JPS6156587B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a tape cassette in which a slippery layer is disposed 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
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. Further, 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 to correct the above-mentioned defects, and in the tape cassette mentioned at the beginning, the slipping layer is mainly composed of a mixture of a lubricant and a binder, and the binder is made of fibers. The present invention relates to a tape cassette characterized in that its main components are a base resin, a thermoplastic polyurethane resin, and a polyisocyanate compound. With this configuration, the abrasion resistance and lubricity of the sheet-like slipping layer are improved, and sufficient adhesive strength can be obtained even when coated on 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, since the main components of the binder are a cellulose resin, a thermoplastic polyurethane resin, and a polyisocyanate compound (crosslinking agent), a structure in which both of these resins are crosslinked is formed, and a lubricant is included in this structure. As a result, the wear resistance of the slipping layer is extremely good, and an increase in the coefficient of friction is suppressed and kept low. Moreover, since the binder contains cellulose resin and thermoplastic polyurethane resin,
The combination of these resins provides very good adhesive strength and makes the slipping layer itself stable. The lubricant used in the present invention has the following properties in terms of improving lubricity:
A material having a layered crystal structure and interlayer cleavability is desirable, and examples thereof include graphite, carbon black, molybdenum disulfide, graphite fluoride, and talc. Among these, graphite, carbon black, and molybdenum disulfide have antistatic properties and are desirable materials in terms of antistatic properties. Furthermore, the average particle size of the lubricant used in the present invention is preferably 0.5 to 10μ,
More preferably, the thickness is 1 to 5μ. 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 100μ)
(μ or more), it becomes too large and it becomes difficult to apply it onto the base, which will be described later. According to the present invention, it is desirable to mix the above-mentioned lubricant with a binder and apply this mixture on a base to form a lubricating layer. It has been found that it is extremely important to use a binder whose main components are a cellulose resin, a thermoplastic polyurethane resin, and a polyisocyanate compound in order to improve the adhesive strength to the adhesive. The cellulose resin that can be used is a cellulose resin as a polymer produced by dehydration condensation of glucose, and the three hydroxyl groups (-OH) in the glucose anhydride unit are subjected to esterification, etherification, nitration reaction, etc. It is preferable to use one that has been appropriately modified. In this case, it is desirable that an average of 1.5 to 2.8, preferably 1.9 to 2.5 of the three hydroxyl groups be 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 includes cellulose nitrate, cellulose acetate, cellulose propionate, cellulose acetate butyrate,
These cellulose may be methyl fiber acid type, ethyl cellulose type, etc., and these cellulose can be converted into nitroxy group (-ONO ₂ ), acetoxy group (-
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 terminal, p,
Examples include those crosslinked with a diisocyanate compound such as 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 has a glass transition temperature of 0.
℃ or less is preferable. For example, Nituporan
2304, 2320, 3022, 5033 (all trade names of Nippon Polyurethane Co., Ltd.), Estane
5701F-1, 5702, 5703, 5707F-1, same
Examples include 5710F-1 and 5715 (the above are trade names manufactured by BF Gutdrich Co., Ltd.). Further, as the polyisocyanate compound used as a crosslinking agent in the present invention, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, p-phenylene diisocyanate,
Polymethylene polyphenyl isocyanate, diphenylmethane diisocyanate, m-phenylene diisocyanate, hexamethylene diisocyanate, butylene-1,4-diisocyanate, octamethylene diisocyanate, 3,3'-dimethoxy 4,4'-biphenylene diisocyanate, 1 , 18-octadecamethylene diisocyanate, polymethylene diisocyanate, benzene triisocyanate, naphthalene-2,4-
Diisocyanate, 3,3'-dimethyl-4,4'-
Biphenylene diisocyanate, 1-methoxyphenylene-2,4-diisocyanate, diphenylene-4,4'-diisocyanate, 4,4'-diisocyanate-diphenyl ether, naphthalene-1,5-diisocyanate, diisocyanate-dicyclohexyl-methane , p-xylene diisocyanate, m-xylene diisocyanate, hydrogenated diphenylene diisocyanate, hydrogenated diphenylmethane diisocyanate, toluene-2,4,6-triisocyanate, 3-methyl-4,6,4'-triisocyanate diphenyl Methane, 2,4,4'-triisocyanate-diphenyl, 2,4,4'-triisocyanate-diphenyl ether, long-chain hydrocarbons or substituted hydrocarbons having an unterminated group -NCO, and these compounds,
Alternatively, a reactive polyisocyanate or a prepolymer having a plurality of -NCOs may be used. Next, the ratio of each component of the slipping layer according to the present invention will be described. First, the amount of lubricant is based on 100 parts by weight of binder.
The amount is preferably 60 to 600 parts by weight. That is, if the lubricating material is less than 60 parts by weight, it is too small and will not be effective in reducing frictional 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 composition of the binder is 20 to 95% by weight of cellulose resin, 80 to 5% by weight of thermoplastic polyurethane resin, and 0.2 to 50 PHR (parts by weight per 100 parts by weight of resin) of polyisocyanate compound. desirable. That is, if the content of the cellulose resin is less than 20% by weight, the coefficient of friction will increase, and if it exceeds 95% by weight, the adhesive strength will decrease and the coating film (slip layer) will become brittle. Moreover, if the thermoplastic polyurethane resin exceeds 80% by weight, friction will increase, and if it is less than 5% by weight, the adhesive strength will decrease and the coating film will become brittle. Furthermore, if the amount of the polyisocyanate compound added is less than 0.2 PHR, both wear resistance and friction properties will deteriorate, and if it exceeds 50 PHR, no significant improvement in properties can be expected, and too much crosslinking will occur, making the coating film brittle. Note that the slipping layer may also contain 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. is desirable, and preferably 2 to 10μ. 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 composition having the following composition was prepared.

[Table] After thoroughly mixing these in a ball mill, a polyisocyanate compound (for example, Dismodyur L: a product name manufactured by Bayer AG) was added in three ways: 0.2 parts by weight, 10 parts by weight, and 40 parts by weight. The mixture was stirred and mixed for a minute to form a coating for a slippery layer. This paint was applied onto the base so that the thickness after drying was, for example, 5 μm to form a liner sheet. As a specific example, as shown in FIG. 1, the above paint is applied onto a polyethylene terephthalate film 1 and dried to form a slippery layer 2.
In this way, a liner sheet 3 is created. This liner sheet is actually installed in a tape cassette 4 shown in FIG. Between the upper half 8 and lower half 9 of the cassette 4, there are reel hubs 5 and 6.
A magnetic tape 7 wound around each of the upper and lower halves is built in, and the above-mentioned liner sheet 3 is disposed between the inner wall surfaces of the upper and lower halves and the magnetic tape 7, 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, thermoplastic polyurethane resin, and polyisocyanate compound was varied, the third
The results shown in the figure were obtained. To explain the measurement method used to obtain this data, first, when measuring the coefficient of (dynamic) friction, 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/π1oget ₂ /t ₁ . In addition, when measuring abrasion resistance (powder falling),
Insert the liner sheet into the cassette as shown in the picture,
After running the tape 500 times, the amount of powder falling from the liner sheet in contact with the reel hub was measured. The amount of powder falling off was expressed using a point system. From the results shown in Figure 3, in order to maintain high wear resistance and suppress the increase in the coefficient of friction, the binder composition should include 20 to 95% by weight of nitrocellulose and 5 to 80% by weight of thermoplastic polyurethane resin.
It can be confirmed that it is desirable to select the following. It is also seen that both wear resistance and lubricity are improved by adding Dismodule L as a crosslinking agent, and when the amount added is 0.2 PHR or more, the properties are significantly improved. However, over 40PHR
Above 50 PHR, we cannot expect much reduction in the coefficient of friction, and from the viewpoint of preventing embrittlement of the coating film, the upper limit of the amount of Dismodule L added is
It is desirable to set it to 50PHR, and it is more desirable to set it to 40PHR. Next, another example will be described with reference to FIGS. 5 to 8.
In this example, as shown in FIG. 5, when coating and forming a slippery layer on the tape side surface of the base film 1,
A coating material containing the above-mentioned lubricant and binder as main components is applied in diagonal lines, thereby coating the slipping layer 12 in the form of diagonal stripes with a width of 400 to 450μ intermittently at intervals of 50 to 100μ (i.e., 1 to 1 mm within 1 mm). 5 slippery layers) are formed. Alternatively, as shown in Fig. 6, paint is applied in dots using a gravure coater, and the spacing between circular unapplied areas (dots) is approximately 1 mm (i.e., ^1/2 to 5 dots within 1 mm2). The slippery layer 22 may have a shape pattern. In short, instead of coating the slippery layer 2 all over the basic film as described in the first example (Fig. 1),
It is applied intermittently or partially, such as by dot coating, to partially form a slippery layer. That is, in solid coating as shown in Fig. 1, the slippery layer 2
has good abrasion resistance and adhesive strength, but since it contains a considerable amount of binder (adhesive), the coefficient of friction is higher than that of a lubricant layer consisting of only a lubricant. Becomes a target. However, in this example, the lubricating layers 12 and 22 containing the binder are formed by partially patterning them, so they not only have good abrasion resistance and adhesive strength, but also have less friction than solid coating. In particular, it is possible to provide a liner sheet suitable for high-grade cassettes that requires low friction. The characteristics of the liner sheet according to this example are shown in FIGS. 7 and 8. FIG. 7 shows the friction against metal (for example, brass) and the adhesion of the slipping layer to the base film, and FIG. Indicates interlayer friction against the base. Friction can be measured in the same way as described above, but when measuring adhesion force, 1/
A 1/4 inch wide flexible film is adhered to the coated surface (smooth layer) of a sample (liner sheet) cut into a 4 inch wide tape, and then this flexible film is pulled in a direction of 180°C. Measure the force required to break the adhesion at the interface between the base film and the paint film. This adhesive strength was expressed using a point system. As is clear from this result, compared to the case where the slippery layer is painted solidly, the liner sheet with diagonal lines as in this example has almost no change in the adhesive strength of the slippery layer and has a smaller coefficient of friction. Improves smoothness. In particular, the decrease in interlayer friction is remarkable (diagonal line coating is better than dot coating);
In a slippery liner sheet, contact between the sheet and the tape is extremely important in improving the running properties of the tape. Next, still another example will be described with reference to FIGS. 9 and 10. In the liner sheet 3 according to this example, as shown in FIG.
is formed, and the above-mentioned slipping layer 2 is coated on this undercoat layer. As a result, not only the adhesiveness of the slipping layer 2 becomes good, but also its coefficient of friction can be reduced. That is, in the liner sheet shown in FIG. 1, the slippery layer 2 coated directly onto the film 1 contains a large amount of binder (adhesive) in order to improve adhesion to the film 1. There is. However, when a large amount of binder is added (assuming the amount of lubricant is constant), the adhesiveness of the slipping layer 2 improves, but on the other hand, the friction increases. Furthermore, if the amount of binder is reduced in order to lower the coefficient of friction, the adhesion properties will deteriorate, so it is difficult to achieve both frictional properties and adhesion properties. However, as in this example, if the film 1 is first provided with an undercoat layer 30 having a strong adhesive force (and therefore has a high binder content), and then a lubricant-containing slipping layer 2 with a controlled amount of binder is formed on the surface of the undercoat layer 30. Since the amount of binder in the slipping layer 2 can be made appropriate, the coefficient of friction can be lowered, and the adhesiveness can also be improved so that the slipping layer 2 can be firmly held through the undercoat layer 30. can be done. Specifically, as the undercoat liquid used to form the undercoat layer 30, a mixture of the following resins and solvents is used. Resins that can be used include thermoplastic polyurethane resins (e.g. Estan 5702 manufactured by B.F.
or 300), a copolymer of vinylidene chloride and vinyl propionate (for example, Reunron manufactured by Tekkosha Co., Ltd.),
QJ-1 or QJ-2), polyamide resins (e.g. Tomide #390 or #395 manufactured by Fuji Chemical Co., Ltd.), vinyldene chloride resins (e.g. Aron 321 manufactured by Toagosei Co., Ltd.), bisphenol-based epoxy resins (e.g. Dainippon Ink Co., Ltd.) Epicron 850) manufactured by the company. When a silane coupling agent is added to these resins, the effect as an undercoat layer can be further improved. As an example, 5% by weight Estan 5702 and 95% by weight
An undercoating liquid (preferably containing a polyisocyanate compound) consisting of methyl ethyl ketone and methyl ethyl ketone is applied onto the film 1 and dried. Next, a coating material for a slipping layer having the following composition is applied onto the undercoat layer 30 having a thickness of 0.5 μm thus formed.

[Table] Figure 10 shows the data obtained for the liner sheet thus obtained. According to the results, it can be seen that although the friction of the liner sheet according to this example is equivalent to that without the undercoat layer, the adhesion of the slipping layer is significantly improved compared to the case without the undercoat layer. . Note that as the amount of graphite powder increases, the friction coefficient decreases, but the adhesive force tends to decrease. In this example, as the amount of graphite powder added increases, the adhesiveness decreases, but even if the adhesiveness decreases, it can still be maintained at a large value. 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, by combining the examples shown in FIGS. 5 and 6 with the example shown in FIG. 9, it is possible to form an undercoat layer as shown in FIG. 9 even in the case of diagonal line coating or dot coating. Further, 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. In some cases, the base film 1 of the liner sheet 3 may be omitted and the slipping layer 2 may be directly coated on the inner wall surfaces of the halves 8 and 9. In this case, if the mechanical strength of the slipping layer is sufficiently large, a liner sheet is constructed of only the slipping layer, and this slipping sheet is placed between the halves 8 and 9 and the magnetic tape 7 as in FIG. can be placed. Note that the present invention is of course applicable to so-called cartridge type cassettes. In addition, the lubricious sheet of the present invention maintains the same low friction as conventional products (carbon-containing Teflon sheets, etc.) and can be produced at a low cost, so it is especially used for tape sagging and tape positioning in video cassettes. It is suitable for

[Brief explanation of the drawing]

The drawings show embodiments of the present invention, in which Fig. 1 is a partially enlarged sectional view of an example of a liner sheet having a slippery layer, and Fig. 2 is a partially cutaway view of a tape cassette equipped with this liner sheet. Perspective view, 3rd
The figure is a graph showing changes in abrasion resistance and (dynamic) friction coefficient of liner sheets depending on binder composition.
The figure is a schematic side view of an apparatus for measuring the coefficient of dynamic friction, FIG. 5 is a plan view of the slippery layer side of a liner sheet according to another example, and FIG. 6 is a plan view of the slippery layer side of a liner sheet according to a modification thereof. , Figure 7 shows the adhesive strength and (dynamic) of the slipping layer of the liner sheet depending on the binder composition.
A graph showing a comparison of changes in friction coefficients, FIG. 8 is a graph showing a comparison of (dynamic) friction coefficients of the same liner sheets, FIG. 9 is a partial enlarged sectional view of a liner sheet according to another example, and FIG. The figure is a graph showing a comparison of the adhesive force and (dynamic) friction coefficient of the slipping layer of the same liner sheet. In addition, in the symbols used in the drawings, 1...
... plastic film, 2, 12, 22 ... slipping layer, 3 ... liner sheet, 4 ... tape cassette, 7 ... magnetic tape, 30 ... undercoat layer.

Claims (1)

[Claims] 1. A tape cassette in which a slippery layer is disposed between a case containing a magnetic tape and the magnetic tape, wherein the slippery layer is mainly composed of a mixture of a lubricant and a binder, and the binder is made of fibers. A tape cassette characterized in that its main components are a base resin, a thermoplastic polyurethane resin, and a polyisocyanate compound.