JPH0759311B2 - Coating method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention provides a flexible support (hereinafter referred to as a web) formed by forming a plastic film, paper, metal foil, etc., with a photographic photosensitive solution, a magnetic solution, The present invention relates to a coating method and apparatus for coating a coating liquid such as a surface protection liquid.

(Prior Art) Conventionally, as a coating device for coating a coating liquid on a web, there are a roll type coating device, a bead type coating device, a slide coat type coating device, an extrusion type coating device, and the like.
Each of the coating devices has a width direction dimension wider than the width of the web, and the width of the coating portion to which the coating liquid is applied is narrower than the width of the web, and several mm to a dozen or more at both ends of the coating surface of the web. There are some areas where the mm coating solution is not applied.

Therefore, among others, as in the extrusion type coating apparatus disclosed in JP-A-57-84771 and JP-A-59-94657, the coating liquid is coated while pressing the coating head against the running web. In this case, since the gap between the web and the coating head is extremely narrow, uncoated portions of the coating liquid on both ends of the web come into contact with the coating head.

Therefore, the coating head scrapes off the web surface of the uncoated portion, and the scraped scraps adhere to both edges of the coating portion of the coating head. Further, the foreign matter attached to the surface of the web is also captured by the edge of the coating section of the coating head.

Then, since the deposits thus deposited on both ends of the coating portion push up the both ends of the web, the coating thickness of the coating liquid applied to the web in the width direction is not uniform and the vicinity of both ends of the web is There is a problem that the coating layer is thickly coated.

Therefore, in order to solve the above-mentioned problems, as disclosed in JP-A-61-257268, the coating solution on the surface of the support should be applied immediately before the application of the coating solution on the flexible belt-shaped support. Corresponding to the position of the coating width regulating plate of the coating device, as disclosed in Japanese Patent Application Laid-Open No. 61-257263, or a coating method in which the coating liquid is not applied to the outside of both ends of the portion. A coating device and the like in which the apex angle portion of the doctor edge is chamfered are proposed.

However, in the coating method of precoating a solvent or the like as disclosed in JP-A-61-257268, the solvent enters the coating portion of the web surface due to disturbances such as flapping and meandering as the web runs. Of the coating or the back surface of the web is apt to cause uneven coating. Further, the precoat layer has a wider width at the back edge and the doctor edge portion (the head end portion in both cases), but when the width of the uncoated portion becomes narrower or the scraping force of the doctor edge becomes stronger, the solvent gets wet. There was a problem that it was difficult to control the width properly.

Therefore, if such bleeding occurs, for example, in the manufacturing process of the magnetic recording medium, the magnetic coating liquid adheres to the carrier roll running the non-magnetic support, stains the support, and then the surface treatment is performed. It will also stain the calender rolls in the process. As a result, there is a problem in that the surface of the support after the surface treatment step is scratched by foreign matter, and the magnetic recording characteristics are deteriorated.

Further, as disclosed in the above-mentioned JP-A-61-257263, in the coating device in which the doctor edge apex angle portion corresponding to the position of the coating width regulating plate of the coating device is chamfered, the uncoated portion and the back edge are However, there was a problem that the back edge scraped the support and trapped foreign matters.

Therefore, in order to supplement the drawbacks of the above coating method and coating apparatus, as described in Japanese Patent Application No. 63-201996,
On both end surfaces of the tip end of the coating head corresponding to the uncoated portion of the flexible support, an inclined portion or a step portion formed in a direction away from the support in both end directions from the central portion of the tip of the coating head is provided, A coating device has been proposed in which a gap is formed between the surface of the unsupported portion of the flexible support and both end surfaces of the tip end portion of the coating head. Therefore, it is possible to prevent the uncoated portion of the flexible support from being scraped off by the tip of the coating head, and the foreign matter adhering to the surface of the flexible support from being trapped at both ends of the coating head. I was able to.

(Problems to be solved by the invention) However, the web is thin (thickness: 15 to 40 μm)
In the case of the flexible support, the stiffness of the web is weak and both ends of the web are largely bent toward the tip of the coating head. Therefore, there arises a problem that both ends of the web come into contact with the edges of the inclined portion or the stepped portion formed on both end surfaces of the tip end portion of the coating head, and the web is scraped.

Particularly in recent years, polyethylene terephthalate base (hereinafter referred to as PET base), which is a web for magnetic recording media for VTRs.
In some cases, a PET base added with a spherical SiO ₂ filler is used. This reduces contact resistance between the magnetic recording medium and a contact portion such as a guide pole of the magnetic recording / reproducing apparatus when the magnetic recording medium is run over the magnetic recording / reproducing apparatus, and stabilizes tape running. This is because. However, PET with such filler added
Since the base itself has low rigidity, both end portions of the PET base are likely to largely bend toward the tip of the coating head when the coating liquid is applied by the coating device or the like. Then, when the PET base comes into contact with the tip of the coating head, the filler is likely to be exfoliated, and there is a problem that shavings are significantly deposited on the tip of the coating head.

Therefore, an object of the present invention is to solve the above-mentioned problems in the coating device, to form a coating layer having a uniform coating thickness and good surface property even on a thin web that easily bends, and a coating method in which the exudation of the coating liquid does not easily occur. And to provide a device.

(Means for Solving the Problems) The above object according to the present invention is to provide a coating method in which a coating liquid is applied while pressing a slot tip portion of a coating head against a surface of a flexible support that continuously runs. The coating liquid is applied while supporting the edges of the flexible support so that the uncoated portions on both ends of the flexible support do not slide on the end faces of the coating head at least near the coating portion side. It is achieved by a coating method characterized by

That is, a concave portion extending along the running direction of the flexible support is formed on both end surfaces of the tip end portion of the coating head corresponding to uncoated portions on both ends of the flexible support, and the coating forming the concave portion is formed. The coating solution is applied to the surface of the flexible support by a coating device configured such that the shoulders on both side ends of the head support both end edges of the flexible support.

An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

(Embodiment) FIG. 1 is a perspective view of an extrusion type coating head 1 in a coating apparatus according to one embodiment of the present invention.

The coating head 1 has a widthwise dimension larger than the width of the flexible support (web) 2, and a back edge 4 constituting a slot 3 for discharging the coating liquid 15 across the widthwise direction.
And a doctor edge 5 is formed. The slot 3
Is in communication with a liquid pool 13 formed inside the coating head 1, and the coating liquid 15 supplied from a coating liquid supply port 9 provided on a side plate 11 on the side of the liquid pool 13 is stored in the slot. It is discharged with a uniform pressure over the width direction of No. 3.

At both ends of the slot 3 in the width direction, regulation plates 6 are set so that the coating width is set so that the coating liquid is not discharged. Therefore, uncoated portions are formed on both sides of the coated surface of the web 2.

Then, on both end surfaces of the back edge 4 and the doctor edge 5 corresponding to the uncoated portion, recessed portions 12 each having a rectangular cross section continuously extending along the running direction A of the web 2 are provided. There is. Further, the shoulders 8 on both sides of the coating head, which form the concave portion 12, are configured to support both end edges of the web 2.

Then, using the coating apparatus according to the present invention, the thickness 15
μ, width 500mm polyethylene terephthalate support, coating amount: 17cc / m ² , coating speed: 250m / min, coating area tension: 20
The magnetic coating solution was applied so that the coating weight was kg / m and the coating width was 485 mm. The magnetic coating liquid was prepared by placing the magnetic coating liquid having the composition components shown in Table 1 below in a ball mill and mixing and dispersing for 10.5 hours. When the viscosity of the magnetic coating liquid thus obtained was measured with a ring cone type viscometer, the shear rate was 70.
It showed 19 poise at ⁰ sec ^-1 .

Then, a magnetic recording medium having a length of 8000 m was prepared under the above coating conditions, and observation of the occurrence of abrasion in the uncoated portion near the coating layer on both ends of the support and the degree of thick coating of the coating layer side end portion with respect to the average thickness of the coating layer. Was measured. The results are shown in Example 1.
Are shown in Table 2. However, the cross-section rectangular recesses at both ends of the extrusion type head have a coating width direction length of 2.0 m.
The shoulder 8 was processed to have a depth of 0.05 mm and a supporting length of 5 mm.

Table 1 Composition ・ γ-Fe ₂ O ₃ (average powder diameter in major axis direction 0.6μ, Hc320Oe) 300
Parts by weight ・ Vinyl chloride-vinyl acetate copolymer (copolymerization ratio 87:13, degree of polymerization 450) 40 parts by weight ・ Conductive carbon 20 parts by weight ・ Stearic acid 7 parts by weight ・ Silicon oil 3 parts by weight ・ Solvent Xylol 300 parts by weight Part Methyl isobutyl ketone 400 parts by weight Furthermore, described in JP-A No. 61-257263, a coating device comprising an extrusion type head having a beveled corner portion of a doctor edge and Japanese Patent Application No. 63-201996. For each of the coating devices in which the angle of 5 ° is formed on both ends of the extrusion type head,
A magnetic recording medium having a length of 8000 m was prepared under the same coating conditions as in Example 1, and the occurrence of abrasion in the uncoated portions at both ends of the support was observed and the coating layer side edge portion was thickly coated with respect to the average thickness of the coating layer. The degree was measured. The results are shown in Table 2 as Comparative Examples 1 and 2, respectively.

That is, according to the present invention, the coating liquid is applied while pressing the slot tip of the coating head 1 against the surface of the running web 2.
When the coating layer 10 is formed by applying 15, the uncoated portion near the coating layer 10 is the back edge 4 of the coating head 1.
Also, there is no contact with the doctor edge 5. Therefore,
The uncoated portion of the web 2 in the vicinity of the coating layer 10 is scraped off by the back edge 4 and the doctor edge 5, and foreign matter adhering to the surface of the web 2 is removed by the back edge 4 and the doctor edge 5 of the coating head 1. Since it can be prevented from being trapped at both ends of the coating head 10 in the vicinity of the coating layer 10, the deposits deposited on both ends of the coating head 1 in the vicinity of the coating layer 10 push up the both ends of the web 2 in the vicinity of the coating layer 10. As a result, it was possible to prevent the coating thickness of the coating liquid applied to the web 2 from being nonuniform.

Further, as shown in FIG. 2, the web 2 runs while being supported by shoulders 8 provided at both end edges of the coating head 1 because both end edges thereof form the recess 12.
Therefore, even if the web 2 is thin and the waist is weak, both edges of the web 2 are supported, so that both ends of the web 2 are largely bent toward the tip of the coating head, and both edges near the coating layer 10 are coated with the coating. It was possible to prevent the web from being scraped by coming into contact with the head end surface.

However, in the shoulder portion 8, contact with the edge of the web occurs,
Since the edge of the web is scraped, in order to prevent the influence on the coating layer 10, the opening length of the recess in the coating width direction is made sufficiently large, or the web supporting length of the shoulder portion 8 is made large. It is desirable to prevent bending of the web. Further, as shown in FIG. 2, a solvent such as butyl acetate or methyl ethyl ketone 14 is previously formed on the web supporting surface of the shoulder portion 8.
Is preferably applied to prevent abrasion of the web due to the lubricating action of the solvent layer.

Next, FIG. 3 shows an extrusion type coating head 16 in a coating apparatus according to another embodiment of the present invention.

The extrusion type coating head 16 is composed of a back edge 4, a doctor edge 5 and a regulating plate 6 which are substantially the same as those of the extrusion type coating head 1 in the above embodiment.

Then, on both end surfaces of the front edge portions of the back edge 4 and the doctor edge 5 corresponding to the uncoated portion of the web 2,
Instead of the recess 12 having a rectangular cross section, a recess 17 having a V-shaped cross section is provided continuously extending along the running direction of the web 2. Further, the shoulders 8 on both sides of the coating head, which constitute the recess 17, are configured to support both end edges of the web 2.

Therefore, similar to the extrusion type coating head 1 in the above-described embodiment, the uncoated portion near the coating layer 10 does not come into contact with the back edge 4 and the doctor edge 5 of the coating head 1. It is possible to prevent the coating thickness of the coating liquid applied to No. 2 from becoming nonuniform.

In addition, the concave portion having a rectangular cross section formed in the above embodiment
It goes without saying that the shape of the concave portion 12 having a V-shaped cross section and the shape of the concave portion 17 having a V-shaped cross section can take various shapes based on the gist of the present invention.

Further, the coating device is not limited to the extrusion type coating head, and any other coating device can be used as long as it is a coating device that coats the coating liquid while pressing the slot tip of the coating head against the surface of the flexible support that continuously runs. A device can also be used.

(Effects of the Invention) As described above, according to the present invention, the flexible support has the above-described structure so that the uncoated portions at both ends do not slide on the both end surfaces of the coating head tip portion at least near the coating portion side. The coating liquid is applied while supporting the edge of the flexible support.

Therefore, even in the case of a thin flexible support, the unapplied part near the application part side is scraped off by the tip of the application head, or foreign matter adhering to the surface of the flexible support is applied to both ends of the application head. Since it can be prevented from being trapped, the deposits deposited on both ends of the coating head push up the both ends of the flexible support and are applied to the flexible support in the width direction. It is possible to prevent the coating thickness from becoming uneven.

Therefore, it is possible to form a coating layer having a uniform coating thickness and good surface properties, and to provide a good coating method and apparatus in which the coating liquid does not seep out.

[Brief description of drawings]

FIG. 1 is a perspective view of an extrusion type coating head in a coating apparatus according to an embodiment of the present invention, FIG. 2 is a partial sectional view of the extrusion type coating head shown in FIG. 1, and FIG. It is a perspective view of the extrusion type coating head in the coating device based on another embodiment. (Reference numeral in the figure) 1,16 …… Extrusion type coating head 2 …… Flexible support 3 …… Slot 4 …… Back edge 5 …… Doctor edge 6 …… Regulation plate, 8 …… Shoulder Part 9 ... Liquid supply port, 10 ... Coating layer 11 ... Side plate, 12 ... Rectangular concave section 13 ... Liquid pool, 14 ... Solvent 15 ... Coating solution, 17 ... V-shaped section concave section

Claims (2)

[Claims] 1. A coating method for coating a coating liquid while pressing the tip of a slot of a coating head against the surface of a flexible support that is continuously running, wherein at least uncoated portions at both ends of the flexible support are coated. A coating method, wherein the coating liquid is coated while supporting the edge of the flexible support so that it does not slide on both end surfaces of the tip of the coating head in the vicinity of the section side. 2. A coating device for coating a coating liquid while pressing a slot tip portion of a coating head against the surface of a flexible support body that continuously runs, wherein the flexible support body has uncoated portions at both ends thereof. Recesses extending along the running direction of the flexible support are formed on both end surfaces of the tip of the coating head, and the shoulders on both side ends of the coating head forming the recesses are both edges of the flexible support. An application device, which is configured to support the.