JPS60180837A - Coated film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD OF THE INVENTION The present invention relates to coated films. Specifically, the present invention relates to a polyester film for magnetic recording media, and more particularly to a polyester film for vapor-deposited video.

[Prior art]

Vapor-deposited videotape, in which a magnetic substance is vapor-deposited on the surface of a polyester film, is capable of extremely high-density magnetic recording, but because the thickness of the magnetic layer is extremely thin, the surface morphology of the base film used remains unchanged. The surface morphology of the deposited thin film after deposition.

Therefore, if the surface roughness of the base film is rough, the electromagnetic conversion characteristics of the vapor-deposited video tape will be significantly deteriorated.

From the viewpoint of electromagnetic conversion characteristics, a base film consisting of a completely smooth mirror surface is preferable, but a vapor deposited film formed on such a base film.

Since the vapor-deposited surface remains mirror-like, it has very poor slipperiness, and unless a protective layer is applied to the vapor-deposited 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 in the actual use of vapor-deposited video tapes is the runnability of the vapor-deposited surface. In the case of conventional coated video tapes in which magnetic powder is mixed with an organic binder and applied to a base film, a lubricant can be added to the binder to improve the running properties of the magnetic surface. for videotape.

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 tape without this protective film layer,
There are drawbacks such as the inability to improve the runnability of the vapor-deposited surface, especially under harsh conditions when actually used, ie, under high temperature and high humidity conditions.

[Purpose of the invention]

An object of the present invention is to provide a base film capable of forming a deposited film with excellent smoothness, scratch resistance, and runnability not only in normal environments but also under high temperature and high humidity conditions.

[Structure of the invention]

The present invention has the following configuration to achieve the above object.

That is, a polyester film, a water-soluble polymer closely adhered to at least one side of the polyester film, and a thickness of 500A mainly composed of fine particles with a particle size of 60 to 500A.
With a discontinuous film of:

The film surface of the discontinuous part of the discontinuous film has a protrusion formed by the fine particles on the discontinuous film, and the film surface of the discontinuous part of the discontinuous film is It is characterized by a coating film in which the height of the fine particles closely adhered to is higher than the thickness of the discontinuous coating.

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. This is desirable. Also,
It is desirable that the surface of the polyester film is smooth, and specifically, the roughness of the film surface is 0.08+nm, the cutoff value of a stylus type surface roughness meter, and an Ra value of 0.0.
It is desirable that the thickness be 15μ or less, more preferably within the range of 0010 to 0002μ.

Note that the Ra value is determined by using an appropriate cutoff value from the cross-sectional curve obtained from a stylus type surface roughness meter.

Absolute value of the height and height of the roughness curve from the center line (measured so that the areas above and below the center line are equal) in the roughness curve excluding ridges is the arithmetic mean of (according to D engineering 1.476'8).

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.

Representative examples include poly-1,4-cyclohexylene dimethylene terephthalate, polyethylene-2,6-naphthalene dicarboxylate, and polyethylene-p-oxybenzoate.

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

For example, diol components such as diethylene glycol, propylene glycol, neopentyl glycol, polyethylene glycol, p-xylylene glycol, 1,4-cyclohexane dimetatool, adipic acid, sebacic acid, phthalic acid, isophthalic acid, 2,6-naphthalene Examples include dicarboxylic acids, dicarboxylic acid components such as 5-sodium sulfoisophthalic acid, trimellitic acid; polyfunctional dicarboxylic acid components such as pyromellitic acid, and p-oxyethoxybenzoic acid. In the case of copolymerization, the amount of components to be copolymerized is 20 molar or less.

Furthermore, the above-mentioned polyester is mixed with at least one of an alkali metal salt derivative of sulfonic acid that is non-reactive with the polyester, a polyalkylene glycol that is substantially insoluble in the polyester, etc., to an extent not exceeding 5% by weight. It's okay. Furthermore, when the film is stretched, it may contain internal particles consisting of polymerization residues that cause protrusions on the film surface or inert particles added from the outside. When the polymer is biaxially stretched, it is sufficient that the thickness is 30 μm or less and the haze per sheet is 5% or less.

The discontinuous film of the present invention is formed from a composition mainly consisting of a water-soluble polymer and fine particles, and preferably contains a silane coupling agent or a titanium coupling agent. Fine protrusions made of fine particles are formed on the discontinuous film.

Moreover, the thickness of the discontinuous film of the present invention is 500X or less, preferably 50 to 300X. When the thickness exceeds 500X, the electromagnetic characteristics of the deposited thin film decrease.

In particular, the S/N ratio deteriorates.

The water-soluble polymer of the present invention has a molecular weight of 10,000 to 200.
10,000, preferably 100,000 to 1,000,000.

When the molecular weight is less than 10,000, the film described below becomes soft, it becomes difficult to maintain the structure, and the durability deteriorates. If the molecular weight exceeds 2 million, the film becomes too hard, becomes brittle, and has poor durability. Examples of such water-soluble polymers include polyvinyl alcohol and tragacanth rubber.

Gum arabic, casein, gelatin, methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, water-soluble polyester ether copolymer, etc. can be used.

The water-soluble polymer of the present invention is not a single component, but includes a water-soluble polymer for forming a discontinuous film and a water-soluble polymer that serves as an easily adhesive component that makes it difficult for fine particles present in the film to fall off from the film. A multi-component system is desirable.

What are the fine particles of the discontinuous film forming component of the present invention?

The size is 30 to 5 degrees, preferably 50 to 4 degrees. Here, the size refers to the maximum particle size of fine particles, and if the size is less than 30X, the runnability of the vapor-deposited thin film formed by vapor-depositing the magnetic material on the discontinuous film will not improve. If the size exceeds 50.0×, the electromagnetic conversion characteristics of the magnetic surface will deteriorate. The shape of the fine particles may be any shape such as a bispherical shape, an ellipsoidal shape, a long sword shape, or a cubic shape. In addition, the nine particle types include inorganic compound particles, such as MgO, Zn
O.

MgC0,,0aOO3,0aSO4,Ba5O,,A
l2O3,5in2゜TlO2, Ca, Ba, Zn
, Mn, and other acid salts can be used. Multiple types of fine particles may be used.

Fine particles exist in the discontinuous film and on the film surface, and the number of particles is 10' to 1 (38 particles/nu
It is necessary that n2' is preferably 10 to 10 ke/lllIn2 te. Number of particles is 104/l1oI
Less than n2.

Alternatively, if the diameter is less than 30A, the runnability of the deposited thin film surface obtained by depositing a magnetic material on the discontinuous film will not improve.

The number of diameter 2 particles is determined by observation with an electron microscope.

When the number of particles exceeds 10' particles/mm2, the S/N ratio among the electromagnetic conversion characteristics of the magnetic surface deteriorates. This is still undesirable as fine particles tend to fall off easily.

The fine particles in close contact with the film surface of the discontinuous portion of the discontinuous film in the present invention are particles with a diameter of 50 to 10,000 A, preferably 100 to 5,000 p, and are It is desirable that the diameter is larger than the diameter of the fine particles on the surface, and the ratio thereof is 2 or more, preferably 5 or more.

The diameter refers to the maximum length of fine particles observed by observing the film of the present invention with an electron microscope. The shape of the fine particles is spherical, ellipsoidal, rectangular, cubic, etc. Regarding the height of the particles, it is desirable that 20% or more, preferably 50% or more of the total number of particles are higher than the discontinuous coating, preferably 20 to 500 A higher. The number of particles is 10
4 to 108 pieces/mm2. Preferably 106 to 108 pieces/
Preferably MQ2. Number of pieces is 104/InI
If it is less than n2, there is a tendency that the runnability of the vapor-deposited film surface formed by vapor-depositing a magnetic material on this surface does not improve. When the number exceeds 108 pieces/Inm2, the electromagnetic conversion characteristics of the magnetic surface, especially the S/N ratio deteriorates. These are fine particles made of sodium acrylate, polyvinyl methyl ether, fluorine resin, etc. Plural types of fine particles may be used. The height of the fine particles is higher than that of the discontinuous film.

Preferably 20-500A, more preferably 30-2
00A high is desirable. If the height of fine particles is low,
These fine particles do not contribute to improving the runnability of the vapor deposited film surface provided on the surface on which the discontinuous film is formed. When it exceeds 500 A, the electromagnetic conversion characteristics of the surface of the deposited film deteriorate. That is,
If the S/N ratio is low, dropout increases.

For the purpose of improving the surface properties of the discontinuous film and its scratch resistance, silicone or a fluorine compound, or both, may be included as a film structural component.

The silicone that can be used has a molecular weight of 60,000 to 300,000, and preferably has the following as a chain component:
OH,, 06H5, HR2: C! H,,06H5,
H or functional group (e.g., epoxy group, amino group, hydroxyl group) n+100 to 7000, R, R2, a silicone compound having an integer that satisfies the above molecular weight, epoxy, amino group, amino at the end group, hydroxyl group, and other functional end groups.

In the present invention, the silicone compound is not necessarily a homopolymer, but may be a copolymer, a copolymer, or a mixture of several types of homopolymers.

The molecular weight of silicone is preferably 60,000 to 300,000.

When the molecular weight is less than 30,000, the film becomes too soft and -
1: The structure becomes easily deformed. On the other hand, if it exceeds 600,000, the film becomes brittle.

Examples of fluorine-based compounds that can be used include fluorine-based surfactants and fluorine-containing hydrocarbon compounds, but those with a fluorine content of 10 to 60 inches, preferably 20 to 50 inches, are desirable. . If the fluorine content is low,
The effect of slipperiness is no longer visible.

In addition, in order to strengthen the bond between the water-soluble polymer, silicone, or fluorine compound, or both, to strengthen the adhesive force between the film and the polyester film, and to strengthen the adhesive force between the particles present in the discontinuous part and the polyester film. It is desirable to add a silane coupling agent to the particles present in the discontinuities.

As a silane coupling agent, it is an organosilicon precursor that has two or more different reactive groups in its molecule. One of the two reactive groups is a methoxy group, ethoxy group, silanol group, etc., and the other Reactive groups include vinyl group, epoxy group,
Examples include methacrylic group, amino group, and mercapto group.

The reactive group is selected to be one that bonds with the water-soluble polymer side chain, terminal group, and polyester, and as a silane coupling agent, vinyltrichlorosilane, vinyltrioxysilane,
Vinyltris(β-methoxyethoxy)silane, γ-glycidoxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxy/silane, N-β(aminoethyl)γ-aminopropylmethyldimethoxysolane,
γ-chloropropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, etc. can be used.

Water-soluble polymer as discontinuous film component [A] Silicone or fluorine compound or mixture thereof [B]
, the silane coupling agent [C], the fine particles [D], and the fine particles [E] present in the discontinuous parts of the discontinuous film are used in the following proportions: [A): [B): (Owl: (D)
'1:[E]=20:D~20:0~20:1~40:
1-40. (preferably 20:0 to 20:1 to 20:1
-30:1-10) f, iru. [B] May be used for the purpose of improving helical properties and scratch resistance.

[C] is preferably used because it is in the bonding direction between various components. If [B] exceeds the upper limit, the adhesion strength of the deposited film will be poor. If [C] exceeds the upper limit, the discontinuous film structure will become too hard and the film will be brittle and undesirable.

When [C] is used, [D], l[) becomes a discontinuous film,
It is firmly attached to the film surface.

The fine particles [D) are present on the surface of the discontinuous film at a ratio of 104 to 1011 particles/mm2.

When [D] is less than the above-mentioned lower limit, its presence becomes sparse and the runnability of the vapor deposition surface deteriorates. Exceeding the upper limit is not preferable because the fine particles tend to fall off from the film and the electromagnetic characteristics deteriorate.

The fine particles []IC) are mainly adhered to the film surface of the discontinuous part of the discontinuous film, but when [E] is below the above lower limit, the number of adhesion decreases, and the particles are formed on the discontinuous film. It no longer contributes to improving the runnability of the deposited film surface. If the upper limit is exceeded, fine particles will be more likely to fall off the film surface. Further, the electromagnetic conversion characteristics are also deteriorated, which is not preferable.

The coated film of the present invention will be explained below based on nine drawings.

Figure 1 shows a discontinuous film that partially covers the surface of a polyester film, a state in which microscopic protrusions are present on the discontinuous film due to the fine particles existing therein, and a film at the discontinuous part of the film. FIG. 3 is a plan view showing fine particles in close contact with a surface. This state can be seen by observing it with an electron microscope at a magnification of 10,000 times or more.

FIG. 2 is a schematic cross-sectional view of the film of FIG. 1 with a discontinuous coating and fine particles adhered thereto. This shows a state in which the height of the fine particles is higher than the height of the discontinuous film. In FIGS. 1 and 2, 1 is a polyester film, 2 is a discontinuous film, 5 is a fine particle in the discontinuous film, and 4 is a fine particle existing in a discontinuous part of the discontinuous film.

The height (height and thickness) of the discontinuous film of the present invention is shown by h in Figure 3, and the measurement of the height, that is, the height, is performed using a stylus type surface roughness meter, and the cutoff value is 0. Using .08mm,
In the surface roughness curve when measuring 9 surface film-formed surfaces under the condition of vertical magnification of 500,000 times.

The peak portion due to fine particles existing in the discontinuous portion was excluded. This value is a measurement of the average height interval between peaks and valleys. The height of the fine particles is hP in Figure 6.

hP2. It is indicated by hP3, and h is a value measured by measuring the difference between a peak and a valley that are largely deviated in the height direction. Note that FIG. 6 schematically shows the actually measured curve. Roughness due to fine particles present in the discontinuous film is difficult to observe.

The height of the discontinuous coating of the present invention is 500X or less, preferably 50 to 600X. If the height exceeds 500 mm, the electromagnetic characteristics of the videotape with the vapor-deposited film formed on its surface, especially the S/N ratio, will deteriorate.

The tape characteristics were evaluated by repeatedly recording and playing back using a commercially available VH8 type VTR.

The tape running properties were evaluated by performing playback under two conditions: normal temperature and humidity, and high temperature and high humidity, and observing screen fluctuations due to disturbances in tape running.

The evaluation criteria are as follows.

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

×: The running is slow in some places, and the playback screen flickers.

The scratch resistance was evaluated by observing scratches on the tape thin film after running the tape 100 times under normal temperature and humidity conditions and high temperature and high humidity conditions.

The evaluation criteria are as follows.

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

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

×: Severe scratches occur on the tape thin film surface. Note that normal temperature and humidity are 25° C. and 60% RH.

The high temperature and high humidity conditions are 50° C. and 80% RH.

The S/N ratio was measured by recording a 50% white level signal at the optimum recording current for each tape and comparing it with the video demodulated signal during playback.

Dropouts were measured by recording a 6-step step wave signal on a magnetic recording tape at the optimum recording current, and measuring dropouts with a video head amplifier output attenuation of 18 dB and a duration of 20 μsec or more during playback using a dropout counter for 10 minutes. , the average per minute was taken. The s/N ratio dropout measurement was performed under normal temperature and normal humidity conditions.

When a discontinuous film containing the fine particles of the coating film of the present invention has protrusions resulting from the discontinuous film, and a vapor-deposited film is provided on the surface of the discontinuous portion of the discontinuous film on the side where the fine particles are closely adhered, the magnetic head, the guide etc. is 1. Even though the contact area with the surface of the vapor deposited film is extremely small, the distance between the two ferromagnetic thin film surface and the magnetic head is kept very narrow, so the running properties of the surface of the vapor deposited film are extremely good. However, the electromagnetic conversion characteristics are excellent.

Next, two methods for producing the film of the present invention will be explained. Aqueous inorganic fine particle water-soluble polymer solution,
More preferably, a coating solution containing a silane coupling agent is applied, dried, and then stretched in the right angle direction, or after stretched in the right angle direction, the film is further stretched again in the one direction and heat treated.

By using inorganic fine particles that have good affinity with water-soluble polymers, the fine particles can be made to exist in the discontinuous film, resulting in a discontinuous film in which the organic fine particles or organic fine particles are closely adhered to the discontinuous parts. A surface is formed. Note that the water-soluble polymer solution here is preferably a two-component system. - Use a component that has adhesive properties that can particularly easily hold inorganic fine particles.

More specifically, the polyester raw material described above is melt-extruded using a conventional film-forming machine, cooled, and then uniaxially stretched 3 to 5 times to form a longitudinally stretched film.

Thereafter, in a step before preheating and stretching, a coating solution containing a water-soluble polymer aqueous solution with a molecular weight of 10,000 to 2,000,000 containing fine inorganic compound particles, fine organic compound particles, or an organic compound emulsion, preferably a 7-run coupling agent, is applied. is coated on at least one side by various coating methods. A silicone compound, a fluorine compound, or a mixture thereof may be added to the coating liquid components.

The coating amount of this coating liquid is 3 to 1 in terms of solid content per surface.
000 mg/m2 is good. Next, this longitudinally stretched film coated with the coating solution is stretched in the transverse direction, but in order to form a film completely before the transverse stretching, it is necessary to completely evaporate the moisture in the coating solution on the film surface to dryness. this is.

5%/sec to 100% in the stenter preheating section of the biaxial stretching machine
Hot air temperature 100-150 to achieve a moisture drying rate of / sec.
This is done by preheating at ℃. 90-12 after preheating
Transverse stretching is carried out by 25 to 4 degrees 5 times at a stretching temperature of 0°C. Fine particles are included on the film surface by horizontal stretching after drying and complete film formation.

As a result, fine particles are formed in close contact with the discontinuous film having protrusions and the film surface of the discontinuous portion of the discontinuous film. This contributes to the quality of the film. Furthermore, this horizontally stretched film is heat treated at 180 to 220°C or t
i-Qts times, 180-220T after re-stretching:
When heat treated with , fine particles are present at discontinuities on the smooth surface of the polyester film. A biaxially stretched polyester film containing fine particles and having on at least one surface a discontinuous film having a height of 5ooX or less and provided with protrusions is obtained.

Although the above explanation was made regarding a single layer film.

In the production of a composite film by co-extrusion of a raw material and a slippery film raw material to which fine particles have been actively added, water-soluble polymers and fine particles are mainly formed on the surface of the smooth film layer. By closely adhering the discontinuous film provided with projections made of fine particles, and making the fine particles adhere to the discontinuous portions, the running performance of the vapor-deposited film formed on the surface on which the film is formed dramatically improves. to improve.

Furthermore, since the height of this discontinuous film is 5ooX or less, the electromagnetic conversion characteristics of the vapor-deposited tape are not impaired. Further, since the height of the fine particles formed in the discontinuous portions of the discontinuous coating is 500 times or less higher than the height of the discontinuous coating, dropouts do not increase.

The coated film of the present invention can be applied to various uses, but
Preferably, it is used as a base film for magnetic recording media, more preferably for forming a ferromagnetic metal thin film.

Next, two examples of manufacturing the coated film of the present invention and an example of applying the film to a magnetic tape will be described based on Examples. - Example 1 A substantially non-oriented, amorphous polyethylene terephthalate raw material containing as little internal particles as possible due to polymerization catalyst residue etc. was melt-extruded onto a rotating drum maintained at about 20° C. The film was stretched in the machine direction, and then the following aqueous emulsion was coated on both sides at a solid content concentration of 20 mg/m2 using a metering bar coater.

Methyl cellulose 0, 20 as an aqueous emulsion
wt%, ultrafine silica 0°15w with average particle size 2DOA
t%, and a polyacrylic acid ester emulsion (solid content concentration 40%) at a ratio of 0.10 wt% was prepared. The drying, preheating, and stretching temperatures were 115° C., and the moisture drying rate was 15 coefficients/second.

A discontinuous film with a height of 260A is formed on one side at a transverse stretching ratio of 64 times and a heat treatment temperature of 200°C, and in the discontinuous film, fine protrusions with a diameter of 20OA are formed and the height is 50H higher than the height of the discontinuous film. A thickness of 12 μm in which fine particles are closely adhered to the discontinuous portion of the discontinuous film at a ratio of 4 x 10′ pieces/a112.
Obtained polyethylene terephthalate film.

A dicobalt-nickel alloy thin film with a thickness of 1500^ was formed on the surface of this polyester film by vacuum deposition.

Subsequently, the film was cut into a predetermined width in the machine direction to obtain a magnetic tape. This characteristic is shown in Table 1.

Example 2 In the production of the base film of Example 1, 0% of the water-soluble polyester ether copolymer was added to the aqueous emulsion used.
．． 35 wt% and the silane coupling agent N-β(aminoethyl)γ-aminopropylmethyldimethoxysilane at a ratio of 0.05%. A polyethylene terephthalate film with a thickness of 12 μm was obtained which was closely adhered at a ratio of m2.

A magnetic tape was obtained in the same manner as in Example 1 using this base film. Table 1 shows the tape properties.

Example 6 Example 20 The polyacrylic acid ester emulsion in the aqueous emulsion used in the production of the base film was converted into a polyvinyl acetate emulsion (solid content 65%).
01 wt%. Otherwise, a discontinuous film containing fine particles and a height of 270H with protrusions formed therein was formed in the same manner as in Example 1, and the fine particles, which were 5ON higher than the height of the discontinuous film, were placed in the discontinuous portion at 3×106. ke/m
A polyethylene terephthalate film having a thickness of 12 μm was obtained which was adhered with an In2 ratio.

Using this base film, a vapor-deposited magnetic tape was obtained in the same manner as in Example 1. Table 1 shows the tape characteristics.

Indicated.

Comparative Example 1 In the production of the base film of Example 1, an aqueous solution with a methylcellulose aqueous solution concentration of 0.40% was used, and the other conditions were the same as in Example 1. A polyethylene terephthalate film having a thickness of 12 μm was obtained, in which a discontinuous film was formed on both sides, and fine particles lower than the height of the discontinuous film were closely adhered to the discontinuous portions of the discontinuous film at a rate of 4×10 6 particles/mm 2 .

A magnetic tape was obtained in the same manner as in Example 1 using this base film. Table 1 shows the tape properties.

Comparative Example 2 A discontinuous film with a height of 250X was formed on both sides in the base film production of Example 1 except that ultrafine silica was not used, and a 12 μm polyethylene terephthalate film with a discontinuous film was obtained. .

A magnetic tape was obtained in the same manner as in Example 1 using this base film. Table 1 shows the tape properties.

Comparative Example 6 In the production of the base film of Example 1, ultrafine silica with a particle size of 150 OA was used.

Otherwise, a discontinuous film with a height of 280A with protrusions of diameter 1500H formed on both sides was formed in the same manner, and fine particles 30X higher than the height of the discontinuous film had a surface that existed in the discontinuous part of the discontinuous film. A polyethylene terephthalate film having a thickness of 12 μm was obtained.

Comparative Example 4 The base film was produced in the same manner as in Example 10, except that the concentration of the methyl cellulose aqueous solution was 0.10% and the concentration of the polyacrylic acid ester emulsion was 1.5 wt%. A discontinuous film with a height of 50A is formed on both sides, and fine particles with a height of 650λ higher than the height of the discontinuous film are adhered to the discontinuous portion of the discontinuous film at a rate of 6 × 107 pieces/MQ2 to a thickness of 12μ. Obtained polyethylene terephthalate film.

A magnetic tape was obtained in the same manner as in Example 1 using this base film. Table 1 shows the tape properties.

Comparative Example 5 Example 10 Base film production without using polyacrylic acid ester emulsion.

In the same way, a discontinuous film with a height of 260A containing fine particles and protrusions formed thereon is formed on both sides, and the discontinuous film has a surface with no fine particles in close contact with the discontinuous portion, and has a thickness of 12 μm. Obtained polyethylene terephthalate film.

A magnetic tape was obtained in the same manner as in Example 1 using this base film. The tape properties are shown in Table 1.

As is clear from the characteristic results in Table 1, the coating film of the present invention has a discontinuous film containing fine particles, and a vapor-deposited film is formed on the discontinuous portion of the discontinuous film on the side to which the fine particles are adhered. Magnetic tape can be used at room temperature and humidity.

Even when used at high temperatures and high humidity, it has good running properties and scratch resistance, and is smooth and has excellent electromagnetic conversion characteristics.

[Brief explanation of the drawing]

FIG. 1 shows a coated film of the present invention, with a discontinuous coating partially covering the surface of a polyester film. FIG. 2 is a plan view schematically showing a state in which fine protrusions are present in the discontinuous film due to fine particles existing therein, and fine particles closely adhered to the film surface of the discontinuous portion of the film. FIG. 2 is a cross-sectional view schematically showing the cross section of FIG.
This shows the state in which the fine particles are in close contact with the discontinuous parts of the discontinuous film and the fine particles in and on the discontinuous film. The middle part of the figure is the film thickness. FIG. 3 is a stylus type surface roughness curve chart at a vertical magnification of 500,000 times for the discontinuous film surface formed according to the present invention. h is the height of the film, hA11 hP21 hA is the height of the fine particles present in the discontinuous portion of the discontinuous film. 1: Polyester film 2: Discontinuous film 3.4: Fine particle rod 1 Same 2 times 3 times

Claims (1)

[Claims] (1) A polyester film, a water-soluble polymer closely adhered to at least one side of the film, and a particle size of 30 to 500
The film consists of fine particles of H and is closely adhered to the surface of a 500 mm thick film. A coating film in which projections of fine particles are formed on the discontinuous film, and the height of the fine particles closely adhered to the film surface of the discontinuous portion of the discontinuous film is higher than the thickness of the discontinuous film.