JPS63234038A - Biaxially oriented polyester film - Google Patents

Abstract

PURPOSE:To obtain the titled film having excellent abrasion resistance, slipperiness, scratch resistance, workability in forming, etc., and suitable e.g. as a base film for magnetic recording, by dispersing specific amount of specific spherical silica particles in a polyester. CONSTITUTION:Preferably at the initial stage of polycondensation reaction for forming a polyester, the reaction system is added with 1-4wt.%, preferably 1-2wt.% spherical silica particles having an average particle diameter of 0.3-4mum, preferably 0.3-2mum, a particle diameter ratio (major diameter/minor diameter) of 1.0-1.2, preferably 1.0-1.1 and a relative standard deviation of preferably <=0.5 [defined by formula I wherein Di is diameter (mum) of circle having equal area to individual particles; D is average value of diameter (mum) of circle having equal area to the particles and defined by formula II; n is number of particles]. The obtained polyester containing spherical silica particles is biaxially drawn and thermally set to obtain the objective biaxially oriented polyester film.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a biaxially oriented polyester film, and more specifically, the present invention relates to a biaxially oriented polyester film that contains specific spherical silica fine particles, has excellent abrasion resistance, and has excellent slip properties, clutch resistance, and processability. The present invention relates to a biaxially oriented polyester film with improved workability.

[Prior Art] Polyester films, represented by polyethylene terephthalate films, have excellent physical properties.

Because of its chemical properties, it is used in a wide range of applications, such as 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,
, the friction between the coating roll and the film surface during application of the magnetic layer is intense, and this also causes severe abrasion of the film surface, which in extreme cases can cause wrinkles on the film surface.
Scratches, etc. may occur. 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 wear occurs between the
As a result of the generation of distortion and the precipitation of white powdery substances due to abrasion of the surface of the polyester film, etc., this often becomes a major cause of missing magnetic recording signals, or in other words, dropouts.

Generally, to improve the slipperiness of a film, a method is adopted in which the contact area between the film and guide rolls etc. is reduced by adding unevenness to the film surface.
Two methods are used: a method in which inert fine particles are precipitated from the polymeric catalyst residue using a film raw material, and a method in which inert inorganic fine particles are added. 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.

In addition, 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 is more spherical than plate-like, the fine particles are single particles that are less likely to deform, the larger the stretching area ratio is when stretching an unstretched film, and the lower the temperature is, the larger the shape is. As these voids get larger, the shape of the protrusions becomes gentler, increasing the coefficient of friction, and small scratches on the voids of the biaxially oriented polyester film that occur during repeated use also cause particles to fall off. This reduces durability and causes the generation of shavings. It has traditionally been common practice to add calcium carbonate, titanium oxide, kaolin, etc. as inert fine particles, but since these fine particles form large voids, they have the above-mentioned problem, and it is also desirable to improve firmness. It is rare.

[Objective of the Invention] The present inventor has solved these disadvantages, and has improved the slipperiness and cracking resistance of the film by reducing the voids around the inert 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 surface properties suitable for various uses.

Therefore, the object of the present invention is to produce biaxially oriented polyester which has small voids, uniform film surface roughness, uniform surface irregularities, and excellent slipperiness, abrasion resistance, scratch resistance, and workability during processing. The goal is to provide film.

[Configuration/Effects of the Invention] According to the present invention, an object of the present invention is to provide polyester with an average particle size of 0.3 μm to 4 μm and a particle size ratio (longer diameter/
This is achieved by a biaxially oriented polyester film containing spherical silica particles having a short axis of 1.0 to 1.2 dispersed in a proportion of more than 1% by weight and less than 4% by weight.

Here, the major axis and minor axis of the spherical silica particles are determined from an image magnified, for example, 10,000 to 30,000 times with a scanning electron microscope after depositing a gold thin film layer on the particle surface, and The diameter 1 particle size ratio is determined by the following formula.

Average particle diameter = sum of area-equivalent diameters of measured particles / particle diameter ratio of number of measured particles = average major diameter of silica particles / average minor diameter of core 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 1, such as terephthalic acid and naphthalene dicarboxylic acid.

Isophthalic acid, diphenoxyethanedicarboxylic acid.

Diphenyl dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenyl sulfone dicarboxylic acid.

Examples include diphenylketone dicarboxylic acid and anthracene dicarboxylic acid. Examples of aliphatic glycols include polymethylene glycols having 2 to 10 carbon atoms such as ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, decamethylene glycol, etc., or alicyclic glycols such as cyclohexane dimetatool. Tribe Geo°
-L, etc.

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, polyethylene terephthalate and polyethylene-2,6-naphthalate, for example, 80 mol% of the total dicarboxylic acid component.
A copolymer in which the above is terephthalic acid and/or 2,6-naphthalenedicarboxylic acid and 80 mol% or more of the total glycol component is ethylene glycol is preferable, in which case 20 mol% or less of the total acid component is terephthalic acid and/or 2,6-naphthalenedicarboxylic acid. /or 2
, 6-naphthalene dicarboxylic acid, and aliphatic dicarboxylic acids such as dichlorohexane-1, adipic acid, sepatic acid, etc.
, 4-dicarboxylic acid, and the like. In addition, up to 20 mol% of the total glycol component can be the above-mentioned glycols other than ethylene glycol, or aromatic diols such as hydroquinone, resorcinol, 2.2-bis(4-hydroxyphenyl)propane, etc. , 4-dihydroxymethylbenzene; aliphatic diols containing aromatic rings; polyethylene glycol, polypropylene glycol;

It can also be a polyalkylene glycol (polyoxyalkylene glycol) such as polytetramethylene glycol.

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-hydroxycaproic acid, a dicarboxylic acid component and an oxycarboxylic acid component. Those copolymerized or combined in an amount of 20 mol % or less based on the total amount of components are also included.

Furthermore, the polyester in the present invention includes a trifunctional or higher functional polycarboxylic acid or a polyhydroxy compound, such as trimellitic acid, in an amount within a substantially linear range, for example, an amount of 2 mol% or less based on the total acid component. Copolymerized products such as bentaerinlitol are also included.

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 O-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 invention, these large numbers of fine protrusions originate from a large number of spherical silica particles that are dispersed and contained in the polyester.

Polyester containing dispersed spherical silica particles is usually produced 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 (preferably as a slurry in glycol) into the reaction system at the same time. Preferably, spherical silica 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 dispersed and contained in the polyester have an average particle diameter of 0.3 to 4 μm and a particle size ratio (major axis/minor axis) of 1.0 to 1.2. It is. These spherical silica particles have individual shapes that are extremely close to true spheres, and the silica particles conventionally known as lubricants are ultrafine lump particles of about 10 mμm.
It is characterized in that it is significantly different from the case where these particles aggregate to form aggregates (M millet particles) of about 0.5μ1m.

The average particle size of the spherical silica particles is preferably 0.3 to 3μ
m, more preferably 0.3 to 2 μm.

If this average particle diameter exceeds 4 μm, the film surface will become too rough, so it is preferable that the particle size ratio of the spherical silica particles be 1.0 to 1.15. More preferably 1.0-1
．． It is 1.

In addition, 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 0.5.
Below, it is more preferably 0.3 or less, particularly preferably 0o15 or less.

This relative standard deviation is expressed by the following formula.

Relative standard deviation = Here, Di2 Area circle equivalent diameter of individual particles (μm) D =
Average diameter equivalent to sum of surface areas (=(Σ Di)/nl (μm) i=1 n: represents the number of particles measured.

When spherical silica particles with a relative standard deviation of 0.5 or less are used, since the particles are spherical and have an extremely steep particle size distribution, the height of the protrusions on the film surface becomes extremely uniform, and the number of protrusions is the same. Also, the slip properties are extremely good compared to the conventional ones.

As long as the spherical silica particles satisfy the above-mentioned conditions, there are no limitations on the manufacturing method or the like.

For example, spherical silica particles are made of ethyl orthosilicate [Si
Hydrous silica [St (OH) A ] monodisperse spheres are produced by hydrolysis of (OCz Hs )a ], and this monodisperse region of hydrated silica is further dehydrated to form silica bonds [;S
It can be manufactured by growing 1-0-311 three-dimensionally. (Journal of the Chemical Society of Japan '81゜Order 9. P, 1503'
).

31 (OCz Hs )a +4Hz O→S i
(OH) a +4. Cz Ha 0H=S i -O
H+HO-3imi→=3 t-o-s tmi+HzO In the present invention, the amount of spherical silica particles added to the polyester needs to be more than 1% by weight and 4% by weight or less, preferably 1% by weight. The content is more than 3% by weight, more preferably 1% by weight and less than 2% by weight. If the amount added exceeds 4% by weight, the abrasion resistance decreases, which is not preferable.

The biaxially oriented polyester film of the present invention can be manufactured according to the conventional methods for manufacturing biaxially oriented films.
For example, a polyester containing spherical silica particles is melt-formed to form an amorphous unstretched film, then the unstretched film is stretched biaxially, heat-set, and if necessary subjected to a relaxing Ml heat treatment. At that time, the surface properties of the film vary depending on the particle size, amount, etc. of the spherical silica particles, and also depending on the stretching conditions, so they are appropriately selected from conventional stretching conditions. In addition, the density, heat shrinkage rate, etc. change depending on the temperature, magnification, speed, etc. during stretching and heat treatment, so the conditions that satisfy these characteristics at the same time are determined. Temperature: T1
) is in the range of (Tg-10) to (7g+45)"C (where Tg is the glass transition temperature of polyester), and the second-stage stretching temperature (for example, transverse stretching temperature: T2) is (T1+5).
) to (T1+40)'C.

Further, the stretching ratio is preferably selected from a range in which the uniaxial stretching ratio is 2.5 or more, especially 3 times or more, and the area magnification is 8 times or more, especially 10 times or more.Furthermore, the heat setting temperature is 180~ It is preferable to select from the range of 250°C, more preferably from 200 to 230°C.

° The biaxially oriented polyester film in the present invention is
This film has extremely small voids compared to conventional films, and the reason why these voids are small is because the spherical silica particles have a good affinity for polyester, and because the particles themselves are extremely close to true spheres, It is presumed that this is because the stress around the lubricant propagates evenly in the process, and the stress does not concentrate on a part of the interface between the polyester and the lubricant.

The biaxially oriented polyester film of the present invention has uniform uneven surface characteristics, excellent slipperiness and abrasion resistance, produces significantly less scratches, white powder, etc., and has excellent workability during processing. It has the following characteristics. Taking advantage of these properties, this biaxially oriented polyester film can be widely used in a variety of applications6.For example, when used as a base film for magnetic recording, such as video, audio, and computer applications, it has excellent electromagnetic conversion properties. Characteristic.

Good slipperiness, running durability, etc. can be obtained. ° Also, when used in capacitor applications, low friction coefficient, 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 Q1, but is not limited thereto, and can be used for electrical applications, packaging applications, and deposition films. It can be widely applied to other fields such as

[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 of silica particles There are the following conditions for particle size measurement.

1) When determining the average particle size, particle size ratio, etc. from silica powder 2) When determining the average particle size, particle size ratio, etc. of silica particles in a film.

1) From silica powder: Scatter the silica powder on a crown sample stage so that the individual particles do not overlap as much as possible, and use a gold sputtering device to
A gold thin film vapor-deposited layer was formed on this surface to a thickness of 2008 to 3 GOA, and the thickness was measured using a scanning electron microscope.
Observe at a magnification of 0,000 times, and measure the length of at least 100 particles (D
li), the short axis (DSi), and the area circle equivalent diameter (Dl).

Then, with the number average value expressed by these following formulas,
It represents the major axis (DI), minor axis (Ds), and average particle diameter (D) of the silica particles.

n n
DI = (Σ D li) /n, D s = (Σ D
Si) / n1 = 11 1 D = (Σ D i ) / n 1 = 1 2) In the case of silica particles in a film: Fix a small piece of sample film on a sample stage for scanning electronic bending, and place it on a JEOL sputtering equipment (JFC-110
0 type ion sputtering device) was used to perform ion etching on the film surface under the following conditions.9 conditions were to place the sample in a Pel jar, increase the degree of vacuum to approximately 104 Torr, and apply a voltage of 0.25 KV. , current 1
．． Ion etching is performed at 25 mA for about 10 minutes. Furthermore, gold sputtering is applied to the film surface using the same equipment, and the film is subjected to gold sputtering using a scanning electron microscope.
Observe at 2x magnification and check the Lusessuk 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.

The following steps are carried out in the same manner as in 1) above.

(23 Particle size ratio of particles other than silica particles, etc. 1) Average particle size CP-SO type Centrifugal particle size analyzer (Centrifugal
parttc+e 5ize Ana+yser)
The particle size corresponding to 50 mass percent is read from the integrated curve of particles of each particle size and their abundance calculated based on the obtained centrifugal sedimentation curve, and this value is calculated as the above average particle size. (See Book "Particle Size Measurement Techniques," published by Nikkan Kogyosho Shimbun, 1975, pp. 1, 242-247).

2) Particle size ratio A small piece of the film is fixed and molded using an epoxy resin, and an ultra-thin section (cut parallel to the film flow direction) with a thickness of approximately 600 mm is prepared using a microtome. The cross-sectional shape of the lubricant (particles) in the film was observed using a transmission electron microscope (manufactured by Hitachi, Ltd., model H-800) and expressed as the ratio of the long axis to the short axis of the lubricant.

3) Relative standard deviation value Measure in the same manner as for silica particles, and for particles other than spherical, calculate the volume from the particle size ratio in the film thickness direction, and define the particle size as the diameter when it is an equioblate sphere. ,
Calculate the relative standard deviation value.

(3 Film surface roughness Ra) This is the value defined in JIS-80601 as the center line average roughness Ra), and in the present invention ■ Koita Research Institute's stylus type surface roughness meter (StlRFCORDERSE-30C) is used. Measure. The measurement conditions are as follows.

(a) Stylus tip radius = 2 μm (b) Measurement pressure: 30q (c) Cutoff, 0.25 cm (d) Measurement length
: 0.5 degree (e) How to summarize the data - Measure 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.

(Void ratio) Expose the area around the lubricant in the film (surface) according to the method (11-2) above, measure the long diameter of at least 50 solid particles and the long diameter of the void, and calculate the following formula: Long diameter void ratio of the void = Solid It is expressed as the number average value of the void ratio determined by the major axis of the fine particles.

(5) Film friction coefficient (μk) In an environment with a temperature of 20°C and a humidity of 60%, a film cut into medium 1/2 inch pieces was held at a fixed rod (surface roughness: 0.3 μm) at an angle θ = (152
/ 180) Contact at yr radian (152°) and move (friction) at a speed of 20G CI+ per minute, exit tension (Tz: g)
is detected by an exit tension detector after the film has traveled 90 m, and the running wear coefficient μk is calculated using the following formula.

μ = (2,303/θ) 100 (Tt /
T1)=0.8f38 too('rz/35)
(61 Duct Fabric Scrapability In an environment with a temperature of 0°C and a humidity of 60%, a film cut to a width of 172 inches was wrapped around a fixed rod (with a corner of 60°) and a cleaning tissue was wrapped at an angle θ = ( 1
G/18G) π radians and move at a speed of 100 m/min. While adjusting the tension controller so that the inlet tension T1 is 50 g, the total length is 1.
The abrasion resistance of the base film is evaluated according to the following criteria based on the state of dirt adhering to the cleaning tissue after running for 00 m.

4-level evaluation: ◎: No stains on the tissue at all ○: Almost no stains on the tissue X゛: Dirt is clearly visible on the tissue.

X×=A line of dirt is clearly visible on the tissue.

(7) Haze (cloudiness) According to JIS-K 674, the haze of the film is determined using an integrating sphere HTR meter manufactured by Nippon Seimitsu Kogaku Co., Ltd.

(8) Scratch determination Magnetic coating tape (1/2 inch width) was applied using the friction coefficient measuring device described in (3) above so that the base film surface of the tape was in contact with the fixed rod at an angle of 152°.
After running for 20 meters at a speed of m/Sec and repeating this 30 times, the thickness, depth, and number of scratches on the surface of the 1/2 inch wide base film are comprehensively judged in the following five stages. .

5-level judgment> ◎ No scratches observed on the 1/2 inch wide base film 0 Almost no scratches observed on the 1/2 inch wide base film Δ Scratches observed on the 1/2 inch wide base film (how many scratches ) × Several thick scratches are observed on the 1/2 inch wide base film xx Many thick and deep scratches are observed all over the 1/2 inch wide base film (9) Coefficient of Static Friction (Film/Film Friction) Lamination A fixed glass plate is placed below the two stacked films, and the film on the lower side of the stacked films (the film in contact with the glass plate) is taken up with a constant speed roll (approximately 10 to 150
11/min), a detector is fixed to one end of the upper film (in the direction in which the lower film is taken and the roadside) to detect the tensile force between the films. The thread used at this time has a weight of 1 to 5 kIr and a lower surface area of 10 to 100 as2.

Comparative Example 1 Dimethyl terephthalate and ethylene glycol were transesterified, manganese acetate was used as a transesterification catalyst, antimony trioxide was used as a polymerization catalyst, hypophosic acid was used as a stabilizer, and an average particle size of 1.2 μm and a particle size ratio of 10 were used as a lubricant. Polyethylene terephthalate having an intrinsic viscosity (orthochlorophenol, 35° C.) of 0.62 was obtained by polymerization using kaolin of .0.

This polyethylene terephthalate pellet was heated to 170°C.
, after drying for 3 hours, fed to the extruder hopper, melting temperature 28
The molten polymer was melted at 0 to 300° C. and extruded through a slit-shaped die with a diameter of 1 mm onto a rotating cooling drum with a surface finish of about 0.3 S and a surface temperature of 20° C. to obtain an unstretched film of 400 μm.

The unstretched film thus obtained was preheated at 75°C, and further rolled between low speed and high speed rolls for 90°
Heated with one IR heater with a surface temperature of 0℃ to 3.6
Stretched to double, rapidly cooled, and then fed to a stenter 105
It was stretched 3.72 times in the transverse direction at °C. The obtained biaxially oriented film was heat-set at a temperature of 205°C for 5 seconds to a thickness of 3
A heat-set biaxially oriented film of 0 μm was obtained.

The resulting film had a void ratio of 1.7, and white powder adhered to it when calendered, making it unsatisfactory.

Furthermore, the properties of this film are shown in Table 1.

Comparative Example 2 Same as Comparative Example 1 except that calcium carbonate with an average particle size of 0.8 μm and a particle size ratio of 1.5 was used instead of kaolin.
Obtain polyethylene terephthalate pellets.

Using this pellet, a thickness of 30 mm was prepared in the same manner as in Comparative Example 1.
A micrometer biaxially oriented film was obtained. Although this film had a void ratio of 2.0 and had good running properties, white powder was generated during the dust fabrication process.

Furthermore, the properties of this film are shown in Table 1.

Comparative Example 3 Pellets of polyethylene terephthalate were obtained in the same manner as in Comparative Example except that titanium oxide having an average particle size of 0.4 μm and a particle size ratio of 2.0 was used instead of kaolin.

Using this pellet, a thickness of 30 mm was prepared in the same manner as in Comparative Example 1.
A micrometer biaxially oriented film was obtained. The void ratio of this film is 1.8, the friction between the films is high, the workability is poor, the running properties are poor, white powder is generated in the D/F processing process and the running system, and in this state it can be used as a tape. Since this was not possible, we were forced to apply a slippery layer to the back side. The properties of this film are shown in Table 1.

Table 1 Examples 1 to 5 and Comparative Example 4 Polyethylene terephthalate pellets were prepared in the same manner as in Comparative Example 1 except that silica fine particles adjusted to the average particle size and particle size ratio shown in Table 2 were used instead of kaolin. I got it.

A heat-set biaxially oriented polyester film having a thickness of 30 μm was obtained by carrying out the same procedure as in Comparative Example 1 except for using RET. The properties of this film are shown in Table 1.

All of the biaxially oriented films obtained in the examples showed excellent slip properties and scratch resistance, and also had extremely good abrasion resistance even in the D/F treatment process, and also had low film-to-film friction and good workability. All were of good quality.

On the other hand, as shown in Comparative Example 4, the particle size of spherical silica is 4 μm.
If it exceeds , white powder will be generated during the dust fabric treatment and the abrasion resistance will be poor.

Example 6.7 A biaxially oriented polyester film was obtained in the same manner as in Example 3.4 except that the stretching ratios in Examples 1 and 2 were changed to 4.5 times in the longitudinal direction and 3.6 times in the transverse direction. The properties of this film are shown in Table 2.

Claims (1)

[Claims] 1. 1% by weight of spherical silica particles having an average particle diameter of 0.3 to 4 μm and a particle size ratio (major axis/minor axis) of 1.0 to 1.2 in polyester. A biaxially oriented polyester film containing dispersed content in a proportion of 4% by weight or less. 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 = √{[Σ^n_i_=_1(Di-@D@)^2/n]
/@D@｝Here, Di: Area circle equivalent diameter of each particle (μm) @D@: Average value of area circle equivalent diameter {=(Σ＾n_i_=_1Di)/n} (μm) n: Particle diameter Represents the number of pieces.