JP2002066425A - Coating method and apparatus using rod - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the generation of streaking in a coating film by making it difficult to trap foreign matter on the surface of a flat coating rod when the coating film with a desired thickness is formed on a web using the coating rod. SOLUTION: The coating film A is formed on the web 12 using the flat coating rod 28. In this case, the coating film A is formed so as to satisfy Rmax<=h/3 in the relation between the thickness h (μm) of the coating film A and the maximum projection height Rmax of the surface roughness of the surface C of the coating rod.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for coating a rod, and more particularly to a method for coating a coating liquid as a medium for recording various images or data such as magnetic tape, photographic film, photographic paper, etc. The present invention relates to a rod coating method and an apparatus for forming a coating film by coating a flexible belt-shaped support (hereinafter referred to as “web”) using a rod.

[0002]

2. Description of the Related Art Methods for obtaining a coating film having a desired thickness on a web include a rod coating method (also referred to as a bar coating method), a reverse roll coating method, a gravure roll coating method, and an extrusion coating method. Among them, the rod coating method is widely used because the equipment is simple and thin layer coating is possible.

The rod coating methods are roughly classified into the following two types. One is a method in which a continuously running web is brought into contact with a coating rod to transfer and apply a coating solution onto the web and a desired coating amount. This is an integrated application / measurement system that performs measurement together. Another method is to apply an excess coating solution to a web with a pre-coating device such as an extrusion coating device, contact a coating rod with the coating solution, and scrape off the excess of the coating solution. Application that measures the amount of application
This is a separate measurement type.

In any case, a wire type in which a wire is wound on the rod surface, a grooved type in which a groove is formed in the rod surface, or a flat type in which the rod surface is flat without forming a wire or groove on the rod surface A coating film having a desired thickness is formed on the web surface by using any one of the three types of coating rods. Comparing these three types of coating rods, wire type or grooved type coating rods, in which the thickness of the coating film can be determined by the thickness of the wire rod and the depth of the engraved groove, are generally used. However, there is a problem that the abrasion resistance is inferior in structure. On the other hand, flat coating rods are excellent in abrasion resistance because they can be made of, for example, a very hard metal that is very hard and there is a liquid film of the coating liquid between the rod surface and the web. ing.

[0005]

However, since the distance between the rod surface and the web is shorter in the flat type coating rod than in the wire type or grooved type coating rod, foreign matter is not generated. A defect that the trapped foreign matter causes a streak failure in the coating film easily occurs on the surface.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and has been described in connection with forming a coating film having a desired thickness on a web using a flat coating rod which is advantageous in abrasion resistance. Therefore, an object of the present invention is to provide a rod coating method and apparatus which can suppress occurrence of a streak failure in a coating film because the rod can be hardly trapped on the rod surface.

[0007]

In order to achieve the above-mentioned object, the present invention provides a coating rod for simultaneously performing transfer coating of a coating solution and measurement of a coating amount on a continuously running flexible belt-like support.
Or a coating rod for measuring the amount of application by scraping off the excess amount of the coating solution of the flexible belt-like support to which the coating solution has been excessively applied in advance by a pre-coating device, wherein the coating rod is a flat coating rod In the rod coating method of forming a coating film on the flexible belt-like support using the method, the thickness of the coating film is h (μm), and the maximum projection height of the surface roughness of the rod surface of the coating rod is _Is R _max (μm),
The relationship between h and _Rmax satisfies _Rmax ≦ h / 3.

Further, in order to achieve the above object, the present invention provides a coating rod or a pre-coating apparatus for simultaneously transferring a coating solution to a continuously running flexible belt-like support and measuring a coating amount. A coating rod for measuring the amount of application by scraping off the excess amount of the coating solution of the flexible belt-shaped support to which the coating solution has been excessively applied in advance, and using a flat-type coating rod to measure the amount of coating. In a rod coating apparatus for forming a coating film on a flexible belt-like support, the rod surface of the coating rod has a thickness h (μm) of the coating film, and a maximum projection height of the surface roughness of the rod surface. When the surface roughness is R _max (μm), the surface smoothing process is performed so as to satisfy R _max ≦ h / 3.

According to the present invention, in a rod coating method for forming a coating film on a flexible belt-like support using a flat coating rod, the thickness of the coating film is defined as h (μm), The maximum protrusion height of the surface roughness of the rod surface of the rod is R
_{When max} (μm), the relationship between the h and the R _max satisfies R _max ≦ h / 3, so that it is possible to make it difficult for foreign matter to be trapped on the rod surface.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the rod coating method and apparatus according to the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is an overall structural view of a coating apparatus 10 according to the present invention, in which a coating liquid excessively applied to a web by a precoating apparatus is measured by scraping off the coating liquid with a coating rod.
This is the case of a rod application device of a separate measuring type.

The rod coating apparatus 10 mainly includes an extrusion type precoating apparatus 16 for applying the coating liquid 14 on the web 12 in excess of a desired amount, and a coating apparatus 14 for coating the coating liquid 14 on the web 12 in excess. It is composed of a coating rod device 18 for scraping the excess, and a plurality of guide rollers 20 provided along the web transport path.

Extrusion type precoating apparatus 1
Reference numeral 6 denotes a head tip surface of the coating liquid 14 fed into the pocket 22 from the outlet 24A of the slot 24 communicating with the pocket 22 to the web 12 mounted on the guide roller 20 and running at a constant speed in the direction of the arrow. Discharge is continuously performed while pressing 26. Thereby, the coating rod device 18
Immediately before, an excessive coating liquid is applied to the lower surface of the web 12. The precoating device 16 is not limited to the extrusion type, and any coating device that applies a coating solution to the web 12 can be used.

The coating rod device 18 is constructed by supporting a flat coating rod 28 disposed in parallel to the width direction of the web 12 continuously running in the running direction on a rod support member 30, and a guide. The roller 12 brings the web 12 into contact with the coating rod 28 at a predetermined wrap angle. As a result, the excess amount of the coating solution 14 excessively applied to the web 12 by the precoating device 16 is scraped off by the coating rod 28 and measured to a desired amount of the coating solution. Is formed. In this case, the coating rod 28 is connected to a rotation drive source (not shown) and rotates at a low speed in a direction opposite to the running direction of the web 12. Alternatively, the web 12 may be rotated in the same direction as the traveling direction of the web 12 by contacting the web 12, and a configuration in which the web 12 is not rotated may be used.

The coating rod 28 is, as shown in FIG.
For example, SUS rod core material 28A of 1 mm to 50 mm
Hard chrome plating 28B on the cylindrical outer peripheral surface of
Vickers hardness (Hv) of 000 or more.

As described in the prior art, when the flat type coating rod 28 is used, the web 1
Since the two surfaces and the rod surface 28C of the coating rod 28 are close to each other, there is a drawback that foreign matter is easily trapped on the rod surface 28C. It has been found that the relationship between the thickness of the applied coating film A and the surface roughness of the rod surface 28C is deeply related to the easiness of trapping foreign matter. This is because even though the rod surface 28C is a flat coating rod 28 having a flat surface, the rod surface 28C
This is because if the height of a large number of projections constituting the surface roughness is too high relative to the thickness of the coating film A to be formed, foreign substances are likely to be caught on the projections.
In particular, it has been found that the degree of the maximum protrusion height of the large number of protrusions with respect to the thickness of the coating film A greatly affects the ease with which foreign matter is caught. That is, it has been found that when the maximum protrusion height of the surface roughness of the rod surface 28C is 1/3 or less of the thickness of the formed coating film A, foreign substances are less likely to be caught on the protrusions.

The present invention has been made on the basis of this finding, and the rod surface 28 of the flat coating rod 28 has been developed.
C has been subjected to a smoothening treatment so as to satisfy the following expression (1).

[0018]

_Rmax ≦ h / 3 (1) where _{Rmax is} the maximum projection height of the surface roughness of the rod surface (μm) h: The thickness of the formed coating film A (μm) The thickness of the applied coating film A refers to the thickness after the excess of the application liquid 14 is scraped off by the coating rod 28.
That is, it is the thickness (μm) of the coating film A after the measurement. The smoothing of the rod surface 28C can be achieved by polishing the rod surface 28C with a polishing device or by mirror-polishing with a polishing device.

Therefore, to satisfy the above equation (1),
The thickness h of the formed coating film A, by adjusting the maximum protrusion height R _max of the surface roughness of the rod surface 28C, the coating liquid 14
Is scraped off, so that even when the flat type coating rod 28 is used, foreign substances are less likely to be trapped on the rod surface 28C. Thereby, it is possible to suppress the occurrence of the streak failure in the formed coating film A. In this case, the thickness of the formed coating film A is preferably 15 μm or less. This is because the allowable value of the maximum projection height _Rmax (when _Rmax = h / 3) that satisfies the above equation (1) increases as the thickness h of the coating film A increases. This is because, when the thickness of the coating film A exceeds 15 μm, the frequency of foreign matter being caught on the projections is significantly increased.

FIG. 3 is an overall configuration diagram of another embodiment of the rod coating device 40 of the present invention, which is a rod coating device provided with a coating rod 42 of an integrated coating and measuring type.

As shown in FIG. 3, a columnar coating rod 42 is arranged in the width direction of the web 12 in contact with the running web 12. The coating rod 42 is rotatable in the direction in which the web 12 runs, and is supported on a rod support member 44 so as not to hinder rotation.
The coating liquid 14 supplied to the coating liquid supply path 48 formed by the rod support member 44 and the weir member 46 forms a liquid pool 50 at a contact portion between the web 12 and the coating rod 42, The coating liquid 14 is transfer-coated on the web 12 by the coating rod 42 rotating through the liquid pool 50.

This coating / measuring integrated coating rod 42
Also, in the case of the rod coating device 40 provided with the above, the rod surface of the flat type coating rod 42 is subjected to a smoothening treatment so as to satisfy the above (1).

Accordingly, even in the case of the rod coating apparatus 40 including the coating rod 42 of the coating and measuring type, it is difficult for foreign matter to be trapped on the rod surface. Thereby, it is possible to suppress the occurrence of a streak failure in the formed coating film. In this case, the thickness of the formed coating film is preferably 15 μm or less, as in the case of the separate coating / measuring type.

As the web 12 to be used, generally,
Polyethylene terephthalate (P) having a width of 0.3 to 1 m, a length of 45 to 10000 m and a thickness of 2 to 200 μm
ET), plastic films such as polyethylene-2,6-naphthalate, cellulose diacetate, cellulose triacetate, cellulose acetate propionate, polyvinyl chloride, polyvinylidene chloride, polycarbonate, polyimide, polyamide, paper, polyethylene,
A flexible layer made of paper or the like coated or laminated with an α-polyolefin having 2 to 10 carbon atoms such as a polypropylene or ethylene butene copolymer, or a processed layer was formed on the surface of the flexible layer using the strip as a base material. It includes a band-like material, a metal foil such as an aluminum foil, and the like.

The coating solution 14 to be used is not limited to a non-Newtonian fluid such as a coating solution for a magnetic tape, but may be a Newtonian fluid which uses a relatively low-viscosity gelatin solution of a photographic photosensitive layer as a binder. Good.

[0026]

EXAMPLE A practical test of the present invention was carried out using a rod coating apparatus in which an excess amount of the coating liquid applied to the web of FIG. 1 was scraped off with a flat coating rod.

[0027] The coating liquid is prepared by putting each component having the composition shown in Table 1 into a ball mill, sufficiently mixing and dispersing, and then adding and uniformly mixing and dispersing 30 parts by weight of an epoxy resin (epoxy equivalent 500). did. The web was made of PET.

[0028]

[Table 1] Table 2 shows the conditions and results of the test.

[0029] As the measuring instrument of maximum protrusion height R _max of Table 2, it was used manufactured by Kosaka Kenkyusho of surf coder SEF-30D.

[0030]

[Table 2] In Examples 1 to 7 in Table 2, the maximum protrusion height R _max (μ
m) and h / 3 (μm), R
_max ≦ h / 3. Comparative Examples 1 to 3
_This is the case where _max ≦ h / 3 is not satisfied.

As a result, Examples 1 to 7
A good product can be obtained without any streak on the fabric film.
Came. In Example 7, the thickness h of the coating film and the maximum protrusion height
Sa R _maxWas the same as in Example 3, and the coating speed was 300 (m
/ Min) to 100 (m / min)
No streak was found on the film.

On the other hand, in Comparative Examples 1 to 3, streaks occurred in the formed coating films in all cases, and the products were rejected.

[0033]

As described above, according to the rod coating method and apparatus of the present invention, a coating film having a desired thickness is formed on a web using a flat coating rod which is advantageous in abrasion resistance. Above, it is possible to make it difficult for foreign matter to be trapped on the rod surface, so that it is possible to suppress occurrence of streak failure of the coating film.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a rod coating apparatus of the present invention of a separate coating and measuring type.

FIG. 2 is an external view of a flat coating rod.

FIG. 3 is an overall configuration diagram of a rod coating apparatus according to the present invention, which is an integrated coating and measuring type.

[Explanation of symbols]

Reference Signs List 10: coating / measuring separate rod coating device, 12: web, 14: coating liquid, 16: precoating device, 18: coating rod device, 20: guide roller, 21: displacement device,
22: Pocket, 24: Slot, 26: Head tip surface, 28: Coating rod, 30: Rod support member, 40
… Integrated application / measurement rod application device, 42… application rod, 50… application liquid pool

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Toshihiro Bandai 1-2-1 Ogimachi, Odawara-shi, Kanagawa F-Film Photo Co., Ltd. F-term (reference) 4D075 AC04 AC53 AC92 DA04 DB18 DC27 DC28 4F041 AA12 AB01 CA02 CA22 CA28 4F042 AA22 BA25 CC02 DD06

Claims (3)

[Claims] 1. A coating rod for simultaneously performing transfer coating of a coating liquid and measurement of a coating amount on a continuously running flexible belt-like support,
Or a coating rod for measuring the amount of application by scraping off the excess amount of the coating solution of the flexible belt-like support to which the coating solution has been excessively applied in advance by a pre-coating device, wherein the coating rod is a flat coating rod In the rod coating method of forming a coating film on the flexible belt-shaped support using the method, the thickness of the coating film is h (μm), and the maximum projection height of the surface roughness of the rod surface of the coating rod is To R _max (μ
m), wherein the relationship between h and _Rmax satisfies _Rmax ≦ h / 3. 2. The rod coating method according to claim 1, wherein the thickness h of the coating film is 15 μm or less. 3. A coating rod for simultaneously performing transfer coating of a coating liquid and measurement of a coating amount on a continuously running flexible belt-like support,
Or a coating rod for measuring the amount of application by scraping off the excess amount of the coating solution of the flexible belt-shaped support to which the coating solution has been excessively applied in advance by a pre-coating device, wherein the coating rod is a flat coating rod In a rod coating apparatus for forming a coating film on the flexible belt-shaped support using: a rod surface of the coating rod, a thickness of the coating film is h (μm), and a surface roughness of the rod surface Wherein a smoothing treatment is performed so as to satisfy R _max ≦ h / 3, where R _max (μm) is the maximum projection height.