JPS63221136A - Polyester film - Google Patents

Abstract

PURPOSE:To obtain a biaxially oriented polyester film excellent in chipping resistance and useful as a base film for videotapes, by molding a composition comprising a polyester and inert inorganic particles while controlling the relationship between the half-value widths of the Raman bands of the outermost layer and inside of a film. CONSTITUTION:0.05-1.0wt.%, based on the product, slurried inert inorganic particles of an average particle diameter of 0.1-1.0mu are dispersed in a diol component of a polyester (e.g., ethylene glycol), and an acid component [e.g., terephthalic acid (dimethyl ester)] is added to this diol component. The mixture is transesterified and polycondensed to obtain composition comprising a polyester and the inert inorganic particles. This composition is extruded at 270-330 deg.C with a draft ratio of 5-30 and the formed unoriented film is heat-treated and biaxially oriented at a speed of orientation of 1X10<3>-7X10<4>%/min and an orientation ratio of 3.0-5.0 and heat-treated for 0.5-60sec at 130-210 deg.C in an atmosphere of steam to obtain the title biaxially oriented film in at least either of which surfaces the half-value width of the Raman band ascribable to CO groups on the outermost layer is greater than that of the inside by at least 1cm<-1>.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to biaxially oriented polyester films.

[Prior Art] As a biaxially oriented polyester film, a film made of polyester containing inert inorganic particles is known (for example, Japanese Patent Laid-Open No. 178224/1983).

[Problems to be solved by the invention] However, the above conventional biaxially oriented polyester film has the following problems:
As the process speed increases in film processing processes, such as printing processes for packaging applications, magnetic layer coating for magnetic media applications, and calendering processes, the surface of the film is abraded by contacting rolls, resulting in damage to the product during the processing process. The drawback of performance problems has recently become a problem.

The object of the present invention is to improve such problems and provide a film with excellent surface "scratching resistance."

[Means for Solving the Problems] A biaxially oriented film whose main components are a composition consisting of polyester and at least one type of inert inorganic particle, which has a Raman oriented film based on a carbonyl group on the extreme surface layer of the film on at least one side. The biaxially oriented polyester film is characterized in that the half width of the band is 1 cm-' or more larger than the half width of the inside of the film.

Polyester in the present invention refers to ethylene terephthalate, ethylene α, β-bis(2-chlorophenoxy)
Ethane-4,4-dicarboxylate, ethylene 2,6
- Contains at least one structural unit selected from naphthalate units as a main constituent. However, other components may be copolymerized within a range that does not impede the present invention, preferably within 5 mol%.

In addition, polyester containing ethylene terephthalate as a main component is particularly desirable because it has even better abrasion resistance.

The type of inert inorganic particles in the present invention is not particularly limited, but when the crystallization promotion coefficient is in the range of 15 to 20 °C, preferably 15 to 15 °C, more preferably 0 to 10 °C, This is particularly desirable since it becomes extremely easy to obtain a Raman band half width within the range of the present invention. Furthermore, among these, substantially spherical silica derived from colloidal silica, synthetic calcium carbonate, titanium oxide, and α-alumina are particularly desirable. It is desirable that the colloidal silica referred to here be particles produced in the process of removing alkali from sodium silicate.

The content of inert inorganic particles in the present invention is not particularly limited, but is 0.05 to 1.0% by weight, particularly 0.1 to 0.8% by weight.
% by weight is particularly desirable because the abrasion resistance becomes even better.

The average particle size of the inert inorganic particles in the present invention is not particularly limited, but is 0.1 to 1.0 μm, particularly 0°15 to 0.8 μm.
It is particularly desirable that the thickness is μm because the abrasion resistance becomes even better.

In the present invention, two or more types of inert inorganic particles may be used, or two or more types of the same type with different average particle sizes may be used in combination, or they may be used in combination with internally precipitated particles. The film of the present invention has the above-mentioned composition as a main component, but other polymers may be blended within the range that does not impede the purpose of the present invention, and antioxidants, heat stabilizers, lubricants, ultraviolet absorbers, etc. Inorganic or organic additives such as additives, nucleating agents, etc. may be added to the extent that they are normally added.

The film of the present invention is a film in which the above composition is biaxially oriented. An unstretched film or a -axis oriented film is not preferred because it has poor abrasion resistance.

In addition, the plane orientation index representing the degree of biaxial orientation is not particularly limited, but is 0.935 to 0.975, particularly 0.94
A range of 0 to 0.970 is particularly desirable because the abrasion resistance becomes even better.

The half-value width of the Raman band based on the stretching vibration of the carbonyl group in the extreme surface layer of the film of the present invention is 1CIW-1, preferably 2CIII-1, than the half-value width of the Raman band based on the stretching vibration of the carbonyl group inside the film. It needs to be bigger than that. If the difference in these half widths is smaller than the above range, the abrasion resistance of the film will be poor, which is not preferable. Note that the upper limit of this difference is not particularly limited, but usually about Bcm' is the manufacturing limit. here,
The above half width is measured by the method described below,
A: The half width of the Raman band based on the stretching vibration of carbonyl groups is inversely proportional to the density of polyester.
, J, ne+veger (J, Polymer 5science 10
, 317.1972 >.

Further, the half-width of the Raman band of the carbonyl group in the extreme surface layer of the film of the present invention is not particularly limited, but it is particularly desirable if it is 15 cm or more, preferably 17 cm-' or more, because the abrasion resistance will be even better. .

The film of the present invention has an average surface roughness Ra of 0.0 in the width direction.
05-0.030μm, especially 0.007-0.020μm
A range of m is particularly desirable because the abrasion resistance becomes even better.

The film of the present invention has a melt viscosity of 1,000 to 10,000 poise at 290°C and 200 SeC, particularly 2,000 to 10,000 poise.
A range of 7000 voids is particularly desirable because the abrasion resistance is even better.

Next, a method for producing the film of the present invention will be explained.

First, as a method for incorporating inert inorganic particles into a given polyester, they may be added before, during, or after polymerization, but they can be added in the form of a slurry to ethylene glycol, which is the diol component of the polyester. A method of mixing, dispersing, and adding is effective in satisfying the relational expression of the present invention. Further, as a method for adjusting the content of inert inorganic particles, a method of diluting a highly concentrated master pellet during film formation is effective for obtaining a Raman band half width within the range of the present invention. In this case, using inert inorganic particles with a Mohs hardness of 3 or more, when dispersing in ethylene glycol, 195
A method of heat treatment at ℃ for 2 hours or 0% for inorganic particles.
．． The method of adding 5 to 20% by weight of ammonium phosphate salt is extremely effective in bringing the relationship between the Raman band half-width in the extreme surface layer and the inside of the film within the range of the present invention.

After sufficiently drying the pellets containing a predetermined amount of inert inorganic particles, the pellets were fed to a known melt extruder and 27
It is extruded into a sheet through a slit-shaped die at 0 to 330°C, and cooled and solidified on a casting roll to produce an unstretched film. In this case, it is effective to set the draft ratio during extrusion (die slit gap/unstretched film thickness) in the range of 5 to 30, preferably 8 to 20, to satisfy the Raman band half width of the present invention. be.

Next, this unstretched film is biaxially stretched and biaxially oriented. As the stretching method, a sequential biaxial stretching method or a simultaneous two-wheel stretching method can be used.

In the case of the sequential two-wheel stretching method, it is common to stretch in the longitudinal direction and then in the width direction, but this order may be reversed. The conditions for two-wheel stretching are not necessarily constant depending on the stretching method, the type of polymer, etc., but are usually in the range of 80 to 160°C, preferably 90 to 150°C in both the longitudinal and width directions, and the stretching ratio is 3.0 to 3.0°C, respectively. A range of 5.0 times, preferably 3.2 to 4.5 times is suitable. Further, the stretching speed is preferably in the range of 1.times.10.sup.3 to 7.times.10.sup.4%/min.

Here, before stretching, the unstretched film was
C. for 0.1 to 60 seconds is effective in satisfying the Raman band half width of the present invention.

Next, this stretched film is heat treated, and the heat treatment conditions at this time are as follows: 130 to 21
Heat treatment at a temperature range of 0° C., especially 130 to 180° C., or heat treatment using microwaves is extremely effective in satisfying the Raman band width of the present invention. The time is 0.5
Processing at a constant length for ~60 seconds is preferred.

[Function] The present invention detects the relationship between the half-width of the Raman band of the extreme surface layer of the film and the half-width of the inside of the film, which is detected by a special method, that is, the relationship between the density of the extreme surface layer of the film and the density of the inside of the film, within a specific range. Therefore, it is presumed that the effects of the present invention were obtained as a result of the film being able to have a large impact absorption capacity when an external shearing force is applied to the film surface.

[Method of Measuring Physical Properties and Evaluating Effects] The methods of measuring the characteristic values and evaluating the effects of the present invention are as follows.

(1) Polyester was removed from the average particle diameter film of inorganic fine particles by plasma ashing treatment or O-chlorophenol dissolution method, and this was dispersed in ethanol and centrifugal sedimentation method (Horiba, CAPA5
00) is the volume average diameter measured.

(2) Content of inorganic fine particles: O-chlorophenol 1°00 per 100g of polyester
was added and heated at 120°C for 3 hours, and then centrifuged at 30°C using a bean centrifuge 55P-72 manufactured by Hitachi Ichiki Co., Ltd.
Stretch separation was carried out for 40 minutes at n+, and the obtained particles were
Vacuum dry at 0°C. When the fine particles are measured using a scanning differential calorimeter, if a melting peak corresponding to the polymer is observed, the fine particles are heated and cooled with O-chlorophenol, and then the stretching separation operation is performed again. When the melting peak is no longer observed, the fine particles are considered to be precipitated particles. Normally the stretching separation operation is 2
times is enough.

(3) Film extreme surface layer Raman band half width JObi
The total reflection Raman spectrum was measured using a RamanOr U-1000 Raman system manufactured by n-YVOn, and the half-value width of 1730 cm, which is a stretching image of a carbonyl group, was determined.The measurement conditions are as follows.Measurement The depth is 500-1000 people from the surface.

■ Light source Argon ion laser (5145 people) ■ Setting the sample Press the film surface onto a total reflection prism so that the laser polarization direction (S polarization) and the film longitudinal direction are parallel, and set the laser incidence angle to the prism ( The angle with respect to the film thickness direction was 60'.

■ Detector P) 1: RCA31034/Proton Count
ing System (Hamamatsu c12
30) (SUPPLY 1600V)■ Measurement conditions 5LIT 1000μm LASER100mW GATE TIHE 1, 0secSCAN 5P
EED 12Cm-'/m1nSA)IPLING
INTERVAL 0.2cm-'REPEAT T
IME 6 (4) Film internal (bulk) Raman band half width The same Raman system as in (3) above was used. However, a total reflection prism is not used, and the incident angle of the laser is set to 70°.
By setting it to 0, specularly reflected light was allowed to escape and only Raman scattered light was detected. In other words, whereas the measurement in (3) above takes advantage of the fact that light slightly penetrates the film surface during total reflection and obtains information about the extreme surface layer, here we measure the Raman inside the film without total reflection. Information is obtained from scattered light. Other conditions are REPEA
T・TI) Same as (3) above except that IE is 4 times.

(5) Planar orientation index Using a refractometer with sodium D line (wavelength 589nll) as a light source, measure the refractive index in the thickness direction of the biaxially oriented film (referred to as A) and place it in water at 10°C after melt pressing. The refractive index (referred to as B) in the thickness direction of the non-oriented (amorphous) film produced by rapid cooling was measured, and A/B was taken as the plane orientation index. Methylene iodide was used as the mounting solution, and the measurement was performed at 25° C. and 65% RH.

(6) Measurement was performed using a melt viscosity enhancement type flow tester at a temperature of 290°C and a shear rate of 200 seconds.

(7) Surface average roughness Ra Measured using a stylus type surface roughness meter according to JIS-8-0601. However, the cutoff is o, osmm,
Measurement length is 11III1 and 11.

(8) Glass transition point Tg, cold crystallization temperature TCC Measured using a DSC (differential scanning calorimeter) model 2 manufactured by PerkinElmer. The DSC measurement conditions are as follows. That is, 10m0 of the sample was set in the DSC device, and 300m
After melting for 5 minutes at a temperature of °C, it is quenched into liquid nitrogen.

This rapidly cooled sample was heated at a rate of 10°C/min, and the glass transition point Tg
Detect.

The temperature was continued to be gradually raised, and the exothermic peak temperature of crystallization from the glass state was defined as the cold crystallization temperature Tcc.

Here, the difference between TCC and Tg (Tcc-Tg) is defined as ΔTcg.

(9) Crystallization promotion coefficient (unit: °C) ΔTC of polyester containing 1% by weight of inert inorganic particles by the above method
g(I) and ΔTcg(II) of a polyester containing no inert inorganic particles having the same viscosity as this, and ΔTcg(II).
The difference between Cg(II) and ΔTCII> [ΔTCCI (II
)-8TCCI(■)] was taken as the crystallization promotion coefficient of the inert inorganic particles.

(b)) Press one blade vertically against a tape-like slit of abrasion-resistant film 1/2 inch wide, push it further 0°5 mm, and run it 20 cm (running tension 500 g, running speed 5.7 cm) /second). (7) The height of the scraped material on the film surface attached to the tip of the R1 single blade was read using a microscope and was defined as the amount of scraped material (unit: μm). When the amount of abrasion (average value on both surfaces) was 15 μm or less, the abrasion resistance was determined to be good, and when it exceeded 15 μm, the abrasion resistance was determined to be poor. This amount of wear:
The value of 15 .mu.m is the critical point in determining whether or not troubles in the process and product performance will occur due to the film surface being scraped during processing steps such as the printing process and the calendering process.

[Example code] The present invention will be explained based on examples.

Example 1 Titanium oxide having an average particle size of 0.3 μm was dispersed in ethylene glycol in the form of a slurry at a concentration of 1% by weight. At this time,
1% by weight of tetraethylammonium phosphate (phosphoric acid and tetraethylammonium hydroxide mixed at a molar ratio of 1:1) was added to titanium oxide, and 50μ
After dispersing m-diameter glass pieces as media,
The glass pieces were filtered off to prepare a slurry.

This ethylene glycol and dimethyl terephthalate are transesterified and then polycondensed to produce 1% by weight of titanium oxide particles.
A polyethylene terephthalate containing polyethylene terephthalate was made. The crystallization promotion coefficient of this titanium oxide was 2.5°C.

These polyethylene terephthalate pellets and polyethylene terephthalate pellets containing no inorganic particles were mixed so that the titanium oxide content was 0.4% by weight. This mixed pellet was dried under reduced pressure at 180°C for 3 hours (
3 TOrr) Shita. Feed this pellet to the extruder,
It was melt-extruded at 300°C, the draft ratio was set to 15, and the electrostatic casting method was used to wind it around a casting drum with a surface temperature of 30°C, which was then cooled and solidified to a thickness of about 180. #
An unstretched film of m was made. This unstretched film
After heat treatment at 30'C for 1 minute, it was stretched 3.4 times in the longitudinal direction at 90C.

This stretching was carried out using a difference in peripheral speed between two sets of rolls, and the stretching speed was 10,000%/min. This -axis film was stretched 3.6 times in the width direction at 100°C at a stretching rate of 2000%/min using a stenter. This film was heated in water vapor for 14 hours.
A biaxially oriented film with a thickness of 15 μm was obtained by heat treatment at 0° C. for 20 seconds.

The Raman band half width of the extreme surface layer of this film is 18 cm' on both sides, and the Raman band half width of the inside of the film is 16 Cm'.
cm-1, and the difference therebetween was 2 C11l-1, which satisfied the relationship of the present invention. As a result of examining the abrasion resistance of the surface of this film, the amount of abrasion was 4 μm, and the abrasion resistance was good.

Examples 2 to 4, Comparative Examples 1 to 3 Various inorganic particles having an average particle diameter of 0.5 μm were dispersed in ethylene glycol in the form of a slurry by changing the dispersion method (the concentration of the inorganic particles was 1% by weight).

This ethylene glycol and dimethyl terephthalate were transesterified and then polycondensed to produce polyethylene terephthalate containing 1% by weight of inorganic particles. The crystallization promotion coefficients of these inorganic particles were as shown in Table 1.

These polyethylene terephthalate pellets and polyethylene terephthalate pellets containing no inorganic particles were mixed so that the inorganic particle content was 0.25% by weight. The mixed pellets were dried under reduced pressure at 180°C for 3 hours (
3 Torr) L/Ta. The pellets were fed into an extruder and melt-extruded at 300°C, with a draft ratio of 15, wound around a casting drum with a surface temperature of 30°C using the electrostatic casting method, and cooled and solidified to a thickness of approximately 180μ.
An unstretched film of m was made. This unstretched film was subjected to various treatments and then stretched 3° to 4 times in the longitudinal direction at 90°C.

This stretching was carried out using a difference in peripheral speed between two sets of rolls, and the stretching speed was 10,000%/min. This -axis film was stretched 3.6 times in the width direction at 100°C at a stretching rate of 2000%/min using a stenter. This film is processed by various methods.
Heat treatment was performed for 0 seconds to obtain a film with a thickness of 15 μm.

The Raman band half width of the extreme surface layer of these films, the Raman band half width of the inside of the film, and the abrasion resistance of the film are as shown in Table 1, and when the Raman band half width is within the range of the present invention. The abrasion resistance was good in some cases, but it was poor in other cases. It can be seen that even if the type of inert inorganic particles are the same, the scratch resistance differs greatly depending on the relationship between the half width of the Raman band of the film.

Effects of the invention] The present invention controls the relationship between the Raman band half-width of the extreme surface layer of the film and the half-width inside the film, which is detected by a special method, that is, the relationship between the density of the extreme surface layer of the film and the density inside the film. As a result, the abrasion resistance of the surface can be improved, and even if the processing process is sped up, the film surface will not be abraded, which can cause problems in the processing process and product performance. It is something that

The use of the film of the present invention is not particularly limited, but it is useful as a base film for magnetic recording media, especially video tapes, where film abrasion tends to cause problems in product performance.

Claims (1)

[Claims] A biaxially oriented film mainly composed of a composition consisting of polyester and at least one type of inert inorganic particle, in which the half-width of the Raman band due to the carbonyl group on the extreme surface layer of the film on at least one side is equal to that of the inside of the film. A biaxially oriented polyester film having a width at half maximum of 1 cm or more.