Atmospheric pressure plasma processing method and atmospheric pressure plasma processing device

Abstract

Provided are an atmospheric pressure plasma processing method and an atmospheric pressure plasma processing device with which a sample is processed in a short time, and the number of processing steps is reduced. In the method and device, the surface of a sample is subjected to plasma processing under atmospheric pressure by means of: a plasma generating device that generates plasma by supplying a pressurized inert gas in a rotating flow from a gas inlet portion 38 to an inner peripheral surface of a reaction cylindrical body 31, and supplying microwaves controlled to a predetermined electric power amount into a high-frequency resonance cavity 34; a substantially cross-shaped reaction container 5; a sample moving mechanism 7 that enables a sample SF to move relative to the plasma flow within the reaction container 5; and a control means 9 that controls a plasma generation state in accordance with the state of the sample.

Description

Atmospheric pressure plasma processing method and atmospheric pressure plasma processing apparatus

[0001] The present invention relates to an atmospheric pressure plasma processing method and an atmospheric pressure plasma processing apparatus capable of processing the surface of a sample by irradiating the sample with a plasma flow under atmospheric pressure.

[0002] Polytetrafluoroethylene (PTFE) is well known as an ultimate material in many respects. Not only is it heat-resistant, but it also boasts the lowest high-frequency loss factor, making it a popular choice for circuit boards. However, PTFE lacks sufficient hardness and strength, necessitating reinforcement with epoxy resins or other materials for use as a substrate. However, PTFE's difficulty in adhering to other surfaces has hindered its use in circuit boards. Therefore, a technique for improving the adhesive properties of PTFE by irradiating it with low-temperature atmospheric-pressure plasma using helium (He) has been proposed (Non-Patent Document 1). While this conventional technique (Non-Patent Document 1) achieved some improvement in adhesive strength, it still had the drawback of poor mechanical strength. To address this drawback, a boron-hydrogen treatment method has been proposed. This boron-hydrogen treatment method, when using an epoxy resin agent, achieved higher adhesive strength than the He treatment method (Non-Patent Document 1), but had the drawback of achieving insufficient strength for industrial applications. In an attempt to overcome this drawback of insufficient mechanical strength, a thermally assisted plasma method (Non-Patent Document 2) was proposed, in which a sample is heated (to approximately 200°C) and irradiated with low-temperature atmospheric-pressure He plasma. This thermally assisted plasma method (Non-Patent Document 2) not only provides a relatively large increase in the mechanical strength of the sample, but also increases the adhesive strength of the sample. Furthermore, Non-Patent Document 3 revealed more detailed plasma conditions, treatment time, sample heating temperature, and the chemical causes of the improved adhesive strength due to heating, which were not revealed in Non-Patent Document 2. This device plasma-treats a sample in a directly heated state, thereby removing a layer called WBL that remains on the sample surface due to the temperature increase, thereby promoting the formation of a cross-linked structure on the sample surface.

[0003] "Journal of Photopolymer Science and Technology" 2011 Vol. 24, No. 4, pp. 441-445 "Surface Technology" 2016, Vol. 67, No. 10, No. 551-556 "Journal of Photopolymer Science and Technology” 2022 Vol. 35, No. 4, pp. 299-302

[0004] However, while conventional thermally assisted plasma processes using low-temperature He atmospheric plasma can roughen the PTFE surface and increase adhesive strength, the resulting surface roughness also leads to the following drawbacks. Specifically, when PTFE processed by conventional thermally assisted plasma processes is used on electronic substrates, the signal delay time deteriorates as the substrate surface roughness increases. Since the roughness of the PTFE surface is related to the plasma treatment time, prolonged plasma treatment is undesirable. Meanwhile, this thermally assisted plasma process requires a minimum treatment time of approximately 5 minutes regardless of the PTFE (sample) temperature. Because practical mechanical strength cannot be achieved below this time, the treatment time cannot be shortened. Thus, conventional plasma treatment technologies have the drawback of being unable to satisfy the contradictory requirements of shortening the treatment time to reduce sample surface roughness and lengthening the treatment time to increase the sample's mechanical strength. Furthermore, the conventional thermally assisted plasma process also suffers from the disadvantage of being unable to satisfy one of the industrial requirements of sample treatment in as short a time as possible. Furthermore, according to the above-mentioned conventional technology, it is necessary to preheat the sample to several hundred degrees, which is an industrial requirement, and there is the disadvantage that the number of steps cannot be reduced as much as possible. The present invention aims to provide an atmospheric pressure plasma processing method and atmospheric pressure plasma processing apparatus that eliminate the above-mentioned disadvantages of the conventional technology, and that can process samples in a short time and reduce the number of processing steps by eliminating unnecessary processing steps.

[0005] In order to solve the above problems, the atmospheric pressure plasma processing method and atmospheric pressure plasma processing apparatus according to the present invention employ the following means: The atmospheric pressure plasma processing method according to claim 1 comprises the steps of: supplying a pressurized inert gas from a gas inlet port while rotating it into a reaction cylindrical body having a gas inlet port and a gas outlet port, and supplying a high frequency wave to the reaction cylindrical body to generate plasma inside the reaction cylindrical body and cause a plasma flow to be blown out from the gas outlet port of the reaction cylindrical body; exposing the sample to the plasma flow while moving the sample relatively in the direction of the plasma flow; and controlling the high frequency power to adjust the plasma generation state so that the plasma flow reaches the sample and the sample surface temperature is maintained at a predetermined temperature, thereby performing surface treatment of the sample. The atmospheric pressure plasma processing apparatus according to claim 2 is an atmospheric pressure plasma processing apparatus that supplies a pressurized inert gas and a high frequency electric field into a reaction cylindrical body to generate plasma inside the reaction cylindrical body and performs surface treatment on a sample with the plasma flow that is blown out from the reaction cylindrical body, comprising: a gas inlet and a gas outlet in the reaction cylindrical body; a high frequency resonant cavity that is provided so as to surround the outer periphery of the reaction cylindrical body; a plasma generator that supplies a pressurized inert gas from the gas inlet into the reaction cylindrical body while rotating it; and supplies a high frequency to the high frequency resonant cavity to generate plasma inside the reaction cylindrical body and blows out the plasma flow from the gas outlet of the reaction cylindrical body; a reaction vessel that is provided with a gas inlet and a gas outlet in a linear cylindrical shape and a cylindrical sample insertion port that is provided at right angles to the gas inlet and gas outlet, forming a substantially cross shape, and the gas inlet is connected to the gas outlet of the reaction cylindrical body; a sample moving mechanism that can be positioned in the direction of the sample insertion port of the reaction vessel, on which the sample can be detachably installed, and that can move the sample within the reaction vessel relative to the direction of the plasma flow blown out from the gas outlet; and control means that detects at least the temperature state of the sample within the reaction vessel and, based on this, can adjust the high-frequency power so that the state of the plasma flow and the sample surface temperature are maintained in predetermined states, and is characterized in that the sample is exposed to the plasma flow and reacts with the plasma flow to perform surface treatment of the sample.The atmospheric pressure plasma processing apparatus according to claim 3 is the apparatus according to claim 2, characterized in that the pressurized inert gas is argon gas or a gas obtained by mixing predetermined amounts of argon gas and helium gas. An atmospheric pressure plasma processing apparatus according to claim 4 is an atmospheric pressure plasma processing apparatus that supplies argon gas or a gas comprising a mixture of argon gas and helium gas in a predetermined amount and microwaves into a reaction cylinder to generate plasma inside the reaction cylinder, and performs surface treatment on a sample with the plasma flow blown out from the reaction cylinder, comprising: a plasma generating apparatus that provides a gas inlet and a gas outlet in the reaction cylinder, provides a cooling cylinder so as to surround the outer periphery of the reaction cylinder, provides a high frequency resonant cavity so as to surround the outer periphery of the cooling cylinder, supplies pressurized argon gas as a rotating flow from the gas inlet into the reaction cylinder, and cools the forwardly movable reaction cylinder by flowing a cooling medium through the cooling cylinder, supplies microwaves with a predetermined amount of power to the high frequency resonant cavity to bring the high frequency resonant cavity into a resonant state, generates plasma inside the reaction cylinder, and blows out the plasma flow from the gas outlet of the reaction cylinder; The present invention is characterized by comprising: a reaction vessel having a linear gas inlet and gas outlet, a cylindrical sample insertion port at right angles to the gas inlet and outlet, and a generally cross-shaped reactor vessel having the gas inlet connected to the gas outlet of the reaction tube; a sample moving mechanism for moving the sample within the reaction vessel relative to the direction of the plasma flow emitted from the gas outlet; and control means for detecting at least the sample temperature within the reaction vessel and adjusting the high-frequency power based on the detected sample temperature to maintain the plasma flow and the sample surface temperature at predetermined levels. The atmospheric pressure plasma processing apparatus according to claim 5 is the same as claim 4, except that the control means adjusts the high-frequency power so that the plasma flow directly reaches the sample surface. The atmospheric pressure plasma processing apparatus according to claim 6 is the same as claim 4, except that the control means adjusts the high-frequency power so that the sample surface temperature reached by the plasma flow is maintained at around 200°C.The atmospheric pressure plasma processing apparatus according to claim 7 is the same as claim 4, wherein the control means can set the microwave power value supplied to the high frequency resonant cavity to the maximum value that allows the plasma flow to reach the sample surface directly and maintain the sample surface temperature at around 200°C.

[0006] According to the present invention, the plasma flow can be reliably delivered to the sample, the sample surface temperature can be maintained at a predetermined temperature, and the sample and plasma flow can be moved relative to each other, which has the following advantages: (1) It is possible to satisfy the contradictory requirements of shortening the processing time to reduce the roughness of the sample surface and lengthening the processing time to increase the strength of the sample. (2) It is possible to satisfy one of the industrial requirements for processing samples in the shortest possible time. (3) It is possible to satisfy another industrial requirement for reducing the number of steps as much as possible.

[0007] Fig. 1 is a block diagram showing an atmospheric pressure plasma processing apparatus according to an embodiment of the present invention. Fig. 2 is an explanatory diagram showing the main parts of the atmospheric pressure plasma processing apparatus according to an embodiment of the present invention. Fig. 3 is a characteristic diagram showing the peel strength versus processing time of a sample processed by the atmospheric pressure plasma processing apparatus according to an example of the present invention.

[0008] An atmospheric pressure plasma processing method and an atmospheric pressure plasma processing apparatus according to an embodiment of the present invention will now be described. FIG. 1 is an overall block diagram showing an atmospheric pressure plasma processing apparatus according to an embodiment of the present invention. FIG. 2 is an explanatory diagram showing the main components of the atmospheric pressure plasma processing apparatus. In FIGS. 1 and 2, the atmospheric pressure plasma processing apparatus 1 according to an embodiment of the present invention can be broadly divided into a plasma generator 3 that generates plasma and blows it out, a reaction vessel 5 that serves as a reaction field in which a plasma flow Pf from the plasma generator 3 is exposed to a PTFE sample SF for reaction, a sample moving mechanism 7 that detachably positions the sample SF and moves the sample SF within the reaction vessel 5 relative to the plasma flow Pf, and a control system 9 that detects the state of the plasma generated in the plasma generator 3 and the surface temperature of the sample SF and controls the plasma generation state of the plasma generator 3. 1 and 2, the plasma generator 3 includes a reaction tube 31 made of quartz and having a long cylindrical shape, a cooling tube 32 also made of quartz and integrally provided coaxially with the central axis of the reaction tube 31 so as to surround the outer periphery of the reaction tube 31, an electromagnetic shield 33 provided coaxially with the central axis of the reaction tube 31 so as to surround the outer periphery of the cooling tube 32, and a high-frequency resonant cavity 34 provided coaxially with the central axis of the reaction tube 31 so as to surround the outer periphery of the cooling tube 32. Microwaves μW are supplied to the high-frequency resonant cavity 34 via a circulator 36a, a power meter 36b, a waveguide 36c, and a three-stub tuner 36d. As shown in FIGS. 1 and 2, the reaction tube 31 is made of quartz and has a long cylindrical shape. This reaction cylindrical body 31 is provided with a gas inlet 37 at the center of the upper side in the figure, and gas inlets 38, 38 at the outer peripheral surface of the cylinder on the upper side in the figure. In addition, a gas outlet 39 is provided at the lower part in the figure of this reaction cylindrical body 31. The gas inlet 37 is provided with carbon dioxide gas (CO ２ nitrogen gas (N ２The reactor 31 is configured so that a predetermined amount of inert gas (Ar gas) can be mixed and supplied via MFC 40n and MFC 40a. Ar gas is supplied to the gas inlets 38 via a mass flow controller (MFC) 41. The gas inlets 38 are oriented obliquely downward in the figure and offset tangentially from the outer periphery of the reactor 31. The Ar gas introduced through the gas inlets 38 rotates downward along the inner periphery of the reactor 31, imparting a rotational force to the inert gas introduced through the gas inlet 37. The plasma generated in the reactor 31 is discharged from the gas outlet 39 as a plasma flow Pf. The cooling cylinder 32 is made of quartz as shown in FIGS. 1 and 2 and is arranged coaxially around the central axis of the reactor 31 to surround the outer periphery of the reactor 31. The cooling cylinder 32 is provided with a cooling medium inlet 32n at the bottom of the figure and a cooling medium outlet 32t at the top of the figure. The cooling medium R enters the cooling cylinder 32 from the cooling medium inlet 32n, moves upward while cooling the reaction cylinder 31, and is discharged from the cooling medium outlet 32t. The reaction vessel 5 is made of quartz and, as shown in FIGS. 1 and 2, is configured in a generally cross shape with a vertical cylinder and a horizontal cylinder. The vertical cylinder is provided with a gas inlet 51 at the top of FIGS. 1 and 2 and a gas outlet 52 at the bottom of FIGS. 1 and 2. The horizontal cylinder is provided with insertion openings 53, 53 for the sample SF on the left side of FIGS. 1 and 2 and on the right side of FIGS. 1 and 2. 1 and 2, the diameter of the gas inlet 51 becomes smaller toward the top, and finally becomes the same as the inner diameter of the gas discharge part 39 of the reaction cylindrical body 31, and the gas inlet 51 is connected to the gas discharge part 39 in a bonded state. The reaction vessel 5 serves as a reaction field where the plasma flow Pf from the plasma generator 3 is directly exposed to the sample SF and reacts with it. The sample moving mechanism 7 is composed of a hollow drum tube 70 made of aluminum (Al), and the diameter of the hollow drum tube 70 is set to be slightly smaller than the inner diameter of the insertion ports 53, 53 of the reaction vessel 5.A sample SF is wound around the hollow drum tube 70 at a predetermined position near the center in the longitudinal direction, and the hollow drum tube 70 is passed through the insertion ports 53, 53. The sample SF is positioned as shown in FIG. 1 so that the plasma flow Pf can be sprayed onto it. A cooling medium r can be supplied from one side of the hollow drum tube 70 and discharged from the other side, allowing the hollow drum tube 70 to be cooled. When the hollow drum tube 70 is positioned as described above, one end of the hollow drum tube 70 is rotatably fixed to a fixing portion 71, and the other end of the hollow drum tube 70 is fixed to a rotation shaft 72 of a motor M. This allows the hollow drum tube 70 to rotate at a predetermined speed by the motor M, moving the sample SF relative to the plasma flow Pf. The control system 9 includes at least a sensor unit 91 provided at a predetermined position in the reaction tube 31 of the plasma generator 3, an optical fiber 92 for guiding detection light from the sensor unit 91, an optical sensor unit 93 disposed at a predetermined position in the reaction vessel 5 for measuring the surface temperature of the sample SF, an optical fiber 94 for guiding detection light from the optical sensor unit 93, and a control device 95 including a spectrometer that can capture the detection light from the optical fibers 92 and 94 and generate control commands CS using a predetermined algorithm based on the detection light and the output from the power meter 36c. The control commands CS from the control device 95 including the spectrometer are used to adjust the output power of the magnetron generator 35. The magnetron generator 35 adjusts the power value of the generated microwave μW based on the control commands CS. The microwave μW, the power value of which has been controlled in this manner, is supplied to the high-frequency resonant cavity 34 via the circulator 36a, the power meter 36b, the waveguide 36c, and the three-stub tuner 36d. As a result, the plasma generated in the reaction tube 31 is controlled based on the control command CS. According to the atmospheric pressure plasma processing apparatus 1 configured as above, the plasma processing of the PTFE sample SF is carried out as follows. ２ The gas was supplied via a mass flow controller (MFC) 40c to N ２The gas is mixed in a predetermined amount through the MFC 40n, and the Ar gas is mixed in a predetermined amount through the MFC 40a, and the mixture is supplied from the gas inlet 37 into the reaction tube 31. The supply of these gases may be performed as needed and is not essential. The other Ar gas is supplied from the gas inlets 38, 38 into the reaction tube 31 through a mass flow controller (MFC) 41. The gas inlets 38, 38 are arranged diagonally downward from above in the figure and offset in the tangential direction of the outer periphery of the reaction tube 31, so that the Ar gas introduced from the gas inlets 38, 38 moves downward in the figure while rotating along the inner circumferential surface of the reaction tube 31. The Ar gas moving downward on the inner circumferential surface of the reaction vessel 5 while rotating as described above may be supplied from the gas inlet 37, for example, with an inert gas (CO ２ Gas, N ２ When inert gases (CO 2 , Ar gas) are supplied into the reaction vessel 5, ２ Gas, N ２The plasma flows downward, transmitting a rotational force to the gas (e.g., Ar gas). In this state, microwaves μW are supplied to the high-frequency resonant cavity 34 from the magnetron generator 35 via the waveguide 36. This generates high-temperature plasma with a gas temperature of approximately 3,000 to 4,000°C within the reaction tube 31. This plasma becomes a plasma flow Pf from the gas outlet 39 of the reaction tube 31 and is blown into the reaction vessel 5 through the gas inlet 51. As the high-temperature plasma generated within the reaction tube 31 flows downward along the gas flow, it is gradually cooled by the cooling medium R flowing within the cooling tube 32 attached to the outer periphery of the reaction tube 31, and finally flows out as a plasma flow Pf from the gas outlet 39. This completes the process of blowing out a plasma flow from the gas outlet 39 of the reaction tube 31. A sample SF is wrapped around a predetermined position on the hollow drum 70, as shown in FIG. 1. The hollow drum tube 70 is inserted through the insertion openings 53, 53 of the reaction vessel 5, and the sample SF is set at the center of the reaction vessel 5, as shown in FIGS. 1 and 2 . In this state, the hollow drum tube 70 of the sample moving mechanism 7 is rotated at a predetermined speed, thereby moving the sample SF relative to the plasma flow Pf. This achieves the process of exposing the sample SF to the plasma flow Pf while moving the sample SF in a direction perpendicular to the direction of the plasma flow Pf. In this embodiment, the surface of the sample SF is moved at a relatively high speed to avoid an excessive increase in surface temperature due to direct contact of the plasma flow Pf with the surface of the sample SF, and to avoid time and spatial nonuniformity in the exposure of the plasma flow Pf that reaches the surface of the sample SF. In the above embodiment, the sample SF and the plasma flow Pf are moved relative to each other by rotating the hollow drum tube 70, but the point is that the sample SF and the plasma flow Pf only need to move relative to each other. For example, the sample SF may be moved at a predetermined speed in the direction of the insertion openings 53, 53, i.e., in the horizontal direction shown in the figure, or the sample SF and the plasma flow Pf may be moved relative to each other by other moving methods. Furthermore, the plasma generation state of the plasma generator 3 is controlled by a control system 9. Specifically, this is done as follows.The detection light from the sensor unit 91 that detects the inside of the reaction tube 31 is supplied via an optical fiber 92, and the detection light from the optical sensor unit 93 that detects the surface temperature of the sample SF is supplied via an optical fiber 94 to a control device 95 including a spectroscope. The control device 95 can generate a control command CS using a predetermined algorithm based on each detection light and the output value from the power meter 36b. The magnetron generator 35 controls the amount of power of the microwave μW generated based on the control command CS from the control device 95. The magnetron generator 35 controls the amount of power of the microwave μW generated by the control command CS, and the microwave μW is supplied to the high-frequency resonant cavity 34, thereby ensuring the following conditions: (a) The plasma flow Pf from the reaction tube 31 directly reaches the surface of the sample SF. (b) The surface temperature of the sample SF, which is directly reached by the plasma flow Pf, can be maintained at a predetermined temperature. (c) The discharge power value (power applied to the high-frequency resonant cavity 34) required for high-speed plasma processing can be supplied at the maximum value such that the above (a) and (b) are simultaneously satisfied. The atmospheric pressure plasma processing apparatus according to the embodiment of the present invention, which operates in this manner, has the following advantages: (1) It can satisfy the contradictory requirements of shortening the processing time to suppress the roughness of the sample surface and lengthening the processing time to increase the adhesive strength of the sample. (2) It can satisfy one of the industrial performance requirements, namely, the requirement to process samples in the shortest possible time. (3) It can also satisfy another industrial performance requirement, namely, the requirement to reduce the number of processes as much as possible.

[0009] Next, an embodiment of an atmospheric pressure plasma processing apparatus according to the present invention will be described primarily with reference to FIG. 2 . While specific dimensions are used in FIG. 2 , the present invention is not limited to these dimensions; other dimensions may be used as long as the same operational effects are obtained. In the plasma generator 3, a high-frequency resonant cavity 34 provided on the outer periphery of the reactor cylindrical body 31 receives microwaves μW of 2.45 GHz from a magnetron generator 35. A reactor vessel 5 is positioned at the lower end of the high-frequency resonant cavity 34, a length La = 9.5 cm below the lower end. The reactor vessel 5 has the following dimensions: The inner diameter D of the horizontal cylinder including the one insertion opening 53 and the other insertion opening 53 is D = 24 mmφ, and the length Lb of the horizontal cylinder is Lb = 50 mm. As already explained, the horizontal cylinder including the insertion ports 53, 53 and the vertical cylinder including the gas inlet port 51 and the gas outlet port 52 form the reaction vessel 5 in a substantially cross shape. In the sample moving mechanism 7, the aluminum (Al) hollow drum tube 70 has a total length Lc of 160 mm and an outer diameter d of 20 mmφ. A sample SF is wound around the center of the hollow drum tube 70. The thickness of the sample SF is 0.5 mm, but the thickness of the sample SF is not limited to this. One end of the hollow drum tube 70 is inserted through the insertion port 53 on the left side (one side) of the horizontal cylinder of the reaction vessel 5 in FIG. 2 . Then, one end of the hollow drum tube 70 is brought out through the insertion port 53 on the right side (the other side) in Figure 2, and the sample SF wound around the center of the hollow drum tube 70 is finally set in the center of the reaction vessel 5 as shown in Figures 1 and 2. When set in this manner, one end of the hollow drum tube 70 is rotatably fixed to a fixing part 71 as shown in Figure 1, and the other end of the hollow drum tube 70 is fixed to a rotating shaft 72 of a motor M, so that the hollow drum tube 70 is rotated by the motor M, and the sample SF wound around the center of the hollow drum tube 70 can be moved.After the sample SF is placed in the above-described state, plasma is generated in the reaction tube 31 of the plasma generator 3, and the high-temperature plasma flow PF is irradiated onto the sample SF in the reaction vessel 5, exposing the sample SF to the plasma flow PF. At this time, the plasma generator 3 is controlled based on the control command CS from the control system 9 so that the plasma flow Pf (microwave afterglow) reaches the surface of the sample SF directly, and so that the surface temperature of the sample SF reached by the plasma flow Pf is kept at around 200°C. These controls are performed based on the control command CS from the control system 9 to adjust the power applied to the high-frequency resonant cavity 34 so that the plasma flow Pf reaches the surface of the sample SF directly and so that the surface temperature of the sample SF reached by the plasma flow Pf is kept at around 200°C, i.e., so that two requirements are simultaneously satisfied. The plasma flow PF freely flows out into the atmosphere through the gap between the insertion ports 53, 53 of the reaction vessel 5 and the hollow drum tube 70, or through the gas outlet 52. Therefore, the processing area (processing space) of the sample SF is a semi-free space blowout type. Furthermore, to avoid excessive surface temperature rise due to direct contact of the plasma flow Pf with the surface of the sample SF, and to limit the time the plasma flow Pf reaches the surface of the sample SF and to avoid spatial nonuniformity of the plasma flow Pf, the surface of the sample SF must be moved at a relatively high speed. For this reason, in this example, the hollow drum tube 70 was rotated at a speed of 6 rpm. This enabled the desired performance to be achieved. The reason for exposing the sample SF to the plasma while rotating it on the hollow drum tube 70 is to suppress local temporal fluctuations in the exposure intensity on the surface of the sample SF due to temporal fluctuations in the emission distribution specific to atmospheric pressure Ar plasma. The hollow drum 70 can be cooled by forced circulation of water, air, or other cooling medium, but natural air cooling can also be achieved by opening the hollow interior of the hollow drum 70 to the atmosphere. Figure 3 is a characteristic diagram obtained by an embodiment of the atmospheric pressure plasma processing apparatus according to the present invention, showing the relationship between peel strength and processing time under the conditions that produced the maximum peel strength. Sample SF obtained by plasma processing according to the above embodiment will now be examined.The plasma-treated sample SF was tested as follows. For the adhesive strength test, the surface of the plasma-treated sample SF was bonded to a stainless steel plate using an epoxy adhesive, left at room temperature for 24 hours, and then measured using a 180-degree peel test with a tensile strength tester (Minebea 88FD Model LTS). Chemical observations of the surface of the sample SF were primarily performed using an ULVAC PHI5000 Versa Probe and XPS for comprehensive surface chemistry analysis. In Figure 3 , the test results are shown with a solid line representing the maximum value (Max) and a dotted line representing the average value (Mean). As shown in Figure 3 , the peel strength was low for short treatment times, but increased with increasing treatment time, reaching a maximum peel strength of 2 kN / m after 42 seconds of treatment. −１ ], which exceeded the highest value (1.2 [kN / m −１]), we were able to obtain values ​​far exceeding the maximum peel strength (42 seconds). Furthermore, as the treatment time was increased beyond the time at which the maximum peel strength was obtained (42 seconds), the peel strength gradually decreased. This result demonstrates that optimizing the treatment time is an important factor in obtaining the maximum peel strength. From the above, in the embodiment of the atmospheric pressure plasma treatment apparatus according to the present invention, the following conditions are suitable for surface treatment of a PTFE sample using a plasma flow (microwave afterglow) using Ar gas to obtain optimal strength without deteriorating the high-frequency characteristics: (Condition 1) The plasma flow Pf (microwave afterglow) must directly reach the surface of the sample SF. (Condition 2) The surface temperature of the sample SF reached by the plasma flow Pf must be controlled to approximately 200°C. (Condition 3) The discharge power value (power applied to the high-frequency resonant cavity 34) required for high-speed plasma treatment must be set to a maximum value that satisfies both (Condition 1) and (Condition 2). (Condition 4) To avoid excessive rise in surface temperature due to direct contact of the plasma flow Pf with the surface of the sample SF, and to avoid time and spatial non-uniformity of exposure to the plasma flow Pf that reaches the surface of the sample SF, the surface of the sample SF must be moved at a relatively high speed. Generally, when the peel strength is low, adhesive components and oxygen taken in from the air are detected on both peel interfaces. However, in the PTFE sample SF that was plasma-treated in the above example, taking these conditions into consideration, no oxygen atoms taken in from the air were found on either the PTFE side or the adhesive side on the adhesive peel surface that showed the highest peel strength, and fluorocarbon (CF ２ ) bonds were observed, it is presumed that cohesion failure occurred deeper inside the PTFE. ２ Gas, N ２In the previous example, a configuration was shown in which a small amount of Ar gas (one or more of the gases) could be added to the reaction tube 31, but it was found that this was likely to have an adverse effect on the adhesive strength, so it is preferable to use only Ar gas flow from the gas inlet 38. Furthermore, measurements using a surface roughness meter performed before and after treatment under the maximum peel strength conditions showed no significant change in roughness, and no change in the degree of surface melting was observed. According to an example of the atmospheric pressure plasma treatment apparatus of the present invention, a PTFE sample treated with this apparatus had a pressure of 2 [kN / m −１ ] and the processing speed was in the order of seconds, which has the following advantages: (1) The processing time can be shortened by suppressing the roughness of the sample surface, and the strength of the sample can be increased in a short processing time. (2) One of the performance requirements in industry, that of processing the sample in the shortest possible time, can be satisfied. (3) Furthermore, because the sample can be heated and processed simultaneously, another performance requirement in industry, that of minimizing the number of steps as much as possible, can be satisfied.

[0010] REFERENCE SIGNS LIST 1 atmospheric pressure plasma processing apparatus 3 plasma generator 5 reaction vessel 7 sample transfer mechanism 9 control system 31 reaction cylinder 32 cooling cylinder 33 electromagnetic shield 34 high frequency resonance cavity 37 gas inlet 38 gas inlet 39 gas outlet 51 gas inlet 52 gas outlet 53, 53 insertion port 70 hollow drum tube 91, 93 sensor section 92, 94 optical fiber 95 control device

Claims

1. An atmospheric pressure plasma processing method comprising the steps of: supplying a pressurized inert gas from a gas inlet into a reaction cylindrical body equipped with a gas inlet and a gas outlet while rotating the gas, and supplying high frequency power to the reaction cylindrical body to generate plasma within the reaction cylindrical body and cause a plasma flow to be blown out from the gas outlet of the reaction cylindrical body; exposing the sample to the plasma flow while moving the sample relative to the direction in which the plasma flow is blown out; and controlling the high frequency power to adjust the plasma generation state so that the plasma flow reaches the sample and the sample surface temperature is maintained at a predetermined temperature, thereby performing surface treatment of the sample.

2. An atmospheric pressure plasma processing apparatus that supplies a pressurized inert gas and a high frequency electric field into a reaction cylinder to generate plasma inside the reaction cylinder and performs surface treatment on a sample with the plasma flow that is blown out from the reaction cylinder, comprising: a plasma generator that provides a gas inlet and a gas outlet in the reaction cylinder, provides a high frequency resonant cavity that surrounds the outer periphery of the reaction cylinder, supplies a rotating pressurized inert gas from the gas inlet into the reaction cylinder, and supplies high frequency to the high frequency resonant cavity to generate plasma inside the reaction cylinder and blows out a plasma flow from the gas outlet of the reaction cylinder; a reaction vessel that has a linear cylindrical gas inlet and gas outlet and a cylindrical sample insertion port that is provided at right angles to the gas inlet and gas outlet, forming a substantially cross shape, and connects the gas inlet to the gas outlet of the reaction cylinder; and a sample moving mechanism that can be arranged in the direction of the sample insertion port of the reaction vessel, on which the sample can be detachably installed, and that allows the sample to be moved within the reaction vessel relative to the direction of the plasma flow that is blown out from the gas outlet. and a control means for detecting at least the temperature state of the sample in the reaction vessel and, based on the temperature state, adjusting the high frequency power so that the state of the plasma flow and the surface temperature of the sample are maintained in predetermined states, wherein the atmospheric pressure plasma processing apparatus is characterized in that the sample is exposed to the plasma flow and reacts with the plasma flow to perform surface processing of the sample.

3. An atmospheric pressure plasma processing apparatus according to claim 2, wherein the pressurized inert gas is argon gas or a gas obtained by mixing predetermined amounts of argon gas and helium gas.

4. An atmospheric pressure plasma processing apparatus that supplies a predetermined amount of argon gas or a gas mixture of argon gas and helium gas, and microwaves into a reaction cylinder to generate plasma inside the reaction cylinder and perform surface treatment on a sample with the plasma flow that is blown out from the reaction cylinder, the apparatus comprising: a gas inlet and a gas outlet in the reaction cylinder; a cooling cylinder that surrounds the outer periphery of the reaction cylinder; a high-frequency resonant cavity that surrounds the outer periphery of the cooling cylinder; a plasma generator that supplies pressurized argon gas as a rotating flow from the gas inlet into the reaction cylinder; a cooling medium that flows through the cooling cylinder to cool the reaction cylinder; a predetermined amount of microwaves that are supplied to the high-frequency resonant cavity to bring the high-frequency resonant cavity into a resonant state, thereby generating plasma inside the reaction cylinder and blowing out the plasma flow from the gas outlet of the reaction cylinder; 1. An atmospheric pressure plasma processing apparatus comprising: a reaction vessel having a linear gas inlet and gas outlet, and an insertion port for a cylindrical sample provided at right angles thereto, forming a substantially cross shape, the gas inlet being connected to a gas outlet part of the reaction cylinder; a sample moving mechanism that enables the sample to be moved within the reaction vessel relative to the blowing direction of a plasma flow blown out from the gas outlet part; and control means that detects at least the sample temperature state within the reaction vessel and, based on this, adjusts the microwave power so that the state of the plasma flow and the sample surface temperature are maintained in predetermined states; wherein the sample is exposed to the plasma flow to cause a reaction with the plasma flow, thereby performing surface processing of the sample.

5. An atmospheric pressure plasma processing apparatus according to claim 4, wherein said control means is capable of adjusting said high frequency power so that the plasma flow reaches directly onto the surface of the sample.

6. An atmospheric pressure plasma processing apparatus according to claim 4, wherein said control means is capable of adjusting said high frequency power so that the temperature of the surface of the sample that is being reached by said plasma flow is maintained at around 200°C.

7. An atmospheric pressure plasma processing apparatus as claimed in claim 4, characterized in that the control means can set the microwave power value supplied to the high frequency resonant cavity to the maximum value that allows the plasma flow to reach the sample surface directly and maintain the sample surface temperature at around 200°C.

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