JP2003170112A - Coating method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To recycle a scraped coating liquid without applying liquid preparation or filtration with the features of a scraping suitable for obtaining a thin uniform coating film layer. <P>SOLUTION: Two slits of a coating slit 30 and a recovering slit 32 are provided in a coating head 16. Excessive coating liquid applied on a web 12 by discharging the coating liquid excessively from the coating slit is scraped by the recovering slit 32 to be recycled. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating method and apparatus, and more particularly to improvement of a coating method and apparatus used for manufacturing photographic light-sensitive materials and magnetic recording media.

[0002]

2. Description of the Related Art A photographic light-sensitive material and a magnetic recording medium are subjected to a coating process in which a predetermined coating liquid such as a magnetic liquid is coated on a continuously running strip-shaped support (hereinafter referred to as "web") to form a coating film. Manufactured. In particular, magnetic recording media such as magnetic recording tapes have rapidly improved in capacity and recording density for broadcasting and computers in recent years, and it is possible to obtain a magnetic layer having an extremely thin film thickness and a smooth surface. Coating technology is required.

As a coating device for coating the coating liquid on the web surface, for example, roll coater type, gravure coat type, roll coat plus doctor type, extrusion type,
Although there are slide coat types and the like, in recent years, extrusion type coaters have been widely used for coating the magnetic coating liquid.

Among the extrusion type coating devices, as described in JP-A-58-109162, a method of pressing the tip of the coating head against the web is
It is widely used in the field of magnetic recording medium manufacturing because the air entrained in the web can be eliminated by increasing the liquid pressure at the tip of the coating head using the web tension, and a thin and uniform coating layer can be obtained. Has been done. However, even when a single layer coating is carried out using this type of coating head, the coating thickness is limited.

As a method for forming a thinner coating layer, as described in Japanese Patent Application Laid-Open No. 7-287843, a web pressing type extrusion coating apparatus is used to coat an excessive amount of the web and then the extrusion coating apparatus. There is a scraping type blade capable of forming a very thin coating layer by scraping off an excessive amount with a blade arranged on the downstream side of. In this case, the means for applying the excessive amount is not limited to the pressing type extrusion coating device, and a roll coater type, a gravure slide coater, an extrusion coater with a backup, or the like can be used.

[0006]

However, in the case of the scraping type, as can be seen from FIG. 7, the coating is applied to the web 5 excessively by the coating head 3 and the excess amount is scraped off by the blade 6 and recovered. Since the liquid once contacts the atmosphere, the solvent in the coating liquid volatilizes and the liquid properties such as viscosity and solid content concentration change. If the coating liquid having a changed viscosity is reused as it is, the amount of the liquid scraped off by the blade 6 or the final thickness of the coating film after the blade 6 is adversely affected. It has a drawback that it cannot be reused until the physical property is adjusted. Further, since the coating liquid recovery line is open to the atmosphere, dust from the outside of the recovery line is easily mixed. Therefore, the recovered liquid is used as the coating liquid supply tank 1.
From the filter 9 when the liquid is sent from the pump 2 to the coating head 3.
There is a drawback that dust cannot be removed sufficiently even if it is filtered with.

The present invention has been made in view of the above circumstances, and prepares a scraped coating solution while maintaining the characteristics of a scraped type suitable for obtaining a uniform and extremely thin coating film layer. It is an object of the present invention to provide a coating method and apparatus that can be reused without liquid treatment or filtration treatment.

[0008]

In order to achieve the above-mentioned object, the first aspect of the present invention is to apply a desired coating to one side of a continuously running strip-shaped support by using a precoating means. A method for precoating a coating solution in excess of the thickness and then scraping off an excess of the coating solution by a scraping means provided on the downstream side of the precoating means when viewed from the support running direction, wherein It is characterized in that the coating liquid coated on the support is not exposed to the atmosphere during the period from the coating of the coating liquid on the substrate to the scraping off of the excess of the coating liquid.

According to the coating method of the first aspect of the present invention, the coating solution is applied to the continuously running strip-shaped support in an amount exceeding the desired coating thickness, and the excess amount of the coating solution is scraped off. Since the coating liquid applied to the support was prevented from being exposed to the atmosphere, it is possible to prepare the scraped coating liquid while maintaining the characteristics of the scraped type suitable for obtaining a uniform ultra-thin coating film layer. It can be reused without liquid treatment or filtration treatment.

Here, "the coating liquid applied to the support is not exposed to the atmosphere" means that the coated surface of the support applied with the coating liquid is at least not exposed to the atmosphere. It does not matter whether or not the end in the body width direction is open to the atmosphere.

A second aspect of the present invention is based on the first aspect.
The scraped off coating liquid is collected through a closed system recovery line, and the collected coating liquid is reused. By making the recovery line closed, the viscosity and solids of the reused coating liquid It is possible to prevent the physical properties of the liquid, such as the concentration, from changing further, and to prevent dust and the like from entering.

According to a third aspect of the present invention, a desired coating thickness is obtained by adjusting at least one of the precoat liquid amount for precoating and the scraping liquid amount to be scraped off. Like this,
A desired coating thickness can be easily obtained.

A fourth aspect of the present invention is based on the third aspect.
The amount of precoat liquid and the amount of the scraping liquid are measured by a flow meter, and at least one of the amount of the precoat liquid and the amount of the scraping liquid is adjusted so that the flow rate difference has a desired coating thickness. A desired thickness can be obtained well.

According to a fifth aspect of the present invention, the traveling speed (coating speed) of the support is adjusted to obtain a desired coating thickness in the first or second aspect. The coating thickness can be changed by adjusting the speed.

A sixth aspect of the present invention is the first, second or fifth aspect.
In the above, the viscosity of the coating liquid is adjusted to obtain a desired coating thickness, and the coating thickness can be changed by adjusting the viscosity of the coating liquid. In this case, an aspect in which the speed adjustment of the coating speed is combined with the viscosity adjustment of the coating liquid is also included.

According to a seventh aspect of the present invention, the solid content concentration of the coating solution is adjusted to obtain a desired coating thickness according to the first, second, fifth or sixth aspect. The coating thickness can be changed by changing. In this case, an aspect in which at least one of the speed adjustment of the coating speed and the viscosity adjustment of the coating liquid is combined with the solid content concentration adjustment of the coating liquid is also included.

According to an eighth aspect of the present invention, the flow resistance of the recovery line is adjusted to obtain a desired coating thickness in the first, fifth, sixth or seventh aspect, and the flow resistance of the recovery line is changed. Therefore, the coating thickness can be changed. In this case, a mode in which at least one of the speed adjustment of the coating speed, the viscosity adjustment of the coating liquid, and the solid content concentration adjustment of the coating liquid is combined with the flow resistance adjustment of the recovery line is also included.

A ninth aspect of the present invention is the support body according to any one of the first to eighth aspects, wherein the scraping means is configured such that the scraping portion of the scraping means and the support body are relatively pressed. It is configured such that the excess amount of the coating liquid is scraped off by the scraping means by pressurizing the coating liquid applied to the device, and the desired coating thickness is obtained by adjusting the pressure applied. Is. In this case, the liquid for adjusting at least one of the liquid resistance of the recovery line, the solid content concentration of the coating liquid, the viscosity of the coating liquid, the amount of the precoat liquid and the amount of the scraping liquid, for adjusting the pressure of the coating liquid. A mode in which at least one of the amount adjustment and the speed adjustment for adjusting the traveling speed of the belt-shaped support is combined is also included.

A tenth aspect of the present invention shows one mode of the pressurizing method and the pressing force adjusting method in the ninth aspect.
The support is wrapped around the scraping portion to obtain a pressing force, and the pressing force is adjusted by adjusting the tension in the traveling direction of the support.

An eleventh aspect of the present invention shows another aspect of the pressurizing method and the pressing force adjusting method in the ninth aspect, in which the support is opposed to the scraping portion and the coating liquid of the support is not applied. A backup roller is arranged on the back side of the body to obtain a pressing force, and the pressing force is adjusted by adjusting the clearance between the scraping portion and the backup roller.

A twelfth aspect of the present invention shows still another aspect of the pressurizing method and the pressing force adjusting method according to the ninth aspect, in which the coating liquid of the support is not applied facing the scraping portion. An elastic backup roller is arranged on the back side of the support to obtain a pressing force, and the pressing force is adjusted by adjusting at least one of the longitudinal elastic modulus and the hardness of the backup roller.

A thirteenth aspect of the present invention shows still another aspect of the pressurizing method and the pressing force adjusting method according to the ninth aspect, in which the coating liquid of the support is not applied so as to face the scraping portion. A spraying means for spraying a fluid is arranged on the back surface side of the support to obtain a pressing force, and the pressing pressure of the spraying means is adjusted to adjust the pressing force.

According to a fourteenth aspect of the present invention, in any one of the first to thirteenth aspects, a magnetic coating material in which magnetic particles are dispersed is used as a coating liquid, and the coating method of the present invention has a viscosity of the coating liquid. It is extremely effective for magnetic paints that require precision in the properties of coating liquids such as adjustment and adjustment of solid content concentration.

In order to achieve the above-mentioned object, the fifteenth aspect of the present invention is, on one side of a continuously running strip-shaped support, provided with an excess of a desired coating thickness finally obtained by using a precoating means. After pre-coating an amount of the coating liquid, a coating device that scrapes off an excessive amount of the coating liquid by a scraping unit provided on the downstream side of the pre-coating unit when viewed from the support running direction, wherein the coating liquid is applied to the support. It is characterized in that an atmosphere release preventing mechanism is provided for preventing the coating solution applied to the support from being exposed to the atmosphere between the application and the scraping off of the excess of the coating solution.

According to the coating apparatus of claim 15 of the present invention,
The coating liquid applied to the support is released to the atmosphere between the time when the excess amount of the coating liquid is applied to the continuously running strip-shaped support and the excess amount of the coating liquid is scraped off. Since a mechanism to prevent atmospheric release is provided,
It is possible to reuse the scraped-off coating liquid without preparing and filtering the scraped coating liquid while maintaining the features of the scraped type suitable for obtaining a uniform and extremely thin coating film layer.

A sixteenth aspect of the present invention relates to an aspect of the atmosphere release preventing mechanism according to the fifteenth aspect, wherein the atmosphere release preventing mechanism integrally includes a precoat portion of the precoat means and a scraping portion of the scraping means. It is formed by bringing the lip surface of the coating head and the support close to each other, and the precoat portion is provided on the upstream side in the running direction of the support of the coating head and the dropping portion is provided on the downstream side. As a result, the excess coating liquid applied in the precoat portion moves to the scraping portion while being sandwiched between the support and the lip surface, and is scraped off. The coating solution applied to the body is never exposed to the atmosphere.

According to a seventeenth aspect of the present invention, in the sixteenth aspect, the precoat portion is provided with a coating slit for discharging the coating liquid, and the scraping portion is provided with a collecting slit for collecting the scraped coating liquid. Since it is provided, all the paths of the precoating means and the scraping means can be made a closed system.

The claim 18 of the present invention is the claim 16 or 1.
7, the coating liquid applied to the support by wrapping the support on the lip surface with a pair of guide rollers provided on the upstream side and the downstream side of the coating head and adjusting the tension in the running direction of the support. Is applied to obtain a desired coating thickness.

The nineteenth aspect of the present invention is the sixteenth aspect or the first aspect.
In 7, the backup liquid is applied to the support by arranging a backup roller on the back side of the support facing the lip surface of the coating head, where the coating liquid is not applied, and adjusting the clearance between the lip surface and the backup roller. Is applied to obtain a desired coating thickness.

The twentieth aspect of the present invention includes the seventeenth to nineteenth aspects.
In any one of the above, the coating slit is connected to the supply line of the coating liquid to be precoated, the recovery slit is connected to the recovery line of the scraped coating liquid, and the supply line and the recovery line are connected to each other. A flowmeter was provided to measure the amount of precoat liquid and the amount of scraped liquid with a flowmeter, and a flowrate control means was provided to control the flowrate of at least one of the supply line and the recovery line so that the difference in flowrate would be the desired coating thickness. It is a thing. This makes it possible to accurately control the desired amount of coating applied to the support.

The twenty-first aspect of the present invention includes the sixteenth to twentieth aspects.
In any one of 1, the shape of the doctor lip surface of the lip surface of the coating head between the time when the coating liquid is applied and the time when the excess amount of the coating liquid is scraped off, and The shape of the recovery lip surface has an arcuate curved surface that is convex toward the support, two or more continuous flat surfaces that are convex toward the support, or a combination surface of an arcuate curved surface and a flat surface that is convex toward the support. Therefore, the liquid pressure of the coating liquid on the lip surface of the coating head can be increased. Thereby, the air entrained in the support can be eliminated and a thin and uniform coating layer can be obtained.

[0032] Claim 22 of the present invention, in claim 21, the radius of curvature of the doctor lip surface and R _2, the radius of curvature of the recovery lip surface when the R _3, such that the R _2> R ₃ I chose As a result, the pressure generated on the collecting lip surface becomes high, so that the coating liquid is easily scraped off.

The twenty-third aspect of the present invention includes the sixteenth to twentieth aspects.
In any one of the above, since the scraping portion is provided with a rotary rod that comes into contact with the coating surface of the support to scrape off the coating liquid, when a foreign substance is trapped between the rotary rod and the support. Foreign matter is easily removed. Therefore, it is possible to reduce streak failures due to foreign matter.

A twenty-fourth aspect of the present invention shows another aspect of the atmosphere release preventing mechanism according to the fifteenth aspect, wherein the atmosphere release preventing mechanism includes a precoat portion of the precoat means and a scraping portion of the scraping means. It is configured as a separate body, and is provided with a cover member that covers at least the coating surface of the support body along the traveling path of the support body between the precoat portion and the scraping portion. As a result, the coating liquid applied to the support in the precoat section moves to the scraping section while being sandwiched between the support and the cover member, and the excess coating solution is scraped off in the scraping section. The coating liquid applied to the support is not exposed to the atmosphere during the period from the scraping to the scraping. Therefore, even when the precoat part of the precoat means and the scraping part of the scraping means are provided separately, it is possible to prevent the coating liquid applied to the support from being exposed to the atmosphere.

A twenty-fifth aspect of the present invention is that, in the twenty-fourth aspect, the precoat portion has a slit for coating, and
The scraping unit has a recovery slit, and one backup roller is provided so as to face both the precoating unit and the scraping unit. As a result, even if the precoat section and the scraping section are separate bodies, the backup roller and the guide member can be configured as if they were integrated, so that all paths of the precoating section and the scraping section can be provided. It becomes possible to make a closed system.

The twenty-sixth aspect of the present invention is the twenty-fifth to the twenty-fifth aspects.
In any one of the above, a magnetic coating material in which magnetic particles are dispersed is used as a coating liquid, and the coating apparatus of the present invention is a magnetic material that requires precision in coating liquid properties such as viscosity adjustment and solid content concentration adjustment. It is extremely effective in paints.

The support used in the present invention is as follows.
Also included are those which have been previously coated with an undercoat layer and solidified.

[0038]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of a coating method and apparatus according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a conceptual diagram for explaining the overall construction of the coating apparatus of the present invention, in which the precoat section 39 of the precoat means 31 and the scraping section 41 of the scraping means 33 are integrated with the coating head 16. This is an example of the case. If the integrated coating head 16 is intentionally divided into a precoat portion 39 and a scraping portion 41, it is divided by a broken line 17 shown in the coating head 16.

As shown in FIG. 1, the coating device 10 mainly includes a guide roller 14 for guiding the traveling of the web 12.
The coating head 16, the precoating unit 31, the scraping unit 33, and the controller 22 for controlling the precoating unit 31 and the scraping unit 33. The coating head 16 has a lip surface 24 at the tip of the coating head.
Are arranged so as to face the web 12 that continuously runs.

The precoat means 31 mainly comprises a precoat part 39 formed on the coating head 16 and the web 12.
Excessive coating amount than the coating amount applied to the precoat part 3
9 and a supply line 18 for supplying the same. On the other hand, the scraping means 33 is composed of a scraping section 41 formed on the coating head 16 and a collecting line 20 for collecting an excessive amount of the coating liquid scraped by the scraping section 41.

As shown in FIGS. 1 and 2, the coating head 1
6 includes a coating pocket portion 26 and a collecting pocket portion 2
A pair of cylindrical pockets 26 and 28 formed with 8 are formed parallel to the web width direction. Further, in the coating head 16, a coating slit 30 having a discharge port 30A on the lip surface 24 and a recovery port 32A on the lip surface 24 downstream of the discharge port 30A in the running direction of the web 12 are collected. The application slit 30 is formed, the application slit 30 is communicated with the application pocket portion 26, and the recovery slit 32 is communicated with the recovery pocket portion 28. As a result, the precoat portion 39 and the scraping portion 41 are integrally formed on the coating head 16. Then, the coating pocket portion 26 is connected to the supply line 18, and the collection pocket portion 2
8 is connected to the recovery line 20. Coating slit 30
And the recovery slit 32 is provided in each pocket 2
It is a narrow flow path that connects 6, 28 and the lip surface 24, and extends in the width direction of the web 12. Then, an excess amount of the coating liquid to be applied to the web 12 is supplied from the supply line 18 to the coating pocket portion 26 of the coating head 16, and the coating liquid recovered from the recovery slit 32 to the recovery pocket portion 28. The excess liquid is discharged to the recovery line 20. In addition, in FIG. 2, as a method of feeding the coating solution to the coating pocket portion 26, the coating liquid is supplied from one side of the coating pocket portion 26.
6 is supplied from one side and pulled out from the other side, or is supplied from the central portion of the coating pocket portion 26 and divided into both sides, and any one may be applied.

As shown in FIG. 1, the supply line 18 is connected to the coating liquid tank 36 and the coating pocket 26 of the coating head 16 by the supply pipe 34, and the supply pipe 3 is provided.
In the middle of 4, a supply pump 38 for varying the amount of the coating liquid supplied to the coating pocket portion 26 and a supply flow meter 40 for measuring the amount of the coating liquid flowing through the supply pipe 34 are provided.

On the other hand, in the recovery line 20, the recovery pipe 42 connects the recovery pocket portion 28 and the coating liquid tank 36, and the recovery line 20 is provided in the middle of the recovery pipe 42.
A valve 44 for varying the amount of coating liquid recovered from the recovery pocket portion 28 by changing the flow resistance of No. 2 and a recovery amount meter 46 for measuring the amount of coating liquid flowing through the recovery pipe 42 are provided. As a result, closed supply / recovery lines 18 and 20 that are not exposed to the atmosphere are formed between the coating head 16 and the coating liquid tank 36.

A pair of guide rollers 14 are provided on the upstream side and the downstream side of the coating head 16 in the web traveling direction, and are arranged at a position lower than the tip of the coating head 16. As a result, the continuously running web 12 is wrapped around the lip surface 24 of the coating head 16, and
It is approached so as to be pressed to the 4 side. As a result, the coating liquid sandwiched between the web 12 and the lip surface 24 is pressurized. The pair of guide rollers 14 and 14 are slidably provided in the sliding directions 48 and 48 in FIG. 1, whereby the tension in the traveling direction of the web 12 can be changed. The slide mechanism of the guide rollers 14 and 14 may be any mechanism as long as it can slide minutely. For example, a mechanism of a feed screw can be used. By changing the tension in the running direction of the web 12, the pressing force with which the web 12 presses the lip surface 24 of the coating head 16 changes, and the pressing force applied to the coating liquid sandwiched between the web 12 and the lip surface 24 changes. Since it changes, the amount of scraping liquid in the scraping unit 41 changes. Thereby, a desired coating thickness can be obtained.
As described above, the scraping means 33 of the present invention is configured such that the lip surface 24 of the coating head 16 and the web 12 are relatively pressed to pressurize the coating liquid applied to the web 12 to collect the slits for recovery. It is configured to scrape off an excessive amount of the coating liquid by utilizing the edge portion of the collecting port 32A of 32 and the lip surface 56 for collection, and the scraped coating liquid is collected by the collecting line 20. In this case, as shown in FIG. 3, of the lip surface 24 of the coating head 16, the shape of the doctor lip surface 54 between the coating slit 30 and the collecting slit 32 and the shape of the collecting slit 32 when viewed from the web running direction. The shape of the downstream collecting lip surface 56 is
It is preferable that the web 12 has a convex arcuate curved surface. Although not shown, other than the curved surface, two or more planes that are continuous and convex toward the web 12 side, or the web 1
You may make it have the combination surface of the circular arc curved surface and the plane which are convex on the 2 side. Thereby, the air entrained in the web 12 can be eliminated and a thin and uniform coating layer can be obtained. Furthermore, the radius of curvature of the doctor lip surface 54 is R
_{When the} radius of curvature of the recovery lip surface 56 is R ₃ , R ₂ > R ₃ is preferably satisfied. As a result, the pressure generated on the recovery lip surface 56 is higher than the pressure generated on the doctor lip surface 54, so that the coating liquid is easily scraped off. The material of each block on which the doctor lip surface 54 and the recovery lip surface 56 are formed is a hard body such as superalloy, fine ceramics, alumina A-150, zirconia, or the surface of the block is covered with these materials. The surface is processed to have a roughness of R _max of 0.5 μm or less, preferably 0.2 μm or less.

The controller 22 includes a flow rate meter 40 for supply.
Also, the measured values of the coating liquid supply amount and the coating liquid recovery amount measured by the recovery amount flowmeter 46 are input. Also, the controller 2
In 2, the difference between the supply amount of the coating liquid and the recovered amount of the coating liquid is calculated to determine whether or not the desired amount of the coating liquid to be applied to the web 12 is matched. At least one of the pump 38 and the valve 44 is controlled.

Next, the operation of the coating apparatus 10 configured as described above will be described.

Excessive coating liquid supplied from the coating liquid tank 36 through the supply pipe 34 by the supply pump 38 to the coating pocket 26 of the coating head 16 rises up the coating slit 30 and is discharged from the discharge port 30A. At the same time, the amount of coating liquid flowing through the supply pipe 34 is measured by the supply flow rate meter 40 and output to the controller 22. The coating liquid excessively discharged from the discharge port 30A is the lip surface 24 of the coating head 16 and the web 1 that travels in the vicinity of the lip surface 24.
It is applied to the web 12 while forming the beads 50 between the two. That is, an excessive amount of the coating liquid is applied to the web 12 in a state where the discharging force of the coating liquid discharged from the discharge port 30A and the pressing force of the web 12 pressing the lip surface 24 of the coating head 16 are balanced. On the other hand, at the recovery port 32A of the recovery slit 32 formed on the lip surface 24 on the downstream side of the discharge port 30A in the web traveling direction, the excess amount of the coating liquid is scraped off into the recovery slit 32. That is, the coating liquid thickly applied to the web 12 at the discharge port 30 </ b> A of the coating slit 30 is entrained in the web 12 and is collected in the recovery slit 32.
Part of the thick coating, that is, an excessive amount of the coating liquid, is scraped off at the edge portion of the recovery port 32A and a recovery lip surface 56 described later. As a result, the coating liquid in a thick coating state on the web 12 is distributed to the coating liquid flowing in the recovery slit 32 and the coating liquid reduced to a desired coating amount and subsequently entrained in the web 12. The coating liquid distributed in the collecting slit 32 is collected in the collecting pocket 2
8. The flow of the coating liquid reaching the coating liquid tank 36 via the collecting line 20 is formed and collected in the coating liquid tank 36.
In addition, the amount of the coating liquid flowing through the recovery pipe 42 is the recovery amount flow meter 4
6 is measured and output to the controller 22.

In this coating / recovering operation, the controller 22 causes the difference between the coating liquid supply amount measured by the supply flow rate meter 40 and the coating liquid recovery amount measured by the recovery flow meter 46 to be subtracted from the web 12. At least one of the rotation speed of the supply pump 38 and the opening degree of the valve 44 is controlled so that the desired amount of coating liquid to be applied matches. Although not shown in FIG. 1, the controller 22 and the slide mechanism of the guide roller 14 are connected to each other by a signal cable or wirelessly.
Alternatively, the slide of the guide roller 14 may be automatically controlled. In this case, the slide amounts of the pair of guide rollers 14 and 14 do not have to be the same amount, and the pressing force of the web 12 against the recovery lip surface 56 is stronger than that of the doctor lip surface 54, so that the web 12 and the recovery roller 12 are recovered. A large pressure may be applied to the coating liquid sandwiched between the application lip surfaces 56, whereby the amount of the scraping liquid may be changed to obtain a desired coating thickness. Further, the controller 22 determines all of the rotation speed of the supply pump 38, the opening degree of the valve 44, and the sliding amount of the pair of guide rollers 14 and 14 based on the measured values of the supply flow rate meter 40 and the recovery flow rate meter 46. It may be controlled to obtain a desired coating thickness. Further, a desired coating thickness may be obtained by adjusting the traveling speed of the web 12, that is, the coating speed. Further, a desired coating thickness may be obtained by adjusting the viscosity and solid content concentration of the coating liquid. Furthermore, the desired coating thickness may be obtained by adjusting the flow resistance of the recovery line 20. For example, the flow resistance can be adjusted by adjusting the opening degree of the valve 44 provided in the recovery line 20. Furthermore, the coating speed, the viscosity of the coating liquid, the solid content concentration, and the flow resistance may be combined.

In FIG. 1, the pair of guide rollers 14 adjust the tension in the running direction of the web 12 to adjust the pressure applied to the coating liquid sandwiched between the web 12 and the lip surface 24 of the coating head 16. However, FIG. 4 shows another mode in which a pressure is applied to the coating liquid applied to the web 12. That is,
This is a case where the backup roller 60 is arranged so as to face the coating head 16 and to the back surface side of the web 12 to which the coating liquid is not coated. The adjustment of the pressing force is performed by sliding the backup roller 60 with respect to the coating head 16 so as to move back and forth to change the clearance between the coating head 16 and the backup roller 60. The slide mechanism of the backup roller 60 may be any mechanism as long as it can slide minutely, but for example, a mechanism of a feed screw can be preferably used. in this case,
The backup roller may be formed of an elastic body and the pressing force may be adjusted by changing at least one of the longitudinal elastic modulus and the hardness of the backup roller. Further, although not shown, a spraying means for spraying a fluid is arranged on the back surface side of the web 12 on which the coating liquid of the web 12 is not applied so as to obtain a pressurizing force while facing the coating head 16. The pressing force may be changed by adjusting.

In FIG. 3, the coating liquid is scraped off by forming the doctor lip surface 54 and the recovery lip surface 56 of the lip surface 24 of the coating head 16 into an arcuate curved surface convex toward the web side. Although the example has been described in which the coating liquid is easily removed, as shown in FIG. 5, the coating liquid is easily scraped off by providing the rotary rod 62 at the end of the recovery lip surface 56 on the recovery slit 32 side. You may The rotating rod 62 may rotate in the same direction or in the reverse direction with respect to the traveling direction of the web 12, but the reverse rotation is more preferable.

As described above, in the above-described embodiment, the coating head 16 has the coating slit 30 and the collecting slit 3.
Two slits No. 2 are provided, and an excessive amount of the coating liquid applied to the web 12 by being excessively discharged from the coating slit 30 is scraped off by the collecting slit 32 and collected.
Thereby, until the excess of the coating liquid discharged from the coating slit 30 is collected by the collecting slit 32,
Since the coating liquid is sandwiched between the lip surface 24 of the coating head 16 and the web 12 and placed in a sandwich state, it is possible to form a closed system that does not come into contact with the atmosphere between the coating and the scraping, which has been difficult in the past. can do. Further, as described above, the coating head 16 and the coating liquid tank 3
Since the supply / recovery lines 18 and 20 of the closed system which are not exposed to the atmosphere are also formed between the line 6 and 6, the coating apparatus 10 as a whole can be formed as a closed system line. As a result, the recovered coating liquid is less likely to come into contact with the atmosphere, and the solvent in the coating liquid does not volatilize and the liquid properties such as viscosity and solid content concentration do not change. Further, it becomes difficult for dust and the like to enter the coating liquid from the outside of the recovery line.

Moreover, the recovery port 32 of the recovery slit 32
Since the edge portion of A and the recovery lip surface 56 on the downstream side of the recovery slit 32 serve as a scraping surface of a conventional blade, a scraping type suitable for obtaining a uniform ultra-thin coating film layer. While maintaining the features of the extrusion type, the scraped off coating liquid can be reused without preparation or filtration. Therefore, the coating apparatus 10 of the present invention is suitable as a coating apparatus for obtaining the uniform ultrathin magnetic layer required in the manufacture of magnetic recording media, and the wet thickness of the magnetic coating liquid applied to the web 12 is 5 μm. The following are preferred. More preferably, it is particularly suitable for an extremely thin coating having a wet thickness of 2 μm or less.

A preferable coating condition is a coating speed of 5
0 to 600 m / min, more preferably 50 to 300 m / min, and the final thickness (dry thickness) of the magnetic coating liquid is 0.5.
It is less than or equal to μm, and more preferably less than or equal to 0.2 μm. The liquid viscosity is 1 Pa · s at 100 (1 / sec).
(10 poise) or less, more preferably 0.2 Pa · s
(2 poise) or less, the viscosity at 40,000 (1 / sec) is 0.01 Pa · s (10 centipoise) or less,
More preferably 0.005 Pa · s (5 centipoise)
It is the following.

FIG. 6 is a conceptual diagram for explaining another aspect of the coating apparatus of the present invention, in which the precoat portion 39 of the precoat means 31 and the scraping portion 41 of the scraping means 33 are separated from each other. This is the case.

As shown in FIG. 6, the coating device 65 runs while the web 12 is supported by one large-diameter backup roller 66, and comes close to the peripheral surface of the backup roller 66 and is scraped off from the precoat portion 39. The part 41 is disposed separately. The precoat portion 39 and the scraping portion 41 have the same pocket 2 for coating as the coating device 10 of FIG.
6, the recovery pocket portion 28, the coating slit 30, and the recovery slit 32 are formed. And the precoat part 3
An arc-shaped cover plate 68 is provided along the web traveling path between the scraping portion 41 and the scraping portion 41, that is, along the circumferential surface of the backup roller 66. The supply line 18 and the recovery line 20 are the same as those described with reference to FIG.
It is composed of a closed supply line 18 and a recovery line 20.

According to the coating device 65 thus constructed, the coating liquid excessively coated on the web 12 from the coating slit 30 of the precoat portion 39 is sandwiched between the web 12 and the cover plate 68 and sandwiched. Scraping part 4
1 and the excess of the coating liquid is scraped off in the recovery slit 32 by the scraping unit 41. Thus, FIG.
Also in the case of the coating device 65, the coating liquid can be prevented from coming into contact with the atmosphere between the coating and the scraping, as in the coating device 10 of FIG. In this case, if the clearance between the web 12 and the cover plate 68 is too large, an air layer is formed between the coating liquid and the cover plate 68, and the solvent easily volatilizes from the coating liquid. Therefore, it is preferable that the thickness is equivalent to the coating thickness of the excess coating liquid applied to the web 12. However, it is essential that the clearance be larger than the coating thickness to be finally obtained.

In this embodiment, the precoat portion 39
The example of the extrusion coater type having the coating slit 30 in the above has been described, but as shown in FIG.
When the scraping unit 41 and the scraping unit 41 are separate units, various coating machines such as a roll coater type, a gravure coat type, and a bar coater type can be used. Further, for the scraping unit 41, for example, a doctor blade, a scraping rod or the like can be used. The point is that the excess coating liquid applied to the web 12 should not be exposed to the atmosphere until it is scraped off. Further, in FIG. 6, the excess coating liquid is scraped off by the edge portion of the collecting slit 32 of the scraping portion 41 and the collecting lip surface 56, but the scraping portion 41 is provided with the rotating rod 62 described in FIG. You may do it.

[0059]

EXAMPLE A test for obtaining a product having a thin coating thickness was conducted by using an integral type coating apparatus in which a precoat section and a scraping section shown in FIG. 1 are integrally provided on a coating head.
Further, the coating thickness when the coating liquid collected in the scraping section was reused as the coating liquid without performing the preparation process or the filtration process was examined. (Coating liquids used in the test) Five types of coating liquids (A, B, C, D, E) having different viscosities and solid content concentrations shown in Table 2 based on the liquid formulations of the coating liquids shown in Table 1 Was prepared and used. (Test conditions) A coating head having a coating width of 1000 mm, a coating slit gap of 0.2 mm, and a collecting slit gap of 0.5 mm is used, and the web has a thickness of 15 μm.
An ET (polyethylene terephthalate) film was used.

Then, the test groups of Tests 1 to 11 were carried out by changing four kinds of factors such as the type of the coating liquid, the coating speed, the pressure applied to the coating liquid at the scraping portion, and the flow resistance of the recovery line. The coating thicknesses obtained in step 1 were compared. Further, in Test 1, the coating thickness when the recovered coating liquid was reused without being subjected to the preparation treatment or the filtration treatment was examined.

The coating speed was changed in the range of 50 to 200 m / min, and the flow resistance of the recovery line was changed by providing a valve in the recovery line and adjusting the opening of the valve. The pressure of the coating liquid was changed by changing the tension in the web running direction within the range of 7 to 30 kgf / m.

[0062]

[Table 1]

[0063]

[Table 2] The test results are shown in Table 3.

[0064]

[Table 3] From the results of Table 3, as can be seen from the comparison of tests 1 to 5 in which only the factor of the coating liquid is changed and other factors are made common, the coating thickness can be changed by changing the type of the coating liquid. As can be seen from tests 3, 6 and 7 in which only the coating speed is changed and other factors are common, the coating thickness can be changed by changing the coating speed, and the coating thickness increases as the coating speed increases. Get thicker. Change only the tension,
As can be seen from tests 3, 8, 9, and 10 in which other factors are common, the coating thickness can be changed by changing the tension, and as the tension is increased, the coating thickness becomes thinner.
As can be seen from the tests 10 and 11 in which only the flow resistance was changed and other factors were made common, the application thickness can be changed by changing the flow resistance, and the application thickness increases as the flow resistance increases. .

In this way, the type of coating liquid (viscosity, solid content concentration), the coating speed, the pressure applied to the coating liquid at the scraping portion (web tension), and the flow resistance (valve opening) of the recovery line are controlled. Thus, the finally obtained coating thickness can be changed.

Further, in Test 1, even when the coating liquid recovered from the scraping section is reused by the precoat means without performing the preparation process or the filtration process, the coating thickness is the same as in Test 1 and dust There was no mixture.

This result shows that by using the coating method and apparatus of the present invention, the scraped coating liquid can be prepared while maintaining the characteristics of the scraped type suitable for obtaining a uniform and extremely thin coating film layer. It means that it can be reused without liquid treatment or filtration treatment.

In the present embodiment, the coating device of FIG. 1 was used as an example, but in the case of the coating device of FIG. 4 in which the integral coating head and the backup roller are combined, the scraping portion of FIG. When the rotary rod is provided, similar results can be obtained even in the case of the coating device in which the precoat portion and the scraping portion are separate bodies and the backup roller in FIG.

[0069]

EFFECTS OF THE INVENTION According to the coating method and apparatus of the present invention, the scraped coating liquid can be prepared and treated while maintaining the characteristics of the scraped type suitable for obtaining a uniform and extremely thin coating film layer. It can be reused without filtering.

Therefore, the coating method and apparatus of the present invention are suitable as a coating apparatus for obtaining a uniform ultrathin magnetic layer required for the production of magnetic recording media, and the magnetic coating solution coated on a support can be used. It is particularly suitable for an extremely thin coating having a wet thickness of 2 μm or less.

[Brief description of drawings]

FIG. 1 is a conceptual diagram illustrating a coating apparatus of the present invention, showing a case where a precoat portion of precoating means and a scraping portion of scraping means are integrated with a coating head.

2 is a perspective view with a part cut away for explaining the structure of the coating head of FIG. 1. FIG.

3 is a cross-sectional view illustrating a lip surface of the coating head of FIG.

FIG. 4 is a conceptual diagram illustrating another aspect of the integrated coating apparatus of FIG.

FIG. 5 is a conceptual diagram for explaining another aspect of the scraping section, and is a diagram for explaining a type in which an excessive amount of the coating liquid is scraped off by a rotating rod.

FIG. 6 is a conceptual diagram for explaining another aspect of the coating apparatus of the present invention, in which the precoat portion of the precoat means and the scraping portion of the scraping means are separate bodies.

FIG. 7 is a configuration diagram illustrating the overall configuration of a conventional scraping-type coating device.

[Explanation of symbols]

10, 65 ... Coating device, 12 ... Web, 14 ... Guide roller, 16 ... Coating head, 18 ... Supply line, 20 ... Collection line, 22 ... Controller, 24 ... Lip surface, 26
... pocket for application, 28 ... pocket for recovery, 30 ...
Application slit, 31 ... Precoat means, 32 ... Collection slit, 33 ... Scraping means, 34 ... Supply pipe, 3
6 ... Coating liquid tank, 38 ... Supply pump, 39 ... Precoat part, 40 ... Supply flow rate meter, 41 ... Scraping part, 42
... recovery pipe, 44 ... valve, 46 ... recovery flow meter, 48
… Sliding direction of guide roller, 50… Bead, 52…
Back lip surface, 54 ... Doctor lip surface, 56 ... Collection lip surface, 60, 66 ... Backup roller, 62 ...
Rotating rod

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B05D 1/26 B05D 1/26 Z 5/12 5/12 A G03C 1/00 G03C 1/00 E 1 / 74 1/74 G11B 5/842 G11B 5/842 Z (72) Inventor Tokuo Shibata 2-12-1, Ogimachi, Odawara-shi, Kanagawa Fuji Photo Film Co., Ltd. F-term (reference) 2H023 EA00 HA04 4D075 AC04 AC53 AC72 AC84 AC92 AC94 AC95 AC96 BB56Z BB92Z CA24 CA48 DA04 DB36 DC28 EA10 EA45 EB15 EB20 4F041 AA12 AB01 BA05 BA12 BA34 BA57 BA59 CA02 CA12 CA16 CA23 CA28 4F042 AA22 AB00 BA04 BA06 BA12 BA15 CA01 DD20 CC02 CB02 DD021717 HH09

Claims (26)

[Claims] 1. A continuous running belt-shaped support is pre-coated on one side with a pre-coating means in an amount exceeding the desired coating thickness to be finally obtained, and then from the running direction of the support. A coating method in which an excess of the coating liquid is scraped off by a scraping means provided on the downstream side of the precoating means, from when the coating liquid is applied to the support until the excess of the coating liquid is scraped off. 2. The coating method according to, wherein the coating liquid coated on the support is not exposed to the atmosphere. 2. The coating method according to claim 1, wherein the scraped off coating liquid is recovered through a closed system recovery line, and the recovered coating liquid is reused. 3. The desired coating thickness is obtained by adjusting at least one of the amount of precoat liquid for precoating and the amount of scraping liquid to be scraped off. How to apply. 4. The precoat liquid amount and the scraping liquid amount are respectively measured by a flow meter, and at least one of the precoat liquid amount and the scraping liquid amount is adjusted so that the difference between the flow rates becomes the desired coating thickness. The coating method according to claim 3, wherein the coating method is adjusted. 5. The coating method according to claim 1, wherein the desired coating thickness is obtained by adjusting the traveling speed of the support. 6. The coating method according to claim 1, 2 or 5, wherein the desired coating thickness is obtained by adjusting the viscosity of the coating liquid. 7. The desired coating thickness is obtained by adjusting the solid content concentration of the coating liquid.
Or the coating method of 6. 8. The flow resistance of the recovery line is adjusted to obtain the desired coating thickness.
Application method 6 or 7. 9. The scraping means presses the coating liquid applied to the support by pressing the scraping part of the scraping means and the support relative to each other, thereby removing the coating liquid. The coating method according to any one of claims 1 to 8, wherein an excessive amount is configured to be scraped off, and the desired coating thickness is obtained by changing the applied pressure. 10. The pressing force is obtained by wrapping the support member on the scraping portion, and the pressing force is changed by adjusting the tension in the traveling direction of the support member. 9. Application method of 9. 11. A backup roller is arranged on the back surface side of the support, on which the coating liquid is not applied, facing the scraping portion to obtain the pressing force, and a clearance between the scraping portion and the backup roller is provided. The coating method according to claim 9, wherein the applied pressure is adjusted by adjusting the pressure. 12. An elastic backup roller is disposed on the back side of the support, on which the coating liquid is not applied, facing the scraping portion to obtain the pressing force, and the longitudinal elastic modulus of the backup roller or The coating method according to claim 9, wherein the applied pressure is adjusted by adjusting at least one of hardness. 13. A spraying means for spraying a fluid is arranged on the back surface side of the support, on which the coating liquid is not applied, to oppose the scraping off portion to obtain the pressurizing force and adjust the spraying pressure of the spraying means. The coating method according to claim 9, wherein the applied pressure is adjusted by carrying out. 14. The coating solution according to claim 1, wherein the coating solution is a magnetic coating material in which magnetic particles are dispersed.
How to apply. 15. A continuous running belt-shaped support is pre-coated on one side with a coating solution in an excess amount over a desired coating thickness to be finally obtained by using a pre-coating means, and then from the running direction of the support. A coating device for scraping off an excessive amount of the coating liquid by a scraping means provided on the downstream side of the precoating means, from when the excessive amount of the coating liquid is scraped off after the coating liquid is applied to the support. 2. The coating apparatus according to claim 1, further comprising an atmosphere release preventing mechanism for preventing the coating liquid applied to the support from being exposed to the atmosphere. 16. The atmosphere release preventing mechanism is formed by bringing a lip surface of an application head integrally having a precoat portion of the precoat means and a scraping portion of the scraping means into close proximity to the support. 16. The coating apparatus according to claim 15, wherein the precoat portion is provided on the upstream side of the coating head in the support body traveling direction, and the dropping portion is provided on the downstream side. 17. The precoat portion is provided with a coating slit for discharging a coating liquid, and the scraping portion is provided with a collecting slit for collecting the scraped coating liquid. 16 coating devices. 18. A pair of guide rollers provided on an upstream side and a downstream side of the coating head wraps the support body on a lip surface of the coating head and adjusts a tension of the support body in a traveling direction. The coating apparatus according to claim 16 or 17, wherein the coating liquid coated on the support is pressurized to obtain a desired coating thickness. 19. A backup roller is arranged on the back surface side of the support, on which the coating liquid is not applied, facing the lip surface of the coating head, and the clearance between the lip surface and the backup roller is adjusted to adjust the clearance. The coating apparatus according to claim 16 or 17, wherein the coating liquid applied to the support is pressed to obtain a desired coating thickness. 20. The coating slit is connected to a supply line of a coating liquid to be precoated, the recovery slit is connected to a recovery line of the scraped coating liquid, and the supply line and the recovery line are coated. A flow rate control means for controlling the flow rate of at least one of the supply line and the recovery line such that a liquid flow meter is provided to measure the amount of the precoat liquid and the amount of the scrape-off liquid, and the difference in the flow amount is the desired coating thickness. 17. The method according to claim 17, wherein
~ 19 any one of the coating device. 21. Of the lip surface of the coating head, the shape of the doctor lip surface between the application of the coating liquid and the scraping of the excess coating liquid, and the scraping of the excess coating liquid The shape of the collecting lip surface is an arcuate curved surface that is convex toward the support, or two or more flat surfaces that are continuous and convex toward the support, or a combination of an arcuate curved surface that is convex toward the support and a flat surface. The coating device according to any one of claims 16 to 20, having a surface. 22. The radius of curvature of the doctor lip surface is R ₂
The coating device according to claim 21, wherein R ₂ > R ₃ when the radius of curvature of the recovery lip surface is R ₃ . 23. The scraping unit is provided with a rotary rod that comes into contact with the coating surface of the support coated with the coating liquid to scrape off an excess of the coating liquid.
The coating device according to any one of 6 to 20. 24. The atmosphere opening mechanism comprises a precoat portion of the precoat means and a scraping portion of the scraping means as separate bodies, and the traveling of the support between the precoat portion and the scraping portion. The coating device according to claim 15, further comprising a cover member that covers at least the coating surface of the support along the path. 25. The precoat section has a coating slit, the scraping section has a collecting slit, and one backup roller is provided so as to face both the precoat section and the scraping section. The coating device according to claim 24, wherein the coating device is provided. 26. The coating apparatus according to any one of claims 15 to 25, wherein the coating liquid is a magnetic coating material in which magnetic particles are dispersed.