JP2001000899A - Coating method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of coating stripes or coating spots due to scum generated by the drying of a coating liquid at the time of applying a coating liquid onto a film by an applicator roll rotated opposed to the travelling direction of the film. SOLUTION: A the time of forming a coating film 5 with the applicator roll 3 rotated opposed to the travelling direction of the travelling plastic film 1 onto the film 1, the solidification of the coating liquid on the surface of the roll 3 due to the coating liquid remaining in fine pores or fine grooves is prevented by using the applicator roll 3 having a surface roughness Ra of 0.05 μm<=Ra<=1.0 μm and 0.8<=Rmax<=20 μm and fine pores 3a or a fine groove structure on the surface.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating method and an apparatus therefor, and more particularly, to a method for coating a running plastic film with an applicator roll rotating in a direction opposite to the running direction of the film. TECHNICAL FIELD The present invention relates to a coating method and a coating device for preventing generation of coating streaks and coating spots due to scum generated by drying of a coating.

[0002]

2. Description of the Related Art A film (including a sheet-like base material) such as a plastic film is easily adhered, easily slidable, and gas-insulated.
Generally, coating is performed for the purpose of imparting functions such as moisture proof, antistatic, and ink receptivity.
Examples of the coater used for this include a gravure coater, a kiss roll coater, a reverse roll coater, a slide coater, a curtain coater, a knife coater,
Extrusion die coaters and the like are known. Among them, the reverse roll coater has the merit that the amount of application can be easily changed by changing the rotation speed of the roll, and there are many examples in which it is used. The applicator roll of this coater is usually provided with hard chrome plating which is high in hardness and relatively easy to mirror finish.

[0003]

However, since a very thin coating film remains on the applicator roll immediately after transferring the coating liquid to the film, the coating liquid slightly dries and solidifies. The scum of the coating liquid is accumulated by repetition. Then, the accumulated scum stays between the applicator roll and the film to generate coating streaks.

In order to suppress the occurrence of this defect, Japanese Patent Application Laid-Open No.
As shown in JP-A-71474, a thick coating is formed on a running film in advance, and then the coating is transferred to an applicator roll and weighed to a desired coating amount. A method of transferring can also be used. However, this method requires a mechanism for forming a thick coating film on the running film in advance, which complicates the apparatus and has a problem that the operation becomes complicated. The present inventor has earnestly studied to solve this problem, and as a result, has arrived at the present invention.

[0005]

That is, the present invention comprises the following constitutions. (1) When a coating film is formed on a running plastic film using an applicator roll rotating in a direction opposite to the running direction of the film, the surface roughness (Ra) is 0.0
5 μm ≦ Ra ≦ 1.0 μm and 0.8 μm ≦ Rma
A coating method using an applicator roll having a micropore or microgroove structure on the surface, where x ≦ 20 μm. Here, the maximum height (Rmax) is the maximum height of the extracted portion corresponding to the reference length L of the sectional curve. That is, the cross-sectional curve is used when measuring the surface roughness.
The vertical axis is a graph in the vertical magnification direction, and the horizontal axis is the recorded direction. The cross-sectional curve is extracted in the horizontal axis direction by the reference length L, and two straight lines parallel to the average line of the cross-sectional curve of the extracted part are shown. When the cross-section curve is interposed, the distance between the two straight lines in the vertical axis direction is measured, and the value is measured by a micrometer (μ
m). (However, when obtaining the maximum height, a portion having no extraordinarily high peaks or deep valleys that are regarded as scratches is extracted by a reference length L.) (2) The coating film finely disperses solids in water Alternatively, the coating method according to (1), which comprises a dissolved coating solution. (3) The coating method according to (1), wherein the plastic film is a continuous running film in a film forming line. (4) An apparatus for forming a coating film on a running plastic film using an applicator roll rotating in a direction opposite to the running direction of the film, wherein the surface roughness of the applicator roll is 0.05 μm ≦ Ra ≦ 1 0.0 μm, and
A coating apparatus characterized by having a micropore or microgroove structure on the surface, wherein 0.8 μm ≦ Rmax ≦ 20 μm. (5) The coating device according to (4), wherein the applicator roll has a ceramic sprayed film formed on a surface thereof. (6) The coating device according to (4), wherein the applicator roll forms a sprayed cemented carbide film on the surface of the roll.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be further described below with reference to the drawings. FIG. 1 is an explanatory view of a main part of an applicator roll portion of a coating apparatus according to an embodiment of the present invention. FIG. 2 is a schematic diagram for explaining a coating apparatus according to one embodiment of the present invention.

In FIG. 1 and FIG. 2, reference numeral 1 denotes a running film which is provided with a coating liquid on a film 1 by an applicator roll 3 and a metering roll 4 which are disposed in a coating liquid pan 2 and rotate in an arrow direction. Then, the coating film 5 is formed and sent in the direction of the arrow. 6 is a doctor blade. Reference numeral 7 denotes a measured coating film on the applicator roll 3, 8 denotes a liquid pool between the applicator roll 3 and the film 1, and 9 denotes a remaining coating film on the applicator roll 3.

Here, the surface of the applicator roll 3 is represented by surface roughness, 0.05 μm ≦ Ra ≦ 1.0 μm.
m and 0.8 μm ≦ Rmax ≦ 20 μm in a fine hole 3a or fine groove structure. The surface corresponding to the application surface of the applicator roll 3 need not be completely mirror-finished, but is polished. It may be in a form in which the fine holes 3a are scattered as shown in FIG. 1, a fine groove or a mixture of these.

In the case of such a mirror-applied applicator roll 3 having no holes or grooves, the residual coating film 9 of the applicator roll becomes very thin and solidifies in an extremely short time. However, in the present invention, since the coating liquid remains in the above-described fine holes and grooves, even if the non-solid content of the coating liquid evaporates, it can be prevented from completely solidifying. However, if the surface roughness of the applicator roll is unnecessarily rough, it causes abrasion on the film, foaming of the coating liquid, and coating unevenness. On the other hand, if the coating liquid is too flat, the coating liquid cannot be held, and the effect of preventing the coating liquid from solidifying is reduced.

Therefore, the surface properties of the applicator roll suitable for the present invention can be expressed by a conventionally well-known roughness parameter: 0.05 μm ≦ Ra ≦ 1.0 μm and 0.8 μm.
If the range of μm ≦ Rmax ≦ 20 μm is satisfied, the above-mentioned problem is solved. This range is more preferably 0.1
μm ≦ Ra ≦ 0.5 μm and 2 μm ≦ Rmax ≦ 10μ
m, so that a more stable and high quality product can be obtained for a long time without any trouble.

A good coated surface can be obtained at a rotation speed of the applicator roll 3 of 1.05 to 2.0 times that of the film. It is more preferable to apply at a speed of 1.1 to 1.5 times.

The surface of the applicator roll may be coated with hard chrome plating, which is commonly used in the prior art. Finished ones are more preferable because secondary advantages such as wear resistance and low friction coefficient can be expected. In order to finish the surface roughness specified by the present invention by hard chrome plating, it is more preferable and effective to adopt a structure in which a large number of fine cracks are present as shown in JP-B-61-39177. is there.

The running film 1 is a plastic film. Examples of the plastic film include a polyolefin film (eg, a polyethylene film and a polypropylene film) and a polyester film (eg, a polyethylene terephthalate film, a polyethylene film).
2,6-naphthalate film and the like), polyamide film (for example, polyetheretherketone film and the like), polycarbonate film and the like. Among them, a polyester film, particularly a polyethylene terephthalate film and a polyethylene-2,6-naphthalate film are preferred.

The traveling film 1 can be coated well in the thickness range of 5 to 800 μm, preferably 10 to 20 μm.
0 μm is good. The running speed of the running film is 5-500m
/ Min, preferably 10 to 350 m / m
in is optimal.

In the present invention, the coating liquid has functional properties on the film surface, for example, adhesion (including easy adhesion, heat sealability), easy slip (running), antistatic property, conductivity, and abrasion resistance. Resistance, abrasion resistance, weather resistance, mold release properties, chemical resistance (including, water resistance, solvent resistance), easy printability, dripping properties, stain resistance, writing properties,
Any coating solution may be used as long as it is a surface processing coating liquid that imparts light-shielding properties, waterproof properties, gas barrier properties, and the like. As these coating liquids, those conventionally known or used can be used. The viscosity of the coating liquid is 1 to 100
Centipoise (cp) is available, 1.1 to 10 cp
Is preferred.

[0016]

The present invention will be described in more detail with reference to the following examples.

Example 1 A pellet of polyethylene terephthalate having an intrinsic viscosity (o-chlorophenol, 35 ° C) of 0.65 was mixed at 180 ° C with 5 pellets.
After vacuum drying for an hour, the mixture was supplied to an extruder heated to 270 to 300 ° C. and formed into a sheet by an extrusion die. Further, this film was adhered and solidified on a cooling drum having a surface temperature of 25 ° C. by static electricity to obtain an unstretched film.
The unstretched film is heated by a group of heating rolls at 80 to 100 ° C. and stretched longitudinally in one step by 3.4 times in a longitudinal direction.
Cooled by rolls at ℃, thickness 180μm, width 600mm
Was obtained. Subsequently, FIGS. 1 and 2
The continuous application of the coating liquid to the uniaxially stretched running film 1 (speed 50 m / min) was performed using the equipment shown in (1). The coating liquid is an aqueous coating liquid film having the following composition.

Coating composition: acid distribution is terephthalic acid (90 mol%), isophthalic acid (6 mol%) and potassium 5-sulfoisophthalate (4 mol%), glycol components are ethylene glycol (95 mol%) and neo Pentyl glycol (5 mol%) copolymerized polyester (Tg = 6)
8 ° C.), 80% by weight, N, N′-ethylenebiscaprylic amide 5% by weight, acrylic resin fine particles (average particle size 0.03 μm) 10% by weight, and polyoxyethylene nonylphenyl ether 5% by weight An aqueous coating liquid having a solid content concentration of 5%, comprising the composition of

The applicator roll 3 has a coating width of 500 m.
m, a tungsten carbide coated roll having a coating portion diameter of 150 mm, surface roughness Ra = 0.1 μm, Rma
When x = 0.8 μm, many fine holes exist on the surface. The applicator roll 3 was rotated in the opposite direction to the running film 1 at a speed of 56 m / min. The metering roll 4 is a mirror roll having a diameter of 100 mm and subjected to hard chrome plating. The gap between the applicator roll 3 and the metering roll 4 is set to 0.02 mm, and the surface speed is 40 m in the opposite direction to the applicator roll 3. The coating amount was 15 g / m ² at a speed of / min. The temperature of the atmosphere during coating is 20 to 25 ° C, and the humidity is 20 to 25.
%.

In this state, the coating condition was observed over time. When the surface of the applicator roll 3 was visually observed after about 8 hours from the start of coating, scum due to drying of the coating liquid was not seen, and the state was good. No coating defects were seen on the coated surface.

Example 2 Surface roughness Ra of applicator roll 3 is 0.7 μm, R
The coating liquid was continuously applied to the uniaxially stretched running film 1 in the same manner as in Example 1 except that the roll was a ceramic-coated roll having a maximum of 10 μm and having many fine holes on the surface.

When the surface of the applicator roll 3 was visually observed after a lapse of about 8 hours from the start of coating, no scum of the coating liquid was observed and the coating liquid was in a good state. A small number of bubbles were observed on the upstream side of the film running in the liquid pool 8, but the coating surface was not affected and there was no coating defect.

Comparative Example 1 The applicator roll had a surface roughness Ra = 2.0 μm, Rm
A continuous application of the coating liquid to the uniaxially stretched running film 1 was performed in the same manner as in Example 1 except that the roll was a hard chrome plating roll with ax = 5.0 μm.

Scratches due to direct contact between the applicator roll and the film were observed on the entire coated surface of the film. Further, a large number of bubbles were present in the liquid pool 8, and streaks were formed on the application surface. These defects prevented the product from being taken.

Comparative Example 2 The applicator roll has a surface roughness Ra = 0.02 μm, R
The coating liquid was continuously applied to the uniaxially stretched running film 1 in the same manner as in Example 1, except that the roll was a hard chrome plating roll with max = 0.1 μm.

When the surface of the applicator roll was visually observed after elapse of about 2 hours from the start of coating, it was found to be cloudy due to the scum of the coating liquid. In the liquid pool 8, there was a coating streak due to the scum piece, and a strong thin spot was observed on the coating surface. These defects prevented the product from being taken.

[0027]

According to the coating method and the coating apparatus of the present invention, it is possible to effectively prevent the generation of coating streaks and coating unevenness due to drying of the coating liquid, and to stably produce a high-quality film without coating defects for a long time. Obtainable.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a main part of an applicator roll portion of a coating apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic view of a coating apparatus representing one embodiment of the present invention.

[Explanation of symbols]

 1: running film 2: coating liquid pan 3: applicator roll 3a: micropore 4: metering roll 5: coating on running film 6: doctor blade 7: measuring coating micropore on applicator roll 8: applicator roll Pool between film and film 9: Residual coating film on applicator roll

Continued on front page F term (reference) 4D075 AC26 AC29 AC35 AC84 DA03 DB31 EA10 4F040 AA22 AB20 AC01 BA23 CB01 CB06 CB22 CB36 CB40 DB22 4F041 AA12 AB01 CA12

Claims (6)

[Claims] When a coating film is formed on a running plastic film using an applicator roll rotating in a direction opposite to the running direction of the film, a surface roughness (Ra) is used.
Wherein 0.05 μm ≦ Ra ≦ 1.0 μm and 0.8 μm ≦ Rmax ≦ 20 μm, using an applicator roll having a micropore or microgroove structure on the surface. 2. The coating method according to claim 1, wherein the coating film comprises a coating solution in which a solid content is finely dispersed or dissolved in water. 3. The coating method according to claim 1, wherein the plastic film is a continuous running film in a film forming line. 4. An apparatus for forming a coating film on a running plastic film using an applicator roll rotating in a direction opposite to the running direction of the film, wherein the surface roughness (Ra) of the applicator roll is 0. A coating apparatus characterized by having a micropore or microgroove structure on the surface, wherein 0.5 μm ≦ Ra ≦ 1.0 μm and 0.8 μm ≦ Rmax ≦ 20 μm. 5. The coating apparatus according to claim 4, wherein the applicator roll has a ceramic sprayed film formed on a surface thereof. 6. The coating apparatus according to claim 4, wherein the applicator roll has a sprayed cemented carbide film formed on the surface of the roll.