JPH0822411B2 - Coating device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention provides a flexible strip-shaped support formed by forming a plastic film, paper, metal foil, etc., with a photographic photosensitive solution, a magnetic solution, a surface protective solution, etc. The present invention relates to a coating device that coats a coating liquid.

(Prior Art) Conventionally, as a coating method for coating a coating solution on a flexible belt-shaped support, there are a roll type coating method, a bead type coating method, a slide coat type coating method, an extrusion type coating method and the like. As a coating device, the width of the flexible strip-shaped support is wider than that of the flexible strip-shaped support, and the width of the coating portion to which the coating liquid is applied is narrower than the width of the flexible strip-shaped support. A portion A where the coating liquid 2 of several mm to several tens of mm is not applied to both ends of the application surface of the flexible belt-like support 1 shown
Occurs.

Therefore, particularly when the coating liquid is applied while pressing the coating head of the extrusion type coating device against the running flexible belt-shaped support, the gap between the flexible belt-shaped support and the coating head is increased. Is extremely narrow, the uncoated portions of the coating liquid on both ends of the flexible belt-shaped support and the coating head will come into contact with each other. Therefore, the coating head scrapes off the surface of the support in the uncoated portion, and the scraped scraps adhere to both ends of the coating portion edge of the coating head. Further, the foreign matter attached to the surface of the support 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 both ends of the flexible strip-shaped support, the coating thickness of the coating liquid applied to the flexible strip-shaped support is uniform in the width direction. However, there is a problem that the coating layer near both ends of the support is pressure coated. In particular, the thinner the coating thickness of the coating layer (wet coating amount 30 cc / m ² or less), or the faster the coating speed of the coating layer (coating speed 200 m / min or more), this becomes remarkable.

Therefore, in order to solve the above-mentioned problems, JP-A-61-257268
As disclosed in Japanese Unexamined Patent Publication (Kokai), just before applying the coating liquid to the flexible belt-shaped support, the solvent is preliminarily applied to the portions of the support surface on which the coating liquid is not applied, on the outer sides of the portions to be applied with the coating liquid. As disclosed in JP-A-61-257263, there is proposed a coating device in which a doctor edge apex angle portion corresponding to the position of the coating width regulating plate of the coating device is chamfered. There is.

(Problems to be Solved by the Invention) However, in the coating method of precoating with a solvent or the like as disclosed in JP-A-61-257268, fluttering, meandering and the like accompanying the running of the flexible belt-like support The solvent is likely to enter the coating portion on the surface of the flexible strip-shaped support body or to go around the back surface of the flexible strip-shaped support body due to the disturbance of 1. 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, the surface of the support after the surface treatment step is scratched by foreign matter, causing problems such as increase in dropout and deterioration of magnetic recording characteristics.

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.

Particularly, when the flexible strip-shaped support is a thin (thickness: 40 μm or less) flexible support, the flexible strip-shaped support has a weak waist and both ends thereof are largely bent toward the tip of the coating head. I will end up. For this reason, both ends of the flexible strip-shaped support come into contact with the edges of the inclined portions or stepped portions formed on both end surfaces of the tip end portion of the coating head, and the flexible strip-shaped support is scraped.

Therefore, an object of the present invention is to solve the problems in the above coating method, and to provide a coating device which forms a coating layer having a uniform coating thickness and good surface properties, and at which solvent exudation hardly occurs.

(Means for Solving the Problem) The above object of the present invention is to provide a coating device for coating a coating liquid while pressing a slot tip portion of a coating head against a surface of a continuously running flexible strip-shaped support, the flexible device comprising: A discharge port for discharging a pressurized fluid toward both ends of the flexible belt-shaped support is provided at both ends of the tip of the coating head corresponding to uncoated portions of both ends of the flexible belt-shaped support, and is blown from the discharge port. By interposing the pressurized fluid between both ends of the flexible strip-shaped support and both ends of the coating head tip,
This is achieved by a coating device characterized in that it is configured so as to avoid contact between the uncoated portions at both ends of the flexible strip-shaped support and both ends of the tip end portion of the coating head.

That is, discharge ports for discharging fluid toward both end edges of the flexible strip-shaped support are provided on both end surfaces of the tip end portion of the coating head corresponding to uncoated portions on both ends of the flexible strip-shaped support. A coating liquid is applied to the surface of the flexible support so that the fluid blown out from the outlet biases both end edges of the flexible support.

As the fluid, for example, a gas such as pressurized air or a liquid such as a solvent can be used as long as it does not adversely affect the coating liquid.

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

(Embodiment) FIGS. 1 and 2 are a partial perspective view and a partial cross-sectional view of an extrusion type coating head 10 in a coating apparatus according to an embodiment of the present invention.

The coating head 10 has a width direction dimension wider than the width of the flexible support (web) 1, and the back edge 4 constituting the slot 3 for discharging the magnetic coating liquid 15 across the width direction. And a doctor edge 5 is formed. The slot 3 communicates with a liquid pool 13 formed inside the coating head 10, and the magnetic coating liquid is supplied from a coating liquid supply port 9 provided on a side plate 11 on the side of the liquid pool 13. 15
Are discharged at a uniform pressure over the width direction of the slot 3.

At both ends of the slot 3 in the width direction, a coating width regulating plate 6 is set so that the coating width is set so that the magnetic coating liquid 15 is not discharged. Therefore, uncoated portions are formed on both sides of the coated surface of the web 1.

The side plate 11 is provided above the coating width regulating plate 6.
There is provided a spacer 7 which constitutes, together with the coating width regulating plate 6, a discharge port 8 communicating with the pressurized air supply port 12 provided in the. The discharge port 8 is formed such that its blowing direction is substantially upward corresponding to the uncoated portion, and is blown from a blower (not shown) connected to the pressurized air supply port 12. The blowing direction, the opening area, and the like are appropriately set depending on the pressure and flow rate of the pressurized air.

That is, according to the present invention, when the magnetic coating liquid 15 is applied to form the coating layer 2 while pressing the slot tip portion of the coating head 10 against the surface of the running web 1, the coating layer 2 in both end directions is formed. The uncoated portion is pushed up by the pressurized air blown out from the discharge port 8, and the coating head 10
There is no contact with the back edge 4 and the doctor edge 5. Therefore, the uncoated portion may be scraped off by the back edge 4 and the doctor edge 5, or foreign matter adhering to the surface of the web 1 may be captured at both ends of the back edge 4 and the doctor edge 5 of the coating head 10. The magnetic coating liquid 15 is applied to the web 1 by pushing up the deposits deposited on both ends of the coating head 10 in the vicinity of the coating layer 2 to push up both ends of the web 1 in the vicinity of the coating layer 2. It is possible to prevent the coating thickness in the width direction from becoming uneven.

The pressure of the pressurized air is set to a gauge pressure of about 0.01 kg / cm ^{2 to 5} kg / cm ² by a pressure adjusting valve or the like depending on the coating speed of the web 1 and the web thickness, and the flow rate is also controlled appropriately by the flow rate control valve. It Therefore, even if the web 1 is thin and the waist is weak, both ends of the web 1 are appropriately pushed up by the pressurized air, so that both ends of the web 1 are bent toward the tip of the coating head, and the tip end surface of the coating head is bent. It was possible to prevent the abrasion of the web 1 due to the contact.

In the above embodiment, pressurized air was used as the fluid for urging both ends of the web 1 upward, but the present invention is not limited to this, and other gas such as nitrogen gas may be used. It can also be used. However, it is preferable to dehumidify such a gas in order to prevent dew condensation on the web surface and further adjust the temperature to room temperature.

Further, as another embodiment of the present invention, it is possible to provide an extrusion type coating head using a solvent instead of the pressurized air in the above embodiment.

That is, the magnetic coating liquid 15 is applied to the surface of the running web 1 by pressing the slot end portion of the coating head with the coating head having the same structure as the extrusion type coating head 10 in FIG. 1 to form the coating layer 2. In doing so, the solvent is sent from a constant flow pump or a pressure tank connected instead of the blower, and the solvent is extruded from the discharge port 8. Then, the uncoated portions on both ends of the coating layer 2 are pushed up by the solvent, so that the coating head does not come into contact with the uncoated portions. Therefore, the uncoated portion is the back edge 4 and the doctor edge 5.
It is possible to prevent the foreign matter adhering to the surface of the web 1 from being scraped off and trapped on both ends of the back edge 4 and the doctor edge 5 of the coating head 10, so that the coating of the coating head 10 can be prevented. The magnetic coating liquid in which the deposits deposited on both ends in the vicinity of the layer 2 push up both ends of the web 1 in the vicinity of the coating layer 2 and are applied to the web 1.
It is possible to prevent uneven application thickness of 15 in the width direction.

The coating thickness of the solvent is set in accordance with the coating thickness of the coating layer 2, and is set by appropriately adjusting the rotation speed of the constant flow pump or the pressure of the pressure tank. Further, since the coating width of the solvent is surely regulated by the spacer 7, the solvent is applied to the web 1
There is no bleeding that penetrates into the coating layer on the front surface or wraps around the back surface of the web.

As the solvent, various solvents such as water or courageous solvent can be used, but the surface tension thereof is preferably 20.
A solvent of ~ 40 dyn / cm is good. Further, in order to avoid mixing of the solvent with the magnetic coating liquid 15, it is desirable that the SP values, which are solubility parameters of the solvents, be separated by 1 or more at 25 ° C. Further, the solvent may contain a certain amount of solid content in order to have a viscosity, in order to reduce the liquid feeding pressure of the solvent and facilitate drying, the viscosity is 50 cp or less, preferably 30 cp or less, More preferably, it should be 10 cp or less.

Further, in the above embodiment, the coating method of the magnetic layer at the time of manufacturing the magnetic recording medium was described, but the coating method of the present invention is not limited to this, and for example, a photosensitive layer at the time of manufacturing a photographic light-sensitive material can be formed. It goes without saying that it can be used in a coating method for coating.

(Effects of the Invention) As described above, in the present invention, the uncoated portions at both ends of the flexible strip-shaped support are prevented from sliding on both end surfaces of the coating head tip portion at least near the coating portion side. The coating liquid is applied while urging both end edges of the flexible belt-like support with a fluid.

Therefore, uncoated portions in the vicinity of the coated portion on both ends of the flexible belt-like support are scraped off by the tip of the coating head,
Since it is possible to prevent foreign substances attached to the surface of the flexible strip-shaped support from being trapped at both ends of the coating head, the deposits deposited on both ends of the coating head become the flexible strip-shaped support. It is possible to prevent both ends of the body from being pushed up to make the coating thickness of the coating liquid applied to the flexible belt-shaped support nonuniform.

Therefore, it was possible to provide a good coating method and apparatus in which a coating layer having a uniform coating thickness and good surface property was formed and the coating liquid did not seep out.

 Hereinafter, examples of the present invention will be described in detail.

(Example) [Example 1] Each component having the composition shown in Table 1 below was put in a ball mill and sufficiently mixed and dispersed, and then an epoxy resin (epoxy equivalent) was used.
The magnetic coating solution prepared by uniformly mixing and dispersing 30 parts by weight of 500) was applied onto a polyethylene terephthalate support having a width of 501,502,506,510 mm and a thickness of 15,38,75 μ: 15,20, The coating was applied at 30,40 cc / m ² , coating speed: 200 m / min, coating tension: 10 kg / 500 mm width, coating width: 500 mm. Therefore, uncoated portions having a width of 0.5, 1, 3, 5 mm on one side are formed at both ends of the coated surface of the support.

The coating apparatus used was an extrusion type coating head 10 as shown in FIG. Here, the shape of the coating head 10 used was that disclosed in JP-A-60-238179, and the radius of curvature r of the curved portion of the doctor edge surface was 5 mm. Further, from the discharge port 8 provided in the coating head 10, pressurized air is supplied at 0.01, 0.1, 0.5, respectively.
It was blown out at 1.0, 3.0, 5.0 kg / cm ² (gauge pressure).

Then, based on the above coating conditions, samples 1 to 16 each of which is a magnetic recording medium having a length of 6000 m are prepared, and the state of adhesion of shavings on both end surfaces of the coating head at the end of coating is observed and coating is started. The amount of change in the coating thickness at the widthwise end of the coating layer at the end of coating was measured. The result is the second
Shown in the table.

Table 1 Composition ・ Co-containing magnetic iron oxide (S _BET 35m ² / g) 100 parts by weight ・ Nitrocellulose 10 parts by weight ・ Polyurethane resin "Nipporan-2304" (manufactured by Nippon Polyurethane Co., Ltd.) 8 parts by weight ・ Polyisocyanate " Coronate L "(manufactured by Nippon Polyurethane Industry Co., Ltd.) 8 parts by weight ・ Cr ₂ O ₃ 2 parts by weight ・ Carbon black (average particle size 20 μm) 2 parts by weight ・ Stearic acid 1 part by weight ・ Butyl stearate 1 part by weight ・ Methyl ethyl ketone 150 Parts by weight: Butyl acetate 150 parts by weight [Comparative Example 1] As a comparative example, the length of each was measured under the same coating conditions as in the above example without blowing pressurized air from the discharge port 8.
Samples 17 to 26, which are 6000 m magnetic recording media, were created, and the state of adhesion of shavings on both end surfaces of the coating head at the end of coating was observed, and the widthwise end of the coating layer at the beginning and end of coating. The amount of change in the coating thickness of each part was measured. Table 2 shows the results.

Example 2 After putting each component having the composition shown in Table 1 above in a ball mill and thoroughly mixing and dispersing, an epoxy resin (epoxy equivalent)
The magnetic coating solution prepared by adding 30 parts by weight of 500) and uniformly mixing and dispersing the same was applied onto a polyethylene terephthalate support having a thickness of 37 μ and a width of 500 mm, coating amount: 17 cc / m ² , coating speed: 200 m
/ Min, coating area tension: 10 kg / 500 mm width, coating width: 490 mm. Therefore, uncoated portions having a width of 5 mm on one side are formed at both ends of the coated surface of the support.

The coating apparatus used was an extrusion type coating head 10 as shown in FIG. Here, the shape of the coating head 10 used was that disclosed in JP-A-60-238179, and the local radius r of the curved portion of the doctor edge surface was 5 mm. Further, the opening width of the discharge port 8 in the coating width direction is at both ends more than the uncoated portion width.
It was set to be smaller by 1 mm.

Then, based on the above coating conditions, samples 27 to 46, which are magnetic recording media having a length of 6000 m, were prepared by changing the type of solvent discharged from the discharge port 8 and the flow rate and viscosity as shown in Table 3 below. At the end of coating, the state of shavings on the uncoated portions at both ends of the support, the bleeding state of the coating liquid, and the state of the interface between the coating liquid and the solvent were observed. The results are shown in Table 3. However, the viscosities of Samples 39 to 46 were adjusted by appropriately adding a vinyl chloride-vinyl acetate copolymer to methyl ethyl ketone.

[Comparative Example 2] As a comparative example, without blowing out the solvent from the discharge port 8,
Comparative Example 2, which is a magnetic recording medium having a length of 6000 m, was prepared under the same coating conditions as in Example 2, and the occurrence of scraping at the uncoated portions at both ends of the support at the end of coating, the bleeding state of the coating liquid, and The interface between the coating liquid and the solvent was observed.
The results are shown in Table 3.

[Comparative Example 3] With a coating apparatus disclosed in Japanese Patent Application Laid-Open No. 57-84771, which comprises an extrusion type head having an unfinished coating head tip, a magnetic material having a length of 6000 m was coated under the same coating conditions as in Example 2. Comparative Example 3, which is a recording medium, was prepared, and the state of occurrence of abrasion at the uncoated portions at both ends of the support, the state of seepage of the coating liquid, and the state of the interface between the coating liquid and the solvent were observed at the end of coating. The results are shown in Table 3.

[Comparative Example 4] Immediately before applying the coating solution to the support disclosed in Japanese Patent Laid-Open No. 61-257268, the uncoated portions on both outer sides of the portions of the support surface to be coated with the coating solution are previously prepared. Comparative Example 4, which is a magnetic recording medium having a length of 6000 m, was prepared under the same coating conditions as in Example 2 by a coating method of coating a solvent.
At the end of coating, the occurrence of abrasion on the uncoated portions on both ends of the support, the bleeding state of the coating solution, and the interface state between the coating solution and the solvent were observed. The results are shown in Table 3.

[Comparative Example 5] A coating apparatus having a length of 6000 m under the same coating conditions as in Example 2 was prepared by using a coating apparatus composed of an extrusion type head disclosed in Japanese Patent Application Laid-Open No. 61-257263, in which the apex angle of the doctor edge was chamfered. Comparative Example 3 which is a magnetic recording medium was prepared, and the state of occurrence of abrasion at the uncoated portions on both ends of the support, the state of seepage of the coating liquid, and the state of the interface between the coating liquid and the solvent were observed at the end of coating. The results are shown in Table 3.

As is clear from Table 3, in Samples 27 to 46, which are examples using the coating apparatus based on the coating method of the present invention, in comparison with Comparative Examples 2 to 5 using the conventional coating apparatus, uncoated Of the coating layer and the thick coating of the end portion on the coating layer side corresponding to the average thickness of the coating layer were improved, and no troubles due to solvent bleeding occurred.

[Brief description of drawings]

FIG. 1 is a partial 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 cross section of the extrusion type coating head shown in FIG. 1, and FIG. It is a partial expanded sectional view showing the coating state of the coating layer on a strip | belt-shaped support body. (Symbols in the figure) 1 ... Flexible strip-shaped support 2 ... Coating surface 3 ... Slot 4 ... Back edge 5 ... Doctor edge 6 ... Regulating plate 7 ... Spacer 8 ... Discharge port 9 ... Coating liquid supply port 10 ... Extrusion type coating head 11 ... Side plate, 12 ... Pressurized air supply port 13 ... Liquid pool, 15 ... Magnetic coating liquid.

Claims (1)

[Claims] 1. A coating device for coating a coating liquid while pressing a slot tip portion of a coating head against the surface of a continuously running flexible strip-shaped support, wherein the both ends of the flexible strip-shaped support are uncoated. Discharge ports for discharging a pressurized fluid toward both ends of the flexible strip-shaped support are provided at both ends of the application head, and the pressurized fluid spouted from the discharge port is the flexible strip-shaped support. By interposing between both end portions of the coating head and both end portions of the coating head tip end portion, contact between the both end uncoated portions of the flexible strip-shaped support and the both end portions of the coating head tip portion is avoided. A coating device characterized by the above.