JPH07185B2 - Coating method and coating device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a coating method and a coating apparatus, and more particularly to solvent coating.

BACKGROUND OF THE INVENTION There are various methods and apparatuses as a coating method and a coating apparatus for forming a coating liquid layer on a support. The choice depends on the surface condition of the substrate to be coated, the properties of the paint such as absorbency and strength, the rheological properties of the paint, and most importantly the properties of the dry coating required.

For example, air doctors, blade coaters, knife coaters, reverse roll coaters, transfer roll coaters, gravure coaters, cast coaters, curtain coaters, extrusion coaters, bead coaters and the like are known.

Of these coating methods, a reverse roll coater is often used when, for example, a magnetic recording material is coated on a support to produce a magnetic recording material. The reverse roll coater is composed of a metal mainly iron applicator roll, a rubber back roll, and a metal mainly iron metalling roll,
The width of the applicator roll is usually made wider than the width of the support in view of coating properties. In such a case, the coating material remains on both sides of the coating material attached to the applicator roll outside the width of the support. Therefore, particularly when a low boiling point organic solvent is used as a solvent in the paint, the solvent of the paint remaining on the applicator roll is evaporated, the applicator roll is cooled by this heat of vaporization, The diameter shrinks. Therefore, the gap between the metering roll or blade that adjusts the liquid thickness on the applicator roll and the applicator roll changes, the gap on both sides expands, and the liquid thickness on the applicator roll increases toward both sides. Therefore, the coating film thickness becomes thicker on both sides. Therefore, the coating stability may be impaired and the yield may be significantly reduced.

[Problems to be Solved by the Invention] An object of the present invention is to provide a coating gap particularly when a coating liquid containing a low boiling point solvent is coated by a reverse roll coater composed of a back roll, an applicator roll and a metering roll as described above. It is an object of the present invention to provide a coating method and a coating device having a stable film thickness accuracy by improving the accuracy. Another object of the present invention is to provide a coating method and a coating device that can improve the coating yield by stabilizing the coating.

[Means for Solving the Problems] The above object of the present invention is to provide a method of applying a coating material onto a support by using a reverse roll coater comprising at least an applicator roll, a back roll and a metalling roll. A coating method characterized by coating while heating both sides of the ring roll, and what can be achieved by a coating device having heating means on both sides of the metal ring roll in order to realize the coating method. I found it.

Next, the details of the present invention will be specifically described with reference to the drawings. First
The figure is a cross-sectional view of a reverse roll coater. FIG. 3A shows an example in which a fountain coater 6 is used to attach the coating material to the applicator roll 2 and a metering roll is used to regulate the film thickness. FIG. 2B shows an example in which the big up roll 7 is used instead of the fountain coater. In the reverse roll coater, the coating liquid adhered to the applicator roll 2 via the fountain coater or the big-up roll has a nip which is properly set by the counter-rotating metering roll 3 in FIGS. 1 (a) and 1 (b). The width is reduced.

In this case, the amount of the coating liquid on the applicator roll depends on the nip width between the applicator roll and the metering roll and these
Adjusted by the relative surface speed of the two rolls. Then, the coating liquid is attached to the support conveyed by the back roll by the nip pressure between the back roll and the applicator roll.

FIG. 2 (a) is a perspective view showing the relationship among the applicator roll 2, the back roll 1, and the support 4. As seen in the figure, the width of the support is narrower than the overall width of the applicator roll. On the other hand, the coating liquid is applied to the applicator roll over almost the entire width. This is because both sides of the applicator roll are vacant due to the problem of coatability on the support, but for this reason, the coating liquid on the applicator roll remains on both sides. When this coating liquid contains a low boiling point solvent, the solvent evaporates, and the heat of vaporization causes both sides of the applicator roll to contract. FIG. 2 (b) is a perspective view showing the relationship between the deformed applicator roll and the metering roll which is the application liquid amount adjusting means. As shown in FIG. The amount of liquid on both upper sides increases. The liquid on the applicator roll is attached to the support by the nip with the back roll, so that the coating film thickness increases toward both sides. FIG. 3 (a) is an example showing the variation of the film thickness in the width direction of the support under the above-mentioned conditions, and the coating film thickness is clearly thicker on both sides than in the central portion. For example, in the case of a magnetic recording medium, the thickness of the magnetic layer differs depending on the application such as audio, floppy disk, video, etc., but it is about several μm, and the practically acceptable film thickness is about ± 5 of the magnetic layer film thickness. Must be within%. ± 0.1μ for recently densified floppy disks
It is about m. Therefore, in such a case, the coating yield is greatly impaired.

Therefore, in the present invention, the applicator roll is expanded by heating both sides of the metering roll so as to correspond to the deformed applicator roll as shown in FIG. It is intended to prevent the influence of the deformation of the roll and to keep the gap between the applicator roll and the metering roll constant over the entire width. FIG. 4 is a perspective view showing the relationship between the metering roll expanded by heating on both sides and the deformed applicator roll.

Various methods can be considered as means for heating both sides of the metering roll. For example, there are the following means.

Hot air, hot water heater, infrared induction heating, etc.

An example of an embodiment in which warm air is used is shown in FIG. In this method, the air flow sent by the blower 15 is heated by the heater 14, and the warm air thus obtained is blown by the flexible pipes 16 to both side surfaces of the metering roll to heat it. Of course, as the means for heating the airflow, a heating method may be used in addition to the heater by various heat exchange methods using a known heat medium. An example of an embodiment in which hot water is used is shown in FIG. 5 (b). This is a method of circulating hot water inside the metering roll. Hot water is introduced from a hot water introduction pipe 12 at the center of the roll, both sides of the metering roll are heated by a hot water jacket 11, and hot water is circulated through a hot water discharge pipe 13 outside the hot water introduction pipe at the center of the roll. In this case, other heat medium can be used instead of hot water. Heating with a heater is a method in which a heater is arranged near the metering roll and heating is performed directly. Also, heaters may be built in on both sides of the metering roll.

Infrared heating is a method of heating by placing infrared light bulbs on both sides of the metering roll.

The induction heating jacket roll is a method in which the heat medium enclosed in the roll is heated by low-frequency induction heating to make the surface temperature of the roll uniform.

Although several examples of the heating means of the present invention have been given, the present invention is not limited to this, and any heating means may be used as long as it can heat both sides of the metering roll. The control of these heating controls the film thickness after coating and drying on-line or off-l.
This can be done by measuring with ine and feeding back this information.

[Examples] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1 A coating having the following constitution was applied on a 13-μm polyethylene terephthalate support to a dry thickness of 4.2 μm while using the reverse roll coater of FIG. 1 (a) and heating with warm air shown in FIG. 5 (a). It was applied so that

Structure of Magnetic Coating Material First, the following magnetic coating material containing no curing agent was prepared.

Co-containing γ-Fe ₂ O ₃ 300 parts Partly hydrolyzed vinyl chloride-vinyl acetate copolymer (“VAGH” 40 parts by Union Carbide Co., Ltd. 40 parts polyurethane (“Nipporan N-3022” by Nippon Polyurethane Co., Ltd.) Silicone oil 4 parts Toluene / methyl ethyl ketone = 1/1 800 parts The above composition was put into a ball mill, dispersed for 48 hours and filtered with a filter having an average particle size of 3 μm to obtain a magnetic paint.18 kg of this magnetic paint was put into a tank and stirred. However, 25 parts of isocyanate compound (“Coronate L” manufactured by Nippon Polyurethane Company) 10 parts of terminal NCO urethane prepolymer Toluene / methyl ethyl ketone = 1/1 Add 0.6 kg of a curing agent having a composition of 105 parts and leave for 10 hours, then cure as described above. 0.6 kg of the agent was added, and the mixture was stirred for 10 minutes and then applied.

The results are shown in FIG. The results are shown by the film thickness distribution in the width direction of the support after drying.

The same figure (a) is a case where hot air is not sent, and the film thickness is thick on both sides. (B) shows warm air at room temperature of 10 ° C
This is the case when coating is performed while blowing air at a high air pressure of 50 mmH ₂ O, and the film thickness is smooth over the entire width. From these results, it can be seen that the film thickness can be stabilized by a method of heating both side surfaces of the metering roll under appropriate warm air conditions.

Example 2 Instead of using the warm air of Example 1, heating was performed with the warm water shown in FIG. 4 (b). The warm water jacket 11 had a width of 5 cm from the end of a 400 mm wide metering roll and a diameter of 30 cm. The warm water was set at a roll surface temperature of + 3 ° C. and the flow rate was 1.0 m ³ / H. As a result, the film thickness distribution was uniform as in FIG. 3 (b) of Example 1.

EFFECTS OF THE INVENTION In the case of applying a coating material containing a low boiling point solvent by a reverse roll coater consisting of a back roll, an applicator roll and a metering roll according to the present invention, the roll gap precision is improved to stabilize the film thickness precision. The coating method and the coating apparatus were provided, and as a result, the coating method and the coating apparatus capable of improving the coating yield could be provided.

[Brief description of drawings]

FIG. 1 is a sectional view of a reverse roll coater used in the present invention. FIG. 2 (a) is a perspective view showing the relationship between the deformed applicator roll and the support. FIG. 2B is a perspective view for explaining the gap between the deformed applicator roll and the metering roll. FIG. 3 is a view showing the film thickness distribution in the width direction after coating and drying. FIG. 4 is a perspective view showing a relationship between a metering roll having a diameter on both sides larger than that of the central portion and a deformed applicator roll according to the present invention. 5 (a) and 5 (b) are perspective views or sectional views showing an embodiment of the heating method for both sides of the metering roll according to the present invention. 1: Back roll 2: Applicator roll 3: Metalling roll, 4: Support 6: Fountain coater 7: Big up roll, 9: Axial roll 11: Hot water jacket 12: Hot water inlet pipe 13: Hot water discharge pipe, 14: Heater 15: Blower 16: Flexible pipe

Claims (2)

[Claims] 1. A method of applying a coating solution onto a support using a reverse roll coater comprising at least an applicator roll, a back roll and a metering roll, wherein both sides of the metering roll are heated. A coating method characterized by that. 2. A coating apparatus comprising a reverse roll coater comprising at least an applicator roll, a back roll and a metering roll, and heating means on both sides of the metering roll.