JPH05298660A - Pancake - Google Patents

Abstract

PURPOSE:To prevent the pancake from shifting in stage while maintaining superior characteristics as a magnetic tape by incorporating particles in at least the outermost layer on one surface side of laminate structure consisting of >=3 layers so that the relation between specific mean particle size and the layer thickness of the outermost layer is satisfied, and specifying the large/small relation in dynamic friction coefficient between both surfaces. CONSTITUTION:The pancake is formed by winding a base film with a magnetic tape provided with a coating type magnetic layer and the base film is a polyester film in laminate structure of at least >=3 layers which are extruded together; and the layer on at least one surface side contains the particles, 0.1<=t/d<=10 holds for the mean particle size (d) (nm) of the particles and the layer thickness (t) (nm) of the layer, and the slide friction coefficient of a magnetic surface to metal is larger than the dynamic friction coefficient of the opposite surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pancake having a support film provided with a coating type magnetic layer and wound with a magnetic tape.

[0002]

2. Description of the Related Art A support film of a magnetic tape having a support film provided with a coating type magnetic layer is a biaxially oriented laminated film, for example, polyester containing substantially spherical silica particles derived from colloidal silica. A biaxially oriented laminated polyester film is known (for example, JP-A-59-171623).

However, with the increase in the process speed of the film processing process, particularly the magnetic layer coating / calendering / winding process in a magnetic medium application, the cassette assembling process, etc., the film surface, especially minute irregularities, is formed on the film by the contacting rolls or guides. There was a drawback that the film surface was easily scraped off. Further, the conventional one has a drawback that the image quality, that is, the S / N (signal / noise ratio) is insufficient because the image quality is deteriorated during dubbing as the dubbing speed is increased by high-speed magnetic field transfer.

In order to eliminate such drawbacks with respect to abrasion resistance and electromagnetic conversion characteristics, the outermost layer of the laminated film is made to be a thin layer, and particles having a relatively large particle diameter relative to the layer thickness are contained. There is proposed a biaxially oriented laminated film in which minute projections which are difficult to be scraped off are formed on the film surface by making the particle diameters of the particles and particles have a specific relationship (Japanese Patent Laid-Open No. 2-77431).

[0005]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention
To further improve the technology proposed in Japanese Patent No. 77431,
In particular, in a pancake in which a biaxially oriented laminated polyester film is used as a support film and a magnetic tape having a coating type magnetic layer provided on the support film is wound, a pancake that does not cause misalignment (step misalignment) during transportation etc. is provided. The purpose is to

[0006]

The pancake of the present invention for this purpose has a support film having a thickness of 0.1 to 5 μm.
In a pancake wound with a magnetic tape provided with a coating type magnetic layer, the support film is a polyester film having a laminated structure of at least three layers coextruded, and particles are provided on at least one surface side of the polyester film. Containing
Average particle diameter d (nm) of the particles and layer thickness t (nm) of the layer
And 0.2 ≦ t / d ≦ 10, and the coefficient of dynamic friction of the magnetic surface with respect to the metal is larger than the coefficient of dynamic friction of the opposite surface.

First, in the pancake of the present invention, the support film of the magnetic tape must have a laminated structure of at least three layers. If there are 3 layers or more, 4 layers will be 5
A layer may be used, but a three-layer structure is preferable because the effect of the present invention is further improved. However, it is difficult to obtain a target coefficient of dynamic friction with respect to a metal and a good step deviation rate in a pancake form in a film having a single-layer or two-layer structure.

The laminated structure of three or more layers is formed by coextrusion. That is, so that the predetermined thickness ratio,
The polymer is laminated in three or more layers by a polymer merging block or a spinneret, discharged into a sheet, and then formed into a film.

Next, in the support film of the present invention, it is preferable that at least one of the layers constituting the support film is biaxially oriented. It is particularly preferable that all layers in the laminated structure of three or more layers are biaxially oriented. It is difficult to satisfy the characteristics of the present invention when all layers are non-oriented or uniaxially oriented.

The polymer constituting the support film of the present invention is polyester, and the polyester is not particularly limited, but ethylene terephthalate, ethylene α, β-bis (2-chlorophenoxy) ethane-4,
It is particularly preferable when at least one structural unit selected from 4'-dicarboxylate and ethylene 2,6-naphthalate units is the main constituent. Of these, polyesters containing ethylene terephthalate as a main constituent are particularly preferable. Incidentally, within the range that does not inhibit the present invention,
Two or more kinds of polyesters may be mixed, or a copolymer polymer may be used.

In the outermost layer on at least one side of the support film having a laminated structure of three or more layers, particles have an average particle diameter d (nm) of the particles and a layer thickness t (nm) of the outermost layer. Is included so that the relation of 0.2d ≦ t ≦ 10d. If t is less than 0.2d, the target dynamic friction coefficient for the metal and the good step deviation rate in the pancake form cannot be obtained, and if t is more than 10d, the desired dynamic friction coefficient and step deviation rate are obtained. In addition to being difficult, the electromagnetic conversion characteristics of a magnetic tape are degraded.

Then, the support film has a thickness of 0.1.
When a magnetic tape having a coating type magnetic layer of ˜5 μm is provided and the magnetic tape is formed into a pancake form, as described above, it is required to have a characteristic that does not cause a deviation (step deviation) during transportation. In order to keep this step deviation rate favorable, the support film in the present invention is formed so that the dynamic friction coefficient of the magnetic surface with respect to the metal is larger than the dynamic friction coefficient of the opposite surface. Further, in the case of a magnetic tape, it is preferable to lower the coefficient of dynamic friction particularly on the surface opposite to the magnetic surface in order to maintain good running properties. In order to achieve both the magnitude relationship of the dynamic friction coefficient of both surfaces and the reduction of the dynamic friction coefficient of the surface opposite to the magnetic surface, it is preferable to control the number of projections on the surface opposite to the magnetic surface within a predetermined range. 3 × 10 ³ -1.
The range of 5 × 10 ⁵ pieces / mm ² is preferable.

Further, in the support film of the present invention, it is preferable that the intermediate layer in the laminated structure of three or more layers contains inorganic particles. In particular, when the outermost layer of the diamagnetic surface also contains particles having the above-mentioned relationship between the average particle diameter and the layer thickness, by doing so, the protrusion forming action of the intermediate layer-containing inorganic particles is reduced to the outermost layer of the thin layer. Also, a protrusion is formed in a form in which the protrusion formed by the outermost layer-containing particles is further added to the protrusion forming surface formed by the inorganic particles, and a desirable protrusion that is less likely to be scraped off and exhibits better traveling performance is formed. Moreover, it becomes easy to specify the magnitude relationship of the dynamic friction coefficients on both sides, and it becomes easy to obtain a good step deviation rate.

Thus, in addition to the outermost layer-containing particles, the intermediate layer-containing inorganic particles also have the effect of forming protrusions. As a result, in the support film of the present invention, the number of protrusions on the diamagnetic surface side of the film surface is within a desired range, that is, 3 x 10 ^{3 to} 1.5 x 10
Easily controlled to ⁵ pieces / mm ² .

When the number of protrusions on the diamagnetic surface side film surface is less than the above range, the coefficient of friction becomes high and it is difficult to obtain good running performance, and it becomes difficult to specify the magnitude relationship of the dynamic friction coefficients on both sides. It becomes difficult to obtain a good step deviation rate. On the contrary, when the number of protrusions is larger than the above range, the film surface becomes brittle and is easily scraped.

The inorganic particles contained in the intermediate layer are not particularly limited, but are preferably at least one selected from calcium carbonate, silica, alumina, zirconia and titanium oxide.

When the intermediate layer-containing inorganic particles are calcium carbonate, the crystal form thereof is preferably calcite type or vaterite type. When the inorganic particles are silica, it is preferably colloidal silica. Further, when the inorganic particles are alumina,
The crystal form is preferably δ type, γ type, θ type, or η type.

In the support film of the present invention, different polymers may be blended within the range not impairing the object of the present invention, and an antioxidant, a heat stabilizer, a lubricant, an ultraviolet absorber. Organic additives such as may be added to the extent that they are usually added.

A magnetic tape is prepared by providing a coating type magnetic layer on such a support film, and a pancake is prepared by winding the magnetic tape. The thickness of the coating type magnetic layer is 0.1 to 0.1 due to the output characteristics of the magnetic tape, the electromagnetic conversion characteristics, etc.
It is set to 5 μm.

The magnetic powder used in the magnetic layer is not particularly limited, but among them, Fe, Co, Fe-Co, Fe-C.
Metals or alloys such as o-Ni, Co-Ni, etc., and A
Alloys with l, Cr, Si and the like are preferably used.

The magnetic powder can be made into a magnetic paint by using various binders, but in general, thermosetting resin binders and high energy ray curable binders are preferable, and other additives such as dispersants, lubricants and antistatics. The agent may be used according to a conventional method. For example, a binder made of vinyl chloride / vinyl acetate / vinyl alcohol copolymer, polyurethane prepolymer and polyisocyanate can be used.

Next, the method for producing the support film, the magnetic tape and the pancake in the present invention will be described.
First, as a method for incorporating particles into the polyester, for example, a method is preferred in which particles are dispersed in a predetermined ratio in ethylene glycol, which is a diol component, and the ethylene glycol is polymerized with a predetermined dicarboxylic acid component. When adding the particles, for example, if the water sol or alcohol sol obtained during the synthesis is added without once drying, the dispersibility of the particles will be very good, and the high-speed scraping property and electromagnetic conversion characteristics will be good. be able to. Further, a method in which an aqueous slurry of particles is directly mixed with a predetermined polyester pellet and supplied to a vent type twin-screw kneading extruder and kneaded into polyester is also very effective in further improving the effect of the present invention. Content of particles,
As a method for adjusting the number of particles, it is effective to prepare a high-concentration particle master by the above method, and dilute it with a polyester that does not substantially contain particles during film formation to adjust the content of particles. ..

Next, using the polyester pellets, a polyester film having a laminated structure of three or more layers is formed. The polyester pellets obtained by the above method are mixed at a predetermined ratio, dried and then fed to a known melt laminating extruder, extruded into a sheet from a slit die, and solidified by cooling on a casting roll. At the very least make an unstretched film. That is, using two or more extruders, three or more layers of manifolds or merging blocks (for example, a merging block having a square merging portion), a film layer forming each outermost layer and a film layer forming an intermediate layer are used. Are laminated, and three or more sheets are extruded from the die and cooled with a casting roll to prepare an unstretched film. In this case, the method of installing a static mixer and a gear pump in the polymer channel is effective. Also, the melting temperature of the extruder for extruding the polymer on the outermost layer side is 5% from the base layer side.
It is effective to lower the temperature by -10 ° C.

Next, the unstretched film is biaxially stretched and biaxially oriented. As a stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used. However, a sequential biaxial stretching method of first stretching in the longitudinal direction and then in the width direction is used, stretching in the longitudinal direction is divided into three or more stages, and the total longitudinal stretching ratio is 3.5 to 6.5 times. The method is particularly preferred. The stretching temperature in the longitudinal direction varies depending on the type of polyester and cannot be generally stated, but usually the first step is 50 to 1
It is effective to set the temperature to 30 ° C. and raise the temperature from the second stage onward. The longitudinal stretching speed is 5000 to 50000% /
The range of minutes is preferred. As a stretching method in the width direction, a method using a stenter is generally used. The draw ratio is 3.0
The range of up to 5.0 times is appropriate. The stretching speed in the width direction is
The range of 1000 to 20000% / min and the temperature of 80 to 160 ° C are suitable. Next, this stretched film is heat-treated. The heat treatment temperature in this case is 170 to 220 ° C., especially 1
The range of 80 to 200 ° C. and the time of 0.2 to 20 seconds are suitable.

Next, a predetermined magnetic layer is applied to this film. The method of applying the magnetic layer can be performed by a known method, and the temperature of the drying step after application is preferably 90 to 120 ° C. At this time, apply a process tension of 1 to 1
It is preferably 5 kg / m, preferably 10 kg / m or less.

The calendering step is performed at a temperature range of 25 to 90 ° C., particularly 40 to 70 ° C., using polyamide or polyester for the elastic roll, and the process tension at that time is 13 kg / m, preferably 8 kg / m or less. Is desirable. Further, after curing the magnetic layer of this film, the original material (wide width) is rolled for 40 to 90 minutes.
It is preferable to heat and leave it in the temperature range of ° C for 24 to 96 hours in order to keep the heat shrinkage rate low. Then, it is slit into a predetermined tape width to obtain a magnetic tape, which is wound to obtain the pancake of the present invention.

[Physical property measuring method and effect evaluating method] The characteristic value measuring method and effect evaluating method of the present invention are as follows. (1) Average particle size and number of particles The polymer is removed from the film by a plasma low temperature ashing method to expose the particles. The processing conditions are such that the polymer is incinerated but the particles are not damaged as much as possible. The particles are observed with a scanning electron microscope (SEM), and the particle image is processed with an image analyzer. The magnification of the SEM is approximately 2000 to 10,000 times, and the visual field for one measurement is appropriately selected from approximately 10 to 50 μm on each side. The volume average diameter d is obtained from the particle diameter and its volume fraction with the number of particles of 5000 or more by changing the observation location. d = Σd _i · Nv _i where d _i is the particle size and Nv _i is the volume fraction thereof. The number of particles is calculated from the volume fraction and converted per mm ² for those satisfying the relationship between the laminated thickness and the average particle diameter. When the particles are organic particles or the like and are significantly damaged by the plasma low temperature ashing method, the following method may be used. Using a transmission electron microscope (TEM), the film cross section is 30
Observe at 00-100,000 times. The section thickness of the TEM is set to about 1000Å, the location is changed and 500 or more visual fields are measured, and the volume average diameter d is obtained from the above formula.

(2) Thickness of laminated polyester layer (thickness of outermost layer: t) Using a secondary ion mass spectrometer (SIMS), the highest thickness among the particles in the film in the depth of 3000 nm from the surface layer The concentration ratio (M ⁺ / C ⁺ ) of the element due to the concentration of particles and the carbon element of polyester is defined as the particle concentration, and the analysis is performed in the thickness direction from the surface to a depth of 3000 nm. In the surface layer, the particle concentration is low due to the interface of the surface, and the particle concentration increases as the distance from the surface increases. In the case of the film of the present invention, the particle concentration once reaching the maximum value starts to decrease again. Based on this concentration distribution curve, the depth at which the surface layer particle concentration becomes ½ of the maximum value (this depth is deeper than the maximum value) was determined and used as the laminated thickness. The conditions are as follows. Measuring instrument Secondary ion mass spectrometer (SIMS) A-DIDA3000 manufactured by ATOMIKA, West Germany Measuring conditions Primary ion species: O ₂ ⁺ Primary ion accelerating voltage: 12KV Primary ion current: 200nA Raster area: 400μm □ Analysis area: Gate 30% Measured vacuum degree: 6.0 × 10 ^-9 Torr E-GUN: 0.5KV-3.0A If the most contained particles in the depth range from the surface layer to 3000 nm are organic polymer particles, SIMS Since it is difficult to measure with XPS (XPS (X
The layer thickness may be obtained by measuring a depth profile similar to the above by line photoelectron spectroscopy), IR (infrared spectroscopy), or the like, or by observing a cross section with an electron microscope or the like, the state of change in particle concentration or polymer It is also possible to recognize the interface from the difference in contrast due to the difference and obtain the laminated thickness. Furthermore, after peeling the laminated polymer, the laminated thickness can be obtained using a thin film step measuring machine.

(3) Number of projections on the film surface The film surface of the film surface was measured using a two-detector type scanning electron microscope [ESM-3200, manufactured by Elionix Co., Ltd.] and a cross-section measuring device [PMS-1, manufactured by Elionix Co., Ltd.]. The measurement value of the height of the projection when scanning is performed with the height of the flat surface set to 0 is sent to an image processing apparatus [IBAS2000, manufactured by Carl Zeiss Co., Ltd.] to reconstruct a film surface projection image on the image processing apparatus. Next, the highest value among the individual projections obtained by binarizing the projections in this surface projection image is taken as the height of the projection, and this is calculated for each projection. This measurement was repeated 500 times at different places, and the number of protrusions was determined using protrusions having a height of 20 nm or more. The magnification of the scanning electron microscope is selected to be 1000 to 8000 times. In some cases, a high-precision optical interference type three-dimensional surface analyzer (WY
KO TOPO-3D, objective lens: 40-200
The height information obtained by using a double high-resolution camera is effective) may be used instead of the value of the SEM.

(4) Dynamic friction coefficient μk Films slit into a tape having a width of 1/2 inch were used at 20 ° C. using a tape running tester SFT-700 type (manufactured by Yokohama System Laboratory Co., Ltd.). The vehicle was run in a 60% RH atmosphere, and the initial coefficient of friction was determined from the following formula (film width was 1/2 inch). μk = 2 / πln (T ₂ / T ₁ ), where T ₁ is the inlet tension and T ₂ is the outlet tension. The guide diameter is 6 mmφ, the guide material is SUS27 (surface roughness 0.2S), the winding angle is 90 °, and the running speed is 3.
It is 3 cm / sec.

(5) Step deviation rate An iron core was inserted into the core of the pancake rolled up to a specified length, and this core rod was vibrated at an amplitude of 50 mm and a frequency of 100 Hz alternately for 5 minutes each vertically and horizontally for a total of 3 hours. After that, observe the pancake, and check the misalignment of the film, which sticks out from the edge and becomes bamboo shoot-shaped. This test was performed on 100 pancakes, and when the step deviation was 2 or less, the step deviation rate was good, and when it was 3 or more, the step deviation rate was determined to be poor.

[0032]

EXAMPLES Next, the embodiments of the present invention will be described based on examples. Examples 1 to 4 and Comparative Examples 1 to 5 Several kinds of particles having different particle diameters were dispersed in ethylene glycol in the form of a slurry, transesterified with dimethyl terephthalate, and then polycondensed to give a predetermined amount of the particles. The contained polyethylene terephthalate (hereinafter abbreviated as PET) was prepared. In addition, PET was produced by a conventional method without containing substantially inert particles. These polymers were mixed in appropriate amounts to adjust the particle concentration, and dried under reduced pressure (3 Torr) at 180 ° C. for 3 hours. With the combinations shown in Table 1, these were fed to two extruders, melted at 290 ° C, and
A rectangular confluent block (feed block) for layers was combined and laminated, and was wound around a casting drum having a surface temperature of 30 ° C. by an electrostatically applied casting method to be cooled and solidified to form an unstretched film having a three-layer structure. .. At this time, the discharge amount of each extruder was adjusted to adjust the total thickness and the thickness of the polyester A layer. This unstretched film was stretched 4.5 times in the longitudinal direction at a temperature of 80 ° C. This stretching was performed by the difference in peripheral speed between the two sets of rolls. This uniaxially stretched film was stretched at a stretching rate of 2000% / min at 100 ° C. in a width direction of 4.0 using a stenter.
The film was double-stretched and heat-treated at 200 ° C. for 5 seconds under a constant length to obtain a biaxially oriented laminated polyester film having a total thickness of 14 μm. All of the laminated constitutions were a three-layer constitution of A layer / B layer / A layer.

A magnetic paint is applied to this film by a gravure roll. The composition of the magnetic paint was adjusted as follows. However, the friction coefficient of the magnetic surface was adjusted by changing the amount of stearic acid.・ Fe 100 parts Average particle size Length: 0.3 μm Needle ratio: 10/1 Coercive force 2000 Oe ・ Polyurethane resin 15 parts ・ Vinyl chloride / vinyl acetate copolymer 5 parts ・ Nitrocellulose resin 5 parts ・ Aluminum oxide Powder 3 parts Average particle size: 0.3 μm Carbon black 1 part Lecithin 2 parts Methyl ethyl ketone 100 parts Methyl isobutyl ketone 100 parts Toluene 100 parts Stearic acid 2 parts

After the above composition was mixed and dispersed by a ball mill for 48 hours, 6 parts of a curing agent was added and the resulting kneaded product was filtered through a filter to prepare a magnetic coating solution, which was coated on the film and magnetic field orientation was performed. And dried at 110 ° C (process tension up to this point is 10 kg / m), and then calendered (steel roll / nylon roll, 5 steps) at temperature 70 ° C, linear pressure 200 kg / cm 2, process tension 7 kg / m. After calendering, it was wound into a roll and cured at 70 ° C. for 24 hours to obtain a raw magnetic recording tape having a width of 1 m. This raw fabric was slit into a tape having a width of 1/2 inch with a micro slitter to prepare a pancake in which a tape having a length of 20000 m was wound. Comparative Examples 3 to 5 were prepared by using the film used in Example 1 and changing the thickness and composition of the magnetic layer. The misalignment rates of these pancakes are as shown in Table 2, and those satisfying the requirements of the present invention were good, but those not satisfying the requirements were poor.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

According to the pancake of the present invention, at least one outermost layer of the laminated structure of at least three layers,
Particles were included so as to satisfy the relationship between the specific particle average particle diameter and the layer thickness of the outermost layer, and the magnitude relationship of the dynamic friction coefficients on both sides was specified, so while maintaining excellent properties as a magnetic tape, the bread It is possible to prevent misalignment of the cake.

Claims (4)

[Claims] 1. A support film having a thickness of 0.1 to 5 μm.
In a pancake wound with a magnetic tape provided with a coating type magnetic layer, the support film is a polyester film having a laminated structure of at least three layers coextruded, and particles are provided on at least one surface side of the polyester film. Containing
Average particle diameter d (nm) of the particles and layer thickness t (nm) of the layer
Pancake characterized in that the relationship with 0.2 ≦ t / d ≦ 10, and the coefficient of dynamic friction of the magnetic surface with respect to the metal is larger than the coefficient of dynamic friction of the opposite surface. 2. The pancake according to claim 1, wherein the number of protrusions on the surface opposite to the magnetic surface of the magnetic tape is 3 × 10 ^{3 to} 1.5 × 10 ⁵ pieces / mm ² . 3. The pancake according to claim 1 or 2, wherein inorganic particles are contained in an intermediate layer of a support film having a laminated structure of three or more layers which is a support for the magnetic tape. 4. The pancake according to claim 3, wherein the inorganic particles in the intermediate layer are at least one selected from calcium carbonate, silica, zirconia, and titanium oxide.