JPS58146064A - Transparent friction plate for cassette - Google Patents

Abstract

PURPOSE:To make a friction plate antistatic by using a plastic film which is made of a thermoplastic synthetic resin mixed with an antistatic agent and a lubricant of 0.02-1wt% against the synthetic resin and formed by biaxial stretchching. CONSTITUTION:A wound magnetic tape 3 rotates by making its side contact with a friction plate 11. Pellets of an antistatic raw material are manufactured by mixing 1pt.wt. antistatic agent which is prepared by adding 8mol of ethylene oxide to lauryl amine, with 100pts.wt. polypropylene having a melt index of 2.0. Master pellets are produced by adding and mixing 2pts.wt. silicone resin to 100pts.wt. raw material pellets, and then, by performing melt extrusion and cooling on the mixture. Then 10pts.wt. master pellet is mixed with 90pts.wt. antistatic raw material pellet, and the mixture is subjected to melt extrusion and biaxial stretching. Thereafter, corona discharge treatment is performed on both surfaces of the stretched product, and thus, a friction plate of polypropylene having a thickness of 50mu is obtained.

Description

[Detailed description of the invention] This invention relates to a transparent friction plate for cassettes.

A cassette that stores a magnetic tape has a friction plate attached to the inner surface of the two cases that make up the cassette, and the side surface of the wound tape rotates while contacting the friction plate, allowing the magnetic tape to run smoothly. , and prevents irregular winding.

To briefly explain an example of the structure of a cassette using FIG. 1, a cassette 1 consists of two symmetrically molded cases 2.
The case 2 includes an annular protrusion 5 for rotatably supporting the IJ-1v4 around which the magnetic tape 3 is wound, and a shaft for rotatably supporting a guide roller 6 for changing the running direction of the magnetic tape 3. a roller pin 7, a guide pin 8 for changing the running direction, a plurality of big holes 9 for combining and fixing the two cases 2, and a magnetic head hole 10 for the magnetic head to come into contact with the running magnetic tape 8. etc. 1 are integrally molded. And K.

A friction plate 11 having approximately the same length as the case 2 is attached to the center of the inner surface of the case 2.
1, the side surface of the wound magnetic tape 3 is rotated while being in contact with the magnetic tape 3. This friction plate 11 is
As shown in FIG. 2, the annular protrusion 5Vc of the case 2
The fitting hole to be fitted.

12, and a square hole 13 for collecting urine in a rolled state;
In addition, a longitudinal protrusion 14 is formed.

The contact surface of the friction plate that is in contact with the side surface of the rotating tape is required to have good slipperiness.
This slipperiness tends to decrease as the number of times the magnetic tape is run and used increases, and when used for a long time, the frictional resistance increases and the winding torque increases, causing wow, flutter, etc., and deteriorating the playback sound quality. However, the vehicle may even be stopped from running.

Therefore, the contact surface of the friction plate is required to have good sliding properties and to maintain running durability.

On the other hand, antistatic properties are required to prevent the generation of static electricity due to contact with the magnetic tape and to prevent dust from adhering during assembly. Therefore, the friction plate is required to have antistatic properties.

Conventionally, commonly used friction plates that meet the above requirements have been made by impregnating, mixing, or laminating carbon black and a lubricant to paper or unstretched polyolefin films. It is something.

The conventional friction plate mentioned above is black and opaque, and is hidden by a display paper pasted on the outside of the case.
Furthermore, the entire winding state of the magnetic tape inside the cassette could not be seen. Therefore, in order to make the entire winding state of the magnetic tape inside the cassette visible, the friction plate must be transparent. Recently, transparent friction plates made of carbon black have been attempted, but all of them lack antistatic properties and have extremely low running durability.

The present invention provides a transparent friction plate having antistatic properties.

That is, this invention provides a thermoplastic synthetic resin with an antistatic agent,
A transparent friction plate for a cassette is made of a plastic film obtained by biaxially stretching a resin composition in which 0.02 to 1% by weight of a lubricant is mixed with the synthetic resin.

The thermoplastic synthetic resin that is the raw material for the biaxially stretched plastic film in this invention includes olefin resins such as polyethylene and polypropylene, ester resins such as polyethylene terephthalate, amide resins such as nylon 6, other polycarbonate resins, and polycarbonate resins. Examples include acrylic resins, with polypropylene and polyethylene terephthalate being particularly preferred.

The antistatic agents used in this invention are cationic,
Anionic, nonionic, amphoteric, or amphoteric metal salt type antistatic agents, and particularly preferred nonionic antistatic agents include polyoxyethylene alkylamide, polyoxyethylene alkylamine, glycerin fatty acid ester, Examples include polyalkylene gelicols and polyalkylene ethers, and examples of amphoteric metal salt-based antistatic agents include sulfonic acid metal salt derivatives. The above antistatic agent is 0.1 to 5% by weight, especially 0.5 to 2% by weight based on the synthetic resin.
is preferable; if it is less than 0.1% by weight, a sufficient antistatic effect cannot be obtained, and if it exceeds 5% by weight, problems such as a decrease in compatibility with the resin and a decrease in the thermal stability of the resin composition occur. be.

Furthermore, the lubricants used in the present invention include silicone resins, fluororesins, paraffins, hydrocarbons such as chlorinated paraffins, higher alcohols such as stearyl alcohol and cetyl alcohol, other fatty acids, fatty acid esters, fatty acid salts, and polyesters. Ethers are exemplified, and silicone resins such as addition reaction-type polysiloxanes and fluororesins such as perfluoroalkyl compounds are particularly suitable.

The mixing amount of the silicone resin and fluororesin is 0.02 to 1% by weight, preferably 0.0.5 to 0-5% by weight, based on the thermoplastic synthetic resin.

If it is less than 0.02% by weight, the dynamic friction coefficient becomes large and the torque during winding of the running magnetic tape becomes large, and if it exceeds 1% by weight, the surface feels slimy, and in this case also, the torque during winding of the running magnetic tape becomes large. Torque increases.

In this invention, a resin composition obtained by kneading an antistatic agent and a lubricant with the thermoplastic synthetic resin is melt-extruded, and the formed unstretched film is biaxially stretched by a conventional method.

Since the lubricant in the resin composition is a small amount of solid matter as described above, it may be difficult to mix it uniformly.

In this case, a predetermined amount of lubricant is mixed with some thermoplastic synthetic resin and melted and extruded using an extruder to produce master pellets, and this master pellet is mixed with the remaining thermoplastic synthetic resin to evenly distribute the lubricant. It is preferable to mix them. The lubricant content in the master pellets is preferably 1 to 5% by weight based on the thermoplastic synthetic resin,
There are no particular restrictions.

One or both sides of the biaxially stretched plastic film obtained as described above may be subjected to corona discharge treatment.

This corona discharge causes the antistatic agent and lubricant contained in the film to ooze out onto the film surface, thereby further improving the antistatic properties and lubricity.

When polypropylene is used as the raw material thermoplastic resin for the biaxially stretched film, it is difficult to mold the above-mentioned protrusions by stamping, and even if the protrusions are formed, the protrusions are easily removed by running the magnetic tape. Easy to disappear. Therefore, this motion table can be made by laminating a biaxially oriented polyester film with good embossing moldability on the opposite side that does not come into contact with the magnetic tape winding side line to form a laminated film of polypropylene film and polyester film. preferable.

The friction plate of the present invention is transparent and allows the entire winding state of the magnetic tape inside the cassette to be seen through. In addition, since it has antistatic properties, it prevents running performance from being deteriorated due to charging during running, and prevents dust from adhering to it when assembling a cassette or running a magnetic tape.

This invention will be explained in detail below.

Example 1 An antistatic raw material pellet was produced by mixing too many parts by weight of polypropylene with a melting index of 2.0 with 1 part by weight of an antistatic agent in which 8 moles of ethylene oxide was added to laurylamine. 2 parts by weight of silicone resin (trade name: Toshiba Silicone YF3860) was added and mixed, and the mixture was melt-extruded using an extruder with a diameter of 60 cm.
It was cooled to form Master Pellets '114. 10 parts by weight of this master pellet and the above antistatic raw material pellet 9
0 parts by weight, mixed and melt extruded, and further biaxially stretched by a conventional method, and then subjected to corona discharge treatment on both sides to a thickness of 5.
A friction plate made of a 0μ polypropylene film was obtained.

Example 2 A friction plate having a thickness of 50 μm was obtained in the same manner as in Example 1, except that 2 parts by weight of the Magtar pellet of Example 1 and 98 parts by weight of the antistatic raw material pellet were mixed and melt-extruded.

Example 3 A biaxially stretched polypropylene film having a thickness of 25 μm was produced in the same manner as in Example 1 above, and a biaxially stretched polyethylene terephthalate film having a thickness of 25 μm was adhered to one side of this polypropylene film.

Example 4 1 part by weight of polyethylene glycol with a molecular weight of 2000 is added to 100 parts by weight of polyethylene terephthalate whose intrinsic viscosity is 0.62 when measured at 30 centimeters using a mixed solution of phenol/tetrachloroethane (6/4). ,
1 part by weight of sodium dodecylbenzenesulfonate and 0.3 parts by weight of a silicone resin (trade name KF-96, manufactured by Shin-Etsu Chemical Co., Ltd.) were mixed, mixed and dried in a blender at 120°C, and the resin composition was melt-extruded and extruded in a conventional manner. Stretched biaxially,
Then, both surfaces thereof were subjected to corona discharge treatment to obtain a friction plate made of polyethylene terephthalate and having a thickness of 50 μm.

Comparative Example Thickness 5 with a low silicone resin content was prepared in the same manner as in Example 1, except that 0.5 parts by weight of Master Benz) of Example 1 and 99.5 parts by weight of antistatic raw material Benz) were mixed.
A friction plate of 0μ was obtained.

The performance of each of the above Examples, Comparative Examples and commercially available products is shown in the table below.

The haze in the table above is the value expressed as the percentage of scattered light transmittance (%) to total light transmittance (%) measured with a haze meter (manufactured by Toyo Seiki Co., Ltd.) in accordance with J.E.S. 6782. The higher the value, the lower the transparency.The ability to prevent banding is determined by measuring the charging voltage using a static honest meter (manufactured by Sagetsu Shokai) at 25°C and 60% RH, and determining the attenuation half-life of the charging voltage. The value is expressed in seconds (seconds), and the smaller the value, the better the antistatic property.

The coefficient of dynamic friction is based on Ako TM-D 1894 and is based on untreated polyester film (trade name E5001, thickness 7
The coefficient of kinetic friction between the easy-slip surface of each sample and the reference film surface of 5 μm (manufactured by Toyobo Co., Ltd.) is shown.

Durability was tested using a commercially available cassette, replacing various friction plates with two friction plates that touch both sides of the magnetic tape, and using a reproducing machine (National RQ, -L).
6) Run the magnetic tape back and forth at high speed, detect the relative value of torque during running of the magnetic tape using current load, and calculate the current load value at each time when the number of reciprocations is 50.100.200.300.400. The relative current load values of the current load values at each number of runs of each sample piece with respect to the initial current load value of the above-mentioned commercial product are shown in the graph of FIG. ○ mark in the table u 400
Those marked with an X do not generate wow or flutter after 400 times, and the quality of the reproduced sound deteriorates.

As seen in the table above, the friction plate of the present invention is not only transparent, but its performance is almost the same as that of the commercially available product (black). In addition, the comparative example containing a small amount of silicone resin has a lower antistatic property, a slightly larger coefficient of dynamic friction, and a significantly poorer running durability.

[Brief explanation of the drawing]

FIG. 1 is a front view of a normal cassette, FIG. 2 is a perspective view of an example of a friction plate, and FIG. 3 is a graph showing the relationship between the number of fast feed reciprocating runs and the relative current load value in a durability running test. 11: Friction plate. Figure 1

Claims (1)

[Scope of Claims] [l] Consisting of a plastic film obtained by biaxially stretching a resin composition in which a thermoplastic synthetic resin is mixed with an antistatic agent and a lubricant in an amount of 0.02 to 1% by weight based on the synthetic resin. A transparent friction plate for cassettes characterized by the following. [2] A patent claim in which the thermoplastic synthetic resin is polypropylene or polyethylene terephthalate! i5.1f
fi 5th. Transparent friction plate for cassettes described in f. [3] The transparent cassette plate according to claim 1 or 2, wherein the lubricant is a silicone resin. [4] The transparent friction plate for a cassette according to any one of claims 1 to 3, wherein at least one side of the plastic film is subjected to a corona discharge treatment. [5] The transparent friction for cassettes according to any one of claims 1 to 4, wherein a polyethylene terephthalate film is laminated on one side of a biaxially oriented polypropylene film containing an antistatic agent and a silicone resin. Board.