JP3575701B2 - Magnetic recording tape - Google Patents

Description

【表２】

【００４９】
【発明の効果】
特殊な積層フィルムを用いて、テープの構成、各層厚さなどを特定範囲としたため、テープ端面からの粉落ちがなくなり、ドロップアウト特性に優れた磁気記録テープが完成したものである。[0001]
[Industrial applications]
The present invention relates to a magnetic recording tape, particularly to a magnetic recording tape suitably used for a W-VHS system or the like.
[0002]
[Prior art]
As a magnetic recording tape, a tape in which a magnetic layer is provided on one side of a laminated film is known (for example, JP-A-3-207018).
[0003]
[Problems to be solved by the invention]
However, the demand for high-density recording and high image quality of magnetic recording tapes has been increasing more and more in recent years. In a recording method typified by W-VHS or digital tape, the magnetic head also rotates at high speed, and the Since a load is applied to the tape, and high-density recording is performed, even small shavings and dust generated from the tape end surface during traveling, etc., will result in serious recording loss (dropout). The problem that satisfactory dropout characteristics cannot be obtained has become apparent.
[0004]
It is an object of the present invention to improve such a problem and to provide a magnetic recording tape capable of achieving these high density and dropout characteristics required for a high-quality tape.
[0005]
[Means for Solving the Problems]
Layer (B layer) made of polyesterParticles having an average particle diameter d of 0.02 to 1 μmLayer (A layer) made of a polyester composition containing 0.05 to 1% by weight ofLayer 2Axial oriented polyester filmB layer surfaceIn addition, a nonmagnetic layer is provided with a thickness tn, and further a thickness tm is formed thereover.Coating mold thinA magnetic recording tape provided with a film magnetic layer, wherein the laminated thickness t of the layer A is 0.1 to 3 μm and tm is 0.1 to 1.5 μm, Tn is 0.5 to 5 μm,Tm / t is 0.05-8, tn / t is 1~ 20 ofIt is a magnetic recording tape characterized by being within the range.
Further, a layer (layer A) made of a polyester composition containing particles having an average particle diameter d of 0.02 to 1 μm and containing 0.05 to 1% by weight was laminated on both surfaces of the layer (layer B) made of polyester. A magnetic recording tape in which a nonmagnetic layer is provided with a thickness of tn on one side of a biaxially oriented polyester film having a three-layer structure, and a coating type thin film magnetic layer having a thickness of tm is further provided thereon. The thickness t of the laminate is in the range of 0.1 to 3 μm, tm of 0.1 to 1.5 μm, tn of 0.5 to 5 μm, tm / t of 0.05 to 8, and tn / t of 1 to 20. The magnetic recording tape is characterized in that:
[0006]
Base layer of base film (hereinafter referred to as film) constituting tape of the present invention(B layer)The polyester is not particularly limited, but when at least one structural unit selected from the group consisting of ethylene terephthalate and ethylene 2,6-naphthalate is used as a main component, the dropout characteristics are further improved. desirable.
[0007]
DepartureMing tapeThe constituent film is a layer (B layer) made of the above polyester,Average particle size d of 0.02 to 1 μmLayer 2 composed of a layer (layer A) composed of a polyester composition containing 0.05 to 1% by weight of particles 2Layer 2Axial oriented polyester filmA layer (layer A) composed of a polyester composition containing 0.05 to 1% by weight of particles having an average particle diameter d of 0.02 to 1 μm is laminated on both surfaces of a layer composed of polyester or a layer (layer B) composed of polyester. Oriented biaxially oriented polyester film with three layersIn Although,The laminated partThe type of the polyester of the (A layer) is not particularly limited, either.Part (layer B)It may be the same or different from the polyester. The laminated portion (layer A)) Is, 2LayeredIf, Is located on the side where the non-magnetic layer and the magnetic layer are not provided,Thin from the cross-sectional structure of the filmLayer.3LayeredIf that tableLayer productRefers to the layer part.
This stackPart (layer A)When the polyester used is crystalline, the dropout characteristics are further improved, which is desirable. The crystallinity as referred to herein indicates that the material is not amorphous, and quantitatively, the cold crystallization temperature Tcc is detected by a differential scanning calorimeter, and the crystallization parameter ΔTcg is 150 ° C. or less. Things. Further, when the heat of fusion (change in enthalpy of fusion) measured by a differential scanning calorimeter shows a crystallinity of 7.5 cal / g or more, dropout characteristics are further improved, which is very desirable. In particular, when at least one structural unit selected from ethylene terephthalate and ethylene 2,6-naphthalate units is used as a main component, the dropout characteristics are further improved, which is preferable. In addition, two or more polyesters may be mixed or a copolymer may be used within a range not to impair the present invention.
[0008]
Construct the present inventionRujiAxis arrangementDirectionFilmAt, The laminated part(A layer)Is required to be 0.1 to 3 μm, preferably 0.1 to 2.5 μm, and more preferably 0.1 to 2 μm. It is not preferable that t is thinner than the above range, or conversely, thicker, since the dropout characteristics become poor.
[0009]
The laminated portion (Particles to be contained in layer A)Is that if the average particle size d is 0.02 to 1 μmAlthough not particularly limited, inorganic particles such as alumina, silica, and calcium carbonate, and organic particles such as polydivinylbenzene, unsaturated polyester, and cross-linked polystyrene are used. Particularly, in the case of the organic particles and the tape layer configuration proposed by the present invention, the dropout characteristics are particularly good, which is desirable.
Further, its content is 0.05 to 1 weight based on the whole laminated portion.%,Preferably,0.07-1% by weight, especially 0.1-1% by weight% And thisIn such a case, the dropout characteristics are further improved, which is desirable. Here, the types and diameters of the particles may be two or more, but the total amount is desirably within the above range. Average particle size of the contained particles (diameter) D is0.02 to 1 μm, particularly 0.07 to 0.8 μm, and further 0.1 to 1 μmAnd thisIn this case, the dropout characteristics are further improved, which is desirable.
[0010]
In the film constituting the present invention, the ratio of the average particle diameter d of the particles contained in the laminated portion of the film to the laminated thickness t, t / d is 0.1 to 10, particularly 0.5 to 5 This is desirable because the dropout characteristics are further improved.
[0011]
In the laminated portion of the mixture, the number of dispersion components satisfying the relationship of 0.1 ≦ t / d ≦ 10 is 3 × 10³~ 8 × 10⁷Pieces / mm²Is preferable because the dropout characteristics are further improved.
[0012]
The film constituting the present invention has a difference between the surface peak count Pc1 in the vertical direction and the surface roughness Pc2 in the horizontal direction, Pc2−Pc1 of the laminated surface, of 10 to 150 / mm, preferably 20 to 120 / mm. It is more preferable that the drop-out characteristics be further improved when the number is 30 to 100 pieces / mm.
[0013]
The difference between the surface roughness Ra1 in the vertical direction and the surface roughness Ra2 in the horizontal direction, Ra2-Ra1 is 1 to 10 nm, preferably 1 to 8 nm, and more preferably 1.5 to 5 nm, the dropout characteristics are more excellent. Is desirable.
[0014]
In addition, when the particles are also contained in the base layer portion, particularly when the film is contained in an amount of 0.01 to 1% by weight with respect to the whole base layer portion, the drop-out characteristics are further improved, which is desirable.
[0015]
Further, the film constituting the present invention has a total reflection Raman crystallization index of 20 cm on the surface of the laminated portion.^-1Below, preferably 18cm^-1Below, further 17cm^-1The following cases are highly desirable because the dropout characteristics are further improved.
[0016]
Although the surface particle concentration ratio measured by the secondary ion mass spectrum of the laminated portion of the film constituting the present invention is not particularly limited, the surface particle concentration ratio on the polyester A surface is 1/10 or less, particularly 1/50 or less. In this case, dropout characteristics are further improved, which is particularly desirable.
[0017]
The thickness of the film constituting the present invention is not particularly limited. However, when the thickness is 2 to 25 μm, particularly 2 to 18 μm, the dropout characteristics are further improved, and it is desirable from the viewpoint of reducing the size of the tape. the filmIs a two-layer configurationOr 3It is a layer configuration.
[0018]
In the tape of the present invention, a nonmagnetic layer is provided on one side of the above-mentioned laminated film, and a magnetic layer is further provided thereon. When the film has a two-layer structure, a magnetic layer is provided on the surface opposite to the laminated part.You. DoIn terms of dropout characteristicsIt is.The composition of the non-magnetic layer is not particularly limited, but a material in which a thermosetting resin, a high energy ray-curable resin, or the like contains an inorganic fine powder, such as silica, alumina, or titanium dioxide, is used. Here, the ratio of the thickness tn of the nonmagnetic layer to the thickness t of the laminated film, tn / t, is 1-20, preferably 1-10, more preferablyMore preferably, it must be in the range of 2 to 8. If the value of tn / t is smaller than the above range or larger than the above range, the dropout characteristics become poor, which is not preferable.
Further, tn is 0.5 to 5 μm, particularly 0.8 to 4 μm.mBetter drop-out characteristicsYou.The type of magnetic layer on the non-magnetic layer is a so-called coating type in which magnetic powder is applied together with a binder.It is. MagneticApply to withstand high-speed rotation of the air headType.
The type of the magnetic powder is not particularly limited, and iron oxide, chromium oxide, cobalt-coated iron oxide, and metals such as iron, cobalt, iron-cobalt, iron-cobalt-nickel, and cobalt-nickel, and alloys thereof are preferably used. However, metals or their alloys are particularly preferred over oxides. The binder constituting the magnetic layer is not particularly limited, but is preferably a thermosetting resin-based, high-energy ray-curable binder, and may contain a dispersant, a lubricant, an antistatic agent, and the like as other additives. . For example, a vinyl chloride / vinyl acetate / vinyl alcohol copolymer, polyurethane, polyisocyanate, or a mixture thereof is preferably used.
Here, the thickness tm of the magnetic layer needs to be 0.1 to 1.5 μm, preferably 0.2 to 1.3 μm, and more preferably 0.2 to 1.2 μm. If tm is larger or smaller than the above range, the dropout characteristics become poor, which is not preferable. Further, the ratio of tm to the film lamination thickness t, tm / t, needs to be in the range of 0.05 to 8, preferably 0.1 to 7, and more preferably 0.2 to 6. If tm / t is smaller or larger than the above range, the dropout characteristics become poor, which is not preferable.
[0019]
The Young's modulus of the tape in the vertical direction is 500 to 2000 kg / mm.², Preferably 600-1500 kg / mm²Is preferable because the dropout characteristics become particularly good.
[0020]
Further, when the tape is used for the W-VHS system, the width of the tape is set to 12.610 to 12.624 mm, and for the digital system, the width is set to 6.3000 to 6.3125 mm, so that the dropout characteristics are further improved. Is desirable.
[0021]
Next, a method for producing the tape of the present invention will be described.
[0022]
First, as a method of incorporating particles into a predetermined polyester, a method of incorporating particles in a polyester polymerization step, a method of preliminarily polymerizing a polyester substantially containing no particles, and then venting a twin-screw kneader into the particles, etc. The method of kneading using is not particularly limited, but after the particles are contained in a high concentration with a vented twin-screw kneader or the like, the polyester and a polyester substantially containing no particles are appropriately mixed to adjust the concentration. Is effective.
[0023]
Thus, the polyester-A pellets containing the particles are dried and then supplied to a known melt extruder 1, where the polyester B (A and B may be the same or different, and B contains particles. Is supplied to the extruder 2 and the polyester A is laminated on at least one side of the polyester B using a two- or three-layer manifold or a merging block. The sheet of two or three layers is extruded from a die and cooled by a casting roll to make an unstretched film. In this case, a method of stacking using a merging block having a rectangular merging cross section is effective for stably obtaining the relationship between the average particle diameter and the thickness of the present invention.
[0024]
Next, the unstretched film is biaxially stretched and biaxially oriented. As the stretching method, a sequential biaxial stretching method or a simultaneous biaxial stretching method can be used. However, using a sequential biaxial stretching method in which stretching in the longitudinal direction and then in the width direction is performed first, the 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 effective for obtaining a film having the relationship between the thickness and the average particle size, the content, the orientation state in the desired range, and the surface layer particle concentration ratio within the range of the present invention without stretching breakage. The stretching temperature in the longitudinal direction differs depending on the type of polyester and cannot be unconditionally determined, but usually the first stage is in the range of 50 to 130 ° C., and the relationship between the thickness and the average particle size in the range of the present invention, the content, and the preferable range are as follows. It is effective for obtaining a film having an orientation state, an average projection height, and a surface particle concentration ratio. The longitudinal stretching speed is preferably in the range of 5,000 to 50,000% / min. As a stretching method in the width direction, a method using a stenter is generally used. The stretch ratio is suitably in the range of 3.0 to 5.0 times. The stretching speed in the width direction is preferably from 1000 to 20,000% / min, and the temperature is preferably from 80 to 160 ° C. Further, the film once biaxially stretched may be further stretched in at least one direction. Next, this stretched film is heat-treated. In this case, the heat treatment temperature is preferably 170 to 200 ° C., particularly 170 to 190 ° C., and the time is preferably 0.5 to 60 seconds.
[0025]
Next, a non-magnetic layer and a magnetic layer are provided on the laminated biaxially oriented polyester film. The method is not particularly limited and may be performed sequentially, but a method in which a non-magnetic layer and a magnetic layer are simultaneously coated by a die coater is desirable for obtaining the layer configuration of the present invention. The drying step after application is desirably performed at a temperature of 90 to 120 ° C., and the subsequent calendering step may be performed between a metal and a metal roll or between a metal and an elastic roll. The elastic roll includes polyamide or polyester. Are used. The calendering temperature is desirably 40 to 70 ° C. Further, the magnetic layer is cured if necessary, and cut into a predetermined width to obtain the magnetic recording tape of the present invention.
[0026]
[Methods for measuring physical properties and evaluating effects]
The method for measuring the characteristic values and the method for evaluating the effects of the present invention are as follows.
[0027]
(1) Average particle size
The polyester is removed from the film by a plasma low-temperature incineration method (for example, model PR-503 manufactured by Yamato Scientific Co., Ltd.) to expose the particles. Processing conditions are selected such that the polyester is ashed but the particles are not damaged. This is observed with a SEM (scanning electron microscope), and the image of the particles (shading of light generated by the particles) is linked to an image analyzer (for example, QTM900 manufactured by Cambridge Instrument). The average area diameter d is defined as the average particle diameter.
[0028]
(2) Content of particles
A solvent that dissolves the polyester but does not dissolve the particles is selected, the particles are centrifuged from the polyester, and the ratio (% by weight) to the total weight of the particles is defined as the particle content. In some cases, the combined use of infrared spectroscopy is also effective.
[0029]
(3) Crystallization parameter ΔTcg, heat of fusion
The measurement was performed using a DSC (differential scanning calorimeter) Model II manufactured by PerkinElmer. The measurement conditions of DSC are as follows. That is, 10 mg of a sample is set in a DSC device, melted at a temperature of 300 ° C. for 5 minutes, and then rapidly cooled in liquid nitrogen. The quenched sample is heated at a rate of 10 ° C./min, and the glass transition point Tg is detected. The temperature was further increased, and the crystallization exothermic peak temperature from the glassy state was taken as the cold crystallization temperature Tcc. The temperature was further increased, and the heat of fusion was determined from the melting peak. Here, the difference between Tcc and Tg (Tcc−Tg) is defined as a crystallization parameter ΔTcg.
[0030]
(4) Surface molecular orientation (refractive index)
The measurement was performed using an Abbe refractometer with sodium D line (589 nm) as a light source. The measurement was performed at 25 ° C. and 65% RH using methylene iodide as the mounting solution. Assuming that the refractive indices of the polymer in the longitudinal, width, and thickness directions are N1, N2, and N3, the absolute value of (N1-N2) is 0.07 or less, and N3 / [(N1 + N2) / 2] is 0.95 or less. The refractive index may be measured using a laser refractometer. Further, when measurement is difficult by this method, a total reflection laser Raman method can be used. The total reflection Raman spectrum of the laser is measured by a Ramanor U-1000 Raman system manufactured by Jobin-Yvon, and the total reflection Raman spectrum is measured. For example, in the case of PET, 1615 cm^-1(Skeleton vibration of benzene ring) and 1730cm^-1Polarization measurement ratio (YY / XX ratio, etc.) of the band intensity ratio of (stretching vibration of carbonyl group), where YY: detection of Raman light parallel to Y with laser polarization direction Y, XX: laser polarization direction , X can be used to determine that Raman light detection parallel to X) corresponds to the molecular orientation. The biaxial orientation of the polymer can be determined by converting the parameters obtained from the Raman measurement into the refractive index in the longitudinal direction and the width direction, and from the absolute value, the difference, and the like. The measurement conditions in this case are as follows.
[0031]
light source
Argon ion laser (5145A)
Sample setting
The film surface was pressed against a total reflection prism, and the angle of incidence of the laser on the prism (the angle with respect to the film thickness direction) was 60 °.
[0032]
Detector
PM: RCA31034 / Photon Counting System (Hamamatsu C1230) (supply 1600V)
Measurement condition
SLIT 1000μm
LASER 100mW
GATE TIME 1.0 sec
SCAN SPEED 12cm^-1/ Min
SAMPLING INTERVAL 0.2cm^-1
REPEAT TIME 6
(5) Total reflection Raman crystallization index
The total reflection Raman spectrum was measured with a Ramanor U-1000 Raman system manufactured by Jobin-Yvon, and the stretching vibration of the carbonyl group was 1730 cm.^-1Was determined as the total reflection Raman crystallization index of the surface. The measurement conditions are as follows. The measurement depth is about 500 to 1000 angstroms from the surface.
[0033]
light source
Argon ion laser (5145A)
Sample setting
The film surface is pressed against a total reflection prism so that the laser polarization direction (S-polarized light) and the longitudinal direction of the film are parallel to each other, and the angle of incidence of the laser on the prism (the angle with the film thickness direction) is 60.゜
[0034]
Detector
PM: RCA31034 / Photon Counting System (Hamamatsu C1230) (supply 1600V)
Measurement condition
SLIT 1000μm
LASER 100mW
GATE TIME 1.0 sec
SCAN SPEED 12cm^-1/ Min
SAMPLING INTERVAL 0.2cm^-1
REPEAT TIME 6
(6) Center line average surface roughness Ra
The measurement was carried out using a high-precision thin film step measuring device ET-10 manufactured by Kosaka Laboratory. The conditions were as follows, and the value was an average value of 20 measurements.
[0035]
・ Stylus tip radius: 0.5 μm
・ Stylus load: 5mg
・ Measurement length: 1mm
・ Cutoff value: 0.08mm
The definition of Ra is, for example, the one shown in Jiro Nara, “Method of Measuring and Evaluating Surface Roughness” (General Technology Center, 1983).
[0036]
(7) Young's modulus
According to the method specified in JIS-Z-1702, the measurement was performed at 25 ° C. and 65% RH using an Instron type tensile tester.
[0037]
(8) Surface particle concentration ratio
Using the secondary ion mass spectrum (SIMS), the concentration ratio of the highest concentration element among the elements originating from the particles in the film to the carbon element of the polyester is defined as the particle concentration, and the analysis in the thickness direction is performed. The ratio A / B between the particle concentration A at the outermost layer particle concentration (point at depth 0) measured by SIMS and the highest concentration B obtained by continuing the analysis in the depth direction was defined as the surface layer concentration ratio. The measuring device and conditions are as follows. The measuring device and conditions are as follows.
[0038]
measuring device
Secondary ion mass spectrometer (SIMS)
A-DIDA3000 manufactured by Atomika, West Germany
Measurement condition
Primary ion species: O₂ ⁺
Primary ion acceleration voltage: 12 KV
Primary ion current: 200 nA
Raster area: 400μm □
Analysis area: Gate 30%
Measurement vacuum: 6.0 × 10^-9Torr
E-GUN: 0.5KV-3.0A
(9) Layer thickness of polyester A layer
Using a secondary ion mass spectrometer (SIMS), the concentration ratio (M) of the element originating from the highest concentration particle to the carbon element of the polyester among the particles in the film having a depth of 3000 nm from the surface layer.⁺/ C⁺) Is defined as the particle concentration, and analysis in the thickness direction is performed 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 with distance from the surface. In the case of the film of the present invention, the particle concentration which has once reached the maximum value starts to decrease again. Based on this concentration distribution curve, the depth at which the surface layer particle concentration was の of the local maximum value (this depth was deeper than the local maximum value) was determined and defined as the lamination thickness. The conditions are as follows.
[0039]
(1) Measurement device
Secondary ion mass spectrometer (SIMS)
A-DIDA3000 manufactured by Atomika, West Germany
(2) Measurement conditions
Primary ion species: O₂ ⁺
Primary ion acceleration voltage: 12 KV
Primary ion current: 200 nA
Raster area: 400 μm □
Analysis area: Gate 30%
Measurement vacuum degree: 5.0 × 10^-9Torr
E-GUN: 0.5KV-3.0A
In the case of crosslinked polymer particles, it is difficult to measure by SIMS. Therefore, while etching from the surface, a depth profile similar to the above is measured by XPS (X-ray photoelectron spectroscopy), IR (infrared spectroscopy), etc. You may ask.
[0040]
The most common method for determining the lamination thickness is by observing the interface from the state of change in particle concentration and the difference in contrast by observing the cross section of the film by (transmission) with an electron microscope such as a transmission electron microscope. This is a method for determining the thickness.
[0041]
(10) Nonmagnetic layer thickness tn, thin film magnetic layer thickness tm
In the observation with the transmission microscope, the interface was recognized from the difference in contrast between the magnetic powder and the non-magnetic powder, and the thickness was determined.
[0042]
(11) Surface peak count Pc
The measurement was performed by connecting a signal analysis device manufactured by Kosaka Laboratory to a high-precision thin film step measuring device ET-10 manufactured by Kosaka Laboratory. The film sample was stuck on a glass-made glass sample base and the ridge line was measured under the following measurement conditions. Pc was a peak count level parallel to the average line (center line) of the roughness curve and separated by 0.01 μm. Between two points where the curve intersects the average line with the peak count level, and when one or more points intersect with the upper peak count are defined as one peak, the number of peaks is determined between the measurement lengths. Was. The measurement was performed 10 times, and the average value was defined as Pc.
[0043]
・ Stylus tip radius: 0.5 μm
・ Measurement speed: 4 μm / sec
・ Stylus load: 5mg
・ Cutoff value: 0.08mm
-Height direction magnification: 100000 times
・ Measuring surface direction magnification: 1000 times
・ Measurement distance: 1mm
(12) Dropout characteristics
A predetermined cassette incorporating a magnetic recording tape is set in a VTR (JVC HR-W1 or Matsushita Electric Digital VTR: D-3), and PLAY / REW for 2 hours is repeated 50 times, and dropout is measured. A dropout at which the output drops by 6 dB or more over 2 μsec was measured. When the number is 0 to 10 pieces / minute, rank 5, 10 to 20 pieces / minute, 4, 20 to 30 pieces / minute, 3, 30 to 40 pieces / minute, and more than 40 pieces / minute It was determined to be rank 1. Ranks 4 or 5 are practically usable.
[0044]
【Example】
The present invention will be described based on examples.
[0045]
Example 1~ 4, Comparative Examples 1 to 8
Using a vent-type kneader having a twin screw, a polymer was prepared by adding a certain amount of particles having different particle diameters to polyethylene terephthalate (PET) and polyethylene-2,6-naphthalate (PEN). Further, PET and PEN containing substantially no particles were produced by a conventional method. These chips were appropriately mixed to prepare a base layer portion (polyester B) and a polymer for a laminated portion (polyester A). Each of these polymers was dried under reduced pressure (3 Torr) at 180 ° C. for 3 hours, and each was fed to two extruders and melted at 290 ° C., and these polymers were combined into a rectangular confluence block (feed) for two or three layers. And then wound around a casting drum having a surface temperature of 30 ° C. using an electrostatic application casting method to cool and solidify to form an unstretched film having a two- or 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 (140 ° C in the case of PEN). This stretching was performed at a peripheral speed difference between two sets of rolls. This uniaxially stretched film is stretched 4.0 times in the width direction at 100 ° C. at a stretching speed of 5000% / min using a stenter (130 ° C. in the case of PEN), and heat-treated at 200 ° C. for 5 seconds under a constant length. A biaxially oriented laminated polyester film was obtained.
[0046]
A non-magnetic paint and a magnetic paint having the following composition are simultaneously applied to this film by a die coater while changing the film thickness, magnetically oriented, and dried. Furthermore, after calendering at a temperature of 70 ° C. and a linear pressure of 200 kg / cm using a small test calender (steel roll / nylon roll, 5 steps), curing is performed at 70 ° C. for 48 hours. The tape was slit into 6.3 mm and 8 mm, and assembled into a cassette to form a magnetic recording tape.
[0047]
Composition of non-magnetic paint
・ Titanium dioxide fine particles: 100 parts by weight
Esrec A (Sekisui Chemical's vinyl chloride / vinyl acetate copolymer: 10 parts by weight)
・ Nipporan 2304 (Polyurethane elastomer made by Nippon Polyurethane): 10 parts by weight
・ Coronate L (Polyisocyanate manufactured by Nippon Polyurethane): 5 parts by weight
・ Lecithin: 1 part by weight
・ Methyl ethyl ketone: 75 parts by weight
・ Methyl isobutyl ketone: 75 parts by weight
・ Toluene: 75 parts by weight
・ Carbon black: 2 parts by weight
-Lauric acid: 1.5 parts by weight
Composition of magnetic paint
・ Iron (length: 0.3 μm, needle ratio: 10/1, 1800 Oersted)
: 100 parts by weight
Esrec A (Sekisui Chemical's vinyl chloride / vinyl acetate copolymer: 10 parts by weight)
・ Nipporan 2304 (Polyurethane elastomer made by Nippon Polyurethane): 10 parts by weight
・ Coronate L (Polyisocyanate manufactured by Nippon Polyurethane): 5 parts by weight
・ Lecithin: 1 part by weight
・ Methyl ethyl ketone: 75 parts by weight
・ Methyl isobutyl ketone: 75 parts by weight
・ Toluene: 75 parts by weight
・ Carbon black: 2 parts by weight
-Lauric acid: 1.5 parts by weight
The parameters and performance of these magnetic recording tapes according to the present invention are as shown in Tables 1 and 2. When the parameters of the present invention are within the range, the magnetic tape has excellent dropout characteristics. If not, it turns out that the purpose cannot be achieved.
[0048]
[Table 1]

[Table 2]

[0049]
【The invention's effect】
By using a special laminated film to set the tape configuration, the thickness of each layer, and the like in a specific range, powder dropping from the tape end surface is eliminated, and a magnetic recording tape excellent in dropout characteristics is completed.

Claims (5)

The layer (B layer) made of polyester, 2-layer average particle diameter d is the layer composed of polyester composition containing the particle element of 0.02 to 1 .mu.m 0.05 to 1 wt% (A layer) are stacked configuration the B layer surface of the biaxially oriented polyester film, a nonmagnetic layer provided with a thickness tn, a further magnetic recording tape having a coating-type thin film magnetic layer having a thickness of tm thereon, laminating the a layer the thickness t of 0.1 to 3 m, tm is 0.1 to 1.5 [mu] m, tn is 0.5 to 5 [mu] m, one or, tm / t is 0.05 to 8, in the range of tn / t is 1 to 20 A magnetic recording tape, comprising: Three layers in which a layer (layer A) composed of a polyester composition containing 0.05 to 1% by weight of particles having an average particle diameter d of 0.02 to 1 μm is laminated on both sides of a layer (layer B) composed of polyester A magnetic recording tape comprising: a non-magnetic layer provided on one side of a biaxially oriented polyester film having a thickness of tn; and a coating type thin-film magnetic layer having a thickness of tm on the non-magnetic layer. The thickness t is 0.1 to 3 μm, tm is 0.1 to 1.5 μm, tn is 0.5 to 5 μm, tm / t is 0.05 to 8, and tn / t is in the range of 1 to 20. A magnetic recording tape, characterized in that: Layer average particle diameter d and t ratio of particles contained in (A layer) having a thickness of t, No placing serial to claim 1 or 2, characterized in that t / d is in the range of 0.1 to 10 Magnetic recording tape. The amount of particles contained in the layer (A layer) of thickness t with respect to the whole of the layer, the magnetic mounting serial to claim 1, characterized in that from 0.1 to 1 wt% Recording tape. The magnetic recording tape according to any one of claims 1 to 4, characterized in that used for the digital signal recording and reproducing system.