JP3373043B2 - Magnetic tape cassette - 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 tape cassette, and more particularly to a magnetic tape cassette suitable for a small cassette deck.

[0002]

2. Description of the Related Art In recent years, the outdoor use of magnetic recording media has increased, and many small decks that are convenient to carry have come to be seen. Especially for audio tapes,
The popularity of small cassette decks called headphone stereos is remarkable. In particular, in order to promote miniaturization of such decks, we are promoting miniaturization of each used component and reduction of the number of components. For this reason, the motor for driving the tape is becoming smaller, and as a result, the torque of the motor is becoming smaller. In other words, generally, in a deck having a low tape feeding force of 40 gf or less for the capstan-pinch roller pulling force, the sliding characteristics between the magnetic layer and the head and the base surface and the guide cannot be explained especially in a low humidity environment. It was found to produce wow and flutter fluctuations.

One of the causes of such wow and flutter is various frictions in the tape running system.
Examples of friction in the tape traveling system include friction between a friction sheet and an end surface of a tape (rolled ball) wound around a hub, friction between a magnetic layer and a head, friction between a back layer and a guide, and the like. Various studies have been conducted to reduce these frictions.

For example, in Japanese Utility Model Laid-Open No. 61-3583, an attempt is made to improve discharge noise by specially processing the surface of a slippery sheet (friction sheet) to reduce its surface electrical resistance (Rs). The device is described. Japanese Unexamined Patent Publication No. 63-78389 relates to a static elimination sheet which is attached to a tape pad to remove static electricity of a tape running system and is used in contact with the tape. The static elimination sheet shows different Rs as the static elimination sheet. In addition, the Rs value is defined and the manufacturing method thereof is disclosed.

In JP-A-60-70519, a running layer is provided by providing a conductive layer between a non-magnetic support and a magnetic layer and defining Rs of the magnetic layer and Rs of the back layer within a predetermined range. It discloses a magnetic recording medium having excellent electromagnetic conversion characteristics with good dropout, no flicker to the fixed cylinder of the deck, and less dropout. Japanese Unexamined Patent Publication No. 1-300419 discloses that a conductive layer provided between a non-magnetic support and a ferrite powder magnetic layer uses carbon black having a specific specific surface area and particle size and a non-magnetic acicular insulator. , R
It is said that a magnetic recording medium having a reduced s and excellent electromagnetic conversion characteristics can be obtained.

As described above, conventionally, the research for obtaining excellent running durability relates to the sliding of the friction sheet and the wound ball end surface, the head and the magnetic layer, the base or the back layer and the guide, and the prevention of the deformation of the tape. However, there is no description about the means for improving the fluctuation of wow and flutter peculiar to the deck with small torque as described above,
It has not been possible to find a solution by simply combining these conventional techniques.

On the other hand, if the ferromagnetic powder is made into fine particles in order to improve the electromagnetic conversion characteristics of the magnetic tape, the Rs will increase, which has been more difficult to solve. The present invention has conducted extensive studies to improve the fluctuation of the wow and flutter, and as a result, by controlling the Rs of the surface of the friction sheet in contact with the end surface of the magnetic tape winding ball and the magnetic layer Rs of the magnetic tape, the capstan is particularly improved. It has been found that a magnetic recording medium exhibiting excellent runnability can be obtained even when used in a low humidity environment by a deck having a low carrying force of 40 gf or less for the pulling force of a pinch roller.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a magnetic recording medium which has excellent runnability in a low-carrying power deck in a low humidity environment and has reduced wow and flutter fluctuations. To do.

[0009]

The above object of the present invention is to provide a magnetic tape cassette in which a friction sheet is brought into contact with an end portion of a magnetic tape wound around a reel so that end faces of wound magnetic tape are aligned. The surface electric resistance of the wound ball end face side surface of the friction sheet is 1 × 10 ⁸ to
1 × 10 ¹¹ Ω / sq, and the surface electric resistance of the magnetic layer surface of the magnetic tape is 5 × 10 ^{7 to} 5 × 10 ¹⁰ Ω / s.
q and the ferromagnetic powder contained in the magnetic layer has an average major axis length of 0.10 to 0.30 μm,
This can be achieved by a magnetic tape cassette characterized in that the average minor axis length is 0.010 to 0.050 μm. Preferably, the above object of the present invention can be achieved by a magnetic tape cassette characterized in that the magnetic tape cassette is for audio. Further, the above-mentioned object of the present invention is such that the magnetic layer of the magnetic tape is composed of a plurality of magnetic layers, and the ferromagnetic powder contained in the upper magnetic layer has an average major axis length of 0.10 to 0.30 μm. Yes, average minor axis length is 0.01
0 to 0.050 μm, the upper magnetic layer contains carbon black, and Co-modified FeOx is contained in the lower magnetic layer.
It can be achieved by a magnetic tape cassette characterized by including (x = 1.333 to 1.490). Particularly preferably, the above-mentioned object of the present invention is for a low-torque deck audio device in which the pulling force applied to the magnetic tape by the magnetic tape cassette is 40 gf or less between the capstan and the pinch roller. Can be achieved by The present invention defines and controls each surface of a friction sheet used in a magnetic tape cassette (the surface that contacts the magnetic tape) and each Rs of the magnetic layer of the magnetic tape within a predetermined range to control the average major axis in the magnetic layer. A ferromagnetic powder having a length of 0.10 to 0.30 μm and an average minor axis length of 0.010 to 0.050 μm, that is, 35 to 60 m ² in terms of _BET specific surface area (S _BET ).
It is possible to provide a magnetic tape cassette which can use a ferromagnetic powder finely divided into particles / g and can suppress wow and flutter fluctuation even in a low humidity environment and low torque. In the present invention, the average major axis length and the average minor axis length of the ferromagnetic powder present in the magnetic layer are taken out from the magnetic layer without damaging the ferromagnetic powder, and a TEM electron micrograph is taken, The major axis length and the minor axis length are average values measured using an image analyzer. In the present invention, the method of taking out the ferromagnetic powder from the magnetic layer is not particularly limited as long as the above conditions are satisfied, but for example, in the case of curing with polyurethane and a polyisocyanate curing agent, it can be decomposed to a monomer level by amine decomposition. It is decomposed, and by this, vinyl chloride, vinyl acetate, etc. are also solubilized, and the ferromagnetic powder can be taken out from the magnetic tape.

INDUSTRIAL APPLICABILITY The present invention can be suitably used in a low torque deck in which the tensile force applied to the magnetic tape is 40 gf or less, particularly 20 to 30 gf between the capstan and the pinch roller. The mechanism by which the present invention can suppress wow and flutter fluctuation even in a low humidity environment and low torque is considered as follows.

When the tape is run, the tape winding ball is charged with electric charges due to sliding between the guide of the cassette shell and the magnetic tape base surface and sliding between the tape winding end surface and the friction sheet. Especially in a low humidity environment, it is difficult for the charged electric charge to leak, and when the tape separates from the winding ball during running, the base surface and the magnetic layer surface stick to each other due to electrostatic attraction, causing a momentary displacement of the running speed and detection as wow and flutter fluctuation. .
By setting the surface electric resistance of the magnetic layer and friction sheet within an appropriate range, the electric charge charged on the winding ball quickly leaks through the friction sheet, so electrostatic attraction between the base surface and the magnetic layer surface during running It is thought that this can be prevented and wow and flutter fluctuations will disappear.

The surface of the friction sheet having Rs controlled by the present invention is the surface side which comes into contact with the edge portion of the magnetic tape, and in the present invention, this Rs is 1 × 10 ⁸ -1.
× 10 ¹¹ Ω / sq, preferably 1 × 10 ^{8 to} 5 × 10 ^10.
Ω / sq, more preferably 1 × 10 ⁸ to 1 × 10 ¹⁰ Ω /
Let sq. Here, the mechanical contact relationship between the friction sheet and the edge portion of the magnetic tape can basically take various forms, but it suffices to have a magnetic tape holding mechanism in a conventionally known magnetic tape cassette. .

If the Rs is 1 × 10 ¹¹ Ω / sq or more, the effect of the present invention cannot be achieved. The means for controlling the Rs of the friction sheet to be less than 1 × 10 ¹¹ Ω / sq is not particularly limited, and a conventionally known method can be applied.
For example, as this method, an antistatic agent may be kneaded into the resin forming the friction sheet, or the antistatic agent may be overcoated on the surface of the friction sheet. Antistatic agents are conductive powders such as carbon black and graphite (only when kneading), cationic surfactants such as quaternary amines, acidic groups such as sulfonic acid, sulfuric acid, phosphoric acid, phosphoric acid ester, carboxylic acid, etc. Anionic surfactants including, and natural surfactants such as saponin are used.
A lubricant such as silicone is preferably used in combination with the antistatic agent. Rs of friction sheet
The lower the value is, the more preferable it is, but if the amount of overcoat or kneading amount of the antistatic agent is increased in order to achieve this, the tape winding end surface and the friction sheet stick to each other due to excessive antistatic agent bleeding out during long-term storage. It is not preferable to make it smaller than 10 ⁸ Ω / sq.

As the material of the friction sheet used in the present invention, polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), synthetic paper and the like can be used, but PET is preferable from the viewpoint of versatility and cost. Also, the friction sheet used has an embossed surface, a curled surface, or a textured surface to prevent the winding disorder of the end surface of the magnetic tape winding ball. ing.

R of the magnetic layer of the magnetic tape used in the present invention
s is 5 × 10 ^{7 to} 5 × 10 ¹⁰ Ω / sq. It is preferably 5 × 10 ⁷ to 1 × 10 ¹⁰ Ω / sq, and more preferably 5 × 10 ^{7 to} 5 × 10 ⁹ Ω / sq. 5 x 10 ¹⁰
If it is higher than Ω / sq, the desired effect cannot be obtained.
As means for controlling Rs of the magnetic layer within the predetermined range,
There is no particular limitation. For example, R of the friction sheet
The same means as the control method of s can be mentioned.

Particularly, in the present invention, as the ferromagnetic powder, Co-modified FeOx (x = 1.333 to 1.490) is used.
It has been found for the first time that Rs is easy to control when is selected. The modification means that Co is doped and that it is adhered. INDUSTRIAL APPLICABILITY The magnetic tape of the present invention is suitable for audios, and is particularly used as a high position tape having a magnetic layer of a single layer or multiple layers and a normal position tape.
Here, the high position is a tape recorded and reproduced with a time constant of 70 μs (TYPE II) of the cassette deck, and the normal position is 120 μ of the time constant of the cassette deck.
s (TYPE I) means a tape recorded and reproduced. A mode example of the magnetic tape cassette of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view of a main part of a magnetic tape cassette 1 of the present invention, and FIG. 2 is a perspective view of a friction sheet 5 arranged in the magnetic tape cassette 1.

As shown in FIG. 1, a magnetic tape cassette 1
Is a rotatably supported hub 3 on which a magnetic tape 4 is wound via friction sheets 5 in cassette halves 2a and 2b. As shown in FIG. 2, the friction sheet 5 is a polyurethane resin sheet having a substantially rectangular shape that is formed in a wavy shape in the left-right direction of the cassette, and is an elliptical hole corresponding to a pair of hub holes 8 provided in the cassette half. 6 and a positioning hole 7 are provided.

The wound balls of the magnetic tape 4 are friction sheets 5 arranged on the inner walls of the cassette halves 2a and 2b.
It is deployed and held in between to prevent winding disturbance of the magnetic tape 4,
It has a structure that protects both balls of the tape and the tape running property. Here, Rs of each surface of the friction sheet on the side in contact with both end faces of the wound ball is 1 × 10 ⁸ to
1 × 10 ¹¹ Ω / sq, and Rs on the magnetic layer surface is 5
Since it is adjusted to × 10 ^{7 to} 5 × 10 ¹⁰ Ω / sq, wow and flutter fluctuations are further prevented.

In the magnetic recording medium of the present invention, a conventionally known structure can be applied to the structure of the magnetic layer provided on the non-magnetic support. For example, the magnetic layer is composed of a binder, a ferromagnetic powder, and other optional additives, but the kinds and proportions of the composition components thereof are basically arbitrary, and the layer structure may be a single layer or two or more layers. And a non-magnetic layer may be provided between the magnetic layers, if desired. When the magnetic layer is composed of two or more layers, the layer farthest from the non-magnetic support is called the upper layer, and the other layers are called the lower layers.

As described above, the ferromagnetic powder used in the present invention has an average major axis length of 0.10 to 0.30 μm and an average minor axis length as the size of the state contained in the magnetic layer. It is necessary to use fine particles having a particle diameter of 0.010 to 0.050 μm, that is, 35 to 60 m ² / g in terms of _BET specific surface area (S _BET ). This is because the size of the ferromagnetic powder as a raw material changes in the range such as kneading even in this range. The average major axis length and the average minor axis length of the ferromagnetic powder in this magnetic layer can be measured, for example, by immersing the magnetic tape in acetone, peeling the magnetic layer, and then using n-butylamine to remove the resulting magnetic layer with an amine. After decomposing and removing the binder, then washing and dispersing the sample, sieving with a copper mesh with a collodion film, taking a TEM electron micrograph,
As described above, there is a method of measuring using an image analysis device. Examples of the ferromagnetic powder used in the present invention include γ-Fe ₂ O ₃ , Co-γ-Fe ₂ O ₃ and FeOx.
(X = 1.33 to 1.5, preferably 1.333 to 1.
490), Co-modified FeOx (x = 1.33 to 1.5,
Preferably _{1.333~1.490), Fe 3 O 4,} C
o Modified Fe ₃ O ₄ , CrO ₂ , Fe or Ni or C
Known ferromagnetic powders such as ferromagnetic powder alloys containing o as a main component (75% or more), barium ferrite, and strontium ferrite can be used.

In the case of FeOx and Co-modified FeOx, x =
At 1.5, it is difficult to obtain the target Rs of the magnetic layer. Particularly in the case of a single magnetic layer, x = 1.333 to 1.4
9, preferably 1.380 to 1.490, particularly preferably 1.450 to 1.490. In the case of a multi-layer magnetic layer, it is preferable to use FeOx or Co-modified FeOx in the above range x in at least one of the upper and lower magnetic layers, and it is particularly preferable to use it in the lower layer. The lower layer of the multi-layered magnetic layer is particularly Co-modified Fe.
Ox (x = 1.333 to 1.490, preferably 1.3
80 to 1.490, particularly preferably 1.430 to 1.4
90) is preferable. Further, it is preferable to use Co-modified FeOx for both layers of the multilayer magnetic layer, and in this case, x = 1.40 to 1.500, preferably 1.440 to 1.500, particularly preferably 1. 460-
The range is 1.500. Co modification is Co
It may be a solid solution or contain Co. When making a magnetic recording medium with a single magnetic layer at x = 1.5, it is preferable to dispose a conductive non-magnetic layer between the support and the magnetic layer. Similarly, in the case of barium ferrite or strontium ferrite, it is necessary to dispose a conductive nonmagnetic layer between the support and the magnetic layer.

In the present invention, these ferromagnetic powders have an average major axis length of 0.10 to 0.30 μm, preferably 0.1.
2 to 0.25 μm, particularly preferably 0.12 to 0.22
μm, and the average minor axis length is 0.010 to 0.050 μm
And preferably 0.012 to 0.040 μm, and particularly preferably 0.012 to 0.030 μm. These are 35 to 60 in terms of _BET specific surface area (S _BET ).
It is a ferromagnetic powder finely divided into m ² / g. The ferromagnetic powder having the specified average major axis length and average minor axis length is contained in the single-layer magnetic layer in an amount of 85 to 100% by weight, preferably 95 to 100% by weight, based on the total ferromagnetic powder. Further, in the multi-layer magnetic layer, it is preferable to mix the upper layer of the magnetic layer with a ferromagnetic powder having a specific average major axis length and average minor axis length in the same proportion as in the case of the single-layer magnetic layer. And, in the other layer, that is, the lower layer, the average major axis length is 0.30 to
0.60 μm, preferably 0.30 to 0.55 μm
m, and the average minor axis length is 0.040 to 0.130 μm, preferably 0.040 to 0.120 μm. In terms of S _BET 25~35m ² / g, preferably preferred for the use of those 26~30m ² / g are compatible surface resistivity and the bias noise of the magnetic layer.

S _BET is the value of the specific surface area measured by the BET method. The carbon black used in the magnetic layer or conductive layer (non-magnetic layer) of the present invention may be a furnace for rubber, thermal for rubber, black for color, acetylene black, or the like. The average particle size of carbon black used in the magnetic layer is preferably 5 to 80 n.
m, particularly preferably 10 to 60 nm, and 0.5 to 10% by weight, preferably 1.0 to 5.0% by weight, of the ferromagnetic powder is preferably contained. When the average particle size is larger than 80 nm, it becomes difficult to obtain the target Rs of the magnetic layer.
However, from the viewpoint of running durability, carbon black having an average particle size of 80 nm to 300 nm may be contained in an amount of less than 0.5% by weight based on the ferromagnetic powder in combination with the above carbon black. In the case of a multilayer magnetic layer structure, the lower layer may or may not contain carbon black, but the upper layer preferably contains carbon black. When carbon black is included in the lower layer, the average particle size is 5 to 20n.
m is 0 to 10% by weight of the ferromagnetic powder, preferably 0.
The electromagnetic conversion characteristics and R of the magnetic layer should be kept to 2.0% by weight.
It is preferable because both s can be satisfied.

Specific examples of the carbon black used in the present invention include those manufactured by Cabot: BLACKPEARLS.
2000, 1300, 1000, 900, 800, 70
0, VALCAN XC-72, Asahi Carbon Co., Ltd .: # 8
0, # 60, # 55, # 50, # 35, manufactured by Mitsubishi Kasei: # 2400B, # 2300, # 900, # 650,
Examples include # 40, # 30, and # 10B.

The abrasives used in the magnetic layer include α-alumina, β-alumina, silicon carbide, chromium oxide, cerium oxide, α-iron oxide, corundum, artificial diamond, silicon nitride, silicon carbide, titanium carbide, and oxide. Known materials having a Mohs hardness of 6 to 10, preferably 7 to 10, such as titanium, silicon dioxide, and boron nitride, are used alone or in combination.

Specific examples of the abrasive include AKP-20, AKP-30, AKP-50 and HI manufactured by Sumitomo Chemical Co., Ltd.
T-50, Nippon Kagaku Kogyo KK: G5, G7, S-1, Toda Kogyo TF-100, TF-140, 100E.
D, 140ED and the like. When the abrasive used in the present invention has a multi-layered structure, it is of course possible to change the type, amount and combination of the lower layer and the upper layer and to use them properly according to the purpose. It is not necessary to use the abrasive for the lower layer if necessary. . These abrasives may be dispersed in a binder in advance and then added to the magnetic paint. The number of abrasives present on the magnetic layer surface and the magnetic layer end surface of the magnetic recording medium of the present invention is 5 to 130 particles / 100 μm ² , preferably 5 to 9
0/100 μm ² or more.

As the binder used in the present invention, a conventionally known thermoplastic resin, thermosetting resin, radiation curable resin, reactive resin or a mixture thereof is used.
Examples of the resin component include vinyl chloride copolymers (for example, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-acrylic copolymer, vinyl chloride). -Acrylonitrile copolymer, etc.), ethylene-vinyl acetate copolymer,
Vinyl chloride-based copolymer having polar group such as —SO ₃ Na or —OSO ₃ Na and epoxy group introduced therein, cellulose derivative such as nitrocellulose resin, acrylic resin, polyvinyl acetal resin, polyvinyl butyral resin, epoxy resin, phenoxy. resins, polyurethane resins (e.g., polyester polyurethane resins, -SO ₃ Na or -OSO ₃ Na and polyurethane resins which polar group is introduced, and polycarbonate polyurethane resins, polycaprolactone polyurethane resin) can be mentioned.

When a curing agent is used, a polyisocyanate compound is usually used. The polyisocyanate compound is usually selected from those used as curing components such as polyurethane resins. Further, when the curing treatment is carried out by electron beam irradiation, a compound having a reactive double bond (urethane acrylate) can be used.

The binder used in the present invention is used in the range of 5 to 50% by weight, preferably 10 to 35% by weight, based on the ferromagnetic powder. When a vinyl chloride resin is used, it is preferably used in a combination of 5 to 30% by weight, a polyurethane resin is used in a range of 3 to 30% by weight, and a polyisocyanate is used in a range of 0 to 20% by weight. In particular,
It is preferable that the binder comprises a vinyl chloride / vinyl acetate copolymer and polyester polyurethane, and the total amount of the binder is 15 to 30% by weight based on the ferromagnetic powder. Further, if necessary, polyisocyanate may be added to each coating liquid in an amount of 1 to 10% by weight based on the ferromagnetic powder to carry out the crosslinking treatment.

The thermoplastic resin constituting the non-magnetic support used in the present invention is not particularly limited to polyester, polyolefin, polyamide, polyphenylene sulfide, etc., but particularly polyester, especially ethylene terephthalate, ethylene α, β- It is desirable to use at least one structural unit selected from bis (2-chlorophenoxy), ethane-4,4'-dicarboxylate and ethylene 2,6-naphthalate units as a main constituent component.

The non-magnetic support used in the present invention may be subjected to corona discharge, plasma treatment, easy adhesion treatment, heat treatment, dustproof treatment, etc. before being coated with the coating liquid. The F-5 value in the tape running direction of the non-magnetic support is preferably 5 to 50 Kg / mm ² , and the F-5 value in the tape width direction is preferably 3 to 30 Kg / mm ² .

The total thickness of the non-magnetic support used in the present invention is 5 to 20 μm, preferably 6 to 16 μm. Next, regarding the method for manufacturing the magnetic tape used in the present invention,
It will be described below. All raw materials such as ferromagnetic powder, binder, carbon black, abrasive, antistatic agent, lubricant and solvent may be added at the beginning or in the middle of any step. In addition, individual raw materials may be divided and added in two or more steps. For example, kneading step of polyurethane,
You may divide and input in a dispersion process and the mixing process for viscosity adjustment after dispersion.

In order to achieve the object of the present invention, it goes without saying that conventionally known manufacturing techniques are used as a part of the steps, but in the kneading step, those having a strong kneading force such as a continuous kneader or a pressure kneader. By using, the high Br of the magnetic recording medium of the present invention can be obtained. When a continuous kneader or a pressure kneader is used, all or a part of the ferromagnetic powder and the binder (however, 30% by weight or more of the total binder is preferable) and 15 to 500 parts by weight based on 100 parts by weight of the ferromagnetic powder. It is kneaded with a solvent in the range of parts. Regarding these kneading treatments, JP-A-1-106338
And JP-A-64-79274.

In the coating step of the present invention, coating is carried out by using a conventionally known technique (gravure coating, roll coating, blade coating, extrusion coating device, etc.). Also,
If desired, the multilayer magnetic layer may be used by using the simultaneous multilayer coating method as shown in JP-A-62-212993. Regarding these, for example, "Latest coating technology" issued by Sogo Gijutsu Center Co., Ltd. (May 1983)
May 31st) can be used as a reference.

In order to obtain the magnetic recording medium of the present invention, it is preferable to perform strong orientation, and 1000 to 3000 G
It is preferable to use a (Gaussian) solenoid and a cobalt magnet of 2000 to 5000 G in combination, and it is preferable to further provide an appropriate drying step in advance before orientation so that the orientation after drying becomes the highest. Further, a heat-resistant plastic roll such as epoxy, polyimide, polyamide, or polyimide amide is used as the calendering roll. Further, it is also possible to perform processing by using metal rolls. The treatment temperature is preferably 80 to 100 ° C. The linear pressure is preferably 200 to 500 Kg / cm, more preferably 300 to 450 Kg / cm, and the speed is 20 m /
The range is from minutes to 700 m / min.

[0036]

EXAMPLES The present invention will be described more specifically by showing examples. In each example, “part” means “part by weight” unless otherwise specified. Example 1 (Single Layer Type) A magnetic coating liquid for a single layer type high position tape was prepared according to the following formulation.

Co-deposited FeOx 100 parts (x: Table 1, Hc = 650 Oe, S _BET (m ² / g): Table 1, average major axis length (abbreviated as major axis length), average minor axis length (minor axis) Abbreviated as length): Table 1) Vinyl chloride-vinyl acetate-vinyl alcohol copolymer 12 parts Composition ratio = 91: 3: 6, degree of polymerization = 400 Polyester polyurethane resin 3 parts Carboxyl group = 10 ⁻⁴ mol / g content α -Alumina (particle size = 0.2 μm) 6 parts Carbon black (particle size = 30 nm) 2 parts Myristic acid modified silicone 1 part Isostearic acid modified silicone 1 part Myristic acid 1 part Butyl acetate 100 parts Methyl ethyl ketone 70 parts Cyclohexanone 30 parts Each of the above After kneading the components with a continuous kneader, they were dispersed using a pin type sand mill. To the obtained dispersion, 3 parts of polyisocyanate compound was added, and butyl acetate was added to 20 parts.
In addition, a magnetic coating solution was obtained by filtering using a filter having an average pore size of 1 μm.

The obtained magnetic coating solution was applied onto a polyethylene terephthalate support having a thickness of 7 μm and a center line average roughness of 30 nm so that the thickness of the magnetic layer after drying was 4.6 μm, and the layer was wet. After drying with a cobalt magnet having a magnetic force of 3000 G and a solenoid having a magnetic force of 1500 G, the temperature of the metal roll was 90 ° with a 7-stage calender composed of a metal roll and a plastic roll.
The treatment was carried out under the condition that the temperature was 300 ° C. and the pressure (line pressure) was 300 Kg / cm, and slit to a width of 3.8 mm to produce an audio tape. The slit audio tape was wound in a cassette for 135 m (C90) to obtain a compact audio cassette. Here, the friction sheet used is a textured sheet. Rs is the Rs of the surface that contacts the end surface of the magnetic tape.

Table 1 shows the measurement results of fluctuations in wow and flutter of the compact audio cassettes obtained in the above Examples and Comparative Examples, bias noise and Rs of the magnetic layer and friction sheet. The above measurement conditions are as follows. Wow and flutter fluctuation Input level to compact audio cassette obtained-
A 3 kHz signal is recorded at 10 dB (0 dB = 250 nwb / m). This cassette is used as a headphone stereo JCK-50 (pulling force 25 gf) manufactured by Sharp Corp.
Measure the wow and flutter by running at 10 ° C and 10%. Wow and flutter is made by National Wow Frameter V
UNWTD (unweighted) with P-7751A
It is measured under the rms condition of. The wow and flutter fluctuations were determined as follows from the wow and flutter measurement results shown on the recording chart.

S: Wow and flutter fluctuation is less than 0.1% =
Excellent A: Wow and flutter fluctuation is 0.1 to 0.2% of the wow and flutter base level = good B: Wow and flutter fluctuation is 0.2 to 0.4% of the wow and flutter base level = practically No problem C: Wow and flutter fluctuation is 0.5 to 0.7% against the wow and flutter base level = practically impossible D: Wow and flutter fluctuation is 0.7% or more against the wow and flutter base level = poor The determinations C and D are levels at which wow and flutter fluctuations are detected in terms of hearing.

Bias Noise The obtained compact cassette tape is recorded without a signal by applying only a bias current, and this portion is reproduced and the output after passing through an auditory sense correction filter (JISC curve) is used as bias noise. No internal standard tape made by Fuji Photo Film
It was set to dB. The magnetic layer is measured according to Rs JIS C 5565. However, the applied voltage is 50V, the measurement time is 10 seconds, the measurement environment is 23 ° C,
50%. As the measured value, the value shown on the measuring machine was used as it was without area conversion. Storage Adhesion Test Method Test by storing in an in-cassette state at 85 ° C for 4 hours in a dry environment. The evaluation is based on whether there is stickiness. Yes:
The end face of the roll and the friction sheet stick together. None: The end face of the winding ball and the friction sheet do not stick together.

The Rs sheet of the friction sheet is placed on the insulator and measured using a Mitsubishi Yuka high resistance high resistor. The applied voltage is 50 V, the measurement time is 50 seconds, and the measurement environment is 23 ° C. and 70%. As the measured value, the value indicated by the measuring machine was used as it was.

[0043]

[Table 1]

An example in which the Rs of the magnetic layer is 5 × 10 ¹⁰ Ω / sq or less, the Rs of the friction sheet is less than 1 × 10 ¹¹ , and the ferromagnetic powder has a specific major axis length, minor axis length, and specific surface area. Indicates that wow and flutter fluctuation is small and bias noise is small. On the other hand, the comparative example is sample 9
It can be seen that the samples Nos. To 13 have good bias noise, but the wow and flutter fluctuation is large, and the samples 14 to 15 have the wow and flutter fluctuation improved, but the bias noise is not improved. Sample 16 has a bad bias noise,
Sample 17 has storage stickiness and sample 18 does not improve wow and flutter variation.

Example 2 (multi-position high position tape) A multi-layer high position tape magnetic coating solution was prepared according to the following formulation. Upper layer coating liquid Co-deposited FeOx 100 parts (x: Table 2, Hc = 700 Oe, specific surface area: Table 2, major axis length, minor axis length: Table 2) Vinyl chloride-vinyl acetate-vinyl alcohol copolymer 12 parts Composition Ratio = 91: 3: 6, degree of polymerization = 400 Carbon black (particle size = 30 nm) 2 parts α-alumina (particle size = 0.5 μm) 1 part Methyl ethyl ketone / cyclohexanone mixed solvent 30 parts (mixing ratio is 1 by weight) 1) Polyester polyurethane resin 3 parts Myristic acid 1 part Isostearic acid modified silicone 2 parts Butyl acetate 100 parts Methyl ethyl ketone 53 parts The above composition was charged into a double-arm open kneader, and after kneading and mixing, dispersed with a sand grinder. .

3 parts of a polyisocyanate compound (Nippon Polyurethane: Coronate L) was added to the obtained dispersion and the mixture was filtered using a filter having an average pore size of 1 μm to prepare an upper layer coating solution. Lower layer coating liquid Co-deposited FeOx 100 parts (x: Table 2, Hc = 580 Oe, specific surface area: 26 m ² / g, particle size (major axis diameter) 0.27 μm, acicular ratio = 8) Vinyl chloride-vinyl acetate- Vinyl alcohol copolymer 12 parts (composition ratio = 86: 13: 1, degree of polymerization = 380, amino group 5 × 10 ⁻⁶ mol / g content) Abrasive (α-alumina, particle size = 0.5 μm) 1 part Methyl ethyl ketone / cyclohexanone mixed solvent 22 parts (mixing ratio is 1: 1 in weight ratio) Polyester polyurethane resin 3 parts Butyl acetate 100 parts Methyl ethyl ketone 73 parts After kneading the above components with a continuous kneader, disperse using a pin type sand mill, It was filtered using a filter having an average pore size of 1 μm to obtain a lower layer coating liquid.

The upper layer coating liquid and the lower layer coating liquid thus obtained were simultaneously coated on a non-magnetic support so that the upper layer was 2 μm and the lower layer was 3 μm, and an audio cassette was obtained by the same method as in Example 1. The characteristics of the various audio cassettes obtained above were evaluated in the same manner as in Example 1.

[0048]

[Table 2]

The Rs of the magnetic layer is 5 × 10 ¹⁰ Ω / sq or less, the Rs of the friction sheet is less than 1 × 10 ¹¹ , and the ferromagnetic powder in the upper layer has a specific major axis length, minor axis length and specific surface area. In the example, it can be seen that wow and flutter fluctuation is small and bias noise is small. On the other hand, in the comparative example, the samples 10 to 12 have good bias noise, but the wow and flutter fluctuation is large, and the samples 13 to 15 are
It can be seen that the wow and flutter fluctuation is improved, but the bias noise is not improved. Further, it can be seen that in Sample 16, the wow and flutter fluctuation is not improved.

Example 3 (multi-position normal position tape) A multi-layer normal position tape magnetic coating solution was prepared according to the following formulation. Upper layer coating liquid Co deposited γ-Fe ₂ O ₃ 100 parts (Hc = 500 Oe, specific surface area: Table 3, major axis length, minor axis length: Table 3) Vinyl chloride-vinyl acetate-vinyl alcohol copolymer 12 parts Composition Ratio = 91: 3: 6, degree of polymerization = 400 Carbon black (particle size = 30 nm) 2 parts α-alumina (particle size = 0.5 μm) 1 part Methyl ethyl ketone / cyclohexanone mixed solvent 30 parts (mixing ratio is 1 by weight) 1) Polyester polyurethane resin 3 parts Myristic acid 1 part Isostearic acid modified silicone 2 parts Butyl acetate 100 parts Methyl ethyl ketone 53 parts The above composition was charged into a double-arm open kneader, and after kneading and mixing, dispersed with a sand grinder. .

3 parts of a polyisocyanate compound (made by Nippon Polyurethane: Coronate L) was added to the obtained dispersion, and the mixture was filtered using a filter having an average pore size of 1 μm to prepare an upper layer coating solution. Lower layer coating liquid The Hc of the Co-modified FeOx of the lower layer coating liquid of Example 2 was 380.
The same composition as in Example 2 was used except that Oe and x were changed to those shown in Table 3.

The above lower layer coating liquid and upper layer coating liquid were used in Example 2
In the same manner as above, the composition was coated on a non-magnetic support and treated in the same manner as in Example 2 to prepare various magnetic tape cassettes, and evaluated in the same manner as in Example 2.

[0053]

[Table 3]

The Rs of the magnetic layer is 5 × 10 ¹⁰ Ω / sq or less, the Rs of the friction sheet is less than 1 × 10 ¹¹ , and the ferromagnetic powder in the upper layer has a specific major axis length, minor axis length, and specific surface area. In the example, it can be seen that wow and flutter fluctuation is small and bias noise is small. On the other hand, in the comparative example, the samples 5 to 8 have good bias noise, but the wow and flutter fluctuation is large, and the samples 9 to 11 show that the wow and flutter fluctuation is improved, but the bias noise is not improved.

[0055]

INDUSTRIAL APPLICABILITY The present invention uses a fine ferromagnetic powder having a specific major axis length, minor axis length, and specific surface area (S _BET ) of 35 to 60 m ² / g, and a magnetic tape edge portion of a friction sheet. The surface electric resistance of the surface contacting with is 1 × 10 ⁸ to 1 × 10
Since it can be controlled to ¹¹ Ω / sq and the surface electric resistance of the magnetic tape magnetic layer surface can be controlled to 5 × 10 ^{7 to} 5 × 10 ¹⁰ Ω / sq, electromagnetic conversion of the magnetic tape cassette can be performed even when using a small cassette deck with low torque. It is possible to effectively prevent the fluctuation of the wow and flutter especially in a low humidity environment while maintaining good characteristics.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part of an example of a magnetic tape cassette of the present invention.

FIG. 2 is a perspective view of an example of a friction sheet arranged in the magnetic tape cassette of FIG.

[Explanation of sign] 1 Magnetic tape cassette 2a cassette half 2b cassette half 3 hubs 4 magnetic tape 5 friction sheet 6 oval holes 7 Positioning hole 8 hub holes

─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-57-147171 (JP, A) JP-A-4-238177 (JP, A) JP-A-60-70519 (JP, A) JP-A-3- 292618 (JP, A) JP 5-189751 (JP, A) JP 5-205438 (JP, A) Actual development Sho 59-1173 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) G11B 23/087 509 G11B 5/70 G11B 5/714 G11B 5/716

Claims (4)

(57) [Claims] 1. A magnetic tape cassette in which a friction sheet is brought into contact with an edge portion of a magnetic tape wound around a reel to align a wound ball end surface of the magnetic tape, the surface of the friction sheet facing the wound ball end surface. The electric resistance is 1 × 10 ⁸ to 1 × 10 ¹¹ Ω / sq, and the surface electric resistance of the magnetic layer surface of the magnetic tape is 5 × 10 ⁷ to
A 5 × ¹⁰ 10 Ω / sq, and the ferromagnetic powder contained in the magnetic layer, the average major axis length is 0.10 to 0.
30 μm, average minor axis length is 0.010 to 0.050
A magnetic tape cassette characterized by being μm. 2. The magnetic tape cassette according to claim 1, wherein the magnetic tape cassette is for audio. 3. The magnetic layer of the magnetic tape comprises a plurality of magnetic layers, and the ferromagnetic powder contained in the upper magnetic layer comprises:
The average major axis length is 0.10 to 0.30 μm, the average minor axis length is 0.010 to 0.050 μm, carbon black is contained in the upper magnetic layer, and C is contained in the lower magnetic layer.
The magnetic tape cassette according to claim 1, which contains o-modified FeOx (x = 1.333 to 1.490). 4. The magnetic tape cassette according to claim 1, wherein the pulling force applied to the magnetic tape by the magnetic tape cassette is for audio of a low torque deck in a range of 40 gf or less between the capstan and the pinch roller. .