JPH04278350A - Biaxially oriented laminated polyester film - Google Patents

Abstract

PURPOSE:To enhance the high-speed cutting properties of a film suitable for the base material of a video tape and the electromagnetic conversion characteristics in high-speed magnetic field transfer by adding internal precipitation type particles to the outermost layer part of at least the single surface of a biaxially oriented laminated polyester film in a predetermined ratio. CONSTITUTION:In a biaxially oriented laminated polyester film having a laminated structure of at least three or more layers, an internal precipitation type particle having a good affinity for a base material and capable of forming a surface projection while achieving the strong bond with the base material is added to the outermost layer part of at least the single surface thereof. The content of the internal precipitation type particle in the outermost layer part is made larger than that in an intermediate layer part and a recycle polymer is added to the intermediate layer. The surface roughness parameter P10 of the outermost layer part is set to 350nm. The formation of the internal precipitation type particle is performed by adding a calcium compound in a process performing polycondensation through the direct esterification of predetermined dicarboxylic acid and ethylene glycol.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biaxially oriented laminated polyester film, and more particularly to a film suitable for use as a base material for standard type video tapes.

0002

BACKGROUND OF THE INVENTION Biaxially oriented polyester films, such as biaxially oriented polyester films that can be used as base materials for video tapes, include films containing substantially spherical silica particles derived from colloidal silica in polyester. is known (for example, Japanese Patent Application Publication No. 5
9-171623).

0003

[Problems to be Solved by the Invention] However, as the speed of film processing processes increases, particularly in magnetic layer coating, calendering and winding, and cassette assembly processes in magnetic media applications, the film surface is ,
In particular, there was a drawback that the surface of the film, which had minute irregularities, was easily scraped off. In addition, the conventional devices had the disadvantage that the image quality, that is, the S/N (signal/noise ratio), was insufficient because the image quality during dubbing deteriorated as the speed of dubbing increased due to high-speed magnetic field transfer.

The present invention solves these problems and makes it difficult for the surface of the film to be scraped off during high-speed processes (hereinafter referred to as "excellent high-speed scraping property"), and when used as a magnetic medium, there is little deterioration in image quality during dubbing. The object of the present invention is to provide a biaxially oriented laminated polyester film that has good electromagnetic conversion characteristics (hereinafter referred to as "excellent electromagnetic conversion characteristics"), is inexpensive, and is optimal as a base material for standard type video tapes.

[0005]

[Means for Solving the Problems] The biaxially oriented laminated polyester film of the present invention in accordance with this object has a biaxially oriented laminated polyester film having a laminate structure of at least three layers, in which the outermost layer of at least one side of the biaxially oriented polyester film has an internal structure. It contains precipitated particles, and the content of internally precipitated particles in the outermost layer is greater than the content in the middle layer.

First, the polyester film of the present invention must have a laminated structure of at least three layers. As long as there are three or more layers, it may be four or five layers, but a three-layer structure is preferred because the effects of the present invention are even better. However, single-layer or double-layer films cannot satisfy high-speed abrasion properties and electromagnetic conversion characteristics.

Next, the polyester film of the present invention is
At least one of the layers constituting this must be biaxially oriented. In a laminated structure of three or more layers, it is particularly preferable that all the layers are biaxially oriented. If all the layers are non-oriented or uniaxially oriented, the characteristics of the present invention cannot be satisfied.

The polyester constituting the present invention is not particularly limited, but includes ethylene terephthalate, ethylene α, β
It is particularly preferred 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. Among these, polyester containing ethylene terephthalate as a main component is particularly preferred. Note that two or more types of polyesters may be mixed or a copolymer may be used within a range that does not impede the present invention.

The polyester film of the present invention contains internally precipitated particles in the outermost layer on at least one side. These internally precipitated particles have good affinity with the base material and are capable of forming surface protrusions while achieving strong bonding with the base material. Since surface protrusions can be easily and inexpensively formed without incorporating external particles, a film with a surface morphology suitable for use as a base material for standard type video tapes, etc. can be obtained. By forming desired surface protrusions, high-speed machinability and electromagnetic conversion characteristics can be improved. Further, in the polyester film of the present invention, it is not necessary that the intermediate layer portion contains internally precipitated particles, but it is desirable that the intermediate layer portion also contains internally precipitated particles. In this case, it is necessary that the content of internally precipitated particles in the outermost layer is greater than that in the intermediate layer.

Regarding the protrusions on the outermost layer formed by the internally precipitated particles, the surface roughness parameter P1
0 is preferably 350 nm or less. If it is larger than this value, there is a risk that high-speed machinability will decrease and electromagnetic conversion characteristics will decrease.

[0011] Regarding the height of the protrusions on the surface of the outermost layer, it is preferable that the relative standard deviation of the protrusion height distribution is 1.2 or less. If the value is larger than this value, undesirable coarse protrusions will be present, and these portions will be likely to be scraped off, leading to a decrease in high-speed scraping properties and a risk of deterioration in electromagnetic conversion characteristics.

Furthermore, in the film of the present invention, although the intermediate layer is not particularly limited, the outermost layer has a surface that is excellent in high-speed abrasion properties, has protrusions of a uniform desired protrusion height, and has excellent electromagnetic conversion characteristics as described above. Therefore, it is preferable that the intermediate layer contains a so-called recycled polymer. Note that the recycled polymer herein refers to a polyester having a terminal carboxylic acid of 55 equivalents/10 6 g or more and a polymer solution haze of 18% or less.

The outermost layer of the biaxially oriented laminated polyester film of the present invention may contain external particles in addition to the internally precipitated particles, but the content is greater than that of the internally precipitated particles. It is preferable to avoid deterioration of high-speed machining properties and electromagnetic conversion characteristics by not causing too much.

The film of the present invention may also contain other polymers, such as antioxidants, heat stabilizers, lubricants, and ultraviolet absorbers, as long as they do not impede the purpose of the present invention. Organic additives may be added to the extent that they are normally added.

It is particularly preferable that the polymer IV of the outermost laminated portion of the laminated polyester film of the present invention is in the range of 0.4 to 0.9, since this further improves high-speed abrasion properties. Furthermore, it is very preferable that the difference in polymer IV from the base layer portion is within 0.1 because high-speed machinability becomes even better.

Next, a method for manufacturing the film of the present invention will be explained. First, the following method is effective for producing internally precipitated particles. In other words, internally precipitated particles undergo polycondensation through direct esterification of a predetermined dicarboxylic acid and ethylene glycol, or ■polycondensation through a transesterification reaction between dimethyl ester of a predetermined dicarboxylic acid and ethylene glycol. In the process, at least one of glycol-soluble calcium compounds, magnesium compounds, manganese compounds, and lithium compounds,
Preferably, it is produced by adding phosphorus acid and/or ester compounds in a suitable manner. The addition of the compound to produce the internally precipitated particles can be carried out at any time from the point at which the esterification or transesterification reaction is substantially completed to the early, less advanced stage of the polycondensation reaction, by adding a calcium compound, It is preferable to add at least one lithium compound to the reaction system as a glycol solution.

Calcium, magnesium, manganese, and lithium compounds that can be used here include halides, inorganic acid salts such as nitrates and sulfates, organic acid salts such as acetates, oxalates, and benzoates, and hydrides. Glycol-soluble compounds such as and oxides are most preferably used, but two or more types may be used in combination. Further, as the phosphorus compound, one or more of phosphoric acid, phosphorous acid, phosphonic acid, and esters and partial esters thereof are used. In the production of internally precipitated particles, it is preferable not to use inorganic particles or the like as a crystal nucleating agent.

As a method for adjusting the amount of internally precipitated particles, a highly concentrated particle master is prepared by the method described above, and then diluted with polyester that does not substantially contain internally precipitated particles during film formation. An effective method is to control the amount of precipitated particles.

Next, the polyester pellets are used to form a polyester film having a laminated structure of three or more layers. The polyester pellets obtained by the above method are mixed in a predetermined ratio, dried, and then fed to a known extruder for melt lamination, extruded into a sheet through a slit die, and cooled and solidified on a casting roll. At least make an unstretched film. That is, the sheets are laminated using two or three or more extruders, a manifold with three or more layers, or a merging block (for example, a merging block with a square merging part), extruding three or more layers of sheets from a die, and cooling with a casting roll. to make an unstretched film. In this case, it is effective to install a static mixer or a gear pump in the polymer flow path. Furthermore, it is effective to lower the melting temperature of the extruder for extruding the polymer on the outermost layer layer side by 5 to 10° C. than on the base layer side.

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, a sequential biaxial stretching method is used in which stretching is first performed in the longitudinal direction and then in the width direction, and the longitudinal stretching is divided into three or more stages, with a total longitudinal stretching ratio of 3.5 to 6.5 times. The method is particularly preferred. The stretching temperature in the longitudinal direction varies depending on the type of polyester and cannot be generalized, but usually the first stage is 50 to 1
It is effective to set the temperature to 30°C and raise the temperature higher than that for the second and subsequent stages. The longitudinal stretching speed is 5,000 to 50,000%/
A range of minutes is preferred. A common method for stretching in the width direction is to use a stenter. The stretching ratio is 3.0
A range of 5.0 times is appropriate. The stretching speed in the width direction is
Preferably, the rate is 1,000 to 20,000%/min and the temperature is in the range of 80 to 160°C. Next, this stretched film is heat treated. The heat treatment temperature in this case is 170-220℃, especially 18
Preferably, the temperature is 0 to 200°C and the time is 0.2 to 20 seconds.

[Method for Measuring Physical Properties and Evaluating Effects] Methods for measuring characteristic values and evaluating effects of the present invention are as follows. (1) Standard deviation of height distribution of surface protrusions Two-detector scanning electron microscope [ESM-3200,
manufactured by Elionix Co., Ltd.] and a cross-sectional measuring device [PMS-1,
The height of the protrusions was measured using an image processing device [IBAS2000, Carl Zeiss Co., Ltd.] when the height of the flat surface of the film was set as 0.
[Manufacturer] and reconstructs the image of the film surface protrusions on an image processing device. Next, a circular equivalent diameter is determined from the area of each protrusion obtained by binarizing the protrusion portion using this surface protrusion image, and this is taken as the average diameter of the protrusion. Furthermore, the highest value among the binarized individual protrusion portions is determined as the height of the protrusion, and this value is determined for each protrusion. This measurement is repeated 500 times at different locations, and the height distribution of the measured protrusions is normal distribution (normal distribution centered on the point of height 0)
The standard deviation of the height distribution was determined by approximation using the least squares method. Furthermore, the magnification of a scanning electron microscope is 1000 to 8
Select between 000 times.

(2) Surface roughness parameter P10 Using an optical interference type three-dimensional surface analyzer (TOPO-3D manufactured by WYKO, objective lens: 40 to 200 times, effective use of a high-resolution camera), to construct a film surface protrusion image. In this surface protrusion image, the average of the 10 points from the highest value of the protrusion portion was defined as P10. The average value of 20 measurements was taken as the value (unit: nm).

(3) Polymer IV Measured at 25°C using o-chlorophenol as a solvent.

(4) Press one blade against a 1/2-inch wide tape-shaped slit of high-speed abrasion film at an angle of 90°, push it in 0.5 mm, and run it for 200 m (speed: 200 m/min, tension: 100g). The adhesion height of the powder scraped off by one blade was read using a microscope and was defined as the scraping amount (μm). If the amount of abrasion is 180 μm or less, the abrasion resistance is good, and if it exceeds this, the abrasion resistance is poor.

(5) A magnetic paint having the following composition is applied to the electromagnetic conversion film using a gravure roll, magnetically oriented, and dried. In addition, a small test calender device (steel roll/nylon roll,
5 stages) at a temperature of 70°C and a linear pressure of 200 kg/cm 2 , followed by curing at 70°C for 48 hours. The original tape was slit into 1/2 inch pieces to make pancakes. A length of 250 m from this pancake was assembled into a VTR cassette to make a VTR cassette tape. (Composition of magnetic paint) ・Co-containing iron oxide:
100 parts by weight of vinyl chloride/vinyl acetate copolymer:
10 parts by weight polyurethane elastomer
: 10 parts by weight polyisocyanate
: 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 A 100% chroma signal was recorded on this tape using a TV test waveform generator using a home VTR, and the chroma S/N was measured from the reproduced signal using a color video noise measuring device.

[0026]

EXAMPLES Next, embodiments of the present invention will be described based on examples. Example 1 (Table 1) 50 parts by weight of pellets containing internally precipitated particles and 50 parts by weight of polyethylene terephthalate pellets containing no particles were mixed together, supplied to a vented twin-screw kneading extruder 1, and melted at 280°C. (Polymer I). Furthermore, another extruder 2 was prepared, and after mixing 35 parts by weight of recycled polymer and 65 parts by weight of pellets containing no particles, the mixture was dried under reduced pressure (3 Torr) at 180°C for 3 hours and then fed to the extruder. (Polymer II). This 2
After high-precision filtration of each of the two polymers, they were laminated in a three-layer merging block with a rectangular laminated part so that Polymer II was placed on the base layer part and Polymer I was placed on the double-sided surface laminated part, and a fishtail-shaped cap was formed. After extruding it into a sheet, it is wrapped around a casting drum with a surface temperature of 30°C using an electrostatic casting method and cooled and solidified to a thickness of approximately 160°C.
An unstretched film of μm was made. The draft ratio at this time was 6.5.

This unstretched film was divided into three stages in the longitudinal direction, 1.2 times at 123°C, 1.45 times at 126°C, and 1
Each was stretched 2.3 times at 14°C. This uniaxial film was divided into two stages in the width direction using a stenter, stretched 3.7 times at 111°C and 1.2 times at 113°C, and stretched 200 times at a constant length.
A heat treatment was performed at .degree. C. for 5 seconds to obtain a film with a thickness of 13 .mu.m.

The electromagnetic conversion characteristics of this film were measured and found to be +2.0. In addition, high-speed machinability is 85 (μm)
It was good. As described above, when the types of particles contained in the outermost laminated portion and the laminated structure are within the scope of the present invention, a film having good electromagnetic conversion characteristics and high-speed abrasion properties can be obtained.

Example 2, Comparative Examples 1 to 4 (Table 1) Example 1
A biaxially oriented polyester film was prepared in the same manner as above, but if the presence or absence of internally precipitated particles in the outermost layer and the laminated structure are not within the scope of the present invention, electromagnetic conversion characteristics,
A film with good high-speed abrasion properties could not be obtained.

[0030]

[Table 1]

[0031]

Effects of the Invention According to the biaxially oriented laminated polyester film of the present invention, uniform and hard-to-scrape protrusions are formed on the surface of the outermost layer of the thin layer on at least one side by the internally precipitated particles, and the desired surface roughness can be achieved. Therefore, it is possible to exhibit excellent abrasion resistance at high speeds and to exhibit excellent electromagnetic conversion characteristics for use in magnetic media.

[0032] Furthermore, since the outermost layer can have the above-mentioned excellent properties, the intermediate layer can contain a recycled polymer without causing any problems, and productivity can be improved. .

Claims (4)

[Claims] Claim 1: A biaxially oriented laminated polyester film having a laminated structure of at least three layers, wherein the outermost layer of at least one side thereof contains internally precipitated particles, and the content of internally precipitated particles in the outermost layer is A biaxially oriented laminated polyester film characterized in that the content is higher than that in the middle layer. 2. The biaxially oriented laminated polyester film according to claim 1, wherein the intermediate layer portion contains a recycled polymer. [Claim 3] Surface roughness parameter P of the outermost layer portion
The biaxially oriented laminated polyester film according to claim 1 or 2, wherein 10 is 350 nm or less. 4. The biaxially oriented laminated polyester film according to claim 1, wherein the relative standard deviation of the protrusion height distribution on the surface of the outermost layer portion is 1.2 or less.