JP2914774B2 - Magnetic recording media - Google Patents

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 magnetic tape, and more particularly to a magnetic tape having a mechanical strength sufficient for practical use with a total thickness of 15 .mu.m or less.
The present invention relates to a magnetic recording medium such as a tape.

[0002]

2. Description of the Related Art In recent years, in particular, in a magnetic tape for video, etc., the thickness of the magnetic tape is reduced as much as possible in order to make recording and reproducing time as long as possible when incorporated in a cartridge case. Have been tried. However, when the thickness of the magnetic tape is reduced, the mechanical strength of the tape is weakened, and the contact state with the rotating video head is deteriorated during recording and reproduction, and a normal reproduction waveform cannot be obtained. It becomes bad. Also, when recording, reproducing, fast-forwarding, rewinding, or loading and unloading, magnetic tape is used.
The edge of the tape may come into contact with a guide member for restricting the running of the magnetic tape or a flange of the loading post for restricting the magnetic tape, causing buckling or breakage. And wrinkles easily occur. Therefore, when a plastic film such as a polyester film is manufactured, a plastic tape reinforced by stretching in the longitudinal direction or the width direction is used as a base film of the magnetic tape, for example, to reduce the thickness of the magnetic tape. Attempts have been made to reinforce the mechanical strength of the pump.

[0003]

However, those obtained by stretching and strengthening in a balanced manner in the longitudinal and width directions have a Young's modulus at 1% elongation (hereinafter abbreviated as Young's modulus) of 550 to 600 kg in both the longitudinal and width directions. / Mm ² , which has a Young's modulus of 750 to 750 in the longitudinal direction.
850 kg / mm ^2, a 350~430kg / mm ² in the width direction, when the total thickness to 15μm or less, especially when subjected to VHS type and VHS-C type VTR, practically sufficient mechanical strength can not be obtained As a result, the tape stiffness in the state of contact with the magnetic head is reduced, so that the tape cannot be optimized, and a normal envelope waveform and stable running in various running modes cannot be obtained.

[0004]

SUMMARY OF THE INVENTION The present invention has been made based on various studies in view of the above situation, and uses a polyethylene naphthalate film or an aramid film as a base film and a binder for a magnetic layer. glass transition temperature was etc. $ WARNING Do not contain -25 ° C. or more polyurethane resins as component, a glass transition temperature of the magnetic layer 4
The temperature is set to 0 ° C. or higher, and the product Et ³ of the cube of the Young's modulus E and the total thickness t of the magnetic recording medium having a total thickness of 15 μm or less is 1.7 g · mm or more in both the longitudinal direction and the width direction. Thus, even if the total thickness of the magnetic recording medium is 15 μm or less, practically sufficient mechanical strength can be obtained. That is, the present invention is applied to a base film.
When the total thickness having the magnetic layer is 15 μm or less, the Young's modulus E
In any cube of the product Et ³ thickness t in the longitudinal direction and the width direction
Is 1.7 g · mm or more and the glass of the magnetic layer
Magnetic recording characterized by having a transition temperature of 40 ° C. or higher
It relates to a medium.

The base film used in the present invention has a Young's modulus of 650 in both the longitudinal direction and the width direction.
kg / mm ² or more, and the Young's modulus in the width direction is preferably larger than the Young's modulus in the longitudinal direction.
If it is less than kg / mm ² , a magnetic recording medium such as a magnetic tape having sufficient rigidity cannot be obtained even if a magnetic layer is formed thereon, and practically sufficient mechanical strength cannot be obtained. further,
It is advantageous to make the Young's modulus in the width direction larger than the Young's modulus in the longitudinal direction in order to obtain practically sufficient mechanical strength without lowering the rigidity.

Further, since the strength of the conventional polyester film is limited, it is preferable to use a polyethylene naphthalate film or an aramid film having higher strength, and the Young's modulus in the width direction is more than the Young's modulus in the longitudinal direction. By using a polyethylene naphthalate film or an aramid film which is large and has a Young's modulus of 650 kg / mm ² or more in both the longitudinal direction and the width direction, the rigidity is not reduced even if the total thickness is 15 μm or less. A magnetic recording medium having sufficient mechanical strength is obtained. In addition, as the aramid film, both para-type and meta-type are suitably used.

The magnetic layer formed on such a base film has a glass transition temperature of -25 ° C. as a binder resin.
The glass transition temperature of the magnetic layer containing the polyurethane resin described above and cured with a commonly used curing agent is preferably 40 ° C. or higher, and such a magnetic layer is formed on the highly rigid base film. Is formed, the Young's modulus E of the magnetic recording medium and the total thickness t are 3 even if the total thickness is 15 μm or less.
In either the product Et ³ multiply the longitudinal direction and the width direction
The magnetic recording medium can have a rigidity of 1.7 g · mm or more, and has high rigidity and sufficient mechanical strength for practical use.

[0008] Such a polyurethane resin having a glass transition temperature of -25 ° C or higher has a glass transition temperature of -25 ° C or higher by increasing the urethane group concentration or introducing a benzene ring or the like into the molecular chain. For example, UR-8300 (glass transition temperature 23, manufactured by Toyobo Co., Ltd.)
C), manufactured by Nippon Polyurethane Industry Co., Ltd .; N-2309 (glass transition temperature: 26 ° C) and the like are used as suitable ones.

As a curing agent, an isocyanate compound or the like is preferably used.
(Nippon Polyurethane Industry Co., Ltd .; trifunctional low molecular weight isocyanate compound) and the like are preferably used. In addition to these polyurethane resins and curing agents, binder resins generally used for magnetic recording media are preferably used in combination, for example, cellulose resins, vinyl chloride-vinyl acetate copolymers, and polyvinyl butyral. A lahr resin, a polyester resin or the like is used in combination.

The magnetic layer is formed by mixing and dispersing magnetic powder, a binder resin including a polyurethane resin having a glass transition temperature of -25 ° C. or higher, a curing agent such as an isocyanate compound, an organic solvent, and other necessary components. A magnetic paint is prepared by subjecting the magnetic paint to polyethylene naphthalene having a Young's modulus in the longitudinal direction and the width direction of 650 kg / mm ² or more and a Young's modulus in the width direction larger than that in the longitudinal direction. -It is formed by coating and drying on a base film such as a base film or an aramid film.

Here, γ-Fe ₂ O is used as the magnetic powder.
Conventionally known magnetic powders such as metal powders such as ₃ powder, Fe ₃ O ₄ powder, Co-containing γ-Fe ₂ O ₃ powder, Co-containing Fe ₃ O ₄ powder, CrO ₂ powder, and Fe powder are all used. . As the organic solvent, organic solvents generally used for magnetic recording media, such as methyl isobutyl ketone, cyclohexanone, ethyl acetate, tetrahydrofuran, dioxane, toluene, and xylene, are used alone or in combination of two or more. In addition, a filler, a lubricant, an antistatic agent, a dispersant, and the like may be contained in the magnetic layer as needed.

Further, a back coat layer may be further formed on the back surface of the base film on which the magnetic layer is formed. This back coat layer is made of a non-magnetic powder, a binder resin, a lubricant,
An organic solvent and the like are mixed and dispersed together with other necessary components to prepare a coating for the back coat layer, and the coating for the back coating layer is applied to the back surface of the base film having the magnetic layer formed on the surface and dried. Formed.

The non-magnetic powder used for such a back coat layer includes α-Fe ₂ O ₃ , TiO ₂ , CaC
O _3, Ca - carbon black or the like, usually, the magnetic recording medium back coating - those used in the coat layer is widely used as the binder resin and an organic solvent, generally the same binder resin as that used in the magnetic layer And organic solvents are both used.

[0014]

Next, an embodiment of the present invention will be described. Example 1 A magnetic paint comprising the following composition was applied to the surface of a polyethylene naphthalate film having a Young's modulus in the longitudinal direction of 700 kg / mm ² , a Young's modulus in the width direction of 740 kg / mm ² and a thickness of 10.7 µm. It is applied so as to have a dry thickness of 3.0 μm and dried to form a magnetic layer having a glass transition temperature of 55 ° C. On the back surface, a paint for a back coat layer comprising the following composition has a dry thickness.
It was applied to a thickness of 0.8 μm and dried to form a back coat layer. After that, cut to the specified width, the total thickness is 14.0
A μm magnetic tape was made.

Magnetic paint Co-containing γ-Fe ₂ O ₃ powder 82 parts by weight Vinyl chloride-vinyl acetate-vinyl alcohol copolymer 10 10 Polyurethane resin (glass transition temperature 10 ° C.) 6〃 Isocyanate compound 2〃 Car Bon Black 5 〃 α-Al ₂ O ₃ powder 4 〃 myristinic acid 0.7 −-n-butyl stearate 1.0 〃 cyclohexanone 83.5 〃 toluene 83.5 〃

Backcoat layer paint Carbon black 60 parts by weight α-Fe ₂ O ₃ powder 7 ニ ト ロ Nitrocellulose 18 ポ リ ウ レ タ ン Polyurethane resin 12 イ ソ Isocyanate compound 5 〃Cyclohexanone 150 ト ル エ ン Toluene 150 〃

Example 2 In Example 1, the Young's modulus in the longitudinal direction was 700 kg / mm.
^2. The Young's modulus in the width direction is 740 kg / mm ² and the thickness is 10.7
μm polyethylene naphthalate of - instead of Tofirumu, except that the longitudinal direction of the Young's modulus 1430kg / mm ^2, the width direction of the Young's modulus at 1650kg / mm ^2, thickness using aramid film of 7.7 .mu.m, Example As with 1, the total thickness
A 11.5 μm magnetic tape was made.

Comparative Example 1 In Example 1, the Young's modulus in the longitudinal direction was 700 kg / mm.
^2. The Young's modulus in the width direction is 740 kg / mm ² and the thickness is 10.7
A polyethylene terephthalate film having a Young's modulus in the longitudinal direction of 620 kg / mm ² , a Young's modulus in the width direction of 580 kg / mm ² , and a thickness of 10.7 μm was used instead of the μm polyethylene naphthalate film. A magnetic tape having a total thickness of 14.5 μm was produced in the same manner as in Example 1.

Comparative Example 2 In Example 1, the Young's modulus in the longitudinal direction was 700 kg / mm.
^2. The Young's modulus in the width direction is 740 kg / mm ² and the thickness is 10.7
μm polyethylene naphthalate of - instead Tofirumu longitudinal Young's modulus is 700 kg / mm ^2, in the width direction of the Young's modulus 740kg / mm ^2, thickness polyethylene naphthalate of 9.7Myuemu - except using Tofirumu is A magnetic tape having a total thickness of 13.5 μm was produced in the same manner as in Example 1.

Comparative Example 3 In Example 1, the Young's modulus in the longitudinal direction was 700 kg / mm.
^2. The Young's modulus in the width direction is 740 kg / mm ² and the thickness is 10.7
A polyethylene naphthalate film having a Young's modulus in the longitudinal direction of 850 kg / mm ² , a Young's modulus in the width direction of 700 kg / mm ² , and a thickness of 10.7 μm was used in place of the polyethylene naphthalate film of μm. A magnetic tape having a total thickness of 14.5 μm was produced in the same manner as in Example 1.

Comparative Example 4 In Example 1, the Young's modulus in the longitudinal direction was 700 kg / mm.
^2. The Young's modulus in the width direction is 740 kg / mm ² and the thickness is 10.7
A polyethylene terephthalate film having a Young's modulus in the longitudinal direction of 620 kg / mm ² , a Young's modulus in the width direction of 580 kg / mm ² and a thickness of 11.7 μm was used instead of the μm polyethylene naphthalate film. A magnetic tape having a total thickness of 15.5 μm was produced in the same manner as in Example 1.

Comparative Example 5 In Example 1, the Young's modulus in the longitudinal direction was 700 kg / mm.
^2. The Young's modulus in the width direction is 740 kg / mm ² and the thickness is 10.7
A polyethylene terephthalate film having a Young's modulus in the longitudinal direction of 550 kg / mm ² , a Young's modulus in the width direction of 450 kg / mm ² , and a thickness of 14.7 μm was used in place of the μm polyethylene naphthalate film. A magnetic tape having a total thickness of 18.5 μm was prepared in the same manner as in Example 1.

Comparative Example 6 In the composition of the magnetic paint in Example 1, a polyurethane resin having a glass transition temperature of -30 ° C. was used instead of the polyurethane resin having a glass transition temperature of 10 ° C. A magnetic tape was prepared in the same manner as in Example 1 except that a magnetic layer was formed.

With respect to the magnetic tapes obtained in each of the examples and comparative examples, the Young's modulus E in the longitudinal direction and the width direction at 1% elongation was measured. The product of the third power of t, Et ^3, was determined. Further, the obtained magnetic tape is loaded on a VHS video tape recorder and
The F output was measured, and an evaluation of the flatness of the reproduced envelope waveform of the video signal (envelope), a load / unload flaw test, and a cue / rev flaw test were performed. RF output is
A single signal of 6 MHz was recorded and reproduced and represented by an output ratio with respect to a reference tape. In the envelope, a ratio between a maximum value and a minimum value of a video signal output waveform was represented by percentage. In the loading / unloading scratch test, loading / unloading was repeated 10 times at the same location near the end of the cassette on the magnetic tape, and the magnetic tape was visually inspected for damage. And the evaluation was made out of 5 points. In addition, the Cue / Rev scratch test also performed about 5 times at the same point near the end of the cassette on the magnetic tape.
Cue / Rev for 10 seconds was repeated 10 times, and the scratches on the magnetic tape were visually judged and evaluated on a scale of 5 out of 5 points. Table 1 below shows the results.

[0025]

[0026]

As is clear from Table 1 above, Example 1
The magnetic tapes obtained in (2) and (3) had good results in RF output, envelope, load / unload scratch test and Cue / Rev scratch test. It can be seen that the magnetic tape obtained has excellent electrical characteristics, high rigidity and sufficient mechanical strength for practical use even when the total thickness is 15 μm or less.

Continuation of the front page (72) Inventor Kimihiko Konno 1-88 Ushitora, Ibaraki-shi, Osaka Hitachi Maxell, Ltd. (56) References JP-A-2-282925 (JP, A) JP-A 1-220120 ( JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G11B 5/78 G11B 5/70 G11B 5/702 G11B 5/704

Claims (5)

(57) [Claims] 1. The product having a magnetic layer on a base film having a total thickness of 15 μm or less and having the Young's modulus E at 1% elongation and the product of the cube of the total thickness t, Et ³ , is 1 in both the longitudinal and width directions. 0.7 g · mm or more, and the glass transition temperature of the magnetic layer
A magnetic recording medium having a temperature of 40 ° C. or higher . 2. A base film having a Young's modulus of 1650% / mm ² or more at 1% elongation in the longitudinal direction and the width direction and a Young's modulus in the width direction larger than that in the longitudinal direction. the magnetic recording medium according to. 3. A base - Sufuirumu is, polyethylene naphthalate - consisting bets base - a Sufuirumu claim 1 or 2
The magnetic recording medium according to. 4. The magnetic recording medium according to claim 1, wherein the base film is a base film made of aramid. 5. A magnetic layer, the glass transition temperature comprising -25 ° C. or more polyurethane resins as binder component 請
5. The magnetic recording medium according to claim 1.