JP2014097479A - Solvent for electrostatic atomization liquid preparation, electrostatic atomization liquid, and electrostatic atomization method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve uniformity of a particle size of a droplet and uniformity of spatial distribution of the droplet, in electrostatic atomization.SOLUTION: A solvent for electrostatic atomization liquid preparation has a dissolution parameter of 9.2-13.4. An electrostatic atomization liquid includes the solvent with the dissolution parameter of 9.2-13.4, and a solute. The electrostatic atomization liquid is supplied to a flow pipe 1 with an electrode via a line L10. The electrically-charged electrostatic atomization liquid is supplied onto a substrate SB by a voltage applied between the flow pipe 1 with the electrode and a counter electrode 20.

Description

  The present invention relates to a solvent for preparing an electrostatic spray, an electrostatic spray, and an electrostatic spray method.

  2. Description of the Related Art Conventionally, there is known an electrostatic spray technique in which a charged electrostatic spray liquid is discharged from a cylinder, a large number of minute droplets are formed by a repulsive force due to electrostatic force, and supplied to an object.

JP 2006-58628 A JP 2004-136655 A

  However, in the conventional technology, the uniformity of the droplet size and the uniformity of the spatial distribution of the droplets are not sufficient.

  The present invention has been made in view of the above problems, and can improve the uniformity of the particle size of the droplets and the uniformity of the spatial distribution of the droplets. And it aims at providing the electrostatic spraying method etc.

  The solvent for preparing an electrostatic spray according to the present invention has a solubility parameter of 9.2 to 13.4.

Here, it is preferable that the solvent for preparing an electrostatic spray solution includes at least one selected from the group consisting of ethyl lactate, 3-methoxy-1-butanol, γ-butyrolactone, and one compound of the formula.

  The electrostatic spray according to the present invention includes a solvent having a solubility parameter of 9.2 to 13.4 and a solute.

  Here, the solvent preferably includes at least one selected from the group consisting of ethyl lactate, 3-methoxy-1-butanol, γ-butyrolactone, and one compound of the formula.

  Moreover, it is preferable that the said solute contains at least 1 selected from the group which consists of resin, a metal particle, and an oxide particle.

  The electrostatic spraying method according to the present invention includes a step of charging the electrostatic spray solution and a step of discharging the charged electrostatic spray solution from the cylinder.

  According to the present invention, in electrostatic spraying, the uniformity of the particle size of the droplets and the uniformity of the spatial distribution of the droplets are improved.

FIG. 1 is a partially broken schematic view of an electrostatic spraying apparatus 100 according to an embodiment of the present invention.

An embodiment of the present invention will be described.
(Solvent for preparing electrostatic spray solution)
The solvent for preparing an electrostatic spray according to the present invention has a solubility parameter of 9.2 to 13.4.

The solubility parameter is a so-called Hildebrand solubility parameter δ and is defined by two equations. Here, ΔHv is the heat of vaporization, R is the gas constant, T is the temperature, and Vm is the molar volume. Moreover, the solubility parameter in this specification and a claim is a value in 25 degreeC, and a unit is (cal / cm < ³ >) ^<1/2 >.

Solvents having solubility parameters in such a range include ethyl lactate (δ = 9.5), 3-methoxy-1-butanol (δ = 10.92), γ-butyrolactone (δ = 12.8), and And compounds of formula 1 (Ecamide B100 (trademark), δ = 13.0) and the like.

Further, the solvent for preparing the electrostatic spray liquid may be a single solvent or a mixture of solvents. An example of a solvent mixture is a mixture of any of the above mentioned solvents.
Note that the solubility parameter δ of the mixed solvent of the solvent 1 and the solvent 2 can be calculated as (φ ₁ V ₁ δ ₁ + φ ₂ V ₂ δ ₂ ) / (V ₁ φ ₁ + V ₂ φ ₂ ).
Here, δ ₁ , δ ₂ : solubility parameters of solvents 1 and 2, φ ₁ and φ ₂ : volume fraction of solvents 1 and 2 (φ ₁ + φ ₂ = 1), V ₁ and V ₂ : solvents 1 and 2 Is the molar volume.

  The solvent for preparing the electrostatic spray solution is preferably a liquid at 25 ° C.

  The solvent for preparing an electrostatic spray solution can contain additives in addition to the solvent. Examples of additives are surfactants, leveling agents and the like. The concentration of the additive can usually be 10% by mass or less.

(Electrostatic spray)
The electrostatic spray according to this embodiment includes the above-described solvent for preparing an electrostatic spray and a solute.

  A solute is a component that remains as a non-volatile component after the solvent is dried, and examples of the solute are a resin, a polymerizable monomer, and inorganic particles including metal particles, oxide particles, and the like.

  Examples of the resin are a photosensitive resin and a non-photosensitive resin. Examples of the photosensitive resin are phenolic resins such as novolak resins, polyhydroxystyrene resins, epoxy resins, acrylic resins, and polyimide resins. The photosensitive resin can contain a photosensitizer such as naphthoquinonediazide in addition to the base resin.

  Examples of the non-photosensitive resin are epoxy resin, acrylic resin, urethane resin, silicone resin, polyester resin, and polyimide resin.

  Examples of the polymerizable monomer are acrylic monomers such as 1,9-nonanediol acrylate and 1,1,1-trimethylolpropane triacrylate. These can be used as a coating liquid for a surface protective film.

  Examples of metal particles are silver particles, gold particles, copper particles, and the like.

  Examples of the oxide particles include ceramic particles such as titania, silica, and alumina, and glass particles.

  The example of the particle size of a metal particle or an oxide particle is 0.001-100 micrometers.

  The concentration of the above-mentioned solvent for preparing an electrostatic spray solution in the electrostatic spray solution is not particularly limited, but is preferably 15% by mass or more, and more preferably 30% by mass or more. Moreover, it is preferable that the density | concentration of the solute in an electrostatic spray liquid shall be 500 mass parts or less with respect to 100 mass parts of solvents for electrostatic spray liquid preparation. Although there is no particular lower limit of the concentration, for example, it can be 0.1 parts by mass.

  A preferable viscosity range of the electrostatic spray liquid is 5 to 10000 mPa · s, but is not limited thereto.

  The electrostatic spray liquid may contain additives such as a surfactant and a leveling agent. The concentration of the additive is usually preferably 10% by mass or less.

  When the solute is a resin, an electrostatic spraying solvent that can dissolve the resin is preferably used. When the solute is a particle, an electrostatic spraying solvent that can disperse the particles is used. preferable.

  The method for preparing the electrostatic spray solution is not particularly limited, and the above-described solvent for preparing the electrostatic spray solution and the solute may be mixed.

(Electrostatic spraying method)
FIG. 1 is a partially broken schematic view of an electrostatic spraying apparatus 100 according to an embodiment of the present invention. The electrostatic spraying apparatus 100 according to the present embodiment includes an electrostatic spraying unit 10, a counter electrode 20, a power supply 30, a liquid supply unit 40, and an electrostatic spraying unit moving unit 50.

  The electrostatic spray unit 10 includes a flow tube 1 with an electrode and a cover 3.

  The electrode-equipped flow tube 1 is connected to an external power source 30, and the electrostatic spray liquid sent from the liquid supply unit 40 is charged by the electrode-equipped flow tube 1. The flow tube with electrode 1 is connected to the line L10 from the liquid supply unit 40 using the joint 4 at the upper end. For example, all or part of the flow tube with electrode 1 is made of a conductive material such as stainless steel, and all or part of the inner surface is formed of a conductive wall.

  The cover 3 is made of an electrically insulating material such as resin (PTFE or the like) so as to cover the flow tube 1 with electrode. Although the internal diameter of the flow tube 1 with an electrode is not specifically limited, For example, it can be set to 10-1000 micrometers.

  The counter electrode 20 is disposed on the opposite side to the electrostatic spray unit 10. The counter electrode 20 is disposed on an extension line of the axis of the flow tube with electrode 1 and is separated from the flow tube with electrode 1. The counter electrode 20 is preferably grounded. The distance between the electrode-equipped flow tube 1 and the substrate SB is not particularly limited, but can be, for example, about 10 to 60 mm.

  In this embodiment, the counter electrode has a plate shape, and the substrate SB to be coated is placed on the counter electrode.

  The power source 30 applies a voltage between the electrode-equipped flow tube 1 and the counter electrode 20. Usually, the voltage is a direct current, and for example, it is preferable to supply the voltage in a pulse form. Although a voltage is not specifically limited, In this embodiment, it can be set to 5-20 kV. The voltage is preferably applied to the counter electrode 20 so that the electrode-equipped flow tube 1 side is positive.

  The liquid supply unit 40 is a device that supplies the above-described electrostatic spray liquid to the electrode-equipped flow pipe 1 via the line L10.

  The liquid supply unit 40 includes a tank 41 that stores the electrostatic spray liquid, and a pump 42 that supplies the electrostatic spray liquid from the tank 41 to the flow pipe with electrode 1 via the line L10. In the present embodiment, by supplying air to the tank 41 in which the pump 42 is in a sealed state, the electrostatic spray liquid is supplied to the electrode-equipped flow pipe 1 through the line L10. In the present embodiment, the liquid supply unit 40 supplies the above-described electrostatic spray liquid to the electrode-equipped flow pipe 1.

  The electrostatic spray unit moving unit 50 moves the electrostatic spray unit 10 relative to the counter electrode 20. Specifically, for example, when the object is the substrate SB, the electrostatic spray unit 10 can move independently in two axes in a plane horizontal to the surface of the substrate SB. Thereby, the liquid can be applied to a desired portion on the substrate SB. Moreover, it is preferable that the electrostatic spray unit moving part 50 can move the electrostatic spray unit 10 with respect to the counter electrode 20 also in a direction perpendicular to the substrate SB. Thereby, it is also easy to adjust the distance between the tip of the electrode-equipped flow tube 1 inside the electrostatic spray unit 10 and the substrate SB.

Then, the coating method using the electrostatic spraying apparatus 100 of this embodiment is demonstrated.
First, the substrate SB to be applied is placed on the counter electrode 20. Subsequently, a voltage is applied between the flow tube with electrode 1 inside the electrostatic spray unit 10 and the counter electrode 20 by the power source 30. Moreover, the pump 42 is driven and the liquid in the tank 41 is supplied to the tip of the flow tube 1 with an electrode inside the electrostatic spray unit 10 through the line L10. The liquid is charged by being charged by the electrode-equipped flow tube 1 inside the electrostatic spray unit 10, and the liquid protruding from the tip of the electrode-equipped flow tube 1 inside the electrostatic spray unit 10 forms a Taylor cone. At the tip of the cone, the droplets are split by electrostatic force, and a number of minute droplets are ejected toward the counter electrode having the opposite charge.

  At this time, in this embodiment, since the above-described solvent and electrostatic spray liquid are used, the uniformity of the particle size of the droplets and the uniformity of the spatial distribution of the droplets are improved. The reason for this is not clear, but since a solvent having a solubility parameter in the above-described range is used, it is considered that the balance between polarizability and chargeability is suitable for electrostatic spraying.

  Then, by adjusting the distance between the tip of the electrode-equipped flow tube 1 inside the electrostatic spraying unit 10 and the substrate SB and supplying a large number of droplets in a state where the solvent is not dried onto the substrate SB, these liquids are supplied. The droplets can be combined on the substrate to densify the liquid film or to make the thickness uniform. Alternatively, the distance between the tip of the electrode-equipped flow tube 1 inside the electrostatic spray unit 10 and the substrate SB may be adjusted to supply and deposit a large number of particles in a solvent-dried state on the substrate SB.

The present invention is not limited to the above embodiment, and various modifications can be made.
For example, the method of electrostatic spraying is not limited to the above embodiment, and is not particularly limited as long as it includes a method of charging the electrostatic spray liquid and releasing the charged electrostatic spray liquid from the flow path of the cylinder. For example, the method of charging the electrostatic spray liquid and the method of discharging from the cylinder are not particularly limited.

  In the above embodiment, since the liquid application target is the substrate SB, the counter electrode 20 is also plate-shaped, but the shape of the counter electrode 20 can be changed to a desired form according to the shape of the application target. . Further, the object to be applied is not particularly limited, and for example, the liquid can be applied to various objects such as a substrate having an uneven surface.

(Examples 1-4, Comparative Examples 1 and 2)
The electrostatic spraying apparatus of FIG. 1 was used, and the type of solvent and the presence or absence of solute were changed as shown in Table 1, and electrostatic spraying was electrostatically sprayed on the substrate. Resist resin (Nagase ChemteX NPR3540-S1) was used as a solute. The concentration of the resist resin was 30 parts by mass with respect to 100 parts by mass of the solvent.
The conditions of the apparatus are shown below.
Flow tube with electrode: stainless steel, applied voltage 12kV
Substrate (Si substrate), distance between substrate and tip of flow tube with electrode 24 mm, nitrogen gas pressure for supplying liquid 0.005 MPa, substrate moving speed 25 mm / s

Further, the spray behavior was observed visually. The results are shown in Table 1. Here, “good” indicates that the spray liquid is uniform and minute, and “bad” indicates that the spray liquid is not uniform or minute.

  DESCRIPTION OF SYMBOLS 1 ... Flow pipe | tube with an electrode, 20 ... Counter electrode, 30 ... Power supply, 40 ... Liquid supply part, 100 ... Electrostatic spraying apparatus.

Claims (6)

  A solvent for preparing an electrostatic spray having a solubility parameter of 9.2 to 13.4. The solvent for preparing an electrostatic spray according to claim 1, comprising at least one selected from the group consisting of ethyl lactate, 3-methoxy-1-butanol, γ-butyrolactone, and one compound of the formula.

  An electrostatic spray solution comprising a solvent having a solubility parameter of 9.2 to 13.4 and a solute. The electrostatic spray according to claim 3, wherein the solvent includes at least one selected from the group consisting of ethyl lactate, 3-methoxy-1-butanol, γ-butyrolactone, and one compound of the formula.

  The electrostatic spray solution according to claim 3 or 4, wherein the solute includes at least one selected from the group consisting of a resin, metal particles, and oxide particles.   An electrostatic spraying method comprising: a step of charging the electrostatic spray solution according to any one of claims 3 to 5; and a step of discharging the charged electrostatic spray solution from the cylinder.

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