JPH036238A - Oriented polyester film - Google Patents

Abstract

PURPOSE:To prepare an improved oriented polyester film which has excellent travelling properties, is scuff-resistant, generates little powder when abraded, and is useful for a metallized film, a magnetic recording medium, etc., by compounding a specified amt. of a specific particulate gamma-Al2O3 into a polyester resin. CONSTITUTION:An oriented polyester film is prepd. from a polyester resin compounded with 0.01-2wt.% gamma-Al2O3 having a mean particle diameter of 0.5mum or lower. Generally a polyester film excellent in the physical and chemical properties is widely used as an industrial material. However, when the film travelling at a high speed touches, e.g. a high-hardness metal pin, friction and abrasion between them becomes large, scuff marks appear on the film and powder is generated by abrasion. The oriented polyester film contg. a specified amt. of said gamma-Al2O3 is excellent in the abrasion properties with other materials and can be suitably used for various applications including a base film for a metallized film and magnetic recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a polyester film having excellent abrasion resistance. More specifically, the present invention has excellent film running characteristics, and also produces extremely few scratches and abrasion particles.
This invention relates to an improved oriented polyester film suitable for metal deposition, magnetic recording media, etc.

[Prior Art and Problems to be Solved by the Invention] Polyester films have excellent physical and chemical properties and are widely used as substrates for graduations. In particular, at least uniaxially oriented polyethylene terephthalate film,
In particular, because of its excellent mechanical strength, dimensional stability, flatness, etc., it is used in various applications including base films for magnetic recording media and capacitor dielectrics.

Incidentally, when these films are actually handled, running properties and further abrasion resistance are required, but this has not been sufficiently achieved in the past.

For example, when a highly hard metal bottle and a film come into contact at high speed, the friction and abrasion between the two increases, causing scratches on the film and generation of abrasion powder.

As a result of intensive studies on improving this abrasion resistance, the present inventors have previously proposed a method of incorporating particles of high Mohs' hardness, such as aluminum oxide, into a film in Japanese Patent Application No. 138051/1982 and elsewhere. Proposed.

However, the inventors have also discovered that the incorporation of particles such as aluminum oxide can cause new problems. In other words, a film containing these particles certainly exhibits an extremely excellent effect in terms of preventing damage to the film itself and generation of abrasion powder when it comes into contact with metal pins, but When metals with low hardness are vapor-deposited or layered and rolled up concentrically, particles present on the film surface that comes into contact with the metal surface often damage the metal surface. A similar phenomenon is observed when a magnetic layer is provided instead of such a metal layer, and the surface of the magnetic layer is often scratched, deteriorating the electromagnetic characteristics.

[Means to solve the problem]

As a result of extensive research into improving this point, the inventor of the present invention found that if aluminum oxide particles with a specific crystal type are used in a specific amount, wear particles will be generated when contacting pins of any composition. The present inventors have discovered that it is possible to obtain an excellent oriented polyester film with almost no

That is, the gist of the present invention resides in an oriented polyester film characterized by containing 0.01 to 2% by weight of gamma-type aluminum oxide having an average particle size of 0.5 μm or less.

The present invention will be explained in more detail below.

The polyester referred to in the present invention refers to terephthalic acid, 2.6
- It refers to a polyester obtained using an aromatic dicarboxylic acid such as naphthalene dicarboxylic acid or its ester and ethylene glycol as the main starting materials, but it may contain other third components. In this case, the dicarboxylic acid component includes, for example, isophthalic acid, phthalic acid, 2.
6-naphthalene dicarboxylic acid, terephthalic acid, adipic acid, sebacic acid, and oxycarboxylic acid components such as p
-Oxyethoxybenzoic acid or the like can be used alone or in combination of two or more. As the glycol component, one or more of diethylene glycol, propylene glycol, butanediol, (1), 4-cyclohexane dimetatool, neopentyl glycol, etc. can be used. In any case, the polyester of the present invention refers to a polyester in which 80% or more of repeating structural units have ethylene terephthalate units or ethylene-2,6-naphthalene units.

Further, the polyester film of the present invention refers to an at least uniaxially oriented polyester film using such a polyester as a starting material, and any known method can be used for its production.

For example, it is usually melt-extruded into a sheet at 270 to 320°C, then cooled and solidified at 40 to 80°C to form an amorphous sheet, and then biaxially stretched or simultaneously stretched in the longitudinal and transverse directions,
A method such as heat treatment at 160 to 250° C. (for example, the method described in Japanese Patent Publication No. 30-5639) can be used. When stretching in the longitudinal and transverse directions, the stretching may be carried out in one stage, or in multiple stages as necessary, or a heat treatment section for orientation relaxation may be provided between the multi-stage stretching. Further, after biaxial stretching, the film may be stretched again before being subjected to the next heat treatment step. This re-stretching can be carried out in either the longitudinal or lateral directions, or in both directions.

The most important feature of the present invention is the use of aluminum oxide having a gamma (γ) type crystal morphology with an average particle size of 0.5 μm or less.

As is well known, aluminum oxide is usually obtained by thermally decomposing alumina hydrates such as gibbsite, vialite, and boehmite. There are nearly 10 types including type β, γ, O1δ, η, χ, η, etc.
Aluminum oxide with different crystal types is produced. Aluminum oxide can also be obtained by burning and hydrolyzing aluminum chloride in an oxyhydrogen flame, but in this case, aluminum oxide in various crystal forms such as α, T, and δ can be obtained depending on the processing conditions.

Each of these aluminum oxides has unique properties; for example, the α-type has a small specific surface area and rarely exhibits catalytic activity, whereas the T-type and η-type usually have a surface area of 150 to 300%.
It has a specific surface area of about yrr/g and has high catalytic activity. Also, depending on each crystal type, the density is about 2.5 ~
It can vary up to 4g/-, and the hardness also varies slightly.

As a result of careful study of many aluminum oxides having different properties, the inventors found that the γ-type aluminum oxide was suitable for the purpose of the present invention, and completed the present invention. In other words, a film containing gamma aluminum formate generates almost no abrasion powder when it comes into contact with metal pins or guide rolls, and when it is rolled up over a metal vapor-deposited layer, it is less likely to damage them and completely It can be suitably used throughout the process.

The reason why such excellent wear characteristics are exhibited in the case of gamma aluminum formate is not clear, but the main reasons are probably that the particles are compatible with polyester and have moderate hardness.

The average particle size of γ aluminum formate is 0.5 μm or less, preferably 0.1 μm or less. This crystalline form of aluminum oxide is, for example, ammonium, aluminum,
It can be obtained by thermally decomposing carbonate hydroxide, but it is convenient because it is often obtained with an average particle size of 0.1 μm or less. In the present invention, it is preferable to use aluminum oxide particles completely dispersed down to the primary particles, but it is acceptable for the aluminum oxide particles to behave as secondary particles in a small amount as long as it does not adversely affect the surface condition of the film. . However, in this case as well, the apparent average particle diameter is preferably 0.5 μm or less.

In the present invention, the desired effect can be fully exhibited if 70% by weight or more, preferably 90% by weight or more of the aluminum oxide added to the film is of the γ type.

The amount of gamma aluminum formate added to the polyester is selected from the range of 0.01 to 2% by weight. If this amount is less than 0.01% by weight, the effect of scratch resistance and abrasion resistance will be insufficient, while if it exceeds 2% by weight, it will often damage metal deposited layers or magnetic layers when they come into contact with them. .

As described above, in the present invention, by blending aluminum oxide having a specific crystal type, it has become possible to obtain a film with excellent abrasion characteristics that could not be achieved hitherto. However, if such aluminum oxide particles are used alone, the slipperiness of the film is insufficient and handling workability is poor, so it is preferable to use other particles in combination.

One example of such particles is so-called precipitated particles. These precipitated particles are fine particles of metal compounds precipitated during the polyester manufacturing process.
For example, an alkali metal or an alkali metal compound is present in the transesterification reaction or the esterification reaction, or before or after the reaction, and the particles are precipitated as inert fine particles having an average particle diameter of about 05 to 5 μm in the presence or absence of a phosphorus compound. In this case, running properties can be particularly improved by having the particles present in an amount of 0.01 to 1 weight percent based on the polyester film.

Another example is so-called additive particles. These additive particles refer to particles added externally to the polyester manufacturing process, and specifically include kaolin, talc, carbon, molybdenum sulfide, gypsum, rock salt, calcium carbonate, barium sulfate, lithium fluoride, calcium fluoride, and zeolite. , calcium phosphate, silicon dioxide, titanium dioxide, and the like. In this case, the average particle diameter of these additive particles is larger than that of gamma aluminum formate, and it is preferable to select from the range of 0.1 to 3 μm, and the amount added to the polyester is selected from the range of 0.05 to 2% by weight. .

Note that heat-resistant polymer fine powder can also be mentioned as an example of such additive particles. A typical example of this case is a monovinyl compound having only one aliphatic unsaturated bond in the molecule and a crosslinking agent as described in Japanese Patent Publication No. 59-5216. Examples include copolymers with compounds having at least 3 aliphatic unsaturated bonds, but are not limited to these, for example, thermosetting phenolic resins, thermosetting epoxy resins, thermosetting It is also possible to use fine powder of a fluororesin such as a polyurea resin, benzoguanamine resin, or polytetrafluoroethylene. In this case, the average particle diameter of these heat-resistant polymer fine powders is selected from the range of 0.05 to 5 μm, and the blending amount to the polyester film is selected from the range of 0.01 to 3% by weight.

As described above, in the present invention, in addition to a specific amount of γ-type aluminum oxide, other particles are also used as necessary. It is possible to achieve a higher degree of improvement in properties, mechanical strength, and slitting properties, making it more suitable as a base film for, for example, magnetic recording media.

One preferable physical property of the polyester film is that its refractive index in the thickness direction is 492 or more. If this value is less than 1.492, even if the particles of the present invention are used, slipperiness and abrasion resistance will often be insufficient. This value is preferably 1.494 or more and 1.505 or less. In order to obtain a film having such physical properties,
For example, in the case of sequential longitudinal and transverse biaxial stretching, the longitudinal stretching temperature may be set at about 105 to 1)5°C, which is 5 to 30°C higher than the normal stretching temperature. Alternatively, such a film can also be obtained by subjecting the film to significant lateral relaxation after two-wheel stretching and before heat treatment.

In addition, one of the preferable embodiments of the polyester film containing the specific aluminum oxide of the present invention is a biaxially oriented film that is strongly oriented in the longitudinal direction and has a film thickness of 12.0 μm or less. In other words, the film of the present invention can be particularly suitably used as a base film for magnetic recording media by taking advantage of its high abrasion resistance properties, but its features are especially exhibited when used for high strength, thin, and high recording density applications. be able to. Specifically, vertical F
-5 value is 12.0kg/year 12 or above, especially 14.0kg
/mm'' or more and the film thickness is 12.0 μm or less, especially 10.0 μm or less, which is effective in applications where wear resistance is particularly required.

Furthermore, in the present invention, the difference Δn (n, ゎn, o
) is 0.010 or more, it has particularly excellent slitting properties and is suitable as a base film for magnetic recording media. This slitting property is a characteristic when a tape coated with a magnetic layer is slit using a shear cutter, etc. If the degree of slitting is low, the cut end may curl up in a streaky manner, or hairs or powder may be generated from the cut end. When such a phenomenon occurs, white powder adheres to the tape, deteriorating electromagnetic conversion characteristics and inducing dropouts. By setting Δn to 0°010 or more, preferably 0.020 or more, more preferably 0.025 or more, this slitting property can be effectively improved. If this Δn is too large, problems will occur in terms of heat shrinkage rate, etc., so it is preferable that this Δn is 0.060 or less.

In order to obtain a film with such physical properties, for example, an amorphous unstretched polyester film is stretched 3 to 4 times in the longitudinal direction at around 90°C, and then stretched 3 to 5 times in the width direction at 90 to 150°C. A method of stretching the film by a factor of up to 6 times (usually at a higher magnification than in the longitudinal direction) and then heat-treating at 170 to 230° C. is conveniently employed.

Note that, in the present invention, it is of course possible to use a combination of several of these preferable characteristics in addition to the basic technical idea of using T-type aluminum oxide.

The film of the present invention is useful as a base film for videotapes, and can also be particularly effective when used as an audio film. In other words, in this field, conventional two-way radio cassette players, component stereos, etc.
As a result of the spread of models equipped with a dubbing function that is more than double the speed, the tape and the base material come into contact at higher speeds during the dubbing process and during fast forwarding and rewinding. The effects of this will be effectively demonstrated.

Further, when the film of the present invention is used as a substrate for thin metal deposition, the effect is maximized when the metal is aluminum, zinc, copper, silver, etc. and has a Mohs hardness of 2 to 3. The laminate obtained by subjecting the film of the present invention to metal vapor deposition is used for, for example, gold and silver systems, decorations, foils, labels, packaging, capacitors, electroluminescence, printed circuit boards, and the like.

[Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded. In addition, "parts" in Examples and Comparative Examples indicate "parts by weight."

Furthermore, the measurement method used in the present invention is as follows.

fl) Average particle size The particle size was measured using a microscope, and the volume fraction of the equivalent sphere was 50.
The particle size (diameter) at the % point was taken as the average particle size.

(2) Running property Evaluation was made based on the slipperiness of the film. The slipperiness was measured using the apparatus shown in FIG. In other words, the film is wrapped around a fixed hard chrome-plated metal roll (diameter 6 wa) with a corner of 135 mm.
'That is, contact at 2.356 rad(θ), 53
A load of g (Tz) was applied to one end, and it was run at a speed of l m / mm, the resistance force ('r +, g) at the other end was measured, and the coefficient of friction (μd) during running was determined using the following formula. .

(3) Abrasion resistance properties (A) Abrasion resistance properties with metal bottles The film was brought into contact with a metal bottle and rubbed, and the degree of scratches produced on the film surface was measured.

That is, the film was wrapped around a hard chrome-plated metal bottle (diameter 6 m, surface roughness 3S), and the angle was 135'' and the tension was 50.
g, and rubbing was carried out at a running speed of 4 m/sec.

Next, aluminum was vapor-deposited on the film surface, and the degree of scratches was visually judged, and the wear resistance against metal bottles was classified into the following five ranks.

Rank 1: There are many and often deep scratches.

Rank 2: The amount of scratches is relatively large and there are deep scratches in places.

Rank 3: The degree of damage is relatively small, with only a few deep scratches.

Rank 4: Some scratches are observed.

Rank 5 has almost no scratches.

(B) Wear resistance properties with magnetic layer 200 parts of magnetic fine powder, 30 parts of polyurethane resin, 10 parts of nitrocellulose, 1 part of vinyl chloride-vinyl acetate copolymer
After mixing and dispersing 0 parts of lecithin, 5 parts of lecithin, 100 parts of cyclohexanone, 100 parts of methyl isobutyl ketone and 300 parts of methyl ethyl ketone in a ball mill for 48 hours, 5 parts of a polyisocyanate compound was added to make a magnetic paint, and this was applied to a polyester film. Before the paint was sufficiently dried and solidified, it was magnetically oriented and then dried to form a magnetic layer with a thickness of 2 μm. Further, this coated film was subjected to surface treatment 1I using a super calender, and each portion was slit into a 2-inch width to prepare a videotape.

Next, the obtained magnetic tape was spread over 8000 lengths at a speed of 2.
It was wound up at 0 m/sec and with a tension of 100 g.

Next, the tape was rewound and the degree of scratches on the magnetic surface was visually judged and divided into the following five ranks.

Rank 1: There are many and often deep scratches.

Rank 2: The amount of scratches is relatively large and there are deep scratches in places.

Rank 3: The degree of damage is relatively small, with only a few deep scratches.

Rank 4: There are some scratches, but the level is satisfactory.

Rank 5 has almost no scratches.

(C) Abrasion resistance with vapor-deposited metal layer A film made by vacuum-depositing aluminum to a thickness of 250±IO on the surface of a 15μm polyester film with a width of 35n+
Cut a slit into the plate and attach it to the moving table with the aluminum vapor-coated side facing up. The ends of test films of the same width were fixed and overlapped on this aluminum vapor-deposited surface, and a load of 1 g/16 cl (1 g/16 cl) was applied on top of the test film, and the moving table was moved at a speed of 20 mm/min. 50-601) 1 Rub the vapor deposition surface and the test film together.

The total light transmittance before and after the test is measured using a haze meter NDH-20D manufactured by Nippon Juishoku Co., Ltd., and the difference therebetween is determined. The higher this value is, the more scratches there are on the aluminum surface.

Example 1 Dimethyl terephthalate) 100 parts ethylene glycol 7
0 parts and 0.20 parts of magnesium acetate tetrahydrate were placed in a reactor, and a transesterification reaction was carried out.

After 4 hours, 1 γ-type aluminum oxide with an average particle size of 0.02 μm was added to this system in which the transesterification reaction had substantially completed.
．． Added 0 parts and further added 0.0 parts of ethyl acid phosphate.
6 parts and 0.04 part of antimony dioxide were added, and a polymerization reaction was carried out for 5 hours according to a conventional method to obtain a polyester having an intrinsic viscosity of 0.63. (Polyester (A)) On the other hand, in the production of the above polyester, calcium carbonate with an average particle size of 0.8 μm is substituted for aluminum Mide.
Polymerization was carried out in the same manner except that 4 parts were added, and the intrinsic viscosity was 0.
63 polyethylene terephthalate was obtained. (Polyester (B)) Next, polyester (A) and polyester (B) were
:50 weight ratio, dried and extruded into a sheet form from an extruder at 290°C to obtain an amorphous sheet. Then, the obtained sheet was heated 3.5 times in the longitudinal direction at 90°C and 1) 0 in the transverse direction.
The film was stretched 3 times at 4°C and heat treated at 210°C for 3 seconds to obtain a biaxially stretched film with a thickness of 15 μm.

Next, the resulting film was coated with a magnetic layer or vapor-deposited with aluminum.

These evaluation results are shown in Table 1 together with those of other Examples and Comparative Examples.

Example 2 A polyester and a polyester film were obtained and evaluated in the same manner as in Example 1 except that the average particle size of γ-type aluminum oxide and the amount added to the polyester were changed.

Comparative Example 1 A film was obtained in the same manner as in Example 1 except that γ-A1203 was not contained.

Comparative Example 2 A film was obtained in the same manner as in Example 1, except that α-type aluminum oxide with an average particle size of 0.3 μm was used instead of γ-type aluminum oxide with an average particle size of 0.02 μm in Example 1, and its characteristics were was evaluated.

〔Effect of the invention〕

The film of the present invention has excellent abrasion characteristics with various materials, and can be suitably used for various applications including metal deposition and base films for magnetic recording media, and has high industrial value.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a running system for evaluating film running properties. In the figure, (1) is a fixed stainless steel bottle with a diameter of 6 mm, (]) and (Iff) are tension meters, and θ is 135°. Applicant: Diafoil Co., Ltd. Agent: Patent attorney: Yo Hase - 1 other person

Claims (1)

[Claims] (1) An oriented polyester film containing 0.01 to 2% by weight of gamma-type aluminum oxide having an average particle size of 0.5 μm or less.