Vacuum drying apparatus and vacuum drying method

• US 20030019124A1
• Filed: 09/16/2002
• Published: 01/30/2003
• Est. Priority Date: 02/23/2000
• Status: Active Grant

• Current Assignee: Shunji Miyakawa, Soichi Matsuo, Yasuhide Nakajima
• Original Assignee: Shunji Miyakawa, Soichi Matsuo, Yasuhide Nakajima
• Inventors: Matsuo, Soichi, Nakajima, Yasuhide, Miyakawa, Shunji
• Granted Patent: US 7,343,695 B2
• Time in Patent Office: Days
• US Class Current: 34/92
• CPC Class Codes: F26B 5/04 by evaporation or sublimation of moisture under reduced pressure, e.g. in a vacuum F26B11/049 and F26B17/128 take precedence

Abstract

A vacuum drying apparatus and a vacuum drying method are provided wherein it is possible to reduce the drying time of an object to be dried and the surface condition of the object to be dried after drying is extremely satisfactory. A vacuum pump is connected to an exhaust port of a vacuum chamber through a suction pipe, and a frequency converter is provided on the input side of an alternating current motor for driving the vacuum pump to form a vacuum drying apparatus. A substrate coated with coating liquid is placed in the vacuum chamber of the vacuum drying apparatus. A gas in the vacuum chamber is exhausted at a high rate until the solvent evaporation rate of the solvent of the coating liquid comes to the vacuum degree that is slightly lower than the vacuum degree at which the evaporation rate of the solvent of the coating liquid is abruptly elevated, and thereafter, the gas in the vacuum chamber is exhausted at a low rate to cause the solvent of the coating liquid to evaporate gradually, and after evaporation of the solvent of the coating liquid, the pressure in the vacuum chamber are returned to the atmospheric pressure.

Claims

1. A vacuum drying apparatus comprising:

a vacuum chamber provided with an exhaust port;

a vacuum pump connected to the exhaust port of the vacuum chamber through a suction pipe;

an alternating current motor for driving the vacuum pump; and

a frequency converter provided on the input side of the alternating current motor.

2. The vacuum drying apparatus according to claim 1, further comprising a controller for detecting the vacuum degree in the vacuum chamber, and adjusting the frequency converter by the preset vacuum degree to change an alternating current frequency to be introduced into the alternating current motor.

3. A vacuum drying apparatus comprising:

a vacuum chamber provided with an exhaust port;

a vacuum pump connected to the exhaust port of the vacuum chamber through a suction pipe equipped with a shut-off valve; and

a motor for driving the vacuum pump.

4. The vacuum drying apparatus according to claim 3, further comprising a controller for detecting the vacuum degree in the vacuum chamber, and adjusting the shut-off valve by the preset vacuum degree to change an exhaust rate from the exhaust port.

5. A vacuum drying apparatus comprising:

a vacuum chamber provided with an exhaust port;

a vacuum pump connected to the exhaust port of the vacuum chamber through a suction pipe equipped with a shut-off valve;

an alternating current motor for driving the vacuum pump; and

a frequency converter provided on the input side of the alternating current motor.

6. The vacuum drying apparatus according to claim 5, further comprising a controller for detecting the vacuum degree in the vacuum chamber, adjusting the frequency converter by the preset vacuum degree to change the alternating current frequency to be introduced into the alternating current motor, and/or adjusting the shut-off valve by the preset vacuum degree to change the exhaust rate from the exhaust port.

7. A vacuum drying method for placing a substrate coated with coating liquid containing solvent in a vacuum chamber and evaporating the solvent in the coating liquid under reduced pressure, comprising:

an air eliminating step of reducing the pressure in the vacuum chamber to an exhaust rate changing pressure which is a pressure level slightly higher than the pressure at which the evaporation rate of the solvent in the coating liquid is rapidly elevated,

a solvent evaporating step of reducing the pressure from the above exhaust rate changing pressure to the terminal pressure which is a pressure at which the evaporation of the solvent is completed, and

an atmospheric pressure step of recovering the atmospheric pressure from the above terminal pressure,

wherein the exhaust rate in the air eliminating step is set to a rate faster than the exhaust rate in the solvent evaporating step.

8. The vacuum drying method according to claim 7, wherein the exhaust rate changing pressure is set to be higher than the vapor pressure of the solvent contained in the coating liquid.

9. The vacuum drying method according to claim 7, wherein the terminal pressure is set to be such a pressure that the pressure reduction rate abruptly rises when pressure reduction is effected at a constant exhaust rate in the solvent evaporating step.

10. The vacuum drying method according to claim 8, wherein the terminal pressure is set to be such a pressure that the pressure reduction rate abruptly rises when pressure reduction is effected at a constant exhaust rate in the solvent evaporating step.