JPS59203230A - Biaxially oriented polyester film - Google Patents

Abstract

PURPOSE:To solve problems such as elongation, contraction, strain, biased elongation, etc. of a magnetic tape for long-time recording and reproducing in the stage of starting and stopping by specifying respectively the thickness, longitudinal Young's modulus, longitudinal stiffness and surface roughness of the biaxially oriented polyester film of said tape. CONSTITUTION:A polyester film consisting of the polyethylene terephthalate or polyethylene-2,6-naphthalene dicarboxylate which is biaxially stretched and oriented so as to have 4-6mu film thickness, >=750kg/mm.<2> longitudinal Young's modulus, >=40mg longitudinal stiffness, <=0.5mu surface roughness PV (peak to valley) value and a CLA (centerline roughness) value ranging 0.012-0.040mu is used for a base film for an audio cassette having 120-180 minutes recording and reproducing time. The base for the tape which has high mechanical strength dimensional stability and excellent running property and is free from elongation, contraction, strain, biased elongation, flexing sticking during winding, etc. is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a polyester film 1r for audio cassette tapes having a recording and playback time of 20 minutes to 180 minutes.
Regarding this.

Prior Art Polyester film has become a versatile material as a base for audio tapes, video tapes, computer tapes, etc. due to its excellent mechanical strength and dimensional stability.

Recently, in the field of magnetic recording tapes, especially audio cassette tapes, there has been a growing demand for longer lengths, smaller sizes, and higher densities, and there is a strong desire for thinner base films.

Currently, the commonly used audio cassette tapes on the market have recording and playback times of 60 minutes and 90 minutes.
This is a generalized version of the system. In order to meet the demand for recording long-term content such as lectures and conferences, cassette-type audio tapes capable of long-term recording are required, and 120-minute audio cassette tapes are already commercially available. However, the existing 120-minute audio cassette tapes are prone to various problems in practical use (some hardware manufacturers are
Currently, a warning is pasted on the hardware telling people to refrain from using audio cassette tapes.

Problems to be Solved by the Invention In order to incorporate tapes into cassettes of the same standard, as recording and playback times become longer, it is natural that
The tape needs to be thin (thin), and the base film that is the base material also needs to be thin accordingly.Currently 60
Various practical problems that occur with minute and 90 minute tapes are more likely to occur (it is inevitable that they will occur).

Practical problems include, for example, tape expansion/contraction and distortion due to tension fluctuations at the start and stop of tape running, one-sided elongation and bending of tape ends, and splicing of running tape.

It is predicted that these troubles are related to some basic physical properties of the base film for tapes.According to the findings of the present inventor, in fact, the basic physical properties of the base film and the practical Relationship with troubles (/C') The physical property that is involved in the tape's expansion and contraction due to tension fluctuations at the start and stop of the tape, and the recovery of φ warping is the Young's modulus of the base film; It has been found that the apparent stiffness, surface properties, static electricity, etc. of the base film are involved in the uneven stretching, bending, and wrapping of the end surface of the tape.

Structure and Effects of the Invention The present inventor has solved these practical problems that sometimes occur with the current 60-minute and 90-minute audio cassette tapes, and which will occur even more frequently with 120-minute and 180-minute audio cassette tapes. As a result of intensive research, we have found that a biaxially oriented polyester film with a base film having a longitudinal Young's modulus and apparent stiffness above a certain value, and a tape surface roughness within a certain range, has been developed as an audio chip. The present invention was achieved based on the discovery that the film is virtually trouble-free in use and has properties that make it practical as a base film for 120-minute or 180-minute audio cassette tapes.

That is, the present invention provides a coating-type base film for audio cassette tapes with a recording and playback time of 120 to 180 minutes, a film thickness of 4 μ to 6 μ, a longitudinal Young's modulus of rsoky/- or more, and a longitudinal stiffness of rsoky/- or more. The surface roughness is PV value of 0.5μ or less and CLA value of 0.
．． A biaxially oriented polyethylene-2,6-naphthalene dicarboxylate or polyethylene terephthalate film characterized by having a particle size ranging from 0.012μ to 0.040μ.

Polyester in this context is a polymer whose main component is bi) polyethylene terephthalate, and copolymerized components (e.g., glycols such as propylene glycol, butylene glycol, inphthalic acid, phthalate, adipic acid, etc.) dicarboxylic acids such as dicarboxylic acids). Further, other polymers, lubricants, antistatic agents, pigments, and other various additives may be added in an amount of 10 weight or less.

Furthermore, (b) the polyester contains a polymer consisting of 2,6-naphthalene dicarboxylic acid and ethylene glyfur, but it also contains other polymers, lubricants, antistatic agents, pigments and other various additives of up to 10% by weight. It can also be added.

As the magnetic material used in the present invention, γ-F(+, 01,
Co-containing 7-Fe, 0. , CrCh, Fe-co or Fe Co Ni, etc., and a binder whose main components are vinyl chloride, vinyl sulfate, polyurethane, nitrocellulose, copolymers or mixtures thereof, or other resins. and those coated with magnetic pigments consisting of C.
It also includes those in which a layer of metal such as Co--Cr, Co--Cr, or other metals is deposited by a vacuum deposition method such as vacuum deposition, sputtering, or ion blasting.

The method for producing the biaxially oriented film of the present invention is not particularly limited, but may be carried out vertically to horizontally, horizontally to vertically, or vertically to horizontally once again.

It can be produced by a known method of sequential stretching such as longitudinal-horizontal stretching, or a combination of simultaneous biaxial stretching.

In the film of the present invention, the Young's modulus in the longitudinal direction is 750.
kg/- or more, it is possible to prevent expansion and contraction of the tape during electronic editing of the tape or when starting and stopping the tape, and it is possible to quickly recover from tape distortion. The Young's modulus in the longitudinal direction is preferably Gooky/- or more.

In addition, in the film of the present invention, the longitudinal direction is the extrusion direction during film formation, and refers to the longitudinal direction of the tape, that is, the longitudinal direction of the film.

Furthermore, by setting the stiffness in the longitudinal direction to 40 square or more, the rigidity of the tape increases and troubles do not occur when the tape runs. Conventional tapes have weak elasticity, which causes them to ``sag,'' making the tape's running performance unstable, causing problems such as one-sided stretching of the tape end, bending, and even splicing of the cape. However, the present invention can solve such problems.

Furthermore, when the surface roughness of the base film is such that the pv value and CLA value are within the ranges specified in the present invention, a film with excellent running properties can be obtained.

In general, as the pv value increases (the CLA value tends to increase as well, the trends do not necessarily match and may be reversed).Film running properties are determined by the film running condition (film surface roughness). It is thought that it depends on the Young's modulus, the running speed of the film, etc., but when the running property and surface roughness pv value of a high Young's modulus film such as the film of the present invention is 0.5μ or less, the CLA value is 0.01577.
It has been found that the above materials are excellent in the above properties.

If the pv value exceeds 0.5μ, the running properties will deteriorate.

If the CLA value is lower than 0.012μ, the runnability will be poor (on the contrary, if it is higher than 0.040μ, the audio characteristics will be poor (according to 1. must be satisfied.

The following describes the standard method for determining the various property values specified in the present invention. speed 5
000 l/min using an in-situ universal tensile tester. Young's modulus was calculated from the tangent to the rising portion of the obtained load-elongation curve.

<Stiffness> By gripping both ends of a test piece of a predetermined length with chucks to form a loop, placing the loop so that it touches a U-gauge surface, and reading the force applied to the U-gauge sample with a millivolt meter. , to measure the stiffness of the film.

(Measurement n number of m sample width; a, S 1 to sample length; 60n+ jack interval; 15.5 axis measurement n number; 5 (pv value and CLA value) PV (peak) indicating surface roughness in the present invention・peak-to-valley) value and CLAC center line + 7 cent
er LineAyerage) ) values are determined by the following methods.

It was measured by

pv value: The roughened film is measured using a stylus surface roughness tester (S+, URFCOM 3B) manufactured by Tokyo Seimitsu Co., Ltd. under the conditions of a needle radius of 3μ and a load of 0.19. For a length of 2.6 m, the standard length direction is multiplied by 50,
Magnify the surface roughness direction 20,000 times, overlay a chart, and extract the standard length from the cross-sectional curve.Among the straight lines parallel to the average line, select the first peak from the highest and the first peak from the deepest. Select the line that passes through the bottom of the valley, divide the distance between these two lines by the vertical magnification, express the value in microns, and calculate this PV.
(Represented as an average value of , 6xo pieces. Note that the measurement is performed in the vertical direction.

CLA value: Cut out a part of measurement length L (2 standard lengths) from the roughened film roughness curve in the direction of its center line, and set the center line of this cut out part on the X axis and the direction of vertical magnification. Y
When the roughness curve is expressed as y = f(z) as the axis,
The value given by the following formula is expressed in μ units. Measurements are performed on 8 samples, 8 samples with the largest value are excluded, and the average value of the 5 samples is expressed. Note that the measurement is performed in the vertical direction.

EXAMPLE Below, Example 4 will be given to further specifically explain the present invention.
~5,9~10 Polyethylene terephthalate chips with an intrinsic viscosity of 0.62 to which kaolin with an average particle size of 0.82μ was added in a range of 0.20 to 0.50 weight φ were melt-extruded at 280°C at a temperature of 4.
It was cooled at a temperature of 0°C to form an unstretched film, and then 8
4.5 times in the vertical direction at 0℃, then 3 times in the horizontal direction at 95℃
．． Stretched 4 times and further heat-set for 5 seconds at 2001: 4~
A stretched film of 6μ was obtained.

Comparative Examples 1 to 2, 3 to 4 Using the same polyethylene terephthalate chips as in Examples 4 to 5 and 9 to 1o above, an unstretched film was made under the same conditions as in the same example, and then stretched in the longitudinal direction at 75°C for 3 .6 times, then stretched 3.9 times in the transverse direction at 1'05°C, and further stretched 21 times.
The film was heat-set at a constant length of 5° C. for 5 seconds to obtain a stretched film with a thickness of 4 to 6 μm.

Examples 1 to 3, 6 to 8 Using the same polyethylene terephthalate naps as in Examples 4 to 5 and 9 to 1o above, an unstretched film was made under the same conditions as in the same example, and then this was stretched in the longitudinal and transverse directions. at 90'C
Biaxially stretched 3.5 times and 3.8 times, respectively, and then 4 times
4011? : Stretched again in the longitudinal direction by t and S times, and then stretched at 230°C.
The film was heat-set to a fixed length for 5 minutes to obtain a stretched film with a thickness of 4 to 6 μm.

Example 11 Kaolin with an average particle size of 0.82 p is 0.20 to 0.50
Polyethylene terephthalate having an intrinsic viscosity of 0.60 (however, 5 moles of the glycol component was copolymerized with polyethylene glycol having an average molecular weight i of 3000) added in a range of % by weight was added to the above-mentioned Examples 4 to 5 and 9. The film was stretched and heat-set under the same conditions as in 10 to obtain a 5.6 μm stretched film.

Example 12 - 7 Polyethylene 2-26-naphthalene chips with an intrinsic viscosity of 0.83 to which kaolin with an average particle size of 0.82 μm was added in a range of 0.20 to 0.50% by weight were melt-extruded at 315°C.
It was cooled with a roll at 40°C to form an unstretched film, and then stretched 3.7 to 4.5 times in the longitudinal direction at 110 to 115°C and then 2.7 to 3.5 times in the transverse direction at 115 to 130°C. Heat set at ~250°C for 5-10 seconds for 4-6
A stretched film of μ was obtained.

In the film obtained under these conditions, 70 wt% of γ was added.
A coating consisting of -Point and 3wt% binder was applied. This binder consists of 5 wt% urethane rubber, 3.5 wt% nitrocellulose, and 1.5 wt%
of vinyl chloride, 90vrt% methyl ethyl ketone,
Further, an incyanate compound was added as a curing agent at 15 vt% based on the resin. A magnetic substance-coated original fabric having a sheath width of 600 mm was obtained by coating in a conventional manner.

A 5/20-inch microslit was made using a slitter with a shear set (model RT, manufactured by Uchizai Seisakusho Co., Ltd.) on this coating material.

The audio characteristics were measured and evaluated in the examples using a fully automatic Nice Torsion Analyzer AA-501 manufactured by Tektronix. ) and compared with our own standard tape, each was evaluated as follows.

0 input/output sensitivity ○...The output sensitivity is low (not high) compared to the input sensitivity.

Δ: The output sensitivity is slightly lower than the input sensitivity, but there is no problem in practical use.

×: Output sensitivity is low compared to input sensitivity and cannot be used.

O8/N ratio ○: Comparable to the standard tape for comparison, no problems.

Δ: Inferior to the reference tape for comparison, but no problem in practical use.

×: Inferior to the standard tape for comparison and cannot be used.

Furthermore, 1.2 of the evaluation of the initial sound quality disturbance f+ when stopping Arp running and starting writing. a & ma as below.

1...Disorder is not recognized.

2... A little disturbance is observed, but there is no problem in practical use.

3...Unusable due to large turbulence 1: Unusable.

In addition, the presence or absence of elongation, bending, and splicing of the end face of the tape was visually evaluated.

Procedural amendment document, J. 1980, )) 1st, Commissioner of the Japan Patent Office 1 Indication of the case Patent application No. 1987-77387 2, Title of the invention Biaxially oriented polyester film 3 Person making the amendment Relationship with the case Patent application 1-11 Minamihonmachi, Higashi-ku, Osaka (30) Representative of Teijin Limited Tomoo Tokusue 6 Contents of amendment (1) Specification, page 9, line 10, “Yasugu rate” has been changed to “
"Young Army," he corrected.

(2) Same, page 9, line 11, “test width” is “sample medium”
I am corrected.

(3) Same, page 12, line 6, "Extrusion temperature 40°C" is corrected to "Extrusion temperature 40"C.

that's all

Claims (2)

[Claims] (1) A base film coated with a magnetic layer and used for audio cassette tapes with a recording and playback time of 120 to 180 minutes, with a film thickness of 4μ to 6μ, a longitudinal Young's modulus of rsokg/m7 or more, The stiffness in the direction is 40mg or more, the surface roughness is pv (0.5 in z)
μ or less and CLA value 0.012 p to 0.040
A biaxially oriented polyester film characterized in that it is in the met range. (2) The biaxially oriented polyester film according to claim 1, wherein the polyester is polyethylene terephthalate or polyethylene-2,6-naphthalene dicarboxylate.