JPH0574151B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a transparent slip sheet for cassettes, and more specifically, it is a transparent slip sheet that is incorporated into tape cassettes such as audio cassettes and video cassettes, and is used to prevent the tape from loosening and to smooth the running of the tape. Regarding slip sheets. Prior Art A magnetic tape cassette is provided with a slip sheet between the tape and the cassette case in order to make the magnetic tape run smoothly. This slip sheet has the effect of allowing the magnetic tape to run smoothly and preventing irregular winding by rotating the wound tape with its side surface in contact with the sheet. Conventionally, poly(4-fluoroethylene) sheets have been used as slip sheets due to their low coefficient of friction and high thermal stability, but these sheets are expensive and have poor flexibility due to their high flexibility. However, there is a drawback that the periphery of the sheet is bent. In addition, graphite on plastic film,
There are sheets filled with or coated with conductive lubricant particles such as carbon, or sheets in which carbon black, phosphorous graphite, molybdenum disulfide, etc. are mixed into paper, and the surface is coated with silicone resin or fluororesin. However, these slip sheets are black and opaque, and are hidden by display paper pasted on the outside of the case, and have the disadvantage that the winding state of the magnetic tape inside the cassette cannot be seen. In order to improve this drawback, a method has been proposed in which silicone oil is applied to the surface of a transparent plastic sheet (Japanese Patent Laid-Open No. 146066/1983).
However, simply applying a lubricant such as silicone oil to the surface of the plastic sheet will not adhere well to the transparent plastic film, and when actually used, friction will increase over time and durability will be insufficient. There is a problem that occurs. Furthermore, a method has been proposed in which a laminate is formed by coating the surface of a transparent plastic sheet with a paint made by adding a lubricant to a thermoplastic resin such as a vinyl chloride-vinyl acetate copolymer or a polyurethane resin (Unexamined Japanese Patent Publication No. Publication No. 58-60474). However, these laminated coatings lack surface hardness, and as the magnetic tape runs, scratches occur at the edges.
The problem is that transparency is decreasing. As can be understood from the above, the properties required for slip sheets incorporated into magnetic tape cassettes include good surface lubricity, as well as excellent durability, scratch resistance, and antistatic performance. Furthermore, when printing is applied to the back surface, it is important to ensure that the lubricant used on the surface does not transfer to the back surface and inhibit printing. On the other hand, for the purpose of stabilizing the surfaces of plastics and glasses, silicon oxide films have traditionally been provided on the surfaces of these materials. A method of treating the surface of a substrate with an isocyanate compound has been proposed (Japanese Unexamined Patent Publication No. 59-39714). However, according to the research conducted by the present inventors, even this method cannot satisfy the above-mentioned required characteristics of the slip sheet. OBJECTS OF THE INVENTION An object of the present invention is to provide a transparent slip sheet for cassettes that satisfies the above-mentioned required performance. Structure and Effects of the Invention According to the present invention, a silicon oxide film derived from a silane isocyanate compound having a ≡Si-NCO bond in the molecule is provided on at least one side of a transparent plastic film, and This is achieved by using a transparent slit sheet for cassettes, which has a silicon-based lubricant chemically bonded to a silicon film and exposed on the surface of the film. In the present invention, transparent plastic films such as polystyrene, polymethyl acrylate, polycarbonate, polysulfone, polyester, etc. can be used as the transparent plastic film. Among these films, biaxially oriented polyester films, particularly polyethylene terephthalate films, are preferred. The transparency of the polyester film can be adjusted by adjusting the amount of lubricants such as clay, kaolin, silica, calcium carbonate, phosphorus-containing compounds, etc. added or precipitated during the polymer production step. Furthermore, polyester film has the advantage of being excellent in solvent resistance required when coating the film during or after film formation, heat resistance during use, mechanical properties, etc. The thickness of transparent plastic film is 25~100μ
It is preferable that the transparency is haze.
It is preferably 10% or less. In the present invention, the silicon oxide film provided on at least one side of the transparent plastic film is formed by the reaction of a silane isocyanate compound having a ≡Si-NCO bond in its molecule with moisture. This moisture may be moisture attached to the surface of the transparent plastic film, moisture in the air, or the like. This silicon oxide (film) formation reaction (hydrolysis reaction of the silane isocyanate compound) is thought to proceed as shown in the following equation.

[Chemical] Through the above reaction, ≡
A silicon oxide film having bonds such as SiOH and ≡Si-O- is formed. This reaction (hydrolysis reaction) proceeds satisfactorily at temperatures ranging from room temperature to 100° C. or less, and has the advantage that reaction by-products are gaseous, there is no reaction residue, and no catalyst is particularly required. Examples of silane isocyanate compounds include the following formulas: [Si(NCO) ₄ ], [RnSi(NCO) ₄ n], [(RO)nSi(NCO) ₄ n] (However, R in the above formula is a methyl group, ethyl group,
a hydrocarbon group such as a phenyl group, a vinyl group, etc., where n is 1, 2 or 3), or a condensate of these compounds,
Examples include mixtures. In particular, in order to improve the adhesion to the polyester film, the greater the number of isocyanate groups (-NCO) in the molecule, the better; for example, methylsilyl triisocyanate, ethoxysilane triisocyanate, tetraisocyanate silane, etc. are preferred. These silane isocyanate compounds are dissolved in an organic solvent such as ethyl acetate, n-hexane, toluene, methyl ethyl ketone, etc., and prepared as a paint. The coating liquid of the above silane isocyanate compound includes:
For example, γ-aminopropyltrimethoxysilane,
It is also possible to add a silane coupling agent such as N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, γ-mercaptopropyletrimethoxysilane, etc. to improve the leveling effect and adhesion of the coating film. . In the present invention, a silicon-based lubricant is chemically bonded to a silicon oxide film, and at least a portion of the silicon-based lubricant is exposed on the surface of the silicon oxide film. The functional groups involved in this chemical bond are hydroxyl group (-OH) and carboxyl group (-COOH).
etc. are preferred. Examples of silicon-based lubricants having this functional group include Dow Corning Co., Ltd.'s product name "DKQ8-778, -779" and Shin-Etsu Chemical Co., Ltd.'s product name KR.
−213, −214, −216” etc., Toagosei Co., Ltd. product name “GS”
The amount of silicone lubricant used is preferably 1.0 to 10.0% by weight based on the silane isocyanate compound. The surface friction coefficient can be greatly reduced and good lubricity can be imparted.The silicon-based lubricant used in the present invention has a functional group that reacts with a silane isocyanate compound, and as a characteristic unique to silicon, forms a silicon oxide film. It appears on the surface of the film during the process.It is assumed that the above reaction substantially proceeds at the paint stage.This gives the surface of the formed paint film (silicon oxide film) lubricity and release properties. In addition, when the slip sheet is rolled into a roll, it is possible to obtain a slip sheet that does not transfer silicone lubricant to the back surface (rear surface). When the tape is installed in a slip sheet and run, static electricity is generated due to the sliding contact between the end of the tape and the slip sheet.
Since this may impede the smooth running of the tape, it is preferable that the slip sheet has antistatic properties. As a means for imparting antistatic ability to a transparent slip sheet, a method of incorporating an antistatic agent into a coating liquid of a silane isocyanate compound is preferred because it is simple and effective. As this antistatic agent, a quaternary ammonium salt type antistatic agent is particularly preferable, and specifically, alkyltrimethylammonium chloride, alkyldimethylammonium ethosulfate, etc. are particularly preferably used. The amount of antistatic agent is preferably 0.5 to 5.0% by weight based on the silane isocyanate compound. This amount can greatly reduce the surface resistivity of the slip sheet. In the present invention, a silane isocyanate compound,
A paint using a silicone lubricant, more preferably an antistatic agent, is preferably prepared with a solid content concentration of 1 to 30% by weight, more preferably 1 to 10% by weight.
There are no particular restrictions on the coating method of paint, such as bar coating method, doctor plate method,
A reverse coating method, a gravure coating method, etc. can be used. At that time, the amount of application should be 5.0 to 15.0 in terms of wet amount.
g/m ² and a thickness of 0.1 to 1 μm after drying. Drying after application of the coating material, coating film formation reaction, etc. may be carried out at room temperature, or may be heated within a temperature range that allows the slip sheet to maintain a stable shape. From the viewpoint of processing time, heating is preferable. If the plastic film is biaxially oriented polyethylene terephthalate film, the heat treatment should be 120℃ or less,
Furthermore, it is preferable to carry out the reaction at a temperature of 100°C or lower. Since the slip sheet of the present invention maintains transparency and has excellent slip properties and preferably excellent antistatic properties, it can be incorporated into tape cassettes such as audio cassettes and video cassettes, and the slip sheet can be used to slide the tape into contact with the slip sheet and loosen the slip sheet. It is possible to prevent this and to make running smoother. EXAMPLES The present invention will be described in more detail with reference to Examples below. The various properties of the film for slip sheets were measured by the following methods. (1) Total light transmittance, haze Based on JIS K6782, haze is a percentage comparison of total light transmittance (%) and scattered light transmittance (%) measured with a haze meter (manufactured by Nippon Denshoku). Indicated. (2) Coefficient of Dynamic Friction Based on ASTM D1894, the coefficient of kinetic friction between the smooth surfaces of the plastic film and between the smooth surface and the back surface is shown. (3) Surface specific resistance The surface specific resistance was measured using a super insulation resistance meter (RM-21A, manufactured by Yokogawa Electric) in accordance with ASTM D-257. (4) Durability The attached diagram is a schematic diagram of the device that evaluates the running and durability of the film (NJS101 manufactured by Japan Automatic Control Co., Ltd.).
type). In the figure, 1 is a feeding reel, 2 is a tension control, 3, 5, 6, 8, 9, 11 are free rolls, 4, 10 are tension detectors, 7 is a fixed pin, 12 is a guide roll, 13 is a winding It is a take reel. With the easy-sliding surface in contact with the fixing pin 7 at (152/180)π radians, the film is moved at a speed of 3.3 cm per second.
run at a speed of The film length is 3.3m,
When the film on the feed reel is finished, return it to its original position and run it again. This round trip is counted as one time. The vehicle was repeatedly driven 100 times, and its durability was evaluated using the following test. () Coefficient of dynamic friction: Control the inlet tension to 30gr and use the following formula μk = 0.868log (T ₂ /30) from the outlet tension T ₂ to find μk during the first and 100th reciprocation, and examine this change. Ta. () Scrapability: After 100 reciprocating runs, the film was visually observed and the occurrence of scratches caused by the fixing pins was examined according to the following criteria. 〇 No scratches × Scratches generated Examples 1 and 2 and Comparative Examples 1 and 2 Tetrisocyanate silane (Matsumoto Pharmaceutical Co., Ltd.)
10% by weight of ethyl acetate solvent (Paint I) (product name: "Orgachix SI-400") was applied to a transparent polyester film (Teijin Ltd. product name: "Tetron Film GS").
-50μ'') was coated with a bar coat so that the coating thickness after drying was 0.5μm, and dried at 100°C for 20 seconds to obtain a surface-treated film (Comparative Example 2).
Also, only this polyester film was used.
(Comparative Example 1). On the other hand, in order to impart slipperiness, silicone oil having hydroxyl groups (Dow Corning, trade name "DK Q8-779") was added at a rate of 0.5% per 100 parts by weight of the above coating solution.
Added parts by weight. This coating liquid (paint) was coated on one side of the same polyester film as above using a bar coat so that the thickness after drying was 0.5 μm, and dried at 100° C. for 20 seconds (Example 1). Further, in order to impart an antistatic effect, 0.5 part of a quaternary ammonium salt (trade name "Cationogen ES-O", manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was added to the paint to obtain a paint. This paint was coated on one side of the same polyester film as above using a bar coat so that the thickness after drying was 0.5 μm, and dried at 100° C. for 20 seconds to obtain a film (Example 2). Table 1 shows the results of performance tests on these films. From Table 1, it can be seen that the sheet of Example 2 is useful as a slip sheet having excellent slipperiness, durability, and antistatic properties. Further, it can be seen that the material of Example 1 has excellent slipperiness and durability.

【table】

【table】 [Brief explanation of the drawing]

The figure is a schematic diagram of an apparatus for measuring the coefficient of dynamic friction (μk) for evaluating film running properties. 1: Feeding reel, 2: Tension control, 3, 5, 6, 8, 9, 11: Free roll,
4: Tension detector (inlet), 7: Fixed pin,
10: Tension detector (outlet), 12: Guide roller, 13: Take-up reel.

Claims (1)

[Claims] 1. A silicon oxide film derived from a silane isocyanate compound having a ≡Si-NCO bond in the molecule is provided on at least one side of a transparent plastic film,
A transparent slip sheet for a cassette, comprising a silicon-based lubricant chemically bonded to the silicon oxide film and exposed on the surface of the film. 2. The slip sheet according to claim 1, wherein the functional group involved in the bonding of the silicone lubricant is -OH or -COOH. 3. The slip sheet according to claim 1, wherein the silicon oxide film contains a quaternary ammonium salt type antistatic agent.