JP2666500B2 - Video tape for high density recording - Google Patents

Description

The present invention relates to a video tape for high-density recording.

[Prior art] In recent years, the progress of magnetic recording tape has been remarkable.
The demand for video tapes has increased sharply with the spread of home video tape recorders, and with this, there has been an increasing demand for higher performance models. In particular, there have been remarkable advances in technology for high-density recording, and improvements have been made on both the magnetic layer and the base film. Improvements in magnetic layers include coating, electroplating, electroless plating, vacuum deposition,
It has been considered to reduce the thickness of the magnetic layer by a method such as sputtering or ion plating. On the other hand, as the improvement of the base film, the surface morphology and surface characteristics have been improved, and the mechanical characteristics of the film have been improved (JP-A-62-80825, etc.).

[Problems to be Solved by the Invention] However, the above-mentioned base film is still insufficient for high-density recording applications requiring severe characteristics, and the process speed of a process of dubbing a soft tape or the like is not sufficient. With the increase, the non-magnetic surface is damaged by a contacting roll or guide. Further, there is a disadvantage that the image quality, that is, the S / N (signal / noise ratio) is insufficient due to the deterioration of the image quality during dubbing.

The present invention solves the drawbacks of the prior art, in particular, the non-magnetic surface of the tape is hardly damaged (hereinafter, referred to as having excellent scratch resistance) in a high-speed process, and the image quality during dubbing is small (hereinafter, referred to as the dubbing resistance). (Excellent) high-density recording video tape.

Means for Solving the Problems The present invention comprises a biaxially oriented thermoplastic resin film having a film layer A forming a nonmagnetic surface and a magnetic layer, and the height distribution standard deviation σ of surface projections on the nonmagnetic surface. (Nm)
And the number N of protrusions exceeding 225 nm in height (number / mm ² ) is 0 ≦ (3σ).
-225) A video tape in which N <5 × 10 ⁴ , wherein the film layer A has a thickness of 0.005 to 3 μm containing thermoplastic resin A and particles as main components, and is contained in the film layer A. The average particle size of the particles is 0.1 to 10 times the thickness of the film layer A,
The present invention relates to a video tape for high-density recording in which the content of the particles is 0.5 to 50% by weight.

The thermoplastic resin A constituting the present invention is not particularly limited, such as polyester, polyolefin, polyamide, and polyphenylene sulfide. Particularly, polyester, especially, ethylene terephthalate, ethylene α, β
Scratch resistance and dubbing resistance when at least one structural unit selected from -bis (2-chlorophenoxy) ethane-4,4'-dicarboxylate and ethylene 2,6-naphthalate units is the main constituent component Is more preferable. Further, when the thermoplastic resin constituting the present invention is crystalline or optically anisotropic when melted, scratch resistance and dubbing resistance are further improved, which is extremely desirable. The 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, 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, scratch resistance and dubbing resistance are further improved, which is extremely desirable. Further, in the case of a polyester containing ethylene terephthalate as a main component, it is particularly desirable because the dubbing resistance and the scratch resistance are further improved. Note that two or more kinds of thermoplastic resins may be mixed or a copolymer may be used as long as the present invention is not impaired.

The particles in the thermoplastic resin A of the present invention have a particle diameter ratio (particle major axis / minor axis) of 1.0 to 1.3 in the film layer A, and in particular, in the case of spherical particles, the particles have more scratch resistance. It is desirable because it becomes even better.

Further, the particles in the thermoplastic resin A of the present invention have a single particle index in the film layer A of 0.7 or more, preferably 0.9 or more, so that the scratch resistance and the dubbing resistance are further improved. desirable.

Further, the particles in the thermoplastic resin A of the present invention are desirable when the relative standard deviation in the film layer A is 0.6 or less, preferably 0.5 or less, because the scratch resistance and the dubbing resistance are further improved.

The type of particles in the thermoplastic resin A of the present invention is not particularly limited, but alumina silicate, silica in which primary particles are agglomerated, internally precipitated particles and the like are not preferable to satisfy the above preferable particle characteristics, There are substantially spherical silica particles resulting from colloidal silica, particles of a crosslinked polymer (eg, crosslinked polystyrene), and the like. Particularly, when the weight is reduced by 10% by weight (in nitrogen, using a thermogravimetric analyzer Shimadzu TG-30M)
Measured using Crosslinked polymer particles whose degree of crosslinking is increased until the temperature rise rate (20 ° C./min) becomes 380 ° C. or more are particularly desirable because scratch resistance and dubbing resistance are further improved. In the case of spherical silica originating from colloidal silica, it is particularly desirable to use a substantially spherical silica produced by the alkoxide method and having a low sodium content, since the scratch resistance is further improved. However, other particles, such as particles of calcium carbonate, titanium dioxide, alumina, etc., can be sufficiently used by appropriately controlling the film thickness and the average particle size.

The crystallization promoting coefficient of the particles in the thermoplastic resin A of the present invention is not particularly limited, but is -15 to 15 ° C, preferably -5 ° C to
A temperature of 10 ° C. is particularly desirable because scratch resistance is further improved.

The size of the particles needs to be such that the average particle size in the film layer A is in the range of 0.1 to 10 times, preferably 0.5 to 5 times, more preferably 1.1 to 3 times the thickness of the film layer A. is there. If the average particle size / thickness ratio of the film layer A is smaller than the above range, the scratch resistance becomes poor, and if it is too large, the scratch resistance and the dubbing resistance become poor.

The average particle diameter (diameter) of the particles in the thermoplastic resin A in the film layer A is 0.007 to 1.0 μm, preferably 0.02 to 0.2 μm.
When the thickness is in the range of 8 μm, the scratch resistance and the dubbing resistance are further improved, which is desirable.

The content of the particles in the thermoplastic resin A of the present invention is 0.5 to 50.
% By weight, preferably 1 to 30% by weight, more preferably 2% by weight.
It must be ~ 15% by weight. If the content of the particles is less than the above range, or if the content is too large, the scratch resistance becomes poor, which is not preferable.

The film layer A of the present invention has a composition composed of the thermoplastic resin A and particles as a main component, but may be blended with other polymers within a range not to impair the object of the present invention,
Further, organic additives such as antioxidants, heat stabilizers, lubricants, and ultraviolet absorbers may be added to the extent that they are usually added.

The film layer A of the present invention is a film in which the above composition is biaxially oriented. Uniaxial or non-oriented films are not preferred because scratch resistance is poor.

In addition, the film layer A of the present invention has a structure in which the orientation of the polymer molecules in the thickness direction of the film, for example, in the vicinity of the surface layer is non-oriented or not uniaxially oriented, that is, the molecules in the entire thickness direction. When the orientation is biaxial orientation, scratch resistance and dubbing resistance are further improved, which is particularly desirable.

Especially when the molecular orientation measured by Abbe refractometer, refractometer using laser, total reflection laser Raman method etc. is biaxial orientation on both the front and back surfaces, scratch resistance and dubbing resistance are even better. This is particularly desirable.

Further, the thermoplastic resin A is a crystalline polyester,
This total reflection Raman crystallization index of the surface of the film layer A of the present invention as a main component is 20 cm ^-1 or less, preferably 18cm ^-1 or less, scratch resistance when further 17cm ^-1 or less, the resistance dubbing resistance It is highly desirable because it is even better.

Film layer A containing thermoplastic resin A of the present invention as a main component
The concentration ratio of the surface particles measured by the secondary ion mass spectrum is not particularly limited, but is preferably 1/10 or less, particularly preferably 1/50 or less, because the scratch resistance is further improved.

Film layer A containing thermoplastic resin A of the present invention as a main component
Should have a thickness of 0.005 to 3 μm, preferably 0.01 to 1 μm, and more preferably 0.03 to 0.5 μm. If the film thickness is smaller than the above range, the dubbing resistance is poor, and if it is large, the scratch resistance is poor, which is not preferable.

Film layer A containing thermoplastic resin A of the present invention as a main component
The average projection height of the surface of 5 to 500 nm, preferably 10 to 300
When the thickness is in the range of 15 nm to 200 nm, the scratch resistance and the dubbing resistance are further improved.

Film layer A containing thermoplastic resin A of the present invention as a main component
It is particularly desirable that the average spacing between protrusions is 6 μm or less, preferably 4 μm or less, because the scratch resistance and the dubbing resistance are further improved.

Film layer A containing thermoplastic resin A of the present invention as a main component
The center line depth Rp of the surface of is not particularly limited, Rp is 180n
It is particularly desirable that the thickness be equal to or less than m, particularly 160 nm or less, since the dubbing resistance will be further improved. Also, the above Rp and the maximum height
When the ratio of Rt and Rt / Rp is 1.5 to 2.5, particularly 1.7 to 2.3, scratch resistance and dubbing resistance are further improved, which is particularly desirable.

Film layer A containing thermoplastic resin A of the present invention as a main component
The ratio of the center line average roughness Ra to the maximum height Rt of the surface of Rt, Rt / Ra is
A scratch resistance and a dubbing resistance of 9.0 or less, especially 8.5 or less, are particularly desirable because the resistance becomes even better.

As described above, it is highly desirable that the thermoplastic resin constituting the film layer A of the present invention be crystalline or melt optically anisotropic. However, in the case of a melt isotropic film, the crystallization parameter ΔTcg is 25 to 65. It is particularly preferable that the temperature is 0 ° C., because the scratch resistance is further improved.

When the thermoplastic resin A is polyester, it is particularly desirable that the refractive index in the thickness direction of the surface of the thermoplastic resin A is 1.5 or less, because the scratch resistance and the dubbing resistance are further improved.

When the thermoplastic resin A forming the film layer A of the present invention is a polyester, the intrinsic viscosity of the film is 0.60 or more, especially 0.1.
A value of 70 or more is particularly desirable because scratch resistance is further improved.

The biaxially oriented thermoplastic resin film in the present invention may be used alone (single-layer film), but the film is biaxially oriented after laminating the film layer A on at least one surface of the film layer B made of the thermoplastic resin B. It is very desirable to use in the form of not only because the mechanical properties are improved, but also the scratch resistance and the dubbing resistance are further improved. Here, the thermoplastic resins A and B may be the same or different.

The above is the case where the laminated structure is layer A / layer B / layer A, layer A / layer B, but, of course, layer A / layer in which layer C having a different surface state from layer A is provided on the opposite surface to layer A. It may be a B / layer C or a multilayer structure of more layers. (Here, layer A, layer B, layer C
The types of the respective thermoplastic resins may be the same or different. It is necessary that at least one surface is the layer A. As the thermoplastic resin B, a crystalline polymer is desirable. In particular, when the crystallinity parameter ΔTcg is in the range of 20 to 100 ° C., it is desirable because the dubbing resistance is further improved.
Specific examples include polyesters, polyamides, polyphenylene sulfides, and polyolefins, and polyesters are particularly preferable because the dubbing resistance is further improved. As the polyester, at least one structural unit selected from ethylene terephthalate, ethylene α, β-bis (2-chlorophenoxy) ethane-4,4′-dicarboxylate and ethylene 2,6-naphthalate units is mainly used. When it is used as a component, the dubbing resistance is particularly improved, which is desirable. However, other components may be copolymerized within a range that does not impair the present invention and within a range that does not impair desired crystallinity, preferably within 5 mol%.

The thermoplastic resin B of the present invention may be blended with other kinds of polymers as long as the object of the present invention is not impaired, and organic additives such as antioxidants, heat stabilizers, lubricants, and ultraviolet absorbers may be added. The agent may be added to the extent that the agent is usually added.

It is not particularly necessary for the film layer B containing the thermoplastic resin B as a main component to contain particles, but the average particle diameter is 0.007.
0.001 to 0.5% by weight, especially 0.005 to 0.3% by weight, more preferably 0.005 to 0.2% by weight,
It is very desirable to contain it because the scratch resistance is further improved. It is desirable to use the kind of particles contained in the thermoplastic resin A that is desirably used. The types and sizes of the particles contained in the thermoplastic resins A and B may be the same or different.

The difference (AB) between the crystallization parameters ΔTcg of the thermoplastic resin A and the thermoplastic resin B is not particularly limited.
When the temperature is from + 20 ° C., scratch resistance and dubbing resistance are further improved, which is particularly desirable.

In the present invention, the film layer A forms a non-magnetic surface. That is, when the biaxially oriented thermoplastic resin film is a single film, one surface of the film is a non-magnetic surface and a magnetic layer is formed on the other surface. In the case of a composite film of the film layer A and the film layer B, the film layer A forms a non-magnetic surface, and the film layer B is provided with a magnetic layer. In the case of a three-layer composite film of film layer A / film layer B / film layer A, one film layer A forms a non-magnetic surface, and the other film layer A is provided with a magnetic layer.

In the present invention, the height distribution standard deviation σ (nm) of the surface projections on the non-magnetic surface and the number of projections N (number / m
m ² ) satisfies 0 ≦ (3σ−225) N <5 × 10 ⁴ . Preferably, 0 ≦ (3σ−225) N <3 × 10 ⁴ , more preferably 0 ≦ (3σ−225) N <1 × 10 ⁴ . If this value is small, the scratch resistance is not satisfied, while if it is too large, the dubbing resistance deteriorates.

The magnetic layer in the present invention is not particularly limited, and the magnetic material may be γ-Fe ₂ O ₃ , Co-containing γ-Fe ₂ O ₃ , CrO ₂ , Fe
A metal powder such as -Co, Fe-Co-Ni or the like, obtained by dispersing in a binder comprising polyvinyl chloride, polyvinyl acetate, polyurethane, nitrocellulose, a copolymer or a mixture thereof, or a resin and other resin; Magnetic paints. Further, the magnetic material includes a material in which Co, Co-Cr, or another metal is deposited by a vacuum deposition method such as vacuum deposition, sputtering, or ion plating.

Next, a method for producing a film used in the present invention will be described.

First, as a method for incorporating particles into the thermoplastic resin A, when the thermoplastic resin is a polyester, the thermoplastic resin A is dispersed in the form of a slurry of ethylene glycol as a diol component, and the ethylene glycol is polymerized with a predetermined dicarboxylic acid component. It is effective to obtain a film having the relationship between the thickness and the average particle size in the range of the present invention, the content and the oriented state in the desired range without breaking the stretch. Further, the method of adjusting the melt viscosity of the polyester containing particles, the copolymerization component, etc., and keeping the crystallization parameter ΔTcg in the range of 40 to 65 ° C. does not cause stretching breakage, and the thickness and the average particle size in the range of the present invention are not broken. Is effective for obtaining a film having the following relationship, content, orientation state in a desirable range, surface layer particle concentration ratio, average projection height, Rt / Rp ratio, and Rt / Ra ratio.

Also, the slurry of particles of ethylene glycol is 140 ~ 2.
30 minutes to 5 hours at a temperature of 00 ° C, especially 180 to 200 ° C, especially 1 to
The method of heat-treating for 3 hours 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 particle concentration ratio in the range of the present invention without breaking the stretch.

Also, as a method of incorporating particles into a thermoplastic resin,
After heat-treating the particles in the same manner as above, the solvent is mixed with the thermoplastic resin in the form of a slurry in which water has been replaced with water, and the mixture is kneaded using a vented twin-screw extruder and kneaded into the thermoplastic resin. It is extremely effective for obtaining a film having the relationship between the thickness and the average particle size, the content, the orientation in the desired range, the surface layer particle concentration ratio, the average projection height, the Rt / Rp ratio, and the Rt / Ra ratio in the range of the invention.

As a method of adjusting the content of particles, a method of preparing a high-concentration master by the above method, and diluting it with a thermoplastic resin containing substantially no particles at the time of forming a film, and adjusting the content of particles is known. It is valid.

Thus, the pellets containing a predetermined amount of particles are dried as necessary, and then supplied to a known melt extruder, extruded into a sheet from a slit-shaped die at a temperature equal to or higher than the melting point of the thermoplastic resin and equal to or lower than the decomposition point, and a casting roll. The above is cooled and solidified to form an unstretched film. In this case, when extrusion-molding into an unstretched film, the ratio of die slit gap / unstretched film thickness is in the range of 5 to 30, preferably 8 to 20, and the voltage of the electrostatic application casting method is 5000 to 15000 V, Preferably 6000 to 12000V, the film of the relationship between the thickness and the average particle size in the range of the present invention without stretching, the range of the content, the orientation state of the desired range, the surface particle concentration ratio, the total reflection Raman crystallization index film. Effective to get.

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, first use the sequential biaxial stretching method of stretching in the longitudinal direction, then in the width direction,
The longitudinal stretching is divided into three or more stages and the total longitudinal stretching ratio is
The method carried out at 3.0 to 6.5 times is effective in obtaining a film having a relationship between the thickness and the average particle size, the content, the orientation state in a desirable range, and the surface particle concentration ratio within the range of the present invention without stretching.
However, when the thermoplastic resin is a melt optically anisotropic resin, the stretching ratio in the longitudinal direction is appropriately from 1 to 1.1 times. The longitudinal stretching temperature varies depending on the type of thermoplastic resin and cannot be unconditionally determined.
It is effective to increase the film thickness after the first stage to obtain a film having the relationship between the thickness and the average particle diameter, the content, the desired state of orientation, the average projection height, and the surface layer particle concentration ratio in the range of the present invention. 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 stretching ratio is suitably in the range of 3.0 to 5.0 times. Stretching speed in the width direction is 1000-20000%
/ Min, and the temperature is preferably in the range of 80 to 160 ° C. Next, this stretched film is heat-treated. The heat treatment temperature in this case is 17
The temperature is preferably from 0 to 220 ° C, particularly from 170 to 210 ° C, and the time is preferably from 0.5 to 60 seconds.

Next, the following method is effective as a method of laminating a film mainly composed of the thermoplastic resin A on at least one side of the film mainly composed of the thermoplastic resin B.

A predetermined thermoplastic resin A composition and a thermoplastic resin B (A,
(B may be the same or different) is supplied to a known extruder for melt lamination, extruded into a sheet from a slit die, and cooled and solidified on a casting roll to produce an unstretched film. That is, two or three extruders,
Using two or three layers of manifolds or merging blocks, the thermoplastic resins A and B are laminated, and 2 or 3
The sheet of layers is extruded and cooled with a casting roll to make an unstretched film. In this case, as a method of controlling the lamination thickness, a method of controlling the temperature in the width direction of the confluence block in accordance with the lamination thickness does not cause stretching breakage, the relationship between the thickness and the average particle size in the range of the present invention, the content, and the preferable range. Orientation state, average protrusion height, Rt / Rp ratio, Rt / Ra
This is effective for obtaining a film having a ratio of a surface layer concentration to a surface layer.
Further, it is preferable that the melting temperature of the extruder on the thermoplastic resin A side be higher by 10 to 40 ° C. than that on the thermoplastic resin B side, without stretching breakage, the relationship between the thickness and the average particle diameter in the range of the present invention, the content, and the content. Range of orientation state, average protrusion height, Rt / Rp ratio, Rt / Ra
It is effective for obtaining a film having a ratio, a surface particle concentration ratio, and a total reflection Raman crystallization index.

Next, the point of the method of biaxially stretching this unstretched film and making it biaxially oriented is basically the same as that of the single-layer film described above. However, the setting of the stretching temperature in the case of the laminated film needs to be set with reference to the thermoplastic resin B. Further, in the heat treatment step of the two-layer laminated film, the hot air temperature blown to the thermoplastic resin A layer is set to be 3 to 20 ° C. lower than that of the thermoplastic resin B layer. This is effective for obtaining a film having a desired range of orientation state, average projection height, Rt / Rp ratio, Rt / Ra ratio, surface layer particle concentration ratio, and total reflection Raman crystallization index.

A predetermined magnetic layer is applied to the biaxially oriented film thus obtained. The method of applying the magnetic layer can be performed by a known method, but the drying step after the application is performed at a temperature of 90 to 120.
C. is preferred.

In addition, the calendering step uses polyamide or polyester for the elastic roll, and is performed at a temperature range of 25 to 90 ° C, particularly 40 to 70 ° C. It is effective for obtaining a film having a surface particle concentration ratio. Further, after curing the magnetic layer of this film, the raw material (wide width) is slit to obtain the video tape for high density recording of the present invention.

[Method for Measuring Physical Properties and Method for Evaluating Effect] The method for measuring characteristic values and the method for evaluating effect according to the present invention are as follows.

(1) Average particle size of particles The thermoplastic resin is removed from the film by a plasma low-temperature incineration method to expose the particles. Processing conditions are selected such that the thermoplastic resin is ashed but the particles are not damaged. Observing this with a scanning electron microscope (SEM), linking the image of the particles (shading of light generated by the particles) to an image analyzer, changing the observation location, and performing the following numerical processing with more than 5,000 particles, The obtained number average diameter D is defined as the average particle diameter.

D = ΣD _i / N where, D _i is a circle equivalent diameter of the particles, N is the is the number.

(2) Content of Particles A solvent in which the thermoplastic resin is dissolved but the particles are not dissolved is selected, the particles are centrifuged from the thermoplastic resin, and the particle content is defined as a ratio (% by weight) to the total weight of the particles.
In some cases, the combined use of infrared spectroscopy is also effective.

(3) Crystallization parameter ΔTcg, heat of fusion Measured using DSC (differential scanning calorimeter). The measurement conditions for DSC are as follows. That is, 10 mg of a sample is set in a DSC apparatus, 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 is further increased, and the crystallization exotherm peak temperature from the glass state is determined to be the cold crystallization temperature Tc.
c. 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.

(4) Surface Molecular Orientation (Refractive Index) Measured using an Abbe refractometer using 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. Biaxial orientation of the polymer in the longitudinal direction, a width direction, the refractive index in the thickness direction N _1, N _2, N ₃
When the absolute value of (N ₁ −N ₂ ) is 0.07 or less and N ₃ /
One criterion may be that [(N ₁ + N ₂ ) / 2] is 0.95 or less. Further, 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 of the laser was measured by Ramanor manufactured by Jobin-Yvon.
The U-1000 Raman system measures the total reflection Raman spectrum, for example in the case of PET, the polarization measurement ratio of the band intensity ratio of 1615 cm ^-1 (skeletal vibration of benzene ring) and 1730 cm ^-1 (stretching vibration of carbonyl group) (YY / XX ratio, etc., where YY: Raman light detection parallel to Y with laser polarization direction Y, XX: Raman light detection parallel to X with laser polarization direction X) Correspondence with molecular orientation can be used. 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, difference, and the like. The measurement conditions in this case are as follows.

Light source Argon ion laser (5145Å) 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 the film thickness direction) was 60 ゜.

Detector PM: RCA31034 / Photon Counting System (Hamamatsu C123
0) (supply 1600V) Measurement conditions SLIT 1000μm LASER 100mW GATE TIME 1.0sec SCAN SPEED 12cm ^-1 / min SAMPLING INTERVAL 0.2cm ^-1 REPEAT TIME 6 (5) Total reflection Raman crystallization index In the same manner as (4) above, The total reflection Raman spectrum was measured, and the surface was defined as the total reflection Raman crystallization index with a half-value width of 1730 cm ⁻¹ , which is the stretching vibration of the carbonyl group. The measurement depth is about 500 to 1000 angstroms from the surface.

(6) Average height of surface protrusions The non-magnetic surface of the tape was measured with a two-detector scanning electron microscope [ESM-3200, manufactured by Elionix Inc.] and a cross-section measuring device [PMS-1, Elionix Inc.]. The height measurement side of the projection when scanning with the height of the flat surface set to 0 is sent to an image processing apparatus [IBAS2000, manufactured by Carl Zeiss Co., Ltd.], and a film surface projection image is reconstructed on the image processing apparatus. Next, the highest value among the individual projections obtained by binarizing the projections in this surface projection image is defined as the height of the projection, and this is determined for each individual projection. This measurement was repeated 500 times at different locations to determine the number of protrusions, and the average value of the heights of all the measured protrusions was defined as the average height. The standard deviation of the projection height distribution is determined by the least squares method from the normal distribution function Ni = Aexp (−hi ² / 2σ ² ) (where hi, Ni, and A are the projection height, the number of projections at the height hi, and a constant, respectively). Is defined by σ obtained by
The magnification of the scanning electron microscope is selected to be a value between 1000 and 8000 times. In some cases, the high-precision optical interference type 3
Dimensional surface analyzer (TOPO-3D manufactured by WYKO, objective lens: 40)
Height information obtained by using a high-resolution camera (up to 200 times, use of a high-resolution camera is effective) may be replaced with the SEM value and used.

(7) Center line average surface roughness Ra, center line depth Rp, maximum height
Rt, spacing between protrusions Sm Measured 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.

・ Stylus tip radius: 0.5 μm ・ Stylus load: 5 mg ・ Measurement length: 1 mm ・ Cutoff value: 0.08 mm The definition of Ra, Rp, Rt, and Sm is, for example, the measurement of surface roughness by Nara Jiro・ Evaluation method ”(General Technology Center, 198
It is shown in 3).

(8) Young's modulus According to the method specified in JIS-Z-1702, use an Instron type tensile tester at 25 ° C and 65%
Measured at RH.

(9) Intrinsic viscosity [η] (unit: dl / g) A value calculated from the following formula from the solution viscosity measured at 25 ° C. in orthochlorophenol is used. That is, η _SP / C = [η] + K [η] ² · C where η _SP = (solution viscosity / solvent viscosity) −1, and C is the solvent
Dissolved polymer weight per 100 ml (g / 100 ml, usually 1.2),
K is the Hangis constant (0.343). Also, solution viscosity,
The solvent viscosity was measured using an Ostwald viscometer.

(10) Surface particle concentration ratio Using secondary ion mass spectroscopy (SIMS), the concentration ratio of the highest concentration element among the elements caused by the particles in the film to the carbon element of the polyester is defined as the particle concentration, Perform direction analysis. The ratio A / B between the particle concentration A at the outermost surface particle concentration (point at depth 0) measured by SIMS and the maximum concentration B obtained by further analyzing in the depth direction, A / B, was defined as the surface concentration ratio. The measuring device and conditions are as follows. The measuring device and conditions are as follows.

Measurement device Secondary ion mass spectrometer (SIMS) A-DIDA3000 manufactured by ATOMIKA, West Germany Measurement conditions Primary ion species: O ₂ ⁺ Primary ion acceleration voltage: 12 KV Primary ion current: 200 nA Raster area: 400 μm □ Analysis area: Gate 30% Measurement vacuum degree: 6.0 × 10 ^-9 Torr E-GUN: 0.5KV-3.0A (11) Single particle index The cross section of the film is observed by a photograph with a transmission electron microscope (TEM) to detect particles. When the observation magnification is set to about 100,000, one particle that cannot be further divided can be observed. When the total area occupied by the particles is A, and the area occupied by the aggregate in which two or more particles are agglomerated is B, (A
-B) / A is defined as a single particle index. The TEM conditions are as follows. One visual field area: 2 μm ² , measurement was performed at 500 visual fields at different locations.

-Apparatus: JEM-1200EX manufactured by JEOL-Observation magnification: 100,000 times-Acceleration voltage: 100 kV-Section thickness: about 1000 angstroms (12) Particle size ratio In the measurement of (1) above, the average value of the major axis of each particle / It is the ratio of the average value of the minor axis.

 That is, it is obtained by the following equation.

Major axis = ΣD1 _i / N long diameter short diameter _{= ΣD2 i / N D1 i,} D2 i each individual particle (maximum diameter), short diameter (the shortest diameter), N is the total number.

(13) Relative standard deviation of particle diameter Standard deviation σ calculated from individual particle diameter D _i , average diameter D, and total number N of particles measured by the method (1). Was divided by the average diameter D (σ / D).

(14) Thickness of the thermoplastic resin A layer in the laminated film Using a secondary ion mass spectrometer (SIMS), the concentration of the element attributable to the highest concentration of the particles in the film and the carbon element of the polyester The ratio (M ⁺ / C ⁺ ) is the particle concentration,
Analysis in the depth (thickness) direction from the surface of the thermoplastic resin A layer is performed. 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 which has reached the maximum value once at the depth [I] starts to decrease again. Based on this concentration distribution curve, the depth [II] (here, I
I> I) was taken as the lamination thickness. The conditions are the same as in the measurement method (10).

In addition, when the particles most contained in the film are organic polymer particles, it is difficult to measure by SIMS, so XPS (X-ray photoelectron spectroscopy), IR
(Infrared spectroscopy) or a confocal microscope
The depth profile of the particle concentration may be measured, and the layer thickness may be obtained by the same method as described above.

Further, instead of the depth profile of the particle concentration described above, the lamination thickness of the thermoplastic resin A may be obtained by observing a cross section of the film or a thin film level measuring device.

The thickness of the single-layer film can be determined by a known method, for example, a dial gauge method, an optical interference method, a gravimetric method, a thin film step measurement method, or the like.

(15) Scratch resistance Using a tape running tester, run on guide pins (surface roughness: 100 nm in Ra) (running speed: 1000 m / min, running frequency: 10 passes, winding angle: 60 °, running) Tension: 80g). At this time, observe the scratches on the non-magnetic surface of the tape with a microscope,
When the number of scratches of 2.5 μm or more per tape width was less than two, it was judged as excellent, and two or more and less than ten were judged as good, and ten or more were judged as bad. Although excellent is desirable, even good is practically usable.

(16) Dubbing resistance Using a VTR for home use on a tape, a 100% chroma signal was recorded with a Shibasoku TV test waveform generator (TG7 / U706), and a Shibasoku color video noise measurement device (925D / The chroma S / N was measured in 1) and set to A. The same sample tape (not yet measured) was obtained by measuring the pancake of the master tape on which the same signal was recorded as described above using a magnetic field transfer type video software high-speed printing system (for example, a Sprinter manufactured by Sony Magnescale Co., Ltd.). The chroma S / N of the tape after dubbing to the pancake of (Recording) was measured in the same manner as described above, and was designated as B. When the decrease in chroma S / N (AB) due to the dubbing was less than 3 dB, the anti-dubbing property was excellent. When it was 3 dB or more and less than 5 dB, it was judged as good. Although excellent is desirable, even good is practically usable.

[Examples] The present invention will be described based on examples.

Examples 1-4, Comparative Examples 1-4 Crosslinked polystyrene particles having different average particle sizes, an ethylene glycol slurry containing silica particles derived from colloidal silica was prepared, and the ethylene glycol slurry was heat-treated at 190 ° C for 1.5 hours. , After transesterification with dimethyl terephthalate, polycondensation, the particles 0.15 to 10
Polyethylene terephthalate (hereinafter referred to as PET)
Pellets). At this time, the polycondensation time was adjusted to make the intrinsic viscosity 0.64 (thermoplastic resin A). In addition, a PET substantially containing particles having an intrinsic viscosity of 0.62 and containing substantially no particles was produced by a conventional method, and was designated as a thermoplastic resin B. Each of these polymers was dried under reduced pressure (3 Torr) at 180 ° C. for 3 hours. The thermoplastic resin A is supplied to the extruder 1 and melted at 288 ° C., and the thermoplastic resin B is supplied to the extruder 2 at 285 ° C.
These polymers are merged and laminated in a merging block (feed block), wound around a casting drum with a surface temperature of 30 ° C using an electrostatic application casting method, and cooled and solidified to form a two-layer unstretched film. made. At this time,
An unstretched film was prepared with the ratio of die slit gap / unstretched film thickness being 10. In addition, the discharge amount of each extruder was adjusted to adjust the total thickness and the thickness of the film layer A.
This unstretched film was stretched 4.0 times in the longitudinal direction at a temperature of 80 ° C. This stretching was performed in four stages with a difference in peripheral speed between two sets of rolls. This uniaxially stretched film is stretched 4.4 times in the width direction at 100 ° C. at a stretching speed of 2000% / min using a stenter.
Under constant length, heat treated at 200 ° C for 5 seconds, total thickness 9μm,
A biaxially oriented laminated film having a film layer A thickness of 0.2 to 6 μm was obtained.

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

・ Fe 100 parts Average size Length: 0.3μm Needle ratio: 10/1 Coercive force 2000Oe ・ 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 ・ 1 part of carbon black ・ 2 parts of lecithin ・ 100 parts of methyl ethyl ketone ・ 100 parts of methyl isobutyl ketone ・ 100 parts of toluene ・ 2 parts of stearic acid After mixing and dispersing the above composition for 48 hours with a pole mill, 6 parts of a curing agent The kneaded product obtained by adding is filtered through a filter to prepare a magnetic coating solution, coated on the thermoplastic resin B surface of the film, magnetically oriented, dried at 110 ° C., and further compacted with a small test calender ( After calendering with a steel roll / nylon roll (5 steps) at a temperature of 70 ° C. and a linear pressure of 200 kg / cm, curing was performed at 70 ° C. for 48 hours to obtain a video tape for high density recording.

The parameters of the present invention for these tapes are as shown in Table 1. When the parameters of the present invention are within the ranges, the scratch resistance, dubbing resistance and coefficient of friction are excellent or good as shown in Table 1. However, if not, a film having both scratch resistance, dubbing resistance and friction coefficient could not be obtained.

[Effects of the Invention] The present invention uses a thermoplastic resin containing particles to improve the relationship between the particle size and the film thickness,
The content or film thickness and the height distribution standard deviation of the surface protrusions of the non-magnetic surface and the relationship between the number of protrusions and the like are in a specific range or as a film or a laminated film thereof, so that the film has excellent scratch resistance and anti-dubbing properties. A video tape that can withstand high-density recording was realized.

Claims (8)

(57) [Claims] 1. A biaxially oriented thermoplastic resin film having a film layer A forming a non-magnetic surface and a magnetic layer, and a height distribution standard deviation σ (nm) of surface projections on the non-magnetic surface.
And the number N of protrusions exceeding 225 nm in height (number / mm ² ) is 0 ≦ (3σ).
-225) A video tape in which N <5 × 10 ⁴ , wherein the film layer A has a thickness of 0.005 to 3 μm containing thermoplastic resin A and particles as main components, and is contained in the film layer A. The average particle size of the particles is 0.1 to 10 times the thickness of the film layer A,
A video tape for high density recording wherein the content of the particles is 0.5 to 50% by weight. 2. The high-density recording according to claim 1, wherein the biaxially oriented thermoplastic resin film is a composite film comprising a film layer A and a film layer B containing a thermoplastic resin B as a main component. For videotape. 3. A biaxially oriented thermoplastic resin film is a composite film comprising a film layer A, a film layer B and a film layer A, wherein one film layer A forms a non-magnetic surface and the other film layer 2. The video tape for high density recording according to claim 1, wherein a magnetic layer is formed on A. 4. The video tape for high density recording according to claim 2, wherein the film layer B contains substantially no particles. 5. A film layer B comprising a thermoplastic resin B and particles having an average particle diameter of 0.007 to 2 μm as main components, wherein the content of the particles is 0.001 to 0.5% by weight.
Or the video tape for high density recording according to 3. 6. The film according to claim 1, wherein the thermoplastic resin A is a crystalline polyester and the total reflection Raman crystallization index of the surface of the film layer A is 20 cm ^-1 or less. The video tape for high-density recording according to 1. 7. Particles contained in the film layer A have a particle size ratio
The video tape for high density recording according to any one of claims 1 to 6, wherein the particles are particles of 1.0 to 1.3. 8. The video tape for high-density recording according to claim 1, wherein the relative standard deviation of the particles contained in the film layer A is 0.6 or less.