WO2013084483A1

WO2013084483A1 - Substrate coating method

Info

Publication number: WO2013084483A1
Application number: PCT/JP2012/007783
Authority: WO
Inventors: 小林　弘和; 佐々木　成人
Original assignee: Ｊｆｅスチール株式会社
Priority date: 2011-12-09
Filing date: 2012-12-05
Publication date: 2013-06-13
Also published as: KR20140103986A; CN103974783B; KR101778837B1; CN103974783A; IN2014CN03862A

Abstract

Provided is a substrate (1) coating method that, when coating multiple layers of coating liquids on a continuously running substrate (1) using a roll coater, can apply thin films beautifully at high speed. Multiple layers of coating liquids are supplied to a rotating applicator roll (5) by a die coater (7). Then, the applicator roll (5) is brought into contact with a continuously running substrate (1) to transfer the multiple layers of coating liquids onto the substrate (1). At this time, the applicator roll (5) rotates in the direction opposite to the substrate (1) at the area of contact with the substrate (1). For the multiple layers of coating liquids supplied by the die coater (7), μ1 < μ2 when the coefficient of viscosity of the coating liquid forming the lowest layer on the applicator roll (5) is μ1 and the coefficient of viscosity for the coating liquid(s) forming the upper layer(s) is μ2. The multiple coating liquids remaining on the applicator roll (5) without being transferred to the substrate (1) are removed from the applicator roll (5).

Description

Application method to substrate

The present invention relates to a coating method for coating a substrate with a multilayer coating solution.

Conventionally, various coating films are formed on the substrate surface in order to impart performance such as corrosion resistance, workability, aesthetics, and insulation to a continuously running substrate substrate such as a steel plate. . In this treatment, a roll coater roll coater is generally used, and a two-roll coater using two rolls or a three-roll coater using three rolls is widely used. In particular, the 3-roll coater has become a mainstream coating method because it has excellent controllability of the coating thickness and has a relatively beautiful surface appearance. The three-roll coater adjusts the amount of coating liquid picked up by the pick-up roll 11 and the pick-up roll 11 that draws up the coating liquid from the coating coater liquid-in-the-pan 13 filled with the coating liquid as shown in FIG. A doctor roll metering roll 12 and an applicator roll applicator roll 5 that transfers the adjusted coating solution from the pickup roll 11 to the substrate 1 are configured. The direction of rotation of each roll may be a reverse rotation that rotates in the opposite direction or a natural rotation that rotates in the same direction at the close point between the rolls or at the close point, but in general the reverse rotation is compared Since a smooth coating surface can be easily obtained, reverse rotation is often performed between the applicator roll 5 and the substrate 1. The applicator roll 5 uses a rubber roll in which rubber is lined on a steel roll so as not to damage the surface of the substrate 1.

As a typical coating defect of a roll coater including a three-roll coater, there is a streak-like appearance defect of streak-like mark that occurs in the roll circumferential direction called roping ribbing. This is known as a defect that occurs when the fluid pressure fluctuation of the liquid meniscus between the rolls and between the roll and the substrate exceeds the effect of stabilizing the surface tension. It is more likely to occur when a coating solution having a higher coefficient is used. For this reason, it is difficult to apply a liquid film beautifully at high speed with a high-viscosity coating liquid.

Further, in recent years, multilayer coating films are sometimes required in designing coating films formed on a substrate due to increasing needs for high added value such as high corrosion resistance and high insulation. As a method of applying a multilayer liquid film to form a multilayer coating film, the coating liquid is supplied from a plurality of slits and the curtain coater system is dropped in a curtain shape, or the die coater method is provided with a plurality of slits. There is a system of slot die coater (see FIGS. 9 and 10). (Patent Document 1, Patent Document 2)
However, in the case of a curtain coater, the minimum liquid flow rate at which the curtain can be formed is determined by the coating liquid, so that the film becomes thick unless the line speed is very high. However, increasing the line speed causes coating unevenness due to air entrainment and makes thin film coating difficult.
When using the die coater method, in order to reduce the film thickness, it is necessary to bring the gap between the base material and the die coater that supplies the coating solution close to the desired film thickness, and a smooth base material such as a glass substrate. However, in the case of a continuously traveling steel plate or the like, shape variation occurs in both the width direction and the longitudinal direction, so that it is difficult to make the die close.

On the other hand, there is no precedent for the method of applying a multilayer coating solution using a roll. This is presumably because it is difficult to maintain a multilayer state with a liquid film, for example, the coating liquid between the rolls and between the roll and the substrate are mixed. For this reason, the meniscus behavior between rolls and between the roll and the substrate for the multilayer coating solution is an unknown part.

Japanese Patent No. 4598493 JP 2004-160274 A

When performing the coating treatment of a multilayer coating solution by a roll coater alone, if the second layer coating solution is applied while the first layer coating solution is in an undried state, the first layer is scraped off and a laminated coating film Can not form. Therefore, it is necessary to apply the second-layer coating liquid after the first-layer coating liquid is applied and then through a drying process. However, in that case, the coating process and the drying process are required twice, and the running cost increases. Also, in the roll coater, the higher the substrate speed or the higher the viscosity of the coating solution, the more likely to cause streak defects in the roll circumferential direction called roping, and it is difficult to apply a high-viscosity coating solution beautifully at high speed. .

The present invention has been made in view of such circumstances, and a substrate that can be beautifully applied with a thin film at high speed when a multilayer coating solution is applied to a continuously running substrate using a roll coater. The object is to provide a method for applying to the skin.

The gist of the present invention is as follows.
[1] Supplying a multilayer coating liquid to a rotating applicator roll by a die coater, and then bringing the applicator roll into contact with a continuously running substrate to transfer the multilayer coating liquid to the substrate. The applicator roll rotates in the opposite direction to the substrate at the contact portion with the substrate, and the multi-layer coating solution supplied by the die coater has a viscosity coefficient of μ1 that forms the lowest layer on the applicator roll. When the viscosity coefficient of the coating liquid forming the upper layer is μ2, μ1 <μ2, and the multilayer coating liquid remaining on the applicator roll that is not transferred to the substrate is removed from the applicator roll. Application method to the material.
[2] A multilayer coating liquid is supplied to a rotating intermediate roll by a die coater, then the multilayer coating liquid is transferred from the intermediate roll to a rotating applicator roll, and then the applicator roll is continuously transferred. In transferring the multilayer coating liquid to the base material in contact with the traveling base material, the intermediate roll rotates in a direction opposite to the applicator roll at a contact portion with the applicator roll, and the applicator roll is The multi-layer coating solution that rotates in the direction opposite to the substrate at the contact portion and is supplied by the die coater has a viscosity coefficient μ1 of the coating solution that forms the lowermost layer on the applicator roll, and the coating solution that forms the upper layer. When the viscosity coefficient is μ2, μ1 <μ2, and the multi-layer coating remaining on the intermediate roll without being transferred to the applicator roll And / or coating method for a substrate and removing the remaining layers of coating liquid to the applicator roll is not transferred to the substrate from the intermediate rolls and / or the applicator roll.
[3] Before the multi-layer coating liquid is transferred to the base material by the applicator roll, the same coating liquid as the coating liquid that forms the lowermost layer on the applicator roll is pre-coated on the base material by the coater. After the pre-coating, while the pre-coated coating solution on the substrate is in a liquid state, the applicator roll performs transfer to the substrate while rotating in the opposite direction to the substrate at the contact portion with the substrate. The method for applying to a substrate according to the above [1] or [2], wherein
[4] When the rotational speed of the applicator roll is V ₁ and the traveling speed of the base material is V ₂ , 0.5 ≦ V ₁ / V ₂ ≦ 1.5 is satisfied [1] Or the coating method to the base material as described in [3].
[5] When the rotational speed of the intermediate roll is V _3, the rotational speed of the applicator roll is V ₁ , and the traveling speed of the substrate is V ₂ , 0.5 ≦ V ₃ / V ₁ ≦ 1.5 and the [2] or [3] the coating method of the substrate according to, which is a _{_{0.5 ≦ V 1 / V 2 ≦}} 1.5.
[6] Before pre-coating the substrate, the substrate is pre-coated with the same coating solution as the coating solution that forms the lowermost layer on the applicator roll.
6. The method for coating onto a substrate according to any one of [3] to [5], wherein the pre-coating is performed while the pre-pre-coated coating liquid is in a liquid state after the pre-pre-coating.
[7] The applicator roll uses a rubber roll obtained by lining rubber on a metal roll,
The method for coating a substrate according to any one of [1] to [6], wherein the die coater generates a negative pressure upstream of the coating part.

According to the present invention, a multilayer coating solution can be beautifully applied to a substrate with a thin film at high speed using a roll coater.

FIG. 1 is a side view of a coating apparatus according to an embodiment of the present invention. FIG. 2 is a side view of a coating apparatus according to another embodiment of the present invention. FIG. 3 is a side view of a coating apparatus according to another embodiment of the present invention. FIG. 4 is a side view of a coating apparatus according to another embodiment of the present invention. FIG. 5 is an enlarged view of the slit die coater according to the embodiment of the present invention. FIG. 6 is a side view of a coating apparatus according to another embodiment of the present invention. FIG. 7 is a side view of a coating apparatus according to a conventional embodiment. FIG. 8 is a side view of a coating apparatus according to a conventional embodiment. FIG. 9 is a side view of a coating apparatus according to another conventional embodiment. FIG. 10 is a side view of a coating apparatus according to another conventional embodiment.

Hereinafter, the present invention will be described in detail.
The present invention is a method of applying a multilayer coating solution supplied from a die coater to one side or both sides of a substrate that is continuously passed through one or a plurality of rolls.
FIG. 1 shows one embodiment of a coating method on a substrate of the present invention. In FIG. 1, 1 is a base material, 2 is a coating liquid collection container, 3 is a coating liquid, 4 is an intermediate roll, 5 is an applicator roll, 6 is a scraping device, 7 is a slit die coater, and 8 is a backup roll. According to FIG. 1, the multilayer coating solution is supplied from the slit die coater 7 to the intermediate roll 4, then transferred to the applicator roll 5 through the intermediate roll 4, and transferred and applied to the substrate 1. The intermediate roll 4 uses a flat roll whose surface is mirror-finished. The intermediate roll 4 rotates in the opposite direction to the applicator roll 5 at the contact portion with the applicator roll 5, and the applicator roll 5 rotates in the opposite direction to the substrate 1 at the contact portion with the substrate 1.
Further, a scraping device 6 is installed on the intermediate roll 4 in order to remove the coating liquid that is not transferred to the applicator roll 5 and remains on the intermediate roll 4.

So far, many studies have been made on the method of applying a multi-layer coating solution at the same time with respect to a method of applying directly to a substrate using a curtain die or a slit die, but there has been no attempt to apply it via a roll. This is because, when transferring a multilayer coating liquid from a roll to a roll or a base material, it is difficult to maintain a laminated state of the multilayer coating liquid and form a laminated coating film on the base material. It is. Therefore, the inventors have verified a coating method of a multilayer coating solution using a roll without being bound by a predetermined concept. As a result, it has been found that if the rotation direction of each roll is reversed between the rolls or between the applicator roll and the substrate, the laminated state of the multilayer coating liquid can be maintained. That is, in FIG. 1, the intermediate roll 4 rotates in the direction opposite to the applicator roll 5 at the contact portion with the applicator roll 5, and the applicator roll 5 is in the direction opposite to the base material 1 at the contact portion with the base material 1. By rotating, the laminated state of the multilayer coating liquid is maintained, and a laminated coating film can be formed on the substrate.

In addition, when the multi-layer coating liquid supplied by the die coater is μ1 as the viscosity coefficient of the coating liquid forming the lowermost layer on the applicator roll after being supplied to the applicator roll, the viscosity coefficient μ2 of the coating liquid forming the upper layer is Let μ1 <μ2. By setting μ1 <μ2, the line speed and roll peripheral speed conditions that are the limit of occurrence of roping and the like are governed by the physical properties of the coating solution that forms the lowermost layer, and the coating solution that forms the upper layer is used as a high-viscosity coating solution. Even in this case, the appearance can be improved and the substrate speed can be increased. Therefore, even when a high-viscosity coating liquid is used as the coating liquid, it becomes possible to apply beautifully at a higher speed. Further, by changing the film thickness ratio of the coating solution for forming the lowermost layer and the coating solution for forming the upper layer, the upper layer can be made thinner, and a highly viscous coating solution can be applied in a thin film. In addition, the said upper layer is a layer formed on the lowest layer.

Also, a scraping device such as a scraping blade is provided on the intermediate roll to which the coating liquid is supplied by the die coater, and the multilayer coating liquid remaining without being transferred is removed from the intermediate roll. This is because if the coating liquid remaining without being transferred to the intermediate roll is supplied again to the coating section of the die coater, the meniscus shape of the coating liquid is disturbed, and stable coating is hindered. In addition to the intermediate roll, a scraping device can be installed on the applicator roll. Any scraper can be used as long as the coating liquid can be scraped off. For example, a method of installing a blade blade or a metal blade or a rubber blade is simple. The material of the blade may be metal or rubber as long as uniform scraping can be performed.

When the rotation speed of the applicator roll is V ₁ and the running speed of the substrate is V ₂ , 0.5 ≦ V ₁ / V ₂ ≦ 1.5 is preferable. Further, when the intermediate roll is interposed _, assuming that the rotational speed of the intermediate roll is V _3, the rotational speed of the applicator roll is V ₁ , and the traveling speed of the substrate is V ₂ , 0.5 ≦ V ₃ / V ₁ ≦ 1.5 and 0.5 ≦ V ₁ / V ₂ ≦ 1.5 are preferred.
When V ₃ / V ₁ or V ₁ / V ₂ is outside the above range, the meniscus of the coating liquid between the rolls and between the applicator roll and the base material may be disturbed and the multilayer state may not be maintained and may be mixed. Furthermore, in order to maintain a good laminated structure and stably apply without being affected by the physical properties of the coating liquid formed in the upper layer, the speed ratio is set to 0.6 ≦ V ₃ / V ₁ ≦ 1.2 and 0.6 More preferably, ≦ V ₁ / V ₂ ≦ 1.2. The rotational speed of the applicator roll and the rotational speed of the intermediate roll are roll peripheral speeds.

The applicator roll is preferably a rubber roll with a rubber lining on the surface of the metal roll. By using a rubber roll, the influence of eccentricity can be absorbed by elastic deformation, and unevenness in appearance and change in the amount of adhesion can be reduced. The rubber lining thickness is preferably about 5 to 40 mm. The rubber hardness is preferably about 40Hs to 80Hs.

In addition, although it is a method that is often used that the base material is applied in a state of being wound around a backup roll, the present invention does not require a backup roll in which roll coaters are arranged on both sides of the base material. It is also applicable to simultaneous application on both sides.

FIG. 2 shows another embodiment of the coating method on the substrate of the present invention. In FIG. 2, the intermediate roll 4 is not provided, and the other symbols are the same as those in FIG. According to FIG. 2, a multilayer coating solution is supplied from the slit die coater 7 to the applicator roll 5, and then transferred and applied to the substrate 1. The applicator roll 5 rotates in the direction opposite to the base material 1 at the contact portion with the base material 1.
Further, a scraping device 6 is installed on the applicator roll 5 in order to remove the coating liquid that has not been transferred to the substrate 1 and remains on the applicator roll 5.
When the amount of the base material to be applied is small, it can be stably applied by the method shown in FIG. 2, but when the base material is large and continuous application is required, the applicator roll is worn out and has a non-uniform shape. In some cases, coating defects may occur. Therefore, when mass production in continuous operation is performed, the method of FIG. 1 is preferable.

FIG. 3 shows another embodiment of the application method to the substrate of the present invention. In FIG. 3, 1 is a base material, 2 is a coating liquid recovery container, 3 is a coating liquid, 4 is an intermediate roll, 5 is an applicator roll, 6 is a scraping device, 7 is a slit die coater, 8 is a backup roll, and 14 is a precoater. Pre-coater. According to FIG. 3, the multilayer coating solution is supplied from the slit die coater 7 to the intermediate roll 4, then transferred to the applicator roll 5 through the intermediate roll 4, and transferred and applied to the substrate 1. The intermediate roll 4 uses a flat roll whose surface is mirror-finished. The intermediate roll 4 rotates in the opposite direction to the applicator roll 5 at the contact portion with the applicator roll 5, and the applicator roll 5 rotates in the opposite direction to the substrate 1 at the contact portion with the substrate 1.
Further, a scraping device 6 is installed on the intermediate roll 4 in order to remove the coating liquid that is not transferred to the applicator roll 5 and remains on the intermediate roll 4.
Further, before the multi-layer coating liquid is transferred to the base material 1 by the applicator roll 5, the same coating liquid as the coating liquid that forms the lowermost layer on the applicator roll 5 can be pre-coated on the base material 1. A precoater 14 is installed. Then, after pre-coating, transfer from the applicator roll 5 to the substrate 1 is performed while the pre-coated coating liquid is in a liquid state.

As the coating solution that is applied to the substrate in advance by the precoater, the same coating solution that forms the lowermost layer on the applicator roll is used among the multilayer coating solutions supplied to the applicator roll by the die coater. By performing the pre-coating, it is possible to suppress air entrainment from the upstream side of the travel line of the base material when transferring by the applicator roll. Moreover, even if the coating liquid used for the pre-coating passes between the applicator roll and the base material and enters between the applicator roll and the base material by performing the pre-coating using the same coating liquid as the lowermost layer, the liquid film of the lowermost layer The coating can be performed stably without interfering with the stabilization effect due to. When the same coating liquid as the upper layer liquid or a high-viscosity coating liquid is used for the pre-coating, the effect of stabilizing the meniscus of the coating liquid is reduced and streak defects are likely to occur.
The liquid film thickness of the precoat has little effect on the appearance, but the mixing of bubbles and the like has an effect because it passes between the applicator roll and the substrate. Therefore, in order to prevent air bubbles from being mixed during pre-coating, it is possible to create a beautiful coating film with even less air bubbles by pre-coating the base material with the same coating liquid as the coating liquid to be pre-coated before pre-coating ( (See FIG. 6).

FIG. 4 shows another embodiment of the coating method on the substrate of the present invention. In FIG. 4, the intermediate roll 4 is not provided, and the other symbols are the same as those in FIG. According to FIG. 4, a multilayer coating solution is supplied from the slit die coater 7 to the applicator roll 5, and then transferred and applied to the substrate 1. The applicator roll 5 rotates in the direction opposite to the base material 1 at the contact portion with the base material 1.
Further, a scraping device 6 is installed on the applicator roll 5 in order to remove the coating liquid that has not been transferred to the substrate 1 and remains on the applicator roll 5.
Further, before the multi-layer coating liquid is transferred to the base material 1 by the applicator roll 5, the same coating liquid as the coating liquid that forms the lowermost layer on the applicator roll 5 can be pre-coated on the base material 1. A precoater 14 is installed. Then, after pre-coating, transfer from the applicator roll 5 to the substrate 1 is performed while the pre-coated coating liquid is in a liquid state.
When the amount of the base material to be applied is small, it can be stably applied by the method shown in FIG. 4, but when the base material is large and continuous application is required, the applicator roll is worn out and has a non-uniform shape. In some cases, coating defects may occur. Therefore, when mass production is performed in continuous operation, the method of FIG. 3 is preferable.

FIG. 5 is an enlarged view of the slit die coater 7. For example, when two layers of coating liquid are applied to the substrate, the slit die coater 7 includes two coating

liquid supply units

7a and 7b for supplying each liquid as shown in FIG. A suction suction slot 7c for generating a negative pressure can be provided on the upstream side of the section. The rotation of the intermediate roll or applicator roll causes an air flow to accompany the coating liquid supply unit. Therefore, if there is no suction mechanism, the probability of air entrainment occurring in the liquid film increases, which may result in coating defects. Therefore, the above problem is solved by generating a negative pressure by the suction 7c, the meniscus shape of the supplied coating liquid is stably maintained, and a gap several times as large as the film thickness formed on the substrate is formed. It becomes possible to ensure, and it becomes possible to apply stably by reducing the influence of gap fluctuation due to fluctuations in substrate thickness.
The supply of the coating liquid to the slit die coater 7 can be performed by, for example, a pump that can stably discharge a constant flow rate. At that time, the coating liquid can be stably supplied onto the intermediate roll or applicator roll by adjusting the negative pressure of the suction 7c, the gap between the intermediate roll or applicator roll to which the coating liquid is supplied and the tip of the slit die coater 7 and the like. can do.

Using the apparatus shown in FIGS. 1 and 2, a coil of 0.8 mm thick and 300 mm wide galvanized steel sheet is applied under the application conditions shown in Table 1, and a liquid film is formed on the galvanized steel sheet. Formed. Next, the appearance of the liquid film after drying was evaluated and the cross section of the liquid film (laminated state) was confirmed.
1 and 2, the slit die coater 7 has a coating liquid supply unit (not shown) for two-layer coating and a suction (not shown). The material of each roll is a flat surface metal roll in which the intermediate roll 4 is applied with hard chrome plating, and the applicator roll 5 is a rubber roll in which rubber is lined. Rubber lining thickness is 20mm, rubber is urethane rubber, hardness is Hs55 °. The roll diameter of each roll is 150 mm for both the intermediate roll 4 and the applicator roll 5. Five types of coating solutions were used, with viscosities of 1.5 mPa · s, 2 mPa · s, 4 mPa · s, 10 mPa · s, 20 mPa · s, and solids concentrations of 4%, 6%, 8%, 13%, and 20%. It is. The viscosity coefficient is the value at a liquid temperature of 20 ° C. The liquid film thickness was adjusted to 10 μm for the two layers by changing the ratio of the upper and lower coating liquid thicknesses on the intermediate roll 4 in FIG. 1 and on the applicator roll 5 in FIG.
As a comparative example, the case where the upper layer and lower layer coating liquids were changed was performed, and the appearance of the liquid film after drying and the cross section of the liquid film were confirmed in the same manner as in the inventive examples.

The appearance of the liquid film after drying was evaluated by cutting out the dried steel plate and visually and observing a TEM cross section. ◎ for a smooth film without streaking, ○ for a slight streak that is hardly noticeable visually, ○ Those that can be seen are marked as x.
In addition, as for the laminated state of the liquid film, it was determined that the liquid film had almost no mixing. Although a slight mixing was observed, the cross section to such an extent that the two layers could be distinguished was considered to be almost satisfactory. A case where the two layers were completely mixed and the two layers could not be distinguished was regarded as defective.

The results obtained above are shown in Table 1 together with the conditions.

As shown in Table 1, in the present invention example, it was possible to uniformly apply a multi-layer and high-viscosity coating solution with a thin film having a film thickness of 6 μm or less before drying using a roll coater.
On the other hand, in the comparative example, uneven stripes were generated, resulting in appearance defects, and the layers were mixed and the laminated state could not be maintained, so that a high-viscosity coating liquid could not be uniformly applied at high speed.

In the example of the present invention, a galvanized steel plate is used as a base material. However, the present invention is not particularly limited to a steel plate, but can be applied to other metal plates such as aluminum, paper, and films.

In addition, the conditions in which the applicator roll was rotated in the direction opposite to that shown in FIG. 1 were carried out under the same coating conditions as in Table 1. However, the laminated state could not be maintained, and the appearance was a streak-mark-on-whole-surface.

In addition, as a conventional method, as shown in FIGS. 7, 9, and 10, evaluation of the coating appearance after drying is performed on a steel sheet having the same specifications as the above-described example of the present invention using a roll coater alone, a slit die coater alone, and a curtain coater alone. And the cross section of the coating film (lamination state) was confirmed.

The applicator roll 5 and the pick-up roll 11 of the roll coater shown in FIG. 7 have the same specifications as the applicator roll and the intermediate roll of the invention example. The doctor roll 12 also has the same specifications as the intermediate roll, and the gap between the doctor roll 12 and the pickup roll 11 is 60 μm. As a result, in the case of the roll coater shown in FIG. 7, the roll peripheral speed was adjusted so as to obtain an optimal appearance as appropriate, but each liquid viscosity was 1.5 μmPa · s, 2 μmPa · s, 4 μmPa · s, 10 μmPa · s. s, 20 mPa · s, the critical speed at which the external appearance evaluation is x is 550 mpm (meter per minute, m / min, hereinafter abbreviated as mpm), 390 mpm, 340 mpm, 180 mpm, 140 As the viscosity became mpm, the higher the viscosity of the coating solution, the lower the speed limit. It was impossible to apply a high-viscosity coating solution beautifully at high speed as in the present invention. Moreover, it was difficult to produce a beautiful thin film having a film thickness of 8 μm or less before drying due to the accuracy of the gap between rolls. When the rotational speed of the pick-up roll was lowered to make a thin film, roping occurred and the appearance became a streak pattern.

In the case of the slit die coater shown in FIG. 9, in each solution, the gap between the slit coating outlet (not shown) and the steel plate gap (not shown) cannot be brought close to 100 μm or less due to the problem of the accuracy of the steel plate thickness. Thus, a thick film exceeding 30 μm before drying was obtained. In addition, when thinning was attempted and the amount of liquid supplied was reduced with the gap remaining as it was, a blurring mark was generated due to running out of liquid. Further, when the gap was made closer, blurring and streak patterns were generated due to the gap fluctuation accompanying the board thickness fluctuation.

In the case of the curtain coater shown in FIG. 10, since the liquid film thickness was set to about 10 μm in each liquid, the curtain formation became unstable when the amount of coating liquid supplied was decreased, resulting in a liquid defect and a defect in appearance.

As described above, when a conventional roll coater, slit die coater, or curtain coater is applied as a conventional method, roping occurs, scumming or curtain liquid film formation becomes impossible, and high-viscosity coating liquid is stably applied at high speed. I couldn't.

Using the apparatus shown in FIG. 3 and FIG. 4, a coil of 0.5 mm thick and 300 mm wide galvanized steel sheet is applied under the application conditions shown in Table 2, and a liquid film is formed on the galvanized steel sheet. Formed. Next, the appearance of the liquid film after drying was evaluated and the cross section of the liquid film (laminated state) was confirmed.
3 and 4, the slit die coater 7 has a coating liquid supply unit (not shown) for two-layer coating and a suction (not shown). The material of each roll is a flat surface metal roll in which the intermediate roll 4 is applied with hard chrome plating, and the applicator roll 5 is a rubber roll in which rubber is lined. Rubber lining thickness is 20mm, rubber is urethane rubber, hardness is Hs55 °. The roll diameter of each roll is 150 mm for both the intermediate roll 4 and the applicator roll 5. Five types of coating solutions were used, with viscosities of 1.5 mPa · s, 2 mPa · s, 4 mPa · s, 10 mPa · s, 20 mPa · s, and solids concentrations of 4%, 6%, 8%, 13%, and 20%. It is. The viscosity coefficient is the value at a liquid temperature of 20 ° C. The liquid film thickness was adjusted to 10 μm for the two layers by changing the ratio of the upper and lower coating liquid thicknesses on the intermediate roll 4 in FIG. 3 and on the applicator roll 5 in FIG. In addition, the precoater apparatus used the same specification as an applicator roll by the 1 roll rotated in the reverse direction to a base material.
Further, as shown in FIG. 6, the case where the pre-precoat was performed was also performed under the conditions described in Table 2. As a result, it was confirmed that a beautiful coating film in which mixing of bubbles was further suppressed was obtained.
Moreover, it performed about the case where the coating liquid of an upper layer and a lower layer was changed as a comparative example, and the evaluation of the external appearance of the liquid film after drying and confirmation of the liquid film cross section were performed like the example of this invention.

The appearance of the liquid film after drying was evaluated by cutting out the dried steel plate and visually and observing a TEM cross section. ◎ for the case where a smooth film is obtained without streaking, ○ for the case where slight streaks that are hardly noticed by visual inspection are generated, ○ Is x.
In addition, regarding bubbles mixed in, those that were hardly seen were marked as ◯. For those that can be confirmed a little, the result is x.
In addition, as for the laminated state of the liquid film, it was determined that the liquid film had almost no mixing. Although a slight mixing was observed, the cross section to such an extent that the two layers could be distinguished was considered to be almost satisfactory. A case where the two layers were completely mixed and the two layers could not be distinguished was regarded as defective.

The results obtained as described above are shown in Table 2 together with the conditions.

As shown in Table 2, in the example of the present invention, it was possible to uniformly apply a multi-layered and high-viscosity coating solution with a thin film having a film thickness of 6 μm or less before drying using a roll coater.
On the other hand, in the comparative example, uneven stripes were generated, resulting in appearance defects, and the layers were mixed and the laminated state could not be maintained, so that a high-viscosity coating liquid could not be uniformly applied at high speed.

In addition, although the galvanized steel plate was used as a base material in the said Example, it is not limited to a steel plate in particular, It applies to other metal plates, such as aluminum, paper, and a film.

In addition, the applicator roll was rotated in the direction opposite to that shown in FIG. 3 under the same application conditions as in Table 2. However, the laminated state could not be maintained, and the appearance was entirely streaked.

In addition, as a conventional method, as shown in FIGS. 8, 9, and 10, when the roll coater alone, the slit die coater alone, and the curtain coater alone are applied to a steel plate having the same specifications as in the above examples, the evaluation of the coating appearance after drying and The cross section of the coating film (laminated state) was confirmed.

The roll coater applicator roll 5 and pickup roll 11 shown in FIG. 8 have the same specifications as the applicator roll and intermediate roll of Example 2. The doctor roll 12 also has the same specifications as the intermediate roll, and the gap between the doctor roll 12 and the pickup roll 11 is 60 μm. As a result, in the case of the roll coater shown in FIG. 8, the roll peripheral speed was appropriately adjusted so as to obtain an optimum appearance. The liquid viscosity was 1.5 μmPa · s, 2 μmPa · s, 4 μmPa · s, 10 μmPa · s. s, 20 mPa · s, the critical speed at which the external appearance evaluation is x is 550 mpm (meter per minute, m / min, hereinafter abbreviated as mpm), 390 mpm, 340 mpm, 180 mpm, 140 As the viscosity became mpm, the higher the viscosity of the coating solution, the lower the speed limit. It was impossible to apply a high-viscosity coating liquid beautifully at high speed as in the present invention example. Moreover, it was difficult to produce a beautiful thin film having a film thickness of 8 μm or less before drying due to the accuracy of the gap between rolls. When the rotational speed of the pick-up roll was lowered to make a thin film, roping occurred and the appearance became a streak pattern.

In the case of the slit die coater shown in FIG. 9, in each solution, the slit coating outlet-steel gap cannot be brought close to 100 μm or less due to the problem of steel sheet thickness accuracy. It became a film. In addition, when an attempt was made to reduce the thickness and the amount of the supplied liquid was reduced while the gap was kept as it was, a sag due to liquid breakage occurred. Further, when the gap was made closer, blurring and streak patterns were generated due to the gap fluctuation accompanying the board thickness fluctuation.

DESCRIPTION OF SYMBOLS 1 Base material 2 Coating liquid collection container 3 Coating liquid 4 Intermediate roll 5 Applicator roll 6 Scraping device 7

Slit die coater

7a, 7b Coating liquid supply part 7c Suction 8 Backup roll 9 Curtain coater 10 Suction device 11 Pickup roll 12 Doctor roll 13 Coater Bread 14 Precoater 15 Precoater

Claims

A multi-layer coating solution is supplied to the rotating applicator roll by the die coater.
Next, in transferring the multi-layer coating liquid to the substrate by contacting the applicator roll with a continuously running substrate,
The applicator roll rotates in the opposite direction to the substrate at the contact portion with the substrate,
The multi-layer coating liquid supplied by the die coater is μ1 <μ2 when the viscosity coefficient of the coating liquid forming the lowermost layer on the applicator roll is μ1, and the viscosity coefficient μ2 of the coating liquid forming the upper layer,
A method of applying to a base material, comprising removing from the applicator roll a multilayer coating liquid that has not been transferred to the base material and remains on the applicator roll.
A multi-layer coating solution is supplied to the rotating intermediate roll by a die coater.
Next, the multilayer coating liquid is transferred from the intermediate roll to a rotating applicator roll,
Next, in transferring the multi-layer coating liquid to the substrate by contacting the applicator roll with a continuously running substrate,
The intermediate roll rotates in the opposite direction to the applicator roll at the contact portion with the applicator roll,
The applicator roll rotates in the opposite direction to the substrate at the contact portion with the substrate,
The multi-layer coating liquid supplied by the die coater is μ1 <μ2 when the viscosity coefficient of the coating liquid forming the lowermost layer on the applicator roll is μ1, and the viscosity coefficient μ2 of the coating liquid forming the upper layer,
Removing the multilayer coating liquid remaining on the intermediate roll and / or not transferred to the applicator roll from the intermediate roll and / or the applicator roll. A method of applying to a substrate.
Before the multi-layer coating liquid is transferred to the substrate by the applicator roll, the substrate is pre-coated with the same coating liquid as the coating liquid that forms the lowermost layer on the applicator roll by the coater.
After the pre-coating, while the pre-coated coating solution on the substrate is in a liquid state, the applicator roll performs transfer to the substrate while rotating in the opposite direction to the substrate at the contact portion with the substrate. The coating method to the base material of Claim 1 or 2 characterized by these.
The rotational speed of the applicator roll is V 1 , and the traveling speed of the base material is V 2 , 0.5 ≦ V 1 / V 2 ≦ 1.5. Coating method on the substrate.
When the rotation speed of the intermediate roll is V 3, the rotation speed of the applicator roll is V 1 , and the running speed of the substrate is V 2 , 0.5 ≦ V 3 / V 1 ≦ 1.5 and 0.5 ≦ V 1 / V 2 ≦ 1.5 The method for coating a substrate according to claim 2 or 3.
Before pre-coating the substrate, the substrate is pre-coated with the same coating solution as the coating solution that forms the lowermost layer on the applicator roll.
6. The method for coating onto a substrate according to claim 3, wherein the pre-coating is performed while the pre-pre-coated coating liquid is in a liquid state after the pre-pre-coating.
The applicator roll uses a rubber roll with a rubber lining on a metal roll,
The method for coating a substrate according to any one of claims 1 to 6, wherein the die coater generates a negative pressure upstream of the coating part.