JP2009018277A - Coating method and coater - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent thick coating by a simple method when coating is started. <P>SOLUTION: An application film layer is formed on the surface of a web 15 by using a slide bead coater 80 through the process (1) of forming a film flow by pouring a coating liquid on the slide surface of the slide bead coater 80, the process (2) of making the film flow transfer part 70 of the slide bead coater 80 approach the web 15 relatively so that the transfer of the coating liquid to the web 15 is started from the piece end 70R in the width direction of the film flow transfer part 70 of the slide bead coater 80, and a process (3) of forming a coating film layer on the surface of the web 15 by making the transfer of the coating liquid cover the whole region in the width direction of the web 15. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention uses a slide bead coater to make paper, coated paper (paper surface coated with pigment, latex, etc.), synthetic paper having a multilayer structure made of polyolefin resin, plastic film, The present invention relates to a coating method and a coating apparatus for forming a coating film layer on the surface of a web such as a composite sheet.

  Examples of the coating film formed on the surface of the web include, for example, a thermal recording layer in which a thermal recording layer containing a leuco dye, a colorant and an adhesive, and a protective layer are sequentially formed on the surface of a plastic film. is there. The thermal recording medium is relatively inexpensive, the recording equipment is compact, and its maintenance is relatively easy. For this reason, recording media such as facsimiles and various computers, CRT medical diagnosis, and X-ray images are used. It is also used as a recording medium for printers for printers and plotters for CAD.

  A slide bead type coating device is used for forming the thermal recording material. The slide bead type coating apparatus is an apparatus including a slide bead coater and a backup roll. The slide bead coater includes a discharge slit for discharging the coating liquid, a slide surface on which the coating liquid discharged from the discharge slit flows down, and a film flow transfer unit at the tip of the slide surface. The backup roll is provided in the vicinity of the tip of the slide surface of the slide bead coater, and is used for winding the web and conveying it in a certain direction.

  In this apparatus, the coating liquid is discharged from the discharge slit of the slide bead coater and is made to flow down along the slide surface, and is brought close to the web conveyed by the backup roll, and is supported by the film flow transfer unit of the slide bead coater. A coating liquid bridge (coating bead) is formed between the body and the body. However, when coating is started with this apparatus, a portion (thick coating portion) in which the coating solution is excessively adhered to the object to be coated is formed. The thick coating part is insufficiently dried in the drying process and may remain undried, which causes various problems such as adhesion to the roll after the drying process. For this reason, conventionally, various methods for solving the problem of the thick coating portion have been proposed.

  For example, Patent Document 1 proposes a method in which an absorption roller is brought into contact with a thick coating portion generated at the start of coating to absorb an excessive coating liquid. Further, Patent Document 2 proposes a method of spraying gas from a direction substantially opposite to the conveying direction of the object to be coated toward the coating application start portion of the object to be coated, and leveling the thick coating part. Has been. In Patent Document 3, a guide member such as a flat plate is installed on the slide surface of the slide bead coater, and by collecting the coating solution with this guide member, the flow of the coating solution on the slide surface is changed, and the liquid rises. A method has been proposed in which a part is formed, thereby forming a crosslinking point, which is used as an application start point, and the thick-coated part is reduced.

JP-A-8-294663 JP 2002-273299 A JP 2006-26500 A

  The methods described in Patent Documents 1 and 2 have a problem in that the apparatus is increased in size to add another process using an absorption roller or air blowing means after the coating process. Moreover, since the method of patent document 3 installs a flat plate etc. on a slide surface, there existed a possibility of damaging on a slide surface.

  The present invention provides a coating method and a coating apparatus that reduce the thick coating portion generated at the start of coating without changing conditions such as the flow rate and the drying speed in the drying process and without using any jigs. For the purpose.

  The present invention has been made to solve the above-described problems, and includes a coating method shown in the following (A) to (C) and a coating apparatus shown in (D).

(A) A method of forming a coating film layer on the surface of a web using a slide bead coater, comprising the following steps (1) to (3).
(1) A step of causing the coating liquid to flow down on the slide surface of the slide bead coater to form a film flow,
(2) The step of relatively moving the membrane flow transfer portion of the slide bead coater closer to the web so that the transfer of the coating liquid to the web starts from one end in the width direction of the membrane flow transfer portion of the slide bead coater,
(3) A step of spreading the coating liquid to the entire width direction of the web to form a coating film layer on the surface of the web.

  (B) A coating method in which, in the step (2) of the coating method (A), the membrane flow transfer part of the slide bead coater is relatively approached to the web so that one end in the width direction precedes the other end.

  (C) In the step (2) of the coating method (A) or (B), the membrane flow transfer unit of the slide bead coater is performing air suction for pressure reduction from the vicinity of one end in the width direction of the membrane flow transfer unit. Coating method in which the web is relatively close to the web.

  (D) A slide bead coater including a discharge slit for discharging the coating liquid, a slide surface on which the coating liquid discharged from the discharge slit flows down, and a film flow transfer portion at the tip of the slide surface, and a web is wound around and fixed. A coating roll for transferring a film flow from a film flow transfer section of the slide bead coater to a web on the backup roll by bringing the slide bead coater close to the backup roll. Control means for controlling the membrane flow transfer part of the slide bead coater so as to approach the web so that one end in the width direction precedes the other end. Having a coating device.

  In the present invention, since the transfer of the coating liquid to the web starts from one end in the width direction of the membrane flow transfer portion of the slide bead coater, the membrane flow transfer portion of the slide bead coater is relatively brought close to the web. Without using an absorbing roller, a jig or the like, it is possible to prevent the coating liquid from excessively adhering to the web, and to reduce the thick coating itself at the start of coating. Accordingly, there is no generation of undried due to thick coating, and the process can be stabilized without soiling the roll or the like after the coating process. Further, since the drying load can be reduced, the production efficiency can be improved.

  FIG. 1 is an overall configuration diagram schematically showing an example of a coating apparatus according to the present invention. As shown in FIG. 1, in the production line 10, the web 15 is conveyed at a predetermined speed by the unwinding device 16 and the winding device 19. The unwinding device 16 has, for example, a tension control mechanism, and the traveling property of the unwound web 15 is ensured. Next, the unrolled web 15 passes through, for example, the foreign substance removing device (web cleaner) 17 and the internal charge removing device 18 and then reaches the backup roll 25.

  As the foreign matter removing device 17, for example, an outer two adhesive rolls and an inner two rubber rolls are used, and the inner rubber rolls are nipped between each other, and the rubber roll and the adhesive roll are nipped. it can. The foreign matter removing device 17 can remove foreign matter by transferring foreign matter on the web 15 between the inner rubber rolls and sucking it with the outer adhesive roll. The internal charge removing device 18 is for preventing coating surface troubles such as bead breakage during the coating process due to charging of the web 15.

  The web 15 that has undergone these steps is wound around a backup roll 25, and after the coating liquid is applied by the coating device 20, the web 15 is dried by the drying step 30, and after passing through the outfeed roll 35 having cooling means, It is wound up by the winding device 19. In addition, in FIG. 1, although what installed the six drying apparatuses 30 was illustrated, it is not limited to such a structure.

  FIG. 2 is a schematic view illustrating the configuration of the coating apparatus according to the present invention. As shown in FIG. 2, the coating apparatus according to the present invention includes a backup roll 25 around which a web 15 is wound, and a slide bead coater 80 disposed adjacent to the backup roll 25. The slide bead coater 80 is fixed to a pedestal 66, and the pedestal 66 is installed on the slide rail 63 so as to be movable in the direction (F) in the figure, for example. The rear end of the pedestal 66 is connected to left and right motors 67L and 67R that independently rotate the ball screws 69L and 69R via left and right ball screws 69L and 69R, and further, struts 68L and 68R. All of these members are arranged on the station base 55, and the slide bead coater 80 can be moved closer to or away from the web 15 by controlling the motors 67L and 67R.

  In the example shown in the figure, an example using a slide rail, a ball screw, a motor, or the like has been described. However, the present invention is not limited to such a configuration. For example, as long as the movement path of the slide bead coater can be controlled, a simple groove, a flat plate, or the like may be used instead of the slide rail. Moreover, it replaces with a ball screw and the cylinder etc. which operate | move by the combination of a gearwheel and a flat tooth, hydraulically or electrically, etc. are employable.

  FIG. 3 is a schematic view illustrating the apparatus configuration of the slide bead coater. In the example shown in FIG. 3, a slide bead coater having four cavities is shown in order to apply four layers of coating liquid to the web. The number of cavities can be set according to the number of.

  As shown in FIG. 3, the upper surface of the slide bead coater 80 is a slide surface (inclined surface) 80S, and a membrane flow transfer unit 70 is disposed at the tip of the slide surface 80S. Inside the slide bead coater 80, there are cavities 90a to 90d communicating with the discharge slits 92a to 92d, and the cavities 90a to 90d constitute the first layer (uppermost layer) to the fourth layer (lowermost layer), respectively. Coating liquids 95a to 95d are respectively stored. The coating liquids 95a to 95d in the cavities 90a to 90d are respectively discharged from the discharge slits 92a to 92d to the slide surface 80S by the liquid feeding device (not shown) and flow down from the film flow transfer unit 70. When the distance between the membrane flow transfer unit 70 and the web 15 is wide, the coating liquid flows down from the membrane flow transfer unit 70 to the waste liquid chamber 96 in the vacuum box 100. The film flow can be transferred onto the web 15 by narrowing.

  FIG. 4 is a top view showing an example of a vacuum box, (A) is a top view, and (B) is a cross-sectional view along AA. As shown in FIG. 4, for example, the vacuum box is divided into a waste liquid chamber 96 and a decompression chamber 97 by a partition plate 98. Then, the coating liquid flowing down to the waste liquid chamber 96 flows to the waste liquid line 96A and is discharged. The decompression chamber 97 is configured by the backup roll 25 and partition plates 98 and 99 whose front end faces the R (curve) of the backup roll 25, and the decompression chamber 97 is decompressed by the decompression line 97A. Application is performed. The decompression chamber 97 creates an air flow between the membrane flow transfer section 70 of the slide bead coater 80 and the backup roll 25, thereby preventing bead destruction due to air entrainment during coating and forming a uniform bead. It is for the purpose.

  In the coating apparatus according to the present invention, when the membrane flow transfer unit 70 of the slide bead coater 80 is brought close to the web 15, the transfer of the coating liquid to the web 15 starts from one end in the width direction of the membrane flow transfer unit 70 of the slide bead coater 80. The biggest feature is that it is controlled to start. This will be specifically described below.

  FIG. 5 is a diagram showing the web application state from the top of the web at the start of transfer, (A) is the state immediately after the start of transfer, (B) is the state where the application has progressed to some extent after the start of transfer, ( C) shows a state where the transfer of the coating liquid is extended to the entire width direction of the web. As shown in FIG. 5A, in the present invention, for example, a transfer start point is formed at the right end 15R in the width direction of the web 15, and the transfer is started. Hereinafter, this point is referred to as a transfer start point S. After the transfer start point S is formed at the end R, since the web 15 is traveling, the coating liquid 95 is spread obliquely as shown in FIG. This spread-out part is called an expanded part. As shown in FIG. 5C, the spread portion spreads to the opposite end portion 15L, and application of the entire area of the web 15 in the width direction is started.

  As described above, in the present invention, since the transfer start point S is limited to one point at one end of the film flow transfer unit 70, a large amount of excessive coating liquid is not transferred. That is, the transfer start point is slightly thicker than the other parts, but since the range is narrow, the thickness of the expanded portion from the transfer start point S is also reduced to the end L that is the final point. Thick coating is suppressed. Moreover, since the vicinity of the transfer start point S that is not applied to the entire area of the web is a portion that is not used as a product, even if it is somewhat undried, the product is not affected. Further, since thick coating of the coating liquid 95 at the start of coating can be suppressed, the load in the drying process after coating can be reduced, resulting in productivity and operability without changing the predetermined line speed. Can be improved.

  As described above, in order to form the transfer start point S at one end of a specific web, the membrane flow transfer unit 70 of the slide bead coater 80 is moved closer to the web 15 so that one end in the width direction precedes the other end. It is good to let them. This will be described in detail below.

  FIG. 6 is a top view illustrating the operation state of the coating apparatus according to the present invention, and (A) to (D) sequentially illustrate the operation states of application standby, application start, transfer start point formation, and stable application. FIG. 6A shows a basic evacuation state before the slide bead coater 80 approaches the web 15. In this state, the coating liquid (four-layer coating liquid in the above example) stably forms a film flow on the slide surface 80S of the slide bead coater, flows down the film flow transfer unit 70, and waste liquid in the vacuum box It is poured into a chamber (not shown). While maintaining this state, as shown in FIG. 6B, one end 70 (the right end 70R in the example shown in FIG. 6) of the membrane flow transfer portion on the side where the transfer start point is formed is connected to the other end (FIG. 6). In the example shown, the left end 70L) is moved closer to the web 15 by a certain distance, for example, 0.2 mm ahead. Such a fixed distance adjustment is performed by controlling the motors 67L and 67R, for example.

  As shown in FIG. 6C, the membrane flow transfer unit 70 of the slide bead coater 80 is brought close to the web 15 while maintaining the above-mentioned constant distance, and a transfer start point is formed at one end 70R thereof. The transfer start point depends on conditions such as the type of coating liquid and the film thickness, and is formed when, for example, the gap between one end 70R of the film flow transfer unit 70 and the web 15 is a distance of about 0.25 mm. The slide bead coater 80 further approaches the web, the bead spreads from the transfer start point, and the coating liquid is transferred over the entire width direction of the web 15 before long. At this time, the one end 70R of the membrane flow transfer unit stops when the gap with the web 15 reaches, for example, 0.15 mm, and thereafter, the other end 70L of the membrane flow transfer unit approaches, but the gap with the web 15 For example, when it reaches 0.15 mm, it stops when it reaches a stable application state. FIG. 6D shows this stable application state.

  In the example shown in FIG. 6, an example is shown in which the membrane flow transfer unit 70 is once brought close to the web 15 while being tilted with respect to the web 15. For example, the membrane flow transfer unit 70 is parallel to the web 15. In this state, after approaching the web 15, the movement of only one end (for example, the left end 70 </ b> L) of the membrane flow transfer unit 70 is stopped, and the other end (for example, the right end 70 </ b> R) is further moved to the web 15. After the transfer start point is formed, the movement is stopped, and the stopped one end 70L can be moved until the distance between the web 15 and the other end 70R becomes the same.

  As a method for starting the transfer of the coating liquid to the web 15 from one end (for example, 70 L) in the width direction of the membrane flow transfer unit 70 of the slide bead coater 80, the inside of the decompression chamber 97 shown in FIG. A method using the decompression line 97A can be employed. That is, by increasing the suction force by the decompression line 97A, the side where the decompression line 97A exists can be widened between the membrane flow flowing down the membrane flow transfer unit 70 and the web 15. Therefore, the transfer start point can be formed on the side where the decompression line 97A does not exist.

  As the coating solution, an aqueous thermosensitive layer containing a leuco dye, a colorant and an adhesive is used as the lowermost layer, an aqueous intermediate layer containing two types of adhesive is used as the second layer, and an aqueous protective layer is used as the third layer. An experiment was conducted in which this coating solution was applied to a transparent PET film having a thickness of 0.175 mm.

The coating was performed at a line speed of 7 m / min, a liquid feeding amount, a first layer of 180 cc / min, a second layer of 30 cc / min, and a third layer of 40 cc / min. Drying was performed using a total of six drying apparatuses (upper and lower vertical wind, slit nozzle gap 4 mm), and setting the nozzle wind speed and temperature as follows.
First dryer: 5.6 m / sec, 85 ° C
Second dryer: 3.3 m / sec, 85 ° C
Third dryer: 2.9 m / sec, 80 ° C
Fourth dryer: 2.7 m / sec, 80 ° C
5th drying device: 2.7 m / sec, 75 ° C.
Sixth dryer: 3.0 m / sec, 75 ° C

  Under the above conditions, the method of applying the slide bead coater to the backup roll is changed, and coating is performed by the following two methods, and the dryness of the thick coating part, the width of the thick coating part, the thickness of the thick coating part Was measured.

  Comparative Example: From the retracted state of FIG. 6A described above, the membrane flow is moved close to the backup roll so that the distance between the both ends 70L, 70R of the membrane flow transfer unit and the web 15 is the same, Application was carried out. In the comparative example, a thick coating portion having a width of 50 mm and a thickness of 0.6 mm was formed on the web 15. And this thick coating part was not able to be dried completely by a drying process.

  Example of the Invention: As shown in FIG. 6B from the retracted state of FIG. 6A, the right end 70R of the membrane flow transfer portion on the side where the transfer start point is formed is set to 0. 0 with respect to the left end 70L. In a state where it is advanced by 2 mm, the membrane flow transfer unit 70 of the slide bead coater 80 is brought close to the web 15, and when the distance between the right end 70R and the web 15 reaches 0.15 mm, the movement of the right end 70R is stopped, The transfer start point is formed on the 70R side, and then the movement of the left end 70L is also stopped when the gap between the left end 70L of the membrane flow transfer unit and the web 15 reaches 0.15 mm, whereby the transfer of the membrane flow is controlled by the web 15 The coating was carried out by extending to the full width of.

  In the example of the present invention, a thick coating portion having a width of 4 mm and a thickness of 0.2 mm was formed on the web 15. This thick coating portion could be completely dried by the drying process.

  According to the present invention, it is possible to prevent the occurrence of non-drying due to thick coating and to reduce the drying load. Therefore, the process in the coating technique using the slide bead coater can be stabilized and the production efficiency can be improved.

Overall configuration diagram schematically showing an example of a coating apparatus according to the present invention The schematic diagram which illustrated the composition of the coating device concerning the present invention. Schematic diagram illustrating the configuration of the slide bead coater Top view showing an example of a vacuum box (A) Top view, (B) AA sectional view The figure which showed the application | coating condition of the web at the time of the start from the upper part of the web (A) The state immediately after the start of transfer, (B) The state where application | coating progressed to some extent after the start of transfer, (C) The width direction of a web Expanded to the entire area The top view which illustrated the operation state of the coating device concerning the present invention (A)-(D): Operation start-application start point formation-operation state of stable application

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Production line 15 Web 16 Unwinding device 17 Foreign material removal apparatus (web cleaner)
18 Internal charge removing device 19 Winding device 20 Coating device 25 Backup roll 30 Drying process 35 Outfeed roll 55 Station base 63R, 63L Slide rail 66 Base 67R, 67L Motor 68R, 68L Post 69R, 69L Ball screw 70R, 70L Film flow transfer Part 80 Slide bead coater 90a, 90b, 90c, 90d Cavities 92a, 92b, 92c, 92d Discharge slits 95a, 95b, 95c, 95d Coating liquid 96 Waste liquid chamber 96A Waste liquid line 97 Decompression chamber 97A Decompression line 98 Waste liquid side partition plate 99 Air Side partition plate (a) Flow direction of web (F) Operating direction of slide bead coater (S) Transfer start point R Right side when the coating device and the web are viewed from the front L Left side when the coating device and the web are viewed from the front

Claims (4)

A method of forming a coating film layer on the surface of a web using a slide bead coater, comprising the following steps (1) to (3).
(1) A step of causing the coating liquid to flow down on the slide surface of the slide bead coater to form a film flow,
(2) The step of relatively moving the membrane flow transfer portion of the slide bead coater closer to the web so that the transfer of the coating liquid to the web starts from one end in the width direction of the membrane flow transfer portion of the slide bead coater,
(3) A step of spreading the coating liquid to the entire width direction of the web to form a coating film layer on the surface of the web.   In the step (2) of the coating method according to claim 1, the membrane flow transfer part of the slide bead coater is relatively approached to the web so that one end in the width direction precedes the other end. Application method.   In the step (2) of the coating method according to claim 1 or 2, the film flow transfer unit of the slide bead coater is relatively opposed to the web while performing air suction for pressure reduction from the vicinity of one end in the width direction of the film flow transfer unit. The coating method characterized by making it approach closely.   A slide bead coater having a discharge slit for discharging the coating liquid, a slide surface on which the coating liquid discharged from the discharge slit flows down, and a film flow transfer part at the tip of the slide surface, and a web is wound around and conveyed in a certain direction. A coating apparatus for transferring a film flow from a film flow transfer section of the slide bead coater to a web on the backup roll by bringing the slide bead coater closer to the backup roll. A coating apparatus having a moving means for moving the roll independently on the right and left with respect to the roll, and a control means for controlling the membrane flow transfer portion of the slide bead coater so as to approach the web so that one end in the width direction precedes the other end .

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