JPH0652630B2 - Transparent cassette liner - Google Patents

Description

The present invention relates to a transparent cassette liner for holding a magnetic tape.

[Conventional technology]

Generally, as a cassette liner that holds a magnetic tape stored in a compact cassette, a micro cassette, a video cassette, or the like, recently, even a customer's request for transparency and fashionability is added, and abrasion resistance, The development of materials with excellent smoothness is urgently needed.

Therefore, polyester resin has been attracting attention as a material satisfying these required properties, but this resin has a large friction coefficient and produces abnormal noise, and scratches on the sliding surface due to long-term use. Since a whitening phenomenon occurs, a method of applying silicone oil to the surface is adopted to reduce the friction coefficient of this resin. However, such a method is not sufficient, and there is a drawback that the silicone oil layer peels off and the coefficient of friction returns to the original value of the resin with use for a long time. Also, as a resin different from the polyester resin,
Ultra high molecular weight polyethylene with excellent sliding properties is sometimes used, but this resin has an extremely low melt viscosity,
The compression molded product is skived into a sheet with a knife and then rolled to increase transparency, but it is impossible to eliminate irregular reflection due to the traces of the blade during skiving, and transparency is insufficient. It is not insignificant, and there is a large change with time in the dimensions due to internal stress after punching to the dimensions of the holding sheet by rolling, and the sliding characteristics of ultra-high density polyethylene are not sufficient, and the waist strength is also high. Such a method has not been put into practical use because it has many drawbacks such as weakness.

[Problems to be solved by the invention]

As described above, the conventional technique has a problem in that a transparent cassette liner that satisfies not only abrasion resistance, smoothness, and the like but also economy is not yet put into practical use.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention adopts a means for a transparent cassette liner in which a fluoropolysiloxane film is formed on the surface of an activated transparent polyethylene phthalate film. The details will be described below.

In general, the surface of a biaxially stretched transparent polyethylene terephthalate film is inactive and has poor adhesiveness, so it is not necessary to say pretreatments such as degreasing and washing, and for example, physical treatment such as corona discharge, plasma etching, and hot alkali. It is well known that a chemical surface treatment is applied.
For the surface activation of the transparent polyethylene terephthalate film in the present invention, these known methods may be appropriately used, and the specific method is not particularly limited.

Next, the fluoropolysiloxane in the present invention has the general formula Those represented by are preferred. Where Y and Z are -C
H = CH ₂ , CH _{2 d} OH or It is preferable to select R from the viewpoint of durability of the coating, but R may be used. R is an alkyl group, an alkenyl group, an aryl group, or even if a hydrogen atom directly bonded to a carbon atom of these hydrocarbon groups is partially substituted with a halogen atom such as chlorine, bromine, or fluorine, or a cyano group. Good. The W is _{CH 2} d _R f, -OCH _{2
d R f, -OCF 2 OC 3} F 6 e OC 3 F 7, -O
CF ₂ OC ₂ F _{4 e} OCF _{2 f} OCF _{3 and the} like are preferable, and R _f is a linear or branched polyfluoroalkyl group having 3 to 21 carbon atoms. Furthermore, a is 0 to 2
00, b are 0 to 100, and c is an integer of 0 to 50,
a, b and c do not become 0 at the same time, and it is desirable for a / b to be 1 or more and 5 or less that a, b and c are integers of 0 to 10 to exert excellent performance.

A coating solution in which such a fluoropolysiloxane is uniformly dissolved in a halogen-based organic solvent (for example, 1,1,2-trichlorotrifluoroethane) which is a soluble solvent to a concentration of 0.01 to 5.0% by weight is prepared. It is prepared and applied to the surface of the activated transparent polyethylene terephthalate film. The coating method is not particularly limited and may be a general-purpose method such as a dipping method, a spray method, a brush coating method, a roll coater method and a curtain coater method. A film thickness of at least 0.01 μm is usually required to form a uniform film on the substrate film surface, and it is desirable that the film thickness be about 0.1 μm or more in consideration of a certain life. However, if the film thickness is made thicker than necessary, the unreacted fluoropolysiloxane may adversely affect the magnetic tape as the mating material, cause dust, etc. to adhere to the surface, or impair properties. Since it will be disadvantageous in terms of (cost), 10 μm or less,
It is preferable to set 5 μm or less as a guideline. One of the important characteristics of the cassette liner is its antistatic property. Therefore, even if an antistatic agent is appropriately mixed in the coating liquid or the base film, it does not hinder the present invention.

〔Example〕

A biaxially stretched polyethylene terephthalate film (thickness: 50 μm) subjected to corona discharge was dipped from one end in a coating solution in which fluoropolysiloxane was dissolved in a fluorine-containing solvent (CFC R ₁₁₃ ) to a concentration of 0.5% by weight. , 50 per minute
The film was successively pulled up at a constant speed of mm, baked at about 70 ° C. for 1 hour and dried to obtain a transparent film having a film having a thickness of about 1.0 μm. The optical characteristics of this film and the change with time (stability) in the coefficient of friction were measured, and the results are summarized in the table together with the type of film-forming substance. Here, the optical characteristics are measured by a turbidimeter (made by Nippon Denshoku Co., Ltd.), and the friction coefficient is measured on the magnetic surface of the magnetic tape and the resin surface of the base material. Each material was measured using a radial type tester (NTT Toyo Bearing Co., Ltd.) under a load of 50 g and an operating speed of 4.8 cm / sec. Compared with the value for 3 hours, the one with a small difference (fluctuation) is good (marked with ◯) and the one with a relatively large difference is bad (×).
The stability of the coefficient of friction was judged by the two-level evaluation (mark). The tester used to measure the coefficient of friction was 0.7
The above values cannot be measured.

Instead of the fluoropolysiloxanes in the above examples, dimethylpolysiloxane (referred to as Comparative Example 1) and methylphenylpolysiloxane (referred to as Comparative Example 2) were used, respectively, or such poly A transparent film was prepared in the same manner as in Example except that no siloxane was used (this is referred to as Comparative Example 3), and exactly the same optical characteristics and changes in friction coefficient with time were measured and shown in the table. I also wrote it down. Comparing the numerical values shown in the table, the friction coefficient in Comparative Examples 1 and 2 increases (due to peeling of the coating) over time and is not stable, and Comparative Example 3 has a large friction coefficient from the beginning. , Increased with time (immeasurable) and the stability was extremely poor, while the example showed very good results.

〔effect〕

As described above, it is obvious that the transparent cassette liner of the present invention is excellent in all respects including friction and wear characteristics, smoothness, optical characteristics, and economical efficiency. It can be said that the significance is extremely large.

Claims (1)

[Claims] 1. A transparent cassette liner comprising a fluoropolysiloxane film formed on the surface of an activated transparent polyethylene terephthalate film.