JP5255332B2 - Application method of water-based paint - Google Patents

Description

  The present invention relates to a method for applying a water-based paint such as a water-based resist ink to a substrate such as a printed wiring board.

  Conventionally, a roll coat has been adopted as a method for applying a paint such as a resist ink to a substrate such as a printed wiring board.

  In the conventional roll coating, a pair of coating rolls having a horizontal rotation axis are arranged in the vertical direction, the coating roll is supplied while rotating the coating roll, the substrate is transported in the horizontal direction, and the coating roll Passing between them is done. In addition, a pair of application rolls having a horizontal rotation axis are arranged in parallel in the horizontal direction, and the coating roll is supplied while rotating the application roll, and the substrate is conveyed in the vertical direction between the application rolls. It is also proposed to let it pass. By such a method, it becomes possible to apply | coat a coating material simultaneously on the upper and lower surfaces of a base material (refer patent document 1).

  In recent years, attempts have been made to suppress the use of organic solvents in paints such as resist inks for printed wiring boards and to use water-based paints. As a result, various problems such as occupational safety and health problems due to organic solvents, environmental pollution problems, and risk of fire occurrence during roll coating and subsequent processes are being sought.

  However, when roll coating is adopted for application of water-based paint, if the paint supplied to the surface of the application roll remains without being applied to the substrate, the solvent water evaporates from the paint. There is a problem in that the viscosity of the paint rises and unevenness of the paint on the base material is likely to occur when the paint is applied to the base material. In particular, in roll coating, since coating rolls having a length dimension larger than the width dimension of the substrate are usually used in order to enable coating on a substrate having various dimensions, both end portions of the coating roll are used. In this case, the remaining of the coating tends to occur, and the increase in the viscosity of the coating due to the remaining coating becomes a problem. When an organic solvent is used as the solvent of the paint, the above problem can be avoided by using a solvent having a composition that does not volatilize easily, but such a countermeasure cannot be performed with the water-based paint. It is.

In addition, a doctor blade is usually used to scrape excess paint on the surface of the application roll during roll coating, but the paint accumulated on the doctor blade may drop, causing uneven coating and poor coating. .
Japanese Patent Laid-Open No. 9-290191

  The present invention has been made in view of the above points, and an object of the present invention is to provide a method for applying a water-based paint for uniformly applying an aqueous solvent onto a surface of a substrate by roll coating.

  The coating method of the water-based paint according to the present invention includes a pair of coating rolls 2 arranged in parallel such that the rotation axis thereof is perpendicular to the horizontal plane or is inclined with respect to the horizontal plane. A water-based paint is supplied to the surface of the coating roll 2 from above and the base material 1 passes between the pair of coating rolls 2 so that the water-based paint is applied to the surface of the base material 1. .

  According to the present invention, the aqueous coating material supplied to the coating roll 2 is applied to the base material 1 while flowing down along the surface of the coating roll 2, whereby the aqueous coating material is applied to the base material 1. In addition, since the water-based paint that has not been applied to the base material 1 falls from the lower end of the application roll 2 without remaining on the application roll 2, the water-based paint does not remain on the surface of the application roll 2 without being applied, An increase in the viscosity of the aqueous paint due to the volatilization of the solvent from the aqueous paint on the surface of the coating roll 2 is suppressed.

  Further, when the doctor blade 3 is used to level the water-based paint on the surface of the coating roll, the water-based paint scraped off by the doctor blade 3 also falls downward along the doctor blade 3. The occurrence of coating unevenness and poor coating due to the overflow of the water-based paint accumulated on the doctor blade 3 and falling is prevented.

  In the present invention, after being supplied to the surface of the application roll 2, the water-based paint that has not been applied to the substrate 1 is collected below the application roll 2, and this water-based paint is supplied again to the surface of the application roll 2. Is preferred.

  In this case, it is possible to effectively use resources by reusing water-based paint.

  When the water-based paint is collected, it is also preferable to adjust the viscosity of the water-based paint supplied to the surface of the coating roll 2.

  In this case, when the water-based paint is once supplied to the application roll 2 and then recovered and is again supplied to the application roll 2, the solvent evaporates from the water-based paint and the viscosity increases. The viscosity of the water-based paint is adjusted, and the occurrence of uneven coating is prevented.

Moreover, in this invention, the base material 1 is conveyed in the horizontal direction in a state where it stands upright with respect to the horizontal direction, and the upper end side of the coating roll 2 protrudes to the opposite side to the conveyance direction of the base material 1 and the lower end. side is so as to project to the conveying direction of the substrate 1, the axis of rotation of the applicator roll 2 is that provided to be inclined in the transport direction of the substrate 1.

  In this case, the water-based paint on the surface of the coating roll 2 is biased to the side opposite to the conveying direction of the base material 1 by its own weight, and the base material 1 from the surface of the coating roll 2 when the base material 1 passes between the coating rolls 2 The amount of water-based paint supplied to the surface of the water increases. For this reason, the application efficiency of the water-based paint to the base material 1 is improved, and the time required to apply the water-based paint to the base material 1 by increasing the conveyance speed of the base material 1 can be shortened.

  Moreover, in this invention, it is preferable that the organic solvent content in the solvent in a water-based coating material is 10 mass% or less.

  In this case, problems such as occupational safety and health problems caused by organic solvents, environmental pollution problems, and the risk of fire may be sufficiently solved.

  In the present invention, a water-based paint having a viscosity in the range of 100 to 10,000 mPa · s is preferably supplied to the surface of the coating roll 2.

  In this case, the uniform application property of the water-based paint to the substrate 1 is very excellent.

  Moreover, in this invention, it is preferable that the base material 1 is a printed wiring board and a water-system coating material is the aqueous resist ink for resist film formation.

  According to the present invention, since the increase in the viscosity of the water-based paint due to the water-based paint remaining on the coating roll 2 is suppressed, the aqueous solvent can be uniformly applied to the surface of the substrate 1 by roll coating. it can.

  Hereinafter, the best mode for carrying out the present invention will be described.

  FIG. 1 shows a schematic configuration of a coating apparatus (roll coater) used in the present invention. The two coating rolls 2 are installed in parallel so that there is a slight gap between them so that the substrate 1 can pass through. The base material 1 conveyed in the horizontal direction passes between the two application rolls 2, so that the water-based paint is applied to both surfaces of the base material 1.

  The pair of coating rolls 2 has an upper end projecting in the direction opposite to the conveying direction of the substrate 1 and a lower end side of the coating roll 2 projecting in the conveying direction of the substrate 1 so that the rotation axis of the coating roll 2 is It is provided so as to be inclined along the conveyance direction of the substrate 1. In this case, the water-based paint on the surface of the coating roll 2 is biased to the side opposite to the conveying direction of the base material 1 by its own weight, and the base material 1 from the surface of the coating roll 2 when the base material 1 passes between the coating rolls 2 The amount of water-based paint supplied to the surface of the water increases. For this reason, the application efficiency of the water-based paint to the base material 1 is improved, and the time required to apply the water-based paint to the base material 1 by increasing the conveyance speed of the base material 1 can be shortened.

  Note that the rotation axis of the application roll 2 may be inclined in an appropriate direction, for example, along the horizontal direction orthogonal to the conveyance direction of the substrate 1. Further, the rotation axis of the coating roll 2 may be arranged perpendicular to the horizontal plane. When the rotation axis of the coating roll 2 is tilted, the tilt angle is appropriately set so that the water-based paint smoothly flows downward on the surface of the coating roll 2, but preferably this tilt angle is relative to the horizontal plane. In the range of 45 ° to 90 °.

  As this coating roll 2, in order that a coating material is uniformly apply | coated to the base material 1 surface, it is preferable to use the thing which gave the surface the rubber lining. Moreover, it is preferable that a plurality of grooves in the direction along the circumferential direction for holding the coating material is formed on the surface of the coating roll 2 from one end to the other end of the coating roll 2.

  A doctor blade 3 is provided in the vicinity of each coating roll 2. The doctor blade 3 levels the water-based paint on the surface of each coating roll 2 and scrapes off the excess water-based paint.

  Below the lower ends of the coating roll 2 and the doctor blade 3, a collection tank 7 for receiving the water-based paint that has flowed down from the coating roll 2 and the doctor blade 3 is provided.

  Moreover, this coating device is provided with a storage tank 4 for storing a water-based paint. A supply path 5 for supplying water-based paint to the upper part of each coating roll 2 is led out from the storage tank 4. The supply path 5 is opened near the upper end of each application roll 2, and the water-based paint flowing out from the supply path 5 is supplied to the surface of each application roll 2. In addition, an on-off valve 6 for allowing the water-based paint in the storage tank 4 to flow through the supply path 5 is provided.

  Further, the recovery tank 7 and the storage tank 4 are connected by a recovery path 8 for returning the water-based paint in the recovery tank 7 to the storage tank 4. Further, a pump 9 is provided as a drive source that provides a driving force for circulating the water-based paint in the collection tank 7 to the collection path 8.

  A method for applying a water-based paint to both surfaces of the substrate 1 using such an application apparatus will be described.

  Examples of the substrate 1 include an appropriate plate material and sheet material, and particularly a printed wiring board.

  An appropriate paint is used as the water-based paint. For example, when the substrate 1 is a printed wiring board, an aqueous solder resist ink can be used as the water-based paint. As the water-based solder resist ink, an ink containing a curable resin such as an appropriate photo-curable resin or thermosetting resin can be used.

  The water-based paint contains only water as a solvent, or the main component of the solvent needs to be water. When the solvent contains an organic solvent other than water, the content of the organic solvent in the solvent is preferably 10% by mass or less. Usable organic solvents include not only water-soluble solvents but also water-insoluble or insoluble organic solvents. Specific examples of usable organic solvents include ethanol, propanol, 2-propanol, butanol, 2-butanol, hexanol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, butylene glycol, trimethylolpropane, Linear, branched, secondary or polyhydric alcohols such as neopentyl glycol, glycerin, 1,2,4-butanetriol, 1,2-butanediol, 1,4-butanediol, diacetone alcohol; ethylene glycol Ethylene glycol alkyl ethers such as monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether; diethylene glycol monomethyl ether, diethylene group Polyethylene glycol alkyl ethers such as coal monoethyl ether and triethylene glycol monomethyl ether; propylene glycol alkyl ethers such as propylene glycol monomethyl ether, polypropylene glycol alkyl ethers such as dipropylene glycol monomethyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol Acetic esters such as monomethyl ether acetate, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate, glycerol monoacetate, glycerol diacetate; lactates such as ethyl lactate and butyl lactate; diethyl adipate, dibutyl adipate, etc. Adipic acid esters; phthalic acid Phthal esters such as ethyl and dibutyl phthalate; Dialkyl glycol ethers such as diethylene glycol diethyl ether; Ketones such as methyl ethyl ketone, cyclohexanone and isophorone; Aromatic hydrocarbons such as toluene and xylene; Swazol series (Maruzen Petrochemical Co., Ltd.) Manufactured), Solvesso series (manufactured by Exxon Chemical Co., Ltd.) and the like, and petroleum-based aromatic mixed solvents; n-hexane, cyclohexane, tetrahydrofuran and the like. These organic solvents are used alone or in combination of two or more.

  The content of the solvent in the water-based paint is adjusted as appropriate so that the viscosity of the water-based paint can be uniformly applied to the substrate 1 by roll coating. In particular, when the content of the solvent is adjusted so that the viscosity of the water-based paint is in the range of 100 to 10000 mPa · s, the uniform application property of the water-based paint to the substrate 1 becomes very excellent.

  When applying the water-based paint to the substrate 1, first, the on-off valve 6 is opened while rotating the application roll 2, and the water-based paint is supplied from the storage tank 4 to the application roll 2 through the supply path 5. The water-based paint is leveled by the doctor blade 3 while flowing downward along the surface of the coating roll 2 from the upper part of the coating roll 2 and supplied to the entire surface of the coating roll 2.

  In this state, the base material 1 is transported in the horizontal direction in a state where the base material 1 stands vertically with respect to the horizontal direction, and passes between the pair of coating rolls 2. As a result, the water-based paint on the surface of each coating roll 2 is transferred onto both surfaces of the substrate 1 and applied.

  Further, the water-based paint that has flowed down to the lower end of the application roll 2 without being applied to the substrate 1 falls from the lower end of the application roll 2 and is received by the collection tank 7. The water-based paint scraped off by the doctor blade 3 also flows downward along the doctor blade 3, falls from the lower end of the doctor blade 3, and is received by the collection tank 7. The water-based paint in the collection tank 7 is returned to the storage tank 4 by the pump 9 through the collection path 8 and used again for application to the substrate 1.

  When the water-based paint is applied to the base material 1 in this way, the water-based paint supplied to the application roll 2 is not applied to the base material 1 and does not remain on the application roll 2 for a long time. Fall from. For this reason, the occurrence of uneven coating due to the increase in viscosity of the aqueous paint due to the volatilization of the solvent from the aqueous paint on the application roll 2 is suppressed. Further, since the water-based paint dropped from the coating roll 2 or the doctor blade 3 is collected and reused, the resource utilization efficiency is increased.

  Further, when the water-based paint is collected in this way, it is preferable to perform a process for adjusting the viscosity of the water-based paint in the storage tank 4. After the water-based paint is supplied to the coating roll 2 and before it is recovered, the solvent is slightly evaporated from the water-based paint, and the solvent content of the recovered water-based paint is compared with that when the water-based paint is supplied to the coating roll 2. Therefore, when the water-based paint is continuously applied to the base material 1 for a long time, the content of the solvent in the water-based paint in the storage tank 4 gradually decreases and the viscosity increases. End up. If this is left as it is, coating unevenness may occur. On the other hand, when the viscosity of the water-based paint in the storage tank 4 is increased, if the process of adjusting the viscosity of the water-based paint is performed, an increase in the viscosity of the water-based paint supplied to the coating roll 2 is suppressed, and It becomes possible to uniformly apply the water-based paint to the substrate 1 over time.

  The viscosity of the water-based paint in the storage tank 4 is adjusted by an appropriate method. In the example shown in FIG. 1, the viscometer 10 that measures the viscosity of the water-based paint in the storage tank 4 in the coating apparatus, and the viscosity of the water-based paint measured by the viscometer 10 has reached a preset upper limit value. In this case, a solvent supply mechanism is provided for supplying the solvent into the storage tank 4 and stopping the supply of the solvent to the storage tank 4 when the viscosity reaches a preset lower limit value. The solvent supply mechanism includes a solvent storage tank 11 that stores the solvent, a solvent supply path 12 that connects the storage tank 4 and the solvent storage tank 11, an on-off valve 13, and a drive mechanism based on a measurement result by the viscometer 10. The control part 14 comprised with the microcomputer etc. which control is provided. In this case, when the viscosity of the water-based paint in the storage tank 4 reaches the upper limit value, the open / close valve 13 is opened by the control of the control unit 14 based on the measurement result by the viscometer 10 and the solvent supply path 12 is connected from the solvent storage tank 11. Through the storage tank 4. When the viscosity of the water-based paint in the storage tank 4 reaches the lower limit value, the control unit 14 closes the on-off valve 13 based on the measurement result by the viscometer 10 and supplies the solvent from the solvent storage tank 11 to the storage tank 4. To stop. For this reason, the viscosity of the water-based paint in the storage tank 4 is maintained in a predetermined range for a long time.

  Further, a replenishment mechanism for replenishing the water-based paint to the storage tank 4 is provided, and the replenishment mechanism replenishes the storage tank 4 with an aqueous solvent having a viscosity lower than that of the aqueous solvent supplied to the coating roll 2. Anyway. The replenishment mechanism includes, for example, a replenishment tank that stores a water-based paint for replenishment, a replenishment path that connects between the replenishment tank and the storage tank 4, an open / close valve that opens and closes the circulation of the replenishment path, and the like. The replenishment tank may be provided in the coating apparatus or may be provided outside the coating apparatus. In this case, when the amount of the water-based paint stored in the storage tank 4 decreases due to the application of the water-based paint to the base material 1, the on-off valve is opened to store the water-based paint in the supply tank via the supply path. It is supplied to the tank 4. Thereafter, the supply of the water-based paint is stopped by closing the on-off valve. When the low-viscosity water-based paint is supplied to the storage tank 4 in this manner, the low-viscosity water-based paint and the high-viscosity water-based paint in the storage tank 4 are mixed, so that The viscosity of the water-based paint is lowered, and the viscosity of the water-based paint is maintained within a predetermined range. The replenishment amount of the water-based paint, the replenishment cycle, the viscosity of the water-based paint to be replenished, and the like are appropriately adjusted based on empirical rules so that the viscosity of the water-based paint in the storage tank 4 is maintained within a predetermined range. Further, as an additional process, the operator periodically measures the actual viscosity of the water-based paint in the storage tank 4, and based on the measurement result, the operator enters the solvent or high-viscosity water system in the storage tank 4. You may make it adjust the viscosity of the water-system coating material in the storage tank 4 by supplying a coating material.

[Example 1]
Using the coating apparatus having the configuration shown in FIG.

  The pair of coating rolls 2 in this coating apparatus are inclined such that the upper end protrudes in the direction opposite to the conveyance direction of the substrate 1 and the lower end side protrudes in the conveyance direction of the substrate 1, and the inclination angle is relative to the horizontal plane. It was installed so that it might become 60 degrees.

  Moreover, as this application | coating roll 2, what was provided with the rubber lining and the groove process was used. The dimensions of the coating roll 2 are roll length: 670 mm, roll diameter: 80 mm, pitch between grooves: 0.4 mm, and groove depth: 0.2 mm.

  Moreover, the copper clad laminated board (thickness 0.6mm, planar view dimension 400mmx330mm) was used as the base material 1. FIG.

  Further, as a water-based paint, a photosensitive emulsion for screen plate making (trade name “Plus Print 39”) manufactured by Kyoyo Chemical Industry Co., Ltd. was used. The water-based paint was adjusted so that the viscosity at 25 ° C. was 1000 mPa · s by adding water in advance. The supply speed of the water-based paint to the application roll 2 was 1 L / min.

  Moreover, the conveyance speed of the base material 1 was 1 m / min, and the base material 1 was continuously conveyed so that two base materials 1 could be supplied between the coating rolls 2 per minute.

[Comparative Example 1]
A horizontal roll coater (“MRC-450C” manufactured by Pilot Seiko Co., Ltd.) provided with a pair of coating rolls having a horizontal rotation axis was used as a coating apparatus.

  As the coating roll, a rubber lining and a groove processed were used. The dimensions of this coating roll are roll length: 490 mm, roll diameter: 90 mm, pitch between grooves: 0.4 mm, and groove depth: 0.2 mm.

  A water-based paint was applied to the substrate 1 under the same conditions as in Example 1 except that such a coating apparatus was used.

[Evaluation]
In Example 1 and Comparative Example 1, the water-based paint was continuously applied to the substrate 1, and after 10 minutes, 30 minutes, 1 hour, 3 hours, 12 hours, and 24 hours from the start of application. The state of the coating film of the water-based paint applied to the substrate 1 was observed later. And, the case where the coating unevenness was not recognized in the coating film was evaluated as ◯, the case where the coating unevenness was observed in the coating film was evaluated as Δ, and the case where the portion where the coating film was not formed on the substrate 1 was evaluated as ×. The results are shown in Table 1.

  As shown in Table 1, in Comparative Example 1, a portion where a coating film was not formed on the base material 1 was generated after 1 hour from the start of coating, and the subsequent coating was stopped. As shown in Table 1, the viscosity of the water-based paint remaining on the doctor blade at the end of this coating test was 18000 mPa · s.

  On the other hand, in Example 1, coating unevenness did not occur even after 24 hours from the start of coating. Further, the viscosity of the water-based paint remaining in the collection tank 7 at the end of the test was 5000 mPa · s as shown in Table 1, and the increase in the viscosity of the water-based paint was suppressed.

It is the schematic which shows an example of embodiment of this invention.

Explanation of symbols

1 base material 2 coating roll

Claims (6)

The base material is transported in the horizontal direction in a state of being perpendicular to the horizontal direction, and the pair of coating rolls protrudes from the upper end side to the side opposite to the transport direction of the base material and the lower end side to the transport direction side of the base material In a state where the rotation axis of the application roll is arranged in parallel so as to be inclined with respect to the horizontal plane so that the rotation axis of the application roll is inclined along the conveying direction of the base material, A water-based paint application method, wherein a water-based paint is applied to the surface of a base material by supplying the water-based paint to the surface and passing the base material between the pair of coating rolls. After being supplied to the surface of the coating roll, water-based paint that has not been applied to the substrate is recovered under the coating roll, in claim 1, characterized in that the aqueous paint is again supplied to the surface of the coating roll Application method of water-based paint as described . The method of applying a water-based paint according to claim 2, wherein the viscosity of the water-based paint supplied to the surface of the coating roll is adjusted. The organic solvent content in the solvent in an aqueous coating material is 10 mass% or less, The coating method of the aqueous coating material as described in any one of Claims 1 thru | or 3 characterized by the above-mentioned. The water-based paint coating method according to any one of claims 1 to 4, wherein a water-based paint having a viscosity in the range of 100 to 10,000 mPa · s is supplied to the surface of the coating roll. 6. The method of applying a water-based paint according to claim 1, wherein the substrate is a printed wiring board, and the water-based paint is an aqueous resist ink for forming a resist film.

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