JPH07241973A - Biaxially oriented laminated polyester film - Google Patents

Abstract

PURPOSE:To reduce the fluctuations of the surface characteristics in the lateral direction of a biaxially oriented laminated polyester film suitable as a base film of a video tape or the like by specifying the thickness and surface roughness of the surface layer of the film and suppressing the fluctuations in the laterial direction of the film to a specific value or less. CONSTITUTION:When the thickness of the surface layer of a laminated film changes, the surface roughness thereof changes with the change of the thickness of the surface layer even if the surface layer has the same lubricant compsn. When this phenomenon is adapted in proportion to the difference between the refractive indexes in the longitudinal and lateral directions of the film or the magnitude of an angle of orientation, the fluctuations of the surface roughness in the laterial direction of the film can be reduced. Herein, the thickness of at least one surface layer is set to 0.02-3mum and the surface roughness Ra thereof is set to 3-40mum. Further, the fluctuations in the lateral direction of the film are suppressed to 5%/500mm or less. If necessary, inert particles (lubricant) of silicon dioxide. alumina or silicate are added to the surface layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially oriented laminated polyester film, and more specifically, at least one surface layer has uniform surface roughness, slipperiness, abrasion resistance, scratch resistance and the like in the width direction. The present invention relates to a biaxially oriented laminated polyester film.

[0002]

2. Description of the Related Art Biaxially oriented polyester films are used in many applications such as magnetic tapes, electricity, photography, metallization and packaging due to their excellent properties. In particular, because of its high strength and elastic modulus, it is widely used as a base film for magnetic recording media such as video tapes, audio tapes, computer tapes and floppy disks.

In these fields of application, high density recording,
The demand for higher quality is increasing, and along with this, the demand for a flat surface on the polyester film that is the base is increasing.

However, when the surface of the film becomes flat, the coefficient of friction of the film becomes high, for example, in magnetic tape applications, causing problems such as poor running and easy scratching. In addition, when the film surface becomes flat, the film winding shape during the film winding process during film production remarkably deteriorates, making it difficult to obtain a film roll with a good winding shape. Accordingly, it is necessary to increase the film winding speed and to widen the film. However, with the increase in speed and width, it becomes difficult to obtain a film roll having a better winding shape.

As described above, the flattening of the film surface needs to solve the problems associated with it at the same time.

Therefore, a laminated film having different front and back surfaces having different surface roughnesses, that is, a front and back different area layer film in which one surface (front surface) is flat and the other surface (rear surface) is rough is proposed. There is. This film is effective when the required flatness is required only on one side of the film and the other side may be rough. For example, in the case of a base film of a magnetic tape, if a magnetic layer is provided on the front surface of the film and a rough surface is used as a running surface, slippage is caused from the viewpoint of flatness and film running property in terms of improvement of electromagnetic conversion characteristics. It is also possible to obtain a better base film for magnetic tape. However, in recent years, the base film is required to be flatter than the surface roughness of the rough surface, and is becoming more and more flat.

Under such a circumstance, variations in the film surface roughness become apparent as differences in the film characteristics, and particularly variations in the surface roughness in the film width direction cause differences in the ease of winding. Is coming.

For example, in the production of a magnetic tape, which is one of the main uses of polyester film, a long polyester film having a wide width (for example, 300 to 1500 mm width) is coated with a magnetic layer and subjected to calendering. After obtaining a wide web, slit into a tape width of, for example, 8 mm or 1/2 inch, and tens of tapes are simultaneously wound into a length of several thousand meters to several hundred meters to form a pancake. At this time, if there is a difference in surface roughness in the width direction of the wide polyester film of the base, slit tapes having different surface roughness will be obtained. And if you wind up the slit product under conditions that match the surface roughness of the flat part,
Since the base surface of the slit product in the rough part is more slippery (excellent in running performance) than the base surface of the slit product in the flat part, the end face deviation of the slit product (pancake) in the rough part is likely to occur, resulting in winding. The appearance becomes worse and the product yield is reduced. Furthermore, if the edge shift is significant, the pancake may collapse during the process, and the process may have to be stopped. On the other hand, if the coil is wound under conditions that match the surface roughness of the rough part, the slit product of the rough part can be wound neatly, but the slit product of the flat part is inferior to the rough part in terms of slipperiness (running property). (Hump-shaped protrusions) occur, or the winding shape becomes bad (the winding does not become a clean circular shape, but it is in a slightly angular state). I will lower it.

If the surface roughness is different in the width direction of the wide film as described above, it becomes difficult to obtain the same good winding shape in all slit products as described above.

[0010]

DISCLOSURE OF THE INVENTION The present inventor has studied the variation of the surface roughness in the width direction of the film. As a result, when the film surface roughness is transversely stretched by the tenter method, the lubricant is uniformly distributed in the film. It has been found that even if it is contained, it tends to become flatter as it is closer to the side end portion compared to the center portion of the tenter. The reason for this is considered as follows.

Polyester film is generally produced by a sequential biaxial stretching method, and is longitudinal-horizontal, longitudinal-horizontal-
Stretched in multiple stages such as vertical, vertical-horizontal-vertical-horizontal, horizontal-vertical, vertical-vertical-horizontal, etc., but in these processes,
The transverse stretching step is usually performed by a tenter method. The tenter method is a method in which a film is guided to a tenter, grips both side ends with a clip-shaped one, and laterally stretches to a predetermined magnification by laterally expanding clips at both ends during conveyance.

In this tenter method, a contraction stress acts on the conveyed film in the longitudinal direction along with the lateral stretching during the lateral stretching, but both side ends gripped by the clips and the restraining force by the clips are relatively weak. There is a difference in the action of the shrinkage stress between the part and the part, and the progress of the molecular orientation is different. This phenomenon is called Boeing, but compared to both ends,
This is due to the fact that the central part is delayed with respect to the tenter flow direction. This means that if you draw a straight line in the lateral direction on the surface of the film before entering the tenter, this straight line is deformed in the tenter and becomes a concave line on the film leaving the tenter. I also understand. It is considered that the difference in the surface orientation and other characteristics in the tenter width direction is caused by the difference in the molecular orientation progress due to the bowing.

The present inventor further studied to reduce or eliminate the surface characteristic variation in the film width direction,
When the layer thickness of the surface layer in the laminated film changes, the surface roughness of the surface layer of the same lubricant composition changes with this change, and this phenomenon is caused by the change in the refractive index in the longitudinal and transverse directions. When applied in proportion to the size of the difference and orientation angle,
The inventors have found that it is possible to reduce the variation in surface roughness in the film width direction, and have reached the present invention.

[0014]

That is, according to the present invention, at least one surface layer has a thickness of 0.02 μm or more and 3 μm or less and a surface roughness Ra of the surface layer of 3 to 40 n.
The biaxially oriented laminated polyester film is characterized in that it is m and the variation in the film width direction is 5% / 500 mm or less.

The polyester in the present invention is a polyester having an aromatic dicarboxylic acid as a main acid component and an aliphatic glycol as a main glycol component. Such polyesters are substantially linear and have film forming properties, especially film formation by melt molding. Examples of the aromatic dicarboxylic acid include terephthalic acid, naphthalenedicarboxylic acid, isophthalic acid, diphenoxyethanedicarboxylic acid, diphenyldicarboxylic acid, diphenyletherdicarboxylic acid, diphenylsulfonedicarboxylic acid, diphenylketonedicarboxylic acid and anthracenedicarboxylic acid. You can Examples of the aliphatic glycol include polymethylene glycol having 2 to 10 carbon atoms such as ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol and decamethylene glycol, and alicyclic compounds such as cyclohexanedimethanol. Examples thereof include diols.

In the present invention, a polyester containing alkylene terephthalate and / or alkylene naphthalate as a main constituent is preferably used as the polyester.

Among such polyesters, not only polyethylene terephthalate and polyethylene-2,6-naphthalate but, for example, 80 mol% or more of all dicarboxylic acid components are terephthalic acid and / or 2,6-
It is a naphthalene dicarboxylic acid and contains 8 of all glycol components.
A copolymer in which 0 mol% or more is ethylene glycol is preferable. 20 mol% or less of the total acid component can be the above-mentioned aromatic dicarboxylic acids other than terephthalic acid and / or 2,6-naphthalenedicarboxylic acid, and aliphatic dicarboxylic acids such as adipic acid and sebacic acid. An alicyclic dicarboxylic acid such as cyclohexane-1,4-dicarboxylic acid can be used. Further, 20 mol% or less of the total glycol component may be the above-mentioned glycol other than ethylene glycol, and aromatic diols such as hydroquinone, resorcin, and 2,2-bis (4-hydroxyphenyl) propane; 1 , 4-
An aliphatic diol having an aromatic ring such as dihydroxydimethylbenzene; polyalkylene glycol (polyoxyalkylene glycol) such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol and the like can also be used.

Further, the polyester in the present invention includes
Aromatic oxyacids such as hydroxybenzoic acid, ω-
Those in which a component derived from an oxycarboxylic acid such as an aliphatic oxyacid such as hydroxycaproic acid is copolymerized or bonded with 20 mol% or less based on the total amount of the dicarboxylic acid component and the oxycarboxylic acid component are also included.

Further, in the polyester of the present invention,
Amounts in a range that is substantially linear, eg, 2 based on total acid component
It also includes a copolymerized polyfunctional polycarboxylic acid or polyhydroxy compound such as trimellitic acid and pentaerythritol in an amount of not more than mol%.

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

In the present invention, the biaxially oriented laminated polyester film is composed of at least two layers, but may be three layers or more as long as the object of the present invention is not impaired.
And the polyester of each layer may be the same or different.

The biaxially oriented laminated polyester film of the present invention has a surface roughness Ra of at least one surface layer of 3 or less.
-40 nm. If this surface roughness Ra is too small,
When winding the film on a roll, bumps (hump-shaped protrusions) are likely to occur even if the winding conditions are adjusted.
When it is larger than nm, the end face is apt to be displaced when wound on a roll, which is not preferable. From these points, the surface roughness Ra is preferably 4 nm or more, more preferably 5 nm or more, and 35 nm or less, further 25 nm.
It is particularly preferable that the thickness is 15 nm or less.

The surface layer contains one or more kinds of inert particles (lubricant). In addition, the other surface layer (base layer) and the inner layer (core layer) of three or more layers may also contain inert particles. In this case, it is preferable that the base layer or the inner layer (core layer) under the surface layer contains inert particles so that the surface roughness Ra of the surface layer becomes lower when the surface is formed by this layer. . Furthermore, the surface roughness R of the base layer and the inner layer
a is 2 nm or more from the surface roughness Ra of the surface layer, especially 4 n
It is preferably lower than m.

Examples of such inert particles include (1) silicon dioxide (including hydrate, diatomaceous earth, silica sand, quartz, etc.);
(2) Alumina (including crystal forms: α, β, γ, δ, θ, κ, etc.); (3) Silicate containing 30% by weight or more of SiO ₂ (for example, amorphous or crystalline clay) Minerals, aluminosilicates (including fired products and hydrates), warm asbestos,
Zircon, fly ash, etc.); (4) Mg, Zn, Z
r and Ti oxides; (5) Ca and Ba sulfates; (6) Li, Ba, and Ca phosphates (including monohydrogen and dihydrogen salts); (7) Li, Na , And K
Benzoates of (8) Ca, Ba, Zn, and terephthalates of Mn; (9) Mg, Ca, Ba, Zn, C
Titanates of d, Pb, Sr, Mn, Fe, Co, and Ni; (10) Chromates of Ba and Pb; (1
1) carbon (eg carbon black, graphite etc.); (12) glass (eg glass powder, glass beads etc.); (13) Mg carbonate; (14) Ca carbonate;
(15) Fluorite; (16) ZnS; and (17) Heat-resistant polymer particles (for example, silicone resin particles, crosslinked acrylic particles, crosslinked polystyrene particles, crosslinked polyester particles, Teflon particles, polyimide particles, melamine resin particles, etc.). Etc. are illustrated.

The average particle size of the inert particles is 0.05 to 3 μm.
m, further 0.08 to 0.9 μm, especially 0.09 to 0.
It is preferably 49 μm. The content of the inert particles is preferably 0.01% by weight or more, more preferably 0.1% by weight or more, particularly preferably 0.6% by weight or more, and 8% by weight or less, further 3% by weight or less, particularly 0.9% by weight
The following is preferable.

In the biaxially oriented laminated polyester film according to the present invention, the variation of the surface roughness Ra in the film width direction needs to be 5% / 500 mm or less.
When this variation is larger than 5% / 500 mm, when the slit product is wound under the winding condition suitable for the one having a large surface roughness Ra of the wide film, bumps are generated in the slit product having a small surface roughness Ra. On the other hand, if the slit product is wound under the winding condition suitable for the one having a small surface roughness Ra of the wide film, wrinkles are easily formed in the slit product having a large surface roughness Ra, and the winding hardness is high. Since it becomes soft, the end face is likely to be displaced, and the winding shape is not good in both cases, which is not preferable. From these points, the fluctuation of the surface roughness Ra in the film width direction is preferably 3% / 500 mm or less, and more preferably 1% / 500 mm or less.

In the biaxially oriented laminated polyester film of the present invention, the thickness of at least one surface layer must be 0.02 μm or more and 3 μm or less. When the thickness of the surface layer is less than 0.02 μm, the surface roughness Ra changes greatly even if the thickness of the layer slightly changes.
The variation in surface roughness Ra becomes large, the number of protrusions due to the inert particles decreases, and the slipperiness deteriorates, which is not preferable. If the surface roughness Ra is to be roughened, the amount of the inert particles added becomes too large relative to the layer thickness, and it becomes easy to scrape during traveling or the like. On the other hand, when the thickness is more than 3 μm, the change of the surface roughness Ra when the thickness of the surface layer is changed in the width direction becomes too small, and it becomes difficult to make the surface roughness Ra uniform in the width direction, which is not preferable. . From these points, the thickness of the surface layer is preferably 0.05 μm or more, more preferably 0.07 μm or more, especially 0.2 μm or more, and less than 2.5 μm, further 2 μm or less, especially 1 μm or less, It is preferably 0.45 μm or less.

The thickness of the surface layer varies in the width direction of the film and has a refractive index (n _MD ) in the longitudinal direction and a refractive index (n n in the width direction).
_TD ) difference (birefringence: Δn = n _MD −n _TD ) increases, and in particular the thickness t _{A of the} minimum birefringence portion (A portion) of the surface layer and the maximum birefringence portion. (B part) thickness t
It is preferable that _B and the following expression 1 are satisfied.

[0029]

[Equation 4]

(Where, t _A : thickness of the surface layer of the A portion (μm) t _B : thickness of the surface layer of the B portion (μm) Δn _A : vertical refractive index n _MD and widthwise refractive index n of the A portion Difference from _TD (birefringence: n _MD −n _TD ) Δn _B : Difference between longitudinal refractive index n _MD and widthwise refractive index n _{TD of} part B (birefringence: n _MD −n _TD ) L: (Distance in the film width direction from part A to part B (m) D: average particle size (μm) of the lubricant contained in the surface layer.)

The birefringence index (Δn = n _MD −
n _TD), the vertical direction refraction index (n _MD) in the width direction refractive index (n _TD) when greater than a positive value, whereas when the width direction refractive index (n _TD) less than a negative value . The above equation 1 is also applied when it takes a negative value.

(T_B-T_A) / T_AIs [(Δn_B-Δn
_A) / 2 × D] × √L, the width of the film
It is not possible to compensate for changes in physical properties with changes in surface layer thickness.
It becomes sufficient and is not preferable. From this point, (t_B−
t_A) / T_AIs [(Δn_B-Δn _A) / D] × √L or more
Is more preferable, and [(Δn_B-Δn_A) /0.75×
D] × √L or more is more preferable, and [(Δn_B-Δ
n_A) /0.5×D] × √L or more is particularly preferable. other
One, (t_B-T_A) / T_AIs [20 (Δn_B-Δn_A)
/ D] × √L, the surface in the film width direction
The layer thickness difference becomes too large, which causes
It is not preferable because the uniformity of surface roughness deteriorates and
The change in the thickness ratio with other layers is large, and the thickness unevenness does not deteriorate.
Less preferred. From this point, (t_B-T_A) / T_AIs
[10 (Δn_B-Δn_A) / D] × √L or less is preferred
, [5 (Δn_B-Δn_A) / D] × √L or less
preferable.

In the above formula 1, the A portion and the B portion are usually separated from each other in the same film in the film width direction (direction perpendicular to the longitudinal direction), and at least 100 mm apart. From the viewpoint of ease of measurement, a position separated by 300 mm or more is preferable, a position separated by 500 mm or more is more preferable, and a position separated by 900 mm or more is particularly preferable.

The thickness of the surface layer preferably satisfies a specific relationship with the inert particles contained in the surface layer. That is, the thickness t (μm) of this surface layer and the average particle diameter D (μm) of the inert particles contained in the surface layer.
It is preferable that the content W and the content W (wt%) satisfy the following expressions 2 and 3.

[0035]

[Equation 5]

If (D × W) exceeds 2, the amount of particles in the surface layer increases, and the surface is liable to be scraped and the roughness becomes rough, which is not preferable. From this point, (D × W)
Is preferably 1.4 or less, more preferably 0.6 or less, and particularly preferably 0.2 or less. On the other hand, when (D × W) is less than 0.01, the amount of particles in the surface layer is small, and the slipperiness is poor and the blocking is poor, which is not preferable. From this point, (D × W) is 0.
02 or more is preferable, 0.04 or more is more preferable,
0.08 or more is particularly preferable.

When (t / √D) is smaller than 0.1, the surface layer thickness is too thin for the particle size, and the particles are likely to fall off, or chipping occurs in the process. Not preferable. From this point, (t / √D) is preferably 0.2 or more, more preferably 0.25 or more, and particularly preferably 0.3 or more. On the other hand, when (t / √D) exceeds 4, the thickness of the surface layer is too thick for the particle size, and even if the thickness of the surface layer is changed, the surface roughness Ra hardly changes, and the effect of the present invention is obtained. It is not preferable because it is difficult to exhibit. From this point,
The (t / √D) is preferably 2 or less, more preferably less than 1, and particularly preferably 0.5 or less.

In the present invention, when the width of the film is narrow (for example, 2000 mm or less), the surface thickness of the biaxially oriented polyester film becomes thicker as the film width changes and the orientation angle increases. It is preferable that the thickness satisfies a specific relationship with the orientation angle. That is, the minimum orientation angle portion (A 'portion) of the surface layer
It is preferable that the thickness t _A ′ and the thickness t _B ′ of the maximum orientation angle portion (B ′ portion) satisfy the following Expression 4.

[0039]

[Equation 6]

(Where, t _A ′: thickness of the surface layer of the A ′ part (μm) t _B ′: thickness of the surface layer of the B ′ part (μm) θ _A ′: orientation angle of the A ′ part (°) θ _B ': orientation angle (°) of B'part L': distance (m) in the film width direction from A'part to B'part.)

Here, the orientation angle means an inclination angle between the axis parallel to the longitudinal direction (longitudinal direction) of the film and the orientation main axis.

In the present invention, the total thickness of the biaxially oriented laminated polyester film has a constant thickness according to the purpose. For this reason, the thickness of the other layer (other surface layer, base layer or inner layer) changes corresponding to the thickness variation of the surface layer in the film width direction within a range in which the total thickness is kept constant. You may.

The total thickness of the biaxially oriented laminated polyester film is usually 1 to 300 μm, preferably 2 to 8 μm.
The thickness is 0 μm, more preferably 2 to 25 μm, and particularly preferably 4 to 17 μm. And base layer or inner layer (core layer)
Is preferably thicker than the surface layer.

If the overall film thickness becomes too thin,
The change range of the thickness of the surface layer is narrowed, so that the roughness cannot be adjusted due to the change of the thickness of the surface layer, which is not preferable.
On the other hand, if the overall film thickness is too large, the ratio of the surface layer to the base layer becomes too small, making it difficult to form a laminated film, and the thickness of the surface layer tends to vary, which is not preferable.

The biaxially oriented laminated polyester film of the present invention can be manufactured by a conventionally known method except that the surface layer is made uniform in the film width direction. For example, it can be manufactured by first manufacturing a laminated unoriented film and then biaxially orienting the film.

The laminated non-oriented film can be manufactured by a conventionally accumulated manufacturing method of a laminated film.
For example, a method of laminating a film layer forming a surface layer and a film layer forming a core layer in a melted state or a cooled and solidified state of polyester can be used.
More specifically, it can be produced by a method such as coextrusion / extrusion lamination. Among these, the co-extrusion method is the one in which the effect of the present invention is most easily exhibited.

A laminated unoriented film having different layer thicknesses in the width direction of the film is produced by the coextrusion method by using a manifold of two layers or three or more layers at the time of coextrusion molding.
This can be achieved by changing the die slit gap in the width direction immediately before the outermost layer polymer joins with the other layer polymer. Also, another method such as a feed block method may be adopted.

In the case of two layers, the surface layer on the side opposite to the surface layer is formed of the base layer.

The film laminated by the above-mentioned method can be made into a biaxially oriented film by further carrying out according to the conventionally accumulated manufacturing method of a biaxially oriented film. For example, polyester is melted and coextruded at a temperature of melting point (Tm: ° C.) to (Tm + 70) ° C. and an intrinsic viscosity of 0.35 to
A laminated unstretched film of 0.9 dl / g was obtained, and the laminated unstretched film was uniaxially (longitudinal or transverse) (Tg
-10) to (Tg + 70) ° C. (however, Tg: glass transition temperature of polyester) is stretched at a draw ratio of 2.5 to 5.0 times, and then in a direction perpendicular to the stretching direction (the first stretching is the longitudinal direction). In the case of, the second stage stretching is in the lateral direction)
It can be produced by stretching at a temperature of g (° C.) to (Tg + 70) ° C. at a draw ratio of 2.5 to 5.0 times. In this case, the area stretching ratio is preferably 9 to 22 times, more preferably 12 to 22 times. The stretching means may be simultaneous biaxial stretching or sequential biaxial stretching. Of these, sequential biaxial stretching using a stenter for transverse stretching is preferable because it is most effective.

Further, the biaxially oriented film has (Tg + 7
It can be heat-set at a temperature of 0) ° C. to Tm (° C.).
For example, polyethylene terephthalate film is preferably heat set at 190 to 240 ° C. The heat setting time is, for example, 1 to 60 seconds.

Various physical properties and characteristics in the present invention are measured and defined as follows.

(1) Average particle size of particles (area circle equivalent diameter) The following method is available for measuring the area circle equivalent diameter of particles. 1) When obtaining the average particle diameter of the area circle equivalent diameter from the powder. 2) When obtaining the average particle size of the equivalent circle diameter of the particles in the film.

1) From powders The powders are scattered on an electron microscope sample stand so that the individual particles do not overlap as much as possible, and a gold thin film vapor deposition layer is formed on the surface thereof with a thickness of 200 to 300 angstroms by a gold sputtering device. Formed, scanning electron microscope, for example, 100
Observing at a magnification of 00 to 30000, and using Luzex 500 manufactured by Nippon Regulator Co., Ltd., the major axis, the minor axis, and the area equivalent circle diameter of at least 100 particles are determined. Then, the average particle size is calculated from these values.

2) In the case of particles in the film A small piece of the sample film is fixed on a sample stand for a scanning electron microscope, and a sputtering device (JFC-made by JEOL Ltd.) is used.
1100 type ion etching apparatus) is used to perform ion etching treatment on the film surface under the following conditions. The condition is that the sample is placed in a bell jar, the degree of vacuum is raised to a vacuum state of about 10 ^-3 Torr, the voltage is 0.25 kV, and the current is 1
Ion etching is performed at 2.5 mA for about 10 minutes. Further, the film surface is subjected to gold sputtering with the same apparatus, and observed with a scanning electron microscope at a magnification of 10,000 to 30,000, and the average particle size is calculated in the same manner as in 1).

(2) Flatness of film surface Ra (center line average roughness) is measured according to JIS B 0601. Using a stylus-type surface roughness meter (SURFCORDER SE-30C) made by Kosaka Laboratory Ltd., a chart (film surface roughness curve) can be obtained under the conditions of a needle radius of 2 μm and a load of 30 mg. A roughness curve Y = f (x) is obtained by extracting a portion having a measurement length L from the film surface roughness curve in the direction of the center line, and defining the center line of the extracted portion as the X axis and the direction of longitudinal magnification as the Y axis. When expressed by, the value (Ra: nm) given by the following equation is defined as the roughness of the film surface.

[0056]

[Equation 7]

In the present invention, the measurement length is 1.0 mm, the cut-off value is 0.08 mm, 7 pieces are measured, and Ra is expressed as an average value of 5 pieces excluding the largest value and the smallest value.

(3) Orientation angle Using a polarizing microscope, the longitudinal direction of the film (longitudinal direction)
The angle of deviation of the orientation main axis from the axis parallel to is measured and used as the orientation angle.

(4) Refractive index and birefringence index Using sodium D line (589 nm) as a light source, methylene iodide was used as a mount solution, and the Abbe refractometer was used to measure the refractive index in the longitudinal and width directions of the film. taking measurement. The difference between the refractive index in the longitudinal direction (n _MD ) and the refractive index in the width direction (n _TD ) (Δ
n = n _MD −n _TD ) to obtain the birefringence.

(5) Layer Thickness Regarding the thickness of each layer of the laminated polyester film, paying attention to the difference in the type and amount of the lubricant contained in each layer, the fluorescent X-ray method and the film were cut into thin pieces, It is obtained by observing the cross-section with a transmission electron microscope, together with the method of searching for the boundary surface.

(6) Winding property (i) Roll winding shape A When the film is wound into a wide and long roll having a width of 1000 mm of 5000 m and a width of 500 mm of 9000 m, it is easy to obtain a good winding shape. Evaluate. ⊚: Even when the winding conditions (tension, contact pressure, etc.) are changed when the film is wound into a wide and long roll at a winding speed of 200 m / min.
A good winding shape can be obtained in a fairly wide range. ◯: When the winding condition (tension, contact pressure, etc.) is changed at a winding speed of 200 m / min, wrinkles are likely to occur, and bumps (bump-shaped protrusions) are easily generated, so that the condition range for good winding is narrow, but Under certain conditions, a good winding shape can be obtained. Δ: At a winding speed of 200 m / min, even if the winding conditions are variously changed, wrinkles are generated, bumps are formed, and end faces are displaced, so that a good winding shape cannot be obtained. When the winding speed is set to 50 m / min, a substantially good winding shape can be obtained by setting the winding condition to a specific condition, but the speed is slow and it is industrially somewhat insufficient. ×: Even if the winding speed is 200 m / min, the winding speed is 50 m / min, or the winding conditions (tension, contact pressure, etc.) are changed,
There are strong wrinkles, bumps (hump-shaped protrusions),
A good winding appearance cannot be obtained due to misalignment of the end faces.

(Ii) Winding property B during production of magnetic tape B [Production of magnetic tape] 100 parts by weight of γ-Fe ₂ O ₃ (hereinafter, simply referred to as “part”) and the following composition were placed on a ball mill for 12 hours. Kneaded and dispersed.

Polyester polyurethane 12 parts Vinyl chloride-vinyl acetate-maleic anhydride copolymer 10 parts α-alumina 5 parts Carbon black 1 part Butyl acetate 70 parts Methyl ethyl ketone 35 parts Cyclohexane 100 parts Further after dispersion fatty acid: oleic acid 1 part Fatty acid : 1 part of palmitic acid 1 part of fatty acid ester (amyl stearate) was added and kneading was continued for 10 to 30 minutes. Furthermore, 7 parts of a 25% ethyl acetate solution of a triisocyanate compound was added,
A high-speed shear dispersion is carried out for 1 hour to prepare a magnetic coating solution.

The obtained coating solution is applied on a polyester film so that the dry film thickness is 2.5 μm (applied to the surface [rear surface or base material layer surface] opposite to the surface layer characterized in the present invention. ).

Then, after orientation treatment in a DC magnetic field, 1
Dry at 00 ° C. After drying, a calendering process is performed, and a magnetic tape is obtained by slitting into a 1/2 inch width.

[Evaluation of Winding Yield] The winding property is evaluated when slitting to the above 1/2 inch width. In the production of a magnetic tape, a large number of dozens of tapes are taken in a 1/2 inch width from a wide web of about 300 to 1500 mm, and the winding state at this time is judged based on the following. ⊚: At a winding speed of 300 m / min, the entire number can be taken up cleanly in a wide range of conditions such as slitter tension. ◯: When the conditions such as the tension of the slitter are changed at a winding speed of 300 m / min, there are conditions under which a good number of windings can be obtained, but the range is narrow. However, at a winding speed of 100 m / min, a wide range can be taken up cleanly. Δ: When conditions such as the tension of the slitter are changed at a winding speed of 300 m / min, there is no condition that the number of windings is good, but some end surface deviation is within 0.5 mm, or Weak irregularities and deformations (bumps, etc.)
It is possible to obtain something (pancake) with a degree of being seen, and it is judged to be a usable level. The condition is narrow at 100 m / min, but a clean winding can be obtained. ×: Even if the slitter condition is changed at a winding speed of 300 m / min, a large amount of end face displacement occurs, or winding irregularities / deformations (bumps, bump-like protrusions, etc.) occur strongly. , The whole does not have a good winding shape,
Some items (pancakes) cannot be used. 1
Even at a winding speed of 00 m / min, even if the slitter conditions were changed, the end face displacement (around 0.5 mm) was observed, and the slight winding irregularities / deformations (bumps, etc.) were observed. XX: 300 m / min, 100 m / min, or even if the slitter condition is changed, a large amount of end face misalignment occurs, and winding irregularities / deformations (bumps) are strongly generated, resulting in good winding. I can't get a figure.

[0067]

EXAMPLES The present invention will be further described below with reference to examples.

Examples 1 to 3 and Comparative Example 1 Dimethyl terephthalate and ethylene glycol, manganese acetate as a transesterification catalyst, antimony trioxide as a polymerization catalyst, phosphorous acid as a stabilizer, and Table 1 as a lubricant. 0.62 dl / intrinsic viscosity (orthochlorophenol, 35 ° C.)
g of polyethylene terephthalate for the surface layer and the core layer was obtained.

Next, the polyethylene terephthalate for the surface layer and the core layer were dried at 170 ° C. for 3 hours, then fed to separate extruders of a coextrusion film forming machine and coextruded from a three-layer die to obtain a laminated unstretched film. It was In order to change the thickness ratio of each layer in the film width direction, the die interval of each layer in the die portion of the manifold type three-layer die can be appropriately adjusted in the film width direction.

The laminated unstretched film thus obtained was sequentially biaxially stretched at a longitudinal stretching ratio of 4.0 and a transverse stretching ratio of 3.8. At this time, the temperature of the low-speed stretching roll in the longitudinal stretching was 66 ° C, and the heating with the IR heater (the surface temperature was 830 ° C)
, And the transverse stretching was carried out at 97 ° C. using a stenter, and further heat treatment was carried out at 220 ° C.

The biaxially oriented laminated film thus obtained had a film width of 4.5 m when it exited from the stenter, and the center of the film in the width direction and 1000 m from the center.
A slit film having a width of 1000 mm was wound on a roll with a length of 5000 m under the same conditions to obtain four film rolls. In each of Examples 1 to 3, the winding was good, and the winding appearance was also good. On the other hand, in Comparative Example 1, the center side was wound up and the winding form was good, but the side end side was insufficient in winding property and the winding form was also poor.

Of these film rolls, one on the center side (roll 1) and one on the side end side (roll 2) are coated with a magnetic layer by the above-mentioned method and subjected to calendering treatment, and then a 1/2 inch width It was slit into and rolled up on a pancake under the same conditions. These characteristics are shown in Table 1.

Example 4 and Comparative Example 2 An ethylene glycol slurry containing crosslinked polystyrene particles was prepared, and dimethyl terephthalate was subjected to a transesterification reaction using manganese acetate as an transesterification catalyst, and then the reaction product. Was subjected to polycondensation using antimony trioxide as a polymerization catalyst and phosphorous acid as a stabilizer to obtain a polyethylene terephthalate for surface layer having an intrinsic viscosity of 0.70 dl / g.

In the same manner as above except that the crosslinked polystyrene particles were not used, polyethylene terephthalate having an intrinsic viscosity of 0.62 dl / g substantially containing no inactive particles was produced and used as a core layer.

Then, the polyethylene terephthalate for the surface layer and the core layer were dried under reduced pressure at 180 ° C. for 3 hours, respectively, and then fed to separate extruders of a coextrusion film-forming machine and coextruded from a three-layer die to form a laminate. A stretched film was obtained. In addition, in order to change the thickness ratio of each layer in the film width direction, the die interval of each layer in the die portion of the manifold type three-layer die can be appropriately adjusted in the film width direction.

The laminated unstretched film thus obtained was sequentially biaxially stretched at a longitudinal stretching ratio of 4.5 times and a lateral stretching ratio of 3.6 times. At this time, the temperature of the low-speed stretching roll in the longitudinal stretching was 66 ° C, and the heating with the IR heater (the surface temperature was 830 ° C)
, And the transverse stretching was carried out at 100 ° C. using a stenter, and further heat treatment was carried out at 200 ° C. for 5 seconds.

The biaxially oriented laminated film thus obtained had a film width of 4.5 m when it exited from the stenter. Therefore, as in Example 1, there were four 1000 mm wide film rolls in the width direction of the stenter. Slit as 1
It was wound up to a width of 000 mm × 5000 m.

Further, the magnetic layer was applied by the above-mentioned method, subjected to calendering treatment, and then slit into a 1/2 inch width. The characteristics are shown in Table 2.

Example 5 Manganese acetate was used as a transesterification catalyst of dimethyl terephthalate and ethylene glycol, antimony trioxide was used as a polymerization catalyst, phosphorous acid was added as a stabilizer, and additive particles shown in Table 2 were added as a lubricant. Polymerized by a conventional method to give an intrinsic viscosity of 0.67 dl / g
To obtain polyethylene terephthalate for the surface layer and for the core layer having an intrinsic viscosity of 0.60 dl / g.

Next, the polyethylene terephthalate for the surface layer and the core layer were dried at 170 ° C. for 3 hours, then fed to separate extruders of a coextrusion film forming machine and coextruded from a three-layer die to obtain a laminated unstretched film. It was In order to change the thickness ratio of each layer in the film width direction, the die interval of each layer in the die portion of the manifold type three-layer die can be appropriately adjusted in the film width direction.

The laminated unstretched film thus obtained was sequentially biaxially stretched at a longitudinal stretching ratio of 3.7 times and a transverse stretching ratio of 3.8 times. At this time, the temperature of the low-speed stretching roll in the longitudinal stretching was 72 ° C, and the heating with the IR heater (surface temperature 830 ° C)
, And the transverse stretching was carried out at 102 ° C. using a stenter, and further heat treatment was carried out at 220 ° C.

The biaxially oriented laminated film thus obtained had a film width of 4.5 m when it exited from the stenter. Therefore, as in Example 1, four 1000 mm wide film rolls were taken in the width direction of the stenter. Slit as 1
It was wound up to 000 mm × 5000 m.

Further, the magnetic layer was applied by the above method, subjected to calendering treatment, etc., and then slit into a 1/2 inch width and wound up to 5000 m. The characteristics are shown in Table 2.

[Example 6] In Example 5, the stretching conditions were that the longitudinal stretching ratio was 3.4 times, and the transverse stretching ratio was 4.3 times. The temperature was set to 76 ° C., the heating with an IR heater was also used, the transverse stretching temperature was set to 107 ° C., and the thickness ratio of the surface layer was adjusted.
The characteristics are shown in Table 2.

[0085]

[Table 1]

[0086]

[Table 2]

Examples 7 to 11 Dimethyl terephthalate and ethylene glycol, manganese acetate as a transesterification catalyst, and antimony trioxide as a polymerization catalyst,
Polyethylene for surface layer and core layer having intrinsic viscosity (orthochlorophenol, 35 ° C.) of 0.62 dl / g was obtained by adding phosphorous acid as a stabilizer and adding particles shown in Table 3 as a lubricant and polymerizing by a conventional method. I got terephthalate.

Next, the polyethylene terephthalate for the surface layer and the core layer were dried at 170 ° C. for 3 hours, then fed to separate extruders of a coextrusion film forming machine and coextruded from a three-layer die to obtain a laminated unstretched film. It was In order to change the distribution of the thickness ratio of each layer in the film width direction,
In the die part of the manifold type three-layer die, the die interval of each layer can be adjusted appropriately in the film width direction.

The laminated unstretched film thus obtained was sequentially biaxially stretched at a longitudinal stretching ratio of 4.1 times and a transverse stretching ratio of 3.7 times. At this time, the temperature of the low-speed stretching roll in the longitudinal stretching was 66 ° C, and the heating with the IR heater (the surface temperature was 830 ° C)
, And the transverse stretching was carried out at 97 ° C. using a stenter, and further heat treatment was carried out at 220 ° C.

The obtained biaxially oriented laminated film had a film width of 1.2 m when it exited from the stenter, and the center of the film in the width direction and 500 mm from the center.
Slits were separated from each other, and a slit film having a width of 500 mm was wound around a roll with a length of 9000 m to obtain two film rolls.

A magnetic layer was coated on one of these film rolls by the above-mentioned method, subjected to calendering treatment, slit into a 1/2 inch width, and wound up under the same conditions. These characteristics are shown in Table 3.

[0092]

[Table 3]

[0093]

According to the present invention, it is possible to provide a biaxially oriented laminated polyester film in which variation in surface characteristics in the width direction is reduced.

Claims (5)

[Claims] 1. The thickness of at least one surface layer is 0.02.
and the surface roughness Ra of the surface layer is 3 to 40 nm, and the fluctuation in the film width direction is 5 μm or more and 3 μm or less.
% / 500 mm or less, a biaxially oriented laminated polyester film. 2. The thickness of the surface layer varies in the width direction of the film, and the refractive index in the longitudinal direction (n _MD ) and the refractive index in the width direction (n _TD )
The biaxially oriented laminated polyester film according to claim 1, wherein the biaxially oriented laminated polyester film becomes thicker as the difference (birefringence index: Δn) becomes larger. 3. A birefringence smallest portion of the surface layer thickness of t _A and birefringence maximum of (A portion) (B portion) of the thickness t _B and is represented by the following formula 1
The biaxially oriented laminated polyester film according to claim 1 or 2, which satisfies the above condition. [Equation 1] (However, t _A : thickness of the surface layer of the A portion (μm) t _B : thickness of the surface layer of the B portion (μm) Δn _A : between the longitudinal refractive index n _MD and the widthwise refractive index n _TD of the A portion Difference (birefringence: n _MD -n _TD ) Δn _B : Difference between longitudinal refractive index n _MD and widthwise refractive index n _{TD of} part B (birefringence: n _MD -n _TD ) L: From part A (Distance in the film width direction to part B (m) D: Average particle size (μm) of the lubricant contained in the surface layer) 4. The thickness t (μm) of the surface layer and the average particle diameter D (μm) and the content W (wt%) of the inert particles contained in the surface layer are represented by the following formulas 2 and 3. Claim 1 which is satisfied,
The biaxially oriented laminated polyester film described in 2 or 3. [Equation 2] 5. The claims and the orientation angle up unit 'thickness t _A of (part orientation angle minimum portion of the surface layer A)' and (B 'part) of the thickness t _B' satisfy the following equation 4 1 Alternatively, the biaxially oriented laminated polyester film described in 2. [Equation 3] (However, t _A ′: thickness of the surface layer of the A ′ part (μm) t _B ′: thickness of the surface layer of the B ′ part (μm) θ _A ′: orientation angle of the A ′ part (°) θ _B ′: B'orientation angle (°) L ': Distance (m) in the film width direction from A'to B'.)