JPH06106614A - Polyester film for magnetic recording - Google Patents

Abstract

PURPOSE:To manufacture a film with its surface not chipped off when the film travels at high speed in VTR by specifying the content of a dispersed polymer dispered in a dispersed layer, specifying the ratio between the thickness of the dispersed layer and the average particle diameter of the dispersed polymer component and also specifying the ratio of the total thickness of the dispersed layer occuping in the total film thickness. CONSTITUTION:The content of dispersed polymer dispersed in a dispersed layer is specified as 1-45wt.%, and the ratio t/d between the thickness (t) of dispersed layer and the average particle diameter (d) of dispersed polymer component satisfies the formula -0.1<=t/d<=10-, and the total thickness of dispersed layer in the total film thickness is specified as 17% or less. A biaxially oriented film is composed of the dispersed layer composed of a composition of a polymer mixed and dispersed in polyester at least on one face of a base layer film composed of a polyester composition. It is particularly desirable to use a copolymer polyester (liquid crystal polyester) for forming an anisotropic molten substance as the dispersed polymer from the viewpoint of uniformity of dispersion.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a polyester film.

[0002]

2. Description of the Related Art As a polyester film used for magnetic recording, a composition containing inorganic or organic particles is laminated on at least one surface of a base layer, and the relationship between the particle diameter and the laminated thickness is specified. A material having improved wear resistance is known (for example, Japanese Patent Laid-Open No. 2-77431).

[0003]

However, recently, in a video tape, which is one of the applications for magnetic media, the VTR search mechanism has been speeded up, and fast forward / rewind (FF / RE) has been performed.
W) As the time is shortened, the surface of the polyester film on the back surface of the tape is scraped off at the time of high-speed running, and a problem that powder is generated has become apparent.

It is an object of the present invention to solve the above problems and to provide a film (hereinafter referred to as FF / REW property good) in which the surface is not scraped even when traveling in a VTR at high speed (fast forward and rewind). To do.

[0005]

In order to achieve the above-mentioned object, the present invention laminates a dispersion layer made of a polyester composition obtained by mixing and dispersing a polymer on at least one surface of a base layer made of a polyester composition. The content of the dispersed polymer dispersed in the dispersion layer is 1 to 4
5% by weight, the ratio t / d of the dispersion layer thickness t to the average particle diameter d of the dispersion polymer component satisfies the following expression (1), and the total thickness of the dispersion layer in the entire film thickness is 17%. The polyester film for magnetic recording is characterized by the following.

0.1 ≦ t / d ≦ 10 (1) The polyester composition constituting the base layer of the present invention is not particularly limited, but it may be composed of ethylene terephthalate and ethylene 2,6-naphthalate units. When at least one selected structural unit is the main constituent, the FF / REW property is further improved, which is desirable.

The present invention is a film comprising a base layer film made of the above polyester composition and a dispersion layer made of a composition obtained by mixing and dispersing a polymer in polyester on at least one surface of the base layer film. The type is also not particularly limited, and may be the same as or different from the polyester of the base layer part. However, ethylene terephthalate, ethylene α, β-bis (2-chlorophenoxy) ethane-4,4′-dicarboxylate
And FF / when at least one structural unit selected from ethylene 2,6-naphthalate units is the main constituent.
It is desirable because the REW property is further improved.

The polymer (dispersion polymer) to be blended and dispersed in the polyester is not particularly limited, but it is necessary that it is incompatible with the polyester to some extent. Completely compatible is not preferable because projections are not formed on the surface, and too incompatible is not preferable because surface roughness becomes too large. In that sense, polyesters, polyamides, polyetheresters and the like are desirable, and particularly, copolyesters (liquid crystal polyesters) capable of forming an anisotropic melt are particularly desirable in terms of dispersion uniformity.

It is necessary that the dispersion polymer mixed and dispersed in the polyester is 1 to 45% by weight, preferably 2 to 30% by weight, more preferably 3 to 25% by weight, based on the entire dispersion layer. If the content is more or less than the above range, the FF / REW property becomes poor, which is not preferable. It should be noted that the number of polymers to be mixed / dispersed may be two or more, not one, but the total amount must be within the above range.

The dispersion layer of the film of the present invention contains the above-mentioned composition as a main component, but may be blended with other polymers within a range that does not impair the object of the present invention, and may contain an antioxidant and a heat stabilizer. Organic additives such as agents, lubricants, ultraviolet absorbers and antistatic agents may be added to the extent that they are usually added.

The present invention is a biaxially oriented film in which the above composition is laminated on at least one side of the above-mentioned base layer polyester composition, and has a thickness t of the dispersion layer and a dispersion diameter of the dispersion polymer dispersed as described above. (Average particle size) ratio of d, t / d
Should be in the range of 0.1 to 10, preferably 0.2 to 5, and more preferably 0.2 to 2. t /
If d is smaller or larger than the above range, F
It is not preferable because the F / REW property becomes poor.

Further, it is necessary that the ratio of the thickness of the dispersion layer of the present invention (the total thickness of each dispersion layer in the case of three or more layers) to the total film thickness is 17% or less. If the thickness ratio of the dispersion layer is larger than the above range, not only the strength and tear resistance of a magnetic medium such as a magnetic tape will be poor, but also the FF / REW property will be poor, which is not preferable. The layer thickness of the dispersion layer is preferably 16% or less,
It is more preferably 15% or less.

In the dispersion layer, the formula: 0.1 ≦ t
The number of dispersed polymer particles satisfying the relationship of / d ≦ 10 is 3 × 1.
0 ³ to 8 × 10 ⁷ pieces / mm ² , more preferably 5 × 10
FF / REW when ³ to 1 × 10 ⁶ pieces / mm ²
It is desirable because the property is further improved.

In the cross section of the film, the ratio of the average of the major axis to the average of the minor axis of the dispersion diameters of the dispersion polymer in the dispersion layer (major axis /
When the (minor diameter) is 1.6 or less, more preferably 1.4 or less, the FF / REW property is further improved, which is desirable.

Further, in the cross section of the film, when the average dispersion diameter of the dispersion polymer of the dispersion layer is 0.1 to 3 μm, more preferably 0.2 to 2 μm, the FF / REW property is further improved, which is desirable. .

Further, when the relative standard deviation of the height distribution of the surface protrusions of the dispersion layer is 0.7 or less, more preferably 0.5 or less, the FF / REW property is further improved, which is desirable.

The average height of the surface protrusions of the dispersion layer is 20 to 20.
In the case of 800 nm, particularly in the range of 30 to 600 nm, the FF / REW property is further improved, which is extremely desirable.

The number of surface protrusions on the dispersion layer is 5 × 1.
FF / when the range is 0 ^{3 to} 5 × 10 ⁷ pieces / mm ^2.
The REW property is further improved, which is extremely desirable.

Further, the surface roughness Ra of the dispersion layer is 10-5.
In the range of 0 nm, the FF / REW property is further improved, which is extremely desirable. Further, when the maximum height Rt is 10 times or less of Ra, the FF / REW property is further improved, which is extremely desirable.

As described above, the present invention may be a biaxially oriented film, and a uniaxial or non-oriented film may be FF.
It is not preferable because the / REW property becomes poor. The degree of this orientation is not particularly limited, but the Young's modulus, which is a measure of the degree of molecular orientation of the polymer, is 400 k in both the longitudinal and width directions.
When it is g / mm ² or more, the FF / REW property is further improved, which is extremely desirable. Although the upper limit of the Young's modulus, which is a measure of the degree of molecular orientation, is not particularly limited, it is usually
The manufacturing limit is about 1500 kg / mm ² .

Further, by increasing the Young's modulus in the transverse direction of the film to be larger than that in the longitudinal direction, preferably 50 kg / mm ² or more, and combining the lamination, FF / R
The EW property can be further improved.

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

First, as a method for dispersing a polymer which is incompatible to some extent in the polyester A to be the dispersion layer, kneading using a vent type twin-screw kneader is effective for obtaining the dispersed state of the present invention. Is. In this case, the melt viscosity of a polymer which is incompatible to some extent at 290 ° C. is measured at a shear rate of 1000 s ^−1.
So, keep it in the range of 500-5000 poise,
It is effective for obtaining the dispersed state of the present invention.

After the mixed composition is dried, it is supplied to a known melt extruder 1 to form polyester B (A, B) as a base layer.
The same kind or different kinds) may be supplied to the extruder 2.
Alternatively, using a three-layer manifold or a confluent block, the mixed composition is laminated on at least one side of polyester B, a two- or three-layer sheet is extruded from a slit-shaped die, and cooled with a casting roll to obtain an unstretched film. make. In this case, the method of stacking using a merge block having a rectangular merge cross section is effective in obtaining the relationship between the dispersion diameter and the laminate thickness of the present invention, and is also effective in reducing breakage during stretching. is there. In addition, the dispersion layer portion (extrusion of the polymer mixed raw material, when using a vent type twin-screw extruder,
It is extremely effective for obtaining the relationship between the dispersed diameter and the laminated thickness and the dispersed state of the present invention.

Next, this unstretched film is biaxially stretched,
It is biaxially oriented. As a 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 is first performed in the longitudinal direction and then in the width direction, stretching in the longitudinal direction is divided into two or more steps, and the area ratio (longitudinal stretching ratio x width-direction stretching ratio) is 10 to 10.
The ratio of 40 times is effective for obtaining the polymer content, the relationship between the dispersed diameter and the laminated thickness, and the dispersed state within the scope of the present invention without stretching breakage.

The stretching temperature in the longitudinal direction and the stretching direction in the width direction varies depending on the type of polyester and cannot be generally stated, but is usually 5
The range of 0 to 130 ° C. is effective for producing a film having a polymer content within the range of the present invention without stretching break. The longitudinal stretching speed is preferably in the range of 5,000 to 50,000% / min. Stretching speed in the width direction is 1000 to 20000%
/ Min, the temperature is preferably in the range of 80 ~ 160 ℃. Alternatively, the biaxially stretched film may be further stretched in at least one direction. Next, this stretched film is heat-treated. The heat treatment temperature in this case is 0.5 to 5 seconds, which is equal to or higher than the melting point of the polymer mixed in the dispersion layer.
Polymer content in the range of the present invention, the relationship between the dispersion diameter and the laminated thickness,
It is effective in obtaining the dispersed state.

[0027]

[Physical property measuring method and effect evaluating method] The characteristic value measuring method and effect evaluating method of the present invention are as follows.

(1) Dispersion particle size and number of dispersion polymer The cross section of the film was measured with a transmission electron microscope to 3000-1.
Observe at 00000 magnification. The thickness of the section was set to about 100 nm, and the measurement was performed at different places. The dispersed particle size is 5 dispersed particles.
With 000 particles, the volume average diameter d was obtained from the following equation from the particle diameter and its volume fraction. Here, di is the particle size and NVi is the logarithmic integration rate. Further, the number of particles per unit area (particles / mm ² ) was calculated from the visual field measured at this time. d = Σdi · NVi

(2) Ratio of major axis / minor axis of dispersed particles By the above method, the major axis dL and dS of each particle were determined by the following equation, and the ratio, dL / dS, was defined as the major axis / minor axis ratio. dL = ΣdLi · NVi dS = ΣdSi · NVi

(3) Thickness t of Dispersion Layer By changing the dispersion state in the above cross-section observation, the difference in contrast between polymer and polyester, XPS (X-ray photoelectron spectroscopy) while etching from the surface, infrared spectroscopy, etc. Recognize the interface and determine the stack thickness. Alternatively, after peeling off the dispersed layer, the laminated thickness can be obtained using a thin film step measuring machine.

(4) Average Height of Surface Protrusion 2 Detector type scanning electron microscope [ESM-3200,
Elionix Co., Ltd.] and cross-section measuring device [PMS-1,
Elionix Co., Ltd.], the height of the flat surface of the film surface is measured as 0, and the measured height of the projection is measured by an image processing apparatus [IBAS2000, Carl Zeiss Co., Ltd.].
Manufactured] to reconstruct the film surface projection image on the image processing device. Next, the equivalent circle diameter is calculated from the area of each protrusion obtained by binarizing the protrusion portion in this surface protrusion image, and this is made the average diameter of the protrusion. In addition, the highest value among the binarized individual projection portions is set as the height of the projection, and this is obtained for each projection. This measurement was repeated 500 times at different places to determine the number of protrusions, and the average value of the heights of all the measured protrusions was taken as the average height. In addition, the standard deviation of the height distribution was calculated based on the height data of each protrusion. The magnification of the scanning electron microscope is 1000
Select a value between ~ 8000 times. In some cases, the height information obtained using a high-precision optical interference type three-dimensional surface analyzer (TOPO-3D manufactured by WYKO, objective lens: 40 to 200 times, use of a high resolution camera is effective) is used for the SEM. You may read and use it for the value of.

(5) Relative standard deviation of protrusion height distribution The value obtained by dividing the standard deviation of the protrusion height distribution obtained by the above method by the average height was taken as the relative standard deviation of the protrusion height distribution.

(6) Center line average surface roughness Ra and maximum height Rt Measured using a high precision thin film step measuring instrument ET-10 manufactured by Kosaka Laboratory. The conditions are as follows, and the average value of 20 measurements was used as the value.・ Stylus tip radius: 0.5 μm ・ Stylus load: 5 mg ・ Measurement length: 1 mm ・ Cutoff value: 0.08 mm Ra and Rt are defined, for example, by Jiro Nara, “Measurement / Evaluation of Surface Roughness”. Law "(General Technology Center, 198
3).

(7) Young's modulus According to the method specified in JIS-Z-1702,
25 using an Instron type tensile tester
It was measured at 65 ° C. and 65% RH.

(8) FF / REW property A magnetic coating composition having the following composition is applied to a film by a gravure roll, magnetically oriented, and dried. In addition, a small test calendar device (steel roll / nylon roll,
(5 stages), after calendering at a temperature of 70 ° C. and a linear pressure of 200 kg / cm, curing is performed at 70 ° C. for 48 hours. The above tape raw fabric was slit into 1/2 inch to prepare a pancake. A length of 250 m from this pancake was incorporated into a VTR cassette to obtain a VTR cassette tape. (Composition of magnetic paint) -Co-containing iron oxide (BET value 50 m ² / g): 100 parts by weight-ESREC A (Sekisui Chemical's vinyl chloride / vinyl acetate copolymer: 10 parts by weight) -Nipporan 2304 (Nippon Polyurethane Polyurethane) Elastomer: 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 This tape was fast forwarded using a home VTR and rewound 300 times each, and the white powder on the metal pins in the VTR cassette was observed and the part where the tape contacted FF / REW when the area ratio of the white powder adhesion part to the area of : ◎, 5~10% of the FF / REW of:
◯: 10% to 30% was judged as Δ, and when it exceeded it, it was judged as ×. ◎ and ○ are good levels in use.

[0036]

EXAMPLES The present invention will be described based on examples.

Examples 1 to 5 and Comparative Examples 1 to 4 Polyethylene terephthalate (hereinafter referred to as PET) having an intrinsic viscosity of 0.65 produced by a known method and a predetermined amount of various polymers were kneaded by a vent type twin screw mixer. Made a polyester mixture.

These polymers were dried under reduced pressure (3 Torr) at 180 ° C. for 3 hours, and similarly dried, P having an intrinsic viscosity of 0.65.
Each of the ETs was fed to two extruders, melted at 290 ° C., and these polymers were combined and laminated with a rectangular confluent block (feed block) for 2 or 3 layers, and the electrostatic applied cast method was used. Casting with surface temperature of 30 ℃
It was wound on a drum and solidified by cooling to prepare an unstretched film having a 2-3 layer structure. At this time, the discharge amount of each extruder was adjusted to adjust the total thickness and the thickness of the polyester mixture layer.

This unstretched film was stretched at a temperature of 80 ° C. in the longitudinal direction at a first stage of 1.5 times and a second stage of 3 times a total of 4.5 times. This stretching was performed with the difference in peripheral speed between the two sets of rolls. This uniaxially stretched film is stretched at a stretching speed of 5000 using a stenter.
The film was stretched 4.0% in the width direction at 100 ° C. at a rate of 100% / min, and heat-treated at 200 ° C. for 5 seconds under a constant length to obtain a biaxially oriented laminated polyester film having a total thickness of 14 μm. The parameters of the present invention for these films are as shown in Table 1. When the parameters of the present invention are within the range, FF / RE is set.
It is understood that the film has excellent W property, but if it is not the case, the purpose cannot be achieved.

[0040]

[Table 1] In Table 1 above, Examples 1 to 5 and Comparative Examples 1 to 4 are laminated on both sides with three layers, and Example 6 and Comparative Example 4 are two layers with one area layer (a magnetic layer is provided on the side opposite to the laminated surface). It was done.
The types of dispersion polymer are as follows.

A: PET with parahydroxybenzoic acid 6
0 mol% copolymerization (melt anisotropy) B: 80 mol% parahydroxybenzoic acid copolymerized with PET (melt anisotropy) C: polyarylate D: 30 mol% parahydroxybenzoic acid copolymerized with PET (Melting isotropic)

[0042]

Industrial Applicability According to the present invention, a polymer is mixed with polyester to form an appropriate dispersed state, and the particles are positionally regulated with the diameter and the laminated thickness of the dispersed particles within a specified range, and the laminated thickness ratio falls within a specified range. Therefore, a support film for a magnetic recording medium is completed in which the surface is not scraped even when traveling at high speed (fast forward and rewind) in a VTR.

Front page continuation (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location G11B 5/704 7215-5D // B29K 67:00 B29L 7:00 4F 9:00 4F

Claims (6)

[Claims] 1. A film comprising a base layer made of a polyester composition and a dispersion layer made of a polyester composition having a polymer mixed and dispersed on at least one surface thereof, the dispersion polymer being dispersed in the dispersion layer. 1 to 4
5% by weight, the ratio t / d of the dispersion layer thickness t to the average particle diameter d of the dispersion polymer component satisfies the following expression (1), and the total thickness of the dispersion layer in the entire film thickness is 17%. A polyester film for magnetic recording, characterized in that: 0.1 ≦ t / d ≦ 10 (1) 2. In the dispersion layer, the number of particles due to the dispersion polymer satisfying the relationship of formula (1) is 3 × 10 ³ to 8 × 1.
The polyester film for magnetic recording according to claim 1, characterized in that the number is 0 ⁷ pieces / mm ² . 3. The polyester film for magnetic recording according to claim 1, wherein in the dispersion layer, the ratio of major axis / minor axis of the dispersion polymer in the film cross section is 1.6 or less. 4. The polyester film for magnetic recording according to claim 1, wherein in the dispersion layer, the average dispersion diameter of the dispersion polymer in the film cross section is 0.1 to 3 μm. 5. The relative standard deviation of the height distribution of the surface protrusions of the dispersion layer is 0.7 or less.
6. A polyester film for magnetic recording according to any one of 1. 6. The dispersion polymer is a copolyester capable of forming an anisotropic melt.
6. The polyester film for magnetic recording according to any one of 5 above.