JPH06279608A - Abrasion-resistant polyester film - Google Patents

Abstract

PURPOSE:To provide a base film extremely reduced in the getting scratches and production of abrasion powder on the travel of the film tape, preventing the happening of dropout, and suitable for high density magnetic recording tapes. CONSTITUTION:A polyester film is characterized in that the film has a coating layer formed in its production process on at least one surface of the polyester film and that the coating layer contains 0.1-50wt.% of aluminum trioxide particles having an average particle diameter of at least <=1mum, 0.1-50wt.% of an aqueous high mol.wt. epoxy resin, and 30-98wt.% of an aqueous polyester resin.

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 that provides excellent running properties, electromagnetic conversion properties, and scratch resistance. More specifically, the present invention relates to a base film having a coating layer suitable for high-density magnetic recording, in which scratches and abrasion powder are extremely small during tape running and dropout is suppressed.

[0002]

2. Description of the Related Art In recent years, magnetic recording media have been rapidly improved, and along with this, the demands on polyester films used as base films have become more severe. . 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 if the surface of the film becomes flat, not only the running property of the film deteriorates, but also the friction and wear between the film and the base material, for example, the guide pin are large. As a result, scratches and abrasion powder are generated on the film.

If the abrasion resistance of the polyester film is insufficient, abrasion powder is generated between the film and various rolls or guide pins during use after the magnetic recording medium is manufactured or used as a product. It becomes inferior in terms of electromagnetic conversion characteristics and dropout. If the scratch resistance of the film is insufficient, the film is easily scratched before and after coating with the magnetic layer, which is reflected on the surface of the magnetic layer, resulting in poor electromagnetic characteristics. Further, the presence of the scraped white powdery substance often deteriorates the electromagnetic characteristics. As a means for improving the surface properties such as running property and scratch resistance of a polyester film, there is known a method in which inert fine particles are present in the film to appropriately roughen the film surface. In particular, JP-A 1-3
As described in JP-A-06220, it is known that scratch resistance and abrasion resistance can be remarkably improved by using a specific amount of particles having high hardness.

[0004] However, while using such particles having a high hardness alone or in combination with other particles can improve various properties required especially in the case of a magnetic tape, at the same time, there are disadvantages in terms of cost and production. is there. 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 also in the production of polyester containing the particles, In order to obtain good dispersion, it is necessary to add a large amount of low-concentration ethylene glycol slurry. Further, if the high hardness particles are filled in the entire layer of the film, the slit blade is significantly worn when the film is slit, which is disadvantageous in terms of the apparatus, operation, and manufacturing cost.

[0005]

Means for Solving the Problems As a result of intensive studies made by the present inventors in view of the above problems, as a result, a coating liquid containing aluminum oxide particles, a high molecular weight epoxy resin and a polyester resin is produced in the production process of a polyester film. It was found that the film obtained by applying the composition has excellent running properties, scratch resistance, slit properties, and high-temperature tack resistance that seriously affects the productivity of magnetic recording media, thus completing the present invention. Came to.

That is, an object of the present invention is to provide an aluminum oxide film having 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 having at least an average particle diameter of 1 μm or less. 0.1-50 wt% particles, 0.1-50 wt% aqueous high molecular weight epoxy resin and 30 wt% aqueous polyester resin
It exists in the polyester film characterized by containing -98 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, etc. 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 coating layer of the film of the present invention is applied to at least one side of the polyester film before the stretching and heat treatment are completed in the production process of the polyester film, followed by drying, stretching, heat setting and treatment of the polyester film. Formed under conditions. By the coating layer formed by the above method satisfies the specific configuration,
It has remarkable scratch resistance and abrasion resistance, and exhibits a remarkable effect of not exhibiting adhesion with a contact substance under high-temperature and high-pressure treatment conditions such as a calender treatment step. The aluminum oxide particles used in the present invention are, for example, those having an average particle diameter of usually 1 μm or less of primary particles produced by the flame method hydrolysis of anhydrous aluminum chloride or the hydrolysis of aluminum alkoxide, and preferably 0 μm or less. ．
The particles are 2 to 0.005 μm. In the present invention, the alumina particles are preferably used after being completely dispersed up to the primary particles, but as long as they do not adversely affect the surface condition of the film, they may aggregate to some extent and behave as secondary particles. Also, a part of aluminum oxide, for example, 30%
It is possible to replace less than the weight with oxides such as Si, Ti, Fe, Na and K.

The particle size distribution of the aluminum oxide particles used in the present invention is sharper. Specifically, when the particle sizes are integrated from the smaller particle size, the ratio of the particle size of 75% by weight to the particle size of 25% is 2. It is preferably 0 or less, more preferably 1.5 or less. As for the shape of these particles, those having a shape close to a lump or a sphere are usually preferably used. Specifically, for example, the volumetric shape defined in Japanese Patent Publication No. 53-14583 is 0.1 to π / 6, and further 0.2 to π /.
Particles such as 6 are preferred. The specific surface area of the particles used is, for example, an average particle size of 0.5 μm and a density of 2 g / c.
particles of sphericity of m ² has a specific surface area of about 6 m ² / g, can be preferably used to 500 meters ² / g approximately porous ones. The surface of these particles may be modified with various surface treatment agents for the purpose of improving the affinity with water-based paints.

In the present invention, the above particles are used as one component of the coating agent, but in this case, they are dispersed in water in advance. At this time, it is desirable to use a small amount of a dispersant in order to improve 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. For example, aluminum oxide particles and water can be dispersed and adjusted using a high-speed stirrer having a plurality of shearing blades parallel to the rotating direction of the stirring blade, a homomixer, an ultrasonic disperser, or the like. Further, the dispersed slurry is preferably filtered with a cartridge type filter having 3 μm perforations for the purpose of removing coarse particles and undispersed aggregated particles in the slurry.

The aluminum oxide used in the present invention is blended in an aqueous polyester resin which is a main binder and coated on a polyester film. The blending amount is 0.1 to 50% by weight based on the coating layer. It is preferably 0.5 to 20% by weight. If the blending amount of aluminum oxide is less than 0.1% by weight, the density of aluminum oxide particles on the film surface becomes low, and the scratch resistance cannot be sufficiently improved. If the blending amount of aluminum oxide exceeds 50% by weight, the mechanical strength of the coating layer will be poor. Examples of the aqueous high molecular weight epoxy resin used in the present invention include a resin having two or more epoxy groups in the molecule such as a condensation reaction product of bisphenol A and epichlorohydrin, an epoxy novolac resin, and a polyamine such as diethylenetriamine and phthalic anhydride. Acid anhydride, if necessary, further reacting a third component to obtain a high molecular weight epoxy resin, and further introducing a hydrophilic group such as a carboxyl group or a sulfonic acid group into the molecule, and emulsifying and dispersing in water to obtain a high molecular weight It is an epoxy emulsion.

When an emulsifying agent which is generally used is used in the emulsification and dispersion of such an emulsion, the heat resistance and the moisture resistance of the coating layer are markedly impaired. Therefore, a high molecular weight epoxy emulsion which does not use an emulsifying agent is preferable. The minimum film forming temperature MFT of such an emulsion is preferably 90 ° C. or lower. If the MFT exceeds 90 ° C., the roughness of the coating layer surface will remarkably increase, and the film will not be suitable for high density magnetic recording applications.

The content of the aqueous high molecular weight epoxy resin is 0.1 to 50% by weight, preferably 1 to 30% by weight based on the coating layer. If the blending amount of the resin is less than 0.1% by weight, the effect of improving the heat resistance of the coating layer will not be sufficiently exhibited. Also, 5
When it exceeds 0% by weight, the surface roughness of the coating layer is deteriorated.

The aqueous polyester resin used in the coating layer of the present invention has a property as a binder for uniformly dispersing aluminum oxide particles and further firmly fixing the particles on a polyester film. A water-dispersible or water-soluble polyester resin having mechanical strength, heat resistance, humidity resistance, and solvent resistance that can withstand a use environment under high temperature and high humidity after being processed into a magnetic recording material.

Examples of the component that constitutes the polyester resin include the following polyvalent carboxylic acids and polyvalent 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 sulfoterephthalic acid, 5-sodiumsulfoisophthalic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, glutar Acid, succinic acid, trimellitic acid, trimesic acid, trimellitic anhydride, phthalic anhydride, p-hydroxybenzoic acid, trimellitic acid monopotassium salt and their ester-forming derivatives can be used, and polyhydric hydroxy groups can be used. As the 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.

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-1-1
The polyester-based resin of the present invention also includes a composite polymer having a polyester component such as so-called acrylic graft polyester and polyester polyurethane in which polyester polyol is chain-extended with isocyanate described in Japanese Patent No. 65633. The blending amount of the polyester resin is in the range of 30 to 98% by weight with respect to the coating layer. When the blending amount is less than 30% by weight, the strength of the coating layer is reduced and the film has poor durability. On the other hand, when it exceeds 98%, the heat resistance of the coating layer is poor, and the adhesiveness is likely to occur in the magnetic tape manufacturing process.

The aqueous resin in the present invention may be a coating agent in which a liquid containing 70% by weight or more of water is used as a medium and forcedly dispersed by a surfactant or the like, but it is preferable to use a coating material such as polyethers. It is a self-dispersion type coating agent having a hydrophilic nonionic component or 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. If the amount of the anionic group is less than 0.05% by weight, the water solubility or water dispersibility of the resin is poor, and if the amount of the anionic group exceeds 8% by weight, there is a problem in terms of water resistance and hygroscopicity of the coating layer. May occur.

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 a lubricant, a defoaming agent, a coatability improving agent, a thickener, an antistatic agent, an antioxidant, an ultraviolet absorber, a foaming agent, a dye, a pigment, etc., The effect of the present invention is sufficiently exhibited even in a system containing them.

[0020]

The present invention will be described in more detail with reference to the following examples, 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 diameter (particle diameter) at an integrated volume fraction of 50% in the equivalent spherical distribution measured by the microscopic method was taken as the average particle diameter. (2) Centerline average roughness (Ra) It was determined as follows using a surface roughness measuring device (SE-3F) manufactured by Kosaka Laboratory Ltd. That is, the reference length L (2.55 mm) from the film section curve in the direction of the center line
The part of is drawn out, and the center line of this extracted part is the x-axis,
When the roughness curve y = f (x) is represented with the direction of the longitudinal magnification as the y-axis, the value given by the following formula is represented by [μm]. The center line average roughness was represented by the average value of the center line average roughness of the extracted portions obtained from the 10 section curves obtained from the surface of the sample film. The tip radius of the stylus was 2 μm, the load was 30 mmg, and the cutoff value was 0.0.
It was 8 mm. Ra = (1 / L) ∫ L 0 | f (x) | dx

(3) Adhesion of Calender Roll A polyester film is passed through a calender roll having a polyester resin roll and a hard chrome plating roll so that the coating layer is in contact with the polyester resin roll, 100 ° C., linear pressure 200 Kgf / cm, speed 20 m. / Se
Flowed for 200 m under the condition of c. At this time, the adhesiveness between the coating layer and the polyester resin roll was observed and evaluated according to the following criteria. A: It does not stick at all and runs smoothly until the end. B: Weak sticking is found between the film and resin roll. C: The sticking of the film and roll is severe, and there is a rattling noise or the film meanders. To

(4) Scratch resistance A polyester film is fixed with 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 scratch B: Slight scratch, but satisfactory level C: Small amount of scratch, few deep scratches D: Large amount of scratch, deep scratch E: Large amount of scratches, often deep scratches

(5) Magnetic Tape Characteristics (Characteristics of Magnetic Recording Medium) 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
Parts, 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 form a magnetic paint, which is applied to a polyester film, and then magnetically oriented before the paint is sufficiently dried and solidified. And then dried. Further, this 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-3 manufactured by Matsushita Electric Co., Ltd.
The following magnetic tape characteristics were evaluated at a constant speed using a 700 type video deck. The VTR head output was measured with a VTR head output synchroscope at a measurement frequency of 4 MHz, the reference tape was set to 0.0 decibel (dB), and the relative value was measured (dB). A video tape on which a signal with a dropout number of 4 or 4 MHz was recorded was reproduced, and the dropout number was measured with a dropout counter of Okura Industry Co., Ltd. for about 20 minutes and converted into the number of dropouts per minute.

Comparative 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 and melt-extruded at 290 ° C. to form an amorphous sheet, which is then stretched 3.5 times at 90 ° C. in the longitudinal direction and 3.7 times at 110 ° C. in the transverse direction, and at 210 ° C. for 3 seconds. Heat treatment was performed to obtain a film having a thickness of 15 μm.

Comparative Example 2 After the longitudinal stretching of the polyester sheet of Comparative Example 1, the aluminum oxide particle-containing coating material shown below was applied by dry coating by a bar coating method to a coating thickness of 0.05 μ and then compared. A biaxially stretched polyethylene terephthalate film was obtained in the same manner as in Example 1. Composition of paint containing aluminum oxide particles Aluminum oxide particles (pyrolysis method average particle size 0.02μ
m) 3 parts; polyester resin (Plus Coat Z-461 manufactured by Kyosho Chemical Co., Ltd.) 97 parts; water 900 parts

Example 1 A biaxially stretched polyethylene terephthalate film was obtained in the same manner as in Comparative Example 1 except that the aluminum oxide particle-containing coating material was changed to the one shown below. Composition of paint containing aluminum oxide particles Aluminum oxide particles (pyrolysis method average particle size 0.02μ
m) 3 parts; high molecular weight epoxy resin (DIC Fine EN0270, manufactured by Dainippon Ink & Co., Ltd.) 3 parts; polyester resin (Plus Coat Z-461, manufactured by Kyodo Chemical) 94 parts; water 90
Copy 0

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. Composition of paint containing aluminum oxide particles Aluminum oxide particles (pyrolysis method average particle size 0.02μ
m) 10 parts; high molecular weight epoxy resin (Dainippon Ink Dick Fine EN0270) 10 parts; polyester resin (Kyoso Chemical Plus Coat Z-461) 80 parts; water 9
00 copies

Example 3 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. Composition of paint containing aluminum oxide particles Aluminum oxide particles (pyrolysis method average particle size 0.02μ
m) 30 parts; High molecular weight epoxy resin (Dainippon Ink Dick Fine EN0270) 30 parts; Polyester resin (Kyoso Chemical Plus Coat Z-461) 40 parts; Water 9
00 copies

Comparative Example 3 A biaxially stretched polyethylene terephthalate film was obtained in the same manner as in Example 1, except that the aluminum oxide particle-containing coating material was changed to the one shown below. Composition of paint containing aluminum oxide particles Aluminum oxide particles (pyrolysis method average particle size 0.02μ
m) 60 parts; high molecular weight epoxy resin (Dainippon Ink Dick Fine EN0270) 10 parts; polyester resin (Kyoso Chemical Plus Coat Z-461) 30 parts; water 9
00 copies

Comparative Example 4 A biaxially stretched polyethylene terephthalate film was obtained in the same manner as in Example 1 except that the aluminum oxide particle-containing coating material was changed to the one shown below. Composition of coating material containing particles Aluminum oxide particles (pyrolysis method average particle size 0.02μ
m) 10 parts; high molecular weight epoxy resin (Dainippon Ink Dick Fine EN0270) 60 parts; polyester resin (Kyoso Chemical Plus Coat Z-461) 30 parts; water 9
The results obtained for more than 00 parts are summarized in Table 1 below.

[0031]

[Table 1]

The films of Examples 1 to 3 satisfying the requirements of the present invention are very excellent in calendar adhesion resistance and scratch resistance, so that they are highly satisfactory in electromagnetic characteristics as a magnetic tape. On the other hand, Comparative Example 1 does not have a coating layer and therefore has poor scratch resistance and poor electromagnetic characteristics. Comparative Example 2 is provided with an alumina coat layer, but since the coating layer does not have a high molecular weight epoxy resin,
Although it has good scratch resistance, it has a drawback in calendar adhesion.
Comparative Examples 3 and 4 are examples in which the compounding amount of the alumina particles or the high molecular weight epoxy resin exceeds the requirements of the present invention, but both of them are resistant to deterioration in surface roughness and mechanical strength of the coating layer. Scratch resistance is deteriorated and electromagnetic conversion characteristics are poor.

[0033]

EFFECT OF THE INVENTION The film of the present invention has excellent scratch resistance and calendar roll adhesiveness, and its industrial value is high.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical display location C08K 3/20 KJR 7242-4J C08L 67/02 LPC 8933-4J

Claims (1)

[Claims] 1. A polyester film having a coating layer provided on at least one surface thereof in the step of forming the polyester film, and the coating layer has an average particle size of at least 1 μm.
0.1 to 50% by weight of aluminum oxide particles of m or less,
A polyester film comprising 0.1 to 50% by weight of an aqueous high molecular weight epoxy resin and 30 to 98% by weight of an aqueous polyester resin.