JP5163532B2 - Coating liquid coating method and coating system - Google Patents

Description

  The present invention relates to a coating method and a coating system using a solvent-based coating solution, and more particularly to the concentration of the coating solution and the uniformization of the coating film thickness.

  In recent years, with the improvement in performance of optical functional films, there has been a growing demand for uniform coating thickness and film thickness. In order to make the film thickness uniform, that is, to prevent film thickness unevenness, it is necessary to apply with high precision while maintaining the concentration of the solid content of the coating solution supplied over time.

  Hereinafter, the concentration of the solid content of the coating solution is referred to as the concentration of the coating solution (coating solution concentration).

  Typical coating apparatuses used for the production of the optical functional film include a bar coating apparatus, a roll coating apparatus, and a gravure coating apparatus. However, in these coating apparatuses, since the coating liquid is scraped from the coating liquid reservoir by a bar or roll and applied to the support, the solvent is sequentially evaporated from the portion of the coating liquid reservoir that is in contact with air. The concentration of the coating solution in the liquid reservoir increases. For this reason, there exists a problem that the film thickness of a coating film changes with time.

  In order to solve the above problem, methods for suppressing evaporation of the solvent have been proposed.

  For example, the density of the coating liquid flowing in the liquid feeding pipe is measured in-line, the density difference between the measured measurement density and the prescribed density of the coating liquid defined in advance is calculated, and the density measurement position is set so that the density difference is eliminated. A coating method has been proposed in which a density adjusting liquid is added into the upstream liquid supply pipe (see, for example, Patent Document 1).

  In addition, it has been proposed to cover the gas-liquid interface of the coating liquid reservoir except the contact area between the coating member such as a bar or roll and the support with an air inflow prevention cover to suppress evaporation of the solvent (for example, Patent Document 2).

JP 2005-279342 A JP 2003-340334 A

  Patent Document 1 measures the density of the coating liquid flowing in the liquid feeding pipe in-line using a Coriolis mass flow meter, calculates the density difference between the measured density and the prescribed density of the coating liquid defined in advance, In this method, the density adjusting liquid is added to the liquid feeding pipe so as to eliminate the density difference. However, this method can be used only when the solvent contained in the coating liquid is composed of only one kind, and cannot be used for the coating liquid composed of two or more kinds of solvents. Moreover, there is a concern that the use of the Coriolis mass flow meter leads to an increase in the cost of the apparatus.

  Hereinafter, a coating solution containing only one solvent is also referred to as a single solvent coating solution, and a coating solution containing two or more solvents is also referred to as a mixed solvent coating solution.

  In Patent Document 2, the air-liquid interface of the coating liquid reservoir except for the contact area between the coating member such as a bar or roll and the support is covered with an air inflow prevention cover, and further in a space covered with the air inflow prevention cover. In this method, an inert gas is filled to suppress evaporation of the solvent. However, since it does not completely block contact with air, it is not possible to prevent evaporation of the solvent in the coating liquid reservoir, and it is possible to prevent an increase in the concentration of the coating liquid in the coating liquid reservoir. There wasn't.

  The present invention has been made in view of the above situation, and it is possible to prevent an increase in the concentration of the coating liquid even in the case of a coating liquid having two or more kinds of solvents with a simple method and configuration, and a uniform film thickness. It is an object of the present invention to provide a coating method and a coating system that can stably form a coating film without unevenness.

  The above object is achieved by the following method and configuration.

1. In a coating method in which a long coating to be conveyed is applied by feeding a solvent-based coating solution containing two or more solvents to a coating apparatus and applying it.
Calculating the total evaporation amount of each of the two or more types of solvents from the coating apparatus and the evaporation amount by simulation using a simulation means;
Wherein for each of two or more solvents, the solvent in an amount corresponding to the calculated evaporation Hatsuryou, and supplied to the coating liquid which is fed to the coating apparatus,
A coating method comprising changing the concentration of the coating solution to be fed.

  2. Coating is performed using a coating solution supplemented with the amount of solvent calculated in the simulation, and the film thickness of the coating film is measured immediately after coating and after drying, and the concentration of the coating solution is determined based on the measurement result. And calculating a difference between the concentration of the coating liquid and a predetermined reference coating liquid concentration and a solvent correction amount corresponding to the difference, and determining a solvent replenishment amount based on the simulation based on the solvent correction amount. 2. The coating method according to 1 above, wherein the coating method is changed.

  3. 3. The coating method according to 1 or 2, wherein the replenishment ratio for each solvent in the replenishment of the solvent is a ratio of the evaporation amount for each solvent calculated by the simulation.

4). In a coating system for forming a coating film by feeding a coating solution of a solvent system containing two or more solvents to a coating device and applying it to a long support to be conveyed.
A simulation means for performing a simulation for calculating a total amount of the evaporation amount and the evaporation amount of each of the two or more types of solvents from the coating apparatus;
Solvent replenishing means for replenishing the coating liquid fed to the coating apparatus with the two or more solvents ;
Control means for controlling the replenishment amount of each of the two or more solvents in the solvent replenishing means,
An application system characterized in that an amount of solvent corresponding to the calculated evaporation amount for each solvent is replenished to the applied coating solution, and the concentration of the applied coating solution is changed.

5. Film thickness measuring means for measuring the film thickness of the coating film immediately after coating and after coating using the coating liquid supplemented with the amount of solvent calculated in the simulation,
Based on the result of the measurement, a concentration calculating means for calculating the concentration of the coating liquid;
A solvent correction amount calculating means for calculating a difference between the concentration of the coating liquid and a predetermined reference coating liquid concentration and a solvent correction amount corresponding to the difference;
5. The coating system according to 4, wherein the control unit changes a replenishment amount of the solvent based on the simulation based on the correction amount of the solvent.

  6). 6. The coating system according to 4 or 5, wherein the replenishment ratio for each solvent in the replenishment of the solvent is a ratio of the evaporation amount for each solvent calculated by the simulation.

  7). The coating system according to any one of 4 to 6, wherein the coating liquid is a coating liquid for producing an optical film functional film.

  8). The coating system according to any one of 4 to 7, wherein the coating device is any one of a bar coating device, a roll coating device, and a gravure coating device.

  As described above, simulation of evaporation amount, calculation of evaporation amount for each solvent, and supply of corresponding solvent amount as replenishment amount, change in concentration of mixed solvent type coating liquid containing multiple solvents Reduction can be achieved.

  Furthermore, the actual coating is performed, the coating solution concentration is calculated based on the measured value of the film thickness of the coating film, and the amount of solvent replenishment calculated in the simulation is corrected, so that the coating solution concentration can be applied over time. It becomes possible to adjust to the liquid concentration. Thereby, it is possible to form a coating film having a uniform film thickness.

1 is a conceptual diagram of a coating system to which a coating liquid coating method according to the present invention is applied. It is a figure which shows the change of the coating liquid density | concentration with respect to elapsed time. It is a figure which shows the comparison of the simulation of the evaporation amount for every solvent before correcting a film heat transfer coefficient, and after correcting based on the evaporation amount in an actual system.

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

  FIG. 1 is a conceptual diagram showing an example of a coating system 20 to which a coating liquid coating method according to the present invention is applied. In the present embodiment, the coating system 20 is an optical functional film coating system.

  The long support 10 wound in a roll shape is fed out from the unwinding portion 10A in the direction of arrow X by a driving means (not shown) and conveyed, and a coating solution is applied by the coating device 210 to form a coating film. The support 10 on which the coating film has been formed is dried by the drying device 50, passed through the UV irradiation device, and then wound around the winding unit 10B.

  In the present embodiment, the coating device 210 is a roll coating device, and the coating solution is a mixed solvent coating solution having two types of solvents (A solvent and B solvent). The method of the coating apparatus and the number of types of solvents are not limited to this, and for example, a bar coating apparatus, a gravure coating apparatus, etc. are preferably used for the production of an optical functional film.

  The coating device 210 is scraped from the coating liquid reservoir 211 by the rotation of the coating roll 214, the guide rolls 217a, 217b, the coating liquid reservoir (coating liquid pan) 211 provided below the coating roll 214, and the coating roll 214. And a blade 216 for scraping off an excessive coating liquid before coating.

  About the lower half of the coating solution roll 214 is immersed in the coating solution filled in the coating solution reservoir 211.

  The coating liquid reservoir 211 is provided with a temperature sensor 213 for detecting the temperature of the coating liquid and a temperature control device 212 to control the temperature of the coating liquid in the coating liquid reservoir. The temperature control prevents the coating liquid temperature from increasing and the amount of solvent evaporation from increasing, and the coating liquid temperature from decreasing to prevent the solid content in the coating liquid from precipitating. In the present embodiment, a thermocouple is used for the temperature sensor 213 and a system in which cooling water or hot water is circulated in the coating liquid reservoir 211 is used for the temperature control device 212. However, the present invention is not limited to this.

  The coating film is formed by applying the coating liquid in the coating liquid reservoir 211 by the rotation of the coating roll 214 while the support 10 to be conveyed is pressed against the coating roll 214 by the guide rolls 217a and 217b that are rotatably supported. It is carried out by scraping it up and applying it onto the application surface of the support 10. The excess coating liquid that has been scraped is scraped off by the blade 216 before coating.

  In the present embodiment, the application roll 214 is rotationally driven in the same direction as the conveyance direction of the support 10.

  The coating liquid is stored in the coating liquid tank 231, and is fed to the coating liquid reservoir 211 of the coating apparatus 210 via the liquid feeding pipe 234 by a pump P1 that is a coating liquid feeding means. The two kinds of solvents are respectively stored in the solvent tanks 232 and 233, and are fed to the liquid feeding pipe 234 by the pumps P2 and P3 which are solvent replenishing means, and are replenished to the coating liquid to be fed. In addition to the pumps (P1, P2, P3), a control valve (not shown) or the like may be used for the coating liquid feeding means and the solvent supply means. For the pumps (P1, P2, P3), a diaphragm pump, a gear pump, and a plunger pump are preferably used in order to accurately control the liquid feeding amount and the replenishing amount.

  The control unit 241 that is a control unit controls the pumps P1, P2, and P3, and controls the liquid feeding amount (replenishment amount). The calculation unit 242 has a function of a simulation unit, which will be described later, and various numerical value and quantity calculation functions.

  On the downstream side of the coating apparatus 210, film thickness meters 245a and 245b serving as film thickness measuring means are provided, and the film thickness of the coating film on the support on which the coating film is formed and conveyed is measured. The film thickness meter 245a measures the wet film thickness immediately after application, that is, before drying, and the film thickness meter 245b measures the dry film thickness after drying by the drying device 50. The measurement data is sent to the calculation unit 242.

  In the present embodiment, the concentration of the coating solution is represented by the ratio (percentage) of the mass of the solid content per unit mass of the coating solution. That is, the concentration of the coating solution is a mass percent concentration. Further, the evaporation amount, the liquid feeding amount, and the replenishment amount are represented by mass. The mass of the evaporation amount, the liquid supply amount, and the replenishment amount can be converted into a volume.

  Next, replenishment of the solvent will be described.

  As described above, in the coating apparatus 210, the solvent is sequentially evaporated from the portion of the coating liquid reservoir 211 that is in contact with the air, and the concentration of the coating liquid in the coating liquid reservoir 211 increases. For this reason, as a result, the film thickness of the coating film changes with time.

  On the other hand, in the present invention, in order to suppress an increase in the concentration of the coating solution, a solvent corresponding to the evaporation amount of the solvent is supplied. The amount of evaporation of the solvent is calculated by simulation in the calculation unit 242 having the function of simulation means.

  In the simulation, the vapor pressure of each solvent component contained in the coating solution is calculated, and the evaporation amount of each solvent per unit time is calculated therefrom.

  Specifically, in the simulation, first, the vapor pressure for each solvent contained in the coating liquid is calculated using the Antoine equation shown in Equation 1.

Number 1
Pn = rn × 10 ⁽ ab− ^{(T + c))}
In Equation 1, Pn is the vapor pressure (pascal, Pa) of the n solvent, rn is the molar fraction in the coating solution of the n solvent, and T is the temperature. In the example of the present embodiment, since the coating liquid contains two types of solvents, A solvent and B solvent, n = A and B. a, b, and c are Antoine constants.

  Next, the evaporation amount per unit area for each solvent is calculated. The evaporation amount is calculated by the equation shown in Formula 2.

Number 2
Wn = (h × Mn × Pn) / (0.45 × Mair × (1.0132 × 10 ⁵ −Pn))
In Equation 2, Wn is the evaporation amount of the n solvent, h is a film heat transfer coefficient indicating the ease of heat transfer between the liquid and the gas (air), Mn is the molecular weight of the n solvent, and Mair is the molecular weight of the air. is there.

  Next, by converting the amount of evaporation per unit area for each solvent calculated by Equation 2 into the area of the portion of the coating liquid reservoir 211 that is in contact with the air, each solvent that evaporates from the coating liquid reservoir 211. The amount of evaporation per unit time (total amount of evaporation) is calculated.

  In the simulation, the amount of solvent evaporation is calculated in consideration of the material balance of the coating liquid reservoir 211.

  The total evaporation amount for each solvent calculated in the simulation is set as a replenishment amount for each solvent corresponding to the solvent, and is sent from the calculation unit 242 to the control unit 241 as replenishment amount data. Based on the replenishment amount data, the control unit 241 controls the pumps P2 and P3 using the amount of solvent corresponding to the total evaporation amount for each solvent as the replenishment amount, and sends the liquid from the solvent tanks 232 and 233 via the liquid feed pipe 234. Replenish the applied liquid. Thereby, the density | concentration of the coating liquid sent to the coating liquid storage part 211 is changed.

  As described above, the evaporation amount is simulated, the evaporation amount for each solvent is calculated, and the corresponding solvent amount is used as the replenishment amount, that is, the evaporation amount ratio for each solvent is used as the replenishment ratio for each solvent. To change the concentration of the coating solution to be fed. As a result, it is possible to reduce the concentration change of the mixed solvent coating liquid containing a plurality of solvents in the coating liquid reservoir 211.

  Here, in application | coating with the coating device 210, what is called entrained air which the air around the support body 10 moves with the conveyance of the support body 10 arises. For this reason, the film heat transfer coefficient h changes, and a deviation may occur between the evaporation amount calculated by the simulation and the actual evaporation amount (actual evaporation amount). For this reason, in order to reduce the concentration change of the coating solution, it is preferable to correct the solvent replenishment amount as a result of the simulation based on the actual evaporation amount.

  Next, correction of the solvent replenishment amount will be described.

  First, coating is performed on the support 10 with a coating solution in which each solvent is replenished with the replenishment amount calculated in the above-described simulation to form a coating film.

  Next, the wet film thickness 245a is measured immediately after coating on the support 10, that is, before being dried, and the dry film thickness after drying is measured by the film thickness meter 245b with the drying device 50. In this embodiment, the film thickness meters 245a and 245b are non-contact type infrared film thickness meters RX-10 (manufactured by Kurashiki Boseki Co., Ltd.) adopting a transmission optical system. However, the present invention is not limited to this method. Alternatively, a method using optical interference may be used.

  The measurement result of the film thickness is sent to the calculation unit 242. The concentration of the coating solution supplemented with each of the solvents is calculated by the calculation unit 242 based on the measurement result. The concentration is calculated from the ratio of the dry film thickness to the wet film mass.

  Next, a standard deviation of the reference coating solution is compared with the calculated concentration to calculate a concentration deviation. Based on the calibration curve graph data based on the concentration deviation, a solvent replenishment correction amount necessary to eliminate the deviation is calculated. The correction amount can be calculated by considering all the solvents contained in the coating solution as one type of solvent (for example, A solvent). For example, all the solvents contained in the coating liquid can be regarded as a solvent having the largest molar fraction among the solvents (for example, the A solvent).

  The calibration curve graph is a graph representing the relationship between the coating solution concentration and the solvent replenishment amount obtained in advance by experiments or the like. As described above, when all the solvents contained in the coating liquid are regarded as one type of solvent in total, the solvent of the calibration curve graph is one type, for example, the A solvent.

  Based on the correction amount, a total replenishment amount (corrected total replenishment amount) obtained by correcting the total replenishment amount of the total solvent replenishment amounts is calculated.

  The corrected total replenishment amount is set as the evaporation amount per unit time, the evaporation amount per unit area is calculated backward, and the equation is applied to Equation 2 to calculate the modified film heat transfer coefficient hs using the film heat transfer coefficient h as a variable. . In the calculation of the film heat transfer coefficient hs, the solvent can be one type, for example, the A solvent.

  Next, the film heat transfer coefficient hs is applied to Equation 2, and the corrected total evaporation amount (corrected total evaporation amount) for each solvent is calculated according to the above-described simulation. The calculated corrected total evaporation amount for each solvent is set as a corrected replenishment amount (corrected replenishment amount) for each solvent, and is sent from the calculation unit 242 to the control unit 241 as corrected replenishment amount data. Based on the corrected replenishment amount data, the control unit 241 controls the pumps P2 and P3 with the amount of solvent corresponding to the corrected total evaporation amount for each solvent as the corrected replenishment amount. Then, replenishment is performed by changing the replenishment amount of the solvent to the coating liquid to be fed.

  FIG. 2 is a diagram showing changes in the coating solution concentration with respect to elapsed time. A line D1 indicates a change in the concentration of the coating solution when the solvent is not replenished with respect to the evaporation of the solvent from the coating solution reservoir 211. Since the coating solution concentration increases with the passage of time, the film thickness of the coating also changes and unevenness occurs.

  A line D2 is a case where the evaporation amount of the solvent is obtained only by the above-described simulation and the solvent is replenished, and shows a change before the replenishment amount is corrected. Since the solvent is replenished, the coating solution concentration rises more slowly than the line D1, but there is a deviation from the reference coating solution concentration. This is because there is a difference between the evaporation amount in the simulation and the evaporation amount in the actual system.

  The line D3 is applied with the coating liquid in the line D2, the film thickness is measured, the boundary film heat transfer coefficient h is corrected to hs, and the evaporation amount for each solvent is simulated to calculate the coating liquid concentration and the reference coating concentration. This is a case where the deviation is corrected. Since the replenishment amount of the solvent is corrected based on the evaporation amount in the actual system, the coating solution concentration is within the concentration range corresponding to the predetermined allowable film thickness range with respect to the elapsed time. And a coating film having a uniform film thickness can be obtained. The line D3 in the figure is shown linearly, but there may be fluctuations within an allowable range.

  FIG. 3 is a diagram showing a comparison of simulations of the evaporation amount for each solvent before the boundary film heat transfer coefficient h is corrected and after the correction based on the evaporation amount in the actual system. A line EA1 indicates the evaporation amount of the solvent A, and a line EB1 indicates the evaporation amount with respect to the elapsed time when the evaporation amount simulation is performed using the film heat transfer coefficient h before the correction of the solvent B. A line EA2 indicates the evaporation amount with respect to the elapsed time when the evaporation amount is simulated using the modified film heat transfer coefficient hs of the solvent A, and a line EB2 indicates the solvent B.

  Thus, by applying and correcting the film heat transfer coefficient h based on the evaporation amount in the actual system, it is possible to obtain a simulation that approximates the actual system, and the evaporation amount that approximates the actual system (Line EA2, Line EB2) can be obtained. Therefore, the subsequent simulation can be made in accordance with the actual system, and the coating solution concentration can be easily stabilized.

  As described above, the actual coating is performed, the coating solution concentration is calculated based on the actually measured value of the coating film thickness, and the solvent replenishment amount calculated in the simulation is corrected. Can be approximated to the reference coating solution concentration. As a result, it is possible to form a coating film having a uniform thickness.

  Further, by modifying the film heat transfer coefficient h according to the actual system, the subsequent simulation can be made closer to the actual system. Thereby, it becomes easy to prevent an increase in the concentration of the coating solution, and it is possible to stably form a coating film having a uniform thickness.

<Example>
Using the coating system 20 shown in FIG. 1, the evaporation amount from the coating liquid reservoir 211 is simulated as described above, and the simulation is performed by correcting the evaporation amount for each solvent. Coating was performed on the support 10 while replenishing the solvent, and the change in the concentration of the coating solution and the change in the coating film were evaluated. As a comparative example, the case where solvent replenishment was not performed, that is, a measure against evaporation was not evaluated.

(Application conditions)
Initial concentration of coating solution: 20% by mass of solid content
Solvent: MEK (methyl ethyl ketone), PGME (propylene glycol monomethyl ether)
Solvent ratio: MEK: PGME = 30: 70
Coating solution mass in coating solution reservoir 211: 0.1 kg
Support 10 total length: 330 m
Support 10 conveyance speed: 10 m / min
Application roll 214 diameter: 5 cm
Coating roll 214 peripheral speed, rotational direction: peripheral speed; 10 m / min, rotational direction; same direction as transport direction of support 10 (evaluation)
Under the above conditions, both the examples and the comparative examples were applied for 30 minutes, and the coating solution concentrations at the start and after 30 minutes were compared with the film thickness of the coating film. The film thicknesses of the coatings were compared by a ratio with the film thickness at the start of application being 1.

(result)
Table 1 shows the results.

  As shown in Table 1, in the examples, the concentration of the coating solution did not change, the film thickness was constant, and no coating unevenness occurred. On the other hand, in the comparative example, the coating solution concentration increased, the film thickness increased, and coating unevenness occurred. Thus, the effect of the present invention was confirmed.

DESCRIPTION OF SYMBOLS 10 Support body 10A Unwinding part 10B Winding part 20 Coating system 50 Drying apparatus
60 UV irradiation apparatus 210 Coating apparatus 211 Coating liquid reservoir 212 Temperature controller 213 Temperature sensor 214 Coating roll 216 Blade 217a, 217b Guide roll 231 Coating liquid tank 232, 233 Solvent tank 234 Liquid supply piping 241 Control section 242 Calculation section 245a, 245b Film thickness meter

Claims (8)

In a coating method in which a long coating to be conveyed is applied by feeding a solvent-based coating solution containing two or more solvents to a coating apparatus and applying it.
Calculating the total evaporation amount of each of the two or more types of solvents from the coating apparatus and the evaporation amount by simulation using a simulation means;
Wherein for each of two or more solvents, the solvent in an amount corresponding to the calculated evaporation Hatsuryou, and supplied to the coating liquid which is fed to the coating apparatus,
A coating method comprising changing the concentration of the coating solution to be fed.   Coating is performed using a coating solution supplemented with the amount of solvent calculated in the simulation, and the film thickness of the coating film is measured immediately after coating and after drying, and the concentration of the coating solution is determined based on the measurement result. And calculating a difference between the concentration of the coating liquid and a predetermined reference coating liquid concentration and a solvent correction amount corresponding to the difference, and determining a solvent replenishment amount based on the simulation based on the solvent correction amount. The coating method according to claim 1, wherein the coating method is changed.   3. The coating method according to claim 1, wherein a replenishment ratio for each solvent in replenishing the solvent is a ratio of an evaporation amount for each solvent calculated by the simulation. In a coating system for forming a coating film by feeding a coating solution of a solvent system containing two or more solvents to a coating device and applying it to a long support to be conveyed.
A simulation means for performing a simulation for calculating a total amount of the evaporation amount and the evaporation amount of each of the two or more types of solvents from the coating apparatus;
Solvent replenishing means for replenishing the coating liquid fed to the coating apparatus with the two or more solvents ;
Control means for controlling the replenishment amount of each of the two or more solvents in the solvent replenishing means,
An application system characterized in that an amount of solvent corresponding to the calculated evaporation amount for each solvent is replenished to the applied coating solution, and the concentration of the applied coating solution is changed. Film thickness measuring means for measuring the film thickness of the coating film immediately after coating and after coating using the coating liquid supplemented with the amount of solvent calculated in the simulation,
Based on the result of the measurement, a concentration calculating means for calculating the concentration of the coating liquid;
A solvent correction amount calculating means for calculating a difference between the concentration of the coating liquid and a predetermined reference coating liquid concentration and a solvent correction amount corresponding to the difference;
The coating system according to claim 4, wherein the control unit changes a replenishment amount of the solvent based on the simulation based on the correction amount of the solvent.   The coating system according to claim 4 or 5, wherein the replenishment ratio for each solvent in the replenishment of the solvent is a ratio of the evaporation amount for each solvent calculated by the simulation.   The coating system according to claim 4, wherein the coating liquid is a coating liquid for producing an optical film functional film.   The coating system according to any one of claims 4 to 7, wherein the coating device is any one of a bar coating device, a roll coating device, and a gravure coating device.

Images