JPS6116017A - Polyester film for magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the adhesiveness of a polyester film to a magnetic layer and to prevent the blocking thereof by providing a continuous film consisting essentially of specific water soluble polyester, silane coupling agent and pulverous inorg. particles to the surface of said film and forming specific projections to said film. CONSTITUTION:The continuous film consisting essentially of the water soluble polyester in which >=70mol% of the total dicarboxylic acid consists of arom. dicarboxylic acid and 7-30mol% consists of ester formable alkali metallic chloride comptd. of sulfonic acid and of which the glycolic component consists of ethylene glycol having (100:0)-(100:15) compsn. ratio in molar ratio and ethylene gycol, the silane coupling agent and the pulverous inort. particles is formed on at least one surface of the polyester film and the projections having average 0.005-5mum diameter are formed on the continuous film. The pulverous inorg. particles having abot 0.005-3mum diameter are preferable. The adhesiveness of said film to the magnetic layer is improved and the mutual blocking of the films is prevented by forming such continuous film. The film is particularly suitable for formation of a film deposited by evaporation and is used for not only a magnetic recording medium but photosensitive and other materials as well.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to polyester films for magnetic recording media.

[Prior art]

Linear polyester films, especially biaxially oriented polyethylene terephthalate films, have excellent mechanical properties, chemical resistance, and heat resistance. Due to its dimensional stability, etc., it is widely used as a magnetic recording material.

The magnetic layer of magnetic recording media can be divided into two types: one in which a magnetic metal dispersed in a resin binder is coated on the film, and the other in which only the magnetic metal is attached to the film by a method such as vapor deposition. It is used in products such as However, the adhesion between the magnetic layer and the polyester film is often a problem, and various methods have been investigated to improve the adhesion of the polyester film.

Conventionally, as a method for improving the adhesion of polyester films,
Physical treatments such as corona treatment, plasma treatment, and ultraviolet light treatment, as well as chemical treatments in which the film surface is treated with specific compounds, are known. However, 9 the adhesion of films treated with these methods may change over time, and the adhesion strength itself is not particularly great, so they are only auxiliary means, and the method of providing an undercoat layer on the polyester film is Nine different types of undercoat agents for polyester films have been proposed and are in practical use. Among these methods, a method using water-soluble polyester as an undercoating agent is superior in coatability to polyester films, adhesion to polyester films, adhesion to magnetic layers, etc. However, when the film is wound into a roll, blocking occurs easily between the polyester film and the undercoat layer, or between the undercoat layer and the other undercoat layer.

In order to make water-soluble polyester water-soluble, the amount of copolymerization and the amount of hydrophilic groups in the polyester resin are often increased, which lowers the softening point of the resin and increases its hygroscopicity, making the blocking phenomenon described above more likely to occur. It becomes easier.

On the other hand, in conventional vapor-deposited video tapes in which a magnetic metal is directly attached to the surface of a polyester film by vapor deposition, etc., the thickness of the magnetic layer is very thin, and the surface morphology of the base film used is very thin. Since the surface morphology is the same as that of a vacuum-deposited ferromagnetic metal thin film (hereinafter simply referred to as a deposited film), if the surface roughness of the polyester film is rough, the electromagnetic conversion characteristics of the deposited videotape will be significantly impaired. Considering this electromagnetic conversion characteristic, a base film with a completely smooth mirror surface is preferable, but the vapor deposited film formed on such a polyester film has extremely slippery properties because the vapor deposition surface maintains its mirror surface. At worst, unless a protective layer is applied to the evaporated surface.

A large number of scratches occur in the tape forming process after the vapor deposition process, making it completely impractical.

Furthermore, a serious problem when actually using vapor-deposited videotape is the runnability of the vapor-deposited surface. In the case of conventional coated video tapes, which are made by dispersing magnetic metal powder in a resin binder and coating it on a polyester film, it is possible to add a lubricant to the binder to improve the running properties of the magnetic surface. In the case of videotapes, the runnability of the deposited surface is generally disadvantageous unless a protective film layer is provided. Since it is difficult to uniformly provide a protective film layer on the vapor deposition surface, in the case of vapor deposition tapes without this protective film layer, it is necessary to improve the runnability of the vapor deposition surface, especially under harsh conditions when actually used. That is, there are drawbacks such as the inability to improve running performance under high temperature and high humidity conditions.

Furthermore, the adhesion between the polyester film and the deposited film has traditionally not been very strong, and when playing back still images where the magnetic head makes contact with the same spot many times, the deposited film is scraped, resulting in increased dropouts or even loss of the reproduced image. There are other problems.

[Purpose of the invention]

The object of the present invention is to eliminate such drawbacks and provide a polyester film for magnetic recording media which does not cause blocking during handling of the film and has improved adhesion to the magnetic layer.

[Structure of the invention]

The present invention has the following configuration to achieve the above object. That is, on at least one side of the polyester film, of the total dicarboxylic acid components, 70 or more moles are aromatic dicarboxylic acids, 7 to 30 moles are ester-forming alkali metal sulfonic acid salt compounds, and glycol components are contained in molar ratios. A continuous film is formed mainly consisting of a water-soluble polyester made of ethylene glycol and diethylene glycol in a composition ratio of ioo:o to 100:15, a silane coupling agent, and inorganic fine particles, and the continuous film has an average diameter of 0. D D It is characterized by a polyester film for magnetic recording media in which protrusions of 5 to 5 μm are formed.

The polyester film of the present invention is a polyester film formed by a well-known method.

Polyester is melted and extruded into sheets or cylinders,
A film formed by stretching this in at least one direction, and the mechanical properties of the film are either a normal balanced type, a type strengthened in the -axial direction, or a type strengthened in the biaxial direction. It is desirable that there be. still,
It is desirable that the surface of the polyester film be smooth, and specifically, the roughness of the film surface is such that the cutoff value of the stylus type surface roughness meter is 0.08 mm, and the Ra value is 0.015μ.
Hereinafter, it is more preferably within the range of 0.010 to 0.002μ.

Note that the Ra value is the absolute value of the height and height of the roughness curve obtained from a stylus surface roughness meter, which is obtained by making the areas of the upper and lower parts equal. (according to DIN 476B).

The polyester forming the film may be any polyester as long as it is mainly composed of linear polyester. For example, polyethylene terephthalate, polytetramethylene terephthalate.

Typical examples thereof include poly-1,4-cyclohexylene dimethylene terelatate, polyethylene-26-naphthalene dicarboxylate, and polyethylene-P-oxybenzoate.

The above-mentioned polyester may be a homopolyester or a copolyester. In the case of copolyester, as a component to be copolymerized.

For example, diethylene glycol-propylene glycol-obentyl glycol, polyethylene glycol, P
- Diol components such as xylylene glycol and 1,4-cyclohexane dimetatool, adipic acid, sepacic acid, phthalic acid, and isophthalic acid.

2. Dicarboxylic acid components such as 6-naphthalene dicarboxylic acid and 5-sodium sulfoisophthalic acid, polyfunctional dicarboxylic acid components such as trimellitic acid and pyromellitic acid, P
-oxyethoxybenzoic acid and the like. In the case of copolymerization, the mole ratio of the components to be copolymerized is 20 or less.

When the film is stretched, it may contain internal particles consisting of residual polymerization that cause protrusions on the film surface or inert particles added from the outside, and the content thereof is determined by When biaxially stretched.

It is sufficient that the thickness is 60 μm or less and the haze per sheet is 5% or less.

In the water-soluble polyester of the present invention, aromatic dicarboxylic acids having a molar ratio of 70 or more among all dicarboxylic acid components include terephthalic acid, isophthalic acid, phthalic acid, 2,5-dimethylterentalic acid, chilic dicarboxylic acids, It consists of biphenyldicarboxylic acid and their ester-forming derivatives, among which terephthalic acid is preferable in terms of wear resistance.

In addition, the 7 to 60 molar ester-forming sulfonic acid alkali metal salt compound consists of alkali metal salts such as sulfoterentalic acid, 5-sulfoiphthalic acid, 4-sulfoisophthalic acid, and ester-forming derivatives thereof. Among these, the sodium salt or potassium salt of 5-sulfoisophthalic acid is preferred. If the ester-forming aromatic sulfonic acid alkali metal salt compound is less than 7 moles, it is difficult to uniformly coat the polyester film, resulting in uneven thickness of the film, which is not preferable. talented 3
When the molar ratio exceeds 0, the blocking property increases.

Next, the glycol component consists of ethylene glycol and diethylene glycol in a molar ratio of ethylene glycol to diethylene glycol of 100:0 to 100:15 (preferably lop: 0 to 100:10), and the ratio of diethylene glycol is as above. If the range is exceeded, the blocking property increases.

This water-soluble polyester has a molecular weight of 1 x 10'~
1 x 10' is preferred because of its good adhesion and water solubility.

The water solubility of the water-soluble polyester used in the present invention is not strictly defined in a physical or chemical sense, and refers to a polyester that is mostly dissolved or finely dispersed in water.

In addition, the water-soluble polyester has a phosphorus content of 20 to 10010 p as the amount of phosphorus in the phosphorus compound relative to the polyester.
It may contain pm.

The silane coupling agent of the present invention is an organosilicon monomer having two or more different reactive groups in its molecule.
The reactive group - is a methoxy group, ethoxy group, silanol group, etc., and the other reactive group is a vinyl group, epoxy group, methacrylic group.

These include amine groups and mercapto groups. The reactive group is selected to be one that bonds with the water-soluble polyester side chain, terminal group, and polyester.As a silane coupling agent, vinyltrichlorosilane, vinyltri)toxysilane, 〈niltris(β-methoxyshetoxy)silane, γ-glycidoxy Propyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, N-β(aminoethyl)γ
-Aminopropylmethyldimethoxysilane, γ-chloropropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, etc. can be used.

The inorganic fine particles of the present invention are known inorganic compound particles, specifically MgO, ZnO, Mg CO, CaCO1°C.
a5O,, Ba5O,, AI, O,, Sin, , T
ie, Ca, Bta'.

These are fine particles made of acid salts such as Zn and Mn, and these fine particles may be of one type or may be a combination of several types.

The average diameter of the inorganic fine particles is preferably 0.005 to 0.0 μm,
0.005 to 1μ is more preferable. In addition, when the magnetic layer is limited to a vapor deposited film, 1. The diameter is preferably 0005 to 01□, particularly 0.01 to 0.05μ.

The continuous film of the present invention includes the above-mentioned water-soluble polyester,
It mainly consists of a silane coupling agent and inorganic fine particles, and the blending ratio is not particularly limited, but the water-soluble polyester is [A], the silane coupling agent is [B],
When the inorganic fine particles are [CB], the blending ratio when the magnetic layer is a coating layer is [A]:CB):(C)=100:0.1
-100:01-100 is preferable. If [B] is below the above-mentioned lower limit, the moisture resistance will not be improved and blocking will occur when the film is wound into a roll, or [:CB may fall off from the film]. If the upper limit is exceeded, the coating solution will gel, shortening the pot life, and the continuous film structure will become too hard, making the film brittle and significantly reducing its properties as an adhesive undercoat layer. [When CB falls below the lower limit, blocking occurs. Exceeding the upper limit is undesirable because fine particles fall off from the film more frequently, worsening dropouts and the like.

In addition, when the magnetic layer is a vapor-deposited film, the compounding ratio is (,A):[B
):(C:I=100:0.1~100:0.1~1
0 is preferred. [The electromagnetic conversion characteristics are improved when the upper limit of CB is within the above range.

In addition, silicone is a constituent component of the continuous film of the present invention.

By adding a lubricant such as various waxes as necessary and coating it on the surface opposite to the magnetic layer surface, a polyester film with easy running properties can be obtained.

The discontinuous film of the present invention has an average diameter of 0.005 to 5μ,
Preferably 0.005 to 2μ, more preferably 0005
-02μ, more preferably 0.015-0.08μ protrusions should be formed.

If the average diameter exceeds this range, adhesiveness and blocking properties cannot be satisfied.

Further, the number of protrusions and the height of the protrusions are not particularly limited, but the height should be within the following range depending on the magnetic layer to which it is applied.
-45μ, especially 0.01-15μ is preferred.

If the magnetic layer is a vapor-deposited film, the number of protrusions is 10 to 10.
/InID', especially 10 to 10 /mm' is preferable.

The height of the protrusion is 0.05 μm or less, especially 0.05 μm or less. OQ 5～00
ro μ is preferred. Note that the average diameter of the protrusions in this case is 0.
005-02μ is preferred.

When the number of protrusions is within the above range, the blocking property is =1
However, if the height of the protrusion is within the above range, the electromagnetic conversion characteristics will be further improved.

Next, a manufacturing method of the present invention will be explained. However, it is not limited to this. A water-soluble polyester film in which a silane coupling agent and fine inorganic compound particles are mixed and dispersed is applied to at least one side of a smooth polyester film that has been stretched in one direction using a conventional method, and after or while drying, it is stretched in a right angle direction. Stretching is performed, or after stretching in the perpendicular direction, the film is further stretched in the one direction and then heat treated. More specifically, the polyester raw material described above is used.

A longitudinally stretched film is melt-extruded using an ordinary film forming machine, cooled, and uniaxially stretched 3 to 5 times. Then, in a step before preheating and stretching, a silane coupling agent and fine inorganic compound particles are mixed and dispersed in an aqueous solution. An aqueous solution of polyester (molecular weight: 1x10 to 1x1O) is coated on at least one side by various coating methods.

The coating amount of this coating liquid is 20% solids per surface.
0 to 4000 mg/m', preferably 6
00-28D Om'g/m'. Next, the coated longitudinally stretched film is laterally stretched, and the moisture in the coating solution on the film surface must be dried to at least an extent that does not interfere with the laterally stretched film. This is done by preheating the stenter preheating section of the biaxial stretching machine at a hot air temperature of 80 to 130"C to achieve a moisture drying rate of 6 to 100%/sec, and then
Transversely stretch 25 to 4.5 times at a stretching temperature of ~120°C.

Furthermore, this transversely stretched film is heat-treated at 180 to 230°C or 11 to 18 times, and after re-stretching to 180 to 23
Heat treatment at 0'O yields a smooth Bolier-stretched polyester film of the invention.

On the continuous film made of water-soluble polyester formed on the surface of the polyester film thus obtained,
Known magnetic layer 9 For example, a magnetic recording medium can be obtained by providing a coating layer in which a ferromagnetic material made of iron, cobalt, nickel, or an alloy thereof is dispersed in a binder, or a vapor deposited film formed of the ferromagnetic material. can.

〔Effect of the invention〕

In the present invention, at least one side of the polyester film
Since a continuous film with a constant percentage was formed, the adhesion to the magnetic layer was good, and an excellent effect was obtained in that the films did not block each other.

The polyester film formed with the continuous film of the present invention is
Although it is suitable to provide a known magnetic layer 1, such as a coating layer or a vapor deposited film, it is most suitable to provide the latter vapor deposited film in 9% of the magnetic layer. Note that the polyester film on which the continuous film of the present invention is formed can be applied not only to magnetic recording media but also to various uses such as photosensitive materials, packaging materials, drafting materials, and electrophotographic materials.

[Measurement method and evaluation method of characteristics]

(1) Average diameter of protrusions The surface of the film of the present invention was observed using an electron microscope.

Observe the maximum length and maximum diameter of each protrusion, and divide the sum of the observed values by the number of observed protrusions to determine the average diameter of the protrusions.

(2) The height of the protrusion in Figure 1 was measured using a stylus type surface roughness meter, and the cutoff value was 008.
2 is a schematic diagram showing a surface roughness curve obtained when the surface film-forming surface was measured at a vertical magnification of 500,000 times.

The height of the protrusion is as shown in Fig. 1 < hp, , hp
,,hp,.

(3) Adhesion A magnetic layer was coated on the continuous film layer of the film of the present invention, and the peel strength was measured. Composition of paint for magnetic layer How Nitrocellulose 3C11, polyurethane 40 parts, salt pea vinyl acetate resin 30 parts, isocyanate reactant 8 parts, carbon black 15 parts, stearamide 5 parts, γ-re, 0.5
00 parts toluene.

It was dispersed in 900 parts of a solvent mixed with equal amounts of methyl ethyl ketone. After coating, it was dried at 80°C for 1 minute.
Thereafter, it was aged for 20 hours at 8D'a.

The magnetic layer was approximately 5μ thick. A Scotch tape having a width of 18 mm manufactured by Sumitomo 3M was placed on the surface of this magnetic layer to measure the degree of air bubbles.

(4) Blocking property The surface of the polyester film of the present invention on which a continuous film was formed and the surface of the film on which a continuous film was not formed were overlapped.

Temperature 40°C2 Humidity 80%RH, Load 100g 7c
m" for 20 hours.Evaluation is by visually observing the overlapping of the above to determine how much of the total area of the film the blocking area is. If there is no blocking at all, 09 indicates partial blocking. Case: △, 5
A case where a portion of 0 or more blocks is blocking is marked as ×.

(5) Tape characteristics Recorded using a commercially available VHS VTR.

The playback was repeated and evaluated.

(a) Tape running properties The tape was played under two conditions: normal temperature and humidity, and high temperature and high humidity, and the screen fluctuations due to disturbances in tape running were observed.

The evaluation criteria are as follows.

○: The vehicle runs smoothly and there is no fluctuation in the playback screen.

×: The running becomes slow in some places, and the playback screen fluctuates.

(b) Resistance to scratches (adhesion) This was determined by observing scratches on the thin film of the tape after running it 100 times under normal humidity and high temperature and high humidity conditions. The evaluation criteria are as follows.

◎: Almost no scratches are observed on the thin film surface of the tape.

○: A few very weak scratches are observed on the thin film surface of the tape.

x: 9 severe scratches were generated on the tape thin film surface.

Note that normal temperature and normal humidity is 25° C. and 60° RH, and high temperature and high humidity is 4D'0.80% RH condition.

4%) S/N ratio 50% A white level signal was recorded at the optimum recording current for each tape, and the signal-to-noise ratio contained in the video demodulated signal during playback was measured using a video noise meter using a commercially available VH5 standard tape. 8) A three-step wave signal was recorded on a dropout magnetic recording tape at the optimum recording current, and the attenuation of the video head amplifier output during playback was 18 d.
B. Dropout with a duration of 20 μSea or more was measured using a dropout counter for 10 minutes, and the average per minute was taken. The S/N ratio and dropout measurements were performed under normal temperature and normal humidity conditions.

(Example〕 The present invention will be explained based on examples. however.

It is not limited to this.

Example 1 Polyethylene terephthalate with an intrinsic viscosity of 0.65 was
Melt extrusion onto a rotating drum maintained at 0'a followed by 34x stretching in the machine direction.

Thereafter, the following aqueous emulsion was coated on one side using a metering bar coater at a solid content concentration of 600 mg/m'.

As an aqueous solution emulsion, water-soluble polyester (polymer composition TPA 75 mol%/5-Na sulfo IPA
25 mol%, /EG 85 mol%/DE015 molti2 molecular weight 3000) 1.5 wt%, silane coupling agent N-β(aminoethyl)γ-aminopropylmethyldimethoxysilane 0.075+vt%, Sin.

A product containing 0.7 wt of particles (Aerosil≠300) was prepared. The drying/preheating and stretching temperature was 115°A, and the moisture drying rate was 15%/sec.

A polyethylene terephthalate film A having a thickness of 12μ and having a continuous film layer made of water-soluble polyester on one side was obtained by forming a film at a transverse stretching ratio of 34 times and a heat treatment temperature of 220"0.

The properties of this film A are shown in Table 1. Example 2 A polyethylene terephthalate film B having a thickness of 12 μm was used in the same manner as in Example 1 except that a polyethylene terephthalate film B was used.

The properties of this film B are shown in Table 1.

Example 6 A polyethylene terephthalate film with a thickness of 12 μm was produced in the same manner as in Example 1, except that the silane coupling agent was replaced with γ-glycidoxypropyltrimethoxysilane 1115 wt% in the production of film A of Example 1. C
I got it.

The properties of this film C are shown in Table 1.

Example 4 In the production of film A in Example 1, the polymerization composition of the water-soluble polyester was changed to TPA 90 mol 15-N a sulfo IPA 10 mol % // E 097 mol % / DEG 3 mol ratio 2 molecular weight 3000, and the aqueous solution concentration was 1.5 w.
The thickness was 12% in the same manner as in Example 1 except that t%
A μ polyethylene terephthalate film D was obtained.

The properties of this film D are shown in Table 1.

Example 5 In the production of film A of Example 1, kaolin (union carbide, ASPI 70) 0 was used instead of Sin.
．． A polyethylene terephthalate film E having a thickness of 12 μm was obtained in the same manner as in Example 1 except that the amount was changed to 5 wt%.

The properties of this film E are shown in Table 1.

Comparative Example 1 Example 1 except that no silane coupling agent, Sin, or particles were added in the production of film A of Example 1.
A polyethylene terephthalate film Fli having a thickness of 12 μm was prepared in the same manner as above.

The properties of this film F are shown in Table 1.

Comparative Example 2 A polyethylene terephthalate film G having a thickness of 12 μm was obtained in the same manner as in Example 1 except that 5102 particles were not added in the production of film A of Example 1.

The properties of this film G are shown in Table 1.

Comparative Example 3 A film with a thickness of 12
A polyethylene terephthalate film H of μ was obtained.

The properties of this film H are shown in Table 1.

As is clear from the characteristic results in Table 1, it can be seen that the film formed with the continuous film of the present invention has good adhesion and blocking properties.

Example 6 No ethylene terephthalate was mixed with ethylene terephthalate to minimize internal particles as much as possible due to the residual polymerization catalyst with an intrinsic viscosity of 065.
It was melt extruded onto a rotating drum maintained at 0°C, then stretched 34 times in the machine direction, and then the following aqueous emulsion was prepared using a metering bar coater to a solid content concentration of 600 mg/m'. It was coated on one side.

As an aqueous solution emulsion, the bipolymerization composition is TPA 75 mol% 15-Na sufu 1/Whey PA 25 mol%/
・p 1.5 wt% water-soluble polyester consisting of 85 mol% EG/15 mol% MEG, silica/coupling agent N-
A composition containing 0.075 wt% of β(aminoethyl)γ-aminopropylmethyldimethoxysilane and 0.15 wt% of ultrafine Sin having an average particle size of 200 Å was prepared. The drying, preheating, and stretching temperatures were 115°C, and the moisture drying rate was 15%/sec.

A 12μ thick polyethylene film formed at a transverse stretching ratio of 64 times and a heat treatment temperature of 220°0, on which a continuous film with a height of 190A and average diameter of 280A at a ratio of 5 x 10 protrusions/IIIrD2 was formed on one side. Obtained terephthalate film. Table 2 shows the blocking properties of this film.

A cobalt-nickel alloy thin film with a thickness of 150 OA was formed on the surface of this film by vacuum deposition, and then polyurethane, nitrocellulose, CaC01, and stearamide were formed on the surface opposite to the coated surface of the present invention. A back coat layer was provided. Subsequently, the film was cut into a predetermined width in the machine direction to obtain a magnetic tape. This characteristic is shown in Table 2.

Example 7 In the production of the film of Example B, the same procedure as Example 6 was carried out except that the ultrafine silica in the aqueous solution used was replaced with ultrafine CaC0 with an average particle size of 210A. 5 x 10 protrusions with an average diameter of 29OA at 200A/
Thickness 1 of continuous film formed at a ratio of 2'
A 2μ polyethylene terephthalate film J was obtained.

Table 2 shows the blocking properties of this film J.

Using this film J, a vapor-deposited magnetic tape was obtained in the same manner as in Example 6. The tape properties are shown in Table 2.

Example 8 In the production of the film of Example B, the film was produced in the same manner as in Example 6, except that the silane coupling agent was replaced with 0.15 wt of γ-glycidoxypropyl trimethoxysilane, with a height of 190 A and an average diameter of 280 A. A polyethylene terephthalate film K having a thickness of 12 μm was formed with a continuous film having protrusions of 5' x 10 protrusions/mm. The blocking properties of this film are shown in Table 2.

Using this film K, a vapor-deposited magnetic tape was obtained in the same manner as in Example 6. The tape properties are shown in Table 2.

Example 9 In the production of the film of Example B, the polymerization composition of the water-soluble polyester was changed to TPA 90 mol% 15-Na sulfo IPAIO mol% //E G 97 mol%/DE
Protrusions with a height of 190 A and an average diameter of 280 A were present at a rate of 5 x 10 pieces/mm' in the same manner as in Example 6, except that an aqueous solution with a concentration of 1 and 5 wt% was used instead of a molar ratio of 0.03 molar. A polyethylene terephthalate film L having a thickness of 12 μm and having a continuous film formed thereon was obtained. The blocking properties of this film L are shown in Table 2.

Using this film L, a vapor-deposited magnetic tape was obtained in the same manner as in Example 6. Table 2 shows the properties of the tape.

Comparative Example 4 Polyethylene terephthalate with a thickness of 12μ was formed in the same manner as in Example 6, except that the silane coupling agent, Sin, and particles were not added in the production of the film of Example B, in which a continuous film free of fine particles was formed. Film M
I got it. As shown in the table, the blocking properties of this film M were extremely poor and could not be passed through the next vapor deposition step.

Comparative Example 5 In the production of Film I of Example B, a polyethylene terephthalate film 11 with a thickness of 12 μm on which a continuous film free of fine particles was formed was prepared in the same manner as in Example 6, except for applying sin and particles. It's a good deal.

The blocking properties of this film H were as shown in Table 2. Although blocking was observed in some parts, using this film N, an ICL-C71・ro')i;c vapor-deposited magnetic tape was obtained in the same manner as in Example 6. . Table 2 shows the properties of the tape.

Comparative Example 6 Ultra-fine particles used in the production of the film of Example B S10. In the same manner as in Example 6, except that the average particle size of
x 12 μ thick polyethylene terephthalate film O with a continuous film formed at a rate of 10 pieces/work 2
I got it. Table 2 shows the blocking properties of this film O.

Using this film O, a vapor-deposited magnetic tape was obtained in the same manner as in Example 6. The tape properties are shown in Table 2.8 As is clear from the characteristic results in Table 2, the magnetic tape of the present invention has a vapor deposited film formed on the continuous film surface of a polyester film on which a continuous film has been formed.

Even when used at normal temperature and humidity, as well as at high temperature and high humidity,
It has good scratch resistance, smooth scratches, and excellent electromagnetic characteristics.

Table “1”

[Brief explanation of drawings]

FIG. 1 is a diagram schematically showing a surface roughness curve of a surface on which a continuous film of the present invention is formed, as measured by a stylus type surface roughness meter. h・1~hD, : Protrusion patent applicant Toshi Co., Ltd. Figure 1

Claims (1)

[Claims] (1) On at least one side of the polyester film, of the total dicarboxylic acid components, 70 mol% or more is an aromatic dicarboxylic acid, 7 to 30 mol% is an ester-forming sulfonic acid alkali metal salt compound, and the glycol component is in a molar ratio A continuous film is formed mainly consisting of a water-soluble polyester made of ethylene glycol and diethylene glycol with a composition ratio of 100:0 to 100:15, a silane coupling agent, and inorganic fine particles, and the continuous film has an average Diameter 0.
A polyester film for magnetic recording media on which protrusions of 005 to 5μ are formed.