JPH02143836A - Biaxially-oriented polyester film and its manufacture - Google Patents

Abstract

PURPOSE:To contrive improvements in scratch resistance and dubbing resistance, by a method wherein a surface roughness parameter is set so as to fall within a specific range. CONSTITUTION:A surface roughness parameter Rt/Ra of at least one side is 8.0 or lower, in a film. A surface roughness parameter sigma/H of the one side may be 0.8 or lower. It is preferable further that a total reflection Raman crystallizing index of the one side is at least 15cm<-1>. Facial protrusions are formed at least on the one side of a biaxially-oriented polyester film like this through particles contained within polyester. It is preferable that the additive particles whose mean particle diameter is 0.02-1.0mum are added at the time of polymerization of the polyester, high-density master pellets are obtained and diluted at the time of film manufacturing. A range of 0.56-0.8 is preferable for intrinsic viscosity in this instance. It is effective to obtain the above- mentioned surface parameter that the obtainable polyester containing the particles is laminated at a thickness of 0.2-5mum on at least the one side of the polyester film and the product of a lengthwise and crosswise draw ratios is made at least 10 times.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a biaxially oriented polyester film and a method for producing the same.

[Prior Art] As a biaxially oriented polyester film, a film with improved running properties on at least one side is known (for example, Japanese Patent Publication No. 18249/1983).

[Problems to be Solved by the Invention] However, with the above-mentioned conventional biaxially oriented polyester film, it is difficult to manufacture a soft tape, etc. by, for example, applying a magnetic layer in magnetic media applications, a calendering process, or dubbing the finished videotape. As the process speed increases, there is a drawback that the film surface is scratched by the contacting rolls and guides. In addition, in the conventional
Due to the above image quality deterioration during dubbing, the image quality when converted to videotape, that is, the S/N (signal/noise ratio)
It also had the drawback of being insufficient. The present invention solves these problems, and reduces the risk of scratches on the film especially during high-speed processes (hereinafter referred to as "excellent scratch resistance") and reduces the deterioration of image quality during dubbing (hereinafter referred to as "excellent dubbing resistance").
An object of the present invention is to provide a biaxially oriented polyester film and a method for producing the same.

[Means for Solving the Problems] The present invention provides (1) a biaxially oriented polyester film characterized in that the surface roughness parameter R1/Ra on at least one side is 8.0 or less; A biaxially oriented polyester film characterized by a surface roughness parameter σ/H of 0°8 or less; (3) a total reflection Raman crystallization index of at least one side of 15 cm-' or more; The biaxially oriented polyester film according to (1) or (2) above, (4) an average particle size of 0.02 to 1°0μ on at least one side of the polyester film.
After laminating 0.2 to 5 μm of polyester containing particles of m and having an intrinsic viscosity of 0.56 to 0°8, it is biaxially stretched so that the product of the longitudinal and horizontal stretching ratios is 10 times or more. The present invention relates to a method for producing a biaxially oriented polyester film according to any one of (1) to (3) above.

The polyester in the present invention is a polyester having an aromatic dicarboxylic acid as a main acid component and an aromatic or aliphatic diol as a main glycol component. There are no particular limitations as long as it has film formability, but ethylene terephthalate, ethylene-α, β-bis(2-chlorophenoxy)ethane-4,4°-dicarboxylate, and ethylene-2,6-naphthalate units may be used. It is preferable to use it as a main component. However, other components may be copolymerized within a range that does not impede the present invention, preferably within 15 mol%. Furthermore, polyester containing ethylene terephthalate as a main component is particularly desirable because it has even better dubbing resistance.

At least one side of the biaxially oriented polyester film in the present invention has surface protrusions formed by particles contained in the polyester. It is extremely desirable for the particles used in the present invention to have a relative standard deviation of 065 or less, preferably 0.4 or less, as this provides even better scratch resistance and dabbing resistance. Furthermore, it is extremely desirable for the particles to have a spherical shape, since this provides even better scratch resistance and dabbing resistance. The types of particles are not particularly limited as long as they are inert to polyester, but include silica derived from colloidal silica, organic polymer particles, especially crosslinked polymer particles, such as crosslinked spherical styrene-divinylbenzene. Copolymer particles are preferred. Moreover, the surface may be surface-modified.

The average particle size of the additive particles is not particularly limited, but is 0°02~
A thickness of 1.0 μm, preferably 0.02 to 0.5 μm, is desirable because scratch resistance and dubbing resistance are even better. It is effective to obtain the surface morphology of the present invention when the content of the particles of the present invention is 0.3 to 50% by weight, preferably 0.5 to 30% by weight, and more preferably 0.8 to 20% by weight. be.

The film of the present invention has the above composition as a main component, but
Other types of polymers may be blended within the range that does not impede the purpose of the present invention, and antioxidants, heat stabilizers, lubricants,
Inorganic or organic additives such as ultraviolet absorbers and nucleating agents,
It may be added to the extent that it is normally added. The present invention is a film in which the above-mentioned composition is biaxially oriented, and the refractive index ratio in the thickness direction indicating the degree of orientation is not particularly limited, but when it is in the range of 0.935 to 0.970, This is particularly desirable since scratch resistance and dubbing resistance are further improved. Furthermore, the difference ΔTcg (=Tcc−Tg) between the glass transition point Tg and the cold crystallization temperature Tcc is 30 to 1
A temperature of 20° C. is particularly desirable because scratch resistance and dubbing resistance become even better.

In terms of scratch resistance and dubbing resistance, the film of the present invention (1) has a surface roughness parameter Ri/
It is necessary that Ra is 8.0 or less. More preferably, R1/Ra is 7.5 or less, even more preferably R1
/Ra is 7.0 or less. The lower limit of Rj/Ra is approximately 4.0, which is the manufacturing limit.

In terms of scratch resistance and dubbing resistance, the film of the present invention (2) has a surface roughness parameter σ/H on at least one side.
is required to be 0.8 or less. More preferably, σ/H is 0.7 or less, and even more preferably σ/H is 0.7.
6 or less. The lower limit of σ/H is approximately 0.01, which is the manufacturing limit.

Furthermore, in terms of scratch resistance and dubbing resistance, the film of the present invention desirably has a total reflection Raman crystallization index of at least one side of 15 cm-' or more. More preferably, the total reflection Raman crystallization index is 17 cm-' or more,
More preferably, the total reflection Raman crystallization index is 18 cm-
'That's it. Total reflection Raman crystallization index is approximately 25
cm-' is the manufacturing limit.

Although the Young's modulus of the film of the present invention is not particularly limited, it is particularly desirable that the Young's modulus in both the longitudinal direction and the width direction be 400 kg/mm 2 or more, since the dubbing resistance will be even better. Further, it is particularly desirable that the Young's modulus in the width direction is 100 kg/mm2 or more higher than the Young's modulus in the longitudinal direction, since the dubbing resistance will be even better. Also,
The film of the present invention has a surface protrusion number N (1/mm2)
, particle content C (wt%), and particle diameter D (nm)
The value ND3/C obtained from is 4x1013 or more, preferably 7x1013 or more, more preferably 10x1
013 or higher is particularly desirable because the dubbing resistance becomes even better.

Next, a method for manufacturing the film of the present invention will be described.

The polyester of the film of the present invention can be obtained by polycondensation via direct esterification or by polycondensation via transesterification. As a method of adding particles to the polymer, a method of adding them during polymerization can be used. As a method for adjusting the particle content, a master pellet method is preferred in which a master pellet with a high concentration, preferably a master pellet with a particle concentration of 3 to 50% by weight, is diluted during film formation. In this case, the intrinsic viscosity is preferably in the range of 0.56 to 0.8. Further, when adjusting the intrinsic viscosity and copolymerization component of the master pellet to make the ΔTcg in the range of 70 to 100°C, and diluting the master polymer with a polyester containing substantially no particles, the ΔTc of the master pellet is
gl and ΔTc of substantially particle-free polyester
Difference from gQ (dΔT cg=ΔTcgQ−ΔTcgl)
Keeping the temperature below 10℃, preferably below 5℃,
This is extremely effective for obtaining the surface parameters of the present invention.

In that case, the average particle diameter of the additive particles is desirably 0.1 to 20 times, more preferably 0.2 to 10 times, the thickness of the laminated portion after stretching.

Laminating the particle-containing polyester obtained above in a thickness of 0.2 to 5 μm on at least one side of a polyester film is extremely effective in obtaining the surface parameters of the present invention. That is, particle-containing polyester A and polyester B
are supplied to different melt extruders, passed through a pinol and feed block with a polymer flow channel having a rectangular cross-section, and discharged in a sheet form from a slit-shaped mouthpiece to be cooled and solidified to produce an unstretched film. In this case, in order to obtain the surface parameters within the range of the present invention, the ratio of the die slit gap to the unstretched film thickness should be in the range of 5 to 30, preferably 8 to 20 when extrusion molding is performed on the unstretched film. Extremely effective. In that case, the thickness of the laminated part is 0.2~5μ
m1 is preferably 0°2 to 3 μm.

Next, by biaxially stretching and orientating this unstretched film, the laminated portion of the film of the present invention is also biaxially stretched.

As the stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used.

In this case, the stretching conditions include first stretching 3 to 5 times in the longitudinal direction and then 3 to 5 times in the width direction, so that the product of the longitudinal and lateral stretching ratios is 10 times or more. It is effective for obtaining The use of electrostatic nipping, rather than mechanical nipping between rolls, in longitudinal stretching is particularly effective in obtaining the surface parameters of the present invention. As for the stretching temperature, a range of Tg-Tg+20°C is effective for obtaining the surface parameters of the present invention.

After stretching in the longitudinal direction, it can be stretched in the width direction, and if necessary, re-stretched in the longitudinal direction, but even in that case, instead of mechanically nipping between rolls, The use of electrostatic nipping methods is particularly effective in obtaining the surface parameters of the present invention. Next, the stretched film is heat treated. The heat treatment conditions at that time include a temperature of 180 to 230°C, preferably 19°C.
A common method is heat treatment in the range of 0 to 220°C for 0.5 to 60 seconds.

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

(1) Average particle diameter of particles, relative standard deviation of particle diameter After etching the particle-containing film and removing the particle surface polymer, the particles were exposed and observed under a scanning electron microscope at a magnification of 20,000 times. was measured. The relative standard deviation of the particle size is the standard deviation σ (= f (Σ
(DiD)2/N)) divided by the average particle diameter (σ/
Defined in D).

(2) Particle content After adding a solvent to the polyester that dissolves the polyester but does not dissolve the particles contained therein and heating it, use an ultracentrifuge 5 manufactured by Hitachi Koki.
Centrifugation is performed using 5P-72, and the obtained particles are vacuum dried. When the particles are measured using a DSC (differential scanning calorimeter), if a dissolution peak corresponding to the polymer is observed, further solvent is added, and after heating, the centrifugation operation is performed again.

When the dissolution peak is no longer observed, the particles are considered to be precipitated particles. Normally, two centrifugation operations are sufficient.

The content is defined as the ratio (% by weight) of the thus separated particles to the total weight.

(3) Intrinsic viscosity [η] (unit: dl/g) A value calculated from the solution viscosity measured at 25°C in 0-chlorophenol using the following formula. That is, ηs, /C = [η] 10 K [η] 2 · Nikode ηSP” (solution viscosity/solvent viscosity) -1, C is the weight of dissolved polymer per 100 ml of solvent (g/10 Qml
, usually 1.2), K is the Huggins constant (assumed to be 0,343). In addition, solution viscosity and solvent viscosity were measured using an Ostwald viscometer.

(4) Glass transition point Tg, cold crystallization temperature TccDSC (
It was measured using a differential scanning calorimeter).

The measurement conditions are as follows. That is, 10 mg of sample
is set in a DSC device, melted at a temperature of 300° C. for 5 minutes, and then rapidly cooled in liquid nitrogen. This rapidly cooled sample was heated to 10°C.
The temperature was raised at a rate of /min, and the glass transition point Tg was detected. The temperature was further increased, and the exothermic peak temperature of crystallization from the glass state was defined as the cold crystallization temperature Tcc.

(5) Surface roughness parameter Ra SR1 Measured using a high-precision thin film step measuring instrument ET-10 manufactured by Kosaka Institute. R
a is the center line average roughness, and R1 is the maximum height, which is expressed as the distance between the largest peak and the deepest valley of the roughness curve. The measurement conditions were as follows, and the average value of 20 measurements was taken as the value.

・Stylus tip radius 2015μm ・Stylus load: 5mg ・Measurement length: 1nm ・Cutoff value: 0.08mm For details on the definition of each parameter, see, for example, "Measurement of Surface Roughness" by Jibu Nara. "Evaluation Method" (Sogo Technological Center, 1983).

(6) Surface roughness parameters σ, H Similarly to (5) above, regarding the film surface roughness curve, the center line direction is the X axis, and the height direction perpendicular to the X axis is the minimum value of the surface roughness curve y. The difference yi2-yif between yil and the nearest maximum value yi was defined as the protrusion height Hi. However, the protrusion height Hi was set to be 3 nm or more. The surface roughness parameters σ and H are defined for this protrusion by the following equation.

i=1 (7) Young's Modulus Measured at 25° C. and 65% relative humidity using an Instron type tensile tester in accordance with JIS-Z-1702.

(8) Refractive index, refractive index ratio Measured at 20° C. and 60% relative humidity using an Atsube refractometer using sodium D line (wavelength 589 nm) as a light source. Note that a sulfur-methylene iodide solution was used as the mounting solution. In addition, the refractive index in the thickness direction of a biaxially oriented film (denoted as A) and the refractive index in the thickness direction of a non-oriented (amorphous) film made by melt-pressing and quenching in 10°C water (denoted as B). was measured, and A/B was defined as the refractive index ratio in the thickness direction.

(9) Total reflection Raman crystallization index of the surface Ramanor U-100 manufactured by Jobin-Yvon
The total reflection Raman spectrum was measured using the 0 Raman system, and l 730 c', which is the stretching vibration of the carbonyl group, was measured.
The half width of m −' was taken as the total reflection Raman crystallization index of the surface. The measurement depth was 500 to 1.000 people from the surface, and the measurement conditions were as follows.

■Light source Argon ion laser (5145cm') ■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 the incident angle of the laser to the prism ( The angle with respect to the film thickness direction was 60'.

■Detector PM: RCA31034/Photon Coun
ting System (Hamamatsu C12
30) (supply t, 6oov) ■Measurement conditions 5LI7 1,000 μmL LASER1
00mW GATE TIME 1.0secSCAN
5PEED 12cm-'/minSAMPL
ING INTERVAL O, 2cm-'REPE
AT TIME ・6 (10) A magnetic paint having the following composition is applied to the dubbing-resistant film using a gravure roll, magnetically oriented, and dried. Furthermore, a small test calender device (steel roll/nylon roll, 5
After calendering at a temperature of near 0°C and a linear pressure of 2001g7cm, the mixture was cured at 70°C for 48 hours. The original tape was slit into 172-inch pieces to make pancakes. A length of 250 m from this pancake was assembled into a VTR cassette to make a VTR cassette tape.

(Composition of magnetic paint) ゛ Parts by weight/c
o-containing iron oxide (BET value 50ffl/g): 100
・Vinyl chloride/vinyl acetate copolymer: 10・Polyurethane elastomer: 10・Polyisocyanate 5・Lecithin
tomethyl ethyl ketone
Near 5 methyl isobutyl ketone
Near 5 Toluene Near 5
-Carbon black 2.Lauric acid: 1.5 A 100% chroma signal was recorded on this tape using a home VTR with a Shibaku TV test waveform generator (TG7/U2O5), and from the playback signal, a Shibaku test waveform generator was used. The chroma S/N was measured using a color video noise measuring device (925D/1) and given a rating of A. In addition, a tape pancake recorded with the same signal as above is printed using a magnetic field transfer video software high-speed printing system (for example, a Sony Magnescale Sprinter).
The chroma S/N of the tape after dubbing onto a pancake of the same type of tape (unrecorded) was measured in the same manner as above, and it was designated as B. Chroma S/N due to this dubbing
If the decrease (A-B) is less than 4°0 dB, dubbing resistance is good; 4. If it was 0 dB or more, it was determined that the dubbing resistance was poor.

(11) Scratch resistance In an atmosphere of 20°C and 60% relative humidity, a 172-inch wide tape film was brought into contact with a fixed shaft (surface roughness 0.2S) with an outer diameter of 6 mmφ at an angle θ = πrad, and the tension was applied. 25g and speed 500m/min (833cm/s)
After running the film 100 times, aluminum was deposited on the surface of the film, and the number and width of scratches and the state of white powder generation were observed using a differential interference microscope. Scratch resistance: 5 if there are no scratches or white powder.
Scratch resistance: 4. Scratches are less than 3 scratches/cm and almost no white powder is generated.Scratch resistance: 4. Some of the scratches are wide with 3 to 10 scratches/cm and a large amount of white powder is generated. The scratch resistance was determined to be 3. Those with scratches of 10 scratches/cm or more, large in width, and with significant white powder generation were determined to be scratch resistance: 2, and the others were determined to be scratch resistance: 1. If the scratch resistance is 5 or 4, it can be used practically without any problem.

[Example] The present invention will be explained based on Examples and Comparative Examples.

Example 1 An ethylene glycol slurry containing colloidal silica having an average particle size of 0.3 μm as particles was prepared. This slurry was polymerized by transesterification using a conventional method to obtain particle master pellets of polyethylene terephthalate containing 20% by weight of particles and having an intrinsic viscosity of 0.66.

This was then mixed with substantially particle-free polyethylene terephthalate pellets to give a particle content of 6% by weight (Polyester A). Also, by common law,
A substantially particle-free polyethylene terephthalate having an intrinsic viscosity of 0.62 was obtained (polyester B). After vacuum drying these two types of polymers at 180°C for 6 hours, polyester A was supplied to extruder 1, polyester B was supplied to extruder 2, and they were combined in a square pinol,
The mixture was discharged in a sheet form from a T-shaped nozzle through a square feed block, and cooled and solidified to produce an unstretched film with a three-layer structure. At this time, the total thickness and the thickness of the polyester layer A were adjusted by adjusting the discharge rate of each extruder. Also,
The ratio of die slit gap/unstretched film thickness was set to 10. This unstretched sheet was stretched in the longitudinal direction by an electrostatic nip at 85°C by a factor of 4°. The average drawing speed is 12
．． 000%/n+in. This -axially stretched film was stretched at a stretching speed of 4.500%/min using a stick.
It was stretched at 100°C by 4° and 5 times in the width direction. Next, this film was directly introduced into a heat treatment zone without being cooled and heat-set at 210° C. for 10 seconds to obtain a biaxially oriented laminated film having a total thickness of 15 μm and a polyester layer thickness of 0.1 μm.

Examples 2 to 5 Samples with different characteristics were made by variously changing the types of particles added, average particle size, amount added, lamination thickness, stretching conditions, and processing conditions under the conditions of Example 1. Ta.

The evaluation results of these films are summarized in Tables 1 and 2. These results show that when the surface parameters of the film are within the range of the present invention, a film having both scratch resistance and dubbing resistance can be obtained.

Comparative Example 1 An ethylene glycol slurry containing calcium carbonate having an average particle size of 0.8 μm was prepared as particles. The slurry was polymerized by transesterification using a conventional method to obtain particle master pellets of polyethylene terephthalate having an intrinsic viscosity of 0.52 and containing 10% by weight of particles. This is mixed with polyethylene terephthalate which does not contain substantially any particles, the particle content is 6% by weight, vacuum dried at 180°C for 6 hours, fed to an extruder, melt extruded at 280°C, and filtered. It was discharged in a sheet form from a T-shaped nozzle via a . This melted sheet was heated to a surface temperature of 5
It was wound around a cooling drum at 5° C. and cooled and solidified to produce an unstretched sheet.

This unstretched sheet was stretched 3.4 times in the longitudinal direction at 85°C. This stretching was performed using a difference in circumferential speed between the rolls. The average stretching speed was 10.000%/min.

This -axially stretched film was stretched at a stretching speed of 3,
The film was stretched 3.6 times in the width direction at 100°C and 000%/min. Next, this film was directly introduced into a heat treatment zone without being cooled and heat-set at 210° C. for 10 seconds to obtain a biaxially oriented polyester film having a thickness of 15 μm.

Comparative Example 2.4.5 Samples with different characteristics were made by changing the types of particles added, average particle size, amount added, stretching conditions, and processing conditions under the conditions of Comparative Example 1.

Comparative Example 3 Polyethylene terephthalate, which had an intrinsic viscosity of 0.62 and was substantially free of particles, was obtained by carrying out transesterification and polymerization using a conventional method. After vacuum drying this polymer at 180° C. for 6 hours, it was supplied to an extruder and discharged in a sheet form from a T-shaped nozzle. This molten sheet was wound around a cooling drum with a surface temperature of 52°C, and cooled and solidified to produce an unstretched film.

This unstretched sheet was stretched 3.6 times in the longitudinal direction at 85°C. Thereafter, colloidal silica having an average particle size of 0.3 μm was coated on the -axially stretched film together with a water-soluble polyester binder so that the coating thickness was 0.3 μm.

This coated uniaxially stretched film was stretched 3.8 times in the width direction at a stretching rate of 3.000%/min and 100° C. using a stenter. Next, this film is directly led to a heat treatment zone without cooling, and heated to 210°C.
The film was heat-set for 10 seconds to obtain a biaxially oriented coating film with a total thickness of 15 μm.

Comparative Example 6 Samples with different characteristics were made by changing the types of particles added, average particle size, amount added, type of binder, stretching conditions, and processing conditions under the conditions of Comparative Example 3.

The evaluation results of these films are summarized in Tables 1 and 2. From these results, it can be seen that if the surface parameters of the film are not within the range of the present invention, a film having both scratch resistance and dubbing resistance cannot be obtained.

[Effects of the Invention] Since the present invention sets the surface roughness parameter within a specific range, a film with excellent scratch resistance and dubbing resistance can be obtained. Furthermore, this will also be compatible with the wear resistance and high output required to improve the quality of magnetic recording media in the future.

The film of the present invention can be processed into various magnetic recording media such as video tapes, audio tapes, floppy disks, etc. by providing a magnetic layer on one or both sides thereof. The film of the present invention is useful for magnetic recording media, but it can also be used in other applications where abrasion resistance and smoothness are issues, such as graphics, stamping foils, electrical insulation materials, dielectric materials for capacitors, and packaging. So, it can be used effectively.

Claims (4)

[Claims] (1) Surface roughness parameter Ri/Ra on at least one side
8.0 or less. (2) Surface roughness parameter σ/H on at least one side is 0
．． A biaxially oriented polyester film characterized by having a molecular weight of 8 or less. (3) Total reflection Raman crystallization index of at least one side is 15
The biaxially oriented polyester film according to claim 1 or 2, characterized in that the film has a diameter of cm^-^1 or more. (4) At least one side of the polyester film is coated with 0.2 to 5 μm of polyester having an intrinsic viscosity of 0.56 to 0.8 and containing particles with an average particle size of 0.02 to 1.0 μm.
4. The method for producing a biaxially oriented polyester film according to claim 1, wherein after lamination, biaxial stretching is carried out so that the product of longitudinal and lateral stretching ratios is 10 times or more.