JPH06200064A - Polyester film - Google Patents

Abstract

(57) [Summary] [Object] To provide a polyester film having excellent scratch resistance and abrasion resistance, which is useful as a base film of a magnetic recording medium. [Constitution] On at least one side of the polyester film,
A coating layer provided in the film forming process of the polyester film, wherein the coating layer has a γ type having an average particle diameter of 0.5 μm or less,
It contains 0.1 to 50% by weight of one or more selected from δ type and θ type aluminum oxide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a magnetic recording medium,
The present invention relates to a polyester film having excellent running properties, electromagnetic conversion characteristics, and abrasion resistance. More specifically, the present invention relates to a base film suitable for high-density magnetic recording in which the occurrence of sliding scratches and abrasion powder during tape running is extremely small and the occurrence of dropout is suppressed.

[0002]

2. Description of the Related Art Polyester films are widely used as industrial substrates because of their excellent physical and chemical properties. Among them, the biaxially oriented polyethylene terephthalate film is now indispensable as a base film for a magnetic recording medium because it is particularly excellent in mechanical strength, dimensional stability and flatness. In recent years, improvements in magnetic recording media have been made rapidly, and along with this, the demand for base films has become even more stringent. For example, in the case of high-density recording such as a video tape, the magnetic layer is thinned. In this case, the unevenness of the base film itself is reflected on the surface of the magnetic layer, and when the degree is large, electromagnetic conversion is performed. It causes deterioration of characteristics and frequent dropouts. Therefore, it is desired that the surface of the base film is flatter, but as is well known, when the surface of the film becomes flat, not only the running property of the film deteriorates, but also between the film and the base material such as the guide pin. Friction between,
Abrasion increases, and scratches and abrasion powder are generated on the film.

If the abrasion resistance of the polyester film is insufficient as described above, abrasion powder is generated between the film and various rolls or guide pins after the magnetic layer manufacturing process or product, and also the electromagnetic conversion characteristics. And will be inferior in terms of dropout. If the film has insufficient scratch resistance, the film is likely to be scratched before and after coating with the magnetic layer, which is reflected on the surface of the magnetic layer, resulting in poor electromagnetic properties. Further, the presence of the scraped white powdery substance often deteriorates the electromagnetic characteristics.

As a means for improving surface properties such as running property and abrasion resistance of a polyester film, a method in which inert fine particles are present in a conventional film to appropriately roughen the film surface, specifically, so-called precipitation The particle method and the additive particle method are known. Precipitated particle method is a method for precipitating catalyst residues etc. in the polyester as fine particles in polyester in the polyester manufacturing process, and has the advantage that the operation is simple, the polymer can be manufactured at low cost, and the filter life during manufacturing is long. Have. Furthermore, it has an excellent affinity with polyester, less particles fall off from the film, and relatively excellent abrasion resistance. However, since the main component of the deposited particles is an organic component, scratch resistance is poor.

On the other hand, the addition particle method is a method in which fine particles of calcium carbonate, kaolin, silica, titanium oxide and the like are added and contained during polyester production or molding.
This method generally tends to lack the affinity between particles and polyester, but it is known to be effective in improving scratch resistance. As described in JP-A-1-306220, it is known that scratch resistance and abrasion resistance can be remarkably improved by using a specific amount of particles having high hardness. However, although it is possible to improve various properties required when a magnetic tape is used, by using particles having high hardness alone or in combination with other particles,
At the same time, there are disadvantages in terms of cost and manufacturing. That is,
In the method of blending high hardness particles in a polyester film, expensive particles usually obtained by a special manufacturing method must be filled in all layers of the film, and the particles are dispersed even in the production of polyester containing such particles. To be good, a large amount of low concentration ethylene glycol slurry must be added.
Also, when the high hardness particles are filled over the entire film layer, the wear of the slit blade during film slitting is remarkable, etc.
There are inconveniences in terms of equipment, operation, and manufacturing cost.

[0006]

Means for Solving the Problems As a result of intensive investigations by the present inventors in view of the above problems, a film containing specific particles in a coating layer was excellent in scratch resistance and abrasion resistance as well as in slit property. It was found that the effect can be exhibited, and the present invention has been completed. That is, the gist of the present invention is to have a coating layer provided on the polyester film at least on one side in the film forming process of the polyester film, and the coating layer has a mean particle size of 0.5 μm or less, γ type, δ type. Type and θ type aluminum oxide selected from 0.1 to 0.1
The polyester film is characterized by containing 50% by weight.

Hereinafter, the present invention will be described in more detail. The polyester in the present invention means terephthalic acid and 2.6.
An aromatic dicarboxylic acid such as naphthalenedicarboxylic acid or its ester, and a polyester obtained by using ethylene glycol as a main starting material, but may contain other third component. In this case, examples of the dicarboxylic acid component include isophthalic acid, terephthalic acid,
2.6-naphthalenedicarboxylic acid, adipic acid, sebacic acid and the like can be used. As the glycol component, diethylene glycol, propylene glycol, butanediol, 1.4-cyclohexanedimethanol, neopentyl glycol and the like can be used. In any case, the polyester referred to in the present invention refers to a polyester in which 80% or more of repeating structural units have ethylene terephthalate units or ethylene-2.6-naphthalate units.

Further, the polyester film of the present invention refers to a polyester film using such polyester as a starting material, and a known method can be adopted as a manufacturing method thereof. For example, after melt-extruding into a sheet form at 270 to 320 ° C., cooling and solidifying at 40 to 80 ° C. to form an amorphous sheet, the area ratio becomes 4 to 20 times in the vertical and horizontal directions at 80 to 150 ° C. As described above, a method of performing sequential biaxial stretching or simultaneous biaxial stretching and heat treatment at 160 to 250 ° C. (for example, the method described in JP-B-30-5639) can be used. Stretching in the machine direction and the transverse direction may be carried out in one step each, or if necessary, in multiple steps,
A heat treatment section for relaxing orientation may be provided during the multi-stage stretching. Further, after biaxial stretching, it may be stretched again before being subjected to the heat treatment step of the next step. This re-stretching
It can be performed either vertically or horizontally.

The greatest feature of the present invention is that in the coating layer provided on the polyester film, gamma (γ) type, delta (δ) type and theta (θ) particles having an average particle size of 0.5 μmm or less are used.
The purpose is to use one or more aluminum oxides selected from the type aluminum oxides. As is well known, aluminum oxide is usually obtained by thermally decomposing alumina hydrates such as dibsite, vialite, and boehmite, but at this time, depending on the type of raw material, hydrolysis conditions, particularly temperature conditions, α Type, β, γ, κ, ο,
Aluminum oxide having nearly 10 different crystal types such as δ, η, χ, and ρ type is generated. Aluminum oxide can also be obtained by a method of burning and hydrolyzing aluminum chloride in an oxyhydrogen flame. In this case, various crystalline aluminum oxides such as α, γ and δ can be obtained depending on the treatment conditions. Each of these aluminum oxides has unique properties, for example, α type has a small specific surface area,
While almost no catalytic activity is exhibited, the γ-type and η-type usually have a specific surface area of about 150 to 300 m ² / g and have a high catalytic activity. Further, the density can be changed up to about 2.5 to 4 g / cm ² depending on each crystal type, and the hardness is delicately changed.

The present inventors have made detailed studies on many aluminum oxides having different properties, and as a result,
Aluminum oxide selected from γ type, δ type and θ type,
In particular, it was found that the δ type meets the purpose of the present invention,
The present invention has been completed. That is, the coating layer containing such an aluminum oxide hardly generates abrasion powder when contacted with either a metal pin or a plastic guide roll or pin, and is extremely excellent in abrasion resistance and abrasion resistance. There is. Further, the film having such an aluminum oxide only in the coating layer has a significantly reduced abrasion rate of the slit blade during slitting, as compared with the film compounded in the film. The reason why the wear rate of the slit blade is reduced is that the concentration of such aluminum oxide is probably concentrated only on the surface layer portion of the film so that the amount of particles used in the entire film is less than that of the conventional film. It is considered that this is because it could be significantly reduced to about 05 to 0.2 times.

Although it is not clear why these aluminum oxides exhibit such an effect, particularly excellent wear resistance, it is probably that the particles are well compatible with the organic binder and that the hardness is appropriate. Seems to be the main reason. The average particle size of such aluminum oxide is preferably 0.5 μm or less, and particularly preferably 0.1 μm or less. Among these aluminum oxides, particularly preferable δ-type crystal type aluminum oxide can be generally obtained by highly flame-hydrolyzing aluminum chloride, but the average particle size thereof can be obtained as 0.1 μmm or less. It is convenient because there are many. In the present invention, it is preferable to use such aluminum oxide particles dispersed in primary particles, but the aluminum oxide particles may behave as slightly agglomerated secondary particles as long as they do not adversely affect the surface condition of the film. However, in this case as well, an apparent average particle size of 0.5 μmm or less is preferably used. In the present invention, if 70% by weight or more, preferably 90% by weight or more of the aluminum oxide compounded in the coating layer is γ type, δ type or θ type, the desired effect can be sufficiently exhibited.

In the present invention, these particles are mainly used as one component of the aqueous coating agent, but in this case, it is necessary to disperse them in water in advance. At this time, it is desirable to use a dispersant from the viewpoint of increasing the compounding stability with the aqueous resin. Further, if necessary, it is blended with the aqueous resin through operations such as pulverization, classification and filtration.

In the present invention, the coating solution containing the aluminum oxide and the aqueous resin is applied to at least one side of the film in the process for producing the polyester film.
The amount of such aluminum oxide compounded is in the range of 0.1 to 50% by weight in terms of the solid content of the coating, and preferably 1 to 10
It is selected from the range of% by weight. If the content is less than 0.1% by weight, the scratch resistance will not be improved, and if it exceeds 50% by weight, the mechanical strength of the coating layer will be deteriorated. As described above, in the present invention, by applying aluminum oxide having a specific crystal form, it becomes possible to impart excellent wear characteristics and slit properties. However, such aluminum oxide alone may be insufficient in slipperiness of the film and inferior in handling workability, and in that case, it can be solved by using other particles in combination.

Specific examples of such particles include kaolin, talc, carbon, molybdenum sulfide, gypsum, rock salt,
Examples thereof include calcium carbonate, barium sulfate, lithium fluoride, calcium fluoride, zeolite, calcium phosphate, silicon dioxide, titanium dioxide and heat-resistant polymer fine powder. The average particle size of these particles is 0.05 to 3
It is preferable to select from the range of μmm, and the blending amount relative to the coating solid content is from 0.5 to 40% by weight.

The binder for the coating layer of the present invention is usually a binder.
A water-based resin is used, but the water-based resin referred to here means the manufacturing process of the magnetic recording material after being coated on the surface of the polyester film, and the use environment under high temperature and high humidity after being processed into the magnetic recording material. When it is coated with an overcoat layer such as a magnetic layer or a back coat layer having heat resistance and moisture resistance that can withstand, and this layer is an undercoat layer, it is a resin having excellent adhesiveness with the layer, such as polyester. , Polyamide, polystyrene, polyacrylate, polycarbonate, polyarylate, polyvinyl chloride, polyvinylidene chloride, polyvinyl butyral, polyvinyl alcohol, polyurethane, and other resins, and copolymers and mixtures of these resins. However, the invention is not limited to these. The most preferable resin among these is a polyester resin.

Examples of the components constituting the polyester resin include the following polyvalent carboxylic acids and polyhydric hydroxy compounds. That is, as the polycarboxylic acid,
Terephthalic acid, isophthalic acid, orthophthalic acid, phthalic acid, 4,4'-diphenyldicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2-potassium sulfoterephthalate Acid, 5-sodium sulfoisophthalic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, glutaric acid, succinic acid, trimellitic acid, trimesic acid, trimellitic anhydride, phthalic anhydride, p-hydroxybenzoic acid , Trimellitic acid monopotassium salt and ester-forming derivatives thereof can be used, and as the polyvalent hydroxy compound, ethylene glycol, 1,2-propylene glycol, 1,3
-Propylene glycol, 1,3-propanediol,
1,4-butanediol, 1,6-hexanediol,
2-methyl-1,5-pentanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, p
-Xylylene glycol, bisphenol A-ethylene glycol adduct, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, polytetramethylene oxide glycol, Dimethylolpropionic acid, glycerin, trimethylolpropane, sodium dimethylolethyl sulfonate, potassium dimethylolpropionate, etc. can be used.

Usually, one or more of these compounds are appropriately selected and a polyester resin is synthesized by a conventional polycondensation reaction. In addition to the above, JP-A-1
A composite polymer having a polyester component such as a so-called acrylic graft polyester described in JP-A-165633 or a polyester polyurethane in which a polyester polyol is chain-extended with isocyanate can also be preferably used as the polyester resin used in the present invention.

The aqueous resin in the present invention usually contains 70% water.
The liquid containing a weight% or more as a medium, may be a coating agent forcibly dispersed by a surfactant or the like, but preferably a hydrophilic nonionic component such as polyethers,
It is a self-dispersion type coating agent having a cationic group such as a quaternary ammonium salt, and more preferably a water-soluble or water-dispersible resin coating agent having an anionic group. The resin having an anionic group is a resin having a compound having an anionic group bonded to the resin by copolymerization or grafting, and sulfonic acid, carboxylic acid, phosphoric acid and their lithium salts, sodium salts, potassium salts. , Ammonium salt and the like. The ratio of the anionic group to the coating solid content is preferably 0.05 to 8% by weight. When the amount of the anionic group is less than 0.05% by weight, the water solubility or water dispersibility of the resin tends to be poor, and when the amount of the anionic group exceeds 8% by weight, the water resistance and the hygroscopicity of the coating layer are poor. May cause problems.

The coating solution for obtaining the coating layer in the present invention contains a methylol as a crosslinking agent in order to improve the adhesion (blocking property), water resistance, solvent resistance and mechanical strength of the coating layer. Alternatively, alkylated urea-based compounds, melamine-based compounds, guanamine-based compounds, acrylamide-based compounds, polyamide-based compounds, epoxy compounds, aziridine compounds, block polyisocyanates, silane coupling agents, titanium coupling agents, zirco-alumines. -Ato coupling agent, peroxide, heat or photoreactive vinyl compound, photosensitive resin, etc. may be contained. Further, if necessary, it may contain an antifoaming agent, a coating property improving agent, a thickening agent, an antistatic agent, an antioxidant, an ultraviolet absorber, a foaming agent, a dye, a pigment, etc., and blend them. The effect of the present invention is sufficiently exerted even in such a system.

The film of the present invention is particularly useful as a base film for video tapes and also when used as an audio film. In other words, recently, models that have more than double the high-speed dubbing function, such as double radio-cassette and compo stereo, have become popular. As a result, the tape and base material can be processed at higher speed during the dubbing process, fast-forwarding and rewinding. However, in this case, the effect of the present invention is effectively exhibited.

[0021]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to the following examples as long as the gist thereof is not exceeded. The measuring methods and definitions of various physical properties and characteristics in the present invention are as follows. In addition, in Examples and Comparative Examples, "part"
"Parts by weight" means "parts by weight". (1) Average particle diameter The particle diameters of the primary particles and aggregates in the coating layer were determined by observing the cross section of the coating layer with a transmission electron microscope. The average particle diameter was defined as the diameter of the equivalent sphere-converted value with a cumulative volume fraction of 50%. Regarding the particles in the dry powder and the slurry, the particle size was determined using a scanning electron microscope. (2) Center line average roughness (Ra) It was performed according to the method described in JIS B0601-1976. For the measurement, a surface roughness meter (SE-3 manufactured by Kosaka Laboratory Ltd.)
F) was used. The center line average roughness was determined under the conditions of a stylus diameter of 2 μm, a stylus load of 30 mg, a cutoff value of 0.08 mm, and a measurement length of 0.8 mm. Do this at 12 measurement points, cut the maximum and minimum values respectively, and
The average value of the points was calculated and set as Ra.

(3) Travelability Two films cut into a width of 15 mm and a length of 150 mm are stacked on a smooth glass plate, a rubber plate is placed on the two films, and the contact pressure of the two films is 2 g / cm ^2. As 20m
Measure the frictional force by sliding the films at m / min,
The coefficient of friction at the point of sliding by 5 mm was determined as the coefficient of dynamic friction. The measurement was performed at a temperature of 23 ° C ± 1 ° C and humidity of 50% ± 5
% Under an atmosphere. (4) Abrasion characteristics 10 while contacting the film with the hard chrome fixed pin.
After running for 00 m, the abrasion white powder adhering to the fixed pin made of hard chrome was visually observed and evaluated according to the following three grades of A, B and C. The film speed was 13 m / min,
The tension was about 200 g, and the winding angle of the film around the pin was 135 °. A: No white powder generation B: Small white powder generation C: Large white powder generation

(5) Scratch resistance A polyester film is fixed to a hard chromium fixing pin (diameter 6).
mm, surface roughness 3S), wrap angle 135 degrees, tension 20
They were brought into contact with each other at 0 g and run for 100 m at a speed of 13 m / min. Next, aluminum was vapor-deposited on the contact surface of the polyester film with the fixing pin, and the degree of scratches was visually evaluated and classified into the following ranks. A: Almost no scratches B: Slight scratches are recognized, but satisfactory level C: Scratch amount is relatively small, deep scratches are slight D: Scratch amount is comparable There are many deep and deep scratches E ... There are many scratches and often deep scratches

(6) Electromagnetic characteristics First, 200 parts of magnetic fine powder, 30 parts of polyurethane resin,
10 parts of nitrocellulose, 10 parts of vinyl chloride / acetate copolymer, 5 parts of lecithin, 100 parts of cyclohexanone and 300 parts of methyl ethyl ketone are mixed and dispersed in a ball mill for 48 hours, and then 5 parts of a polyisocyanate compound is added to obtain a magnetic paint, which is a polyester. After coating the non-coated surface of the film so that the film thickness after drying was 5 μm, the coating was magnetically oriented before the coating was sufficiently dried and solidified, and then dried. further,
The coated film was surface-treated with a super calendar and slit into a 1/2 inch width to obtain a video tape. This video tape is NV-370 manufactured by Matsushita Electric Co., Ltd.
The following magnetic tape characteristics were evaluated at a constant speed using a 0 type video deck. VTR Head Output (S / N) The VTR head output at a measurement frequency of 4 MHz was measured with a synchroscope, the reference tape was 0.0 decibel (dB), and the relative value (dB) was measured. Dropout (DO) Number 4 or 4 megahertz signal recorded video tape was played back, Okura Industry Co., Ltd. dropout counter measured the number of dropouts for about 20 minutes, and converted to the number of dropouts per minute .

Example 1 100 parts of dimethyl terephthalate, 60 parts of ethylene glycol and 0.09 part of magnesium acetate tetrahydrate were heated and heated, and methanol was distilled off to carry out a transesterification reaction, which required 4 hours from the start of the reaction. Then, the temperature was raised to 230 ° C. to substantially end the transesterification reaction. Then add 0.04 parts of ethyl acid phosphate,
Furthermore, 0.04 parts of antimony trioxide was added to carry out a polycondensation reaction, and after 4 hours and 30 minutes, polyethylene terephthalate having an intrinsic viscosity of 0.660 was obtained. The obtained polyester is dried, melt-extruded at 290 ° C. to form an amorphous sheet, and then stretched 3.5 times at 90 ° C. in the longitudinal direction, and then 0.1 times the amount of the δ-type aluminum oxide particle-containing paint having the following composition. The non-ionic dispersant is added and the paint obtained by dispersing with a sand grinder is dried and stretched by a bar coating method, and the coating thickness is 0.1 μm.
m to m, then laterally at 110 ° C for 3.
Stretched 7 times and heat-treated at 210 ° C for 3 seconds to give a thickness of 15
A film of μm was obtained. Aluminum oxide particle-containing paint δ-type aluminum oxide (average particle size 0.03 μm) 3 parts by weight; polyester resin (Plus Coat Z-4 manufactured by Kyodo Chemical
61) 97 parts by weight; water 900 parts by weight

Example 2 A biaxially stretched polyethylene terephthalate film was obtained in the same manner as in Example 1 except that the paint containing aluminum oxide particles was changed to the one shown below. Aluminum oxide particle-containing coating δ type aluminum oxide (average particle size 0.03 μm) 10 parts by weight; polyester resin (Plus Coat Z-manufactured by Kyosho Chemical Co., Ltd.)
461) 90 parts by weight; water 900 parts by weight

Example 3 A biaxially stretched polyethylene terephthalate film was obtained in the same manner as in Example 1 except that the paint containing aluminum oxide particles was changed to the one shown below. Aluminum oxide particle-containing paint 10 parts by weight of δ-type aluminum oxide (average particle size 0.1 μm); polyester resin (Plus Coat Z-4, manufactured by Kyosho Chemical Co., Ltd.)
61) 90 parts by weight; 900 parts by weight of water

Example 4 A biaxially stretched polyethylene terephthalate film was obtained in the same manner as in Example 1 except that the coating material containing aluminum oxide particles was changed to the one shown below. Aluminum oxide particle-containing paint γ-type aluminum oxide (average particle size 0.05 μm) 10 parts by weight;
461) 90 parts by weight; water 900 parts by weight

Example 5 A biaxially stretched polyethylene terephthalate film was obtained in the same manner as in Example 1 except that the coating material containing aluminum oxide particles was changed to the one shown below. Paint containing aluminum oxide particles 10 parts by weight of θ-type aluminum oxide (average particle diameter 0.08 μm); polyester resin (Plus Coat Z-manufactured by Kyouso Kagaku)
461) 90 parts by weight; water 900 parts by weight

Comparative Example 1 A biaxially stretched polyethylene terephthalate film was obtained in the same manner as in Example 1 except that the coating material containing aluminum oxide particles in Example 1 was changed to the one shown below. Aluminum oxide particle-containing paint 10 parts by weight of α-type aluminum oxide (average particle size 0.3 μm); polyester resin (Plus Coat Z-4 manufactured by Kyosho Chemical Co., Ltd.)
61) 90 parts by weight; 900 parts by weight of water

Comparative Example 2 A biaxially stretched polyethylene terephthalate film was obtained in the same manner as in Example 1 except that the coating material containing aluminum oxide particles was changed to the one shown below. Paint containing aluminum oxide particles δ type aluminum oxide (heat decomposition method average particle size 0.03
μm) 60 parts by weight; polyester resin (Plus Coat Z-461 manufactured by Kyosho Chemical Co., Ltd.) 40 parts by weight; water 900 parts by weight The results obtained above are summarized in Tables 1 and 2 below.

[0032]

[Table 1]

[0033]

[Table 2]

The films of Examples 1 to 5 satisfying the requirements of the present invention are excellent in running resistance and abrasion resistance, and particularly excellent in scratch resistance, so that the electromagnetic characteristics are at a highly satisfactory level. On the other hand, Comparative Example 1 uses α-type aluminum oxide, but is inferior to the aluminum oxide of the present invention in scratch resistance, slit property, and electromagnetic characteristics when used as a magnetic tape. Comparative Example 2 is an example in which the compounding amount of aluminum oxide exceeds the requirements of the present invention even if the crystal form is within the range of the present invention, but the abrasion resistance due to deterioration of the mechanical strength of the coating layer. Is reduced.

[0035]

The film of the present invention has excellent abrasion resistance,
It has scratch resistance and slit resistance, and its industrial value is high.

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Claims (1)

[Claims] 1. A γ-type, δ-type, and θ-type polyester film having a coating layer provided on at least one surface thereof in a film-forming process of the polyester film, and the coating layer having an average particle size of 0.5 μm or less. A polyester film comprising 0.1 to 50% by weight of one or more selected from the type aluminum oxides.