KR890004389B1 - Oriented poly joint polyester film - Google Patents

Abstract

The polyester film having an improved slip property, drop-out and electronical property is prepd. Thus, polyester layer (A) contg. 0.07 wt.% 0.04 μm TiO2 and polyester layer (B) contg. 0.02 wt.% 0.5μm CaCO3 is coextruded at 275≰C, 285≰C resp., and cooled fast on cooling roller at 50≰C to make 200 μm non-stretched polyester coextrusion sheet. The sheet is drawn at 90≰C to machine direction by the drawing ratio of 3.3 and is drawn again in the cross direction of machine by drawing ratio of 3. The center line av. roughness and max. roughness of (A) layer are 0.007 and 0.08 μm resp., while (B) layer are 0.028 and 0.35 m resp.

Description

Biaxially Stretched Multilayer Polyester Film

The present invention relates to a biaxially stretched multilayer polyester film.

In particular, the present invention relates to a biaxially-stretched multilayer polyester film having improved dropout and electronic properties in addition to improving the activity of magnetic tape in a polyester base film.

Biaxially oriented films made of polyester such as polyethylene terephthalate and polyethylene naphthalate have excellent mechanical strength, thermal stability, chemical stability, and electrical insulation, and are widely used in magnetic tape, graphic art, stamping foil, packaging, and various electrical insulation applications. have.

However, there are some problems in the use of magnetic tapes, especially video tapes having high recording frequency and requiring high speed recording and reproducing.

One of them is that the friction coefficient of the base film is high. Films used in video tapes require surface smoothness in addition to mechanical strength and thermal stability.

However, the improvement of surface smoothness results in high coefficient of friction. The base film with good runability up to now has many defects such as a low coefficient of friction and a poor bundle of dropouts and poor electronic properties during greening and regeneration.

On the other hand, a low coefficient of friction is required in order to have a good wound state of the film in the film forming process, to have good electronic properties of the magnetic tape, and to have good electronic properties of the magnetic tape.

In order to satisfy the contradictory properties required in such a base film, the surface roughening and the subsequent activity improvement are improved by adding inorganic fine particles in polyester, generating internally produced fine particles or embossing during post processing. However, in any case, it was difficult to use as a base film of magnetic tape due to not only mechanical properties, chemicals and physical properties but also dropouts and poor image quality.

Another problem is that the uncoated side of the magnetic tape rubs with the guide pin of the video tech or the metal guide pin of the cassette during recording, resulting in scratches or abrasion on the film surface. In some cases, a multilayer film having an extremely smooth layer that is not added and a roughened layer in which an appropriate amount of inert fine particles are added may be used, but in this case, the layer to which the fine particles are not added is too smooth so that a flaw may occur in the film forming process. There was a flaw, which was susceptible to friction from layers. Such flaws and abrasion are more severely generated during repeated use, which severely degrades the tape quality during repeated use.

In order to solve this problem, the back coating may be performed on the non-coated side of the magnetic tape, but this increases not only the manufacturing cost of the magnetic tape but also a problem of peeling due to the coating material or durability of the coating layer.

The present invention, as a result of earnestly examining in order to solve all the problems of the polyester film used for the magnetic tape as described above is as follows.

The centerline average roughness (Ra) value is in the range of 0.001-0.01μ, and the polyester layer (A) having fine surface roughness having a maximum surface roughness (Rmax) of 0.1μ or less and the centerline average roughness (Ra) value are 0.01-0.05μ. And a polyester film for biaxially stretched magnetic tape having an asymmetric structure with a polyester layer (B) having a surface roughness Rmax of 0.5 μm or less.

In the present invention, in the resin of the polyester layer (A), inert fine particles having a diameter of 0.01-0.1 μm are preferably 0.01-0.1 wt%, preferably 0.01-0.05 wt%, of 0.02-0.06 μ inert fine particles. The inert fine particles may contain at least one of silicon dioxide, titanium dioxide and synthetic calcium carbonate.

The resin of the polyester layer (B) preferably contains 0.01-0.5% by weight, preferably 0.05-0.3% by weight, of inert fine particles having a diameter of 0.1-5 mu, preferably 0.5-2 mu, It is preferable to contain at least one of titanium dioxide, silicon dioxide, calcium carbonate, kaolin, mica, aluminum hydroxide, barium sulfide, talc and synthetic zeolite.

In the present invention, the biaxially stretched polyester film has a thickness of 5 µ-20 µ, preferably 7-15 µ, and a ratio of the thickness of the polyester layer (A) and the polyester layer (B) is 2: 1-7: 1 Preferably, 3: 1-5: 1 is good, and it is good that the thickness of a polyester layer (B) is 3 micrometers or less.

In the present invention, the term "polyester" refers to polyesters made of difunctional acids and glycols, or copolymers or mixtures thereof.

The acid component of the polyester is mainly terephthalic acid, but at least 90 mol% of terephthalic acid, preferably at least 95 mol% and, for example, 10 mol% of one or more of difunctional acids such as isophthalic acid, phthalic acid, adipic acid, and sebacic acid. Preferably, the copolymer may be 5 mol% or less, and the component of glycol is mainly ethylene glycol, but 90 mol% or more, preferably 95 mol% or more, for example polyethylene glycol, nucleoethylene glycol, propylene It may be 10 mol% or less, preferably a copolymer of 5 mol% or less, or a mixture thereof.

And here, you may mix additives, such as a stabilizer, a coloring agent, antioxidant, an antistatic agent, and a brightener.

In the present invention, the homogeneous polyester means a polyester obtained from homogeneous monomers and has the same repeating unit in the structure of the polyester, but does not significantly change the structure of each polyester. The composition of coalescence may be sufficient.

The multi-layered structure of the present invention refers to a structure of two or more layers, and the polyester layer (A) refers to one outer layer and is mainly coated in the manufacturing process of the magnetic tape, and the polyester layer (B) refers to the outer layer on the opposite side. Mainly refers to the layer where friction occurs with the guide pin of the cassette when driving.

In lamination | stacking, only a polyester layer (A) and a polyester layer (B) may be sufficient, and the other polyester layer may be thin several micrometers between a polyester layer (A) and a polyester layer (B).

The polyester base film of the present invention not only has good mechanical strength and thermal stability, but also divides the problems of opposing electronic properties and runability in the magnetic tape to each outer layer, thereby sharing a low coefficient of friction and activity such as a conventional biaxial operation. It can exhibit improved electronic properties.

In addition, in the differentiation of each layer, it is possible to think of a method of not inserting fine particles into one outer layer, but in the film forming process, it still suffers from flaws from each roll during driving and a problem of abrasion. The flaw is flawed.

The laminated film of the present invention is characterized by being capable of satisfying excellent running characteristics and electronic properties by forming appropriate roughness on the outer layer, respectively.

In the present invention, the thickness of the polyester (A) and the polyester layer (B) is very important, and if the thickness of the polyester layer (B) becomes too thin, the uniform surface roughness value of the polyester layer (B) cannot be maintained. Increases dropouts due to irregular driving.

When the thickness of the polyester layer (B) becomes thick, the effect of adding the inert fine particles of the polyester layer (B) is transferred to the polyester layer (A), resulting in poor adhesion to the video head during running of the tape, resulting in poor electronic properties.

This effect is also related to the thickness of the biaxially stretched film. When the thickness is thin, the effect of the polyester layer (B) is easily transferred to the polyester layer (A), and when the thickness becomes thick, the inert fine particles of the polyester layer (B) The addition effect is slowed down.

Therefore, the polyester layer (A) and the polyester layer (B) should be maintained in an appropriate thickness.

Example 1

A polyester layer (A) containing 0.07% by weight of titanium dioxide having a diameter of 0.04μ and a polyester layer (B) containing 0.2% by weight of 0.5μ of calcium carbonate were supplied from a compressor, respectively, at 275 ° C and 285 ° C. Melt and extrude both polymers at a discharge rate of 1.4, then co-extrude into two layers using a manifold die and quench them on a cooling roll rotating at 50 ° C to obtain about 200μ unstretched sheet in the direction of 3.3 times at 90 ° C. After extending | stretching, it extended | stretched 3 times laterally at 100 degreeC, and heat-processed at 200 degreeC, and formed the film of 14.5 micro.

The film obtained at this time had a centerline average roughness Ra of the polyester layer A of 0.007 and a maximum surface roughness Rmax of 0.08 μ, and a centerline average roughness Ra of the polyester layer B of 0.028 μ, with a maximum surface. Roughness Rmax was 0.35 mu.

의 스테인레스 27고정봉(표면조도 0.3S)에 각도 θ(단위래디안)로 접할때 입구의 장력을 30g으로 고정할때 출구의 장력을 측정하여 다음식에서 산출하였다.The surface roughness was measured by Gosaka Institute's two-dimensional surface roughness measuring instrument SE-3H, and the friction coefficient was 23mm at 60RH%.

When the inlet tension was fixed at 30g when the stainless steel 27 fixed rod (surface roughness 0.3S) was contacted at an angle θ (unit radians), the tension of the outlet was measured and calculated by the following equation.

Coefficient of friction (μk)

The biaxially oriented film was produced by the same method, making adjustment of a polyester layer (A) constant, and changing the kind and size of inert fine particles of a polyester layer (B).

The obtained base film was coated with a ferromagnetic oxide γ-Fe 203 uniformly dispersed in a binder on the polyester layer (A) to a thickness of 4μ, coated and cut into 1/2 "widths to form a magnetic tape.

The resulting magnetic tape was run with a tape recorder while using a dropout counter to measure a drawout of 15 μsec or more and 20 db or less for the first 10 minutes to calculate the average value.

The S / N ratio was recorded at 50% of the back level signal at the optimum recording current, and the signal and noise ratio included in the video demodulation signal at the time of reproduction were compared with a commercially available VHS tape using 0 dB as a video noise meter.

TABLE 1

As shown in Table 1, the size of the inert fine particles added to the polyester layer (B) was 0.1-5 mu and the dropout and the electronic properties were good in the range of 0.01-0.3 wt%.

When the inert fine particles were 0.1μ or less or the dose was 0.1 wt% or less, the initial characteristics were relatively good, but the dropout increased rapidly during repeated driving. The properties and electronic properties were poor.

Example 2

A polyester layer (A) containing a polyester layer (A) containing 0.07% by weight of titanium dioxide having a diameter of 0.04μ and a polyester layer (B) containing 0.2% by weight of calcium carbonate having a diameter of 0.5μ, in the same manner as in Example 1 ) And a biaxially oriented film was produced in the same manner while varying the thickness of the polyester layer (B) and was measured in the same manner as in Example 1.

TABLE 2

As shown in Table 2, the thickness of the polyester layer (B) is 3 µm or less, the friction coefficient is low in the range of 2: 1 to 7: 1 or less, and the ratio of the polyester layer (A) and the polyester layer (B) is Dropout and electronic properties were good.

If the thickness or the thickness of the polyester layer (B) is too thick, the properties of the polyester layer (B) are transferred to the polyester layer (A) and the electronic properties are lowered. If the thickness is too thin, the influence of roughening is small and the friction coefficient is high. Dropout in repeated regeneration increased.

Claims (8)

Consists of at least two adjacent layers, both outer layers have a surface roughness in the form of a mountain and a valley, and the center line average roughness (Ra) value in the surface roughness of one outer polyester layer (A) is 0.001-0.01 μ The maximum surface roughness (Rmax) value is 0.1 μ or less, the center line average roughness (Ra) value is 0.01-0.05 μ in the surface roughness of the opposite type of polyester layer (B), and the maximum surface roughness A biaxially oriented multilayer polyester film characterized by having an asymmetric structure having a (Rmax) value of 0.5 mu or less. The biaxially oriented multilayer polyester film according to claim 1, wherein the resin of the polyester layer (A) contains inert particles having a diameter of 0.01-0.1 µ at a ratio of 0.01-0.1 wt%. The biaxially oriented multilayer polyester film of claim 2, wherein the inert particles are at least one titanium dioxide, silicon oxide, or synthetic calcium carbonate. The biaxially oriented multilayer polyester film according to claim 1, wherein the resin of the polyester layer (B) contains inert particles having a diameter of 0.1-5 탆 at a ratio of 0.01-0.5% by weight. The biaxially oriented multilayer poly according to claim 4, wherein the inert particles are at least one or more of metal oxide sulfides and hydrates such as titanium dioxide, silicon oxide, calcium carbonate, aluminum hydroxide, kaolin, mica, talc, barium sulfide and the like. Ester film. The biaxially oriented multilayer polyester film of Claim 1 whose total thickness is 5 micrometers or more and 20 micrometers or less. The biaxially oriented multilayer polyester film according to claim 1, wherein the ratio of the thickness of the polyester outer layer (A) and the polyester layer (B) is from 2: 1 to 7: 1 or from 1: 2 or more to 1: 7. . The thickness of a polyester layer (B) is 3 micrometers or less, The biaxially stretched multilayer polyester film of Claim 1 characterized by the above-mentioned.