JP3182745B2 - Magnetic tape - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating type magnetic tape.

[0002]

2. Description of the Related Art For example, in a camera-integrated VTR represented by the 8 mm system or the VHS-C system, a small tape cassette is used in order to reduce the size and weight.
For this reason, it is difficult to secure a recording time, and a maximum of 2 hours is used in the 8 mm system, and a maximum of 20 hours in the standard mode in the VHS-C system.
The recording time is limited to minutes, and sufficient recording time cannot be obtained.

[0003] In order to solve such a problem of recording and reproducing time, a thin magnetic tape accommodated in a tape cassette is used.
Increasing the length of the tape wound in the winding area of the tape cassette has been considered.

[0004] However, if the tape thickness is reduced in such a manner, the strength is correspondingly reduced, and there is a problem of poor contact with the head and tape damage due to running.

That is, conventionally, a camera-integrated VTR
The magnetic layer used for the magnetic tape was formed by applying a magnetic paint mainly composed of a ferromagnetic metal powder and a binder on a non-magnetic support made of polyethylene terephthalate (PET). However, if the tape thickness is simply reduced, scratches and edge breakage due to a decrease in the tape strength are liable to occur, and the head contact (contact with the head) tends to deteriorate.

Therefore, in order to avoid the above-mentioned problems in response to the above-mentioned tape thickness reduction, a film such as a PEN (polyethylene naphthalate) film having a higher Young's modulus than a PET film is generally used. Is being adopted.

However, when the PEN film is used as a non-magnetic support for a thin tape, the strength and rigidity of the tape are improved as compared with the case where PET is used.
Not quite satisfactory. That is, if a PEN film is simply used for a thin tape, there still remain problems such as tape damage due to running and insufficient contact with the head. Further, in the PEN film, the rigidity and strength are different depending on the type, and it is considered that it is necessary to sufficiently examine this point.

[0008]

According to the study by the present inventor, the damage caused by the running of the tape is reduced by improving the Young's modulus in the width direction of the base as in the case of a PEN film. In some cases, it is insufficient.) However, it has been found that the hitting characteristics with respect to the head are adversely deteriorated. An object of the present invention is to provide a magnetic recording medium such as an ultra-thin magnetic tape capable of recording / reproducing for a long time, having both good anti-damage characteristics and hitting characteristics.

[0009]

That is, the present invention relates to a magnetic tape having a magnetic layer formed on a non-magnetic support by coating the non-magnetic support with a Young's modulus in a width direction of _ETD and a longitudinal direction. when the Young's modulus and E _MD of, E _TD ≧ E _MD, a _{^{800kg / mm 2 ≦ E TD ≦}} 1010kg / mm 2 600kg / mm 2 ≦ E MD ≦ 930kg / mm 2, the non-relative to the total thickness magnetic tape The present invention relates to a magnetic tape, wherein the ratio of the thickness of the magnetic support is 1: (0.55 to 0.75), and the glass transition point of the magnetic layer is 60 ° C to 84 ° C.

As a result of studying to solve the above-mentioned problems, the present inventor has found that a non-magnetic support (base) having a specific value of Young's modulus in the longitudinal and width directions is used, and further having a thickness structure and magnetic properties. It has been found that such a problem can be solved by setting the glass transition point of the layer to a specific value.

First, when the Young's modulus of the nonmagnetic support is E _{TD in the} width direction and E _{MD in the} longitudinal direction, E _TD ≧ E _MD , 800 kg / mm ² ≦ E _TD ≦ 1010 kg / Mm ² 600 kg / mm ² ≦ E _MD ≦ 930 kg / mm ² . That is, for the Young's modulus of the base,
In particular, when a base film that does not satisfy E _MD ≧ 600 kg / mm ² is used, the hitting characteristics are deteriorated. When E _TD ≧ E _MD and E _TD ≧ 800 kg / mm ² are not satisfied, the damage resistance is deteriorated. . However, it is preferable that both E _TD and E _MD are not so large in terms of the hitting characteristics, running characteristics, and the like, and the upper limits are preferably set as described above.

Further, regarding the thickness configuration, the total thickness of the medium (T
The ratio of the thickness of the nonmagnetic support for _{T) (T B): (} T B
/ T _T ) is less than 0.55, the anti-damage property is poor,
If it exceeds 0.75, the hit characteristics will deteriorate, so (T _B
/ T _T ) should be between 0.55 and 0.75.

However, as described above, in particular, E _TD ≧ E _MD and E _TD ≧ 800 kg / mm ² , E _MD ≧ 600 kg / mm ² , and the thickness configuration satisfies (T _B / T _T ) = 0.55 to 0.75. However, when the glass transition point (Tg) of the magnetic layer does not particularly satisfy Tg ≧ 60 ° C., both the damage resistance property and the hitting property with the head deteriorate. However, it is better not to make this Tg too high from the viewpoint of powder dropping of the magnetic powder, etc., and it is better to set the above upper limit.

Therefore, for the base: E _TD ≧ E _MD and 800 kg / mm ² ≦ E
_TD ≦ 1010kg / mm ² , 600kg / mm ² ≦ E _MD ≦ 930kg
/ Mm ² , Tape thickness composition: (T _B / T _T ) = 0.55 to 0.7
5. Regarding magnetic coating: glass transition point (Tg) is 60 ° C ≦ Tg
Only when all of the conditions of ≤84 ° C. are satisfied can a magnetic tape having anti-damage characteristics and hitting characteristics which can be recorded and reproduced for a long time be obtained.

In the above description, the base Young's modulus E
_{In order to set TD} and _EMD within the above ranges, use a film with high elastic modulus such as polyethylene naphthalate or polyaramid film, and further control the width at the time of film formation and the stretching ratio in each longitudinal direction. Becomes possible.

The thickness ratio (T _B / T _T ) can be controlled by adjusting the thickness of the non-magnetic support at the time of molding and the coating thickness of the magnetic layer or the like. Can be controlled mainly by the type of the binder, the selection of the curing agent, and the like.

In the magnetic recording medium of the present invention, examples of the non-magnetic support include polyesters such as polyethylene naphthalate, polyimide, polyamide imide and polyaramid.

The magnetic layer provided on the nonmagnetic support is preferably a magnetic coating film formed by applying a magnetic paint mainly comprising a magnetic powder and a binder to the surface of the nonmagnetic support. .

When the magnetic layer is a magnetic coating, a magnetic powder,
Any known binder can be used, and is not limited at all. As magnetic powder, γ-Fe ₂ O
_3, the ferromagnetic iron oxide particles such as cobalt coating gamma-Fe ₂ O _3,
Examples thereof include ferromagnetic chromium dioxide-based particles, ferromagnetic metal-based particles made of a metal such as Fe, Co, and Ni, and alloys containing these, hexagonal plate-like hexagonal ferrite fine particles, and the like.

Examples of the binder include polymers such as vinyl chloride, vinyl acetate, vinyl alcohol, vinylidene chloride, acrylates, methacrylates, styrene, butadiene, and acrylonitrile, or copolymers of two or more of these. , Polyurethane resin, polyester resin, epoxy resin and the like. A hydrophilic group such as a sulfonic acid group, a carboxyl group, or a phosphoric acid group may be introduced into these binders in order to improve the dispersibility of the magnetic powder.

In addition to the magnetic powder and the resin binder, a dispersant, an abrasive, an antistatic agent, a rust inhibitor and the like may be added to the magnetic coating film as additives.

In the magnetic recording medium of the present invention, a top coat layer made of a rust preventive or a lubricant is provided on the magnetic layer, or the top surface of the non-magnetic support on which the magnetic layer is not formed is provided. The back coat layer may be provided.

FIG. 1 shows a (magnetic tape for VTR) as an example of the magnetic recording medium of the present invention. That is,
A nonmagnetic support 1 has a magnetic layer 2 containing magnetic powder, a binder and the like on one surface. Further, the other surface may have a back coat layer 3 mainly composed of a non-magnetic powder and a binder.

[0024]

EXAMPLES Hereinafter, the present invention will be described with reference to specific examples, but the present invention is not limited to the following examples.

Preparation of Sample Cassette Tape After a metal-based magnetic paint having the following composition was dispersed in a sand mill, 5 parts by weight of a curing agent (Coronate L) was added, and base films (a to h) having the specifications shown in Table 2 were added. ) On top, apply after calendering to the value shown in Table-3 →
Drying → winding. Then, after calendering → curing → backcoating (0.6μm), slit to 8mm width, 133m (1mm in 8mm video NTSC standard mode)
13 minutes of samples were obtained by incorporating the 50-minute recording) into an 8 mm cassette. The composition of the metal-based magnetic paint is as follows. Table 1 shows the details of the binder composition.

Composition of metal-based magnetic paint Fe-Co metal magnetic powder: (specific surface area = 55.8 m ² / g) 100 parts by weight Binder: PVC-based copolymer (see Table 1) -1) 20 parts by weight Alumina powder 10 parts by weight Lubricant: 1.5 parts by weight of stearic acid 1.5 parts by weight of butyl stearate Solvent: methyl ethyl ketone / toluene / cyclohexanone 100/100/50 parts by weight

* The Young's modulus of the base film was controlled by controlling the stretching ratio during molding in the longitudinal or width direction. The Young's modulus was determined by a tensile test under the following conditions. Temperature 23 ± 2 ℃, Humidity 64 ± 5% RH Sample width 6.25mm × Effective sample length 100mm Peeling speed 100mm / min

Regarding the glass transition point of the magnetic coating film, Tan-δ was measured at a frequency of 110 KHz and a heating rate of 1 ° C./min using a direct connection type Vibron DDV-II manufactured by Toyo Baldwin Co., Ltd. The temperature at the peak position of δ was determined and defined as the glass transition point.

With respect to the damage characteristics and hit characteristics of the 8 mm video cassette tape prepared as described above,
The evaluation was performed by the following method.

Evaluation method Damage characteristics: Each sample was recorded for 10 minutes at a temperature of 40 ° C. and 80% RH for 10 minutes with 13 8 mm video cassette recorders of 10 volumes each and recorded under the same environment. The reproduction of the part was repeated 100 times. If the tape (especially the edge part) was not damaged even after repeating the reproduction 100 times, the tape was ◎. If the tape was mildly damaged but no image noise was seen on the playback screen, the tape was ○. If the image noise was displayed on the screen, it was △, and if it was impossible to run due to tape damage during playback, ×
And

Hit characteristics: Recording was performed for 3 minutes using an 8 mm video cassette recorder, and the reproduced RF envelope waveform was observed with an oscilloscope. When the ratio between the peak and the valley bottom of the envelope waveform was 0.8 or more, it was evaluated as ○, when it was 0.8 or less, no noise was observed on the reproduction screen, and when it was 0.8 or less and the noise was observed on the reproduction screen, ×.

The results of the evaluation are shown in Table-4. From these results, regarding the thickness configuration of the tape, when (T _B / T _T ) is less than 0.55 (Comparative Example 1), the tape damage characteristics are poor, and when it exceeds 0.75 (Comparative Example 2), the hitting characteristics are poor. Become. In addition, as for the Young's modulus of the base film, when a base film that does not satisfy E _MD ≧ 600 kg / mm ² is used (Comparative Example 3), the hitting characteristics are deteriorated, and E _TD ≧ E _MD and E _TD ≧ 800 kg / mm.
^{When the value of 2} is not satisfied (Comparative Example 4), the tape damage characteristics deteriorate. Further, for the base film, E _TD ≧
E _MD and E _TD ≧ 800 kg / mm ² , E _MD ≧ 600 kg / mm ² , and regarding the thickness configuration of the tape, (T _B / T _T ) = 0.55
The glass transition point (T
g); when Tg ≧ 60 ° C. is not satisfied (Comparative Example 5),
Both the tape damage characteristic and the contact characteristic with the head deteriorate.

On the other hand, regarding the base film,
E _TD ≧ E _MD and 800 kg / mm ² ≦ E _TD ≦ 1010 kg / mm
² , 600 kg / mm ² ≦ E _MD ≦ 930 kg / mm ² , (T _B / T _T ) = 0.55 to 0.75 for the thickness configuration of the tape, and further, for the magnetic coating film, the glass transition point (Tg);
Examples 1 to 8 satisfying each condition of 60 ° C. ≦ Tg ≦ 84 ° C.
It can be seen that a very good property against tape damage and contact property with the head can be obtained.

[0034] Binder A: PVC-based copolymer (vinyl chloride = 84 wt%,
-OSO ₃ K = 0.08mmol / g containing) binder B: aromatic polyester polyurethane (polyester, ethylene glycol + isophthalic acid + terephthalic acid -SO ₃ Na = 0.14mmol / g containing) binder C: an aromatic polyester (polyethylene iso And terephthalate) polyurethane (polyester;
Ethylene neopentyl glycol + isophthalic acid + terephthalic acid -SO ₃ Na = 0.08 mmol / g) Binder D: aliphatic polyester polyurethane (polyester; butanediol + adipic acid (main component) -SO)
₃ Na = 0.15 mmol / g contained)

[0035]

[0036]

[0037]

[0038]

[0039]

[0040]

As is apparent from the above description, in the present invention, not only the Young's modulus in the width direction and the longitudinal direction of the base but also the glass transition point and the thickness structure of the magnetic layer are specified to predetermined values. Therefore, even when the thickness is reduced, an optimum tape strength can be obtained with respect to both the anti-image property and the contact property with the head. Therefore, according to the present invention, for example, even when used in a small tape cassette used in a camera-integrated VTR or the like, a long recording / reproducing time can be obtained, the hit to the head is good, and the device has been used for a long time. Even in such a case, it is possible to obtain a medium that is hardly damaged.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a configuration example of a magnetic recording medium to which the present invention is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Non-magnetic support 2 ... Magnetic layer 3 ... Back coat layer

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-50-46303 (JP, A) JP-A-1-263918 (JP, A) JP-A-2-218014 (JP, A) JP-A-4- 292933 (JP, A) JP-A-5-128489 (JP, A) JP-A-2-202924 (JP, A) JP-A-2-202925 (JP, A) JP-A-2-208039 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G11B 5/70

Claims (1)

(57) [Claims] 1. A magnetic tape magnetic layer on a nonmagnetic support is coated and formed, the width direction of the Young's modulus E _TD of the non-magnetic support, when the longitudinal direction of the Young's modulus and E _MD, E _TD ≧ E _MD , 800 kg / mm ² ≦ E _TD ≦ 1010 kg / mm ² 600 kg / mm ² ≦ E _MD ≦ 930 kg / mm ² , and the ratio of the thickness of the non-magnetic support to the total thickness of the magnetic tape is 1 : A magnetic tape characterized in that (0.55 to 0.75) and the glass transition point of the magnetic layer is 60 ° C to 84 ° C.