JPS6138545B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a tape cassette in which a sheet-like slipping 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 "slippery plastic sheet") is used between the inner wall of the case (half) and the magnetic tape or hub to reduce the frictional resistance and allow the magnetic tape to run stably. (referred to as a liner sheet) is arranged. Examples of this liner sheet include (1),
Consisting only of polytetrafluoroethylene.
(2) A plastic film filled with or coated with conductive lubricant particles such as graphite or carbon. (3) There is a paper sheet mixed with carbon or the like and top coated with silicone oil. However, although the above (1) has excellent slipperiness, it has a high electric resistance and is disadvantageous in terms of antistatic properties, and the above (2) and (3) have a low filling amount for base materials such as carbon and graphite. Because of the limitations, a considerable amount must be mixed in to produce a sufficient effect, but this has the disadvantage of making molding difficult and increasing costs. The present invention has been made to correct such deficiencies, and in the tape cassette mentioned at the beginning, the sheet-like slipping layer mainly contains a slipping material and a conductive acrylic resin. This relates to a characteristic tape cassette. By configuring in this way, the lubricity and electrical resistance can be improved and it can be easily molded at low cost. 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 above-mentioned conductive acrylic resin is used as a binder, the conductivity of this binder makes it possible to reduce the amount of charge and improve the antistatic property. The amount of conductive lubricant can be reduced by the presence of the resin. Therefore, not only can the lubricity (reduction of frictional resistance) by the lubricant be improved, but also
When a conductive lubricant is used, the amount added can be reduced, making it easier to form the sheet and reducing costs. According to the present invention, as the above-mentioned conductive acrylic resin, poly(2-hydroxy-3
- methachlorooxypropyltrimethylammonium chloride) is preferred. Since this conductive acrylic resin has ionic trimethylammonium chloride at the branch end, it has excellent conductivity and contributes to lowering the amount of charge (electrical resistance) of the sheet-like slipping layer. Furthermore,
When a predetermined amount of a polyisocyanate compound is mixed with this conductive acrylic resin, the -OH in the branches of the conductive acrylic resin reacts and bonds with the isocyanate group of the polyisocyanate compound, resulting in a polyisocyanate compound with high wear resistance. Since an isocyanate-modified acrylic copolymer (crosslinked polymer) can be produced, the abrasion resistance of the sheet-like slipping layer is also greatly improved. Note that this conductive acrylic resin may be poly(2-hydroxy-3-acryloyloxypropyltrimethylammonium chloride) in addition to the above-mentioned methacrylic resin. Further, the above-mentioned conductive acrylic resin may be composed of a copolymer of the above-mentioned -OH-containing conductive acrylic resin and a conductive acrylic resin having the following structural formula (without -OH), but the latter Although the resin has ionicity, it does not react with isocyanate, so its proportion is preferably about 50% or less based on the total copolymer (ie, the extent to which the former resin provides wear resistance). The average molecular weight of the conductive acrylic resin described above is preferably from 20,000 to 200,000, and even more preferably from 40,000 to 100,000. Further, as polyisocyanate compounds that can be used in the present invention, the following di-, tri-, and tetra-isocyanates can be used.

【table】

【table】

【table】

【table】

【table】

【table】

【table】

【table】

[Table] Other isocyanates include PRO
(NCO) ₂ etc. organic phosphorus isocyanate, CF ₃ NCO
or fluorinated isocyanates such as C _o F _2o+1 CH ₂ NCO, sulfonyl isocyanates such as RSO ₂ NCO, and benzyl chloride isocyanates.

[Formula] Isocia of benzalchloride Nate

[Formula] Ethylbenzole isocyanate, styrene isocyanate

[Formula] Urethane triisocyanate etc. When the above-mentioned polyisocyanate compound and the above-mentioned conductive acrylic resin are included, the proportion of the polyisocyanate compound is preferably 5 to 50 parts by weight per 100 parts by weight of the resin such as the conductive acrylic resin. Even better is a proportion of ~30 parts by weight. That is, if the amount of the polyisocyanate compound is less than 1 part by weight, the proportion of the isocyanate-modified acrylic copolymer will decrease, resulting in poor abrasion resistance.
If it exceeds parts by weight, it will be too crosslinked and become too hard, and the relative proportion of the conductive acrylic resin will decrease, resulting in weak ionicity (conductivity) as a whole. The above-mentioned lubricating material used in the present invention is preferably a material having a layered crystal structure and interlayer cleavage from the viewpoint of improving lubricity. molybdenum sulfide,
Examples include graphite fluoride and talc. this house,
Since graphite, carbon black, and molybdenum disulfide have antistatic properties, they are desirable materials for preventing static electricity. The average particle diameter of the 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 is 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. Furthermore, if a fluid-like lubricant is used as the lubricant, the effect of lowering the coefficient of dynamic friction can be further improved. In this case, the fluid lubricant used is the number of carbon atoms
Fatty acid esters consisting of various fatty acids of 25 or less and similar various alcohols, siloxane compounds or polysiloxane compounds having various organic functional groups (e.g. polydimethylsiloxane), various paraffinic compounds such as liquid paraffin and squalane, hydrocarbon compounds, Alternatively, a mixture thereof can be used. The amount of these fluid lubricants is preferably 20 parts by weight or less, more preferably 10 parts by weight or less, based on 100 parts by weight of the conductive acrylic resin. Further, in the present invention, it is desirable to add an abrasion resistance imparting material to improve the abrasion resistance of the sheet. This wear resistance imparting material is preferably a non-magnetic material (abrasive) with a Mohs hardness of 5 or more, including Cr ₂ O ₃ , α-A ₂ O ₃ , SiC, α-Fe ₂ O ₃ ，
SiO ₂ , calcium silicate, kaolin, TiO ₂ ,
Examples include pigments such as ZnO, aluminum silicate, talc, diatomaceous earth, calcium carbonate, aluminum hydroxide, and magnesium carbonate. The average particle diameter of this wear-resistant material is preferably 0.05 to 5.0μ, more preferably 0.1 to 1.0μ. That is, if the average particle size is less than 0.05μ, it is too small and the anti-wear effect will be poor, and if it exceeds 5.0μ, it will easily damage the magnetic tape side and it will be difficult to apply it on the base as described below. . Further, as other additive components, 50 parts by weight or less of resin may be used with respect to 100 parts by weight of the above-mentioned conductive acrylic resin, and this resin may be used as an extender and a strength imparting agent. The resins that can be added include vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, vinyl chloride-vinylidene chloride copolymer, Vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer, acrylic ester-vinylidene chloride copolymer, methacrylic ester-
Vinylidene chloride copolymer, methacrylic acid ester-styrene copolymer, thermoplastic polyurethane resin, phenoxy resin, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, acrylonitrile-butadiene-acrylic acid copolymer Polymer, acrylonitrile-butadiene-methacrylic acid copolymer, polyvinyl butyral, polyvinyl acetal, cellulose derivative, styrene-butadiene copolymer, polyester resin, phenolic resin, epoxy resin, thermosetting polyurethane resin, urea resin,
Examples include melamine resin, alkyd resin, urea formaldehyde resin, etc. The liner sheet according to the present invention, as shown in FIG. 1, for example, includes a base 1 of paper, nonwoven fabric, polytetrafluoroethylene, polyester, polycarbonate, etc., coated with a slipping layer material having the above-mentioned composition,
A slippery layer 2 is formed by drying, and a liner sheet 3 is thereby created. As the solvent in this case, conventionally known solvents including methyl ethyl ketone, cyclohexanone, dimethyl formamide, etc. can be used. This liner sheet is
Specifically, it is installed in a tape cassette 4 shown in FIG. Upper half 8 and lower half 9 of cassette 4
A magnetic tape 7 wound around the reel hubs 5 and 6 is built in between the upper and lower halves 9.
The above-mentioned liner sheet 3 is arranged between the inner wall surface of the magnetic tape 7 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. Note that the surface of the liner sheet 3 may be top coated with a known lubricant.
Moreover, the thickness of the slippery layer 2 is preferably 1 to 20 μm, and even more preferably 2 to 10 μm. That is, if it is less than 1μ, the life will be shortened, and if it exceeds 20μ, it will be difficult to install it in the cassette from a practical standpoint. Next, the present invention will be explained in more detail with reference to examples. Comparative Example A mixture having the following composition was prepared. Conductive acrylic resin 100 parts by weight Methyl ethyl ketone 200 Cyclohexanone 200 This mixture was coated on the base so that the thickness after drying was about 5 μm. Example 1 A mixture having the following composition was prepared. Graphite powder (particle size 5μ) 100 parts by weight Conductive acrylic resin 100 〃 Methyl ethyl ketone 400 〃 Cyclohexanone 400 〃 This mixture was dispersed and mixed in a ball mill to make a paint, which had a thickness of about 5μ after drying. Coat it on the base and let it dry. Example 2 A mixture having the following composition was prepared. Talc powder (particle size 1.2μ) 100 parts by weight Conductive acrylic resin 100 〃 Methyl ethyl ketone 400〃 〃 Cyclohexanone 400〃 This mixture was applied on the base in the same manner as in Example 1 to form a slippery layer about 5μ thick. Example 3 Talc powder (particle size 1.2μ) 100 parts by weight Conductive acrylic resin 100 〃 Polyisocyanate (Desmodyur L: manufactured by Bayer Dye Manufacturing Company) 20 〃 Methyl ethyl ketone 400 〃 Cyclohexanone 400 〃 Talc powder, conductive acrylic resin and Disperse and mix the solvent in a ball mill and apply it on the base for about 30 minutes.
A few minutes before, polyisocyanate was added and mixed, and this was coated and dried on the base so that the thickness after drying was about 5 μm. The coefficient of dynamic friction, abrasion resistance, and electrical resistance of each of the samples described above were measured. When measuring the coefficient of dynamic friction, as shown in Figure 3,
A sample (liner sheet) 3 cut into a 1/4 inch wide tape is brought into contact with the brass drum 10 over 1/4 circumference, and one end is attached to the support 11 in a horizontal state. Lower the other end vertically and attach the weight W. Then, the drum 10 is rotated at a relative speed of 0.75 mm/sec with respect to the sample 3.
The values t ₁ and t ₂ of tension gauges T ₁ and T ₂ placed between the support body 11 and the weight W are read, respectively.
The dynamic friction coefficient μd is given by μd=2/πloget ₂ /t ₁ . In addition, when measuring abrasion resistance (powder falling amount), cut the pieces into 1/4 inch width and hang them on a roller wrapped with #800 wrapping tape specified in JIS R6001 and JIS R6253, and apply a load of 100 g. 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. The results are shown in the table below.

[Table] *As a conventional example, a liner sheet made of polytetrafluoroethylene sheet containing carbon was used.
From these results, it can be seen that the liner sheet according to this example is comparable to or better than the conventional one in terms of friction coefficient and abrasion resistance, and is significantly superior in terms of electrical resistance. 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. In some cases, the base 1 of the liner sheet 3 may be omitted,
The slippery layer 2 can be formed by directly coating 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 can be constructed from only the slipping layer, and this slipping sheet can be combined with the halves 8 and 9 and the magnetic tape 7 as shown in FIG. can be placed between. Note that the present invention is of course applicable to so-called cartridge type cassettes.

[Brief explanation of the drawing]

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. 3 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...
Base, 2... Smooth layer, 3... Liner sheet, 4...
Tape cassette, 7...magnetic tape.

Claims (1)

[Claims] 1. In a tape cassette in which a sheet-like slipping layer is arranged between a case containing a magnetic tape and the magnetic tape, the sheet-like slipping layer mainly contains a slipping material and a conductive acrylic resin. A tape cassette characterized by: