JP2003236456A - Rod coating method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rod coating method capable of forming a long and wide coating film on a continuously moving web by applying various liquid-state compositions. <P>SOLUTION: The rod coating method is carried out for forming a coating film A on a belt-like flexible support 12, which is extended by a plurality of guide rollers 20A, 20B, and 20C and moved continuously with tension in the moving direction, by using a coating rod 28 which measures the coating amount by scraping off the excess amount of a coating liquid 14, which is previously applied excessively by a precoat device 16, from the belt-like flexible support 12. The winding angle of the belt-like flexible support 12 to the coating rod 28 is adjusted to be 10-90°. <P>COPYRIGHT: (C)2003,JPO

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rod coating method and relates to a coating liquid as a medium for recording various images or data such as magnetic tape, photographic film, photographic paper and the like. , A belt-like flexible support (hereinafter “web”) using a coating rod
That's it. ) Is applied to form a coating film. As a method for obtaining a coating film having a desired thickness on a web, a rod coating method (also called a bar coating method), a reverse roll coating method, a gravure roll coating method, an extrusion coating method, etc. (Above, Yuji Harasaki, “Coating Method”, Tsuji Shoten, 1979,
reference). As prior art of such a coating method,
For example, (1) JP 2000-126673 A,
(2) Japanese Patent Application No. 12-255626, (3) Japanese Patent Application Laid-Open No. 9-
No. 75815, etc. Among the above coating methods, the rod coating method is widely used because of its simple equipment and thin layer coating. The rod coating methods are roughly classified into the following two types. The first method is an integrated application / metering method (pre-metering application) in which a continuously running web is brought into contact with the coating rod and the transfer liquid is applied to the web and the desired amount of application is measured together. Also referred to as a method). The second method is
Applying an excess coating solution to the web with a pre-coating device such as extrusion coating, and contacting the coating rod to scrape off the excess coating solution to measure the desired coating amount A method with a separate measurement type (also referred to as a post-measuring application method). In any of the above methods, a coating film having a desired thickness is formed on a web by using a coating rod such as a flat rod, a wire rod, or a grooved rod. However, the rod coating method is capable of thin layer coating with simple equipment,
Since the coating rod itself does not have the function of adjusting the thickness of the coating film in the web width direction, the web width direction can be compared to the extrusion coating method in which the thickness of the coating film in the web width direction can be adjusted by a slit or the like. There is a drawback that the thickness distribution tends to deteriorate. In particular, when a flat rod is used as the coating rod, the thickness distribution in the web width direction of the coating film is the thickness distribution in the width direction of the web itself, and the coating film applied by the pre-coating means. Because it is easily affected by thickness distribution, fluctuations in liquid feeding to the pre-coating device, and web tension distribution generated upstream or downstream of the coating device, the thickness distribution in the web width direction of the coating film is applied within the standard range. It was difficult to do. However, in the above prior art, no measures have been taken in view of such circumstances. That is, in the prior arts (1) and (2), it was not even recognized that the thickness distribution in the web width direction of the coating film changed due to disturbance. In (3), no means for suppressing the influence of the pre-coating means or the influence of disturbance is disclosed. The present invention has been made in view of such circumstances, and when forming a coating film on a web using a coating rod, the thickness distribution of the precoat coating film generated by the precoat means, It is an object of the present invention to provide a rod coating method capable of suppressing the thickness distribution failure of the coating film in the web width direction due to the web tension distribution generated upstream or downstream of the coating apparatus. In order to achieve the above object, the present invention provides a belt-like flexible support that is stretched around a plurality of guide rollers and is continuously run with tension applied in the running direction. A coating film is formed on the body using a coating rod that measures the coating amount by scraping off the excess coating solution of the band-shaped flexible support, which has been applied in advance with a pre-coating device. In the rod coating method, the wrapping angle of the strip-shaped flexible support with respect to the coating rod is 10 to 90 °. The thickness distribution of the coating film on the web applied by the coating rod is roughly divided into a thickness distribution in the longitudinal direction of the web and a thickness distribution in the width direction of the web. Among these factors, the factors affecting the thickness distribution in the longitudinal direction of the web are:
Web thickness distribution, web stiffness distribution, tension distribution applied to the web, coating rod processing accuracy, coating rod eccentricity, coating rod rotational speed unevenness, fluctuations in liquid feeding to the precoater The factors affecting the thickness distribution in the width direction of the web include web thickness distribution, web stiffness distribution, tension fluctuation applied to the web, processing accuracy of the coating rod, and pre-coating device. Thus, the thickness distribution of the coating film in a state where the coating liquid is applied can be considered. According to the inventor of the present application, by performing various evaluations, if the web is supported by the coating rod with a wrap angle in the above range, fluctuations in liquid feeding to the precoat apparatus and precoat It was confirmed that the thickness distribution of the coating film in the web width direction generated by the thickness distribution in the apparatus can be easily reduced. The "wrap angle" refers to a wrap angle defined by a wrapping conduction device (belt conduction device) in mechanics. In the present invention, the wrapping angle of the belt-like flexible support (web) with respect to the guide roller is 20 to 150 in both the guide roller upstream of the coating means and the guide roller downstream of the coating means. It is preferable that it is (degree). If fluctuation (distribution) occurs in the tension applied to the web, the thickness distribution of the coating film is adversely affected. However, the guide roller on the upstream side of the coating means and the guide roller on the downstream side of the coating means. By making the winding angle of the above range within the above range, for example, fluctuation (distribution) generated in the tension generated in the upstream or downstream drying zone can be reduced, and as a result, the thickness distribution of the coating film on the web This is because it can be reduced. In the present invention, it is preferable to use a flat bar or a fixed blade as the coating rod. This is because when a flat bar or a fixed blade is used as the coating rod, an effect specific to the present invention can be obtained. The details will be described below. As a configuration using a coating rod for measuring the coating amount, there are a configuration in which a backup roller is provided on the back surface of the web and a configuration in which no backup roller is provided. In a configuration without a backup roller or the like, there are a configuration in which a groove or a recess is provided on the surface of the coating rod, and a configuration in which a groove or a recess is not provided on the surface of the coating rod. In the configuration in which the backup roller is provided, the thickness of the coating film is controlled by the clearance between the coating rod and the backup roller. In a configuration in which a groove or a recess is provided on the surface of the coating rod among the configurations in which a backup roller or the like is not provided, the thickness of the coating film is controlled mainly by the groove or the recess on the rod surface. On the other hand, among the configurations in which no backup roller or the like is provided, a configuration in which grooves or dents are not provided on the surface of the coating rod, specifically, a flat bar (flat rod) with a flat rod surface or a rotating function is provided. In a configuration in which a fixed blade not provided is used, the thickness of the coating film is controlled mainly by the liquid pressure of the coating solution. However, when the film thickness of the coating film is controlled mainly by the liquid pressure of the coating liquid, the film thickness of the coating film is easily affected by fluctuations in the tension applied to the web. Even in this case, if the wrap angle of the web with respect to the coating rod and / or the wrap angle of the web with respect to the guide roller is in the above range, fluctuation (distribution) occurring in the tension can be relaxed, As a result, the thickness distribution of the coating film on the web can be reduced. DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a rod coating method and an apparatus to which the coating method according to the present invention is applied will be described in detail below with reference to the accompanying drawings. FIG. 1 is an overall configuration diagram of a coating apparatus 10 according to the present invention. The coating liquid 14 that has been excessively applied to the web 12 by the pre-coating apparatus 16 is measured by scraping it off with a coating rod 28. This is the case of the body-shaped rod coating apparatus 10 and is configured by the second method described in the section of the prior art. The rod coating apparatus 10 mainly includes an extrusion type pre-coating apparatus 16 for applying the coating solution 14 to the web 12 in excess of a desired coating solution amount, and a coating solution 14 applied to the web 12 in excess. It comprises a coating rod device 18 that scrapes off the excess and a plurality of guide rollers 20A, 20B, 20C provided along the web conveyance path. Extrusion-type precoat apparatus 1
6 is a web 12 in which the coating liquid 14 pumped into the pocket 22 is mounted on the guide rollers 20A, 20B, and 20C from the outlet 24A of the slot 24 communicating with the pocket 22 and travels at a constant speed in the direction of the arrow. Head end surface 2
Dispense continuously while pressing 6. Thereby, an excessive coating liquid is applied to the lower surface of the web 12 immediately before the coating rod device 18. In addition, the precoat apparatus 16
The invention is not limited to the extrusion-type coating device, and any coating device that applies a coating solution to the web 12 can be used. The coating rod device 18 supports a rod-shaped coating rod 28 disposed parallel to the width direction of the continuously running web 12 with a tension applied in the running direction on a rod support member 30. The guide roller 20A,
The web 12 is applied to the coating rod 28 by 20B and 20C.
With a predetermined wrap angle. Accordingly, the excess coating solution 14 applied to the web 12 by the pre-coating device 16 is scraped off by the coating rod 28 and measured to a desired coating solution amount, so that the desired thickness is obtained. The coating film A is formed. In this case, the coating rod 28 is rotated at a low speed in the direction opposite to the traveling direction of the web 12 by connecting a rotation drive source (not shown). Unlike the example shown in the figure, the web 12 is brought into contact with the web 12 by contacting it.
It may be configured to rotate in the same direction as the travel direction, and further, a structure configured so as not to rotate may be used. As the coating rod 28 to be used, a flat rod having a flat rod surface, a wire rod in which a wire is tightly wound around the rod, and a grooved rod in which grooves are formed in the circumferential direction of the rod base surface. Etc. can be used.
Further, the diameter of the coating rod 28 is often 1 to 50 mm, but is not particularly limited. The web 12 generally has a width of 0.3 to 5 m, a length of 45 to 20000 m, and a thickness of 2 to 2.
200 μm polyethylene terephthalate (PET),
Polyethylene-2,6-naphthalate, cellulose diacetate, cellulose triacetate, cellulose acetate propionate, plastic film such as polyvinyl chloride, polyvinylidene chloride, polycarbonate, polyimide, polyamide, paper, polyethylene, polypropylene, ethylene butene copolymer Etc. have 2 to 10 carbon atoms
A flexible strip made of paper or the like coated or laminated with α-polyolefins or a strip with a processed layer formed on the surface of the strip is used. The coating solution 14 is not limited to a non-Newtonian fluid such as a magnetic tape coating solution, but may be a Newtonian fluid using a gelatin solution having a relatively low viscosity in a photographic photosensitive layer as a binder. . When an organic solvent is used for the coating solution 14, aromatic hydrocarbons such as toluene, xylene and styrene, chlorinated aromatic hydrocarbons such as chlorobenzene and orthodichlorobenzene, monochloromethane, etc. Methane derivatives, chlorinated aliphatic hydrocarbons including ethane derivatives such as monochloroethane, alcohols such as methanol, isopropyl alcohol and isobutyl alcohol, esters such as methyl acetate and ethyl acetate, ethyl ether, 1,
Ethers such as 4-dioxane, ketones such as acetone and methyl ethyl ketone, glycol ethers such as ethylene glycol monomethyl ether, alicyclic hydrocarbons such as cyclohexane, aliphatic hydrocarbons such as normal hexane, aliphatic or aromatic A mixture of group hydrocarbons can be used. Since the coating rod 28 itself does not have a function of adjusting the film thickness distribution in the web width direction of the coating film A, the disadvantage is that the thickness distribution in the web width direction tends to be worse compared to the extrusion coating method. There is. In contrast, the inventors of the present invention set the wrap angle of the web 12 to the coating rod 28 to 10-9.
It was found that by setting the angle to 0 °, the thickness distribution of the coating film A caused by the precoat thickness distribution and the liquid feeding fluctuation can be suppressed. Similarly, the guide rollers 20A and 2
It has also been found that the thickness distribution of the coating film A due to the tension distribution of the web generated upstream or downstream of the coating apparatus can be relaxed by setting the wrapping angle of the web 12 to 0 C to 20 to 150 °. Here, the winding angle is as described above.
The wrap angle as defined in the wrapping conduction device in the mechanics refers to the web 12 and the horizontal tangent line 1 before contacting the coating rod 28 as shown in FIG.
3 and the angle theta ₁ formed by the, also those represented by the sum of the angle theta ₂ formed by the web 12 after the contact with the coating rod 28 and the horizontal tangent 13. This relationship also applies to the relationship between the guide rollers 20A and 20B and the web 12. The rod coating apparatus 10 constructed as described above.
According to this, the winding angle of the web 12 around the coating rod 28 is configured to be 10 to 90 °.
The web 1 for the guide rollers 20A and 20C
The wrapping angle of 2 is 20 to 150 °. Thus, the influence of the pre-coating can be suppressed when the excess coating liquid is scraped off by the coating rod 28, and the guide rollers 20A and 20C.
Since the winding angle of the web 12 with respect to the web is 20 to 150 °, for example, fluctuation (distribution) generated in the tension of the web 12 generated in the drying zone upstream or downstream
As a result, the thickness distribution of the coating film in the web width direction can be easily reduced. The web 1 for the coating rod 28
When the wrapping angle of 2 is more than 90 °, it is confirmed that the film surface quality of the coating film is inferior, and the guide rollers 20A and 2
When the winding angle of the web 12 with respect to 0C exceeds 150 °, the guide rollers 20A and 20C of the web 12
It has been confirmed that scratches caused by sticking to the surface are likely to occur, and neither is preferable. FIG. 3 is a block diagram of another embodiment of the rod coating apparatus 60 of the present invention, which is a case of a separate coating / metering type rod coating apparatus. In this configuration diagram, only the portion of the coating rod device 18 is shown. Other configurations are the same as the example of FIG. As shown in FIG. 3, the running web 1
A cylindrical coating rod 62 is disposed in the width direction of the web 12 in contact with the web 2. This coating rod 62 is
This is a so-called doctor blade as a fixed blade, and is formed integrally with the rod support member 64. And
The excessive coating liquid applied to the lower surface of the web 12 by the precoat device (see FIG. 1) is scraped off by the coating rod 62 and measured to a desired coating liquid amount. Is formed. The upper surface of the coating rod 62 is formed with a predetermined curvature, and a predetermined wrap angle can be formed between the web 12 and the cylindrical coating rod 28 (see FIG. 1). This coating / measuring separate type coating rod 62
Also in the case of the rod coating device 60 provided with the above, the wrap angle of the web 12 with respect to the coating rod 62 is set to 10 to 90 °. Thus, even in the case of the rod coating device 60 provided with the coating / measuring separate type coating rod 62, the coating liquid can be evenly transferred and coated on the web 12. Accordingly, the coating film A is applied to the web 12 using the coating rod 62.
When forming the film, the thickness distribution of the coating film in the web width direction can be easily reduced. Next, a drying apparatus as ancillary equipment used in the rod coating method according to the present invention will be described. The following configuration is an exemplification, and any configuration of the drying apparatus can be applied to the present invention. The drying device shown in the conceptual diagram of FIG. 4 is a roller-conveying dryer type drying device 70, and the web 12 is placed in a tunnel-like device body 70A in which an inlet 66 and an outlet 68 of the web 12 are opened at both ends. A plurality of pass rollers 72, 72,... The web 12 is conveyed on the pass roller 72 arranged in this manner with the coating film surface facing upward. A plurality of supply ports 74 for supplying air into the apparatus main body 70A are provided on the upper surface of the apparatus main body 70A.
Is formed on the lower surface of the apparatus body 70A.
A plurality of suction ports 76, 76... For sucking air in A are formed. Then, the air in the apparatus main body 70 </ b> A is sucked from the suction port 76 while supplying the drying air with appropriate drying conditions from the supply port 74, thereby drying the coating film surface formed on the surface of the web 12. The drying apparatus shown in the conceptual diagram of FIG. 5 is an air floating dryer type drying apparatus 82, and the web 12 is placed in a tunnel-shaped apparatus main body 82A in which an inlet 78 and an outlet 80 of the web 12 are opened at both ends. A plurality of air headers 84, 84,.
Arranged. The plurality of air headers 84 are
On both the upper side and the lower side across the web 12, the web 1
It arrange | positions so that it may be located alternately along 2 conveyance lines. Then, a plurality of air headers 84 arranged in an alternating manner are used to send dry air of appropriate drying conditions to the web 12.
By blowing out toward the coating film surface, the coating film surface is dried while the web 12 is floated and conveyed. The example of the embodiment of the rod coating method according to the present invention has been described above, but the present invention is not limited to the example of the above embodiment, and various modes can be adopted.
For example, in the present embodiment, the extrusion type pre-coating device 16 has been described with reference to FIG. 1, but a configuration in which an arbitrary coating device can be applied can also be adopted. EXAMPLE The web 12 shown in FIG. An implementation test of the present invention was performed using the rod coating apparatus 10 provided with a coating rod that scrapes off the excess of the coated coating solution 14 with the coating rod 28. The coating solution was prepared by thoroughly mixing and dispersing each component having the composition shown in Table 1 in a ball mill and then uniformly mixing and dispersing 30 parts by weight of an epoxy resin (epoxy equivalent 500). used. The web is PET
The material was used. [Table 1] Table 2 shows the results of an implementation test of the present invention. In the table, Examples 1 to 29 are examples of the present invention, and Examples 30 to 35 are comparative examples. As the coating rod, flat bars and wire bars were used in the examples of the present invention, and only flat bars were used in the comparative examples. [Table 2] As the viscosity of the coating solution, those of 8 cp and 20 cp were used in the examples of the present invention, and only those of 8 cp were used in the comparative example. The coating speed (web running speed) is 300m for most of the implementation categories.
For some examples, 600 m / min. The thickness of the pre-coated coating solution was 50 μm for most of the working sections and 100 μm for some examples. The diameter of the coating rod was 3 mm and 20 mm in the examples of the present invention, and only 3 mm was used in the comparative example. In Table 2, θ represents the wrap angle of the web with respect to the coating rod, and in the examples of the present invention, 10-9.
A value of 0 ° is employed, and in the comparative examples 3-8 ° and 10 °
A value of 0 ° was adopted. On the other hand, φ in Table 2 is the wrap angle of the web with respect to the guide roller. In the embodiment of the present invention, 2
A value of 0 to 150 ° is adopted, and in the comparative example 10 to 1
Values of 5 ° and 160 ° were adopted. The evaluation criteria for the coating film are based on the following four items. A) The effect of unevenness of the pre-coated coating liquid and the effect of unevenness are performed by visual sensory inspection.
As "unevenness influence", it ranks according to (circle), (triangle | delta), and x. ○ indicates that no unevenness can be detected, Δ indicates that some unevenness is detected but within an allowable range, and x indicates that unevenness is detected and becomes defective. B) The coating film quality was checked by visual sensory inspection, and “film surface quality” was ranked according to ◯, Δ, and X. ○ indicates that no defects can be detected, △
Indicates that some defects are detected but within an allowable range, and x indicates that defects are detected and become defective. C) The presence or absence of the influence of the web fluttering in the drying apparatus arranged downstream was checked by visual sensory inspection, and was ranked according to ◯, Δ, and x as “fluttering”. A mark indicates that a defect due to web flutter cannot be detected, a mark indicates that a defect is partially detected but within an allowable range, and a mark indicates that a defect is detected and becomes defective. D) The presence / absence of sticking of the web to the guide roll was determined by visual sensory inspection, and “sticking” was ranked according to ○, Δ, and ×. ○ indicates that scratches due to web sticking cannot be detected, Δ indicates that some scratches are detected but within an allowable range, and × indicates that scratches are detected and become defective. As can be seen from the results, the web winding angle θ with respect to the coating rod is appropriately set, and
By appropriately setting the winding angle φ of the web with respect to the guide roller, the fluid pressure of the coating liquid interposed between the coating rod and the web can be made uniform, so that the coating film excess can be evenly distributed. Can be scraped off. In Examples 30 to 35 which are comparative examples,
The above four items (a to 4) which are the evaluation criteria of the coating film may be because the wrapping angle θ of the web with respect to the coating rod is not appropriate.
Any one or more of d) is defective. As described above, according to the rod coating method and apparatus of the present invention, when the coating film is formed on the web using the coating rod, the coating film in the web width direction can be formed. The thickness distribution can be easily reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall configuration diagram of a separate coating / metering type rod coating apparatus used in the present invention. FIG. 2 is an explanatory diagram illustrating a winding angle. FIG. 4 is an explanatory diagram illustrating a roller conveying dryer type drying device. FIG. 5 is an explanatory diagram illustrating an air floating dryer type drying device. DESCRIPTION OF SYMBOLS 10 ... Separate application | coating and measurement type | mold rod coating device, 12 ... Web, 14 ... Coating liquid, 16 ... Pre-coating device, 18 ... Coating rod device, 20A, 20B, 20C ... Guide roller, 22 ... Pocket, 24 ... Slot 26... Head end face 28. Coating rod 30. Rod support member A
... Coating film

Claims (1)

[Claims] [Claim 1] An excessive amount of coating liquid is preliminarily applied to a belt-like flexible support that is stretched by a plurality of guide rollers and continuously runs with tension applied in the running direction. In a rod coating method for forming a coating film by using a coating rod that measures the coating amount by scraping off the excess coating liquid of the coated strip-shaped flexible support, the above-mentioned coating rod with respect to the coating rod A rod coating method, wherein the winding angle of the belt-like flexible support is 10 to 90 °.