JPS63170018A - Biaxially oriented polyethylene terephthalate film of favorable slit property - Google Patents

Abstract

PURPOSE:To contrive a reduction in dropout of a video tape where a magnetic layer is provided on a film and prevention of clogging of a magnetic head, by optimizing shock-resistant strength and tearing strength of the film. CONSTITUTION:Suitable raw materials of polyethylene terephthalate film is manufactured by adding fine particles non-soluble in the system and precipitating particles having at least a kind of alkal metals or alkaline earth metals as its part of constitutent ingredient. Sufficient vacuum drying and melt extrusion of the obtained PET raw materials are performed, a molten polymer is filtered, molded into a sheetlike state with a mouthpiece and an unoriented sheet is manufactured by cooling and solidifying the same. Then the film is heat-treated. After cooling of the heat-treated film to some extent, the same is cooled gradually down to a room temperature, and a biaxially oriented PET film is obtained. Shock-resistant strength Fi (kg.cm/mm<2>) and tearing strength Ft (g/mm) of the PET film satisfy Ft<=14.8 Fi+1067, and the strength becomes optimum when the Fi is 20 or higher and the Ft is 400 or higher.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a biaxially oriented polyethylene terephthalate film with good slitting properties. The present invention relates to a biaxially oriented polyethylene terephthalate film that exhibits good slitting properties when used as a base material for disks, etc.

[Prior Art] As a biaxially oriented polyethylene terephthalate film with good slitting properties, one is known that has an average refractive index within a specific range, a somewhat low degree of plane orientation, and a limited number of protrusions on the surface ( JP-A-58-23323>.

[Problems to be Solved by the Invention] However, the above-mentioned conventional film has good slitting properties in the sense that the cut edges do not easily bulge when slit. It is something. In the present invention, the term "good slitting performance" means that when the film itself or a film with a magnetic layer placed on it is slit at high speed, it is difficult for whiskers or powder to come out from the cut end. If a large amount of whiskers and powder are produced during slitting, these will adhere to the magnetic layer and cause quality defects such as dropouts (missing signals), so improvement in slitting performance in this sense is strongly desired. An object of the present invention is to provide a biaxially oriented polyethylene terephthalate film that has excellent slitting properties in the sense that it does not easily generate whiskers or powder.

[Means for solving the problems] The present invention provides a film impact strength F i, (kg-cm/
mm2), tear strength Ft (q/mm) is Ft≦14
．． 8Fi +1067, Fi≧20, and Ft≧400, and its main feature is a biaxially oriented polyethylene terephthalate film with good slitting properties.

First, polyethylene terephthalate (hereinafter referred to as PET) of the present invention
abbreviated as ) film impact strength Fi(k(] −c
m/mm 2 ) and tear strength F t (g/mm) is Ft
≦14.8Fi +1067 must be satisfied. If this inequality is not satisfied, whiskers are likely to occur during slitting, which is undesirable.

Next, Fi must be 20 or more and Ft must be 400 or more. If any of these is removed, the film becomes brittle and easily torn or torn, which is not practical.

Note that the PET of the PET film of the present invention may contain a diethylene glycol component in an amount of 0.2 to 2.0% by weight. In addition, the intrinsic viscosity of PET (25°C ortho-
(measured in chlorophenol) is preferably in the range of 0.58 to 0.65, preferably 0.61 to 0.64 dl/g.

The method for producing the film of the present invention is not particularly limited, and any method may be used, but one example of a preferred production method will be described below.

First, the PET raw material suitable for producing the film of the present invention is prepared by adding insoluble fine particles to the system during the polycondensation reaction, and then adding at least one kind of alkali metal or alkaline earth metal as a constituent component during the polycondensation reaction. It is manufactured by precipitating particles (so-called precipitated particles) that are part of the To be more specific, when producing a polyester by transesterifying or esterifying terephthalic acid or its ester-forming derivative with ethylene glycol and subsequently carrying out a polycondensation reaction, optional At this point, insoluble particulate matter (preferably those with a specific surface area of 5TIi/Q or more) is added to the system, and one or more alkali metals or alkaline earth metals are added as part of the constituent components during the polycondensation reaction. This is a manufacturing method in which particles are precipitated.

This method of incorporating diethylene glycol into the PET raw material can be achieved by adding a desired amount of diethylene glycol to the above-mentioned ethylene glycol.

The PET raw material made in this way is sufficiently vacuum-dried according to a conventional method, then fed to an extruder for melt extrusion, the molten polymer is filtered, formed into a sheet with a die, and then wrapped around a cooling drum and cooled. By solidifying, an unstretched sheet is produced. This unstretched sheet is stretched 3 to 5 times in the longitudinal direction of the film above the glass transition temperature. Thereafter, the film is stretched in the width direction in multiple stages while increasing the stretching temperature little by little. In the initial stretching in the width direction, the stretching temperature is set at a relatively low temperature of 85 to 95°C, and the film is stretched 2.0 to 2.3 times. 2
In the second width stretching, the temperature was raised to 96-105°C, and 1.
Stretching is performed 3 to 1.7 times.

The third stretch is 1.1-5 at a temperature of 101-110'C.
= Stretching is performed by ~1.5 times. By performing multi-stage stretching in this manner, a stable fine structure in which molecules are well arranged in the width direction of the film can be obtained.

Furthermore, if necessary, stretching in the width direction may be repeated three or more times to further align the molecules in the width direction. However, care must be taken to ensure that the molecular orientation in the width direction is not increased too much and the mechanical properties in the longitudinal direction of the film are not deteriorated.

The film is then led to a heat treatment zone where 190~
Heat treat at 220'C for 2-10 seconds. In this heat treatment zone, 1 to 8% of the original length in both the longitudinal and width directions.
The biaxially oriented PET film of the present invention is obtained by introducing the heat-treated film into an intermediate cooling zone of 80 to 120'C, cooling it to some extent, and then gradually cooling it to room temperature. be able to.

[Applications] The biaxially oriented PET film thus obtained can be used in various magnetic recording media such as video tapes, audio tapes, etc. by providing a magnetic layer on one or both sides thereof.
It is processed and used as floppy disks, etc. The magnetic layer may be one in which magnetic powder is applied together with a binder, or one in which a ferromagnetic material is made into a thin film by vacuum evaporation, sputtering, ion blasting, plating, or the like. Although the film of the present invention can be used for the various magnetic recording media mentioned above, it is particularly effective for videotape applications.

When slitting a videotape, if there are a lot of hairs and powder on the end face, not only will dropouts increase, but these hairs and powder can also clog the magnetic head. This is why the film of the present invention is particularly effective.

As mentioned above, the film of the present invention is mainly used for magnetic recording media, especially video tapes, but it can also be used for other purposes.
For example, it can be effectively used in applications where slitability is an issue, such as in graphics, stamping foils, electrical insulating materials, dielectrics for capacitors, and packaging.

[Function] By optimizing the impact strength and tear strength of the biaxially oriented PET film, the present invention eliminates hairs and powder during slitting, especially when slitting with a magnetic layer placed on the film. This is what we found out that it becomes less likely to occur. A slit is a destructive phenomenon in which a film or a film and a magnetic layer are cut together, and it is extremely difficult to clearly analyze the relationship between such destruction and film properties. However, since this destructive phenomenon and the destructive characteristics of the film itself are closely related to each other,
It is believed that by specifying the impact properties and tear properties of the film, we were able to contribute to improving the slitting properties.

[Method for measuring properties and evaluating effects] (1) Evaluation of slitting properties A magnetic coating solution with the following composition was applied to one side of a PE film with a thickness of 14.5 μm so that the film thickness after drying was 3 μm. Coat.

(Parts by weight) Polyester polyurethane resin 35 PVC/maleic acid copolymer 30 α-alumina
15 car phone black
3 oleic acid
5 Amyl stearate 4 Triisocyanate compound 22 Ferromagnetic metal powder
300 butyl acetate
300 methyl isobutyl ketone 3
After 00 coating, it is oriented in a DC magnetic field, dried, and then calendered. This sheet is slit into 1/2 inch width using a shear cutter to make a videotape. The slit location made by this shear cutter is visually observed, and the degree of generation of whiskers and powder is evaluated by dividing it into the following five grades.

Slitting property A: There is very little generation of whiskers and powder.

B: Few.

C: Normal level.

D: Slightly higher.

E: A lot.

-〇- (Note) The level of slitting properties of currently commercially available biaxially oriented PET films for video tapes is
C or D.

(2) Impact resistance According to the method specified in ASTM-D-256, the Charpy impact strength of the film (unit: kg - cm/mm) was measured using a new Charpy impact tester manufactured by Toyo Seiki.
2) was measured. According to ASTM, strength is expressed in kg.
・Cm is expressed here by dividing it by the cross-sectional area of the film. The impact strength value was determined when the longitudinal direction of the film was set horizontally between two supporting points.

(3) Tear strength To measure tear strength, an Elmendorf tear tester manufactured by Toyo Seiki Co., Ltd. was used. 50.8 (longitudinal direction) x 63.
Take a 5 mm (width direction) film sample, make a 12.7 mm cut in the width direction at right angles in the center of both claws along the longitudinal direction, and calculate the tearing force for the remaining 50.8 mm (
q) was calculated. This force was divided by the thickness of the film to obtain the tear strength.

[Example] The present invention will be explained using the following examples and comparative examples, but the present invention is not limited to these examples.

Example 1 100 parts by weight of dimethyl terephthalate, 69 parts by weight of ethylene glycol, 0.5 parts by weight of diethylene glycol,
Using 0.09 parts by weight of calcium acetate as a catalyst, a transesterification reaction is carried out by a conventional method, and the resulting product contains 0.03 parts by weight of antimony trioxide, 0.3 parts by weight of lithium acetate, and 0.2 parts by weight of trimethyl phosphate. Parts by weight and silicon dioxide fine powder (specific surface area: 180 m/Cl) were added, and polymerization was carried out in a conventional manner to obtain polymer pellets with an intrinsic viscosity of 0.635. After vacuum-drying the pellets at 180°C for 8 hours, the pellets are fed to an extruder, melt-extruded at 280°C, and discharged in the form of a sheet from a T-type nozzle via a gear pump and filter. It was wound around a cooling drum at 40'C and cooled and solidified to produce an unstretched sheet.

During this cooling, in order to improve the adhesion between the molten sheet and the drum surface, a wire electrode is placed on the molten sheet side, and a DC voltage of 8KV is applied to it to ensure that the molten sheet is well adhered to the drum. did.

This unstretched sheet is stretched 3.5 times in the longitudinal direction at 85°C, then the stretched sheet is introduced into a stenter, both ends of the sheet are held with clips, and stretched 2° in the width direction at 90°C. Stretched. Guide this sheet to the second stentor zone and
It was re-stretched to 1.5 times in the width direction at 6°C, and then further stretched to 1.3 times in the width direction at 105°C in the third stenter zone.

Next, this film was directly introduced into a heat treatment zone without being cooled, and was tension heat-set at 205°C for 2 seconds.
Next, at the same temperature, relaxation is performed by 2% in the longitudinal direction and 3% in the width direction (respectively relative to the original length), and then tension heat set again at the same temperature for 5 seconds, and the material is directly transferred to a 1oo'c intermediate cooling room. ,
After performing intermediate cooling here, a relaxation of 1% of the original length is given in the longitudinal direction at this outlet, and then the biaxial film is made into a biaxial film with a thickness of 14.5 μm. An oriented PET film was obtained. The intrinsic viscosity of this film is 0.61 dl/CI, and the impact strength is 25! l]・cm
/mm 2 , and the tear strength was 500 p/mm.

Using this film as a base material, a videotape was made by the method described above, and the slitting properties of the film were evaluated. The slitting properties were graded A, with very little whiskers or powder.

Examples 2 to 11 and Comparative Examples 1 to 9 Among the various conditions of Example 1, the amount of additives during polymerization, stretching temperature, stretching ratio, heat setting temperature, and degree of relaxation during heat setting were variously changed. By doing this, samples with different values of impact strength and tear strength were made.

The results of the slitting performance evaluation of these films were summarized in the first
As shown in the figure. These results show that films having characteristic values within the range of the present invention have excellent slitting properties.

In the figure, the symbols ◎, 01, Δ, and X correspond to slit properties A, B, CSD, and E, respectively.

[Effects of the Invention] The present invention improves the slip resistance of the film, particularly for video tapes with a magnetic layer provided on the film, by optimizing the impact strength and tear strength of a biaxially oriented PET film. This has the effect of improving slitting properties.

The property of not easily generating whiskers or powder during slitting is effective in reducing dropouts of video tapes and preventing clogging of magnetic heads, and in this sense, the film of the present invention is particularly useful as a base material for video tapes.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the evaluation results of examples and comparative samples. The vertical axis is tear strength, and the horizontal axis is impact strength. ◎, ○, open, △, and X represent the quality of the slitting properties.

Claims (1)

[Claims] The film impact strength Fi (kg cm/mm^2) and tear strength Ft (g/mm) are in the ranges of Ft≦14.8Fi+1067, Fi≧20 and Ft≧400. Biaxially oriented polyethylene terephthalate film with good slitting properties.