JPH09147353A - Magnetic recording medium and cassette - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the traveling property and durability of a tape by regulating tension at the traveling time of the tape when prescribed back tension is given so as to become a specific value. SOLUTION: The magnetic tape 1 is formed with a magnetic layer 23 by applying magnetic paint made by dispersing magnetic power and a lubricant into a binder resin on a nonmagnetic supporting body 21. On this tape 1, tension T1 at the traveling time under back tension of 0.1 newton is <=0.6 newton and tension T2 at the time of lowering traveling speed down by 2% by raising the back tension is >=0.5 newton. Then, a value of T2 /T1 is >=1.4. This tape 1 is particularly suitable for a microcassette.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention contains a magnetic recording medium such as a magnetic tape having a magnetic layer (in particular, a magnetic layer containing magnetic powder and a binder as a main component), and such a magnetic recording medium. It concerns cassettes.

[0002]

2. Description of the Related Art Generally, in order to form a magnetic layer in a magnetic recording medium such as a magnetic tape, a magnetic coating material containing necessary components such as magnetic powder, a binder (binder resin), an organic solvent, a curing agent and an additive is used. It is applied on a non-magnetic support such as a polyethylene terephthalate film, dried and cured.

Generally, in a magnetic tape for a cassette for video, audio, etc., in order to maintain good running property and durability, a surface protrusion is provided on a non-magnetic support and a magnetic layer is laminated thereon. Is controlling the friction coefficient of
If the coefficient of friction is too high, the magnetic tape is caught by the guide means such as guide pins or the magnetic head, and smooth running cannot be obtained, and the durability of the magnetic tape decreases. Therefore, a method of applying a lubricant to the surface of the magnetic layer or internally adding a lubricant to the magnetic layer is adopted, whereby the friction coefficient of the magnetic layer is lowered and the running property and durability are maintained.

FIG. 10 is an enlarged cross-sectional view of a magnetic tape for video, audio, etc. configured for such a purpose.

That is, FIG. 10 (a) is a cross-sectional view showing an example of the structure of a magnetic tape.
A magnetic layer 123 having a lubricant internally added is provided on the surface of the non-magnetic support 21 internally added with particles of O ₂ , CaCO ₃ , kaolin, etc., and a magnetic tape 27 is constituted. Figure 10 (b)
Unlike FIG. 1A, shows a magnetic tape 28 in which a lubricant layer 26 is laminated on a magnetic layer (containing no lubricant) 23.

FIG. 9 is a cross-sectional view of a generally widely used compact cassette 40. The traveling path of the magnetic tape 1A will be described with reference to this figure. First, the magnetic tape 1A wound on one reel 11 passes through the guide pin 13, the guide roller 14, and the guide pin 15, and then the leaf spring 17 is passed.
With the back surface of the non-magnetic support body 21 slidingly contacting the pad 16 supported by, the reel 16 is further wound around the other reel 12 via the guide pin 15, the guide roller 14 and the guide pin 13. In the middle of the running path, the tape guide 20 slightly protruding from the inner main surfaces of both cassette halves regulates the movement in the width direction.

In the opening 19, a magnetic head (not shown) sandwiches the magnetic tape 1 with the pad 16 and slides on the magnetic layer surface of the magnetic tape 1A for recording or reproduction. Then, when the reels 11 and 12 are rotated and wound as shown in the drawing, the cassette 10 is turned upside down and reattached to the deck, the magnetic tape 1A is taken out from the reel 12, wound on the reel 11, and recorded in the same manner as above. Alternatively, perform playback. In the auto-reverse deck, the reels 11 and 12 rotate in the opposite direction immediately after the reel 12 is completely wound and the magnetic tape 1A is rotated.
Record or play while rewinding. In the figure, 18A is
It is a through hole provided in the cassette half for inserting a capstan.

FIG. 8 is a sectional view of the microcassette 30 similar to FIG. The magnetic tape 1B wound around one reel 31 includes a guide pin 33, a guide roller 34, and guide pins 35, 35, 35, 35 provided at four positions on the front side of the cassette.
It is wound around the other reel 32 via the guide roller 34 and the guide pin 33.

Pads 36, 36 supported by leaf springs 37 are located between the pair of left and right guide pins 35, 35, and during recording or reproduction, the magnetic tape 1B is
Recording and reproduction are performed by traveling while being sandwiched between an upstream pad 36 and a magnetic head (not shown). In the figure, 39 and 39 are openings for inserting a magnetic head, and 38 is a through hole provided in a cassette half for inserting a capstan.

Generally, a capstan is inserted into the through hole 38, and the magnetic head is positioned so as to press the pad 36 on the upstream side of the magnetic tape running. The microcassette 30 is further provided with through holes 38 'and 38' for inserting a capstan so that it can be adapted to a special deck. Others are the same as in the compact cassette 40 of FIG.

As described above, the magnetic tape runs in the cassette while being sandwiched between the pad and the magnetic head or being pressed by the leaf spring through the pad by the leaf spring. Therefore, the running performance of the tape guide, the sandwiching member, or the pressing member is determined depending on the hitting condition.

The compact cassette 40 shown in FIG. 9 has a total of eight guide pins, whereas the micro cassette shown in FIG.
The 30 has a total of 6 guide pins, and the running path of the magnetic tape is simple. In addition, the compact cassette 40 of FIG. 9 has a width W ₁ of 100.4 mm and the depth D ₁ of 63.8 mm, while the microcassette 30 of FIG. 8 has a width W ₂ of 5 mm.
The size is 0.2 mm and the depth D ₂ is 33.5 mm, which is about 1/2 of the size of the compact cassette and about 1/4 of the area of the main surface.

In the microcassette, as described above, the magnetic tape runs in a very narrow cassette and the number of guide pins is small, so that the magnetic tape may cause running failure due to unstable running property. The reason for this is that the microcassette is ultra-small, the tape thickness is thin, and the traveling path forms a predetermined path within a narrow space, so there are many restrictions, and the back tension is low due to the mechanism.

That is, the tape for the micro cassette is
Due to the mechanism, it is necessary to maintain stable running with low back tension.

Incidentally, the magnetic tape for the microcassette has a tape width of 3.81 mm and a thickness of 9 μm, which is much thinner than that for a compact cassette having a thickness of 18 μm.

Therefore, the back tension is compensated by maintaining a certain friction coefficient, but if the friction coefficient is too high, the magnetic powder falls off, causing a so-called powder falling phenomenon,
In addition to the deterioration of recording performance and reproduction output, the contact with the tape guide or the guide pin becomes strong, the edge is easily damaged or broken, and the so-called wakame phenomenon occurs in which both side edges are elongated. However, there is a limit to lowering the friction coefficient, and there is a special problem that running performance cannot be improved simply by lowering the friction coefficient.

As described above, particularly in the case of the microcassette, it is necessary to give the magnetic tape an appropriate friction, which improves the running property but impairs the durability.
That is, it has been found that it is difficult to achieve both running performance and durability.

Further, even in the compact cassette, a small tape recorder, for example, a pocket size, whose running property is unstable, and a tape path guide for bringing the magnetic tape into contact with the magnetic head at the time of recording / reproducing are made of plastic. When used in a cassette deck, the magnetic tape may not run smoothly. The causes include increased friction and tape slip.

Therefore, it is necessary to impart appropriate friction characteristics to the magnetic tape, but merely lowering the friction of the magnetic tape leads to damage to the magnetic tape. Depending on the situation like this, even if it is in a compact cassette, it can be used in any tape recorder or cassette deck, as in the above-mentioned micro cassette.
To ensure durability while ensuring good running performance,
Very difficult.

[0020]

SUMMARY OF THE INVENTION The present invention has been made in view of the above situation, and it is difficult to apply back tension, for example, a micro-cassette, or running is apt to be unstable, for example, a pocket-sized tape. An object of the present invention is to provide a magnetic recording medium excellent in running property and durability even when used in a compact cassette used for a cassette deck having a recorder or a plastic guide, and a cassette containing such a magnetic recording medium. To do.

[0021]

Means for Solving the Problems The present inventor has conducted extensive studies and experiments from various angles in order to achieve the above object. As a result, by adjusting the surface roughness of the magnetic tape and the amount of lubricant added, it was concluded that appropriate back tension is imparted and that both running properties and durability are improved, leading to the present invention. Is.

That is, the first invention is a magnetic recording medium having a magnetic layer (in particular, a magnetic layer formed by coating a non-magnetic support with a magnetic paint mainly containing a binder and magnetic powder). The tension T ₁ when running while giving a back tension of 0.1 Newton is 0.6 Newton or less, and the back tension is increased to increase the running speed to 2
The magnetic recording medium is characterized in that the tension T ₂ when reduced by 0.5% is 0.5 Newton or more and the value of T ₂ / T ₁ is 1.4 or more.

The second invention is a magnetic recording medium having a magnetic layer (in particular, a magnetic layer formed by coating a non-magnetic support with a magnetic paint mainly containing a binder and magnetic powder). The tension T ₁ when running while giving a back tension of 0.1 Newton is 0.45 Newton or less, and the back tension is increased to increase the running speed to 2
The magnetic recording medium is characterized in that the tension T ₂ when it is reduced by 0.5% is 0.5 Newton or more and the value of T ₂ / T ₁ is 1.2 or more.

The present invention also provides a cassette containing the magnetic recording medium according to the first invention and a cassette containing the magnetic recording medium according to the second invention.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, it is desirable to have a magnetic layer on a non-magnetic support and to internally add and / or apply a lubricant to the magnetic layer.

Further, in the present invention, the values of the tape tensions T ₁ and T ₂ can be satisfied by the average plane roughness Ra of the magnetic layer and / or the amount of the lubricant added.

The magnetic recording medium according to the first aspect of the invention is particularly suitable for a microcassette.

The magnetic recording medium according to the second invention is particularly suitable for a compact cassette.

As the materials used for the non-magnetic support, fine particles, underlayer, lubricant, binder, magnetic layer and back coat layer constituting the magnetic tape, the following materials can be used, for example.

The binder resin is not particularly limited as long as it is a known binder such as vinyl chloride resin, polyester resin, polyurethane resin and polyester polyurethane resin. However, it is not preferable that the dispersibility of the magnetic powder is impaired or the heat resistance and abrasion resistance are significantly reduced.

Examples of preferable resins include JP-A-61-161
200113, JP 61-202327, JP 2-121114, and JP 2-306.
The binder resins described in JP-A No. 427, JP-A-3-153785, JP-A-3-171418, JP-A-4-307420 and the like can be mentioned.

Specific examples of the vinyl chloride copolymer include a vinyl chloride-vinyl alcohol copolymer into which a phosphate group, a sodium sulfonate group, a potassium sulfonate group, a phosphate amine salt and a sulfonate amine salt are respectively introduced. Polymer, vinyl chloride-hydroxypropyl acrylate copolymer having phosphoric acid or sulfonic acid group introduced, vinyl chloride-hydroxyethyl acrylate copolymer having phosphoric acid or sulfonic acid group introduced, phosphoric acid or sulfonic acid group introduced Examples thereof include a vinyl chloride-hydroxypropyl methacrylate copolymer, a vinyl chloride-hydroxyethyl methacrylate copolymer having a phosphoric acid or sulfonic acid group introduced. Further, these vinyl chloride-based copolymers may be copolymerized with a monomer containing an epoxy group, and a specific example thereof is trade name MR110 manufactured by Zeon Corporation.

Further, in combination with these vinyl chloride type copolymers, JP-A-54-157603 and JP-A-57-9.
Various resins known in JP-A-2422, JP-A-63-138523, etc., in which a polar group is introduced into the main chain or side chain of a binder resin, for example, sulfonic acid metal salt, carboxyl group, phosphoric acid group, etc. It is also possible to use a polyurethane resin, polyester polyurethane or the like introduced with.

Examples of the magnetic powder used in the present invention include γ-Fe ₂ O ₃ powder, Co-containing γ-Fe ₂ O ₃ powder, CrO ₂ powder, Fe powder, Co powder, Co ferrite powder, and Ba ferrite powder. A wide range of conventionally known various magnetic powders such as BET specific surface area of 45 m ² / g or more is obtained by highly packing and orienting the above magnetic fine powder.
A high-performance magnetic recording medium can be obtained.

Nonmagnetic solid additive particles are generally added to the magnetic coating material. As such nonmagnetic solid additive particles, abrasive particles generally used in magnetic recording media, such as α-, are used. Al ₂ O ₃ powder, Cr ₂ O ₃ powder, α
All of —Fe ₂ O ₃ powder, ZrO powder, TiC powder, SiC powder, BN powder, TiO ₂ powder and the like are preferably used. Furthermore, when the one whose particle surface is treated with the organosilazane compound is used, the dispersibility of the non-magnetic solid additive particles is further improved, and the powder of the non-magnetic solid additive particles does not fall off. The continuous sliding durability can be further improved.

Further, in the magnetic paint, if necessary, a dispersant such as lecithin, a lubricant such as stearic acid ester, an antistatic agent such as carbon black, an abrasive such as alumina,
A rust preventive agent or the like may be added. As the dispersant, the lubricant, the antistatic agent, the rust preventive, and the like, any conventionally known material can be used and is not limited at all.

Examples of the non-magnetic support usable in the magnetic recording medium according to the present invention include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate, aramid, and the like. The shape may be a sheet shape, a sheet shape, a tape shape, a disk shape, or the like. An intermediate layer or an undercoat layer may be provided on the surface of the non-magnetic support in order to improve the adhesiveness of the magnetic layer.

The magnetic recording medium of the present invention may be produced according to a conventional method, for example, magnetic powder, polyurethane resin having sulfonic acid metal salt and OH group, curing agent, phosphoric acid group or sulfonic acid group. To prepare a magnetic paint by adding a vinyl chloride copolymer having a polar group consisting of a metal base or a derivative thereof introduced with an organic solvent and other additives such as non-magnetic solid additive particles to prepare a magnetic paint. The coating may be applied onto a substrate such as a polyester film by an arbitrary method such as spraying or roll coating, and dried.

As the organic solvent, methyl ethyl ketone,
Cyclohexanone, methyl isobutyl ketone, toluene, tetrahydrofuran, dioxane, dimethylformamide, ethyl acetate and the like may be used alone or in combination.

To provide a protrusion on the surface of the non-magnetic support,
Fine particles of SiO ₂ etc. with an average particle size of 100-200 nm
It is recommended to place it in the support at a rate of about 100 pieces / mm ² .

The non-magnetic powder used in the back coat layer is generally composed mainly of carbon black, but in addition to this, calcium carbonate, alumina, titanium oxide, α-iron oxide and the like can be mentioned. Further, as the magnetic powder, any of those described above as those used for the magnetic layer can be used. They may be used alone or in combination. As the binder and other additives, any of those described above for use in the magnetic layer can be used, and they may be used alone or in combination. However, it is not always necessary to provide this back coat layer.
An overcoat layer may be provided on the magnetic layer.

[0042]

EXAMPLES Examples of the present invention will be described below, but it goes without saying that the present invention is not limited to the following examples.

<Embodiment 1 (Embodiment of the First Invention)> This embodiment is an example of a magnetic tape for a microcassette. As described above, when the magnetic tape has a high friction coefficient, not only the running property is poor but also the durability is poor. On the other hand, if the coefficient of friction is low, slippage cannot be achieved and the required running performance cannot be obtained. In particular, the microcassette is extremely small, and the magnetic tape used for it is also extremely small, so it is mechanically weak, and special consideration is required to smoothly travel the required travel route within a restricted and narrow cassette. .

That is, it is difficult to apply the back tension, but stable traveling performance cannot be obtained unless the necessary back tension is secured. Therefore, it is desired to provide an appropriate friction coefficient in order to stabilize the running property.

Therefore, in this embodiment, various non-magnetic supports having different surface properties are used, and the magnetic powder and the lubricant are dispersed in the binder resin on the non-magnetic support 21, as shown in FIG. The magnetic coating was applied to form the magnetic layer 23, and the magnetic tape 1 was manufactured.

In the magnetic tape for a microcassette having the above-mentioned basic structure, in order to pursue the optimum friction coefficient, the size of the SiO ₂ fine particles to be arranged on the non-magnetic support (base film) 21 of polyethylene terephthalate, By changing the disposition density and the amount of the lubricant added to the magnetic layer 23, seven kinds of sample tapes A to G having different surface roughness and lubricity of the magnetic layer 23 were prepared as shown in Table 1 below. Magnetic layer 23
Is a binder resin containing vinyl chloride resin, polyester resin, polyurethane resin, and γ-Fe ₂ O ₃
The magnetic powder of is dispersed.

[0047]

[0048]

In the preparation of the magnetic paint and the magnetic tape, this composition was mixed in a ball mill for 48 hours, then 5 parts by weight of a polyisocyanate curing agent was added, and the mixture was further added to 30 parts.
The mixture was minutely mixed and applied onto a polyethylene terephthalate film having a thickness of 6 μm so that the thickness after drying would be 3 μm. After drying, it was cut into 3.81 mm width to obtain a magnetic tape.

The sample tapes thus prepared were measured for T ₁ and T ₂ with a measuring device as shown in FIG.
In this device, a head 9 corresponding to a magnetic head is arranged under the same condition that the magnetic head actually contacts the magnetic tape of the microcassette. A tension gauge G ₁ is arranged on the upstream side of the magnetic head 9 and a tension gauge G ₂ is arranged on the downstream side with respect to the running direction D of the magnetic tape 1.

The magnetic tape 1 is sandwiched between a capstan 7 and a pinch roller 8 which rotate at a constant speed and runs at a constant speed. The tension gauge G ₁ is composed of a main roller 3 on the upper part and driven rollers 4a, 4b on the lower part, and the magnetic tape 1
As shown in the figure, the paper runs while being sandwiched between the main roller 3 and the driven rollers 4a and 4b. Similarly to the tension gauge G ₁ , the tension gauge G ₂ has a main roller 5 and a driven roller 6 as well.
The magnetic tape 1 is composed of a and 6b and travels while being similarly sandwiched.

The tension gauge G ₁ mechanism on the upstream side is provided with a slight braking function for the running of the magnetic tape 1 and a gauge showing the braking force. The tension gauge G ₂ mechanism on the downstream side has a function of pulling the magnetic tape 1 in the running direction against the braking force of the tension gauge G ₁ mechanism and a gauge showing the force.

Therefore, the braking force of the upstream side tension gauge G ₁ acts as the back tension BT in the direction of the arrow shown in FIG. 3, and conversely the pulling force TT of the downstream side tension gauge G ₂ is the opposite arrow shown in the same figure. Acts as tape tension in the direction. By this, the magnetic tape 1 is given a tension, and the same state as that of the magnetic head slidingly contacting in the cassette is created.

As shown in FIG. 3, the magnetic tape 1 is attached to the apparatus and the magnetic tape 1 is attached to the magnetic tape 2 as shown in FIG.
It was measured while running at a specified speed of 3.8 mm / sec. Then, back tension was applied so that the tension gauge G ₁ was 0.1 Newton, and the value of the tension gauge G ₂ at that time was set to T ₁ . In addition, the back tension is gradually increased by the tension gauge G ₁ ,
Tension gauge G when tape speed decreases by 2%
A value of ₂ and T _2, and further calculates the value of T ₂ / T _1. Note that 2% is merely a standard for measurement. Reference numeral 50 in FIG. 3 is a frequency counter, which has a predetermined frequency (for example, 3).
KHz) signal is recorded on the magnetic tape and the running speed is 2
% It is for reading the value when changing.

According to the above-mentioned measurement procedure, T ₁ and T ₂ were measured for seven types of sample tapes (Sample A to Sample G in Table 1).
The results of measuring the value of are as shown in Table 2 below.

[0056]

After the above measurement, these sample tapes were further assembled in the microcassette shown in FIG. 8, and the tape recorder for the microcassette was used to measure the decrease in the tape output (10kHz-20dB) after 1000 passes, and damage was also taken. The results of the determination are shown in Table 3 below. For damage, the elongation (so-called wakame) of both side edges of the magnetic tape was visually determined. In Table 3, ∘ indicates that no damage was recognized, Δ indicates that the damage was slight, and × indicates that the damage was severe.

[0058]

From these results, the magnetic tape for a microcassette can be obtained as shown in FIG. 1 as a curve showing the running and durability tendencies of the magnetic tape depending on the magnitude of the friction coefficient. In the graph of FIG. 1, the solid line curve shows the output decrease and the change of damage due to T ₁ , and the broken line curve shows the output decrease and the change of damage due to T ₂ .

If either of the values of T ₁ and T ₂ changes,
The value of T ₂ / T ₁ naturally changes. Therefore, in Table 3, it is considered that the samples F and G in which the output reduction and the damage are particularly small are the samples in which the surface roughness and the lubricant addition amount are most balanced, and among the samples F and G, T ₁ and T of the other samples are considered. the value of T _1, T ₂ of the sample F that is not far removed from the _second value to the standard, to calculate the T ₂ / T ₁ for each by replacing T _1, T ₂ of each sample at these values the sample, The horizontal axis of T _{1 and} the horizontal axis of T ₂ in FIG.

That is, the T ₂ value 0.53 of the reference sample F is used as a standard, and the T ₂ (0.53) of the sample F is set to the value of T ₂ of the sample F.
Calculated by dividing the T ₂ (0.53) T ₁ of each sample is close to, T ₂ / T ₁ on the horizontal axis from these T ₂ / T ₁ value (it is denoted in the points plotted in the graph) I set the scale of.

Similarly, the value of T ₁ of the reference sample F is 0.37
Was the standard, sample T ₂ of the near T ₁ (0.37) value of T ₁ is the sample F, determined by dividing the T ₁ (0.37) of the sample F, which the T ₂ / T ₁ value (the graph (These are added to the plotted points of the above) and the scale of T ₂ / T _{1 on} the horizontal axis is set.

The data of sample E (maximum output reduction), in which the values of T ₁ and T ₂ are far from those of sample F, are not adopted in FIG.

In the solid curve, there is a tendency that the output decrease and the damage sharply increase when T ₁ exceeds 0.6 Newton, and the output decrease and the damage are the smallest when T ₂ / T ₁ is 1.4. In the dashed curve, T ₂ / T ₁ is
At 1.4 or more, the output reduction and damage are small,
In particular, when T ₂ is less than 0.5 Newton and T ₂ / T ₁ is less than 1.4, the output decrease and the damage are rapidly increased.

From the above results, T ₁ is 0.6 Newton or less, T ₂ is 0.5 Newton or more (hatched arrow range), T
_It can be understood that output reduction and damage are small if all three conditions of ₂ / T ₁ of 1.4 or more are satisfied.

FIG. 2 is a bar graph showing the values in Tables 2 and 3 above. Then, the marks (◯), (Δ), and (×) above each bar graph are evaluated based on the results shown in FIG. 1. Table 2, Table 3
According to Fig. 2, the relationship between T ₁ , T ₂ , T ₂ / T ₁ and output reduction and damage is a subtle difference that cannot be seen at first glance, but according to the bar graph in Fig. 2, this difference is a factor that determines pass / fail. But it turns out.

From the above, as shown in Table 1,
The magnetic tape can be designed according to the surface property of the non-magnetic support, which is the basis of the surface property of the magnetic tape for the microcassette, and the surface roughness Ra of the magnetic layer formed thereby and the addition amount of the lubricant. .

Next, for comparison with the data of each sample of the above-mentioned magnetic tape for microcassette, a magnetic tape obtained by sampling from the same magnetic tape raw material (before being cut into a predetermined width) is compacted. It was assembled in a cassette and the measurement was carried out in the same manner as above. The measurement results are shown in Table 4 below.

[0069] * The output drop is the tape output drop (10KHz-20dB drop) after 100 passes on the tape deck for compact cassettes.

In the magnetic tape for the compact cassette, the friction coefficient of the magnetic tape has little effect on the running property in the former case and in the latter case it is slight, but in the case of the magnetic tape for the micro cassette, this effect is remarkable. Is. That is, as described above, the magnetic tape for the microcassette has a narrow width and low mechanical strength, and runs in an extremely narrow place in a small cassette, so back tension is difficult to apply. Therefore, it can be said that the difficulty of ensuring the surface property and running property of the magnetic tape is supported because the necessary frictional property must be imparted while having the slip property.

According to this embodiment, a magnetic tape is specified.
The value T ₁ of the downstream tension gauge G ₂ when the back tension of 0.1 Newton is applied to the upstream tension gauge G ₁ while traveling at 23.8 mm / sec is 0.6 Newton or less, and the back tension is increased. the value T ₂ of the downstream tension gauge G ₂ when reduced 2% of the tape speed Te is not more 0.5 Newtons or more, T ₂
/ T ₁ should be 1.4 or higher. If the friction coefficient of the magnetic tape satisfying this range is provided, the running property and durability, which are the weak points of the magnetic tape for microcassette, can be improved. This effect is particularly great when used for magnetic tapes of microcassettes for answering machines, which are frequently used repeatedly.

The same result as above was obtained in the experiment on the magnetic tape in which the lubricant was not contained in the magnetic layer and the same amount of the lubricant was applied to the surface of the magnetic layer instead.

<Embodiment 2 (Embodiment of the Second Invention)> This embodiment is an example of a magnetic tape for a compact cassette. The cross-sectional structure of the magnetic tape according to the present embodiment is the same as that of the first embodiment, as shown in FIG.

Then, seven kinds of sample tapes H to N shown in Table 5 below were prepared, and these sample tapes were made of vinyl chloride resin, polyester resin and polyurethane resin in the same manner as in Example 1. A magnetic coating material in which magnetic powder of γ-Fe ₂ O ₃ is dispersed in a blended binder resin is applied on a polyethylene terephthalate base film.

[0075]

[0076]

In the preparation of the magnetic coating material and the magnetic tape, this composition was mixed in a ball mill for 48 hours, and then 5 parts by weight of a polyisocyanate curing agent was added, and further 30
The components were mixed and coated on a polyethylene terephthalate film having a thickness of 12 μm so that the thickness after drying would be 6.5 μm. After drying, it was cut into 3.81 mm width to obtain a magnetic tape.

[0078] These sample tapes, as well as in the Example 1, the measurement apparatus shown in FIG. 3, T _1,
The value of T ₂ was measured to determine T ₂ / T ₁ . The measurement results are as shown in Table 6 below.

[0079]

After the above measurement, each of the two compact cassettes (see FIG. 9) assembled with these sample tapes, one of them is a small tape recorder (trade name Walkman WM-R707 manufactured by Sony Corporation: represented by reference numeral WM).
The other one is a cassette deck (Hitachi brand name DW-2 with the plastic tape path guide described above.
20: Represented by the symbol PGD. ) Is used to measure the initial wow and flutter, and also the Sony tape recorder TC-
Tape output after running 100 times using K555EST (10
(kHz-20dB) was measured. Each sample tape is 60
It is a magnetic tape for minute recording.

Wow and flutter were measured by the following method. Recording (3 KHz) in advance with the above tape recorder, and playing using a cassette deck (TC-K555EST manufactured by Sony Corp.) with less wow and flutter in particular, normal wah
Measure with a flutter meter. Therefore, the measured wow and flutter value is a total value including the wah and flutter specific to the regenerator. The measurement results are as shown in Evaluation 7 below.

[0082]

FIGS. 5 and 6 are the same as FIG. 1 in the first embodiment.
4 is a graph in which the relationship between T ₁ or T ₂ and wow and flutter is obtained from the above measured values in accordance with the preparation procedure of. FIG. 7 is a graph showing the relationship between T ₁ or T ₂ and the reduction in reproduction output. There is a request to reduce wow and flutter to about 0.2% or less.

The following can be understood from FIGS. 6 to 7.

Both wow and flutter and output decrease tend to be smaller as T ₁ is smaller, and smaller as T ₂ is larger. Small tape recorder WM reduces wow and flutter 0.2%
In order to achieve the following, T ₂ should be 0.5 Newton or more. For T _1, from the curve of T ₁ is at first glance appear to be possible to increase become variable, a curve of T _2, wow and flutter, and output reduction is the smallest sample tape N T
To ₁ 0.45 Newton, T ₁ 0.47 Newton large sample tape L is slightly T ₁ is, wow and flutter, and output reduction becomes both large.

From this, T ₁ is wow and flutter,
It is considered that it has a strong influence on both of the output reduction (especially the output reduction). Therefore, it is desirable that T ₁ is 0.45 Newton or less of the sample tape N that gives the best result. Further, from FIG. 6, in order to suppress wow and flutter to 0.2% or less using the cassette deck PGD having the plastic tape path guide, it is preferable to set the value of T ₂ / T ₁ to 1.2 or more.

Although the embodiments of the present invention have been described below, various modifications can be added to the above embodiments based on the technical idea of the present invention.

For example, a top coat layer made of a lubricant may be provided on the magnetic layer, and the friction coefficient may be adjusted by both the lubricant in the magnetic layer and the amount of the lubricant in the top coat layer.

The present invention can also be applied to, for example, a magnetic tape in which a magnetic layer made of a metal magnetic thin film is formed on a non-magnetic support and a hard protective film is formed on this magnetic layer. is there. In this case, since the lubricant cannot be internally added to the metal magnetic thin film, the lubricant is applied to the outermost surface.

[0090]

As described above, in the magnetic recording medium according to the first invention, the tension T ₁ when running while giving a back tension of 0.1 Newton is 0.6 Newton or less, and the back tension is increased. The tension T ₂ when the traveling speed is reduced by 2% is 0.5 Newton or more, and the value of T ₂ / T ₁ is 1.4 or more. Therefore, an appropriate back tension is applied, and the compact and small back is provided. Even when it is used for a micro-cassette where it is difficult to apply tension, good running performance and durability are guaranteed, and reliability is high.

Further, the magnetic recording medium according to the second aspect of the present invention is such that T ₁ is 0.45 newtons or less, T ₂ is 0.5 newtons or more, and the value of T ₂ / T ₁ is 1.2 or more. The running performance is apt to be unstable due to friction or slip, for example, recording and / or recording such as a small tape recorder or a cassette deck having a plastic guide.
Even when used in a regenerator, it runs stably with a good balance of tension. As a result, especially when used in compact cassettes, wah
The inconvenience of increased flutter is eliminated, and for example, output reduction due to repeated use is eliminated, and durability is guaranteed.

[Brief description of the drawings]

FIG. 1 shows T ₁ , T ₂ and T according to a first embodiment of the present invention.
₃ is a graph showing the relationship between ₂ / T ₁ and output reduction and damage.

FIG. 2 is a bar graph showing values of each sample tape.

FIG. 3 is a schematic view of an apparatus for measuring the back tension and the tape tension.

FIG. 4 is an enlarged sectional view of the magnetic tape.

FIG. 5 is a graph showing the relationship between T ₁ , T ₂ , T ₂ / T ₁ and wow and flutter in the small tape recorder according to the second embodiment of the present invention.

FIG. 6 shows T ₁ , T ₂ , T ₂ / T ₁ and wah in a cassette deck having the same plastic tape path guide.
It is a graph which shows the relationship with flutter.

FIG. 7 is a graph showing the relationship between T ₁ , T ₂ , T ₂ / T ₁ and output reduction.

FIG. 8 is a sectional view of a microcassette.

FIG. 9 is a sectional view of a compact cassette.

FIG. 10 is an enlarged cross-sectional view showing a general structure of a magnetic tape.

[Explanation of symbols]

 1, 1A, 1B ... Magnetic tape 3, 5 ... Main roller 4a, 4b, 6a, 6b ... Followed roller 7, 8 ... Tension 9 ... Magnetic head 11, 12, 31, 32・ ・ ・ Reels 13, 33, 35 ・ ・ ・ Guide pins 14, 34 ・ ・ ・ Guide rollers 15, 35 ・ ・ ・ Leaf springs 16, 36 ・ ・ ・ Pads 18A, 38, 38 '・ ・ ・ For capstan insertion Through hole 18B ... Through hole for inserting guide pin on deck side 19, 39, 39 '... Opening 20 ... Tape guide 21 ... Non-magnetic support 23 ... Magnetic layer 26 ... Lubrication Agent layer 30 ・ ・ ・ Micro cassette 40 ・ ・ ・ Compact cassette

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yuko Abe 6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation

Claims (10)

[Claims] 1. In a magnetic recording medium having a magnetic layer, the tension T ₁ when running while giving a back tension of 0.1 Newton is 0.6 Newton or less, and the back tension is increased to reduce the running speed by 2%. A magnetic recording medium having a tension T ₂ of 0.5 Newton or more and a value of T ₂ / T ₁ of 1.4 or more. 2. The magnetic recording medium according to claim 1, further comprising a magnetic layer on a non-magnetic support, and a lubricant is internally added and / or applied to the magnetic layer. 3. The magnetic recording medium according to claim _1, wherein the tape tensions T ₁ and T ₂ are adjusted by the average plane roughness Ra of the magnetic layer and / or the amount of lubricant added. 4. The magnetic recording medium according to claim 1, which is for a microcassette. 5. The tension T ₁ when traveling while giving a back tension of 0.1 Newton is 0.6 Newton or less, and the tension T ₂ when increasing the back tension to reduce the traveling speed by 2% is 0.5 Newton. A cassette containing a magnetic recording medium having a value of T ₂ / T ₁ of 1.4 or more. 6. A magnetic recording medium having a magnetic layer, wherein the tension T ₁ when running while giving a back tension of 0.1 Newton is 0.45 Newton or less, and the back tension is increased to reduce the running speed by 2%. A magnetic recording medium having a tension T ₂ of 0.5 Newton or more and a value of T ₂ / T ₁ of 1.2 or more. 7. The magnetic recording medium according to claim 6, wherein a magnetic layer is provided on a non-magnetic support, and a lubricant is internally added and / or applied to the magnetic layer. 8. The magnetic recording medium according to claim 6, wherein the tape tensions T ₁ and T ₂ are adjusted by the average plane roughness Ra of the magnetic layer and / or the amount of the lubricant added. 9. The compact cassette for a cassette according to claim 6.
The magnetic recording medium described in 1. 10. The tension T ₁ when traveling while giving a back tension of 0.1 Newton is 0.45 Newton or less, and the tension T ₂ when increasing the back tension to reduce the traveling speed by 2% is 0.5 Newton. The above is the cassette containing the magnetic recording medium having a value of T ₂ / T ₁ of 1.2 or more.