JP2009240849A - Coating method/device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating method and a coating device which can keep an ejection level uniform. <P>SOLUTION: This coating device 1 can form a coating liquid film H1 on a conveyed object to be coated H by ejecting the coating liquid to the object to be coated H as liquid droplets. In addition, the coating device 1 comprises: an inkjet head 4 for ejecting the coating liquid to the object to be coated H; a coating liquid tank 50 which supplies the coating liquid to an inkjet head 4; and a heat exchanger 7 which can keep uniform the internal coating liquid temperature of the inkjet head 4. The coating liquid tank 50 is so designed as to keep constant the liquid level of the coating liquid tank 50. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a coating method and a coating apparatus.

  Conventionally, in the field of manufacturing various films such as a liquid crystal, a photoresist film, an overcoat film, an alignment film, a color filter, and an organic EL material necessary for manufacturing an electro-optical panel (a liquid crystal display device or an organic EL panel), for example, An inkjet coating method has been proposed as a coating method for coating a coating liquid on a coated material (for example, see Patent Document 1). The inkjet coating method is a method of forming a coating liquid film by ejecting a coating liquid as droplets from a nozzle of an inkjet head and arranging them on the surface of an object to be coated.

By the way, in such an ink jet coating method, for example, the following four techniques have been developed.
That is, in the first technique, a pressure loss measuring means is provided between the ink jet head and the coating liquid tank, and the pressure loss is set so that the pressure loss of the entire flow path becomes constant over time based on the measurement result. (For example, refer patent document 2). More specifically, in this technique, the pressure loss control means changes the cross-sectional area of the flow path or heats a part of the flow path.

  In the second technique, a sub-tank for supplying coating liquid is provided in the ink jet head, and the sub-tank can suck and discharge the coating liquid from the main tank, and the liquid level in the sub-tank is detected to detect the liquid. By controlling the surface to be constant, the inside of the ink jet head is controlled to a predetermined negative pressure (see, for example, Patent Document 3).

  In the third technique, the temperature of the member constituting the discharge port is detected and compared with a predetermined set temperature for the purpose of preventing the solvent evaporation of the liquid at the discharge port of the inkjet head. The discharge port is cooled based on the result (see, for example, Patent Document 4).

In the fourth technique, the viscosity of the ink is detected to control the coating liquid temperature, and the driving signal of the pressurizing unit is controlled (see, for example, Patent Document 5).
JP 2004-313895 A JP 2006-256262 A JP 2007-203649 A JP 2007-106061 A JP 2005-349647 A

  However, in recent years, according to the research of the present inventors, if the pressure loss and the ink viscosity are not kept constant in the ink jet coating method, the injection amount cannot be made constant especially during a long continuous injection, and it is uniform. It was found that a coating liquid film having a sufficient thickness could not be formed.

The reason is considered as follows.
First, a coating liquid tank for supplying a coating liquid is connected to the inkjet head, and droplets are ejected by drawing or pushing the coating liquid by deformation of a flexible plate by a piezoelectric vibrator. Since the flow path of the liquid is very narrow, even if the liquid level position fluctuates slightly in the coating liquid tank, the pressure loss when the coating liquid moves in the flow path changes over time, resulting in an injection amount This is because of changes.

  Further, in the ink jet head, the flexible plate is deformed by the piezoelectric vibrator, and a slight amount of heat is generated by the movement thereof. When the coating liquid is warmed by this heat, the viscosity of the coating liquid changes. This is because the pressure loss changes over time or the injection itself is affected, and not only fluctuations in the injection amount but also injection defects (bent injection, etc.) occur.

  In consideration of the above four techniques, the first and second techniques control the pressure loss, but the ink viscosity is not controlled, and the third and fourth techniques use ink. Although the viscosity is controlled, the pressure loss is not controlled. Therefore, in any case, the injection amount cannot be made constant.

  An object of the present invention is to provide a coating method and a coating apparatus capable of keeping the injection amount constant.

The invention according to claim 1 is a coating method in which a coating liquid film is formed on an object to be coated by ejecting the coating liquid as droplets from an inkjet head to the object to be conveyed.
The liquid level position of the coating liquid tank for supplying the coating liquid to the inkjet head is kept constant, and the coating is performed by the inkjet head while the coating liquid temperature inside the inkjet head is kept constant. And

The invention according to claim 2 is the coating method according to claim 1,
The liquid level position is kept constant by overflowing the coating liquid that exceeds a predetermined storage amount from the coating liquid tank.

The invention according to claim 3 is the coating method according to claim 2,
The coating liquid overflowed from the coating liquid tank is collected and re-supplied to the coating liquid tank.

The invention according to claim 4 is the coating method according to claim 1,
The liquid level position is detected by a liquid level sensor, and the liquid level position is kept constant by controlling the supply amount of the coating liquid to the coating liquid tank based on the detection result.

The invention according to claim 5 is the coating method according to claim 1,
The liquid level position is kept constant by raising the coating liquid tank based on the decrease amount of the coating liquid in the coating liquid tank.

Invention of Claim 6 is the application | coating method as described in any one of Claims 1-5,
The liquid level position is kept constant at a height of (ejection surface height−600 mm) <liquid surface position <(ejection surface height + 600 mm) with respect to the coating liquid ejection surface in the inkjet head. It is characterized by.

Invention of Claim 7 is the coating method as described in any one of Claims 1-6,
The temperature of the coating liquid inside the inkjet head is detected, and based on the detection result, the coating liquid is detected in any of the inkjet head, the coating liquid tank, and the flow path from the inkjet head to the coating liquid tank. By controlling the temperature, the temperature of the coating solution inside the inkjet head is kept constant.

The invention according to claim 8 is a coating apparatus for forming a coating liquid film on an object to be coated by ejecting the coating liquid as droplets on the object to be conveyed.
An inkjet head for injecting a coating liquid onto the object to be coated;
A coating solution tank for supplying a coating solution to the inkjet head;
Liquid level holding means for holding the liquid level position of the coating liquid tank constant;
And a temperature holding means for holding the coating solution temperature inside the ink jet head constant.

The invention described in claim 9 is the coating apparatus according to claim 8,
A coating solution supply means for supplying the coating solution to the coating solution tank;
The liquid level holding means is
The liquid level position is kept constant by overflowing the coating liquid that exceeds a predetermined storage amount from the coating liquid tank.

A tenth aspect of the present invention is the coating apparatus according to the ninth aspect,
The coating liquid supply means includes
A coating liquid collecting means is provided for collecting the coating liquid overflowed from the coating liquid tank and re-supplying the coating liquid to the coating liquid tank.

The invention described in claim 11 is the coating apparatus according to claim 8,
A coating solution supply means for supplying the coating solution to the coating solution tank;
The liquid level holding means is
A liquid level sensor for detecting the liquid level position;
Supply amount control means for controlling the supply amount of the coating liquid from the coating liquid supply means to the coating liquid tank based on the detection result by the liquid level sensor.

The invention according to claim 12 is the coating apparatus according to claim 8,
The liquid level holding means is
A decrease amount detecting means for detecting a decrease amount of the coating liquid in the coating liquid tank;
And a tank raising means for raising the coating liquid tank based on a detection result by the reduction amount detecting means.

The invention according to claim 13 is the coating apparatus according to any one of claims 8 to 12,
The liquid level position is
It is characterized by being held constant at a height of (ejection surface height−600 mm) <liquid surface position <(ejection surface height + 600 mm) with respect to the injection surface of the coating liquid in the ink jet head.

The invention according to claim 14 is the coating apparatus according to any one of claims 8 to 13,
The temperature holding means is
A temperature sensor for detecting a coating liquid temperature inside the inkjet head;
Temperature control means for controlling the temperature of the coating liquid in any of the ink jet head, the coating liquid tank, and the flow path from the inkjet head to the coating liquid tank based on the detection result of the temperature sensor. It is characterized by that.

  According to the present invention, the application liquid is applied by the inkjet head while keeping the liquid surface position of the application liquid tank that supplies the application liquid to the inkjet head constant. Pressure loss can be kept constant. In addition, since the application is performed by the inkjet head while keeping the temperature of the coating solution inside the inkjet head, the viscosity of the coating solution can be kept constant. Accordingly, even during continuous injection for a long time, the injection amount can be made constant as compared with the conventional case.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to this.

First, the coating apparatus according to the present invention will be described.
FIG. 1 is a conceptual diagram showing a schematic configuration of a coating apparatus 1 in the present embodiment.

As shown in this figure, the coating apparatus 1 includes a transport device 2, a coating unit 3, and the like.
The conveying device 2 conveys the workpiece H in the conveying direction X, and includes an unillustrated unwinding device and winding device, and a backup roller 20. Among these, the unwinding device feeds the object to be coated H in the transport direction X, and the winding device winds the material to be coated H fed from the unwinding apparatus. Further, the backup roller 20 applies a predetermined tension to the workpiece H between the unwinding device and the winding device. In addition, in this conveyance apparatus 2, the drying apparatus which dries the coating liquid adhering to the to-be-coated object H is provided between the backup roller 20 and the winding device.

The coating unit 3 has at least one inkjet head 4.
The ink jet head 4 ejects the coating liquid as droplets onto the coating object H transported between the backup roller 20 and the winding device so as to form the coating liquid film H1 on the coating object H. It has become. The inkjet head 4 is not particularly limited. For example, a thermal type head or a shear mode type (piezo type) head may be used. Here, the thermal-type head is a head that has a heating element, and rapidly changes the volume of the coating liquid by thermal energy from the heating element and ejects it from the nozzle. The shear mode type head is a head that has a vibration plate provided with a piezoelectric element in an ink pressure chamber, and discharges a coating liquid by a pressure change in the ink pressure chamber by the vibration plate. Hereinafter, in the present embodiment, the inkjet head 4 will be described as a shear mode type head.

FIG. 2 is a schematic perspective view showing an example of the shear mode type ink jet head 4, which has a broken surface in part.
As shown in this figure, the inkjet head 4 has a piezoelectric substrate 40, a top plate 41, and a nozzle plate 42.

  The piezoelectric substrate 40 is formed by joining an upper layer piezoelectric substrate 40a and a lower layer piezoelectric substrate 40b, and by grinding the upper layer piezoelectric substrate 40a and the upper portion of the lower layer piezoelectric substrate 40b, A plurality of parallel nozzle grooves 40c having a predetermined length and a flat surface 40d are provided. The plurality of nozzle grooves 40c are partitioned by two side walls 40e to form a sealed channel (coating liquid pressure chamber). The nozzle plate 42 is open on the side, and the opposite side is shallow, and the surface 40d. It is continuous. Further, a metal electrode 40f is formed by plating inside the nozzle groove 40c, and is continuous with the metal electrode 40g formed on the surface 40d. The metal electrode 40g is connected to a control unit 10 (see FIG. 1) described later via a connector (not shown). In addition, FIG. 2 shows a case where each nozzle groove 40c is used as a pressure chamber for the coating liquid, but it may be used alternately as a coating liquid pressure chamber and an air pressure chamber. The materials of the upper piezoelectric substrate 40a and the lower piezoelectric substrate 40b are not particularly limited, and may be made of, for example, an organic material. For example, alumina, aluminum nitride, zirconia, silicon, silicon nitride, silicon carbide, quartz, It may be made of an inorganic material such as lead zirconate titanate (PZT).

  The top plate 41 is disposed on the upper surface of the piezoelectric substrate 40. The top plate 41 closes the open side of the nozzle groove 40c, thereby forming a coating liquid channel 400 between the top plate 41 and the nozzle groove 40c. Further, the top plate 41 is formed with a notch 41 a, and the notch 41 a forms a coating liquid reservoir 401 inside the top plate 41. The coating liquid storage unit 401 communicates with the coating liquid flow path 400 via the coating liquid supply port 405, stores the coating liquid supplied from the coating liquid supply pipe 402, and supplies the coating liquid flow path 400 to each coating liquid flow path 400. It is supposed to be. In addition, the coating liquid storage unit 401 is connected to a pipe 403 used for bleeding the coating liquid. The pipe 403 is configured to be sealed by a valve (not shown) or the like when the coating liquid is ejected from the inkjet head 4.

  The nozzle plate 42 has a plurality of nozzle discharge ports 42 a for discharging the coating liquid. The nozzle discharge ports 42a are configured so that the coating liquid in the nozzle groove 40c is in a droplet state as the side walls 40e of the nozzle groove 40c are sheared and deformed to change the pressure in the nozzle groove 40c (coating liquid pressure chamber). It is designed to be discharged. The interval between the nozzle discharge ports 42a is preferably 0.02 to 0.3 mm. Moreover, in this Embodiment, the surface (injection surface) of the nozzle plate 42 is parallel to the surface of the to-be-coated object H, and it is preferable that the space | interval of both is 40 micrometers-1000 micrometers. Moreover, as a base material which comprises such a nozzle plate 42, a metal and resin are used, For example, stainless steel, a polyimide, a polysulfone, polyether sulfone etc. can be employ | adopted preferably. Particularly preferred is a polyimide resin, and DuPont: Kapton or Ube Industries, Ltd .: Upilex, etc. are preferred because they are excellent in dimensional stability, ink resistance, heat resistance and the like.

  The ink jet heads 4 as described above are installed in an arbitrary number and arrangement. The arrangement and number are preferably determined in accordance with the type of coating solution used and the coating conditions.

Here, the example of arrangement | positioning of the inkjet head 4 is demonstrated using FIG. 3, FIG.
FIG. 3 is a schematic plan view for explaining the arrangement angle θ of the inkjet head 4 with respect to the transport direction X.

As shown in this figure, the arrangement angle θ connects the centers of the nozzle discharge ports 42 a arranged in the nozzle plate 42 in a state where the object H to be coated and the surface of the nozzle plate 42 of the inkjet head 4 are parallel. The angle formed by the line and the conveyance direction X of the workpiece H. More specifically, the angle in the clockwise direction from the line connecting the centers of the nozzle discharge ports 42a to the conveyance direction X is positive. ing. For example, the angle θ1 in the figure is −45 °, and the angle θ2 is + 45 °.
Such an arrangement angle θ is + 45 ° ≦ θ ≦ + 90 ° in consideration of the size of the inkjet head 4 with respect to the width of the object H, the number of inkjet heads 4 to be arranged, and the stability of the coating surface. Alternatively, −45 ° ≦ θ ≦ −90 ° is preferable.

  FIG. 4 is a schematic plan view showing an arrangement example when a plurality of inkjet heads 4 are arranged. More specifically, FIGS. 4A and 4B are schematic plan views when the arrangement angle θ is arranged at 90 ° and −45 °.

  In these drawings, the adjacent inkjet heads 4 and 4 have their ends overlaid so that the intervals between the nozzle discharge ports 42a and 42a at the ends are the same as the intervals between the nozzle discharge ports 42a in one inkjet head. Wrapped and arranged. According to such an arrangement, it is easy to cope with the width of the object to be coated H, and there is no uncoated portion between the ink jet heads 4, and a stable coating liquid film H1 is obtained. In particular, according to the arrangement shown in FIG. 4B, the interval between the droplets applied from the nozzle discharge ports 42a can be made narrower than the arrangement shown in FIG. It is possible to increase the coating density in the width direction of H and perform coating with a stable film thickness. The arrangement of these inkjet heads 4 can be appropriately selected as necessary.

Each ink jet head 4 is provided with a temperature sensor 45 as shown in FIG.
The temperature sensor 45 detects the coating liquid temperature inside the inkjet head 4 and transmits it to the control unit 10 described later.

  Further, a coating liquid supply device 5 and a maintenance device 6 are connected to each inkjet head 4.

The coating liquid supply device 5 has a coating liquid tank 50.
The coating liquid tank 50 supplies the coating liquid to the inkjet head 4 during the coating operation, and is connected to the inkjet head 4 via the flow path R1. The coating liquid tank 50 also functions as a liquid level holding means in the present invention. By overflowing the coating liquid that exceeds a predetermined storage amount and discharging it to the flow path R2, the coating liquid is obtained. The liquid surface position (the height of the liquid surface) E is kept constant. In the present embodiment, the height of the liquid surface position E is (the height of the injection surface−600 mm) <the liquid surface position with respect to the injection surface of the coating liquid in the inkjet head 4 (the surface of the nozzle plate 42). It is kept constant at a height of E <(height of injection surface + 600 mm).

  Here, in the flow path R1, a valve B1 and a heat exchanger 7 are provided in this order from the upstream side to the downstream side.

  The valve B <b> 1 controls the supply of the coating liquid from the coating liquid tank 50 to the inkjet head 4.

  The heat exchanger 7 heats and cools the coating liquid in the flow path R1. The heat exchanger 7 is a temperature holding unit in the present invention, and is configured to keep the coating liquid temperature in the inkjet head 4 constant by cooperating with a control unit 10 described later.

An auxiliary tank 51 is connected to the above-described flow path R2.
The auxiliary tank 51 collects and stores the coating liquid that overflows from the coating liquid tank 50 and naturally flows through the flow path R <b> 2, and is disposed below the coating liquid tank 50. The auxiliary tank 51 is connected to the coating solution tank 50 through a flow path R3, and a pump P1 and a filter F are provided in the flow path R3.

  The pump P1 is for supplying the application liquid from the auxiliary tank 51 to the application liquid tank 50 and supplying it again, and the operating conditions are set so that the liquid surface position E of the application liquid tank 50 is constant according to the application conditions. Is set.

  The filter F filters the coating liquid that is re-supplied from the auxiliary tank 51 to the coating liquid tank 50. In addition, as such a filter F, it is preferable to pass a filter medium with an absolute filtration accuracy or semi-absolute filtration accuracy of 0.05 to 50 μm at least once.

  The maintenance device 6 performs cleaning of the ink jet head 4 and filling of a coating liquid, and has tanks 60 and 61.

  Among these, the tank 60 supplies a coating liquid to the inkjet head 4 under maintenance, and the tank 61 supplies a cleaning solvent to the inkjet head 4 under maintenance. These tanks 60 and 61 are connected to the ink jet head 4 through a flow path R5 and the like.

  Here, the flow path R5 communicates between the valve B1 and the heat exchanger 7 in the above-described flow path R1, and in this flow path R5, the pump P2 and the valve B2 are provided from the upstream side toward the downstream side. They are provided in this order.

The pump P2 supplies the coating liquid and solvent in the tanks 60 and 61 to the inkjet head 4 and forcibly supplies them.
The valve B2 controls supply of the coating liquid and the solvent from the tanks 60 and 61 to the inkjet head 4.
One set of these tanks 60, 61, pump P1, and valve B2 may be provided for each inkjet head 4, or one set for a plurality of inkjet heads 4 by using branching of piping. Only these may be provided, or these may be combined.

Next, the functional configuration of the coating apparatus 1 will be described.
FIG. 5 is a block diagram showing a functional schematic configuration of the coating apparatus 1.

  As shown in this figure, the coating apparatus 1 includes a control unit 10 connected to the above-described inkjet head 4, transport apparatus 2, heat exchanger 7, valves B 1 and B 2, pumps P 1 and P 2, and the like. In FIG. 1 described above, only the connection between the control unit 10 and the inkjet head 4 is illustrated for the sake of simplicity of illustration.

  The control unit 10 controls each part of the coating apparatus 1. For example, when the coating liquid is ejected by the inkjet head 4, the operation strength and frequency of the piezoelectric substrate 40 are set, and the piezoelectric substrate 40 is subjected to the control unit 10. On the other hand, a drive voltage is applied.

  Further, the control unit 10 controls the heat exchanger 7 to keep the temperature of the coating liquid in the flow path R1 constant based on the temperature value transmitted from the temperature sensor 45, that is, the value of the coating liquid temperature in the inkjet head 4. By doing so, the temperature of the coating liquid in the inkjet head 4 is kept constant.

  In the present embodiment, the control unit 10 cancels the temperature change over time measured by the temperature sensor 45 for each application condition of the ink jet head 4 and cancels the temperature change in the ink jet head 4. Information on the temperature in the flow path R1 to be maintained by the heat exchanger 7 in order to maintain the coating liquid at a constant target temperature (hereinafter referred to as control temperature) is stored in advance in association with each other. As shown in FIG. 4, based on the application conditions set for the inkjet head 4, information on the control temperature corresponding to the application conditions is transmitted to the heat exchanger 7, and the temperature of the application liquid in the flow path R1 is controlled to the control temperature. To be controlled. Here, in FIG. 6, the horizontal axis represents time, the vertical axis represents temperature, the A line represents a temperature change measured in advance by the temperature sensor 45, the B line represents the target temperature of the coating liquid in the head, and the C line represents heat. This is the control temperature in the exchanger 7. However, the control unit 10 includes information on the temperature measured by the temperature sensor 45 and the control temperature in the flow path R1 that should be maintained by the heat exchanger 7 in order to maintain the coating liquid in the inkjet head 4 at a constant target temperature. May be stored in association with each other, and the control temperature may be transmitted to the heat exchanger 7 based on the measured temperature. In this case, even when the application is interrupted for some reason, the heat exchanger 7 can be appropriately controlled based on the temperature of the application liquid in the inkjet head 4 at the time of resumption.

Here, the coated object H in the present embodiment will be described.
As long as the workpiece H is a member that is long in the transport direction X, there is no particular limitation on the thickness and width. There is no restriction | limiting in the kind of this to-be-coated object, It can be set as paper, a plastic film, a metal sheet, etc. Examples of the paper include resin-coated paper and synthetic paper. Examples of plastic films include polyolefin films (eg, polyethylene film, polypropylene film), polyester films (eg, polyethylene terephthalate film, polyethylene 2,6-naphthalate film), polyamide films (eg, polyetherketone film). And cellulose acetate film (for example, cellulose triacetate film). As the metal sheet, an aluminum plate is typical.

Next, the coating liquid in this Embodiment is demonstrated.
The coating liquid preferably contains 0.5 to 50% by mass of a polymer component. Examples of the polymer component include gelatin, methyl cellulose, carboxymethyl cellulose, polyacrylic acid, polyvinyl ether, polyvinyl alcohol, polyvinyl pyrrolidone, and natural rubber. The coating solution containing these polymer components is not particularly limited. For example, a general or industrial silver halide photosensitive material coating solution, a heat sensitive material coating solution, or a photothermographic material coating solution may be used. Alternatively, a solution obtained by dissolving a polymer material in an organic solvent, water, a pigment dispersion, a colloidal dispersion, or the like may be used. In the present embodiment, the viscosity of the coating solution is preferably 20 mPa · sec or less.

Then, the coating method by the above coating device 1 is demonstrated.
First, the maintenance of the inkjet head 4 is performed by the maintenance device 6. Specifically, the coating liquid is forcibly supplied from the tank 60 to the inkjet head 4 by the pump P2 with the valve B1 closed and the valve B2 opened. At this time, the coating liquid discharged from the inkjet head 4 is received by a catch pan (not shown). Thereby, the inkjet head 4 is filled with the coating liquid, and the inside of the head is evacuated.

  Next, the pump P1 supplies the coating liquid in the auxiliary tank 51 to the coating liquid tank 50 at a predetermined flow rate, and overflows the coating liquid that exceeds a predetermined storage amount. As a result, the coating liquid starts to circulate between the auxiliary tank 51 and the coating liquid tank 50.

Next, the valve B <b> 2 is closed and the valve B <b> 1 is opened so that the coating liquid can be supplied from the coating liquid tank 50 to the inkjet head 4.
Next, formation of the coating liquid film H <b> 1 is started by starting the injection of the coating liquid from the inkjet head 4 under the predetermined injection conditions while transporting the workpiece H at a predetermined speed by the transport device 2. In the present embodiment, the formation of the coating liquid film H1 is preferably performed in a wet state, and the thickness of the coating liquid film H1 is preferably 40 μm or less.

  At the same time, the heat exchanger 7 starts temperature control for the coating liquid in the flow path R1 based on the temperature measured by the temperature sensor 45. Thereby, the coating liquid temperature in the inkjet head 4 is kept constant.

  On the other hand, at this time, as described above, the liquid level E of the coating liquid tank 50 is kept constant because the coating liquid overflows from the coating liquid tank 50 in excess of the predetermined storage amount.

  According to the coating apparatus 1 described above, since the coating is performed by the inkjet head 4 while the liquid level E of the coating liquid tank 50 that supplies the coating liquid to the inkjet head 4 is kept constant, the coating liquid flows. The pressure loss when moving in the road can be kept constant. In addition, since the application is performed by the inkjet head 4 while keeping the temperature of the coating solution inside the inkjet head 4 constant, the viscosity of the coating solution can be kept constant. Accordingly, even during continuous injection for a long time, the injection amount can be made constant as compared with the conventional case.

  Moreover, since the overflowed coating liquid is collected by the auxiliary tank 51 and re-supplied to the coating liquid tank 50 while the coating liquid is overflowed from the coating liquid tank 50, waste of the coating liquid due to overflow can be eliminated.

  It should be noted that the present invention should not be construed as being limited to the above-described embodiment, and of course can be modified or improved as appropriate.

  For example, in the embodiment described above, the liquid level position E is held constant by overflowing the coating liquid from the coating liquid tank 50. However, the liquid level position E is detected by the liquid level sensor, By controlling the supply amount of the application liquid from the auxiliary tank 51 to the application liquid tank 50 based on the detection result, the liquid surface position E may be kept constant, or the decrease amount of the application liquid in the application liquid tank 50 The liquid level E may be kept constant by raising the coating liquid tank 50 by a predetermined tank raising means based on the above. Here, as a technique for detecting the decrease amount of the coating liquid, a technique for detecting by a liquid level sensor, a technique for calculating from the coating conditions and the coating time, or the like can be used.

  In addition, the inkjet head 4 has been described as injecting the coating liquid onto the coating object H transported between the backup roller 20 and the winding device. It is good also as injecting.

  Further, although the heat exchanger 7 has been described as being provided in the flow path R <b> 1, it may be provided in the coating solution tank 50 or may be provided in the inkjet head 4. Further, when the heat exchanger 7 is provided in the coating solution tank 50, it may be provided outside the coating solution tank 50 as long as the coating solution inside the coating solution tank 50 can be heated and cooled. It may be provided. Similarly, when the heat exchanger 7 is provided in the inkjet head 4, it may be provided outside or inside the inkjet head 4 as long as the coating liquid in the inkjet head 4 can be heated and cooled. Also good.

  Further, the temperature sensor 45 has been described as being provided in each inkjet head 4, but may be provided in only one of the plurality of inkjet heads 4. In addition, although it has been described that the coating liquid supply device 5 is connected to each inkjet head 4, only one of the plurality of inkjet heads 4 may be connected.

  Subsequently, examples suitable for the present embodiment will be described, but the present invention is not limited thereto.

[Preparation of workpiece H]
A polyethylene terephthalate film having a thickness of 100 μm, a width of 600 mm, and a length of 5500 m was prepared as an object to be coated H.

[Preparation of coating solution]
Polyvinyl alcohol was dissolved in a solvent in which pure water and methanol were mixed at a mass ratio of 70:30 to prepare a coating solution. In addition, it was 5.0 mPa * s when the viscosity was measured about this coating liquid using the B-type viscosity meter at the temperature of 25 degreeC.

[Coating]
The above coating object H and the coating liquid were applied to the coating apparatus 1 in the above embodiment, and coating was continuously performed for 5000 m under the conditions shown in Table 1 below.

  In Table 1, “Do not use overflow” means that the application liquid is not supplied from the auxiliary tank 51 to the application liquid tank 50 and the application liquid is not overflowed from the application liquid tank 50. On the other hand, “overflow use” means that the coating liquid is supplied from the auxiliary tank 51 to the coating liquid tank 50 to overflow the coating liquid from the coating liquid tank 50. Further, “(not using a constant coating liquid temperature)” means that the coating liquid temperature in the inkjet head 4 is not controlled without operating the heat exchanger 7. On the other hand, “use (constant coating liquid temperature)” means that the heat exchanger 7 is operated to control the coating liquid temperature in the inkjet head 4 to be constant.

  Of the coating conditions other than those shown in Table 1, the droplet velocity immediately after ejection from the nozzle discharge port 42a was 7 m / sec. Moreover, the conveyance speed of the to-be-coated object H was 25 m / min. The diameter of the nozzle discharge port 42a was 0.04 mm, the average discharge amount per droplet of the coating liquid was 50 pl, the pitch of the nozzle discharge ports 42a was 0.07 mm, and the number of nozzles was 500. The ejection conditions from the nozzle discharge port 42a were set to 4 μm when the ejected coating droplet spread with a uniform thickness in the width direction of the coating liquid film H1 (front and back direction in FIG. 1). Further, as shown in FIG. 4A, a plurality of inkjet heads 4 are arranged in a staggered manner so that a coating liquid film H1 having a width of 550 mm can be obtained. The temperature of the coating solution stored in the tank 60 and the coating solution tank 50 was 25 ° C.

[Evaluation of application]
The film thickness fluctuation ratio was evaluated for the obtained coating liquid film H1.
Specifically, first, according to the following formula (1), the film thickness increases in the coating portion of the coating liquid film H1 coated with a length of 5000 m and each coating portion of 1000, 2000, 3000, 4000, 5000 m. The ratio was measured. In addition, as a film thickness used for Formula (1), the value which measured the film thickness of 54 points | pieces by 10 mm space | interval except 10 mm of both ends in the width direction of the coating liquid film H1, and also the length of the coating liquid film H1. Five points were sampled at 100 mm intervals in the direction (conveyance direction X), and the values of these five points were averaged and used.
Film thickness fluctuation ratio = (film thickness of each application part-film thickness at the start of application) / film thickness at the start of application x 100 [%] (1)

Then, the film thickness variation ratio was evaluated depending on how much the thickness of each coated portion varied with respect to the leading portion. The closer this value is to 0, the higher the accuracy and the better, but generally it is considered that the tolerance is within ± 2%.
Therefore, the evaluation is ○ when it is within ± 2%, and × when this range is exceeded. The results are shown in Table 1 above.

  From the results of Table 1, it was confirmed that in the examples according to the present invention, the variation in the film thickness was small and the injection amount was kept constant.

It is a conceptual diagram which shows schematic structure of the coating device which concerns on this invention. It is a perspective view which shows an inkjet head. It is a figure for demonstrating the arrangement | positioning method of an inkjet head. It is a figure for demonstrating the arrangement | sequence method of an inkjet head. It is a block diagram which shows schematic structure of the coating device which concerns on this invention. It is a figure for demonstrating the control method of the coating liquid temperature in an inkjet head.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Coating device 4 Inkjet head 45 Temperature sensor 50 Coating liquid tank (liquid level holding means)
51 Auxiliary tank (coating liquid supply means, coating liquid recovery means)
7 Heat exchanger (temperature holding means, temperature control means)
H Coating object H1 Coating liquid film

Claims (14)

In a coating method for forming a coating liquid film on the coating object by ejecting the coating liquid as droplets from the inkjet head to the coating object to be transported,
The liquid level position of the coating liquid tank for supplying the coating liquid to the inkjet head is kept constant, and the coating is performed by the inkjet head while the coating liquid temperature inside the inkjet head is kept constant. Application method. The coating method according to claim 1,
A coating method, wherein the liquid surface position is kept constant by overflowing a coating liquid that exceeds a predetermined storage amount from the coating liquid tank. The coating method according to claim 2, wherein
A coating method comprising collecting the coating solution overflowed from the coating solution tank and re-supplying the coating solution to the coating solution tank. The coating method according to claim 1,
The liquid level position is detected by a liquid level sensor, and the liquid level position is kept constant by controlling the supply amount of the coating liquid to the coating liquid tank based on the detection result. Method. The coating method according to claim 1,
A coating method characterized in that the liquid surface position is kept constant by raising the coating liquid tank based on a decrease amount of the coating liquid in the coating liquid tank. In the coating method as described in any one of Claims 1-5,
The liquid level position is kept constant at a height of (ejection surface height−600 mm) <liquid surface position <(ejection surface height + 600 mm) with respect to the coating liquid ejection surface in the inkjet head. A coating method characterized by the above. In the coating method according to any one of claims 1 to 6,
The temperature of the coating liquid inside the inkjet head is detected, and based on the detection result, the coating liquid is detected in any of the inkjet head, the coating liquid tank, and the flow path from the inkjet head to the coating liquid tank. A coating method characterized in that the temperature of the coating liquid in the inkjet head is kept constant by performing temperature control. In a coating apparatus for forming a coating liquid film on an object to be coated by ejecting the coating liquid as droplets on the object to be transported,
An inkjet head for injecting a coating liquid onto the object to be coated;
A coating solution tank for supplying a coating solution to the inkjet head;
Liquid level holding means for holding the liquid level position of the coating liquid tank constant;
A coating apparatus comprising: a temperature holding unit that keeps the temperature of the coating solution inside the inkjet head constant. The coating apparatus according to claim 8, wherein
A coating solution supply means for supplying the coating solution to the coating solution tank;
The liquid level holding means is
A coating apparatus, wherein the liquid surface position is kept constant by overflowing a coating liquid that exceeds a predetermined storage amount from the coating liquid tank. The coating apparatus according to claim 9, wherein
The coating liquid supply means includes
A coating apparatus comprising: a coating liquid recovery unit that recovers the coating liquid that has overflowed from the coating liquid tank and supplies the coating liquid again to the coating liquid tank. The coating apparatus according to claim 8, wherein
A coating solution supply means for supplying the coating solution to the coating solution tank;
The liquid level holding means is
A liquid level sensor for detecting the liquid level position;
A coating apparatus comprising: a supply amount control unit configured to control a supply amount of the coating liquid from the coating liquid supply unit to the coating liquid tank based on a detection result by the liquid level sensor. The coating apparatus according to claim 8, wherein
The liquid level holding means is
A decrease amount detecting means for detecting a decrease amount of the coating liquid in the coating liquid tank;
And a tank raising means for raising the coating liquid tank based on a detection result by the reduction amount detecting means. In the coating device as described in any one of Claims 8-12,
The liquid level position is
The coating is characterized by being held constant at a height of (ejection surface height−600 mm) <liquid surface position <(ejection surface height + 600 mm) relative to the ejection surface of the coating liquid in the inkjet head. apparatus. In the coating device as described in any one of Claims 8-13,
The temperature holding means is
A temperature sensor for detecting a coating liquid temperature inside the inkjet head;
Temperature control means for controlling the temperature of the coating liquid in any of the ink jet head, the coating liquid tank, and the flow path from the inkjet head to the coating liquid tank based on the detection result of the temperature sensor. An applicator characterized by that.

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