic recording medium, it is difficult to improve both the durability and the contact property of the head, and it is the current situation that one of them is sacrificed to improve the other.

[0004]

However, since the magnetic recording medium is used under various environments, there is no problem in durability even if it is run or rotated at high speed, for example.
Moreover, the magnetic recording medium is excellent in both durability and head contactability, such that stable contactability can be obtained even with a head whose protrusion amount has decreased due to wear due to long-term use. Is desirable. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a magnetic recording medium having excellent characteristics in both durability and head contactability.

[0005]

In order to achieve the above object, the present invention provides a magnetic recording medium having a magnetic coating film on a non-magnetic support, wherein the stiffness of the non-magnetic support is 15 or more and 22 or more. And the stiffness of the entire magnetic recording medium is 50 or more and less than 60, and the coating energy of the magnetic coating film is 55 kg · mm / mm ² or more and 75 kg · m or more.
It is characterized in that it is set to m / mm ² or less.

In the conventional magnetic recording medium, satisfactory performance can be obtained at the same time in terms of both the durability as seen in the head clog during running and the head contact property which affects the electromagnetic conversion characteristics. There wasn't. In order to confirm this, the stiffness of the non-magnetic support is 15
For a plurality of commercially available magnetic tapes having a size of 22 or more,
When the physical and mechanical properties were measured, a distribution as shown in FIG. 1 was found in the relationship between the coating energy of the magnetic coating and the stiffness of the entire magnetic recording medium.

As is apparent from this distribution, the commercially available magnetic tapes have a coating film energy of the magnetic coating film of 30 or more and 55 or less (kg · mm / mm ² ), and Group A having a stiffness of 50 or more and 60 or less, and coating energy of the magnetic coating film is 55 or more and 75 or more.
Below (kg · mm / mm ² ), with the group B in which the stiffness of the entire magnetic recording medium is 60 or more and 75 or less,
Divided into two big groups. When the durability and the head contact property of the plurality of commercially available magnetic tapes were examined, each of the magnetic tapes belonging to Group A had excellent head contact property but poor durability, and conversely, The magnetic tapes belonging to group B were excellent in durability but poor in head contact property.

Therefore, a plurality of patterns of magnetic coating films in which the coating energy of the magnetic coating film is set to various values within a wide range including the distribution range of the above-mentioned groups A and B have a stiffness of 15 or more and less than 22. A plurality of patterns of magnetic recording media were prepared, each of which was formed on a magnetic support, and the overall stiffness was set to various values within a wide range including the distribution range of the groups A and B. And
When the durability and the head contact property of the magnetic recording media having a plurality of patterns were examined, it was found that both the durability and the head contact property were excellent within the range of the coating energy and the overall stiffness of the present invention. It was That is, in the present invention, by setting the physical and mechanical properties of the non-magnetic support and the magnetic coating film in appropriate ranges, it is possible to improve both the durability and the head contact property of the obtained magnetic recording medium. it can.

In the present specification, the coating film energy is, as shown in FIG. 2, an S-S curve 1 showing strength characteristics when both ends of the entire magnetic recording medium are pulled, and a non-magnetic support alone. It is a value obtained by dividing the area of an oblique line portion S drawn by 10% elongation by the sample cross-sectional area by drawing the S-S curve 3 showing the strength characteristics when both ends are pulled. The coating film energy of the magnetic coating film of the magnetic recording medium according to the present invention is preferably 55 or more and 75 or less (kg · mm / mm ² ). If the coating energy of the magnetic coating film is less than 55 (kg · mm / mm ² ), durability will be insufficient, and conversely if the coating energy of the magnetic coating film will be greater than 75 (kg · mm / mm ² ). However, the rigidity of the magnetic coating film becomes too strong and the head contact property deteriorates.

In the present specification, the stiffness means that the width of the test medium is 6.2 as shown in FIGS. 3 (a) and 3 (b).
A magnetic tape 5 having a length of 5 (mm) and a length of 140 to 160 (mm) is formed, and a loop having a length of 100 (mm) is formed with the magnetic layer surface facing outside, and the loop is set in the holder 7. It is a value obtained by measuring the strain amount of the strain gauge 11 one minute after the loop-shaped magnetic tape 5 was pressed against the detection unit 9 while holding d = 20 (mm). At this time, the width of the detection portion of the strain gauge that contacts the loop-shaped magnetic tape 5 (test medium) is 4 (mm). As a result of repeated studies by the present inventors, the stiffness of the entire magnetic recording medium is 5
It has been found that 0 or more and less than 60 is suitable. If the stiffness of the entire magnetic recording medium is less than 50, mechanical strength characteristics such as tape damage cannot be sufficiently satisfied, and conversely, if the stiffness of the entire magnetic recording medium is 60 or more,
The rigidity of the magnetic recording medium becomes too strong and the head contact property deteriorates.

In the magnetic recording medium according to the present invention, a non-magnetic support, a magnetic powder mixed in a magnetic layer, a binder, and optionally a dispersant, an abrasive, an antistatic agent, an anticorrosive agent. Alternatively, conventionally known solvents can be applied to the solvent used for preparing the magnetic coating material in the coating type magnetic recording medium, and the solvent is not limited at all. Further, as the material of the non-magnetic support, conventionally known materials generally used for this type of magnetic recording medium can be used. For example, polyesters such as polyethylene terephthalate and polyethylene naphthalate,
Polyolefins such as polyethylene and polypropylene,
Cellulose triacerate, cellulose diacerate, cellulose derivatives such as cellulose acetate butyrate, polyvinyl chloride, vinyl resins such as polyvinylidene chloride, polycarbonate, polyimide, polyamide, plastics such as polyamide-imide, paper, aluminum,
Examples include metals such as copper, light alloys such as aluminum alloys and titanium alloys, ceramics, and single crystal silicon.

The non-magnetic support made of such a material may be in the form of a film, tape, sheet, disk, card, drum or the like. Further, as the magnetic powder, ferromagnetic iron oxide particles, ferromagnetic chromium dioxide,
Examples include ferromagnetic alloy powder and iron nitride. As the binder, vinyl chloride-vinyl acetate copolymer, vinyl chloride-
Vinyl acetate-vinyl alcohol copolymer, vinyl chloride-
Vinyl acetate-maleic acid copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer, acrylic ester-vinylidene chloride copolymer, methacrylic acid-vinylidene chloride Copolymer, methacrylic acid ester-styrene copolymer, thermoplastic polyurethane resin, phenoxy resin, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, acrylonitrile-butadiene-methacrylic acid copolymer , Polyvinyl butyral, cellulose derivative, styrene-butadiene copolymer, polyester resin, phenol resin, epoxy resin, thermosetting polyurethane resin, urea resin, melamine resin, alkyd resin,
Urea-formaldehyde resin, a mixture thereof, or the like can be used.

Among these, polyurethane resins, polyester resins, acrylonitrile-butadiene copolymers, etc., which are said to impart flexibility, and cellulose derivatives, phenol resins, epoxy resins, etc., which are said to impart rigidity are preferable. These may be those in which an isocyanate compound is used as a cross-linking agent to further improve durability, or an appropriate polar group may be introduced.

As the solvent for adjusting the magnetic coating material, ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, glycol acetate monoethyl ester, etc. Ester solvent, glycol ether solvent such as glycol monoethyl ether and dioxane, aromatic hydrocarbon solvent such as benzene, toluene and xylene, methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, ethylene chlorohydrin, dichlorobenzene. And other organic chlorine compound-based solvents. Furthermore, the other surface of the above-mentioned non-magnetic support,
That is, a back coat layer may be provided on the surface on which the magnetic layer is not formed, if necessary. As the non-magnetic powder, binder, solvent and the like used in this non-magnetic layer (back coat layer), conventionally known materials can be used.

[0015]

According to the present invention, in the magnetic recording medium in which the stiffness of the non-magnetic support is 15 or more and less than 22, if the stiffness of the entire magnetic recording medium is 50 or more and less than 60, the head contact property becomes good, and , The coating energy of the magnetic coating is 55 or more and 75 or less (kg · mm / m
If it is m ² ), the durability will be good. In this way
Both the durability and the head contact property, which have been difficult to achieve in the past, can be achieved.

[0016]

EXAMPLES Preferred examples of the present invention will be described below based on experimental examples. In the examples, "part" is "part by weight"
Indicates.

[Examples 1 to 4 and Comparative Examples 1 to 8] First, magnetic coating compositions for forming a magnetic layer were prepared according to the following compositions. Co deposition γ-Fe ₂ O ₃ (specific surface area 45 m ² / g): 1
00 parts Nitrocellulose <NC> (Asahi Kasei Corp., trade name NC
-1 / 2H), vinyl chloride-vinyl acetate-vinyl alcohol copolymer <PVC> (manufactured by U.C.C., trade name Vinylite VAGH) and polyurethane resin <PU>.
(Nippon Polyurethane Co., product name N-2304): 2 in total
0 parts (however, the numbers of parts of <NC>, <PVC>, and <PU> in Examples 1 to 4 and Comparative Examples 1 to 8 are as described in [Table 1]) Butyl stearate: 1 part α-A1 ₂ O ₃ (Sumitomo Kasei, trade name AKP-30):
3 parts Polyisocyanate (manufactured by Nippon Polyurethane Company, trade name Coronate L): 6 parts Methyl ethyl ketone: 70 parts Methyl isobutyl ketone: 70 parts Toluene: 70 parts

The above-mentioned magnetic coating composition was crushed with a ball mill.
Mixed for hours. This was applied onto two types of polyethylene terephthalate films having a thickness of 11.5 μm and stiffnesses of 16 and 21 so that the film thickness after drying would be 4 μm, and cut into 1/2 inch width. I made a videotape. The durability and head contact property of each of the video tapes prepared in these examples and comparative examples were measured. Each measuring method is as follows. First, the durability was measured by the following two methods. Recording a video signal 4.2MH _Z in still characteristics videotape the reproduction output was expressed as the time in minutes until attenuated to 50%. A good value is 120 minutes or longer. Powder falling The amount of powder falling onto the head drum, guide, etc. after 100 times of shuttle running for 60 minutes was visually observed and evaluated by the deduction method (the larger the absolute value, the more powder falling). A value of 2.0 or less is a good value. The head contact property was measured by the following two methods. Output characteristics A sine wave signal of 4 MHz was recorded on each video tape with the optimum recording current for the reference tape, and the reproduction output at that frequency was obtained. In this experiment, the output characteristics of the video tape of Example 4 are shown as relative values with reference (0 dB). Low head RF characteristics Recording / playback head projection amount is sufficiently worn due to running of the video tape. After recording 4.2 MHz video signal on the video magnetic tape using the head, this playback output waveform Was visually observed with an oscilloscope, and the uniformity of the output waveform was evaluated by the symbol method (← good ○, △, ▲ → bad). Only "○" is a good value. The results are shown in [Table 1].

[0019]

[Table 1]

FIG. 4 shows the relationship between the coating energy of the magnetic coating film and the stiffness of the entire magnetic recording medium in each of the magnetic recording media of Examples 1 to 4 and Comparative Examples 1 to 8. It is a correlation diagram. In FIG. 4, black circles indicate the magnetic recording media of Examples 1 to 4, and white circles indicate the magnetic recording media of Comparative Examples 1 to 8. Also, the shaded area in FIG. 4 indicates the selection range of the coating energy of the magnetic coating and the stiffness of the entire magnetic recording medium defined in the present invention.

From Table 1, Examples 1 to 4 (● 1 in FIG. 4) satisfy both the coating energy of the magnetic coating film and the stiffness of the entire magnetic recording medium satisfying the conditions specified in the present invention.
(See ~ 4)), still characteristics, powder drop, output characteristics, R
It can be seen that all of the F contact characteristics are excellent, and both the characteristics of durability and head contactability have reached a level that can be satisfied at the same time. On the other hand, Comparative Examples 1 to 3 (see ◯ 1 to ◯ 3 in FIG. 4) in which both the coating energy of the magnetic coating and the stiffness of the entire magnetic recording medium do not satisfy the conditions specified in the present invention, In addition, either Comparative Example 7 (see ◯ 7 in FIG. 4), Comparative Example 8 (see ◯ 8 in FIG. 4), or either the coating energy of the magnetic coating film or the stiffness of the entire magnetic recording medium is the present invention. In Comparative Examples 4 to 6 (see ◯ 4 to ◯ 6 in FIG. 4) that do not satisfy the specified conditions, neither of the characteristics of durability and head contactability is satisfied at the same time.

[0022]

As is apparent from the above description, according to the present invention, it is possible to provide a magnetic recording medium excellent in both durability and head contact property. Therefore, it is possible to provide a magnetic recording medium that performs high-quality recording / reproduction even in a more severe environment.

[Brief description of drawings]

FIG. 1 is a correlation diagram showing the relationship between the coating energy of a magnetic coating on a plurality of commercially available magnetic tapes having a non-magnetic support having a stiffness of 15 or more and less than 22 and the stiffness of the entire magnetic recording medium.

FIG. 2 is an explanatory diagram showing the definition of coating film energy.

3A and 3B are explanatory diagrams showing the definition of stiffness.

FIG. 4 is a correlation diagram showing the relationship between the coating energy of the magnetic coating film of each magnetic recording medium of Examples 1 to 4 and Comparative Examples 1 to 8 and the stiffness of the entire magnetic recording medium.

[Explanation of symbols]

 1 S-S curve of the whole magnetic recording medium 3 S-S curve of the non-magnetic support 5 Magnetic tape 7 Holder 9 Detection part 11 Strain gauge

Claims (1)

[Claims] 1. A magnetic recording medium having a magnetic coating film on a non-magnetic support, wherein the non-magnetic support has a stiffness of 15 or more and less than 22 and a stiffness of the entire magnetic recording medium of 50 or more and less than 60. And the coating energy of the magnetic coating is 55 kg · mm / mm
A magnetic recording medium characterized by having a value of ² or more and 75 kg · mm / mm ² or less.