JP2001184831A - Magnetic tape cassette - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic tape cassette using a friction sheet which is reduced in the friction generated between a magnetic tape and the friction sheet and the electrification by the friction, is extremely little in the peeling of an antistatic agent with which the sheet is impregnated and is extremely excellent in durability and slidability. SOLUTION: The purposes described above are achieved by the magnetic tape, which has a cassette body formed of upper and lower halves, a pair of take-up hubs rotatably housed in this cassette body and wound with the magnetic tape and the friction sheet interposed between a pair of these take-up hubs and at least one of the upper half and the lower half and has a surface electric resistance value of 1×109 to 1×1010 Ω, and the magnetic tape cassette which uses the friction sheet made of porous polyethylene having a surface electric resistance value of 1×109 to 1×1010 Ωand/or a coefficient of dynamic friction of 0.15 to 0.25.

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 provided with an improved friction sheet for preventing electrification and ensuring slidability of a magnetic tape.

[0002]

2. Description of the Related Art As is well known, a magnetic tape cassette is
After fixing each end of the long magnetic tape, a pair of winding hubs around which the magnetic tape is wound are housed in the cassette body (upper half and lower half), and at least recording and reproduction of the magnetic tape is performed. When loaded into the device, so that the magnetic tape can contact the magnetic head,
Only a part of the magnetic tape stretched between the pair of winding hubs is exposed to the outside of the cassette body.
When the magnetic tape cassette is loaded into the recording / reproducing apparatus, the magnetic tape cassette is stretched between the winding hubs, and a part of the magnetic tape exposed from the cassette body abuts the magnetic head in the apparatus, and the winding hub is rotated, As the magnetic tape runs and slides on the magnetic head in the apparatus, the magnetic head records information on the magnetic tape and reproduces information from the magnetic tape.

In an audio magnetic tape cassette or the like, when the magnetic tape cassette is loaded into a recording / reproducing apparatus, a part of the magnetic tape exposed from a cassette main body is stretched between winding hubs and is attached to a magnetic head in the apparatus. Abut,
When the take-up hub is rotated and the magnetic tape runs and slides on the magnetic head in the apparatus, the magnetic head records information on the magnetic tape and reproduces information from the magnetic tape. In a device such as a video magnetic tape cassette having a front cover for protecting the tape, when the magnetic tape cassette is loaded into the recording / reproducing device, the front cover is magnetically driven by a mechanism in the device in conjunction with the cassette. The tape is rotated to the position where the tape is released, and a part of the magnetic tape stretched between the winding hubs is exposed from the cassette body. Then, the take-up hub is rotated, the magnetic tape runs, and slides in contact with the magnetic head in the apparatus, so that the magnetic head records information on the magnetic tape and reproduces information from the magnetic tape. It has become.

If the magnetic tape moves up and down while the magnetic tape is running, the magnetic tape does not properly contact or slide with the magnetic head, so that proper recording / reproduction cannot be performed, and there is a possibility that other troubles may occur. is there. Therefore, it is necessary to suppress the vertical movement during the running of the magnetic tape, improve the regulation accuracy of the running position of the magnetic tape, and stabilize the running performance. For this reason, conventionally, in a magnetic tape cassette using a flangeless type winding hub, a friction sheet is interposed between the winding hub around which the magnetic tape is wound and the cassette body (upper and lower halves) to form a magnetic tape. The running position (height) of the magnetic tape is regulated to adjust the running position of the magnetic tape. Further, a shaping portion (squeezing) is provided on the friction sheet, and the running position (height) of the magnetic tape is defined by the height of the shaping portion.

[0005] By the way, in a magnetic tape usually used for a magnetic tape cassette, there is a problem of durability of a member which comes into contact with the tape edge, for example, a friction sheet, depending on the type of a magnetic material and a base material. The magnetic tape usually has a surface electric resistance of 1 × 10 ⁵ Ω to 1 × 10 ⁷ Ω, but when such a magnetic tape runs or vibrates, it is integrally molded with a cassette with an ABS resin or the like. There is a problem that there is a fear that the charged resin is rubbed and charged, causing an influence on a head of the recording / reproducing apparatus and a failure such as sticking of a magnetic tape such as a friction sheet to a mechanical component.

[0006] On the other hand, the friction sheet is usually formed of high-density polyethylene (high-density PE) or the like, and its electric resistance is very large, about 10 ¹⁶ Ω.
It is about. For this reason, the sheet itself is easily charged, and the sheet is easily charged by the contact or sliding contact between the sheet and the inner wall surface of the cassette, the magnetic tape or the winding hub, and dust is easily attached. This is even more problematic because the magnetic tape and the take-up hub are in sliding contact with the sheet, causing peeling charging.

[0007]

Therefore, there is a need for improving the durability of the friction sheet and reducing the surface electric resistance. Here, the durability of the friction sheet is the scraping with the tape edge. The scraping of the sheet by the tape edge can be prevented by adopting a porous polyethylene sheet as the sheet, and the durability of the friction sheet can be reduced. The problem can be solved.

By the way, in order to reduce the surface electric resistance of the friction sheet, utilizing the fact that the sheet is porous, the sheet is immersed in an antistatic agent such as a mixture containing a quaternary ammonium salt or the like. It is conceivable that the sheet is impregnated with an antistatic agent by coating or the like. When the antistatic agent is used to reduce the surface electric resistance of the sheet, the surface electric resistance generally decreases as the concentration of the antistatic agent increases.
However, the antistatic agent only impregnates, fits, and adheres to the micropores formed on the sheet surface. Therefore, the antistatic agent peels off with a slight impact,
There was a problem that it could be missing. The amount of the missing matter increases as the concentration of the antistatic agent increases, and the missing matter adheres to the magnetic tape and causes contamination of the tape and further the cassette, impairing the appearance and product performance, There is a problem in that the quality of the magnetic tape itself and the magnetic tape cassette is deteriorated.

On the other hand, the value of the surface electric resistance of a magnetic tape housed in a magnetic tape cassette is naturally determined due to restrictions on a base material, a magnetic material and the like to be used. Therefore, while using the same magnetic tape as before, the amount of missing antistatic agent was reduced, and the magnetic tape was prevented from sticking without impairing the antistatic effect on the friction sheet. There has been a need for a magnetic tape cassette that reduces scraping of the edge itself.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a magnetic tape cassette using a predetermined magnetic tape, wherein the friction and friction generated between the magnetic tape and the friction sheet are provided. An object of the present invention is to provide a magnetic tape cassette using a friction sheet excellent in durability and slidability, in which electrification caused by the frictional sheet is reduced and the antistatic agent impregnated in the sheet is very little peeled off.

[0011]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, the surface electric resistance and the dynamic friction coefficient of the friction sheet used in the conventional magnetic tape cassette have been reduced. It has not been optimized for the properties of the magnetic tape used in the tape cassette, and by optimizing it for the magnetic tape described above, the impregnated charging The inventors have found that a magnetic tape cassette having an extremely small amount of the inhibitor can be obtained, and completed the present invention.

That is, the magnetic tape cassette of the present invention has a cassette main body formed by connecting an upper half and a lower half in a lid-like manner, and is rotatably housed in the cassette main body, and has a magnetic tape wound thereon. A pair of winding hubs; a pair of winding hubs; and a friction sheet interposed between at least one of the upper half and the lower half. The magnetic tape has a surface electric resistance of 1 × 10 ⁵ Ω ~
1 × 10 ⁷ Ω, the friction sheet is made of porous polyethylene, and 1 × 10 ⁹ Ω to 1 × 1
It has a surface electric resistance of 0 ¹⁰ Ω.

[0013] The magnetic tape cassette of the present invention further comprises a cassette body formed by connecting an upper half and a lower half in a lid-like manner, and a pair of rotatable magnetic tape wound in the cassette body. And a friction sheet interposed between the pair of winding hubs and at least one of the upper half and the lower half. The magnetic tape has a surface electric resistance of 1 × 10 ^5. Ω ~
The friction sheet may be 1 × 10 ⁷ Ω, the friction sheet may be made of porous polyethylene, and have a dynamic friction coefficient of 0.15 to 0.25.

Here, it is preferable that the friction sheet has the two properties described above.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetic tape cassette according to the present invention will be described in detail below based on preferred embodiments shown in the accompanying drawings.

FIG. 1 is a partially exploded perspective view showing a schematic configuration of an embodiment of a cassette body of a magnetic tape cassette according to the present invention, and FIG. 2 is housed in the cassette body of the magnetic tape cassette shown in FIG. FIG. 1 is an exploded perspective view showing a schematic configuration of an embodiment of a magnetic tape wound around a pair of winding hubs and a friction sheet sandwiching these from both sides. As shown in these drawings, a magnetic tape cassette (hereinafter, simply referred to as a cassette) 10 is formed as a housing by being combined with a lid, and a pair of upper and lower upper halves (upper cassette half) 12 constituting a cassette main body. And a lower half (lower cassette half) 14 (see FIG. 1), and a pair of winding hubs 16 and 16 housed in the cassette body.
And a magnetic tape 18 wound around the pair of winding hubs 16, 16, a space between the winding hubs 16, 16, the magnetic tape 18 wound around them, and the upper half 12, and a pair of magnetic tapes 18. It has winding hubs 16, 16 and friction sheets (hereinafter, also simply referred to as sheets) 20, 20 (refer to FIG. 2) interposed between the lower half 14 and the magnetic tape 18 wound therearound, respectively.

As shown in FIG. 1, a pair of upper halves 1
The second half 2 and the lower half 14 have substantially the same shape, and are provided with a partition wall 26 that divides the hollow interior of the cassette body formed by these into a recording / reproducing area 22 and a hub storage area 24 (in the upper half 12, it is illustrated). Is omitted). A center along the cassette front-rear direction (hereinafter, the recording / reproducing area 22 is defined as a front side with respect to the hub storing area 24) is substantially at the center of both sides of the hub storing area 24 of the pair of upper and lower halves 12, 14. A pair of spindle shaft insertion holes 28, 28 into which a pair of spindle shafts of a recording / reproducing apparatus for rotationally driving the pair of take-up hubs 16, 16 are inserted symmetrically with respect to the line; Insertion hole 2
A pair of hub supporting annular ribs 28a, 28a for rotatably regulating (or supporting) the pair of winding hubs 16, 16 along the inner peripheral edges of the pair of rotation guide rollers 30, 30 at both front ends. And so on. The pair of rotation guide rollers 30 is rotatably supported by a pair of pins 30a erected on the lower half 14, respectively.

In the recording / reproducing area 22 of the pair of upper and lower halves 12, 14, the pair of capstan insertion holes 32, 32 and the pair of cassette positioning holes 34, 34 are symmetrical with respect to the center line. Etc. are perforated. Inside the pair of cassette positioning holes 34, 34 in the recording / reproducing area 22 of the lower half 14, a pair of head pins 36, 36 and the like are erected symmetrically with respect to the above-mentioned center line. Further, in the recording / reproducing area 22, a leaf spring 40, which is a plate-like support member for supporting the pressure pad 38, is provided behind the pair of head pins 36, 36, and a shield plate 42 is provided behind the leaf spring 40. ing. A magnetic head (not shown) of the recording / reproducing apparatus is inserted into the recording / reproducing area 22 from the front of the cassette at the time of recording / reproducing at the front center of the recording / reproducing area 22 of the pair of upper and lower halves 12, 14. A head insertion port 44 is formed.

Then, the magnetic head is inserted into the magnetic head insertion slot 4.
When the magnetic tape 18 is inserted into the recording / reproducing area 22 from the position 4, the tip of the magnetic head is pushed into the cassette 10 together with the pressure pad 38. As a result, the magnetic tape 18 is formed at the tip of the magnetic head 18 by the tension of the magnetic tape 18 stretched between the pair of head pins 36 and 36 and the pressing force of the pressing pad 38 based on the urging force of the leaf spring 40. Head gap). When performing recording / reproducing, the take-up hubs 16 and 16 engaged with the pair of spindle shafts of the recording / reproducing apparatus are driven to rotate, and the magnetic tape 18 is attached to both head pins 36 and
It is stretched around 36, runs while sliding against the magnetic head, and the audio information recorded on the magnetic tape is reproduced, and conversely, the audio information is recorded on the magnetic tape.

As shown in FIG. 2, the magnetic tape 18 is wound around a pair of winding hubs 16,16. Winding hub 1
Reference numeral 6 denotes a tape winding ring 16a provided on the outer periphery, and the side surface thereof is a magnetic tape winding surface. A small piece 17 for fixing an end of the magnetic tape 18 is attached to a part of the tape winding ring 16a. A small-diameter ring 16b is formed on the inner peripheral side of the winding hub 16, and engages with the hub supporting annular rib 28a of the spindle shaft insertion hole 28 of the pair of upper and lower halves 12 and 14,
The winding hub 16 is rotatably supported and the winding hub 1 is supported.
6 is restricted from coming off the position of the spindle shaft insertion hole 28.

Here, the surface electric resistance of the magnetic layer of the magnetic tape 18 used in the present invention is 1 × 10 ⁵ Ω to
1 × 10 ⁷ Ω. The base material, the magnetic material, and the like used for the magnetic tape are not particularly limited as long as the surface electric resistance value is within the above range, and any material may be used as the base material or the magnetic material. Examples of the magnetic material of the magnetic tape used in the present invention include all conventionally known magnetic materials used for conventionally known magnetic tapes. Examples of the magnetic tape used in the present invention include general magnetic tapes in which such a magnetic material is closely adhered to a base material and slit to a certain width. Above all,
After the magnetic tape has been slit, it is preferable that no special coating be applied to the edge of the magnetic tape.

The magnetic tape used in the present invention has a tape
As a base material, there is used a conventional magnetic tape.
All known base materials can be mentioned, but
As a preferable base material, PET (polyethylene tereph
Tarate), PEN (polyethylene naphthalate),
Lamid and the like can be mentioned. As the thickness of the magnetic layer
Is preferably 2 μm to 6 μm, more preferably
Or 2.5 μm to 4 μm. The magnetic tape
Although the lower limit of the thickness is not particularly limited,
m or more. Also, the magnetic tape Yang
Preferably, the cutting rate is 500 kg / mm in the vertical and horizontal directions. ^Two
That is all.

Also, as shown in FIG.
Between the winding hubs 16, 16 around which the tape is wound and the inner wall surface of the cassette 10, that is, between the winding hub 16 and the upper half 12, and between the winding hub 16 and the lower half 12, respectively. Sheets 20, 20 are inserted. These sheets 20, 20 have four small holes 2 perforated respectively.
0a is 4 of the upper half 12 and the lower half 14 shown in FIG.
By fitting the two ribs 12a and 14a,
It is positioned and attached to the upper half 12 and the lower half 14. The seats 20 have a pair of insertion holes 20b, 20b corresponding to the two spindle shaft insertion holes 28, 28 of the upper and lower halves 12, 14, respectively. Furthermore, the friction sheets 20, 20
Each has two shaping portions 20c and 20d in the cassette left-right direction (the direction orthogonal to the front-back direction of the cassette 10). The sheets 20, 20 reduce the sliding resistance when the winding hubs 16, 16 rotate, smoothen the rotation, and support the winding hub 16, on which the magnetic tape 18 is wound by the shaping portions 20c, 20d. It also plays a role in height regulation. In the example described above, the friction sheet 2
0 is a magnetic tape 18 and a pair of take-up hubs 16, 16;
And the upper half 12 and the lower half 14, but the present invention is not limited to this, and may be interposed only in either one.

The friction sheet 2 used in the present invention
0 is made of porous polyethylene. By using such a material, a friction sheet excellent in durability and slidability can be obtained.

The friction sheet 20 has the following 2
It satisfies at least one of the two characteristics, that is, the characteristic relating to the surface electric resistance value and the characteristic relating to the dynamic friction coefficient. As characteristics relating to the surface electric resistance, 1 × 10 ⁹ Ω to 1 ×
It has a surface electric resistance of 10 ¹⁰ Ω.
Within this range, it is possible to prevent the friction sheet from sticking to the magnetic tape or other members,
In addition, it is possible to minimize the loss of the antistatic agent impregnated in the friction sheet. In addition, the preferable range of the surface electric resistance value is 0.2 × 10 ⁹ Ω to
0.8 × 10 ¹⁰ Ω. The characteristic relating to the dynamic friction coefficient is that it has a dynamic friction coefficient of 0.15 to 0.25. Within this range, the friction generated due to the rubbing with the magnetic tape or other members can be kept low, and the antistatic agent impregnated in the sheet can be hardly peeled off. Further, the edge of the sheet or the magnetic tape itself can be hardly scraped. The preferred range of the dynamic friction coefficient is 0.18 to 0.22.

In the present invention, when the magnetic tape cassette has a plurality of friction sheets 20, it is sufficient that at least one satisfies one of the above two characteristics. The friction sheet 20 used in the present invention only needs to satisfy one of the above two characteristics. It is preferable that both properties are satisfied from the viewpoint of effectively suppressing the loss of the antistatic agent impregnated in the sheet and the sticking of the sheet to the magnetic tape.

In order to satisfy the above characteristics, the friction sheet can be impregnated with an appropriate concentration of an antistatic agent. The antistatic agent used is not particularly limited, and for example, a mixture containing a quaternary ammonium salt can be used. Examples of the method of impregnating the friction sheet with the antistatic agent include, for example, an immersion method such as exposing the raw material of the friction sheet to an antistatic agent bath, a method of applying a so-called coater, and the like. The sheet may be modified in advance by performing a pretreatment such as a corona discharge treatment and an ultraviolet treatment.

Here, as a method for measuring the surface electric resistance value of the magnetic tape and the friction sheet, JIS X
6130 was adopted. Next, a method for measuring the dynamic friction coefficient of the friction sheet will be described. First, a test piece of a rectangular sheet having a width of 80 mm and a length of 200 mm was prepared, placed on stainless steel made of SUS420J having a surface roughness (Ra) of 0.3 μm, and a 63 mm side was further placed thereon. Square and the contact surface
A sliding piece, to which a felt specified in JIS L3201 is adhered smoothly, is covered. After setting the sliding pieces, 23
Under a condition of 50 ° C. and a relative humidity of 50%, the specimen was tested at a test speed of 10%.
Start at 0 ± 10 mm and start the test. The coefficient of kinetic friction is calculated as a dynamic friction force from an average load up to a friction distance of 70 mm from a point at which the minimum is passed after the initial maximum load.

Next, the reason why at least one of the friction sheets used in the magnetic tape cassette of the present invention satisfies at least one of the above two characteristics will be described.
This will be described with reference to FIG. FIG. 3 is a diagram showing a relationship between the surface electric resistance value of the friction sheet and the rate of occurrence of sticking between the friction sheet and the magnetic tape. As a friction sheet, a porous polyethylene friction sheet is prepared, and various concentrations of an antistatic agent (ammonium salt) are adjusted so that the surface electric resistance value is 1 × 10 ⁵ Ω to 1 × 10 ¹³ Ω by the above-described measurement method. Mixture) was impregnated on both sides by a dipping method. Next, the base material was aramid, the thickness of the magnetic layer was 2 μm, the total thickness of the tape was 5.6 μm, the width was 4 mm, and the surface electric resistance was 1.0 × 1.
It was prepared a magnetic tape is 0 ⁶ Ω.

A sample of the cassette body provided with each of the friction sheets described above is prepared, and after winding the above-described magnetic tape into the cassette body at a rate of 1 to 4 m / sec for 125 m at a temperature of 23 ° C. and a relative humidity of 50%. The occurrence rate (%) of sticking of the magnetic tape and the peeling rate (%) of the antistatic agent impregnated in the friction sheet were measured, and are shown in FIG. The rate of occurrence of sticking of the magnetic tape is indicated by a hollow circle. In addition, the peeling rate of the antistatic agent was tested eight times for each surface electric resistance value, and each was represented by a symbol of intermediate coating.

Here, sticking of the magnetic tape means a phenomenon in which the magnetic surface of the magnetic tape sticks to a certain surface of the upper and lower sheets or the cassette. The rate of sticking of the magnetic tape (%) refers to the number of samples of the cassette body (5500 rolls).
Is the ratio of the number of turns of the cassette in which the sticking has occurred. Further, the peeling test of the antistatic agent is performed by taking out the magnetic tape from the cassette main body after winding the magnetic tape and visually observing whether or not the peeled material of the antistatic agent is attached to the edge of the magnetic tape. The peeling rate (%) is the ratio of the number of turns of the cassette where the magnetic tape edge has a deposit to the number of samples (100 turns) of the cassette body. The determination as to whether or not the deposit attached to the edge of the magnetic tape is an antistatic agent is determined by FT-IR
This was performed by a transmission method.

As shown in FIG. 3, when the surface electric resistance is 1 × 10 ⁹ Ω to 1 × 10 ¹⁰ Ω, the rate of occurrence of tape sticking can be suppressed to 0.02% or less, and The peeling rate of the antistatic agent can be suppressed to 20% or less.
Further, when the dynamic friction coefficient of a sheet having a surface electric resistance value in this range was measured by the method described above, it was 0.15
0.25. For this reason, by using a friction sheet in this range, the magnetic tape does not stick to the friction sheet without minimizing peeling of the antistatic agent, and without impairing the antistatic effect of the friction sheet. It can be seen that a cassette can be obtained.

Examples of applications of the magnetic tape cassette of the present invention include conventionally known applications such as an audio magnetic tape cassette, a video magnetic tape cassette, and a computer backup magnetic tape cassette. That is, as the magnetic tape cassette of the present invention,
The present invention is not limited to the above-described magnetic tape cassette for audio. For example, a magnetic tape cassette having a front lid and protecting a magnetic tape exposed forward, such as a magnetic tape cassette for video (VHS), an 8 mm cassette,
A magnetic tape cassette of a type having a front lid and a slider for protecting a magnetic tape exposed to the front, such as a digital audio tape cassette (DAT) and a digital data storage (DDS), may be used.

In the case where the state of use is determined, such as a video magnetic tape cassette or an 8 mm cassette, a digital audio tape cassette, or a digital data storage, the take-up hub, the magnetic tape, etc. are placed from below. The supporting side, that is, the lower friction sheet is preferably a porous polyethylene sheet that satisfies one of the above-mentioned two properties, and the lower friction sheet is formed of both of the above two properties. More preferably, the porous polyethylene sheet satisfies the following. This is because the friction sheet on the lower side has a higher frictional force and a higher sliding force than the upper side,
By using such a sheet as the sheet used in the present invention, sticking between the magnetic tape and the sheet can be more effectively prevented, and side effects such as lack of an antistatic agent can be reduced.

As described above, the magnetic tape cassette of the present invention has been described in detail with reference to various embodiments. However, the present invention is not limited to the above-described embodiments, and is not departed from the gist of the present invention. Of course, various improvements and changes may be made.

[0036]

According to the magnetic tape cassette of the present invention,
The friction sheet used is excellent in durability and slidability, and since the surface electric resistance value and dynamic friction coefficient are optimized for the magnetic tape used, there is almost no sticking of the magnetic tape. In addition, the peeling of the antistatic agent and the peeling of the magnetic tape and the friction sheet itself are reduced, so that the product performance is not impaired.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of an embodiment of a cassette main body of a magnetic tape cassette according to the present invention.

FIG. 2 is an exploded perspective view of an embodiment of the magnetic tape wound around a pair of winding hubs and a friction sheet sandwiching these from both sides, which are housed in a cassette main body of the magnetic tape cassette shown in FIG. is there.

FIG. 3 is a diagram showing a relationship between a surface electric resistance value of a friction sheet, a sticking occurrence rate of a magnetic tape, and a peeling rate of an antistatic agent.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Magnetic tape cassette 12 Upper half 12a, 14a Rib 14 Lower half 16 Take-up hub 16a Tape take-up ring 16b Small diameter ring 17 Small piece 18 Magnetic tape 20 Friction sheet 20a Small hole 20b Insertion hole 20c, 20d Shaping part 22 Recording / reproducing area 24 Hub storage area 26 Partition wall 28 Spindle shaft insertion hole 28a Hub support annular rib 30 Rotation guide roller 30a Pin 32 Capstan insertion hole 34 Cassette positioning hole 36 Head pin 38 Pressure pad 40 Leaf spring 42 Shield plate 44 Magnetic head insertion hole

Claims (3)

[Claims] 1. A cassette body formed by connecting an upper half and a lower half in a lid-like manner, a pair of winding hubs rotatably housed in the cassette body and wound with a magnetic tape, The magnetic tape has a pair of winding hubs and a friction sheet interposed between at least one of the upper half and the lower half, and a surface electric resistance value of the magnetic tape is 1 × 10 ⁵ Ω to 1 ×.
10. The magnetic tape cassette according to claim ⁷ , wherein the friction sheet is made of porous polyethylene, and has a surface electric resistance of 1 × 10 ⁹ Ω to 1 × 10 ¹⁰ Ω. 2. A cassette body formed by connecting an upper half and a lower half in a lid-to-lid manner, a pair of winding hubs rotatably housed in the cassette body and wound with a magnetic tape, The magnetic tape has a pair of winding hubs and a friction sheet interposed between at least one of the upper half and the lower half, and a surface electric resistance value of the magnetic tape is 1 × 10 ⁵ Ω to 1 ×.
10. The magnetic tape cassette according to claim ⁷ , wherein said friction sheet is made of porous polyethylene and has a dynamic friction coefficient of 0.15 to 0.25. 3. The friction sheet according to claim 1, wherein said friction sheet is 0.15 to 0.1.
2. The magnetic tape cassette according to claim 1, having a dynamic friction coefficient of 25.