JPH03209623A - Memory tape - Google Patents

Abstract

PURPOSE:To obtain the memory tape which is excellent in scratch resistance and output characteristics by using thermoplastic resins contg. particles and specifying the relation between the size of the particles and the thickness of a film and the content. CONSTITUTION:The memory tape consists of a base material film and a magnetic layer. The base material film is a laminated film formed by laminating a layer (layer A) consisting of the thermoplastic resin A contg. the particles on a layer (layer B) consisting of the thermoplastic resin B. The surface roughness Ra of this layer A is <=75nm and the ratio Rt/Ra between the max. height Rt and Ra is <=8. The average grain size (d) of the particles incorporated into the layer A is 10 to 1,000nm and the content of the particles in the layer A is 1 to 40wt.%. The ratio t/d between the thickness (t) of the layer A and the average grain sized (d) of the particles is 0.1 to 3. The scratch resistance and output characteristics are inferior and such is undesirable if these ranges are exceeded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to memory tapes.

[Prior Art] Memory tapes are mainly used for data storage in computers, etc., are used repeatedly among magnetic recording media, and are usually used at high speeds due to sequential (continuous physical position) recording. It is something that

As such magnetic recording media such as memory tapes, there are known magnetic recording media in which an oxide-coated magnetic layer is provided on a polyester film (for example, Japanese Patent Laid-Open No. 61-269
Publication No. 33, etc.).

[Problems to be Solved by the Invention] However, the above-mentioned conventional memory tapes have a drawback in that the tape surface is scratched by the rolls and guides that come into contact with the memory tapes because the memory tapes are often used at high speeds. In addition, the conventional type had a drawback that the output characteristics were low when recording was repeatedly written and reproduced, resulting in an insufficient S/N (signal/noise ratio).

The present invention solves these problems and has excellent scratch resistance, especially in high-speed processes.
The purpose of the present invention is to provide a memory tape (hereinafter referred to as having excellent output characteristics) that can withstand repeated recording and playback.

[Means for Solving the Problems] The present invention provides a memory tape having a magnetic layer provided on at least one side of a base film, wherein the base film has at least one layer (B layer) made of thermoplastic resin B. It is a laminated film in which a layer (A layer) made of thermoplastic resin A containing particles is laminated on one side, and the surface roughness Ra of the A layer is 75n.
m or less, the ratio of maximum height Rt and Ra is Rt/Ra or 8.
0 or less, and the average particle diameter d of the particles contained in the A layer is 1
0 to 11000n, the content of the particles in A layer is 1 to
40% by weight, the ratio t of the thickness t of the A layer and the average particle size d of the particles
/d is 0. The present invention relates to a memory tape characterized by numbers 1 to 3.

The thermoplastic resins A and B constituting the base film of the present invention may be the same or different types (polyester,
Polyolefins, polyamides, polyphenylene sulfides, etc. are not particularly limited, but polyesters, especially ethylene terephthalate, ethylene α, β
- Scratch resistance is even better when the main constituent is at least one structural unit selected from bis(2-chlorophenoxy)ethane-4,4'-dicarboxylate and ethylene 2,6-naphthalate units. Therefore, it is desirable. Further, it is extremely desirable that the thermoplastic resin A constituting the present invention is crystalline, since this provides even better scratch resistance. Crystallinity here indicates that it is not so-called amorphous, and quantitatively, the cold crystallization temperature Tcc in the crystallization parameter is detected, and the crystallization parameter ΔTcg is 150°C or less. . Further, it is extremely desirable that the crystallinity has a heat of fusion (change in enthalpy of fusion) of 7.5 cal/g or more as measured by a differential scanning calorimeter because the scratch resistance will be even better. Furthermore, polyester containing ethylene terephthalate as a main component is particularly desirable because it provides even better scratch resistance.

In addition, within the range that does not impede the present invention, thermoplastic resin A,
B may be mixed with other thermoplastic resins or may be a copolymer. Furthermore, organic additives such as antioxidants, heat stabilizers, lubricants, and ultraviolet absorbers may be added to the thermoplastic resins A and B to the extent that they are usually added, within a range that does not impede the purpose of the present invention. .

The average particle diameter d of the particles in layer A of the base film constituting the present invention is 10 to 110 from the viewpoint of scratch resistance and output characteristics.
If a magnetic layer is provided on the A layer side, the thickness is preferably 10 to 50 Q nm, and if no magnetic layer is provided, it is preferably 30 to 11,000 nm.

Further, the content of particles in the base film A layer of the present invention is 1 to
It is necessary that the amount is 40% by weight, preferably 2 to 30% by weight, and more preferably 3 to 20% by weight. If the content is more than the above range, the output characteristics will not be satisfactory, and if the content is less than the above range, the scratch resistance will be poor, which is not preferable.

Further, the ratio t/d between the thickness t of the base film A layer of the present invention and the average particle diameter d of particles contained in the A layer is 0.1 to 3, preferably 0. 2 to 2.0, more preferably 0. 3
It is necessary that it is in the range of ~1.5. If t/d is smaller than the above range, the scratch resistance will be poor, whereas if it is larger, the output characteristics will be poor, which is not preferable.

Furthermore, the B layer of the present invention does not particularly need to contain particles, but the average particle size is 5 to 500 nm, particularly 10 to 4 nm.
0.001 to 0.5% by weight, especially 0.00nm particles.
A content of 0.005 to 0.3% by weight is desirable because scratch resistance and output characteristics become even better.

The particles contained in the thermoplastic resin A of the present invention have a particle size ratio (
Particles having a particle length (longer axis/breadth axis) of 1.0 to 1.3, particularly spherical particles, are preferable because they provide even better scratch resistance and output characteristics.

Further, the particles have a single particle index of 0.0 in the base film.
7 or more, preferably 0. A value of 9 or more is particularly desirable because scratch resistance and output characteristics are even better. Furthermore, the particles have a relative standard deviation of particle size of 0.6 or less, preferably 0.6 or less. A value of 5 or less is desirable because scratch resistance and output characteristics become even better.

The type of particles used in the present invention is not particularly limited, but includes substantially spherical silica particles derived from colloidal silica, particles made of crosslinked polymers (for example, crosslinked polystyrene), etc. Measured using a thermogravimetric analyzer inside.

In the case of crosslinked polymer particles whose degree of crosslinking is increased until the temperature increase rate (20°C/min) is 380°C or higher, scratch resistance,
This is particularly desirable since the output characteristics will be even better. In addition, in the case of spherical silica derived from colloidal silica, substantially spherical silica produced by an alkoxide method and having a low sodium content is particularly desirable because the scratch resistance and output characteristics are even better. . However, other particles, such as calcium carbonate, titanium dioxide, alumina, etc., can also be used satisfactorily by appropriately controlling the ratio of the thickness t of the thermoplastic resin A layer to the average particle diameter d.

The substrate constituting the present invention is a biaxially oriented laminated film made of the above-mentioned composition, and a negative-axis or non-oriented film is not preferable because the scratch resistance will be poor. The degree of this orientation is not particularly limited, but if the Young's modulus, which is a measure of the degree of molecular orientation of the polymer, is 350 kg/mm2 or more in both the longitudinal and width directions, the output characteristics and scratch resistance will be even better. This is extremely desirable. The upper limit of Young's modulus, which is a measure of the degree of molecular orientation, is not particularly limited, but is usually 1500 kg/f.
11[n2 is the manufacturing limit.

It is particularly desirable that the total reflection Raman crystallization index of the surface of the A layer of the base film constituting the present invention be 20 cm-'' or less, since scratch resistance and output characteristics will be even better.

The present invention is a magnetic recording medium comprising a magnetic layer provided on at least one side of the base film. The magnetic powder used is not particularly limited, but ferromagnetic powder, especially γ-Fe2O
3, co-containing 7-Fe2O3, Fe3O4, co-containing F
e3O4, CrO2, etc. are preferably used.

Magnetic powder can be made into a magnetic paint using various binders, but thermosetting resin binders and radiation curing binders are generally preferred, and other additives such as dispersants, lubricants, and antistatic agents can be added according to conventional methods. May be used. For example, binders made of vinyl chloride/vinyl acetate/vinyl alcohol copolymers, polyurethane prepolymers, and polyisocyanates can be used.

The thickness tM of the magnetic layer is not particularly limited, but the ratio of 1/1M to the thickness t (-layer) of the A layer on the magnetic layer side is not particularly limited, but is 0.002 to 10, preferably 0. 01-10
, more preferably in the range of 0.01 to 5, since the output characteristics and scratch resistance become even better. Also, the value of tM is 0. It is desirable to keep the thickness in the range of 5 to 5 μm because output characteristics and scratch resistance become even better.

It is particularly desirable that the thickness unevenness in the width direction of the layer A constituting the present invention is 25% or less, more preferably 20% or less, since the output characteristics and scratch resistance will be even better.

The thickness of the A layer constituting the present invention is 0.01 to 1 μm, preferably 0.02 to 0.5 μm, to improve scratch resistance.
This is particularly desirable since the output characteristics will be even better.

The surface roughness Ra of layer A constituting the present invention is 75 nm or less, preferably 60 nm from the viewpoint of output characteristics and scratch resistance.
m or less, more preferably 45 nm or less.

The maximum height Rt, l of the A layer constituting the present invention! :Ra ratio Rt/Ra is 8.0 or less, preferably 7.5 or less, more preferably 7 or less from the viewpoint of output characteristics and scratch resistance.

The surface layer particle concentration ratio measured by the secondary ion mass spectrum of the surface of the A layer constituting the present invention is not particularly limited, but when the surface layer particle concentration ratio is 1/10 or less, particularly 1150 or less, scratch resistance, This is particularly desirable since the output characteristics will be even better.

Next, a method for manufacturing a memory tape according to the present invention will be explained.

First, as a method for incorporating the particles into the thermoplastic resin A, there is a method in which the particles are made into an ethylene glycol slurry and kneaded into the thermoplastic resin using a vent type twin-screw kneading extruder, which does not cause tearing due to stretching and is within the scope of the present invention. The relationship between thickness and average particle diameter is extremely effective for obtaining a base film with a certain content.

One way to adjust the particle content is to prepare a high-concentration master using the above method, and then dilute it with a thermoplastic resin that does not substantially contain particles during film formation to adjust the particle content. It is valid.

Next, the pellets of thermoplastic resin A containing a predetermined amount of 81 particles of thermoplastic resin are dried as necessary, and then supplied to a known extrusion device for melt lamination, extruded into a sheet form from a slit-shaped die, and cast. The film is cooled and solidified on a roll to form an unstretched film. That is, thermoplastic resins A and B are laminated using two or three extruders, a two or three layer manifold or a merging block, two or three layers of sheets are extruded from a die, and the sheets are cooled with a casting roll. Make an unstretched film. In this case, the method of installing a static mixer and a gear pump in the polymer flow path of thermoplastic resin A will prevent stretching and tearing, and the film will have a relationship between thickness and average particle size, content, and a surface layer particle concentration ratio within the desired range of the present invention. It is effective to obtain Further, it is extremely effective to use a rectangular feed block as the merging block in order to obtain the relationship between the thickness and the average particle size within the range of the present invention. In addition, setting the melting temperature of the extruder on the thermoplastic resin A side 10 to 40°C higher than that on the thermoplastic resin B side will prevent stretching breakage, and the relationship between the thickness and average particle size, the content, and the content within the range of the present invention. This is effective in obtaining a film with desired ranges of lamination thickness unevenness, surface layer particle concentration ratio, and total reflection Raman crystallization index. The above explanation is based on the configuration of A/BXA/B/
Although we have described A, it can also be applied to structures with three or more layers such as A/B/C, and in particular, in the case of three layers, three extruders can be used, and a three-layer manifold or confluence block can be used.
Thermoplastic resins A, B, and C are laminated, the three-layer sheet is extruded from a die, and the sheet is cooled with a casting roll to form an unstretched film.

Next, this 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, by using a sequential biaxial stretching method that first stretches in the longitudinal direction and then in the width direction, the longitudinal stretching is divided into three or more stages, and the total drawing ratio is 3.
．． The method carried out at a magnification of 0 to 6.5 times is effective for obtaining a film having a relationship between thickness and average particle size and content within the range of the present invention.

The longitudinal stretching temperature varies depending on the type of thermoplastic resin, but it is usually 50 to 130 degrees at the first stage.
°C and higher in the second and subsequent stages is effective for obtaining a film having a relationship between thickness and average particle size within the range of the present invention and a surface layer particle concentration ratio within the desired range of the present invention. The longitudinal stretching speed is preferably in the range of 5,000 to 50,000%/min. A common method for stretching in the width direction is to use a stenter. The stretching ratio is 3.0 to 5.0 times,
The stretching speed is preferably 1,000 to 20.000%/min, and the temperature is preferably 80 to 160°C. Next, this stretched film is heat treated. The heat treatment temperature in this case is 170~2
00°C1 especially 170-190°C, time 0°5-60
A range of seconds is preferred.

Next, a predetermined magnetic layer is applied to this film.

The magnetic layer can be applied by any known method, but the method of applying with a gravure roll provides a film with a relationship between thickness and average particle size within the range of the present invention and a surface layer particle concentration ratio within the desired range of the present invention. It is effective for In the drying step after coating, the temperature is preferably 90 to 120°C.

In addition, in the calendering process, polyamide or polyester is used as an elastic roll, and 25 to 90°C, especially 40 to 7
It is effective to conduct the film at a temperature of 0° C. in order to obtain a film having a relationship between thickness and average particle size within the range of the present invention and a surface layer particle concentration ratio within the desired range of the present invention. Furthermore, after curing the magnetic layer of this film, the original fabric (wide width) is slit to obtain the memory tape of the present invention.

[Method of Measuring Physical Properties and Evaluating Effects] The methods of measuring the characteristic values and evaluating the effects of the present invention are as follows.

(1) Average particle size of particles The thermoplastic resin is removed from the film by plasma low-temperature ashing treatment to expose the particles. The processing conditions are selected so that the thermoplastic resin is incinerated but the particles are not damaged.

This is observed with a scanning electron microscope (SEM), and the image of the particles is processed with an image analyzer. The following numerical processing is performed when the number of particles is 5000 or more while changing the observation location, and the number average diameter obtained thereby is taken as the average particle diameter.

D-ΣDi/N Here, Di is the circular diameter of the particle, and N is the number of particles.

(2) Particle size ratio This is the ratio of (average length of major axis)/(average value of minor axis) of individual particles in the measurement of (1) above. That is, it can be obtained using the following formula.

Major axis = ΣDli/N Minor axis = ΣD2i/N Dli, D2i is the major axis (maximum diameter) and minor axis (shortest axis) of each individual particle, and N is the number of particles.

(3) Relative standard deviation of particle size Standard deviation σ (=(Σ(Di
−D) 2/N)”2) divided by the average diameter (σ/
D).

(4) A cross section of the single particle index film is photographed and observed using a transmission electron microscope (TEM) to detect particles. If the observation magnification is set to about 100,000 times, a single particle that cannot be separated any further can be observed. When the total area occupied by particles is A1, and the area occupied by aggregates in which two or more particles are aggregated is B, (
A-B)/A is the single particle index. The TEM conditions are as follows, and 500 visual fields are measured by changing the measurement location of 1 visual field area = 2 μm 2 .

・Observation magnification: 100,000 times ・Acceleration voltage: 100kV ・Section thickness: Approximately 1,0OOA (5) Particle content Select a solvent that dissolves the thermoplastic resin but does not dissolve the particles, and centrifuge the particles from the thermoplastic resin. The particles are separated and the ratio (weight %) to the total weight of the particles is defined as the particle content.

(6) Crystallization parameter ΔTcg, heat of fusion measured using a differential scanning calorimeter (DSC).

The DSC measurement conditions are as follows. That is, sample 1
0 mg was set in a DSC device, melted at a temperature of 300° C. for 5 minutes, and then rapidly cooled in liquid nitrogen.

This rapidly cooled sample was heated at a rate of 10°C/min, and the glass transition point Tg
Detect. The temperature was further increased, and the exothermic peak temperature of crystallization from the glass state was defined as the cold crystallization temperature Tcc.

The temperature was further increased, and the heat of fusion was determined from the melting peak. Tcc here! : The difference in Tg (Tcc-Tg) is defined as the crystallization parameter ΔTcg.

(7) Young's modulus 2 using an Instron type tensile tester according to the method specified in J I 5-Z-1702.
Measurement was performed at 5° C. and 65% RH.

(8) Total reflection Raman crystallization index The total reflection Raman spectrum was measured, and the half-width of 1730 cm-'', which is the stretching vibration of the carbonyl group, was taken as the total reflection Raman crystallization index of the surface.The measurement conditions were as follows. However, the measurement depth is 500 to 1,000 mm from the surface.
It was set as the degree.

■Light source: Argon ion laser (5,145A) ■Sample setting Press the film surface onto a total reflection prism so that the laser polarization direction (S polarization) and the film longitudinal direction are parallel, and adjust the incidence angle of the laser to the prism. (Angle with the film thickness direction) was set to 60°.

■Detector PM: RCA31034/Photon Coun
ting Sysjem(Hamanalsu C12
30) (supply 1,600V) ■Measurement conditions 5LIT 1. [)0[1μm LASE
R100mW GATE TIME 1.0secS
CAN 5PEED 12cm-'/minS
AMPLING INTERVAL 0.2cmR
EPEAT TIME 6 (9) Intrinsic viscosity [η] (unit: di/g) A value calculated from the solution viscosity measured at 25° C. in orthochlorophenol using the following formula. That is, η5. /C= [η] +K [ηko 2 ・ Nicode, η5P-(solution viscosity/solvent viscosity)-1, C is the weight of dissolved polymer per 100 ml of solvent (g/100 ml.
Normal],,2), K is Huggins constant (set to 0,343). In addition, solution viscosity and solvent viscosity were measured using an Ostwald viscometer.

(10) Surface layer particle concentration ratio Using secondary ion mass spectrometry (SIMS), the concentration ratio of the element with the highest concentration among the elements caused by particles in the film and the carbon element of the thermoplastic resin is defined as the particle concentration, Perform analysis in the thickness direction. The ratio of the particle concentration A at the outermost layer particle concentration (point at depth O) measured by S■MS to the maximum concentration B obtained by further analysis in the depth direction, A
/B was defined as the surface layer particle concentration ratio. The measuring device and conditions are as follows.

Primary ion species = 02 Primary ion acceleration voltage: 12KV Primary ion current: 200nA Raster area: 400μm mouth analysis area, gate 30% Measurement vacuum level: 6. OX 10-9To+
rE-GUN: 0. 5KV-3,0A (1
1) Surface roughness parameter Ra (center line average roughness), Rt
(Maximum height) Measured using a surface roughness meter. The conditions were as follows, and the average value of 20 measurements was taken as the value.

・Stylus tip radius: 20.5μm ・Stylus load: 5mg ・Measurement length: 1mm ・Cutoff value: 0.08mm (12) Output characteristics A 100% signal is recorded by a shunal generator, and the signal noise is determined from the reproduced signal. The S/N was measured with a measuring device and marked as A. Further, recording and reproducing of the signal was repeated using a tape on which the same signal as above was recorded, and the S/N of the tape after 10,000 times was measured in the same manner as above and was designated as B. S due to this repetition
/N decrease (A - B) is 6. If it was less than OdB, it was determined that the output characteristics were good, and if it was more than that, it was determined that the output characteristics were poor.

(13) Scratch resistance In an atmosphere of 20°C and 60% relative humidity, a 1/2 inch wide tape was brought into contact with a fixed shaft (surface roughness 0.28) with an outer diameter of 6 mmφ at an angle θ = πrad, and the tension was applied. 100 at 80g and speed 500m/min (-833cm/s)
After running the tape several times, the non-magnetic surface of the tape was deposited with aluminum, and the number and width of scratches and the state of white powder generation were observed using a differential interference microscope.

All (No scratches/cm and no white powder generation: Scratch resistance: Excellent, Less than 3 scratches/cm and almost no white powder generation: Scratch resistance: Good, Other: Scratch resistance: Good) Scratch resistance: Determined as poor.

[Example] The present invention will be explained based on examples.

Examples 1 to 4 and Comparative Examples 1 to 4 Ethylene glycol slurries containing crosslinked polystyrene particles and silica particles derived from colloidal silica with different average particle sizes were prepared, and the ethylene glycol slurry was heated at 190°C for 1.5 hours. After heat treatment, transesterification with dimethyl terephthalate is performed, polycondensation is performed, and the particles are reduced to 0.
．． Polyethylene terephthalate containing 3-6% by weight (
(hereinafter abbreviated as PET) pellets were made. At this time, the polycondensation time was adjusted so that the intrinsic viscosity was 0.65 (thermoplastic resin A). In addition, PET having an intrinsic viscosity of 0°62 and containing substantially no particles was produced by a conventional method, and thermoplastic resin B
And so.

After each of these polymers was dried under reduced pressure (3 Torr) at 180°C for 6 hours, thermoplastic resin A was supplied to extruder 1 and melted at 285°C, and thermoplastic resin B was further supplied to extruder 2, These polymers were melted at 280° C. and laminated in a merging block, then wound around a casting drum with a surface temperature of 30° C. using an electrostatic casting method, and cooled and solidified to produce a laminated unstretched film. At this time,
The total thickness and the thickness of the thermoplastic resin A layer were adjusted by adjusting the discharge amount of each extruder.

This unstretched film was heated to 4.0 mm in the longitudinal direction at a temperature of 82°C.
Stretched twice. This stretching is done by the difference in circumferential speed between the two sets of rolls.
It was done in stages. This -axially stretched film was stretched 4.4 times in the width direction at 105°C at a stretching rate of 2.000%/min using a stenter, and then heat-treated at 210°C for 5 seconds under constant length to a total thickness of 10 μm. A biaxially oriented laminated film was obtained.

Magnetic paint is applied to this film using a gravure roll. The magnetic paint was prepared as follows.

7-Fe2O3 100 parts Average particle size Length 20.3 μm Acicular ratio: 10/1 Coercive force 5000e ・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
After mixing and dispersing the above composition in 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. , oriented in a magnetic field, dried at 110°C, and further heated to a temperature of 7 in a small test calender (steel roll/nylon roll, 5 stages).
After calendering at 5°C and a linear pressure of 250 kg/cm, curing was performed at 70°C for 48 hours to obtain a memory tape.

These properties are as shown in Table 1, and the memory tape of the present invention had excellent or good scratch resistance and output characteristics.If not, the memory tape that satisfied the scratch resistance and output characteristics was considered to be a good product. I couldn't.

[Effects of the Invention] The present invention uses a thermoplastic resin containing particles by devising a manufacturing method, and sets the relationship between particle size and film thickness and content within a specific range, resulting in improved scratch resistance and output characteristics. Thus, a memory tape with excellent properties was obtained, which can accommodate increased processing speeds in various applications.

Claims (1)

[Claims] A memory tape comprising a magnetic layer provided on at least one side of a base film, wherein the base film is a layer (B layer) made of thermoplastic resin B, and a layer made of thermoplastic resin A containing particles on at least one side of the layer (B layer). (A layer) is a laminated film in which the surface roughness Ra of the A layer is 75 nm or less, and the ratio Rt/Ra of the maximum height Rt and Ra is 8.0 or less,
The average particle diameter d of the particles contained in layer A is 10 to 1000n.
m, the content of the particles in layer A is 1 to 40% by weight, A
The ratio t/d of the layer thickness t and the average particle diameter d of the particles is 0.1 to
A memory tape characterized by 3.