Coating apparatus – Solid member or material acting on coating after application – Running length work
Reexamination Certificate
2002-10-29
2004-11-16
Bareford, Katherine A. (Department: 1762)
Coating apparatus
Solid member or material acting on coating after application
Running length work
C118S126000, C118S413000, C427S356000
Reexamination Certificate
active
06818062
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a coating method and an apparatus, and in particular, to a coating method and an apparatus for applying a substrate used for the production of photosensitive material and a magnetic recording medium.
2. Description of the Related Art
Each of photosensitive material and magnetic recording media is produced through a coating step of forming a coating film by applying predetermined coating liquid such as magnetic liquid on a continuously running flexible substrate (hereinafter referred to as a web). In particular, since the capacity and recording density of magnetic recording media such as magnetic recording tapes are rapidly improved as the use for broadcasting and computers, the coating technology of being able to obtain a magnetic layer having thin film thickness and smooth surface has been requested.
As methods of applying coating liquid on a web surface, there are, for example, a roll coater method, a gravure coating method, a roll coater plus doctor method, an extrusion type coating method, and a slide coater type coating method, etc.
Among extrusion type coating apparatuses, in such a coating apparatus of pressing a point of a coating head to a web as disclosed in Japanese Patent Publication No. 5-8065, it is possible to obtain a thin uniform coating layer with excluding air coming with the web by raising hydraulic pressure in the point of the coating head by using web tension. Hence, this type of apparatuses is frequently used in a field of production of magnetic recording media.
However, since there is a limit in the thickness of a possible coating layer even when coating is performed by this extrusion type of coating apparatus, there is a problem that it is not possible to sufficiently respond to a demand of obtaining a magnetic layer with thin film thickness. In addition, there is a defect that a stripe is easily generated in the coating layer due to web cut at the point of the coating head.
From this, as a coating apparatus that can obtain a thinner coating layer without a coating stripe, there is a doctor blade scraping-off type coating apparatus disclosed in Japanese Patent No. 2614119. This coating apparatus obtains a thin coating layer by scraping off an excess of coating liquid with a doctor blade arranged in a downstream side of a roll coater type applicator after applying the excessive coating liquid on a web by the applicator. In this case, though the roll coater type apparatus is used in Patent No. 2614119 as a coating apparatus to apply the excessive coating liquid on the web, it is not limited to this, but it is possible to use a supporting-member-pressurizing extrusion type apparatus, a backed-up extrusion type apparatus, a gravure slide coater type apparatus, or the like.
Nevertheless, though a conventional doctor blade scraping-off type coating apparatus is a coating apparatus that comparatively easily forms a thin coating layer without a coating stripe, there is a defect that the following coating defects may be caused when an ultrathin magnetic layer, which is unprecedented and is 2 &mgr;m or less in a moist state, like those of magnetic recording media in recent years is formed.
(1) Coating thickness distribution is easily generated in a web width direction of a coating layer after scraping-off by the doctor blade due to the thickness distribution of the web itself and single-edged slack.
(2) Coating thickness distribution is easily generated in the web width direction of a coating layer after scraping-off by the doctor blade.
(3) Coating thickness variation is easily generated in a web-traveling direction of a final coating layer after scraping-off by the doctor blade.
(4) Uneven coating may be caused in the web width direction.
(5) A detailed unevenness may be generated as a coating surface gets rough.
(6) Coating stripes may happen frequently.
The above-described coating defects from items (1) to (6) were not problems particularly in the case of coating layer thickness demanded of a magnetic layer of a conventional magnetic recording medium. Nevertheless, they become obvious by making the thickness of a magnetic layer of a magnetic recording medium be 2 &mgr;m or less, which is unprecedented and ultrathin, in a moist state in recent years. Hence, it is necessary to pursue occurrence causes of these coating defects and to exclude their factors.
SUMMARY OF THE INVENTION
The present invention is devised in consideration of such circumstances and aims to provide a coating method and an apparatus for being able to perform ultrathin and uniform coating on a web without causing a coating defect in scraping-off type coating.
In order to achieve the above-described object, the first form of the present invention is characterized in a coating apparatus that scrapes off an excess of coating liquid, excessively applied, with an doctor blade with relatively pressing the doctor blade on a coated side surface of a web after applying of the coating liquid, which is more excessive than desired quantity of coating liquid, on the web by a precoating apparatus while making a web travel continuously, comprising a pressure distribution adjusting device which adjusts pressure distribution in a width direction of the web pressed.
According to the first form of the present invention, a pressure distribution adjusting device adjusting the distribution of pressure, relatively pressuring the doctor blade and the web, in the width direction of the web is installed. Hence, it is possible to intentionally adjusting the scraping-off quantity of coating liquid in the width direction of the web. Owing to this, it is possible to perform the scraping-off of the coating liquid according to the thickness distribution of the web itself, the single-edged slack of the web, and the like. In particular, when a ultrathin magnetic layer, which is unprecedented and has the thickness of 2 &mgr;m or less in a moist state, like a magnetic recording medium in recent years, the influence of the thickness distribution of the web itself and the single-edged slack becomes obvious, but it is possible to solve it by the present invention.
As a preferable form of the pressure distribution adjusting device, a roller is installed in at least one side of an upstream side and a downstream side of the doctor blade in a traveling direction of the web, and this roller is inclined by an inclination mechanism in a width direction of the web. Owing to this, it is possible to adjust pressure distribution in the width direction of the web. In this case, when an expander roller is used as the roller, it is possible not to linearly incline the web in the width direction of the web, but to curvilinearly incline it. Therefore, it is possible not to make the pressure distribution be linear from one edge to another edge in the width direction of the web, but to adjust the pressure distribution curvilinearly.
As another preferable form of the pressure distribution adjusting device, a blade inclination mechanism inclining the doctor blade in the width direction of the web can be also used.
Furthermore, pressure distribution in the width direction of the web can be adjusted with air by installing an air jet nozzle, which can adjust blowing pressure in the width direction of the web, on the opposite side of the doctor blade across the web.
As still another preferable form of the present invention, it is preferable to adjust the pressure distribution in the width direction of the web by a pressure distribution adjusting device so that the coating thickness distribution of a coating layer in the width direction of the web after scraping-off by the doctor blade may become 20% or less.
As a further preferable form of the present invention, it is preferable to have the configuration that coating liquid applied on the web is not exposed to the air during from the applying of the coating liquid on the web to the scraping-off of an excess of the coating liquid. Here, a sentence “coating liquid applied on the web is not exposed to the air” means a
Mandai Toshihiro
Shibata Norio
Tomaru Mikio
Bareford Katherine A.
Fuji Photo Film Co. , Ltd.
Sughrue & Mion, PLLC
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