JPH0519900Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Industrial Application Field] The present invention relates to a low-friction sheet for tape rolls. The tape roll as used in the present invention refers to a flexible long strip (hereinafter referred to as "tape") such as magnetic tape such as video tape or audio tape, or 8 mm movie film such as Single 8 or Super 8. [Prior Art] The tape roll is usually rewound or wound up inside a case called a cassette or magazine (cartridge). There is a concern that the tape may rub against the inner surface of the case and hinder the running of the tape.For this reason, a low-friction member, generally called a low-friction sheet, is fixed or rotatably provided between the inner surface of the case and the tape roll. This low-friction sheet has a low coefficient of friction,
It is required to have wear resistance, dimensional stability, and antistatic properties. Conventionally, such low-friction sheets include fluororesin sheets, silicone or wax-treated paper, and JP-A-Sho.
A sheet containing a fluorine compound on the surface of a thermoplastic film as proposed in No. 50-145482, or as disclosed in Japanese Utility Model Publication No. 43-2858,
Sheets coated with at least one of wax, low molecular weight polyethylene, and sodium salt of alkyl sulfate are known. [Problems to be solved by the invention] These low-friction sheets are not necessarily satisfactory in terms of antistatic properties, abrasion resistance, and planar stability; Attempts have been made to reduce the amount of charge by adding various antistatic agents to the film. However, the antistatic effect was small and the cost was high. In particular, transparent thermoplastic resin films that do not contain additives may have a low coefficient of friction as a film, but they may be attracted to the tape roll due to static electricity generated by friction with the tape roll, increasing the coefficient of friction. If dust adheres to the tape roll and it is used as a low-friction sheet for video tape or audio tape, it will cause drop-outs (sound skipping or blurred images), and if it is used as a low-friction sheet for 8mm movie film, it will generate sparks. This method has not been put to practical use because it not only exposes the photosensitive material to light and causes photofogging problems, but also allows film cutting debris, photographic emulsion powder, and other dust to adhere, significantly impairing the image quality of the film. To overcome these shortcomings, most of the low-friction sheets for tape rolls that are currently in practical use are Teflon sheets with carbon black added, ultra-high molecular weight polyethylene sheets made by cutting and forming with carbon black added, or carbon black sheets. A sheet containing a paper support coated with a lubricant is used. However, since these low-friction sheets contain a large amount of carbon black, carbon black lumps tend to form on the surface that comes into contact with the tape roll, reducing the surface strength of the sheet and causing dirt on the machine during sheet forming. had become very expensive. Appropriate curling is required to hold the tape roll, but carbon black has a problem in that its curling and size change greatly due to changes in humidity due to its water absorption properties. In particular, ultra-high molecular weight polyethylene sheets containing carbon black, which are used by many manufacturers by cutting and forming, tend to curl more toward the center of the cylinder, and the variation in curls is extremely large, making it impossible to create a uniform low-friction sheet. There's a big problem. An object of the present invention is to eliminate the above-mentioned drawbacks of conventional low-friction sheets, to provide a new low-friction sheet that has each of the above-mentioned properties and can be manufactured at low cost. [Means for Solving the Problems] The above object of the present invention is to provide a molecularly oriented high-density polyethylene resin film with a thickness of 30 to 150μ having a surface in contact with the tape roll and a surface with a low coefficient of friction in contact with the tape roll. The opposite side (back side) is treated so that the surface tension is 42 dyne/cm or less, and then an 80 to 600 Å thick aluminum vapor deposition layer is provided.The peeling voltage on both front and back surfaces is 21 volts or less, and the static friction on the surface This is achieved by using a low-friction sheet with a coefficient of 0.250 or less and a back surface static friction coefficient of 0.325 or more. The present invention will be described in detail below with reference to the drawings. FIG. 1 is a cross-sectional view of a low-friction sheet according to the present invention, which is a low-friction molecule-oriented high-density polyethylene resin film. Reference numeral 2 denotes an aluminum vapor-deposited layer, which is provided on the opposite surface (back surface) of the low-friction molecule-oriented high-density polyethylene resin film 1 that contacts the tape roll. This aluminum vapor-deposited layer has a thickness of 80 mm in order to satisfy the adhesion strength with the low-friction molecular-oriented high-density polyethylene resin film, antistatic properties, curling, and flatness.
Within the range of Å~600Å, preferably 100Å~
It is within the range of 400 Å. If it is less than 80 Å, it will not satisfy the anti-static properties due to peeling, and if it is more than 601 Å, it will melt and soften due to the heat during aluminum evaporation unless a low-friction molecular-oriented high-density polyethylene resin film 1 with extremely high density and molecular orientation is used. , shrink,
It deforms and creates unevenness, damaging the flatness,
Not only may the curl become large, but also the cost of aluminum vapor deposition becomes high, making it impractical. By providing an aluminum vapor deposition layer with a thickness of 80 to 600 Å, it is possible to reduce the peeling voltage on both the front and back surfaces to 21 volts or less. There is no longer any problem with other dust adhering to the tape roll, film cutting scraps or photographic emulsion powder that impairs the image quality of 8mm movie film, or optical fog caused by static electricity. In the present invention, in order to further increase the adhesive strength between the low-friction molecular-oriented high-density polyethylene resin film 1 and the aluminum vapor-deposited layer 2 and to prevent the aluminum-deposited layer from peeling off, a low-friction molecular-oriented high-density polyethylene resin film is used. It is preferable that the surface on which the aluminum vapor-deposited layer 2 is formed is subjected to a film surface modification treatment such as corona discharge treatment, flame treatment, ultraviolet irradiation treatment, and anchoring agent coating. The degree of this surface modification treatment was determined using the JIS K6768 wetting test method.
If it is not less than 42dyne/cm, it will have a negative effect on the low friction properties of the surface. Also, if necessary, to protect the aluminum vapor deposited layer 2.
Even if a protective layer 3 such as a lacquer layer, wax layer, or resin layer with a thickness of 20 μm or less is provided, the antistatic property will not be significantly impaired. In the present invention, the aluminum vapor-deposited layer 2 is provided on the surface (back surface) opposite to the surface of the low-friction thermoplastic resin film 1 that comes into contact with the tape roll, and this is mainly for the following reasons. In other words, providing the aluminum evaporated layer 2 on the surface (back surface) of the film in contact with the tape roll can be done in the same way as providing it on the opposite surface (back surface), and although it has the advantage of having a large antistatic effect, it has poor abrasion resistance. Various problems occur, such as poor performance, adhesion (adhesion) strength, tape contamination, flatness, high coefficient of friction, etc., and the disadvantages far outweigh the advantages of the antistatic properties mentioned above. This is because there is a risk that it will be difficult to Regarding the friction of the low-friction sheet in this invention, the surface (surface) in contact with the tape roll
is low friction and easy to slip, and the opposite side (back side) is a high friction and non-slip sheet to make it difficult for the low friction sheet to move. Specifically, the surface preferably has a static friction coefficient of 0.250 or less in order to improve the running properties of the tape, keep the peeling voltage to 30 volts or less, and improve wear resistance. On the other hand, the back surface preferably has a static friction coefficient of 0.325 or more in order to prevent movement and generation of abrasion powder. That is, the low friction sheet of the present invention is characterized in that the front and back sides have contradictory values in terms of static friction coefficient. A protective layer 3 may be provided if necessary to prevent peeling and wear of the aluminum vapor deposited layer.
(Figure 4) In the present invention, in order to provide the protective layer 3 and the anchor coating layer (=adhesion improving layer), generally known melt extrusion coating method, spray coating method, roller coating method, air knife coating method, etc. Gravure coating method, curtain coating method, silk screen coating method, reverse roll coating method, bar coating method,
Various methods can be employed, such as a smoothing coat method and a doctor coat method. However, the total thickness of the low-friction sheet is preferably in the range of 30 to 170 μm, more preferably 50 μm to 170 μm, from the viewpoint of suitability for incorporation into a magazine or cassette, low friction, antistatic properties, cost, rigidity, etc.
It is within the range of 110μm. Therefore, the thickness of the low friction molecular oriented high density polyethylene resin film 1 is 30
It is preferable to set it to 150 micrometers, and it is more preferable if it is 50 to 100 micrometers. The static friction coefficient of the surface of the low-friction molecule-oriented high-density polyethylene resin film 1 in contact with the tape roll is preferably 0.250 or less. The antistatic properties can be further improved by incorporating known antistatic agents such as metal fibers, metal powders, metal compounds, carbon black, metal salts, or various surfactants into this film.
Furthermore, in order to improve low friction properties, various known lubricants can be added to the film (Fig. 5) or coated on the film surface. (Figures 6 and 7). In particular, when a molecularly oriented high-density polyethylene film having a density of 0.94 g/cc or more is used, an inexpensive low-friction sheet with excellent low friction properties, abrasion resistance, and rigidity can be obtained. In the present invention, the low-friction molecule-oriented high-density polyethylene resin film is manufactured using the inflation method or T
It can be obtained by the die method etc. (including single extrusion method and co-extrusion method in each manufacturing method), but in order to obtain these, when using the inflation method, the blow ratio must be within the range of 1.1 to 2.0. Well,
Preferably, the film is formed within the range of 1.2 to 1.6. When stretching is used, the stretching ratio may be within the range of 1.5 to 7 times, preferably
It is within the range of 2.0 to 4.0 times. In terms of low friction, abrasion resistance, and film formability, sheets made of high-density polyethylene resin with a melt index (ASTMD1238) of 0.1 to 10 g/10 min and a density (ASTMD1505) of 0.940 to 0.970 g/cm ³ are recommended. preferable. In addition, this low-friction molecule-oriented high-density polyethylene resin film contains fluorine-containing compounds described in JP-A-50-145482, silicone such as dimethylpolysiloxane, paraffin wax, higher alcohol, higher fatty acid, It is possible to further improve the low friction properties by mixing and adding known lubricants such as fatty acid salts, coating the film surface with the above-mentioned lubricant, or providing various irregularities on the surface to be attached to the tape roll. preferable. Fig. 8 shows an example in which an aluminum vapor deposited layer 2 is provided on a low-friction molecular-oriented high-density polyethylene resin film 11 that has been molded in advance, and of course Fig. 4 also applies to a low-friction sheet for tape rolls having the structure shown in Fig. 8. The modification example shown in FIG. 7 is conceivable. Next, the present invention will be explained in more detail with reference to Examples. (Comparative example) Using Hi-zex5000SR high-density polyethylene resin (manufactured by Mitsui Petrochemical Co., Ltd.) with a density of 0.955 g/cm ³ , an blown film with a blow ratio of 1.3 and a thickness of 80 μ was obtained, and this was used as a low-friction film. It was made into a sheet. This low friction sheet is designated as A and is shown in FIG. Furnace type carbon black (manufactured by Mitsubishi Kasei Corporation) is placed in the film A mentioned above.
A low-friction sheet was created by adding 10% of the film. This low friction sheet is designated as B and is shown in FIG.
These A and B are conventional products. The surface of the low friction sheet A obtained above that is opposite to the surface in contact with the tape roll (back surface) is subjected to corona discharge treatment (surface tension is improved to 38 dyne/cm), and then a thin aluminum film with a thickness of 50 Å is vacuum evaporated. A low friction sheet with a total thickness of about 80μ was obtained. This low friction sheet is designated as C. (Example) In addition, the opposite surface (back surface) of the low friction sheet A obtained above in contact with the tape roll was subjected to corona discharge treatment (the surface tension was improved to 38 dyne/cm), and the thickness was further increased to 100 Å and 600 Å. A thin aluminum film was vacuum-deposited to obtain a low-friction sheet with a total thickness of about 80μ. These low-friction sheets are shown in FIG. 1 as D and E, respectively. Next, the surface opposite to the surface in contact with the tape roll (back surface) of the low-friction sheet A obtained above was subjected to corona discharge treatment (surface tension improved to 42 dyne/cm), and a thin aluminum film with a thickness of 200 Å was further applied under vacuum. After the vapor deposition, a yellow vinyl acetate-based protective layer 3 with a dry thin thickness of 2 μm was applied to the aluminum vapor-deposited surface to obtain a beautiful low-friction sheet with a golden luster and a total thickness of 82 μm. This low friction sheet is shown as F in FIG. Next, the surface of the low-friction sheet A containing 0.5% by weight of dimethylpolysiloxane (manufactured by Shin-Etsu Chemical Co., Ltd.) opposite to the surface in contact with the tape roll has a small corona discharge (the surface tension is
(improved to 40 dyne/cm) and further vacuum-deposited a 100 Å thin aluminum film to obtain a low-friction sheet with a total thickness of approximately 80 μm. This low friction sheet is designated as G and the fifth
As shown in the figure. These low friction sheets A, B, C, D, E, F,
When the suitability of G was evaluated, the results shown in Table 1 were obtained.

【table】

[Effect of idea]

According to the present invention, a molecularly oriented high-density polyethylene resin film made of high-density polyethylene resin, which is an inexpensive general-purpose resin, is used, so it is low cost and has excellent low friction and wear resistance. By providing an aluminum evaporated layer with excellent antistatic effect on the back side, the antistatic property has been greatly improved, so when the low friction sheet for cassette tape is charged, magnetic powder and other dust will be removed from the tape. This causes damage to the sound quality of the tape, and in the case of low-friction sheets for 8mm film, in addition to the adhesion of photographic emulsion powder and other dust, static electricity causes so-called static marks. This is because the fear that the image quality of the film would be significantly impaired has been eliminated. Furthermore, it is possible to obtain an inexpensive low-friction sheet for tape rolls that has a metallic appearance and has high commercial value.

[Brief explanation of drawings]

The accompanying drawings are for explaining the present invention, and FIGS. 1 and 4 to 8 are cross-sectional views showing representative examples of the low-friction sheet according to the present invention. FIGS. 2 and 3 are cross-sectional views showing typical examples of conventional low-friction sheets, respectively. 1...Low-friction molecule-oriented high-density polyethylene resin film, 1a...Low-friction molecule-oriented high-density polyethylene resin film with carbon black added to 1, 1b...Low-friction molecule-oriented high-density polyethylene resin with lubricant added to 1. Film, 2...Aluminum vapor deposited layer with vacuum vapor deposited aluminum thin film,
3...Protective layer, 4...Low friction layer, 4b...Low friction layer added with a lubricant, 11... Low friction molecular oriented high density polyethylene resin film subjected to molding processing.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) A molecularly oriented high-density polyethylene resin film with a thickness of 30 to 150μ having a surface (surface) with a low coefficient of friction that contacts the tape roll, the surface opposite to the surface that contacts the tape roll ( surface tension
Thickness after surface treatment to be less than 42dyne/cm
A low-friction product for tape rolls, which has an 80-600 Å aluminum vapor deposition layer and has a peeling voltage of 21 volts or less on both the front and back surfaces, a static friction coefficient of 0.250 or less on the front surface, and a static friction coefficient of 0.325 or more on the back surface. sheet. (2) The low-friction sheet for tape rolls according to claim 1, wherein the molecularly oriented high-density polyethylene resin film contains a lubricant.