JP3834863B2 - Biaxially oriented polyethylene-2,6-naphthalate film and method for producing the same - Google Patents

Description

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【表２】

【００３１】
【表３】

【００３２】
【発明の効果】
本発明では、縦方向または横方向のいずれかの方向のヤング率が１０００ｋｇ／ｍｍ²以上１３５０ｋｇ／ｍｍ²以下であり、かつ縦方向と横方向のヤング率の和が１６００ｋｇ／ｍｍ²以上２７００ｋｇ／ｍｍ²以下であり、さらに縦方向（ＭＤ）の厚みむらと横方向（ＴＤ）の厚みむらの比（ＭＤ／ＴＤ）が０．９７以上１．５以下であることを特徴とする二軸配向ポリエステルフィルムとしたので、非常に高い強度のフィルムを供給でき、特に磁気テープ、中でも記憶容量２０ＧＢ以上のディジタルデータストレイジ用として用いる場合、薄膜化しても品質を向上させることができる。したがって、磁気記録媒体用途において特に有益に用いることができるが、磁気記録媒体用途以外にもコンデンサー用、包装用など機械強度の要求される様々な用途に広く活用することが可能である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a biaxially oriented polyester film and a method for producing the same. More specifically, the present invention relates to a biaxially oriented polyester film suitable for magnetic recording media, particularly for digital data storage having a storage capacity of 20 GB or more, for capacitors, and for packaging. It relates to the manufacturing method.
[0002]
[Prior art]
Polyester films are used in a wide range of fields such as magnetic recording media, electrical insulation, and packaging materials because of their excellent heat and mechanical properties. In particular, in magnetic recording media applications, the tape thickness has been reduced to increase the recording time and the cassette size to be compact, and the polyester film as the base film must bear the mechanical strength that has been reduced due to the tape thickness reduction. Has occurred. Japanese Patent Application Laid-Open No. 50-45877 discloses a polyester film having improved mechanical strength, and examples of a method for strengthening include a method in which re-longitudinal and re-lateral stretching are further performed after biaxial stretching, for example, No. 102303, Japanese Patent Laid-Open No. 2-208323, and the like, but the recent demand for higher strength by reducing the thickness of the tape has become very strict. Due to lack of waist when used as a tape and poor recording with a video tape recorder and contact with the playback head, the quality of the recorded image is degraded, and dirt that has accumulated on the head, which the tape itself has previously handled. The cleaning effect is insufficient due to a decrease in the rigidity of the tape, recording loss due to head contamination occurs, and the reproduced image is disturbed.
[0003]
[Problems to be solved by the invention]
The present invention solves the above problems, provides a biaxially oriented polyester film having mechanical properties dramatically improved from the conventional one, and improves the quality even when the final magnetic tape is thinned. That is what you want.
[0004]
[Means for Solving the Problems]
The biaxially oriented polyethylene-2,6-naphthalate film of the present invention along this purpose, either direction Young's modulus in the longitudinal or transverse direction is at 1000 kg / mm ² or more 1350 kg / mm ² or less, and the vertical direction the sum of the transverse Young's modulus is at 1600 kg / mm ² or more 2700 kg / mm ² or less, the ratio of the thickness unevenness of the thickness irregularity and lateral (TD) further machine direction (MD) (MD / TD) is 0. consisting of those wherein the at 9 7 to 1.5.
[0005]
In addition, the method for producing a biaxially oriented polyethylene-2,6-naphthalate film according to the present invention provides a longitudinal uniaxial birefringence of 0.20 or more and a density of 1.345 g / cc or more when producing a film having the above characteristics. It consists of the method characterized by extending | stretching a stretched film again after transverse stretching at the temperature (Tcc + 20 degreeC) below (cold crystallization temperature Tcc-20 degreeC) of this uniaxially stretched film.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Examples of the polyester in the present invention include polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, polyethylene-α, β-bis (2-chlorophenoxy) ethane-4, 4′-dicarboxylate and the like. Among these polyesters, polyethylene terephthalate, polyethylene-2,6-naphthalate, polyethylene-α, β-bis (2-chlorophenoxy) ethane-4, 4′-dicarboxylate are preferable, particularly polyethylene-2, 6-Naphthalate is very effective for obtaining the Young's modulus within the range of the present invention. In addition, the polyester of the present invention may be one kind of the above-mentioned polymers, a copolymer of two or more polyesters, or a mixture of two or more polyesters. Various additives may be added as long as the effects of the present invention are not impaired. Although not particularly limited, it is preferable that the polyester is polymerized using a germanium compound such as germanium oxide or germanium tetraacetate as a catalyst because it is very suitable for obtaining the Young's modulus of the present invention. In addition, as a compounding quantity, it is preferable that the germanium compound contained in a film is 0.005 weight% or more and 0.03% weight or less with respect to a polymer as a quantity of germanium. Furthermore, it is preferable that it is 0.006 weight% or more and 0.02 weight% or less.
[0007]
Although it is not particularly limited, the biaxially oriented polyester film of the present invention is provided with a slippery property, and it is inorganic in order to improve the handling property in the manufacturing and processing steps and the running property when used as a product magnetic tape. More preferably, it contains inert particles such as particles and organic particles. Examples of inorganic particles include silicon dioxide, calcium carbonate, aluminum oxide, and zirconium oxide. Examples of organic particles include ethyl vinylbenzene-divinylbenzene copolymer, polymethyl methacrylate, and silicone. These inert particles are used alone or in combination of two or more. The particle diameter of these inert particles is not particularly limited, but is preferably 2 μm or less, preferably 0.05 μm or more and 1.5 μm or less.
[0008]
The Young's modulus in either the longitudinal direction (hereinafter sometimes abbreviated as MD) or the lateral direction (hereinafter sometimes abbreviated as TD) of the biaxially oriented polyester film of the present invention is 1000 kg / mm ^2. As mentioned above, it is necessary that it is preferably 1100 kg / mm ² or more, more preferably 1200 kg / mm ² or more. When the Young's modulus of either MD or TD is out of the above range, there is no missing recording at the time of use, which is the effect of the present invention, and a magnetic tape having excellent electromagnetic conversion characteristics cannot be obtained.
[0009]
Furthermore, the sum of the Young's modulus of MD and TD needs to be 1600 kg / mm ² or more, preferably 1800 kg / mm ² or more, more preferably 2000 kg / mm ² or more. When the sum of the Young's modulus of MD and TD is out of the above range, the effect of the present invention cannot be obtained, which is not preferable.
[0010]
Although not particularly limited, when the MD and TD Young's moduli are both 1000 kg / mm ² or more, preferably 1100 kg / mm ² or more, more preferably 1200 kg / mm ² or more, it is extremely effective for obtaining the effects of the present invention. It is.
[0011]
The thickness of the film is preferably 2 μm or more and 7 μm or less, and more preferably 3 μm or more and 6 μm or less. Furthermore, the ratio of the film thickness irregularity of the film thickness unevenness and TD of MD (MD / TD) is 0.9 7 to 1.5, preferably when the upper limit is 1.35 or less, the effect of the present invention This is very preferable because the image quality of a certain magnetic tape is improved.
[0012]
In addition, the biaxial orientation in the present invention means that each of MD and TD is stretched and oriented at a magnification of 1.5 times or more.
[0013]
Next, the manufacturing method of the biaxially oriented polyester film of this invention is demonstrated.
First, the polyester pellets are sufficiently dried, then supplied to a known melt extruder, passed through a filter selected as necessary, and then melt-extruded into a film from a slit-shaped die. This film-like polyester is rapidly cooled and solidified on a casting drum controlled at a temperature of 20 to 60 ° C. to be in an amorphous state. At this time, it is more preferable to improve the adhesion between the drum and the polyester film using a known electrostatic application device in order to obtain a cast film having good moldability and to improve the subsequent stretching.
[0014]
The obtained amorphous polyester film is first stretched and oriented longitudinally. The polyester film is preheated by passing over a sufficiently heated roll, and then stretched longitudinally by utilizing the peripheral speed difference of the roll. The longitudinal stretching method may be one-stage stretching or multi-stage stretching of two or more stages, but multi-stage stretching of two or more stages is particularly suitable for obtaining the Young's modulus within the scope of the present invention. The longitudinal stretching condition is not particularly limited, but the stretching is performed at least 3 times at a temperature of the glass transition temperature Tg or more of the polyester. In the case of multi-stage stretching, a method in which first-stage stretching is first performed at a temperature of Tg + 20 ° C. or more and second-stage stretching is performed at a lower temperature than the first-stage stretching is preferable. For example, when the polyester is polyethylene-2,6-naphthalate, the first stage of stretching is performed at a film temperature of 140 ° C. or higher, preferably 150 ° C. or higher at the time of stretching, followed by a film temperature of 120 to 160 ° C. and 1 The second stage stretching is performed at a temperature lower than the stage stretching temperature. The stretching ratio is preferably 1.5 to 3 times in the first stage and 3 to 6 times in the second stage. In addition, as long as the effect of the present invention is not hindered, one or more stages of stretching may be added between the first stage of stretching and the second stage of stretching. As the material for the roll surface used for longitudinal stretching, it is particularly preferable to use a material having low adhesiveness such as Teflon or silicone.
[0015]
Although not particularly limited, the birefringence (Δn) of the film after uniaxial stretching is 0.20 or more, preferably 0.25 or more and 0.5 or less, more preferably 0.27 or more and 0.4 or less, after uniaxial stretching. very density of the film is 1.345 g / cc or more, preferably 1.347g / cc or more, more to preferably obtain a Young's modulus of the present invention range is less than or equal to 1.347g / cc or more 1.36 g / cc It is effective for.
[0016]
Subsequently, stretching in the transverse direction is performed. Stretching in the transverse direction is not particularly limited, but stretchability is very good when the stretching temperature is stretched within the range of (cold crystallization temperature Tcc-20 ° C) or higher (Tcc + 20 ° C) of a uniaxially stretched film using a known stenter. Therefore, it is particularly suitable for obtaining a film having a high Young's modulus without troubles such as tearing. Further, the transverse stretching may be performed in two stages. At this time, it is preferable that the stretching temperature in the second stage is higher than that in the first stage, and the difference from the subsequent heat treatment temperature is 50 ° C. or less. Although not particularly limited, the fact that the film density after transverse stretching is smaller than the density of the film after longitudinal stretching is a film having a high Young's modulus and good stretchability in subsequent longitudinal and re-lateral stretching. Is particularly preferred in order to stably obtain After stretching in the transverse direction, heat treatment is performed at a temperature of about 150 ° C. to 250 ° C. as necessary. Heat treatment is usually performed under tension, and relaxation treatment is performed in the lateral and / or longitudinal direction as necessary.
[0017]
Furthermore, when re-lateral stretching is performed, heat treatment is not performed after longitudinal or horizontal stretching within the above-mentioned condition range, or even if it is performed, heat treatment is performed at a relatively low temperature of 180 ° C. or less, preferably 160 ° C. or less, and the stenter is removed. It is used for re-lateral stretching. The re-lateral stretching is performed at a relatively high temperature of 150 ° C. or higher, preferably 150 ° C. or higher and 230 ° C. or lower, in a magnification range of 1.1 to 3 times, preferably 1.1 to 2 times. Note that the first lateral stretching and re-lateral stretching may be performed using one stenter or two stenters. If necessary, relongitudinal stretching can be performed before relateral stretching. When re-longitudinal stretching is performed, the stretching is performed at a temperature that is equal to or higher than the previous horizontal stretching temperature and in a magnification range of 1.1 to 3 times. Further, heat treatment is performed as necessary. The heat treatment is performed under normal tension in a temperature range of 150 ° C. or more and 250 ° C. or less, and is performed under lateral and / or longitudinal relaxation as necessary.
[0018]
[Methods for measuring physical properties and methods for evaluating effects]
(1) Set the sample film so that the Young's modulus tensile tester of the film has a width of 10 mm and a length between chucks of 100 mm, and conducts a tensile test at a tensile rate of 200 mm / min under the conditions of 23 ° C. and 65% RH. It was measured.
[0019]
(2) Birefringence (Δn)
The retardation of the film was measured using a Belek compensator for a polarizing microscope, and birefringence (Δn) was determined by the following formula.
Δn = R / d
R: retardation d: film thickness
(3) The film temperature at the time of stretching was measured at an emissivity of 0.98 using a non-contact thermometer (for example, 505 manufactured by Minolta Co., Ltd.).
[0021]
(4) Quantitative determination of germanium The quantitative determination of germanium in the polymer was performed by fluorescent X-ray analysis.
[0022]
(5) Density of film Measured by a density gradient tube method of JIS-K-7112 using a mixed solution of n-heptane, carbon tetrachloride, or an aqueous sodium bromide solution.
[0023]
(6) Electromagnetic conversion characteristics (RF output)
A magnetic coating component having the following composition is kneaded and dispersed in the film, and then 5 parts of Coronate L from Nippon Polyurethane Industry is added to form a magnetic coating, applied with a gravure roll, magnetically oriented and dried. Furthermore, it is cured at a temperature of 75 ° C. and a linear pressure of 220 kg / cm with a calender device (steel roll / nylon roll, 5 stages) and then cured at 70 ° C. for 48 hours. The magnetic tape original fabric was slit into a 1/2 inch width to produce a magnetic tape pancake. Tape from this pancake is stored in a cassette to form a video cassette. Test signals were recorded on this cassette using a home video deck, and RF output was measured using a color video noise measuring device. Judgment criteria for the quality of the characteristic is that the output of the magnetic tape produced using the film of Comparative Example 1 is the standard (0 dB), the RF output is larger than +1.5 dB, the characteristic is better, and the image quality is less than +1.5 dB. Since it worsened, it was considered as a characteristic defect.
Ferromagnetic powder Co-γ-Fe ₂ O ₃ 100 parts α-alumina 5 parts sulfonic acid metal-containing vinyl chloride resin 10 parts polyester polyurethane resin 5 parts carbon black 1 part myristylic acid 1 part stearic acid 1 part butyl stearate 1 part cyclohexanone 100 parts methyl ethyl ketone 100 parts
(7) Frequency of missing recording due to head contamination A television broadcast image was recorded on the videotape produced as described above, and the playback screen was visually observed and judged according to the following criteria. ◎ and ○ are good characteristics.
-No missing recording (white flickering on the screen) due to head contamination on the playback screen. : ◎
・ Occasionally flickering is observed, but I don't really care about it: ○
・ There are flickers in some places. △
-Frequent flickering is very anxious: ×
[0025]
(8) Cold crystallization temperature (Tcc)
A temperature rise curve was measured with a differential scanning calorimeter (for example, RDSC220 manufactured by Seiko Denshi Kogyo Co., Ltd.), and an exothermic peak temperature (Tcc) accompanying crystallization of the polymer was read.
[0026]
(9) Unevenness of thickness Using a film thickness tester KG601A manufactured by Anritsu Co., Ltd. and an electronic micrometer K306C, the thickness is continuously measured through a film sampled 30 mm wide and 1 m long in the vertical and horizontal directions. From the maximum thickness value Tmax (μm) and the minimum value Tmin (μm) at 1 m length,
R (μm) = Tmax−Tmin
And 1 mm long average thickness Tave (μm) to thickness unevenness (%) = R / Tave
As sought.
[0027]
【Example】
The present invention will be described based on examples.
Example 1 (Tables 1, 2, and 3)
Polyethylene-2,6-naphthalate (PEN) pellets obtained by a known method were pre-dried at 120 ° C. for 3 hours, then dried in a vacuum at 180 ° C. for 3.5 hours, and supplied to an extruder at 290 ° C. The film was melted at a temperature of 5 ° C., extruded from a die, and cooled and solidified on a casting drum having a surface temperature of 35 ° C. using an electrostatic application method to obtain an unstretched film in an amorphous state. This film was stretched under the conditions shown in Table 1. First, using a longitudinal stretching machine in which several rolls are arranged, two-stage stretching is performed longitudinally using the difference in peripheral speed of the rolls, followed by transverse stretching and heat treatment with a stenter, and further with a roll longitudinal stretching machine. After longitudinal stretching, re-stretching and heat treatment were performed with a stenter to obtain a 5.2 μm thick biaxially oriented polyethylene-2,6-naphthalate film. The amount of germanium in the film was 0.01% by weight as a polymer. Characteristics of the film a Young's modulus of the MD are shown in Table 2 is the Young's modulus of 1250 kg / mm ^2, TD is very high mechanical strength can be obtained that can not be obtained in a conventional sequential biaxial stretching was 1200 kg / mm ² When this film was used to produce a magnetic tape and the characteristics were evaluated, the electromagnetic conversion characteristic was very good with a high RF output of +3.0 dB and no omission of images.
[0028]
Examples 3 to 9, Reference Example, Comparative Examples 1 to 6 (Tables 1, 2, and 3)
The polymer to be used was changed (“PET” represents polyethylene terephthalate), and the stretching orientation was performed using the same extruder, die, and stretching apparatus as in Example 1. The stretching conditions were as shown in Table 1, and the properties of the obtained film were as shown in Tables 2 and 3. When the Young's modulus of either MD or TD is within the range of the present invention, it was possible to obtain a magnetic tape having high electromagnetic conversion characteristics (RF output) and very low image recording omission. On the other hand, when the Young's modulus is out of the range of the present invention, the electromagnetic conversion characteristics and the frequency of image recording omission cannot be satisfied.
[0029]
[Table 1]

[0030]
[Table 2]

[0031]
[Table 3]

[0032]
【The invention's effect】
In the present invention, any of the direction of the Young's modulus in the longitudinal or transverse direction 1000 kg / mm ² or more 1350 kg / mm ² or less, and the sum of the vertical and horizontal direction Young's modulus 1600 kg / mm ² or more 2700 kg / and mm ^{2 or} less, biaxial further the ratio of the thickness unevenness of the thickness irregularity and lateral (TD) vertical (MD) (MD / TD) is characterized in that 0.9 7 to 1.5 Since the oriented polyester film is used, a very high-strength film can be supplied. In particular, when used for magnetic tape, especially for digital data storage having a storage capacity of 20 GB or more, the quality can be improved even if the film is thinned. Therefore, it can be used particularly advantageously in magnetic recording medium applications, but can be widely used for various applications requiring mechanical strength such as capacitors and packaging in addition to magnetic recording medium applications.

Claims (5)

Longitudinal or either direction Young's modulus in the transverse direction is at 1000 kg / mm ² or more 1350 kg / mm ² or less, and the sum of the vertical and horizontal direction Young's modulus 1600 kg / mm ² or more 2700 kg / mm ² or less There, biaxially oriented polyethylene-2 addition ratio of the thickness unevenness of thickness irregularity and lateral (TD) vertical (MD) (MD / TD) is characterized in that 0.9 7 to 1.5 , 6-Naphthalate film. Vertical, horizontal any direction is also Young's modulus of 1000 kg / mm ² or more 1350 kg / mm ² or less, a biaxially oriented polyethylene-2,6-naphthalate film according to claim 1. The biaxially oriented polyethylene-2,6-naphthalate film according to claim 1 or 2, wherein the amount of germanium contained in the film is 0.005% by weight or more and 0.03% by weight or less of the polymer. The biaxially oriented polyethylene-2,6-naphthalate film for digital data storage having a storage capacity of 20 GB or more according to any one of claims 1 to 3 , wherein the film thickness is 2 µm or more and 7 µm or less. A longitudinally uniaxially stretched film having a birefringence of 0.20 or more and a density of 1.345 g / cc or more is transversely stretched at a temperature of (cold crystallization temperature Tcc−20 ° C.) to (Tcc + 20 ° C.) of the uniaxially stretched film, and then re- The method for producing a biaxially oriented polyethylene-2,6-naphthalate film according to any one of claims 1 to 4 , wherein the film is stretched in the transverse direction.