JPH048458B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a polyester film, and more particularly to a polyester film suitable mainly for magnetic tapes and magnetic disks. [Prior art] Polyester, which is used industrially today,
In particular, biaxially stretched polyethylene terephthalate films have excellent properties and are widely used in industry. However, in films for magnetic tapes and magnetic disks, the production of which has been increasing rapidly in recent years, the abrasion resistance between the polyester film and the guide pin, head, or roll portion is poor, which often poses a problem in practice. For this reason, attempts have been made to improve the abrasion resistance by incorporating specific inorganic or organic additives into polyester, and by specifying the diameter and amount of the additive particles, as well as the surface roughness of the film after addition. [Problems to be Solved by the Invention] However, the conventional polyester film described above has the following problems. Even if the film has excellent slipperiness, that is, the slipperiness between the films, the tape running property, that is, the slipping property between the metal head and the tape, is poor, and when the tape is repeatedly run, the running torque increases and the running speed decreases. Eventually, the tape will stop running. Even if the running properties of the film appear to be excellent, white powdery substances may fall off due to wear on the film head, and signals such as audio and images, which is a fatal defect in audio and video tapes, may be removed. cause disturbance. Furthermore, even if the running properties are excellent at room temperature, the running properties deteriorate under high temperature and high humidity conditions (for example, 40°C, 95RH%). In the case of films with excellent slipperiness, the wound films tend to slip against each other, resulting in uneven film end surfaces and so-called stray winding. The object of the present invention is to solve these problems and provide an excellent polyester film free from the above-mentioned drawbacks. [Means for Solving the Problems] The present invention provides a polyester film containing 0.001 to 0.03% by weight of inert particles with an average particle size of 500 to 1500 mμ, wherein the inert particles are used as primary particles.
A polyester film characterized in that it is an aggregate of particles having an average particle size of 10 to 100 mμ, and the surface layer crystallization coefficient of the polyester film is in the range of 0.5 to 0.7 (provided that the inert particles are silicon oxide (excluding cases consisting of), The polyester in the present invention is a polymer having ester bonds obtained by condensation polymerization from dicarboxylic acid and diol, and dicarboxylic acid components include terephthalic acid, phthalic acid, isophthalic acid, adipic acid, sebacic acid, naphthalene dicarboxylic acid, Diol components include ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, cyclohexanedimethanol, dihydroxycyclohexane, resorcinol, hydroquinone, dihydroxynaphthalene, polyethylene glycol, etc. Polyesters can also be obtained from oxyacids such as hydroxyethoxybenzoic acid, p-oxybenzoic acid, and the like. The intrinsic viscosity of the polyester is preferably 0.4 or more, preferably in the range of 0.6 to 1.0. Polyesters suitable for the present invention include polyethylene terephthalate. Of course, optional additives may be added to the polyester, such as slip agents, heat stabilizers, antiblocking agents, antioxidants, colorants, antistatic agents,
It may also contain an ultraviolet absorber, a viscosity increasing (reducing) agent, etc. The inert particles contained in the polyester are aggregates of particles in which the primary particles have an average particle size of 10 to 100 mμ, preferably 20 to 80 mμ, and the average particle size is 500 to 1500 mμ, preferably 700 to 1200 mμ. be. If the average particle size of the primary particles is less than 10 mμ, the cohesive force of the aggregates will be weak, and the aggregates will easily disintegrate due to the shearing force in the polymer manufacturing and film forming processes. Difficult to obtain agglomeration. Furthermore, if the primary particle size exceeds 100 mμ, particles that fall off or peel off during film running will cause disturbances in signals such as audio and images, and a dropout phenomenon, which is a fatal defect in magnetic recording. Furthermore, if the average particle size of the aggregates is less than 500 mμ, not only will the slipperiness and running characteristics of the film deteriorate, but also the roll-like appearance of the film, that is, the occurrence of irregularities in the slit end face, wrinkles, and depressions. becomes more likely to occur. In addition, the average particle size of the aggregates is
If it exceeds 1500 mμ, the surface smoothness of the polyester film will deteriorate, and not only will dropouts due to spacing loss and electromagnetic conversion characteristics deteriorate.
Dropout is likely to occur due to particles falling off the surface of the polyester film due to wear of the head or the like. Furthermore, the inert particles used in the present invention must be aggregated particles. In the case of uniform particles rather than agglomerated particles, the stress applied to the film during film running causes the particles to peel off or fall off the film in their original shape and size, so when used as a base film for magnetic recording, audio and Not only does it cause signal disturbances such as images and dropout phenomenon,
Driving performance also deteriorates significantly. However,
When agglomerated particles of a specific particle size as in the present invention are used, when stress is applied to the film due to friction, running, etc., some of the agglomerated particles with unevenness on the film surface may cleave or collapse. Alternatively, it may fall off or peel off from the surface layer of the film due to physical atomization effects such as destruction or crushing. The thickness of the surface layer particles varies depending on the type of particles added, surface treatment conditions, and stretching conditions, but it is approximately 1/1/2 of the added particles.
The size is about 20 to 1/60. Particles that fall off in this way often adhere to the surface layer of the film singly or in multiple layers, but their thickness is
Since it is small, 1/20 to 1/40 of the added particles, it cannot reach a height of 500 mμ or more, preferably 250 mμ or more, which would cause dropout. Therefore, dropout does not occur due to dropout of surface particles, but rather, dropout occurs. The fine particles greatly improve the running properties of tapes, etc. As described above, it is not preferable for the agglomerated particles of the present invention to have too strong or too weak a cohesive force. If it is too strong, when an external force is applied to the film, a part of the aggregated particles will not fall off from the surface layer of the film properly, but the entire aggregated particles will fall off, leading to defects such as dropouts, or conversely, the cohesive force will be reduced. If it is too weak, particles with an average particle diameter of 500 to 1500 mμ cannot be obtained as aggregated particles, and as a result, running properties etc. are significantly reduced. As a measure of cohesive force, aggregated particles with a media such as glass beads are dispersed in a dispersion liquid such as ethylene glycol, coarse protrusions are eliminated by applying high shear force, and after the particles are uniformly dispersed, a sedimentation method is applied. Average particle size (CAPA) measured at
is 2 to 10 times the primary particle size after treatment, preferably 3 to 10 times the primary particle size.
It is preferable that the agglomerated particles of the present invention be in a range of 8 times. Typical agglomerated particles include TiO ₂ , ZrO ₂ , and CaCO ₃ dispersed in a jet agitator.
and so on. Of course, in addition to the aggregated particles, particles with an average particle diameter of preferably 500 mμ or less, more preferably 150 to 400 mμ
It is preferable to include other uniform particles having an average particle size of 0.05 to 0.5% by weight, such as SiO ₂ or TiO ₂ , to improve slipperiness, runnability, and winding shape, and the effects of the present invention can be improved. This makes it even more noticeable. The inert aggregate particles are present in an amount of 0.001 to 0.03% by weight, preferably 0.005 to 0.03% by weight based on the polyester film.
Add so that the content is 0.02% by weight. The content is
If the content is less than 0.001% by weight, slipperiness, runnability, and winding appearance will be poor, and if the content exceeds 0.03% by weight,
The smoothness of the polyester film decreases, white powder particles tend to fall off the surface of the polyester film due to abrasion, and not only does it have poor abrasion resistance, but many of the fallen particles agglomerate and grow. This will cause dropout. Surface layer crystallization coefficient of the polyester film of the present invention
Ax must be in the range 0.50-0.70, preferably 0.55-0.67. This is because if the value of Ax is less than 0.50, the slipperiness between films and the running property between metal and film will deteriorate.On the other hand, if the value of Ax exceeds 0.7, even if the added particles are specific agglomerated particles. However, when the film is running, particles near the surface layer with the same shape and size fall off or peel off from the film, and the dropped particles not only cause a dropout phenomenon, but also significantly deteriorate running properties. This is to do so. Furthermore, the density d of the film of the present invention is 1.385 to 1.398.
A relatively low density material (g/cm ³ ) is preferable. This is because excellent running performance without dropouts, which is an effect of the present invention, can be obtained. Further, the effect of the present invention is also noticeable when the plane orientation coefficient is in the range of 0.130 to 0.170. Next, the method for manufacturing the polyester film of the present invention will be explained. A polyester represented by polyethylene terephthalate, polyethylene naphthalate, etc. is obtained by a polycondensation reaction from a dicarboxylic acid component and a diol component by a conventional transesterification method (DMT method) or a direct polymerization method. Inert particles of a specific particle size can be added before, during, or after the polyester condensation reaction, but in particular, they can be added evenly as a slurry in a diol component such as ethylene glycol before the polycondensation reaction. It is preferable to add the fine particles in order to uniformly disperse the fine particles in the polyester. At this time, if necessary, appropriate dispersion methods may be used to eliminate coarse protrusions and make the particle size distribution uniform.
If too strong a dispersion method, such as media dispersion, is used in combination, the aggregated particles will be separated and dispersed into primary particles, which is not preferable. Of course, the above-mentioned additives may be kneaded into polyester to form a master chip, and diluted with other polyester so that the content in the film becomes 0.001 to 0.03% by weight. Next, the polyester is sufficiently dried, and melt extrusion is performed in such a way that substantially no hydrolysis reaction or thermal decomposition reaction proceeds during melt extrusion, and then the molten polymer is discharged from a die and cast. In the case of the present invention, it is particularly preferable to obtain a cast sheet by dropping the sheet onto an electrically insulated cast drum charged with an electrostatic charge and cooling and solidifying the sheet in the charged state. Next, the sheet is stretched 3 to 8 times in one or multiple stages at 85 to 130°C in the longitudinal direction, and then stretched at 80°C in the width direction.
Stretch 3-6 times at ~200°C and heat treat at 100-240°C. If necessary, heat treatment may be performed again after stretching in the longitudinal direction and/or width direction. It is important to form the polyester film so that the surface layer crystallization coefficient is within a specific range. For this reason, especially as film forming conditions, when using roll-type longitudinal stretching, the longitudinal stretching should not be completed with cooling rolls, but using nip-type heating rolls that are maintained at a temperature higher than the glass transition temperature Tg of polyester. It is preferable to employ a special casting method such as that described above. Further, the effect of the present invention is also enhanced by a treatment in which only the surface layer of the obtained film is heated, such as flame treatment or corona discharge treatment. Also, the thickness of the polyester film is 4~
125 mμ, preferably about 5 to 80 mμ is often used. [Applications] The thus obtained polyester film of the present invention can be used as a base film for magnetic tapes and magnetic disks, and can be used for magnetic recording without dropouts with excellent runnability, especially runnability under high temperature and high humidity, and abrasion resistance. It is preferable to use it as a base film. [Effects of the Invention] The present invention allows polyester to contain a specific amount of specific inert agglomerates and particles with a specific particle size, and furthermore, limits the surface layer crystallization coefficient of the polyester film to a specific range, thereby improving the runnability of the polyester film. ,
In particular, it has excellent runnability under high temperature and high humidity conditions, and is also excellent in abrasion resistance.As a result, the film not only has extremely low dropouts but also has excellent slitting suitability. [Measurement method and evaluation method of characteristics] The measurement method and evaluation method related to the present invention are as follows. Slip property: according to the method of ASTM-1894-63,
Static friction coefficient (μs) using a slip tester
and the coefficient of dynamic friction (μd) were measured. Generally, the range in which a film is considered to have excellent slipperiness is 1.0 or less in μs and 0.8 or less in μd. Slip property (μs) 1.6 or more × 1.0 to less than 1.6 △ 0.7 to less than 1.0 〇 Less than 0.7 ◎ Running durability Using a tape running property tester model TBT-300 (manufactured by Yokohama System Research Institute Co., Ltd.) at 25℃,
Repeatedly run 100 times in an atmosphere of 50RH% and 40°C and 85RH%, find the initial μk and μk after 100 times repeatedly using the past formula, and calculate the difference between these two values (μk after 100 times repeatedly run - initial μk ) represents running durability. μk=0.733log(T ₁ /T ₀ ) Here, T ₀ is the inlet tension and T ₁ is the outlet tension.
The guide diameter is 8mmφ, and the guide material is
SUS27 (surface roughness 0.2S), wrapping angle 180°, running speed 3.3cm/sec. Running durability (wear resistance) (difference between μk after 100 repetitions and initial μk) Less than 0.03 ◎ 0.03 to less than 0.06 〇0.06 to less than 1.2 △ 1.2 or more × Surface roughness: Ra (μm) Stylus type surface Shown as measured values with a roughness meter (cutoff value 0.25 mm, measurement length 4 mm, JIS-B
-0601). Surface roughness Ra (μm) 0.10 or more × 0.05 to less than 0.10 △ 0.01 to less than 0.05 〇 Less than 0.01 ◎ Amount of white powder (evaluation method that indicates wear resistance) Tape runability tester TBT-300 (manufactured by Yokohama System Research Institute Co., Ltd.) ), 25℃, 50RH
After running 300 times in an atmosphere of 300%, the white shaving powder (white powder) adhering to the guide part was visually determined. Here, the guide diameter is 8mmφ, the guide material is SUS27 (surface roughness 0.2S), and the wrapping angle is
180°, tape running speed is 3.3 cm/sec. Criteria for determining the amount of white powder: Very little ◎ Little 〇 Slightly much △ Very much × Average particle size: Using optical observation, mark the area around the protrusions caused by specific particles in the film with the tip of a disassembly needle, and then slide the area. Fix it on the glass. In a plasma reactor device (for example, Yamato Kagaku PR-503 model), the particles that form the protrusions are ashed at a low temperature until they are exposed from within the film. Peel off the attached particles with double-sided adhesive tape and fix them on the sample stage with the back side of the particles exposed. Observe the sample with FE-SEM and use an image analyzer (e.g.
QTM900: Made by Cambridge Instrument)
The number average diameter φn obtained by the following numerical processing at 10 or more observation points is defined as the average particle diameter. Σdn/Σn=φn where n is the number and d is the actual hole diameter. The diameter of the coarse particles in the film is determined by applying a plasma reactor to the location where the coarse protrusions are present, removing the polyester on the surface layer, taking out only the contained particles, and using a scanning electron microscope. To judge the slit end face, cut a tape-like film to a film width of 8 mm, wind it to a length of 3,000 m around a 3-inch PVC core, and check that both end faces are completely uniform with no irregularities.
A case where there is a disturbance within 0.5 mm is marked as ○, a case where the end face is not aligned at all is marked as ×, and a mark in between is marked as △. The surface layer crystallization coefficient Ax is calculated using FT-IR.
Measure the ATR spectrum in the width direction. The incident angle of the light beam was set to 45° with respect to the film surface, and the wave number was 1350 to 1400 cm ^-1 with 300 integrations.
The absorbance A of the crystal band at 1386 chi and the amorphous band at 1370 chi is calculated by enlarging the area of , and the ratio (A ₁₃₈₆ /A ₁₃₇₀ ) is calculated as the surface crystallization coefficient.
Let it be Ax. Density is determined according to ASTM D1505 using the density gradient tube method at 23°C (in g/cm ³ ). Intrinsic viscosity [η] is measured according to ASTM D1601 (unit: dl). [Example] In order to clarify the effects of the present invention, examples will be described below. Example 1 Agglomerated particles of titanium dioxide TiO ₂ with a primary particle size of 50 mμ and colloidal silica (uniform particles with an average particle size of 200 mμ) were dispersed in ethylene glycol and uniformly dispersed using a jet agitator dispersion method to form particles with a particle size of 6μ or less. The ethylene glycol solution from which the grains had been removed and dimethyl terephthalate were mixed with lithium acetate as a transesterification reaction catalyst, and the mixture was heated to an elevated temperature to perform a transesterification reaction by removing methanol. Next, antimony trioxide was added to the reaction product together with phosphoric acid and triethyl phosphate, and the polymerization was completed according to a conventional method to obtain polyethylene terephthalate having an intrinsic viscosity [η] of 0.65. The polyethylene terephthalate was vacuum dried at 180°C for 2 hours, then supplied to an extruder, melted at 285°C, and discharged from a T-die nozzle. At this time, it was cooled in close contact with a casting drum (freon gas was used as a refrigerant) that was electrically insulated and to which a high voltage was applied. That is, the melt coat was cooled to the glass transition temperature of polyethylene terephthalate, 70° C. or lower, while it remained charged. The cast sheet thus obtained was stretched 1.8 times at 125°C between two pairs of nipped heating rolls, then 3.1 times at 90°C in the same direction, and then stretched at 95°C in the width direction.
After stretching 4 times with
While also relaxing 2% in the width direction of the
Heat set for seconds. The quality of the resulting polyethylene terephthalate film with a thickness of 9 μm was first in the class.
As shown in the table. As shown in Table 1, the product of the present invention has excellent slipperiness, running properties, and surface smoothness, and also has no coarse particles and hardly scratches when running.
Therefore, it can be seen that the film has no dropouts.

【table】

[Table] Comparative Example 1 In place of the agglomerated titanium dioxide particles used in Example 1, uniform particles (not agglomerated particles) with the same composition and average particle diameter of 800 mμ were used, but the thickness was determined in exactly the same manner as in Example 1. A polyethylene terephthalate film with a diameter of 9 μm was obtained. The evaluation results are shown in Table 2. In this way, even if the average particle size is the same, if uniform particles are used instead of aggregated particles, the particles will fall off during tape running, not only reducing running durability but also causing dropouts. It turns out that it cannot be used as a base film for magnetic recording. Comparative Example 2 The casting method used in Example 1 was changed, and an electrostatic charge was applied to the molten sheet discharged from the T-die die from a tungsten wire placed between the die and the casting drum to charge the molten sheet. After that, it was tightly solidified on a grounded casting drum (using water as a refrigerant). Furthermore, the longitudinal direction stretching method is heated to 50℃.
The method was changed to a method in which the process is carried out between a cooling roll that has been cooled down to a certain temperature. A polyethylene terephthalate film having a thickness of 9 μm was obtained in exactly the same manner as in Example 1, except that the casting method and longitudinal stretching method were changed as described above. The results are shown in Table 2. In this way, it can be seen that even if the additives are the same, the surface layer crystallization coefficient Ax changes depending on the film forming conditions, resulting in differences in running durability, dropout, etc. Examples 2 to 5, Comparative Examples 3 to 4 Biaxially stretched films were formed in the same manner as in Example 1, except that the amount of agglomerated titanium dioxide used in Example 1 was changed as shown in Table 3. did. From Table 3, it can be seen that the addition amount is preferably in the range of 0.001 to 0.03% by weight, preferably 0.005 to 0.02% by weight for the present invention. Example 6 Biaxially stretched polyethylene terephthalate with a thickness of 9 μm was produced in the same manner as in Example 1, except that zirconia oxide ZrO ₂ with a primary particle size of 20 μm was used instead of TiO ₂ with a primary particle size of 50 μm used in Example 1. I got the film. The thus obtained agglomerated ZrO ₂ contained 0.001% by weight, and its average particle size was 950 mμ. Surface layer crystallization coefficient Ax is 0.60, density is 1.395g/cm ³ ,
ΔN was 0.148, and all properties such as slipperiness, running durability, surface roughness, amount of white powder, and slit end surface were excellent.

【table】

【table】

Claims (1)

[Claims] 1 Inert particles with an average particle size of 500 to 1500 mμ are 0.001
A polyester film containing ~0.03% by weight, wherein the inert particles contain 10~0.03% by weight as primary particles.
It is an aggregate of particles with an average particle size of 100 mμ,
and the surface layer crystallization coefficient of the polyester film is
A polyester film characterized in that the inert particles are in the range of 0.5 to 0.7 (except when the inert particles are made of silicon oxide).