JPS6361028A - Biaxially orientated polyester film - Google Patents

Abstract

PURPOSE:To obtain the titled film, containing specific globular silica particles and other inert and fine inorganic particles having a smaller particle size than that of the above-mentioned silica particles, having excellent slip properties and shaving resistance and suitable for magnetic tape, condenser, etc. CONSTITUTION:In a reaction, for example, during ester interchange reaction for forming (A) a polyester (e.g. polyethylene terephthalate etc.) having preferably 0.4-0.9 intrinsic viscosity (B) 0.005-0.5wt% [based on the component (A)] globular silica particles having 0.4-2mum average particle size and 1.0-1.2 particle size ratio (major axis/minor axis) and (C) 0.005-0.5wt% [based on the component (A)] inert and fine inorganic particles (e.g. pulverized particles of calcium carbonate, etc.) having 0.05-0.6mum average particle size are added to a reaction system as, e.g. a slurry in glycol and the reaction mixture is polymerized, melt formed into film, biaxially drawn, and the thermally fixed to provide the aimed film.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a biaxially oriented polyester film, more specifically, it contains specific spherical silica particles and other inert inorganic fine particles with a smaller particle size, and has a non-slip surface. The present invention relates to a biaxially oriented polyester film with excellent hardness and abrasion resistance.

Polyester films, typified by polyethylene terephthalate films, are used in a wide range of applications because of their excellent physical and chemical properties. For example, for magnetic tape, capacitors, photography, and packaging.

It is used for OHP etc.

In a polyester film, its slipperiness and abrasion resistance are major factors that determine the workability of the film manufacturing process and processing process in each application, as well as the quality of the product.

If these are insufficient, for example, when applying a magnetic layer to the surface of a polyester film and using it as a magnetic tape,
Bt between the coating roll and the film surface when applying the magnetic layer! The II is severe, and the film surface is also abraded, and in extreme cases, wrinkles, scratches, etc. occur on the film surface.

Furthermore, even after slitting a film coated with a magnetic layer and processing it into audio, video, or computer tape, there are many guide parts, playback heads, etc. when pulling it out from a reel or cassette, winding it, or other operations. Significant abrasion occurs between the polyester film, causing scratches and distortion, and furthermore, the surface of the polyester film is scratched and a white powdery substance is deposited, which is often a major cause of missing magnetic recording signals, that is, dropouts.

Generally, to improve the slipperiness of a film, a method is adopted in which the surface of the film is made uneven to reduce the contact area between the film and guide rolls, etc.
Two methods are used: one is to precipitate inactive fine particles from the residual polymer catalyst used as a film raw material, and the other is to add (m) inert inorganic fine particles. A method of adding these raw material fine particles is used. Generally speaking, the larger the size of the fine particles in these raw polymers, the greater the effect of improving slipperiness. Since this itself can cause defects such as dropouts, the unevenness on the film surface needs to be as fine as possible, and there is currently a demand to satisfy these contradictory characteristics at the same time.

Further, in a film made of polyester containing the above-mentioned inert fine particles, peeling occurs at the boundary between the fine particles and the polyester due to biaxial stretching, and voids are formed around the fine particles. The larger the particle is, the larger the void is.
The shape becomes larger when the shape is more spherical than plate-like, when the fine particles are a single particle and are less likely to deform, when the unstretched film is stretched, the stretching area magnification is higher, and when stretching is carried out at a lower temperature. As these voids grow, the shape of the protrusions becomes gentler, increasing the wear coefficient, and small scratches on the voids of the biaxially oriented polyester film that occur during repeated use can also cause particles to fall off. This reduces durability and causes the generation of shavings. It has long been common practice to add one or more of calcium carbonate, titanium oxide, kaolin, etc. (a combination of large particles and small particles) as inert fine particles (JP-A-51-34272.52- 78953.5
2-78954゜53-41355.53-71154
However, since these fine particles form large voids, they have the above-mentioned problem, and improvements in this problem are also desired.

[Purpose of the Invention] The present inventor has solved these disadvantages, and has improved the slipperiness and abrasion resistance of the film by reducing the voids around the inert fine particles and making the film surface moderately rough. The present invention was developed as a result of intensive studies to obtain a biaxially oriented polyester film with suitable surface properties.

Therefore, an object of the present invention is to provide a biaxially oriented polyester film with small voids and excellent slipperiness and abrasion resistance.

[Configuration and Effects of the Invention] According to the present invention, an object of the present invention is to
The first component contains 0.005 to 0.5% by weight of spherical silica particles having an average particle diameter of 0.4 to 2 μm and a particle size ratio (major axis/minor axis) of 1.0 to 1.2. , and the second component has an average particle size smaller than the first component, but is 0.05 to 0.
0.00 of other inert and organic particles in the range of 6 μm.
This is achieved by a biaxially oriented polyester film characterized by containing 5 to 0.5% by weight.

Here, the major axis and minor axis of spherical silica particles are determined to be 10,000 to 30,000 to 30,000 by electron microscopy after metal is deposited on the particle surface.
It is determined from an image magnified 10,000 times, and the average grain size 9 grain size ratio is determined by the following formula.

Average particle diameter = Sum of area equivalent diameters of measured particles / Number of particle diameter ratio of measured particles - Average major axis of silica particles / Average minor axis of the particles The polyester in the present invention has an aromatic dicarboxylic acid as the main acid component, It is a polyester whose main glycol component is aliphatic glycol.

Such polyesters are substantially linear and have film forming properties, particularly by melt molding. Examples of aromatic dicarboxylic acids include terephthalic acid,
Naphthalenedicarboxylic acid, isophthalic acid, diphenylethanedicarboxylic acid, diphenyldicarboxylic acid, diphenyl etherdicarboxylic acid, diphenylsulfonedicarboxylic acid 1! ! , diphenylketone dicarboxylic acid, anthracene dicarboxylic acid, and the like. Examples of aliphatic glycols include ethylene glycol, trimethylene glycol, and tetramethylene glycol.

Examples include fullylene glycols having 2 to 10 carbon atoms such as pentamethylene glycol, hexamethylene glycol, and decamethylene glycol, polyethylene glycol, and alicyclic diols such as cyclohexane dimetatool.

In the present invention, polyesters containing, for example, alkylene terephthalate and/or alkylene naphthalate as main constituents are preferably used.

Among such polyesters, for example, not only polyethylene terephthalate and polyethylene-2,6-naphthalate, but also terephthalic acid and/or 2,6-naphthalenedicarboxylic acid account for 80 mol% or more of the total dicarboxylic acid component, and all glycol A copolymer in which 80 moles or more of the component is ethylene glycol is preferred. In this case, up to 20 mol% of the total acid component can be the above-mentioned aromatic dicarboxylic acids other than terephthalic acid and/or naphthalene dicarboxylic acid; , 4-dicarboxylic acid, and the like. Further, 20 mol% or less of the total glycol component can be the above-mentioned glycols other than ethylene glycol, or for example, hydroquinone, resorcinol, 2.
Aromatic diols such as 2-bis(4-hydroxyphenyl)butane; aliphatic diols containing aromatics such as 1,4-dihydroxymethylbenzene; polyalkylenes such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol. It can also be glycol (polyoxyalkylene glycol) or the like.

Furthermore, in the polyester used in the present invention, a component derived from an oxycarboxylic acid such as an aromatic oxyacid such as hydroxybenzoic acid; an aliphatic oxyacid such as ω-hydrococcaproic acid, a dicarboxylic acid component and an oxycarboxylic acid component. Those copolymerized or bonded in an amount of 20 mol % or less based on the total R of acid components are also included.

Furthermore, the polyester in the present invention contains a substantially linear amount of polycarboxylic acid or polyhydroxy compound, such as trimellitic acid, pentamellitic acid, etc., in an amount of 2 mol% or less based on the total acid component. It also includes those copolymerized with erythritol.

The above polyester is known per se, and can be produced by a method known per se.

The above polyester has an intrinsic viscosity of about 0.4 measured as a solution in 0-chlorophenol at 35°C.
~0.9 is preferred.

The biaxially oriented polyester film of the present invention has many fine protrusions on its surface.

According to the present invention, these many fine protrusions are formed by a large number of spherical silica particles (the first
component) and other inert inorganic fine particles with a smaller particle size (secondary component)
derived from ingredients).

The polyester containing these inert particles dispersed is usually used at any time during the reaction to form the polyester, for example, during the transesterification reaction or polycondensation reaction when using the transesterification method, or at any time during the polycondensation reaction when using the direct polymerization method. It can be prepared by adding spherical silica particles and other inert inorganic fine particles individually or together (preferably as a slurry in glycol) into the reaction system at a certain stage. Preferably, these inert particles are added to the reaction system at the beginning of the polycondensation reaction, for example, until the intrinsic viscosity reaches about 0.3.

In the present invention, the spherical silica particles as the first component dispersed in the polyester have an average particle size of 0.4 to 2 μm.
These are silica particles having a particle size ratio (major axis/breadth axis) of 1.0 to 1.2. These spherical silica particles have individual shapes that are extremely close to true spheres, and the silica particles conventionally known as lubricants are either ultra-fine lumpy particles of about 10 mμ, or they are agglomerated to form particles of about 0.5 μm. It is distinctive in that it is significantly different from forming aggregates (agglomerated particles).

The average particle size of the spherical silica particles is preferably 0.5 to 1.7.
μm, more preferably 0.6 to 1.5 μm.

If the average particle diameter is less than 0.4 μm, the effect of improving slipperiness and abrasion resistance is insufficient, which is not preferable.

Moreover, if the average particle diameter exceeds 2 μm, the surface of the film becomes too rough, which is not preferable. The particle size ratio of the spherical silica particles is preferably 1.0 to 1.15, more preferably 1.0 to 1.
．． It is 1.

Further, it is preferable that the spherical silica particles have a sharp particle size distribution, and the relative standard deviation representing the steepness of the distribution is 0.
It is preferably 5 or less, more preferably 0.4 or less, particularly 0.3 or less. This relative standard deviation is expressed by the following equation.

Here, Di = surface circle equivalent diameter of each particle (μTrL
).

When spherical silica particles with a relative standard deviation of 0.5 or less are used, the heights of the large protrusions on the film surface become extremely uniform because the particles are spherical and have an extremely narrow particle size distribution. Furthermore, the individual large protrusions on the film surface have very sharp protrusion shapes because the voids around the lubricant are small.
Therefore, even with the same number of large protrusions, the slipperiness is extremely good compared to those using other lubricants.

The spherical silica particles are not limited in any way, including the manufacturing method, as long as the above-mentioned conditions are satisfied. For example, spherical silica particles are ethyl orthosilicate [Si (OC2H5)
Hydrolyzed silica [Si(OH)4]
] Monodisperse spheres are created, and this hydrated silica monodisperse method is further dehydrated to grow silica bonds [=Si-0-8i] three-dimensionally (Journal of the Chemical Society of Japan)
'81. Nch9, p'1503).

Si (OC2H5)4 +4H20→Si (O
H) a +4C2IIs 0H=Si -OH+HO-
8i= →; Si −0-8i=+Hz O In the present invention, the amount of spherical silica particles added as the first component is 0.005 to 0.5% by weight based on the polyester.
It is preferably 0.01 to 0.45% by weight, more preferably 0.02 to 0.4% by weight. If the amount added is less than 0.005% by weight, the effect of improving pickling resistance and abrasion resistance will be insufficient, while if it exceeds 0.5% by weight, surface flatness will deteriorate, which is not preferable.

In the present invention, other inert inorganic fine particles as the second component to be dispersed and contained in the polyester are particularly limited as long as they have an average particle size smaller than that of the first component, but within the range of 0.05 to 0.6 μm. Not done. Other inert inorganic fine particles include inert inorganic fine particles precipitated into polymers from catalyst residues, such as calcium carbonate, magnesium carbonate, kaolin, clay, bentonite, titanium oxide, porous silica, and barium sulfate. , calcium titanate, barium titanate, fluorite, barium chromate, glass peas, and the like. These can be used alone or in combination of two or more.

The average particle size of such inert inorganic fine particles is 0.1 to 0.5μ.
, and more preferably 0.15 to 0.4μ.

In order to obtain particles with a predetermined average particle size, a conventionally known particle m production method can be used, for example, pulverization treatment 1
A predetermined average particle size is obtained by performing classification operations, etc.

It is preferable to have a particle size distribution.

In the present invention, the content of the inert inorganic fine particles as the second component needs to be 0.005 to 0.5% by weight, preferably 0.01 to 0.45% by weight, and more preferably 0.01 to 0.45% by weight based on the polyester. is 0.02 to 0.4% by weight.

If this content is less than 0.005% by weight, the effect of improving slipperiness and abrasion resistance will be insufficient, and if it exceeds 0.5% by weight, surface flatness will deteriorate, which is not preferable.

The biaxially oriented polyester film of the present invention can be produced according to conventional methods for producing biaxially oriented films.

For example, polyester containing spherical silica particles and other inert inorganic fine particles is melt-cast to form an amorphous unstretched film, then the unstretched film is stretched in the direction of the two wheels, heat-set, and if necessary It is produced by relaxation heat treatment. At this time, the surface properties of the film vary depending on the particle size, amount, etc. of the spherical silica particles and other inert fine particles, and also depending on the stretching conditions, so they are appropriately selected from conventional stretching conditions. In addition, since the density, thermal shrinkage rate, etc. change depending on the temperature, zero magnification, speed, etc. during stretching and heat treatment, conditions are determined to satisfy these characteristics at the same time. For example, the stretching temperature is such that the first stage stretching temperature (e.g. longitudinal stretching temperature 2T1) is (To-
10) to (T(] +45) 'C range (however, Tg
: glass transition temperature of polyester), the second-stage stretching temperature (for example, lateral stretching temperature: T2) is (T++15) ~
(T+ +40) 'It is best to select from the range of C. Further, the stretching ratio is preferably selected from a range in which the uniaxial stretching ratio is 2.5 or more, particularly 3 times or more, and the area magnification is 8 times or more, especially 10 times or more. Furthermore, the heat setting temperature is preferably selected from the range of 180 to 250°C, more preferably 200 to 230°C.

The biaxially oriented polyester film of the present invention has smaller voids than conventional films, and is characterized by smaller voids, especially around the spherical silica particles. The reason why the voids around the spherical silica particles are small is because the spherical silica particles have a good affinity for polyester, and because the particles themselves are very close to a true sphere, the stress around the lubricant is evenly propagated during stretching, and the polyester It is assumed that this is because stress is not concentrated on a part of the lubricant interface.

In the present invention, the distribution of large projections formed on the surface of the polyester film is extremely uniform due to the addition of spherical silica particles whose particle size distribution is extremely sharp.
A polyester film with uniform protrusion heights can be obtained. By further containing inert inorganic fine particles in this film, it is possible to further improve the slipperiness while maintaining the abrasion resistance.

The biaxially oriented polyester film of the present invention has uniform uneven surface characteristics, excellent slipperiness and abrasion resistance, and is characterized by significantly less generation of scratches, white powder, etc. This biaxially oriented polyester film can be widely used in various applications by taking advantage of these properties. For example, when used as a base film for magnetic recording, such as video, audio, and computer applications, excellent electromagnetic conversion characteristics, slipperiness, running durability, etc. can be obtained.

Furthermore, when used in capacitor applications, low coefficient of friction, excellent windability, low crushing load, high transparency, etc. can be obtained. As mentioned above, this biaxially oriented polyester film is preferably used as a base film for magnetic recording media, particularly as a base film for magnetic tapes, but is not limited thereto, and can be used for electrical applications, packaging applications, vapor deposition films, etc. It can be widely applied to other fields as well.

[Example] The present invention will be further explained below with reference to Examples.

Note that various physical property values and characteristics in the present invention were measured as follows.

(1) Particle size There are the following conditions for particle size measurement.

1) When calculating the average particle size 1 particle size ratio etc. from powder 2) When calculating the average particle size 2 particle size ratio etc. of particles in the film 1) From powder Place the powder on an electron microscope table. The individual particles are scattered so as not to overlap as much as possible, and a gold thin film heat layer is formed on the surface using a gold sputtering device to a thickness of 200 to 300 mm,
Observed with a scanning electron microscope at 10,000 to 30,000 times, and
The major axis (Dli), minor axis (Dsi), and area equivalent (Di) of at least 100 particles are determined. Then, with the number average value expressed by the following formula, the major axis (DI), minor axis (Ds), and average particle diameter (D) of the silica particles are calculated.
represents.

2) In the case of particles in a film, a small piece of sample film was fixed on a sample stage for a scanning electron microscope, and sputtering equipment (JFC-110 manufactured by JEOL Ltd.) was used.
The surface of the film was subjected to ion etching using a Type 0 ion etching apparatus under the following conditions. The conditions were to place the sample in a Pel jar, increase the degree of vacuum to approximately 1O-3 Torr, and apply a voltage of 0.25 KV and 1N1.
Ion etching was performed at 2,51 A for about 10 minutes. Furthermore, using the same equipment, gold sputtering was applied to the film surface, and a scanning electron microscope gave a gold sputter of 10,000 to 30,000.
Observe at double magnification and use Luzex 50 manufactured by Nippon Regulator ■.
0, the major axis (Dli), minor axis (DSi), and area circle equivalent diameter (Dl) of at least 100 particles are determined. Below, above &! Proceed in the same manner as 1).

(2 film surface roughness Ra) JIS-B as center line average roughness (Ra).

601, and in the present invention ■ Koita Research Institute's stylus type surface roughness meter (StJRFCORDER8E-
30C). The measurement conditions are as follows.

(a) Stylus tip radius = 2μm (b) Measurement pressure: 30IIg (C) Cutoff: 0.25am (small measurement length)
: 2.5m+ (lil) Data summary direction - Repeat measurements for the sample 5 times, and take the largest value as 1
The average value of the remaining four data is rounded off to the fourth decimal place and displayed to the third decimal place.

(3) Void ratio The area around the lubricant in the film (surface) is exposed according to the method (1)-2) above, and the long diameter of at least 50 solid particles and the long diameter of the voids are measured. It is expressed as the number average value of the void ratio determined by long axis/long axis of solid fine particles.

(4) Film friction coefficient (μk) In an environment with a temperature of 20°C and a humidity of 60%, a film cut to a width of 172 inches was held at a fixed rod (surface roughness 0.3 μm) at an angle θ = 152.
/ 1807 r radians (152°) and moved at a speed of 200 m/min (II rub). The tension controller is adjusted so that the entrance tension T+ is 359. After the film has traveled 90 meters, the exit tension (Tz: g) is detected by the exit tension detector, and the travel rJ friction coefficient μk is calculated using the following formula. .

μk = (2,303/θ) 10! II (T2
/TI)=0.868100 (T2/3
5) (5) Scrapability The scratchability of the running surface of the base film was evaluated using a 5-stage mini super calendar. The calender was a nylon O-) and steel roll render, and the processing temperature was 80°C. The linear pressure applied to the film is 20ON#/cm
The film was run at a speed of 50 m/min. The running film was run for a total length of 20,007 FL, and the abrasion resistance of the base film was evaluated based on dirt adhering to the top roller of the calendar.

4-level judgment> ◎ No stains on the nylon roll O Almost no stains on the nylon roll × Very dirty on the nylon roll × × Severely dirty on the nylon roll (6) Haze (cloudiness) According to JIS-674, Japan Seimitsu The haze of the film was determined using an integrating sphere HTR meter manufactured by Kogaku Co., Ltd.

Comparative Examples -1 to -6 Using dimethyl terephthalate and ethylene glycol, manganese acetate as a transesterification catalyst, antimony trioxide as a polymerization catalyst, phosphorous acid as a stabilizer, and inorganic fine particles shown in Table 1 as a lubricant. Polymerize using a conventional method, and the intrinsic viscosity (orthochlorophenol, 35°C)
0.62 of polyethylene terephthalate was obtained.

This polyethylene terephthalate (hereinafter abbreviated as PET)
After drying at 110°C for 3 hours, the pellet is fed to the extruder hopper and melted at a melting temperature of 280 to 300°C.The molten polymer is passed through a slit die with a surface finish of about 0.3S and a surface temperature of 20°C. The film was formed and extruded onto a rotating cooling drum to obtain a 200 μm unstretched film.

The unstretched film thus obtained was preheated at 75°C, and then passed between low-speed and high-speed rolls at 90°C from 15M above.
Heated with one IR heater with a surface temperature of 0℃, 3.6
Stretched to double, rapidly cooled, and then fed to a stenter 105
It was stretched 3.7 times in the transverse direction at °C. The obtained two-wheel stretched film was heat-set at a temperature of 205°C for 5 seconds to a thickness of 15 μm.
A heat-set biaxially stretched film was obtained.

The properties of these films are shown in Table 1.

Examples -1 to -8 Comparative examples except that spherical silica (manufactured by Nippon Shokubai Chemical Co., Ltd.) as the first component shown in Table 2 and other inert inorganic fine particles as the second component were used instead of kaolin. A biaxially oriented polyester film was obtained in the same manner as in -1.

The properties of these films are shown in Table 2. .

Claims (1)

[Claims] 1. In the polyester, as the first component, the average particle size is 0.
4 to 2 μm and a particle size ratio (major axis/breadth axis) of 1.0 to
1.2 containing 0.005 to 0.5% by weight of spherical silica particles, and as a second component, other impurities having an average particle diameter smaller than that of the first component but in the range of 0.05 to 0.6 μm. A biaxially oriented polyester film containing 0.005 to 0.5% by weight of active inorganic fine particles. 2. The biaxially oriented polyester film according to claim 1, wherein the relative standard deviation of the spherical silica particles expressed by the following formula is 0.5 or less. Relative standard deviation = ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ Where, Di: Area circle equivalent diameter of individual particles (μm) @D
@: Average value of area circle equivalent diameter (=▲There are mathematical formulas, chemical formulas, tables, etc.▼) (μm) n: Represents the number of particles. 3. The biaxially oriented polyester film according to claim 1 or 2, wherein the other inert fine particles are at least one selected from the group consisting of kaolin, bentonite, titanium oxide, calcium carbonate, and porous silica. .