JP3217338B2 - Composite oriented polyester film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a composite oriented polyester film suitable as a base film for a magnetic tape.

[0002]

2. Description of the Related Art Polyester films are widely used for various purposes including magnetic recording because of their excellent physical and chemical properties. Among them, especially when used as a base film for a magnetic tape, the flatness of the surface and the running property are regarded as important. As a method of improving running properties, a method of adding inorganic or organic fine particles to a film to roughen the film surface is general.
However, roughening of the film is not preferable because it causes deterioration of electromagnetic conversion characteristics.

Recently, with the speeding up of the magnetic tape manufacturing process, there has been a demand for a film having more excellent abrasion resistance in the calendering process. That is, the calendering step is a step of smoothing the surface after applying and drying the magnetic paint, but since the film passes between rolls to which extremely high pressure is applied, projections on the film surface are scraped off. There is a problem that abrasion powder is generated, and improvement thereof is expected.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a composite orientation which is excellent in both running properties and electromagnetic conversion characteristics and generates very little abrasion powder in a calendering step even when a magnetic tape is used. The purpose is to provide a polyester film.

[0005]

In order to achieve the above object, the composite oriented polyester film of the present invention is a composite oriented polyester film composed of at least three or more layers, and one of the outermost layers (A layer) Does not contain particles having a substantial ability to form protrusions in the resin constituting, and contains particles having a substantial ability to form protrusions in a layer (layer B) adjacent to the layer A, and the surface of the layer A Is characterized in that the average roughness of the surface on the opposite side is two thirds or less of the average roughness of the surface of the layer A. In order to achieve the above object, the composite oriented polyester film of the present invention is a composite oriented polyester film composed of three layers, A layer, B layer, and C layer, and one of the outermost layers (A layer) Does not contain particles having a substantial projection-forming ability in the resin constituting, and contains particles having a substantial projection-forming ability in a layer (B layer) adjacent to the A layer, and contains A particles adjacent to the B layer. Outermost layer other than layer (C layer)
Is two-thirds of the average roughness of the surface of layer A.
It is characterized by the following.

[0006] The composite oriented polyester film of the present invention comprises at least three polyester layers.
Any structure having three or more layers may be used. The layers other than the above three layers may be layers other than the polyester layer.

[0007] The polyester constituting each layer of the composite oriented polyester film of the present invention is not particularly limited, and is arbitrary, but at least 80 mol% of the repeating unit is ethylene terephthalate or ethylene-2,6 naphthalate. In this case, the effect of the present invention is most remarkable, so that it is particularly preferable. Other copolymerization components include isophthalic acid, p-β-oxyethoxybenzoic acid, 2,6-naphthalenedicarboxylic acid, terephthalic acid, 4,4′-dicarboxylic diphenyl, 4,4′-dicarboxylbenzophenone, bis (4-carboxyphenyl) ethane, adipic acid, sebacic acid, 5-sodium sulfoisophthalic acid, dicarboxylic acid components such as cyclohexane-1,4-dicarboxylic acid, propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexane dimethanol , Ethylene oxide adduct of bisphenol A, polyethylene glycol,
Glycol components such as polypropylene glycol and polytetramethylene glycol, and oxycarboxylic acid components such as p-oxybenzoic acid can be arbitrarily selected and used. In addition, a compound containing a small amount of an amide bond, a urethane bond, an ether bond, a carbonate bond, or the like may be contained as the other copolymer component.

The polyester may be produced by any method such as a direct polymerization method in which an aromatic dicarboxylic acid is directly reacted with a glycol and a transesterification method in which a dimethyl ester of an aromatic dicarboxylic acid is transesterified with a glycol. Can be applied.

In the composite oriented polyester film of the present invention, it is necessary that the resin constituting at least one of the outermost layers (layer A) contains substantially no particles capable of forming projections. This is because the layer A that does not substantially contain particles having the ability to form protrusions has a protective effect against chipping off of the surface protrusions of the polyester film, and the film surface protrusions formed based on the particles contained in the layer B fall off. This is because it is possible to obtain a surface in which the generation of wear powder in the calendering step is significantly improved. The term "projection forming ability" as used herein refers to the ability to form a projection having a height of 50 nm or more on the film surface, and the ability can be evaluated by a scanning tunneling microscope or the like. Conversely, a protective layer (A layer) which does not substantially contain particles capable of forming protrusions
When no is provided, or when a layer containing particles having substantial projection forming ability is provided as the outermost layer, the projections of the film surface are likely to fall off during the calendering process, and the generation of wear powder is remarkable. Become.

In the composite oriented polyester film of the present invention, the layer adjacent to the layer A (layer B) substantially contains particles capable of forming projections. By forming projections on the surface of layer A based on the particles added to layer B, A
Excellent running properties can be imparted to the layer surface (running surface).

The inert particles having the ability to form protrusions include carbonates of Ca, Mg, Sr and Ba, Na,
Sulfates of K, Mg, Ca, Ba and Al, Na, K, M
g, Ca, Sr, Ba, Al, Ti and Zr phosphates, silicon dioxide, alumina, composite silicate compounds (amorphous region is crystalline clay mineral, aluminosilicate compound, etc.), hot asbestos (zircon, Fly ash, etc.), oxides of Zr and Ti, terephthalates of Ca, Ba, Zn and Mn, chromates of Ba and Pb, carbon (carbon black, graphite, etc.), glass (glass powder, glass beads, etc.) And inorganic particles such as fluorite and ZnS, and organic particles such as a crosslinked polystyrene resin, a crosslinked acrylic resin, a benzoguanamine resin, a silicone resin and a crosslinked polyester resin. Preferably, calcium carbonate, silicic anhydride, hydrous silicic acid, aluminum oxide, aluminum silicate, barium sulfate, calcium phosphate, zirconium phosphate, titanium oxide, lithium benzoate, glass powder, clay (kaolin, bentonite, clay, etc.), Examples include talc and diatomaceous earth. These inert particles may be natural products or synthetic products. Further, they may be used alone, two or more kinds may be used in combination, or may be used in the form of a complex salt.

The average particle size of the inert particles varies depending on the thickness and the amount of the layer A and the layer B. The average particle diameter of the inert particles is such that a protrusion having a height of about 0.1 to 1 μm is formed on the layer A. What is necessary is just to have a particle diameter. The particle size is usually 0.05μ
m to 5.0 μm, preferably 0.1 μm to 2.5 μm
It is.

The amount of the inert particles in the layer B is 0.05 to 40 parts by weight based on 100 parts by weight of the polyester.
Preferably it is 0.2 to 10 parts by weight.

In the composite oriented polyester film of the present invention, the layer (layer C) other than the layer A adjacent to the layer B contains substantially no particles capable of forming protrusions or the particles contained in the layer B It is necessary to contain particles having an average particle diameter of two-thirds or less of the particles having the largest average particle diameter (that is, 3 μm or less, preferably 0.05 to 1.5 μm). When the film has a three-layer structure, the surface opposite to the surface of the A layer (in the case of a magnetic tape, the layer surface on which the magnetic layer is preferably formed) is also provided with slipperiness. It is preferable to add particles to the C layer.

Examples of the particles that can be added to the layer C include particles having the same composition as the particles exemplified as the above-mentioned inert particles having the ability to form protrusions. By limiting the average particle size of the particles that can be added to the C layer within the above range, C
It is possible to substantially prevent the formation of protrusions on the surface of the layer A (the running surface in the case of a magnetic tape) due to the particles added to the layer. Accordingly, the protrusions formed on the surface of the layer A are substantially only those formed by the particles added to the layer B, and have uniform and high-density protrusions. It is possible to obtain. vice versa,
When particles having an average particle diameter outside the above range are added to the C layer, projections are formed on the surface of the A layer by the particles added to the C layer, or the projections on the running surface become uneven, For example, the roughness of the magnetic surface (the surface on the side opposite to the surface of the A layer) increases, and the electromagnetic conversion characteristics deteriorate.

The amount of the inert particles in the layer C is 0.01 to 10 parts by weight per 100 parts by weight of the polyester.
Preferably it is 0.04 to 2 parts by weight.

In the polyester film of the present invention, the thickness of the layer A (Ta), the thickness of the layer B (Tb) and the thickness of the entire film (Tf) satisfy the following relationship: Ta + Tb <(（) Tf. Is preferred.

Generally, when the tape running surface is roughened, the running properties are improved, but the electromagnetic conversion characteristics are deteriorated due to the transfer of the running surface roughness to the surface of the magnetic layer. However, Ta +
By setting Tb within the above range, it is possible to obtain a running surface (surface of layer A) having a very small transfer effect, and to obtain an electromagnetic recording film having both excellent electromagnetic conversion characteristics and running properties. Conversely, if Ta + Tb exceeds the above range, the transfer of the running surface roughness to the magnetic surface becomes remarkable, and the magnetic surface is roughened, resulting in poor electromagnetic conversion characteristics.

Therefore, from the viewpoint of the electromagnetic conversion characteristics, the thinner the layers A and B are, the better. However, in order to improve the calendering, the effect of protecting the running surface by the layer A must be sufficient. There must be. On the other hand, if the layer A is too thick, the projection effect on the film surface becomes flat due to its coating effect, and the running property tends to be adversely affected. Therefore, Ta is preferably 0.01 to 2 μm, particularly preferably 0.05 to 1 μm, and Ta is 1/5 of Tf.
It is preferred to be less than. On the other hand, the lower limit of Tb is not particularly limited.
b is preferably 0.05 to 3 μm, particularly preferably 0.1 to 3 μm.
1 to 2 μm. Tf is preferably 3 to 300.
μm, particularly preferably 5 to 20 μm. The thickness of the layer A and the layer B is determined by the secondary ion mass spectrometry (SIM
S) can be evaluated.

The surface roughness of the composite oriented polyester film of the present invention is not limited at all and is optional.
It is preferable that the average roughness of one surface is not more than two thirds of the average roughness of the other surface. In particular, it is preferable that the rough surface is the surface of the layer A and the average roughness is 0.010 to 0.030 μm. This is because, by forming a magnetic layer on a flat surface, it is possible to suppress the surface roughening of the magnetic layer due to the underlayer effect, and in addition, the surface of the layer A is extremely roughened by the transfer effect. This is because it has a property that it hardly occurs, and the electromagnetic conversion characteristics can be further improved. The average roughness of the surface (Ra) is
Using a surface roughness meter Surfcom 300A manufactured by Tokyo Seimitsu Co., Ltd., needle diameter 2 μm, load 0.07 g, measurement standard length 0.8 m
m means the center line average roughness measured under the conditions of a cutoff of 0.08 mm.

The method for producing the composite oriented polyester film of the present invention is arbitrary, and is not particularly limited. For example, it can be produced as follows.
That is, it is obtained by melting and laminating the polyesters constituting the A layer, the B layer, and the C layer, coextruding, and then biaxially stretching and heat-treating by a conventionally known method. The stretching order may be any of vertical and horizontal, horizontal and vertical, and simultaneous two axes. Further, three or more stages of stretching may be performed by appropriately combining transverse stretching, longitudinal stretching, and simultaneous biaxial stretching. After the biaxial stretching, heat treatment is performed in a tenter.
It is preferably performed at 0 to 230 ° C. for 2 to 10 seconds. Further, during or after the heat treatment, the relaxation treatment can be performed in the horizontal and vertical directions.

When the composite oriented polyester film of the present invention is used as a magnetic tape, a magnetic layer is formed on one surface of the film. The magnetic layer may be formed on any surface of the film, but when the surface of layer A is used as a running surface and the magnetic layer is provided on the opposite surface, the effect of the present invention is most remarkable, so that it is preferable. . Also, a back coat may or may not be provided on the running surface. However, when the surface of the layer A is used as the running surface, excellent running properties can be obtained without providing the back coat.

[0023]

FIG. 2 shows an embodiment of the composite oriented polyester film of the present invention. In FIG. 2, 7 indicates the A layer, 8 indicates the B layer, 9 indicates the C layer, 10 indicates the inactive particles, and 11 indicates the inactive particles. In the following description, the production of the polyester and the evaluation of the ability to form protrusions were performed as follows. [Production of Polyester and Evaluation of Ability to Form Protrusions] When polymerizing polyester by a conventional method, each particle was added at the time of polymerization as shown in Table 1, and polyethylene terephthalate having an intrinsic viscosity of 0.620 (PET-1 to PET- 5) was created. Next, the obtained polyester (PET-1 to P-P)
After drying each of ET-4), it is melted at 290 ° C.
Cast on a cooling drum at 30 ° C.
A μm unstretched film was obtained. A roll which heated the film to 75 ° C. and an infrared heater having a surface temperature of 600 ° C. (installed at a position 20 mm away from the film)
And stretched 3.3 times in the machine direction between the low-speed roll and the high-speed roll. The film was further introduced into a tenter, stretched 4.4 times in the transverse direction at 100 ° C.
For 5 seconds to prepare a biaxially oriented polyester film having a thickness of 15 μm. Using the film thus obtained, the projection forming ability of each particle was evaluated, and the results are shown in Table 1.

The measurement of the particle diameter and the projection forming ability of the inert particles in Table 1 was performed as follows. Particle Size of Inert Particles The powder is sufficiently dispersed in an ethylene glycol (EG) slurry by high-speed stirring, and the particle size distribution in the obtained slurry is measured using a light transmission centrifugal sedimentation type particle size analyzer SA- manufactured by Shimadzu Corporation. It was measured using a CP3 type. In this distribution, the value of 50% integration is used.

Presence or absence of protrusion forming ability After sputter-coating the film surface with 5 nm of platinum palladium, first using a scanning tunneling microscope STA350 manufactured by Seiko Denshi Kogyo Co., Ltd., an optical microscope attached to the same device to enlarge the magnification. The film surface was observed at about 2000 × (50 × objective lens). Next, a large number of protrusions formed by the inert particles (about 1/20 μm
² or more) Those observed on the film surface were judged to have projection forming ability. On the other hand, when the projections are difficult to observe, a portion where the projections formed by the abnormal aggregates of the particles are not observed is selected with an optical microscope, and then the revolver is switched from the optical microscope to a scanner of a tunnel microscope, and the same portion is 20 μm ^2. Was measured with a tunnel microscope (number of pixels = 256 pixels × 128 lines).
After performing a tilt correction and a smoothing process on the surface shape obtained from the tunnel microscope measurement, the height distribution of the peak number and the height distribution (histogram) of the pixel number were measured. The height level at which the number of pixels is maximized is defined as a zero level, and the number of peaks having a height of less than 50 nm is 95% or more of the total number of peaks (the maximum number of peaks) And In the case where the number of peaks existing in the area of 20 μm ² was less than 100, the same measurement was repeated until the number of peaks reached 100.

Examples 1 to 3 and Comparative Examples 1 to 3 The polyesters constituting the layers A, B and C shown in Table 2 were each dried and then supplied to separate extruders. Then, the ratio of the discharge amount of each extruder was adjusted so as to have the thickness ratio of each layer shown in Table 2, melted at 290 ° C., laminated using a T die, and cooled at 30 ° C. It was co-extruded on a drum to obtain a 220 μm thick unstretched composite oriented polyester film. The unstretched film obtained in this manner was biaxially stretched and heat-treated in exactly the same manner as the stretching method used in the evaluation of the ability to form projections, to produce a composite oriented polyester film shown in Table 2. The thickness of each layer shown in the table was calculated from the polyester discharge ratio of each layer and the total thickness of the obtained film.

Comparative Example 4 As shown in Table 2, without layer A, layer B and layer C were
A composite oriented polyester film was prepared in exactly the same manner as in Example 1 except that the polyester had a two-layer structure using the polyester shown in the same table.

Comparative Examples 5 to 6 As shown in Table 2, the same procedures as in Example 1 were conducted except that the layer B was omitted, and the layers A and C had a two-layer structure using the polyester shown in the same table. A composite oriented polyester film was prepared in exactly the same manner.

Test Example 1 The composite oriented polyester films of Examples and Comparative Examples were tested for calendering properties, running properties and electromagnetic conversion properties in the following manner, and the average roughness was measured. The results are shown in Table 3. Calender shaving characteristics A 30 cm wide film was treated with a super calender (line pressure: 300 kg / cm, running speed: 300 m / min) for 40,000 m using a four-stage super calender. The amount of white powder adhering to the elastic roll was visually observed and ranked as follows. Was done. 1 ... no white powder is observed 2 ... faint white powder is observed but very small amount 3 ... small amount of white powder is observed 4 ... large amount of white powder is observed

The running performance was tested using the apparatus shown in FIG. 1 under the conditions of a temperature of 23 ° C. and a relative humidity of 65%. In FIG. 1, 1 is a crank having a length of 40 mm, 2 is a rotatable guide roller, 3 is a tension detecting device, and 4 is a metal guide post of a commercially available home VTR (maximum roughness Rt = 0.15 μm, average roughness). Ra = 0.008
μm) and a film 12.5 mm in width is passed through the guide roller 2, the tension detecting device 3 and the guide post 4, the contact angle with respect to the guide post 4 is set to 3π / 4 radian, and one end of the film 5 is Connect to crank 1,
A weight 6 having a weight of 50 g was hung on the other end, the crank 1 was rotated at a speed of 8 rpm, and the film 5 was reciprocated 100 times to determine a coefficient of friction (μk). . ○ ・ ・ ・ μk <0.25 △ ・ ・ ・ 0.25 ≦ μk ≦ 0.35 × ・ ・ ・ 0.35 <μk

Electromagnetic Conversion Characteristics Chroma S / N with respect to a standard tape was measured using a TG-7 / 1 type NTSC-TV test signal generator and a 925D / 1 type NTSC color video noise measuring device manufactured by Shibasoku Co., Ltd. And was ranked.・ ・ ・ S / N> +3 dB ・ ・ ・ S / N> +1 dB × S / N <+1 dB The magnetic tape was prepared by coating a base film with a magnetic paint having the following composition. 1. Magnetic powder (γ-Fe ₂ O ₃ ) 2. Binder (polyurethane / nitrocellulose) 3. Curing agent (trifunctional isocyanate) Carbon black 5. Abrasive (alumina) 6. 6. Lubricants (stearic acid / isobutyl stearate) A solvent (methyl ethyl ketone / toluene / cyclohexanone) was dried and applied to a thickness of 5 μm, dried, supercalendered, and thermally cured. The obtained film was slit to a width of 1/2 inch to prepare a VHS video tape.

Average roughness (Ra) Using a surface roughness meter Surfcom 300A manufactured by Tokyo Seimitsu Co., Ltd., needle diameter 2 μm, load 0.07 g, measurement standard length 0.8 m
Indicated by the center line average roughness measured under the conditions of m and cutoff 0.08 mm.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

[Table 3]

As is clear from the above table, Examples 1 to 3 satisfying the requirements of the present invention are excellent in both running properties and electromagnetic conversion properties, and are also extremely excellent in calendar scraping properties. On the other hand, in Comparative Example 4 having no A layer substantially not containing particles having a projection forming ability and Comparative Example 1 substantially containing particles having a projection forming ability in an A layer, running property and electromagnetic conversion were not improved. It can be seen that the properties are excellent, but the calendering properties are poor. In addition, it can be seen that Comparative Example 3 in which the layer B does not substantially contain particles having the ability to form protrusions has poor running properties. Further, it can be seen that in Comparative Example 2 in which particles having an average particle diameter exceeding two-thirds of the average particle diameter of the particles added to the B layer were added to the C layer, the electromagnetic conversion characteristics were poor. Further, in Comparative Examples 5 and 6, which do not have the thin intermediate layer (layer B) to which the particles having substantial projection-forming ability are added, either the running property or the electromagnetic conversion characteristic is poor. .

[0037]

According to the composite oriented polyester film of the present invention, in addition to having a protective layer (A layer) substantially free of particles having a projection-forming ability, particles having a projection-forming ability are substantially contained. , Only the projections that are hard to be removed in the calendering step are formed uniformly and at high density on the film surface. Therefore, for example, a magnetic tape made of the polyester film has excellent electromagnetic conversion characteristics and running properties, and has the effect of significantly reducing the generation of white powder in the calendering step, and exhibits excellent characteristics as a film for a magnetic recording medium. I do.

As described above, the main use of the composite oriented polyester film of the present invention is for magnetic recording media, but other uses, such as graphics, stamping foils, electric insulating materials, derivatives for capacitors, packaging, flexible Wear resistance of printed circuit boards, etc.
It is effectively used for applications where runnability is a problem.

[Brief description of the drawings]

FIG. 1 is a schematic view of a tester for measuring the running property of a film.

FIG. 2 is a schematic view showing an example of a composite oriented polyester film.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Crank 2 Guide roller 3 Tension detector 4 Guide post 5 Composite orientation polyester film 6 Weight 7 A layer 8 B layer 9 C layer 10 Inactive particles 11 Inactive particles

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-31859 (JP, A) JP-A-4-301447 (JP, A) JP-A-63-42862 (JP, A) JP-A-60-1985 254415 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B32B 1/00-35/00

Claims (2)

(57) [Claims] A composite oriented polyester film comprising at least three layers, wherein one of the outermost layers (A
Contains no particles having substantial projections forming ability in the resin constituting the layer), it contains particles having substantial projections forming ability in the layer (B layer) adjacent to the A layer, adjacent to the B layer A layer and below
In the outer layer (C layer), particles having substantial projection forming ability
Not contained or average of particles contained in layer B
The average particle size of two thirds or less of the largest particle size
A composite oriented polyester film , comprising particles having an average roughness of the surface opposite to the surface of the layer A, the average roughness of which is not more than two-thirds of the average roughness of the surface of the layer A. 2. A composite oriented polyester film comprising three layers, A layer, B layer and C layer, having a substantial projection forming ability in a resin constituting one of the outermost layers (A layer). The layer adjacent to the layer A (layer B) does not contain particles, but contains particles having a substantial protrusion forming ability, and the layer adjacent to the layer B
Layer (C layer) other than layer A has substantial protrusion forming ability
Particles that do not contain
Average of two-thirds or less of the largest average particle size
The average roughness of the surface of the outermost layer (C layer) other than the A layer adjacent to the B layer containing particles having a particle diameter is not more than two thirds of the average roughness of the surface of the A layer. A composite oriented polyester film characterized by the following.