1. Field of the Invention
The present invention relates to a coating device and a coating method. More specifically, it relates to a coating device and a coating method capable of performing a stable and even coating operation, even in the case of coating a coating liquid agent on the surface of band-shaped substrate, with the substrate running at a high speed.
Furthermore, the invention relates to a coating device and a coating method using a bar coater. More specifically, it relates to a bar coating device and a bar coating method capable of coating a coating liquid agent on an object to be coated being conveyed in a constant direction at a high speed, preferably adopted for cases where the object to be coated has a rough surface.
Furthermore, the invention relates to a bar coating device comprising a bar and a primary side weir member disposed upstream of the bar, capable of effectively preventing drying or adhesion of a coating liquid on the primary side weir member, and a coating method using the coating device.
2. Description of the Related Art
Photographic sensitive materials, printing papers, magnetic recording materials, coated metal plates, planographic printing plate precursors, or the like have been produced by coating a coating liquid such as a plate-making layer forming liquid on a substrate such as a support web.
A bar coater, a slide bead coater, an extrusion coater, of the like have been used for the application of the coating liquid. In particular, the bar coater has been used widely because it is easy to handle.
The bar coater comprising a bar that is rotatable in the same or opposite direction relative to the conveyance direction of the substrate while contacting the lower surface of the continuously running substrate has been conventionally used. In that bar coater, by ejecting the coating liquid upstream of the bar in the substrate conveyance direction (hereinafter referred to simply as “upstream”) while the substrate is running so as to form a bead and taking up the coating liquid by the rotation of the bar, the coating liquid is adhered onto the lower surface of the substrate. The bar may be slaved to the running of the substrate and rotated thereby.
Moreover, in addition thereto, a bar coater disclosed in the specification of the Japanese Utility Model Application Laid-Open No. 63-126213, comprising a first weir plate disposed adjacent to a bar and upstream of the bar, with the thickness of the upper end portion thereof tapered toward the downstream conveyance direction of the substrate hereinafter simply referred to as “downstream”) and the upper end portion bent toward the bar, having a flat surface of the length 0.1 to 1 at the top portion; and a bar coater disclosed in the official gazette of the Japanese Patent Application Publication (JP-B) No, 58-004589 comprising a bar, a first weir plate disposed on the upstream side thereof, with the upper end portion thickness made thinner toward the downstream side, and a second weir plate disposed downstream of the bar, have been commonly used.
For the above bar coaters, a coating liquid is generally discharged between the first weir plate and the bar so as to be coated on the substrate.
Moreover, in the case where the weir plate is provided upstream of the bar, those methods of coating the coating liquid on the substrate by ejecting the coating liquid between the bar and the weir member while forcibly rotating the bar at a circumferential speed different from the conveyance speed of the substrate, have mainly been used.
However, for any of the above bar coaters, when the substrate is running at a high speed, stripe-like defects of an equal pitch can easily be generated. Moreover, when the support web is run at a high speed, an accompanying film of air following the support web, can form on the surface of the support web.
When an entrained air film is formed on the surface of the support web, the entrained air film is brought by the support web to the bead as the coating part, and this generates such defects as coating film cuts and coating irregularities in the coating film of the coating liquid formed on the surface of the support web. Thus there is a problem involved in that the coating liquid cannot be coated on in a stable manner.
Moreover, for the bar coater provided with the weir plate, the coating liquid is intentionally discharged between the first weir plate and the bar, and it cannot always be provided evenly along the substrate width direction.
Therefore, the coating liquid discharged intermittently dries and adheres on the top portion of the first weir plate so that due to the adhered coating liquid solid component, coated surface problems such as coating streaks and solid component adhesion can be generated on the coated surface of the substrate.
Furthermore, in order to coat a coating liquid on an object to be coated such as a metal plate, or eliminate excessive coating liquid from the object to be coated (that is called, “measurement”), a bar coating device 502 as shown in FIG. 20 can be used.
For the bar coating device 502, a columnar (cylindrical) coating bar 506 is provided for a metal plate 504. The columnar coating bar 506 is conveyed at a constant speed in a direction orthogonal to the direction in which the metal plate 504 is conveyed (arrow F1 direction) so as to be contacted with the coated surface (lower surface) of the metal plate 504. The coating bar 506 is rotated at a circumferential speed equal to the conveyance speed of the metal plate 504 by the friction between the metal plate 504 and the coating bar 506. The rotation brings up a coating liquid 508 to provide a bead 510 between a weir member 512 and the metal plate 504. That is, the coating liquid in the bead 510 is coated on the metal plate 504 and the excessive coating liquid is eliminated from the metal plate 504, i.e., measured.
However, for the bar coating device 502, the so-called entrained air enters in at the time of coating so that the bead 510 is not stable. In particular, the conveyance speed of the metal plate 504 has recently been set at high speeds, so that due to the high speeds, the risk of the inability to maintain stability in the bead 510 is increased. If the bead 510 is instable, for example, the coating liquid 508 cannot be coated evenly in the entire width direction of the metal plate 504, so that it is difficult to obtain an evenly coated surface. This is especially true in the case where the surface of the metal plate 504 is coarse, since entrained air can easily be generated, it is further difficult to obtain an evenly coated surface.