JPS6339996B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tape cassette in which a slippery sheet is provided between a case containing a magnetic tape and the magnetic tape.

Conventionally, in this type of tape cassette, a slippery plastic sheet (hereinafter referred to as a liner sheet) is provided between the inner wall surface of the case and the magnetic tape to reduce the frictional resistance and allow the magnetic tape to run stably. ) are placed. For example, the liner sheet disclosed in Japanese Patent Publication No. 49-46249 is
This is a plastic base filled with lubricant powder such as graphite or molybdenum disulfide. However, this is manufactured by rubbing graphite etc. into the base using a reversing roll while applying pressure and temperature, which makes it difficult to control pressure and temperature to obtain a uniform product. Although the top sheet has excellent lubricity, it has the disadvantage of insufficient abrasion resistance. Furthermore, the liner sheet disclosed in Japanese Patent Publication No. 10484/1984 has hard particles having a Mohs hardness of 5 or more added to a plastic base such as Teflon for the purpose of improving wear resistance. However, in this sheet, the reinforcing effect becomes weak unless a considerable amount of hard particles are added to the base. In other words, if a large amount is added, the particles will exist not only on the surface on the magnetic tape side but also inside and on the back side of the base, reinforcing the base, but if the amount added is small, such a state will not occur.
This is because the particles are not uniformly contained. Moreover,
The surface of the sheet is easily roughened by hard particles, which may damage the magnetic tape, and the lubricity is not sufficient.

The present invention was invented in order to correct the above-mentioned defects, and in the tape cassette mentioned at the beginning, the slippery sheet comprises a sheet-like support and a slippery layer coated on the surface of the support. The lubricating layer is mainly composed of a mixture of a solid lubricant, an abrasion resistance imparting material, and a binder, and the binder is mainly composed of a cellulose resin and a thermoplastic polyurethane resin. This relates to a characteristic tape cassette. With this configuration, the abrasion resistance and lubricity of the coating layer of the slippery sheet, that is, the slippery layer, are improved, and the sheet-like support,
That is, sufficient adhesive strength can be obtained even when applied onto a base. Note that the term "tape cassette" herein refers to a case with a built-in magnetic tape, and includes so-called tape cartridges and the like.

According to the present invention, the abrasion resistance imparting material and the solid lubricant are uniformly mixed in the binder, and are evenly present on the surface of the magnetic tape in particular, so that the abrasion resistance and the solid lubricant are uniformly present on the surface of the magnetic tape. This also improves the magnetic tape's performance, making it possible to run smoothly and stably without damaging the magnetic tape. Furthermore, since the main components of the binder are a cellulose resin and a thermoplastic polyurethane resin, the combination of these resins provides very good adhesive strength, and the slipping layer itself can be made stable.

The solid lubricant used in the present invention is preferably a material that has a layered crystal structure and cleavage between the layers in terms of improving lubricity, and examples include graphite, carbon black, and disulfide. Examples include molybdenum, graphite fluoride, and talc. Among these, graphite, carbon black, and molybdenum disulfide have antistatic properties and are therefore desirable materials for preventing static electricity. Further, the average particle diameter of the solid lubricant used in the present invention is preferably 0.5 to 10 microns, more preferably 1 to 5 microns. That is, if the average particle size is less than 0.5μ, it is too small and the lubricating effect will be poor, and if it exceeds 10μ (especially about
This is because if it exceeds 100μ, it will be too large and difficult to coat onto the base, which will be described later.

In addition, the wear resistance imparting material used in the present invention is preferably a non-magnetic material (abrasive material) with a Mohs hardness of 5 or more in order to improve wear resistance.
Examples include Cr ₂ O ₃ , α-Al ₂ O ₃ , SiC, α-Fe ₂ O ₃ and SiO ₂ . The average particle size of this wear-resistant material is 0.05
The thickness is preferably 5.0μ, more preferably 0.1 to 1.0μ. In other words, if the average particle size is less than 0.05μ, it will be too small and the wear resistance effect will be poor;
This is because if it exceeds 5.0μ, the magnetic tape side is likely to be damaged and it becomes difficult to apply it onto the base, which will be described later.

According to the present invention, the above-mentioned solid lubricant and wear resistance imparting particles are mixed with a binder, and this mixture is applied onto a base to form a lubricating layer. In order to improve the strength, it has been found that it is extremely important to use the above-mentioned cellulose resin and thermoplastic polyurethane resin as a binder.

Usable cellulose resins are cellulose resins that are polymers produced by dehydration condensation of glucose, and are produced by esterification, etherification, nitration reactions, etc. of the three hydroxyl groups (-OH) in glucose anhydride units. Appropriately modified materials are desirable. In this case, on average 1.5 to 2.8 of the three hydroxyl groups,
Preferably, 1.9 to 2.5 of the functional groups are substituted with the functional groups introduced by the above reaction. That is, if the substitution is not made within this range, the solubility in the solvent during coating will decrease. The cellulose resin used in the present invention may be cellulose nitrate, cellulose acetate, cellulose propionate, cellulose acetate butyrate, methyl cellulose, ethyl cellulose, etc. These celluloses are produced by converting the three hydroxyl groups in the glucose anhydride unit into nitroxy groups (-ONO ₂ ) and acetoxy groups (-
OCOCH ₃ ), propionyloxy group (-
OCOCH ₂ CH ₃ ), butyryloxy group (-
Partial substitution with OCOCH ₂ CH ₂ CH ₃ ), methoxy group (-OCH ₃ ), ethoxy group (-OCH ₂ CH ₃ ), etc. is preferable.

Further, as the thermoplastic polyurethane resin that can be used in the present invention, a polyester obtained from a glycol such as 1,4-butanediol and a dicarboxylic acid such as adipic acid and having a hydroxyl group at the end,
Examples include those crosslinked with a diisocyanate compound such as p,p'-diphenylmethane diisocyanate or toluene diisocyanate. In this case, if the reaction is carried out at a ratio of isocyanate groups to hydroxyl groups of 0.99 or less, a stable polymer having hydroxyl groups at the terminals can be obtained. This polyurethane resin is thermoplastic and preferably has a glass transition temperature of 0° C. or lower. For example, Nipporan 2304, Nipporan 2320, Nipporan 3022, Nipporan 5033 (all trade names of Nippon Polyurethane Co., Ltd.), Estane 5701F-1, Estane 5702, Estane 5703, Estane 5707F.
-1, 5710F-1, 5715 (the above are B.F.
(trade name manufactured by Gutsudoritsu) is exemplified.

Next, the ratio of each component of the slipping layer according to the present invention will be described.

First, the amount of the solid lubricant is preferably 60 to 600 parts by weight per 100 parts by weight of the binder. That is,
If the solid lubricant is less than 60 parts by weight, it will be too small and will not be effective in reducing friction and resistance, and if it exceeds 600 parts by weight, a large amount of so-called "powder falling" will occur as the magnetic tape runs. . The amount of wear resistance imparting material is based on 100 parts by weight of solid lubricant.
The amount is preferably 0.2 to 5 parts by weight. That is, if the abrasion resistance imparting material is less than 0.2 parts by weight, the effect of improving abrasion resistance will be poor, and if it exceeds 5 parts by weight, wear will occur on the edge surface of the magnetic tape (the end surface that contacts the slippery layer). It is. Further, it is desirable that the composition of the binder is 20 to 95% by weight of cellulose resin and 80 to 5% by weight of thermoplastic polyurethane resin in order to improve the first adhering property and to maintain a low coefficient of friction. Note that the slipping layer may also contain other components such as a dispersant such as lecithin, an antistatic agent, etc. at the same time.

In addition, when the slipping layer according to the present invention is coated on a base that is a support, for example, a plastic sheet such as polyethylene terephthalate or paper, the thickness of the slipping layer (coating film) is 1 to 20 μm. The thickness is preferably 2 to 10 μm, and more preferably 2 to 10 μm. That is, if the thickness of the slipping layer is less than 1 μm, it will be too thin and its life will be shortened, and if it exceeds 20 μm, it will be difficult to mount it in a cassette from a practical standpoint.

Next, embodiments of the present invention will be described with reference to the drawings.

As an example, a coating material for a slipping layer having the following composition was prepared.

Graphite powder 200 parts by weight Nitrocellulose (H1/8: trade name manufactured by Asahi Kasei Corporation) Thermoplastic polyurethane resin (Estan 5702: trade name manufactured by B.F. Griddrich) 100 parts by weight (total amount) Lecithin (dispersion) 2 parts by weight Cr ₂ O ₃ (Mohs hardness 8-9) 2 parts by weight Methyl ethyl ketone (solvent) 400 parts by weight Toluene (solvent) 400 parts by weight Cyclohexanone (solvent) 400 parts by weight And this paint is shown in Figure 1. As shown, a slippery layer 2 is formed by coating on a polyethylene terephthalate film 1 and drying, thereby creating a liner sheet 3. Specifically, this liner sheet is installed in a tape cassette 4 shown in FIG. Between the upper half 8 and the lower half 9 of the cassette 4, a magnetic tape 7 wound around a reel hub 5 and 6 is built in, and between the inner wall surface of the upper and lower halves 9 and the magnetic tape 7. The above-mentioned liner sheets 3 are arranged respectively. In this case, the liner sheet 3 is placed so that the slippery layer 2 side is close to the magnetic tape 7.

In the above coating composition, when the blending ratio of nitrocellulose and thermoplastic polyurethane resin was varied, the results shown in FIGS. 3A to 3C were obtained.

To explain the measurement method used to obtain these data, first, when measuring the adhesive force in Figure 3A, 1/
A 1/4 inch wide flexible film is adhered to the coated surface (slip layer) of a sample (liner sheet) cut into a 4 inch wide tape, and then this flexible film is pulled in a 180° direction to form a sample. Measure the force required to break the adhesion at the interface between the base film and the paint film. In addition, when measuring the coefficient of dynamic friction shown in Figure 3B, as shown in Figure 4, a sample (liner sheet) cut into a 1/4 inch wide tape was used.
3 is brought into contact with the brass drum 10 over 1/4 circumference, one end of which is attached to the support 11 in a horizontal state, and the other end is lowered vertically to attach the weight W. Then, the drum 10 is moved at a relative speed to the sample 3.
Rotate at 0.75mm/sec, drum 10 and support 1
Tension gauge placed between 1 and weight W
Read the values t ₁ and t ₂ of T ₁ and T ₂ , respectively. The dynamic friction coefficient μd is given by μd=2/πloget ₂ /t ₁ .
In addition, when measuring the amount of powder falling, JISR6001 and
Cut it into 1/4 inch width and hang it on a roller wrapped with #800 wrapping tape specified in JISR6253.
A load of 100 g was applied, and the tape-shaped sample was reciprocated 100 times over a length of 10 cm. Then, the decrease in weight of the sample was measured, and the amount of decrease was defined as the amount of powder falling off.

From the results shown in Figures 3A and 3B, in order to increase the adhesive force to the base and suppress the increase in the coefficient of friction, the binder composition should be 20 to 95% by weight of nitrocellulose and 5% by weight of thermoplastic polyurethane resin. It can be confirmed that it is desirable to select one with a content of ~80% by weight. Regarding wear resistance, as shown in Fig. 3C, in the case of this example in which Cr ₂ O ₃ is added, powder falling off is greatly reduced and the resistance is improved compared to that in which Cr ₂ O ₃ is not added. Abrasion resistance can be improved.

Although the present invention has been described above with reference to embodiments, this embodiment can be further modified based on the technical idea of the present invention. For example, the liner sheet 3 having the sheet-like slipping layer described above may be adhesively fixed to the inner wall surfaces of the upper and lower halves 8 and 9. Note that the present invention is of course applicable to so-called cartridge type cassettes.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, in which Fig. 1 is a partially enlarged sectional view of a liner sheet having a slippery layer, and Fig. 2 is a partially cutaway perspective view of a tape cassette equipped with this liner sheet. , Fig. 3A is a graph showing changes in the adhesive force of the liner sheet depending on the binder composition, Fig. 3B is a graph showing changes in the dynamic friction coefficient of the liner sheet depending on the binder composition, and Fig. 3C is a graph showing the change in the liner sheet powder falling depending on the binder composition. The graph showing the changes, FIG. 4, is a schematic side view of an apparatus for measuring the coefficient of dynamic friction. In addition, in the symbols used in the drawings, 1...
...Plastic film, 2... Smooth layer, 3...
Liner sheet, 4... Tape cassette, 7...
It is magnetic tape.

Claims (1)

[Claims] 1. In a tape cassette in which a slippery sheet is provided between a case containing a magnetic tape and the magnetic tape, the slippery sheet is applied to a sheet-like support and a surface of the support. The slippery layer is mainly composed of a mixture of a solid lubricant, an abrasion resistance imparting material, and a binder, and the binder is mainly composed of a cellulose resin and a thermoplastic polyurethane resin. A tape cassette characterized by comprising: