JPH02107375A - Coating method - Google Patents

Abstract

PURPOSE:To form a paint film having excellent surface properties to a film by running a base film in opposed relation to a smooth plane so as to provide a predetermined gap from said plane and supplying paint to the gap from behind in the running direction. CONSTITUTION:This apparatus is constituted of a paint film thickness prescribing means (a) consisting of a block body 1 and a smooth flat plate 2, a running means (b) of a base film 7 consisting of the back roll 3 opposed to the smooth flat plate 2 through a predetermined gap W and guide rolls 4, 5, 6 and a paint supply means (c). The film 7 running in an A-direction by the means (b) is held in parallel to the smooth flat plate 2 under tension through the predetermined gap W and paint 8 is supplied to the gap part from behind in the running direction of the film 7. Whereupon, the paint 8 enters the gap W with the running of the film 7 and a paint film 9 having a film thickness W is formed to the running film 7 issued from the gap part in such a state that the surface of said film 9 is smoothed by the friction with the smooth flat plate 2. The gap W, that is, the film thickness W can be approximately altered by moving the means (a) or (b).

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a coating method, and in particular to a coating method for applying a magnetic paint or Panco-1 paint onto a base film, which is applied to the manufacture of so-called coated magnetic recording media. The present invention relates to a method of applying.

[Conventional technology]

Magnetic recording media used in the field of magnetic recording are broadly classified into coated type and thin coated type depending on the method of forming the magnetic layer. Among these, coated magnetic recording media are manufactured by uniformly applying a magnetic paint made by kneading ferromagnetic powder with a binder, a dispersant, a lubricant, and other additives onto a nonmagnetic base film. be done.

Conventionally, as methods for applying such magnetic paint, the so-called gravure coating method, in which the magnetic paint is transferred onto a base film using a gravure roll, and the offset coating method, in which an offset roll is used, have generally been adopted.

[Problem to be solved by the invention]

However, the current situation is that it is not always possible to obtain a magnetic recording medium with excellent surface properties by any of the above-mentioned methods.

First, in the gravure coating method, the base film is pressed between a cylindrical gravure roll with fine recesses (cells) and a smooth hack roll, and travels with the rotation of these IJ rolls. Therefore, immediately after the paint transfer step, the surface of the coating film has minute irregularities (so-called gravure pattern) reflecting the surface shape of the gravure 1 coat. This unevenness may even lead to deformation of the base film.

On the other hand, in the offset coating method, unlike the case of the gravure coating method, a concave indentation does not occur, but it is difficult to form a thick coating film.

This is because the coating film-1 is dragged depending on the surface tension and viscosity of the coating material as the roll rotates at high speed, and vertical streaks are likely to occur on the surface of the coating film.

Smoothing is usually performed to eliminate unnecessary patterns that occur in the coating film. For example, JP-A-54-
Publication No. 8646 discloses a technique for smoothing the surface of a coating film by bringing a specially shaped solid smoother into contact with the coating film provided on a continuously running web while it is still undried. Disclosed. However, at present, even with this technique, it is not possible to completely eliminate the gravure pattern and vertical stripes described in L.

Furthermore, in any of the above-mentioned systems, the base film has at least two 1. Since it runs while being sandwiched between the I-ru, there is a high probability that periodic defects will occur in the coating film depending on the machining and eccentricity of the I-ru.

If unnecessary patterns on the surface of the coating film as described above occur on the surface of the magnetic layer of a magnetic recording medium, the durability of the magnetic recording medium and the magnetic head due to the increase in the 1γly coefficient may decrease, and the recording and reproducing performance may deteriorate. Problems such as quality deterioration occur, which is extremely disadvantageous for high-density recording and high-speed recording.

Therefore, the present invention aims to solve the two problems and provide a coating method that can form a coating film with a thickness of 1 minute at high speed without generating unnecessary patterns on the coating surface. .

[Means to solve the problem]

The present invention is proposed to achieve the above object.

That is, in the coating method according to the present invention, a base film is run and closed in a state where a predetermined gap is formed with respect to a smooth plane, and the base film is coated from behind in the running direction of the base film into the gap. 1 is characterized in that a coating material is applied to the surface of the base film each time the base film is supplied.

Here, various methods can be considered to avoid running the heath fill J while facing the smooth surface with a predetermined gap. : Roll the base film around the base film and apply appropriate tension to keep it parallel to the above plane. At this time, set the distance between the roll and the plane as appropriate. A predetermined gap is set by choosing a radius longer than the radius of the 1-rule, and the size of the gap can be changed by moving either the plane or the radius.

The above-mentioned smooth plane may be constructed of a block body, a flat plate, a combination of a block body and a flat plate, a flat plate covered with a smooth film, or the like.

The material constituting the above-mentioned surface and its surface roughness are not particularly limited, but for example, S IJ S steel plate with a surface finish of -1, A polyenalene terephthalate (PET) film or the like is suitable.

Furthermore, the base film does not need to be wound directly around the roll; for example, a wide belt may be attached to the roll and then the roll may be run.

The method of supplying the paint is not particularly limited as long as the paint can be uniformly poured between the gear knobs from behind in the running direction of the base film, and an appropriate method may be selected depending on the viscosity, surface tension, etc. of the coating 11. All you have to do is choose. Therefore, it is also possible to provide a gap in the vertical direction Cζ and use the free fall of coating #:1 by gravity, or diagonally or water
It may also be possible to supply the coating $1 continuously during the gap.

[Effect]

According to the coating method of the present invention, the base film runs a certain distance while being sandwiched between the base film and a smooth plane with the paint on it, and then leaves the plane.

Therefore, it is possible to form a coating film with excellent surface properties without smoothing. In addition, since the plane and the base film maintain surface contact through the paint layer, there is less chance of damage to the base film or changes in the thickness of the paint film, etc., compared to applying with a line contact like using a doctor blade or cloth. few.

[Examples] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

Examples 1 to 3 In this example, a videotape was manufactured by using a SUS steel surface as a smooth flat surface and applying magnetic paint to the north of the PUT film.

The configuration of the apparatus used in this example is schematically shown in FIG. Broadly speaking, this device includes a coating film thickness regulating means, a paint supplying means, and a base film transporting means.

The film thickness regulating means consists of a block body (1) and a smooth flat plate (2) attached thereto, and the base film running means includes a bank roll (3) and a bank roll (3) facing the smooth flat plate (2) with a predetermined gap therebetween. Other guide rolls (
It consists of 4), (5), and (6).

The smooth flat plate (2) is manufactured, for example, from a SUS steel plate that has been given a level surface finish indicated by a triangular symbol in the JIS standard. In the configuration shown in Figure 1, the smooth flat plate (2)
protrudes a length l from the end face of the block body (1) toward the running direction of the base film (7) (indicated by arrow A in the figure), but it does not necessarily have to be like this. - The end faces of the block body (1) and the smooth flat plate (2) may be aligned on the same plane. However, as mentioned above, the smooth flat plate (2) is long! By protruding high, air can be smoothly supplied to the coating film (9) to be formed, and a magnetic recording medium with a better surface condition can be manufactured.

The base film (7) is wound around the hashic roll (3) and each of the guide rolls (4), (5), and (6), and travels in six directions indicated by arrows as these rolls rotate. Here, the -.- film (7) is caused by the tension acting between the hack roll (3) and the guide roll (5) to create a gap W.
It is held parallel to the above-mentioned smooth flat plate (2) via.

This gear W can be changed by moving either the film thickness regulating means or the base film traveling means, so consider the thickness of the base film (7), the thickness of the magnetic layer formed, the type of paint, etc.・! and set as appropriate.

In such a device, when paint 4 (8) is supplied to the gear knob part from behind in the running direction of the base film (7), the paint enters the gap W as it runs and is discharged from the gear knob part. On top of the base film is a 1L film whose surface has been smoothed by friction with the smooth flat plate (2).
A coating film (9) having a thickness of ff is formed.

Here, the smooth flat plate (2) is a SUS steel plate with a reher surface finish, and the base film is a 12 μm thick PE plate.
I actually made a tape using T-film. The composition of the magnetic paint is as follows.

Co deposition 7 FezOr (magnetic powder) 100 parts by weight Vinyl chloride-vinyl acetate copolymer (binder) [LJ, C
, C. Co., Ltd., product name: VAGII+ 10.5 parts by weight Polyurethane resin (binder) 1 Nippon Poly II') Retan Co., Ltd., product name: M-5033
110.5 parts by weight carbon blank (antistatic agent)
5 parts by weight lecithin (dispersant)
1 part by weight Methyl ethyl ketone (solvent) 150 parts by weight Methyl isobutyl ketone (solvent) 150 parts by weight The gap W of the magnetic paint was adjusted so that the thickness of the coating after drying was 51/Ill, and the PUT film was run. The speeds were 50m/sec and 100m/sec, respectively.

Coating was carried out at a speed of 200 m/sec. After that, magnetic field orientation treatment,
After drying, winding, and calendering, each sample tape was cut into 172-inch pieces.

Example 4 The above-mentioned smooth flat plate (2) was given a mirror finish and a ridged surface.
A sample tape was prepared in the same manner by pasting a μm-thick PET film and running the base film at a running speed of 100 m/sec.

Comparative Example: Using the conventional gravure coating method, the above-mentioned magnetic paint was coated at 12 μm at a base film running speed of 100 m/s.
It was applied onto a PET film having a thickness of m, and sample tapes were prepared in the same manner.

First, regarding the occurrence of a gravure pattern, 0 indicates that no gravure pattern is observed under the microscope, Δ indicates that it is slightly observed, and MU indicates that it is clearly observed.

Regarding the S/N ratio of the C signal, the Q is 40 dB or more,
Δ represents 37 dB or more and less than 40 d13, and Mu represents less than 37 dB.

Furthermore, regarding the S/N ratio of the Y signal, ◯ represents 50 dB or more, △ represents 47 dB or more and less than 50 dB, and MU represents less than 47 dB.

For each sample tape created in each of the above Examples and Comparative Examples, the occurrence of gravure patterns was observed using an optical microscope, and a 630 kHz chroma signal (C signal) and a 4 MHz luminance signal (Y signal) were measured. The S/N ratio during recording and reproduction was measured. These results are shown in Table 1.

In addition, in the table, the occurrence status of gravure patterns and S/N
Each ratio is represented by a symbol, the meaning of which is as follows.

Table 1 In conventional gravure coating, the occurrence of gravure patterns is unavoidable, and the S/N ratio is also low. On the other hand, in each of the embodiments to which the present invention is applied, no gravure pattern is generated, or even if it is generated, it is only slight.
The S/N ratio is also good. Tape speed during application is also 50rn
It is better to set the speed to 100 m/s or more rather than as slow as 100 m/s, which is also preferable from the viewpoint of improving productivity.

It goes without saying that the above-mentioned coating method can also be applied to forming a back coat layer using Banokko-1 paint.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing the main parts of a coating device used to carry out the coating method of the present invention. Block Body Smooth Flat Plate Bank Roll Guide Roll Base Film Paint Coating Film [Effects of the Invention] As is clear from the above explanation, by applying the present invention, a coating film with excellent surface properties can be formed at high speed. . If the coating method of the present invention is applied to the production of magnetic recording media such as video tapes, the surface of the magnetic layer can be formed smooth even when the base film is run at high speed, which allows the recording signal to be The S/N ratio during recording and reproduction also improves.

Claims (1)

[Claims] The base film is made to run while facing a smooth plane with a predetermined gap, and the paint is applied to the surface of the base film by supplying the paint to the gap from behind in the running direction of the base film. Application method.