JP2013215644A - Coating method and coating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating method and a coating apparatus in which wet extension can be controlled even if coating liquid has low viscosity, and a desired coating amount can be started up promptly even if being a thin film coating.SOLUTION: A coating apparatus 10 of a slot die method includes: a coating solution supply line 40 provided with a supply pump 42 that supplies a coating liquid 18 to a slot die 24; a coating liquid discharge line 44 that exhausts the coating liquid 18 from the slot die 24; a control valve 46 disposed at the coating liquid discharge line 44 and regulating a discharge amount of the coating liquid 18; an opening and closing valve 48 disposed at the coating liquid discharge line 44 and opening and closing the discharge line; a detection sensor 52 that detects whether the coating liquid 18 is filled up to a tip of a slot 16; and a controller 50 that controls the supply pump 42, the control valve 46, and the opening and closing valve 48 based on a detection result of the detection sensor 52.

Description

  The present invention relates to a coating method and a coating apparatus, and more particularly to a technique for suppressing wetting and spreading of a coating liquid to an end portion in the slot die width direction at the start of coating or at the time of restarting coating in slot die type coating.

  Conventionally, bar coaters, reverse roll coaters, gravure roll coaters, and extrusion coaters have been used as coating devices to coat the surface of a web (band-shaped flexible support) to form a coating film with a desired thickness. A coating device such as a slot die coater is known. Among these, the slot die coater is widely used in various coating fields because it can apply a thin film at a higher speed than other types of coaters.

  FIG. 7 shows a conventional coating start step using a slot die.

  As shown in FIG. 7A, the web 12 to which the coating liquid 18 is applied is supported by the backup roller 14 and conveyed. On the other hand, the slot die 24 supplies the coating liquid from the coating liquid supply line 40 to the slot die 24 at the standby position P away from the web 12. And it waits in the state where the coating liquid 18 corresponding to the desired coating amount drips from the tip of the slot 16 (also referred to as a slit). By waiting in such a state of flowing down, it is possible to prevent the application liquid 18 from being applied to the web 12 at the start of application and to prevent the application of stripes by preventing the slot tip from drying. doing.

  Next, as shown in FIG. 7B, the slot die 24 is moved to the coating position C so that the distance between the tip of the slot 16 and the web 12 becomes a predetermined clearance. As a result, a coating solution bridge is formed between the tip of the slot 16 and the web 12 by the coating solution 18 discharged from the tip of the slot 16. Thereby, application | coating of the coating liquid 18 to the web 12 conveyed is started.

  Here, the coating solution crosslinking is also referred to as a coating solution bead, and the coating solution can be stably applied onto the web 12, and a state where no coating failure or film thickness variation occurs, that is, a good bead is formed. Means state.

  However, the conventional method for starting application has the advantage that the desired amount of application can be applied to the web 12 from the start of application by allowing the application liquid 18 to flow down before application starts, but the application liquid 18 is slotted. There is a problem that the die 24 spreads to the end in the width direction. When the wetting spread N (see FIG. 8) of the coating liquid 18 exceeds the web width, the backup roller 14 and a transport roller that transports the web 12 in the subsequent drying process are soiled with the coating liquid 18. End up. If the apparatus is contaminated, the coating operation must be stopped and cleaning must be performed, resulting in a large production efficiency loss.

  The wetting spread N is not a problem when the web width is wider than the slot die width because the wetting spread N does not protrude from both ends in the web width direction.

  However, it is usual to apply a plurality of types of different web widths with one slot die 24. In this case, as shown in FIG. 8, a slot die 24 having a large slot die width is used, and spacers 17 are inserted at both ends in the slot width direction to cope with the change in the coating width. Accordingly, since the web width is narrower than the slot die width, if the coating liquid 18 wets and spreads along the upper surface of the spacer 17 before or after the start of coating, the web spreads over the web width.

  For example, in low-viscosity thin film coating performed in the production of a functional film such as an optical film, coating using a slot die is often performed, and wetting and spreading are a problem.

  As a technique for preventing wetting and spreading in the slot die, for example, there are Patent Documents 1 to 3.

  Patent Document 1 discloses adjusting the shape and position of an application width regulating plate inserted at both ends of a slot in order to regulate the application width.

  In Patent Document 2, the upper edge of the spacer that regulates the coating width of the extrusion type coating apparatus and the corner portion on the bridging side protrude from the concave portion or the flat surface recessed from the flat surface of the upper edge. It is disclosed to form a convex portion.

  In Patent Document 3, the degree of wetting and spreading is detected between two points between the slit width and the actual coating width of the coating liquid filled between the slit tip (slot tip) and the substrate (corresponding to the web) at the coating start end. In addition, it is disclosed that the actual application width arrival time is calculated from the wetting spread speed, and the timing for starting the application and the nozzle moving speed are controlled.

Japanese Patent Laid-Open No. 07-112152 JP 2001-170542 A JP 2010-264329 A

  However, for example, in the case of low-viscosity coating with a coating solution having a viscosity of 10 cPa · s or less, the conventional wetting and spreading prevention techniques of Patent Documents 1 to 3 are insufficient, and the coating solution at the start of coating is insufficient. It can be considered that wetting spread is suppressed by delaying the start of liquid feeding.

However, for example, in the case of thin film coating with a coating amount of 30 cc / m ² or less (wet film thickness of 30 μm or less), by delaying the start of liquid feeding at the start of coating, a desired coating amount (desired wet weight) after the start of liquid feeding. It takes time to reach the coating amount required to obtain a thick coating film), so there are concerns about new problems such as an increase in defective parts and the occurrence of coating streaks due to drying of the nozzle tip of the slot die. Is done.

  From such a background, there is a demand for a coating method and a coating apparatus that can suppress wetting and spreading even when the coating liquid has a low viscosity, and that can quickly rise to a desired coating amount even in the case of thin film coating.

  The present invention has been made in view of such circumstances, and is capable of suppressing wetting and spreading even when the coating solution has a low viscosity, and can be quickly brought up to a desired coating amount even in a thin film coating. An object is to provide a method and a coating apparatus.

  In order to achieve the above object, the present invention discharges the coating liquid from the slot tip of the slot die to form a bridge of the coating solution in the clearance between the web supported by the backup roller and the slot tip, In the coating method in which the coating liquid is applied to the web via the coating liquid crosslinking, the slot is provided from the coating liquid supply line so that the coating liquid is maintained up to the slot tip in the preparation stage of the coating. The supply amount of the coating liquid supplied to the die and the discharge amount of the coating liquid discharged from the slot die to the coating liquid discharge line are set, and the supply amount is set so that the supply amount becomes a desired application amount to the web. The application preparation step to be set and the set values of the supply amount and discharge amount of the application liquid set in the application preparation step are fixed and the application is started at the timing of application start. A coating start step of closing the discharge line, characterized by comprising a.

  According to the coating method of the present invention, in the coating preparation step, the supply amount of the coating solution supplied from the coating solution supply line to the slot die and the discharge amount of the coating solution discharged from the slot die to the coating solution discharge line are set. A state in which the coating liquid is filled up to the end of the slot is formed, and the supply amount of the coating liquid to the slot die is set to a desired coating amount to be applied to the web. In the coating start process, the coating liquid discharge line is closed at the coating start timing while the set values of the supply amount and the discharge amount of the coating liquid set in the coating preparation process are fixed.

  As described above, in the coating preparation process, the coating liquid is filled at the tip of the slot and a supply amount corresponding to the desired coating amount to be applied to the web is waited until the start of coating with the slot die being supplied. To do. Therefore, the coating solution does not spread out on the end portion in the width direction of the slot die before the start of coating.

  Since the coating liquid discharge line is closed at the start of coating, the coating liquid bridge is formed with the web before the coating liquid wets and spreads at the end portion in the slot die width direction. Thereby, even if it is a low-viscosity coating liquid, wetting and spreading can be suppressed effectively.

  Also, since the desired amount of coating liquid is applied to the web from the end of the slot as soon as the coating liquid discharge line is closed, the desired amount of application can be quickly increased even for thin film coating. Here, as described above, the desired coating amount refers to a coating amount necessary to obtain a coating film having a desired wet thickness.

  Therefore, if the coating method of the present invention is carried out, it is possible to suppress wetting and spreading even if the coating solution has a low viscosity as well as coating with a normal viscosity and film thickness, and quickly even in the case of thin film coating. The desired application amount can be raised.

  In the coating method of the present invention, after the coating start step, a coating temporarily stopping step of temporarily stopping coating and a coating restarting step of restarting the temporarily stopped coating are provided, and in the coating temporarily stopping step, the coating liquid is discharged. The line is opened, and in the application resumption process, the application liquid discharge line is closed at the application resumption timing while the set values of the supply quantity and the discharge quantity of the application liquid set in the application preparation process are fixed. Is preferred.

  According to the coating method of the present invention, even when the coating temporarily stop step and the coating resumption step are performed after the start of coating, the coating liquid can be recovered when the coating is resumed by a simple operation of opening and closing the coating liquid discharge line. Can be prevented from spreading.

  As described above, the coating method of the present invention can not only prevent the coating liquid from spreading at both ends in the slot width direction, but also the coating liquid by a simple operation of only opening and closing the coating liquid discharge line. Even when the application is once stopped and restarted after the operation is started, the coating liquid can be prevented from spreading and spreading.

  Further, since it is a simple operation of only opening and closing the coating liquid discharge line, the operator's skill is not required, and wetting and spreading can be effectively suppressed even if the coating amount of coating liquid and the physical properties of the coating liquid change.

  In the coating method of the present invention, the viscosity of the coating solution is preferably 30 cPa · s or less. The viscosity of the coating solution is particularly preferably 10 cPa · s or less.

  This is because the coating method of the present invention exhibits a further wetting and spreading suppressing effect under coating conditions where the coating liquid is easily wetted and spread like a low viscosity coating having a viscosity of 30 cPa · s or less.

  In the coating method of the present invention, it is preferable that spacers for adjusting the coating width are provided at both ends in the width direction of the slot.

  This is because the coating method of the present invention exhibits a further wetting and spreading suppressing effect under coating conditions where the wetting and spreading tends to occur, such that spacers for adjusting the coating width are provided at both ends in the width direction of the slot.

  When the spacer is provided, the present invention is particularly effective when the lip surface of the slot die has an overbite structure or an underbite structure.

  This is because when the lip surface of the slot die has an over bite structure or an under bite structure, it is difficult to process and install the spacers without gaps at both ends in the width direction of the slot. That is, the slot gap amount of the slot die is a narrow gap of about 100 to 200 μm, and it is difficult to process a thin and flat spacer that can be inserted into the gap without any gap. Also, when there are steps on the upstream and downstream lip surfaces as in the over bite structure or under bite structure, after the spacers are fitted into both ends in the width direction of the slot, the spacers are pressed evenly from the upstream side and the downstream side. I can't. As a result, a gap is easily formed between the spacer and the inner wall surface of the slot.

  Therefore, the present invention exhibits a further wetting and spreading suppressing effect under coating conditions that easily spread and wet like slot die having an over bite structure or an under bite structure. The step (bite amount) between the downstream lip surface and the upstream lip surface of the overbite structure or underbite structure is preferably in the range of 10 to 150 μm.

  In order to achieve the above object, the coating apparatus of the present invention discharges the coating liquid from the slot tip of the slot die and forms a bridge of the coating solution in the clearance between the web supported by the backup roller and the slit tip. In the coating apparatus for coating the web with the coating liquid via the coating liquid bridge, the coating liquid is discharged from the coating liquid supply line provided with a supply pump for supplying the slotted die with the coating liquid. A coating liquid discharge line; an adjustment valve provided in the coating liquid discharge line for adjusting a discharge amount of the coating liquid; an open / close valve provided in the coating liquid discharge line for opening and closing the discharge line; A detection sensor for detecting whether or not the coating liquid is filled up to the point, and the supply pump and the adjustment valve based on the detection result of the detection sensor. Characterized by comprising a control means for controlling the said opening and closing valve and.

  According to the coating apparatus of the present invention, the coating liquid supply line that supplies the coating liquid to the slot die is provided with the coating liquid supply pump, and the amount of the coating liquid discharged is adjusted to the coating liquid discharge line that discharges the coating liquid from the slot die. An adjustment valve and an opening / closing valve for opening / closing the coating liquid discharge line are provided, so that the control means can control the supply pump, the adjustment valve, and the opening / closing valve based on the detection result of the detection sensor for detecting the liquid surface position at the slot tip. Configured.

  As a result, not only at the start of coating, but also at the time of resuming coating after stopping coating temporarily, the opening and closing of the coating liquid discharge line is controlled by simply opening and closing the coating liquid discharge line. It is possible to effectively suppress the spreading of the coating liquid in

  Therefore, it is possible to apply at the start of application or at the time of resumption of application even when using a low viscosity thin film application or slot die with an overbite structure or underbite structure, as well as application with normal viscosity and film thickness. The wet spread of the liquid can be effectively suppressed.

  In the coating apparatus of the present invention, in the coating preparation stage, the control means controls the supply pump and the adjustment valve with the open / close valve open to fill the coating liquid up to the slot tip. While maintaining, the supply amount of the supply pump is set to be a desired application amount to the web, and at the start of application, the set values of the supply amount and the discharge amount of the application liquid set in the application preparation step are fixed. It is preferable to close the coating liquid discharge line by controlling the opening / closing valve at the timing of starting coating.

  The control steps of how the control means controls the supply pump, the adjustment valve, and the open / close valve in order to suppress wetting and spreading of the coating liquid are shown.

  In the coating apparatus of the present invention, as in the case of the coating method described above, when the coating liquid is a low-viscosity coating, when the slot die has an overbite structure or an underbite structure, the coating width is applied to both ends in the width direction of the slot. As in the case where a spacer for adjusting the thickness is provided, a further wetting and spreading suppression effect is exhibited under the coating conditions where the wetting and spreading is easy.

  According to the coating method and the coating apparatus of the present invention, wetting and spreading can be suppressed even when the coating liquid has a low viscosity, and even a thin film coating can be quickly brought up to a desired coating amount.

  Accordingly, the backup roller and the transport roller after coating are not contaminated with the coating liquid, so that it is not necessary to perform the cleaning of the process, the manufacturing efficiency is improved, and the quality of the film with a coating film to be manufactured is also improved.

Configuration diagram of slot die type coating device Explanatory drawing of the coating liquid supply line and coating liquid discharge line mainly of the coating apparatus of the present invention Illustration of overbyte structure and underbyte structure Explanatory drawing of moving slot die between standby position and application position Flow chart of control steps of coating method of the present invention Example test results graph Explanatory drawing explaining the application start method in the conventional application method Explanatory drawing explaining the spread of wetness with the conventional coating method

  Hereinafter, preferred embodiments of a coating method and a coating apparatus of the present invention will be described in detail with reference to the accompanying drawings.

  Here, in the drawing, portions indicated by the same symbols are similar elements having similar functions. In addition, in the present specification, when a numerical range is expressed using “˜”, upper and lower numerical values indicated by “˜” are also included in the numerical range. In addition, the descriptions of upstream, downstream, upstream, and downstream mean all upstream (side) and downstream (side) with respect to the web conveyance direction.

[Configuration of coating device]
FIG. 1 is a cross-sectional view showing a configuration of a slot die type coating apparatus according to an embodiment of the present invention, and FIG. 2 mainly describes the configurations of a coating liquid supply line and a coating liquid discharge line in the slot die of the coating apparatus. It is explanatory drawing.

  As shown in FIGS. 1 and 2, the slot die type coating apparatus 10 is mainly disposed so as to be opposed to the backup roller 14 that rotates while supporting the web 12 conveyed in the direction of the arrow, and the slot 16. The coating liquid 18 is discharged from the front end of the die, and a coating liquid bridge 22 (also referred to as a coating liquid bead) is formed in the clearance between the lip surface 20 which is the die front end surface and the web 12, whereby the coating liquid is applied to the web 12. 18 and a decompression device 26 for decompressing the upstream side of the coating solution bridge 22 in the web conveyance direction. The slot die 24 is mounted on the base 28.

  There are no particular limitations on the type, viscosity, and coating amount of the coating liquid 18 used in the embodiment of the present invention. However, it is preferable to apply the present invention to low-viscosity coating in which the coating solution 18 has a viscosity of 30 cPa · s or less. In the case of such low-viscosity coating, the coating liquid tends to wet and spread on the widthwise end of the slot die 24 at the start of coating and at the time of restarting coating, and the present invention is particularly effective. Furthermore, the present invention is particularly effective for low-viscosity coating of 10 cPa · s or less.

In the embodiment of the present invention, the desired coating amount of the coating liquid applied to the web 12 is not particularly limited, but is preferably 30 cc / m ² or less, particularly 10 cc / m ² or less. preferable.

  The decompression device 26 is supported on the side surface of the base 28 on the backup roller 14 side. Specifically, the upstream side of the slot die 24 is covered with a cover 24A, and the air in the cover 24A is sucked with a vacuum pump (not shown) through the air pipe 24B, thereby reducing the pressure in the cover 24A. Thereby, the coating liquid bridge 22 is stabilized by balancing the force with which the upstream side of the coating liquid bridge 22 is pulled and the force with which the coating liquid is carried by the conveyance of the web 12.

  The slot die 24 includes a plurality of blocks 30 and 32 and a pair of side plates 34 and 36 (see FIG. 2).

  Then, by combining the plurality of blocks 30 and 32 and the side plates 34 and 36, the slot die 24 has a pocket 38 for storing the coating liquid 18 and a pocket 38 to the lip surface 20 which is the die tip surface. An extending slot 16 is formed.

  The length L of the slot 16 (the length from the upper end of the pocket to the tip of the lip) is preferably in the range of 30 to 150 mm. If the length L of the slot 16 is less than 30 mm and is too short, it is difficult to stably maintain the coating liquid 18 in a state where the tip of the slot 16 is filled. If the length L is too long, the pressure loss increases. It becomes necessary to increase the supply pressure of the supply pump 42 (see FIG. 2). Furthermore, if the length L is too long, the slot die 24 becomes large, and a larger installation space is required.

  The slot gap amount d is preferably in the range of 100 to 200 μm.

  Further, as shown in FIG. 2, the slot width W is designed so as to correspond to the maximum width of the web used for coating, and when the web 12 having a narrow web width is used, the slot width W is provided at both ends of the slot 16 in the width direction. It is preferable to correspond to the coating width W1 by inserting a pair of spacers 17. As described above, when the spacers 17 are inserted at both ends of the slot 16 in the width direction, the coating liquid 18 is likely to be spread N through the upper end of the spacer, and the present invention is particularly effective.

  The pocket 38 may have a substantially circular or semicircular cross-sectional shape. The pocket 38 is a liquid storage space for the coating liquid 18 whose cross-sectional shape is extended in the width direction of the slot die 24.

  Here, in the lip surface 20, the downstream lip surface in the conveyance direction (arrow direction) of the web 12 is referred to as a downstream lip surface 20A, and the upstream lip surface is referred to as an upstream lip surface 20B. In other words, the front end surface of the block 30 is referred to as a downstream lip surface 20A, and the front end surface of the block 32 is referred to as an upstream lip surface 20B.

  In FIG. 1, as the lip surface structure of the slot die 24, the case where the downstream lip surface 20A and the upstream lip surface 20B are flush with each other is shown, but an overbite structure or an underbite structure is more preferable.

  The overbite structure is a structure having a step D in which the upstream lip surface 20B is recessed from the downstream lip surface 20A, as shown in FIG. The under bite structure is a structure having a step D in which the upstream lip surface 20B protrudes from the downstream lip surface 20A, as shown in FIG. The step D between the downstream lip surface 20A and the upstream lip surface 20B in the overbite structure and the underbite structure is preferably in the range of 10 to 150 μm.

  As shown in FIG. 2, a coating liquid supply line 40 for supplying the coating liquid 18 to the pocket 38 is connected to the side plate 34 on one end side in the longitudinal direction of the pocket (in the slot die width direction). The coating liquid supply line 40 is provided with a supply pump 42 that supplies the coating liquid 18 from a coating liquid tank (not shown) to the pocket 38. The supply pump 42 can adjust the coating liquid supply amount by changing the number of rotations of the rotary blades.

  On the other hand, a coating liquid discharge line 44 for discharging the coating liquid 18 from the pocket 38 is connected to the side plate 36 on the other end side in the longitudinal direction of the pocket 38. As a result, the coating liquid supply line 40 and the coating liquid discharge line 44 are communicated with each other via the pocket 38 of the slot die 24. The coating liquid discharge line 44 is provided with an opening / closing valve 48 and a discharge amount adjusting valve 46 in series. By opening and closing the opening / closing valve 48, the coating liquid discharge line 44 can be fully opened and fully closed. Further, by adjusting the valve opening degree of the adjustment valve 46, the amount of the coating liquid discharged from the coating liquid discharge line 44 can be adjusted. The supply pump 42 is the only pump installed in the coating liquid supply line 40 and the coating liquid discharge line 44. The supply pump 42 supplies the coating liquid 18 to the pocket 38, so that the coating liquid 18 in the pocket 38 is supplied to the coating liquid discharge line. 44 to be discharged. The supply pump 42, the opening / closing valve 48, and the adjustment valve 46 are connected to the controller 50 by signal cables.

  As shown in FIG. 2, a non-contact type detection sensor 52 that detects whether the coating liquid 18 is filled up to the tip of the slot 16 is provided on the side of the tip of the slot 16 of the slot die 24. The detection sensor 52 is not particularly limited as long as it is a non-contact type, but an infrared sensor or an imaging device (for example, a CCD camera) that detects whether the coating liquid 18 is filled by imaging the tip of the slot 16 is suitable. Can be used. FIG. 2 shows a case where an infrared detection sensor 52 is used. An infrared emitting device 52A is provided on one side of the slot 16 in the width direction, and a light receiving device 52B is provided on the side of the other end type. The light receiving device 52B is connected to the controller 50 by a signal cable. Then, the detection sensor 52 detects whether or not the coating liquid 18 has risen from the tip end portion of the slot 16 due to surface tension.

  Further, as shown in FIG. 4, the controller 50 controls a moving mechanism (not shown) that moves the slot die 24 between an application position C at which application starts and a standby position P at which application preparation is performed. Thus, since the slot die 24 moves between the application position C and the standby position P, the detection sensor 52 is preferably supported by the slot die 24 and moved together.

  Next, the coating method of the present invention using the coating apparatus 10 configured as described above will be described with reference to the control step flow of FIG.

  FIG. 5 shows the control steps from the start of the operation of the coating apparatus 10 to the start of the application, until the application is temporarily stopped and restarted at least once until the operation of the coating apparatus 10 is terminated. is there.

[Application preparation process]
Before starting the operation of the coating apparatus 10, the controller 50 prepares for coating the slot die 24 at the standby position P in FIG. 4 shows only the coating liquid discharge line 44, the coating liquid supply line 40 is provided on the back side of FIG.

  First, the controller 50 fully closes the valve openings of the opening / closing valve 48 and the adjusting valve 46 and drives the supply pump 42 so that the coating liquid 18 drips from the tip of the slot 16. As a result, a bubble removal operation is performed to remove air from the pocket 38 and the slot 16 (step 1).

  Next, the controller 50 controls the rotational speed of the rotary blades of the supply pump 42 so that the amount of coating liquid supplied to the slot die 24 becomes the desired amount of coating liquid applied to the web 12 (step 2). ).

  Next, the controller 50 opens the opening / closing valve 48 and fully opens the valve opening of the adjustment valve 46, so that all the coating liquid 18 from the coating liquid supply line 40 flows to the coating liquid discharge line 44 and stops dripping ( Step 3).

  Next, the controller 50 gradually narrows the valve opening of the adjustment valve 46 from fully open while monitoring the detection result from the detection sensor 52 with the open / close valve 48 open. As a result, the coating liquid 18 supplied to the slot die 24 rises in the slot 16 toward the tip of the slot 16. The controller 50 sets the adjustment valve 46 to the valve opening when the detection sensor 52 detects the coating liquid 18, that is, the coating liquid discharge amount (step 4). Thereby, a state in which the coating liquid 18 is filled up to the tip of the slot 16 is formed, and the coating preparation is completed. In this case, as described above, the application liquid 18 of the slot die 24 is discharged to the application liquid discharge line 44 only by the supply pump 42 without providing the discharge pump, and the discharge amount is adjusted by the adjustment valve 46. A state in which the coating liquid 18 is filled up to the tip of the slot 16 can be formed with high accuracy.

  As described above, in the coating preparation step, the coating liquid 18 is filled at the tip of the slot 16 and a supply amount of the coating liquid corresponding to the desired coating amount to be applied to the web 12 is supplied to the slot die 24. Wait until application starts. Therefore, the coating liquid 18 does not spread out on the end of the slot die 24 in the width direction before the start of coating. In addition, after step 4, it is desirable to clean the slot die 24 that has become dirty due to dripping with the solvent of the coating liquid 18 or the like. Further, the bubble removal operation in Step 1 may not be performed when the viscosity of the coating solution is small and bubbles are easily removed.

[Coating start process]
When the preparation for application is completed, the controller 50 moves the slot die 24 from the standby position P in FIG. 4B to the application position C in FIG. 4A (step 5). By moving the slot die 24 to the application position C, a clearance with a predetermined gap corresponding to a desired application amount is formed between the web 12 and the lip surface 20 of the slot die 24.

  Next, the controller 50 keeps the opening / closing valve 48 fixed with the rotation speed of the rotating blades (application liquid supply amount) set in the supply pump 42 and the valve opening degree (application liquid discharge amount) set in the adjustment valve 46 fixed. Close (step 6). That is, the coating liquid discharge line 44 is closed at the application start timing, and the coating liquid 18 filled up to the slot 16 tip is discharged from the slot 16 tip.

  As a result, the coating solution bridge 22 is instantaneously formed between the coating solution 18 and the web 12 before the coating solution 18 wets and spreads on the end portion in the width direction of the slot die 24. Therefore, even under coating conditions where the coating liquid 18 is easily wetted and spread like a low-viscosity coating having a viscosity of 30 cPa · s or less, the wetting and spreading N described with reference to FIG. 8 can be effectively suppressed. In particular, the present invention is effective for suppressing wetting and spreading in a low viscosity application of 10 cPa · s or less.

Further, since the desired amount of coating liquid 18 is applied to the web 12 from the end of the slot as soon as the coating liquid discharge line 44 is closed, the desired application can be quickly performed even in the case of thin film coating of 30 cc / m ² or less as described above. Can be launched in quantity. In particular, the present invention is effective in coating a thin film of 10 cc / m ² or less.

[Pause once and stop application]
When the coating apparatus 10 that is continuously applied from the start of application is temporarily stopped, the controller 50 opens the opening / closing valve 48 in accordance with the timing of the application stop and moves the slot die 24 from the application position C to the standby position P. (Step 7). At this time, the rotation speed of the rotary blade set in the supply pump 42 and the valve opening degree set in the adjustment valve 46 remain fixed. Thereby, the coating liquid 18 supplied to the pocket 38 from the coating liquid supply line 40 is discharged from the coating liquid discharge line 44, and the discharge of the coating liquid 18 is stopped in a state where the coating liquid 18 is filled up to the tip of the slot 16. Therefore, the same standby state as described in the coating preparation step is reproduced on the slot die 24.

  When the application is resumed, the controller 50 moves the slot die 24 again from the standby position P to the application position C, and closes the opening / closing valve 48 at the application resumption timing (step 8). At this time, the rotation speed of the rotary blade set in the supply pump 42 and the valve opening degree set in the adjustment valve 46 remain fixed. Thereby, also when restarting application | coating, the wet spread N of the coating liquid 18 can be suppressed similarly to the time of application | coating start.

  When the application is temporarily stopped and the application is restarted, the process returns from step 8 to step 7 (step 9).

  In addition, after the application is temporarily stopped, when the slot die 24 is at the standby position P, the lip surface 20 of the slot die 24 is preferably cleaned with a solvent of the application liquid 18 or the like. This is because the coating liquid 18 adheres to the lip surface 20 during coating, and coating defects such as streak failure may occur when coating is resumed.

  When the application is finished, the opening / closing valve 48 is opened in accordance with the application completion timing, and the slot die 24 is moved from the application position C to the standby position P (step 10). Thereby, the application | coating driving | operation of the coating device 10 is complete | finished.

  In the coating method of the present embodiment, as a method of filling the coating liquid up to the tip of the slot 16, the valve opening of the adjustment valve 46 is gradually narrowed from the full opening while monitoring the detection result from the detection sensor 52. The coating liquid 18 was raised in the slot 16. However, the opening / closing valve 48 in step 3 is opened, and the coating liquid 18 is gradually opened from the state in which the valve opening of the adjustment valve 46 is fully closed and the coating liquid 18 is flowing down. May be filled at the tip of the slot 16. This method is effective when the coating liquid 18 in which bubbles are easily generated in Step 4 is used.

  The presence / absence of N in the coating solution when the coating method according to the embodiment of the present invention was applied was tested.

(Coating solution)
Viscosity: 0.1 cPa · s (25 ° C)
Application amount to the web: 10 cc / m ² (film thickness h of the coating film 18A: 10 μm)
(Web)
・ Web material: Triacetylcellulose film (TAC)
・ Web width: 400mm
(Applicator)
The coating apparatus 10 described in FIGS. 1 and 2 was used.

・ Slot width W ... 650mm
・ Slot length L ... 50mm
・ Slot gap d: 150 μm
・ Spacer width: 165mm
・ Overbite amount (step size) ... 50μm
・ Application width W1 ... 320 mm,
Relationship between the web width and the coating width: Since the coating width W1 is 320 mm wide with respect to the 400 mm wide web 12, the width of the end portion of the web 12 mounted on the spacer 17 portion is 40 mm. Therefore, if the coating liquid 18 exceeds 40 mm and spreads, the backup roller 14 is contaminated with the coating liquid 18 because it spreads beyond the web width.

(Application conditions)
Test 1 is a case where the application is started by moving the slot die 24 from the standby position P to the application position C in a state where the opening / closing valve 48 is opened and the valve opening of the adjustment valve 46 is fully opened.

  Test 2: The valve opening of the adjusting valve 46 is set to a state in which the coating liquid 18 is filled up to the tip of the slot 16, and in this setting state, the slot die 24 is moved from the standby position P to the coating position C to match the coating timing. In this case, the opening / closing valve 48 is closed to start application. That is, this is the case where the coating is started by the coating method of the present invention.

  Test 3 is a case where the adjustment valve 46 and the opening / closing valve 48 are both closed, and the application is started by moving the slot die 24 from the standby position P to the application position C in a state where the application liquid 18 is dripping from the tip of the slot 16. . That is, this is the conventional coating start method shown in FIG.

  Test 4 is a case where the coating liquid discharge line 44 having the adjustment valve 46 and the opening / closing valve 48 is not provided, and is substantially the same as the test 3.

(Test results)
The test results are shown in FIG. The reference line 1 in FIG. 6 is a width of 40 mm at the end of the web 12 placed on the spacer 17 portion. Further, the reference line 2 is at the start of application, and if the wetting spread N occurs beyond the reference line 1 by the reference line 2, it means that the backup roller 14 is contaminated with the coating liquid 18.

  As can be seen from the results of FIG. 6, in the test 1, since the coating liquid is not discharged from the slot front end, there is no wet spread N, but the coating cannot be performed.

  Test 2 is the coating method of the present invention, and the reference line 1 at the start of coating does not exceed the reference line 1. Therefore, in Test 2, the backup roller 14 was not contaminated with the coating liquid 18.

  In tests 3 and 4, the wet spread N before the start of coating exceeded the reference line 1, and the backup roller 14 was contaminated with the coating solution.

  DESCRIPTION OF SYMBOLS 10 ... Application | coating apparatus, 12 ... Web, 14 ... Backup roller, 16 ... Slot, 17 ... Spacer, 18 ... Coating liquid, 20 ... Lip surface, 20A ... Downstream lip surface, 20B ... Upstream lip surface, 22 ... Coating solution bridge | crosslinking ( 24 ... slot die, 26 ... decompression device, 28 ... base, 30, 32 ... block, 34, 36 ... side plate, 38 ... pocket, 40 ... coating solution supply line, 42 ... supply pump, 44 ... Coating liquid discharge line, 46 ... adjustment valve, 48 ... open / close valve, 50 ... controller (control means), 52 ... detection sensor

Claims (11)

The coating liquid is discharged from the slot tip of the slot die to form a bridge of the coating liquid at the clearance between the web supported by the backup roller and the tip of the slot, and applied to the web through the coating liquid bridge. In the application method of applying the liquid,
In the preparation stage of coating, the supply amount of the coating liquid supplied from the coating liquid supply line to the slot die and the coating liquid discharge line from the slot die so that the coating liquid is maintained up to the slot tip. An application preparation step of setting the supply amount so that the supply amount becomes a desired application amount to the web, and setting the discharge amount of the coating liquid to be discharged;
An application start step of closing the application liquid discharge line at the start of application while the set values of the supply amount and discharge amount of the application liquid set in the application preparation step are fixed, and How to apply. After the application start process, the application temporarily stop process of stopping the application, and the application restart process of restarting the temporarily stopped application,
In the coating temporarily stopping step, the coating liquid discharge line is opened,
2. The application liquid discharge line is closed at the application resumption timing while the set values of the supply amount and the discharge amount of the application liquid set in the application preparation step are fixed in the application resumption process. Application method.   The coating method according to claim 1, wherein the coating solution has a viscosity of 10 cPa · s or less. The coating method according to claim 1, wherein the desired coating amount is 30 cc / m ² or less.   The coating method according to claim 1, wherein spacers for adjusting a coating width are provided at both ends in the width direction of the slot.   The coating method according to claim 5, wherein the lip surface of the slot die has an overbite structure or an underbite structure. The coating liquid is discharged from the slot tip of the slot die, and a bridge of the coating liquid is formed in the clearance between the web supported by the backup roller and conveyed and the slit tip, and the coating liquid is applied to the web through the coating liquid bridge. In a coating apparatus for coating
A coating liquid supply line including a supply pump for supplying the coating liquid to the slot die;
A coating liquid discharge line for discharging the coating liquid from the slot die;
An adjustment valve provided in the coating liquid discharge line for adjusting the discharge amount of the coating liquid;
An open / close valve provided in the coating liquid discharge line for opening and closing the discharge line;
A detection sensor that detects whether or not the coating liquid is filled up to the tip of the slot;
A coating apparatus comprising: a control unit that controls the supply pump, the adjustment valve, and the open / close valve based on a detection result of the detection sensor.   In the application preparation stage, the control means controls the supply pump and the adjustment valve with the opening / closing valve opened to maintain the application liquid filled up to the tip of the slot and supply the supply pump. The amount is set so as to be a desired amount to be applied to the web, and at the start of application, the set values of the supply amount and the discharge amount of the application liquid set in the application preparation step are fixed and the application start timing is The coating apparatus according to claim 7, wherein the coating liquid discharge line is closed by controlling an opening / closing valve. The coating apparatus according to claim 7 or 8, wherein the coating solution has a viscosity of 10 cPa · s or less and the desired coating amount is 10 cc / m ² or less.   The coating apparatus according to claim 7, wherein the slot die has an overbite structure or an underbite structure.   The coating apparatus according to claim 7, wherein spacers for adjusting a coating width are provided at both ends in the width direction of the slot.

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