JP2008204797A - Plasma processing method and device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma processing method and a plasma processing device capable of efficiently processing objects to give a substantially-uniform surface state and increase the adhesion property improving effect. <P>SOLUTION: To provide a method of processing the surface of an object 3 placed between two opposing electrodes 4 and 11 by applying a high-frequency electric power to the electrodes 4 and 11 to generate plasma while continuously feeding and discharging a prescribed gas, wherein the high-frequency electric power is intermittently applied to the electrodes in synchronism with time when the prescribed gas passes by the object 3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a surface modification treatment for improving the hydrophilicity and adhesiveness of a surface of a difficult-to-adhere base material having poor hydrophilicity such as a fluororesin, and generates plasma in the fluororesin etc. The present invention relates to a plasma processing method in which surface modification is performed by generating plasma in a pressure atmosphere and performing surface treatment.

  Conventionally, glow plasma treatment, which is a dry and clean treatment method, is known as a surface modification method (surface treatment method) for treating the surface of a substrate to impart hydrophilicity, adhesion, and the like to the surface.

  As surface treatment with glow plasma, low-pressure glow plasma treatment has been generally used, but in the case of low-pressure glow plasma treatment, since it is usually performed at a low pressure of 1.3 kPa or less, a large vacuum is used for the implementation. An apparatus is required, and there is a drawback that equipment costs and processing costs are increased, and heat is easily generated during processing, and it is difficult to apply to an object to be processed made of a low melting point material.

As a processing method for solving the drawbacks of the low-pressure glow plasma processing as described above, a processing method by an atmospheric pressure glow plasma method in which plasma processing is performed at atmospheric pressure has been developed. A treatment method for improving the adhesion of the surface has been proposed. (Patent Document 1)
Japanese Patent Laid-Open No. 04-145139

  However, in the conventional atmospheric pressure plasma treatment, it has been found that the surface modification effect is not sufficient, and the surface state of the object to be treated is not uniform. As a result of further investigation, it was found that the closer to the gas outlet, the lower the degree of surface treatment.

As a result of examining the cause of the problem that the degree of surface treatment becomes lower as the position is closer to the gas discharge port, the following was found.
That is, in the conventional atmospheric pressure plasma processing, a high-frequency power is continuously applied while a processing gas is continuously supplied from an inlet to an outlet in a state where an object to be processed is disposed between two electrodes facing each other. The object to be processed was processed by applying.

  However, when this method is used, the introduced gas is sequentially moved to and discharged from the discharge port while generating plasma, so that the concentration of the activated gas during the movement, that is, the amount of generated plasma is reduced. To do. As a result, the concentration of the active gas reaching the surface of the object to be processed is not constant within the surface of the object to be processed, and the degree of surface treatment is lower as the position is closer to the gas outlet. That is, in-plane variation occurred.

  One method to solve the above problem is to introduce a gas into the processing chamber, then seal it and apply high-frequency power continuously to perform processing, then replace the processing chamber gas and repeat the processing. However, in this method, an extra step such as frequent gas exchange, sealing or opening of the processing chamber is required, and there is a problem that productivity is lowered.

  For this reason, while the processing gas flows continuously from the introduction port to the discharge port, occurrence of in-plane variation of the processing object is suppressed, and the processing object can be processed efficiently into a substantially uniform surface state. Furthermore, a plasma processing method that further increases the effect of improving adhesiveness has been desired.

As a result of intensive studies, the inventor has applied plasma to the surface of the object to be processed by intermittently applying high-frequency power to both electrodes at a time interval longer than the time for the gas to pass through the object to be processed. As a result, the occurrence of in-plane variation of the object to be processed can be suppressed, the object to be processed can be efficiently processed into a substantially uniform surface state, and the effect of improving adhesiveness is high. As a result, the present invention has been completed.
The invention of each claim will be described below.

The invention described in claim 1
While continuously introducing and discharging a predetermined gas between two electrodes facing each other, high-frequency power is applied to both electrodes to cause plasma discharge in a pressure atmosphere that generates plasma, and is disposed between both electrodes. A plasma processing method for performing a surface treatment of a workpiece,
In the plasma processing method, the high-frequency power is intermittently applied to both electrodes in synchronization with a time during which the predetermined gas passes through the workpiece.

  In the plasma processing of this claim, high-frequency power is intermittently applied to both electrodes in synchronization with the time during which a predetermined gas passes through the workpiece. The time required for the predetermined gas to pass through the object to be processed here means the time required for the gas in contact with the object to be processed to be replaced with fresh gas. In addition, intermittent application to both electrodes in synchronization with the time when the predetermined gas passes through the object to be processed means that the predetermined gas is intermittently applied while the application gas is turned off during the time when the predetermined gas passes through the object to be processed. It means that it applies to. Since the present invention intermittently applies high-frequency power to both electrodes in synchronism with a predetermined time as described above, fresh gas is always filled during application. As a result, the amount of plasma that reaches the surface of the workpiece can be controlled to a certain level, the occurrence of in-plane variations in the workpiece can be suppressed, and the workpiece can be efficiently processed into a substantially uniform surface state. In addition, the effect of improving adhesiveness is further increased.

The predetermined gas in this claim may be any gas except air and suitable for plasma generation, and is not particularly limited. For example, an inert gas such as He, Ne, Ar, N ₂ or the like A gas containing a small amount of CO ₂ , halogen, or other gas that contains an inert gas as a main component and reacts with the object to be processed to impart a hydrophilic functional group to the surface of the object to be processed.

  Means for generating plasma include discharge such as corona discharge and arc discharge in addition to glow discharge, and means for generating plasma is not particularly limited in the present invention. From the viewpoint of more control, glow discharge is preferable. Here, in order to perform glow discharge, it is necessary to cover the surface of at least one of the electrodes with a solid dielectric, but ceramic, glass, plastic, etc. can be applied as the solid dielectric, and the material is particularly limited. Although not intended, ceramic or glass having a high dielectric constant is preferable.

  The shape and combination of electrodes are not particularly limited, such as a combination of flat electrodes facing each other, a combination of cylindrical electrodes facing each other, or a combination of a cylindrical electrode and a shaft electrode. .

  When the present invention is applied to thin film deposition, the growth rate of the thin film can be made uniform in the vicinity of the processing gas inlet and outlet.

Invention of Claim 2 is the said plasma processing method, Comprising:
The plasma treatment method is characterized in that the object to be treated is a resin selected from a fluororesin, a polyethylene terephthalate resin, and a polyphenylene sulfide resin.

In the invention of this claim, the effect of the present invention can be remarkably exerted in the surface modification treatment of a fluororesin that has been problematic in the hydrophilicity and adhesion of the surface of the object to be treated.
In the invention of this claim, the fluororesin that is the object to be processed is not particularly limited. For example, polytetrafluoroethylene (PTFE) suitable as a surface layer of a multi-layer endless belt or roller for image transfer or fixing of an image forming apparatus, Examples thereof include tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA).
In addition, the fluororesin in the present invention includes a fluorine-containing resin composition in which other substances such as a plasticizer and a filler are added to the fluorine resin in addition to a pure fluorine resin.

  Moreover, the invention of this claim can also exhibit the effect remarkably also in the polyethylene terephthalate (PET) resin and polyphenylene sulfide (PPS) resin used for an electronic material. That is, when the accelerated plasma (ions) collides with the resin surface, the adhesion of the ink during printing is improved and the printability is improved.

The invention described in claim 3
Two electrodes facing each other,
Gas introduction / discharge means for continuously introducing and discharging a predetermined gas between the electrodes,
And a high-frequency power application means for intermittently applying high-frequency power to both electrodes in synchronism with the time that the predetermined gas passes through the workpiece.

  The invention of this claim captures the invention of claim 1, which is a method invention, from the aspect of the apparatus.

  The plasma processing apparatus according to the invention of the present claim can increase the cost because the high frequency power applying means in the conventional plasma processing apparatus can be handled only by changing to the high frequency power applying means for intermittently applying the high frequency power. There is almost no.

  According to the present invention, while the processing gas flows continuously from the introduction port to the discharge port, occurrence of in-plane variation of the processing object is suppressed, and the processing object is efficiently processed into a substantially uniform surface state. In addition, the effect of improving adhesiveness is increased.

  Hereinafter, the present invention will be described based on the best mode by taking a transfer belt for an image forming apparatus as an example. Note that the present invention is not limited to the following embodiments. Various modifications can be made to the following embodiments within the same and equivalent scope as the present invention.

(A) Formation of surface layer First, formation of the surface layer of a transfer belt for an image forming apparatus, which is an object to be subjected to plasma treatment in the present embodiment, will be described.
FIG. 1 is a diagram conceptually illustrating a method for forming the surface layer 3 of the transfer belt according to the present embodiment. In FIG. 1, reference numeral 4 denotes a first cylindrical electrode. The first cylindrical electrode 4 is a stainless steel electrode having an inner diameter of 169.2 mm, a length of 500 mm, and a predetermined thickness. A predetermined amount of PFA dispersion (PFA grade 950HP) manufactured by Mitsui Dupont Fluoro Chemical Co. was applied to the inner peripheral surface of the first cylindrical electrode 4 and then baked at 400 ° C. on the inner surface of the first cylindrical electrode 4. A surface layer 3 having a length of 470 mm and a thickness of 8 μm is formed.

(B) Surface Plasma Treatment Secondly, the surface layer plasma treatment will be described.
a. Plasma treatment In this embodiment, plasma treatment is performed by generating glow plasma constantly in a fresh predetermined gas atmosphere by intermittently applying high-frequency power between both electrodes. Specifically, plasma is generated in synchronism with the time for applying high-frequency power to the time during which a predetermined gas passes through the workpiece.

By synchronizing the interval at which the high frequency power is applied to the time for which the predetermined gas passes through the object to be processed, the plasma is generated by always applying the processing space in a fresh predetermined gas atmosphere state. During the plasma processing, the activity of a predetermined gas can be kept substantially constant, and processing unevenness (in-plane variation) can be reduced.
This embodiment will be specifically described below.

2 and 3 are diagrams conceptually showing how the surface layer 3 according to the present embodiment is subjected to the plasma treatment. FIG. 2 is a front view. FIG. 3 is a diagram conceptually showing a shape when the position indicated by AA ′ is viewed in an arrow.
In FIG. 2, reference numeral 13 denotes a plasma processing chamber surrounded by a second pressure vessel 12 made up of a cylindrical vessel and a lid.

  Inside the plasma processing chamber 13, a second cylindrical electrode having the same length as the first cylindrical electrode 4 and an outer diameter of 152 mm is smaller than the inner diameter of the first cylindrical electrode 4. 11 is installed. Next, the 1st cylindrical electrode 4 which formed the surface layer 3 in the internal peripheral surface is installed so that the 2nd cylindrical electrode 11 may be surrounded. At the same time when the first cylindrical electrode 4 is installed, the first cylindrical electrode 4 is positioned so that the axis of the first cylindrical electrode 4 and the axis of the second cylindrical electrode 11 coincide with each other. The two cylindrical electrodes having different diameters form a double cylinder, and the surface layer 3 is disposed between the two cylindrical electrodes.

  The second cylindrical electrode 11 is connected to one electrode of the high-frequency power source 20 installed outside, and the first cylindrical electrode 4 is grounded (application means not shown). As shown in FIG. 3, the first cylindrical electrode 4 includes a stainless steel cylinder 41, and the second cylindrical electrode 11 includes an aluminum cylinder 111 and a Pyrex having an outer peripheral surface of 4 mm in thickness. The solid dielectric 112 is covered with glass (manufactured by Asahi Techno Glass).

  An air supply pipe 14 for supplying a predetermined gas to the plasma processing chamber 13 and a vacuum exhaust pipe 18 for evacuating the gas from the plasma processing chamber 13 are attached to the lid of the second pressure vessel 12. A valve 15 and a valve 19 are attached to the air supply pipe 14 and the vacuum exhaust pipe 18, respectively. An exhaust pipe 16 for releasing the gas in the plasma processing chamber 13 to the outside is attached to the bottom wall of the second pressure vessel 12, and a valve 17 is attached to the exhaust pipe 16. The supply pipe 14 is connected to a high-pressure cylinder (not shown) of a predetermined gas (He gas), and the vacuum exhaust pipe 18 is connected to a second vacuum pump 21.

  The valve 15 and the valve 17 are closed, the valve 19 is opened, the second vacuum pump 21 is operated, and the air in the plasma processing chamber 13 is supplied to an HNT-221A type pressure gauge (pressure range manufactured by Daiichi Keiki Seisakusho). : -0.1 MPa to 0.1 MPa centered on atmospheric pressure (not shown) is excluded until it indicates -0.1 MPa. Next, the valve 19 is closed, the valve 15 is opened, and a predetermined gas (He gas) is supplied from the supply pipe 14 to the plasma processing chamber 13 at a flow rate of 10 l / min, and the pressure in the plasma processing chamber generates a predetermined plasma. Supply until pressure (atmospheric pressure) is reached. After the pressure in the plasma processing chamber 13 reaches a predetermined pressure (atmospheric pressure) for generating plasma, the valve 17 is slightly opened while supplying a predetermined gas (He gas) from the valve 15, and the plasma processing chamber The gas in 13 can be discharged outside. That is, the opening degree of the valve 17 is adjusted so that the pressure in the plasma processing chamber is maintained at a predetermined pressure (atmospheric pressure) for generating plasma.

Next, a high frequency power of 700 W, voltage 30 kV, and frequency 20 kHz is intermittently applied between the cylindrical electrodes 4 and 11, and only in the space between the cylindrical electrodes 4 and 11 is applied. Glow plasma is generated and plasma treatment of the surface layer 3 is performed. Specifically, 30 cycles of application (total application time: 60 seconds) are performed, with high-frequency power applied for 2 seconds and applied for 2 seconds off as one cycle.
By providing an application off time of 2 seconds, the plasma processing is performed in a state where the old and new gases in the plasma processing chamber are replaced.

  In the present embodiment, by synchronizing the application off time with the time for which the predetermined gas passes through the object to be processed, the plasma is generated by always applying the process space in a fresh predetermined gas atmosphere state. Therefore, the activity of the predetermined gas can be kept substantially constant during the plasma processing, and processing unevenness (in-plane variation) can be reduced.

(C) Production and performance evaluation of transfer belt Next, a transfer belt is produced by applying the surface layer produced in the above embodiment.
a. Configuration of Transfer Belt First, the configuration of the transfer belt according to the present embodiment will be described.
The transfer belt is mainly composed of three layers: a base layer responsible for mechanical strength, an intermediate layer for imparting elasticity to the belt, and a surface layer responsible for a transfer function.
FIG. 4 is a diagram conceptually showing the configuration of the transfer belt for the image forming apparatus according to the present embodiment, and is an enlarged view of a part of the cross section of the transfer belt. In FIG. 4, 1 is a base layer based on a polyimide resin, 2 is an intermediate layer composed of an elastomer based on aqueous urethane, and 3 is a surface layer composed of a fluororesin excellent in toner releasing properties. Adjacent layers and layers are bonded. In the transfer belt according to the present invention, the surface layer 3 and the intermediate layer 2 are directly bonded without using an adhesive layer.
The thickness of each layer is 60 μm for the base layer, 200 μm for the intermediate layer, and 8 μm for the surface layer.

b. Next, a procedure for manufacturing the transfer belt according to the present embodiment will be described.
In the present embodiment, the intermediate layer 2 is formed by forming a laminated body in which the base layer 1 and the intermediate layer 2 are laminated, fitting the inner peripheral surface with the surface layer 3 subjected to the plasma treatment, and pressing both. And the surface layer 3 are adhered to form a transfer belt.

The formation of each layer constituting the transfer belt will be described below.
c. Formation of a laminate with a base layer and an intermediate layer laminated While rotating a drum-shaped mold, a predetermined amount of polyimide varnish is applied to the outside, and then the mold is heated to carry out an imidization reaction. A cylindrical base layer 1 made of polyimide resin having a thickness of 60 μm is formed around the mold.
Next, the base layer 1 is once removed from the drum mold and fitted to the outer peripheral surface of another drum mold.
Separately, a thickening agent is added to aqueous urethane to obtain a viscosity of about 10 Pa · s, a defoamed urethane solution is prepared, and a predetermined amount is applied onto the surface of the base layer 1. After coating, moisture is dried at room temperature, and further annealed at 160 ° C. to form an intermediate layer 2 made of polyurethane having a thickness of 200 μm on the surface of the base layer 1 to obtain a cylindrical laminate.
FIG. 5 is a diagram conceptually illustrating a state in which a laminated body including the base layer 1 and the intermediate layer 2 is formed on the outer peripheral surface of the drum-shaped mold 5.

Next, the adhesion between the laminate and the surface layer will be described.
d. Adhesion of Laminate and Surface Layer Here, a specific method of adhering the intermediate layer 2 and the surface layer 3 of the laminate by fitting the laminate to the surface layer 3 and pressing them will be described.
FIG. 6 is a diagram conceptually showing an adhesion process for adhering the intermediate layer 2 and the surface layer 3 by pressing the laminate and the surface layer 3.
In FIG. 6, 6 is a kind of fluid container, which is a hollow cylindrical container (hereinafter referred to as “waterback”) made of a silicon rubber film and closed at both ends. The cylindrical laminate is removed from the drum mold 5 and fitted into the outer periphery of the water bag 6.

  The water bag 6 fitted with the laminated body is inserted inside the first cylindrical electrode 4 having the surface layer 3 formed on the inner peripheral surface, and the water bag 6 and the first cylindrical electrode 4 are connected to the first withstand voltage. It is installed inside the vacuum chamber 7 surrounded by the container 8. Next, the pump 9 is operated to press the fluid into the water bag 6 to raise the water back pressure to 0.5 MPa, and at the same time, the first vacuum pump 10 is operated to make the vacuum chamber 7 vacuum. .

The laminated body on the outer periphery of the water bag 6 and the surface layer 3 on the inner periphery of the first cylindrical electrode 4 by the body portion of the water bag 6 inflated by the internal pressure and the inner surface of the first cylindrical electrode 4 are: They are pressed against each other. Since the water bag 6 is a film made of silicon rubber, the entire resin layer uniformly presses the resin layer against the inner surface of the first cylindrical electrode 4. Moreover, since the inside of the vacuum chamber 7 is evacuated at this time, it will be pressed more effectively. As a result, the intermediate layer 2 and the surface layer 3 are firmly bonded. However, as described above, in the present embodiment, the plasma treatment is performed on the inner peripheral surface of the surface layer 3 prior to pressing.
In this way, a transfer belt comprising three layers of the base layer 1, the intermediate layer 2, and the surface layer 3 is obtained.

  Based on the present embodiment, a transfer belt having excellent transfer function and excellent durability can be obtained.

It is a figure which shows notionally the formation process of the surface layer of the belt for transfer. It is the conceptual diagram which looked at the plasma processing which concerns on embodiment of this invention from the front. It is the conceptual diagram which looked at the plasma processing which concerns on embodiment of this invention from the upper side. FIG. 3 is a partially enlarged cross-sectional view of a transfer belt. It is a figure which shows notionally the formation process of the laminated body of the belt for transfer. It is a figure which shows notionally the adhesion process of the surface layer of a transfer belt, and a laminated body.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base layer 2 Intermediate | middle layer 3 Surface layer 4 1st cylindrical electrode 5 Drum-shaped metal mold 6 Water back 7 Vacuum chamber 11 2nd cylindrical electrode 12 2nd pressure | voltage resistant container 13 Plasma processing chamber 14 Supply pipe 16 Exhaust pipe 18 Vacuum exhaust pipe 20 High frequency power supply 21 Second vacuum pump

Claims (3)

While continuously introducing and discharging a predetermined gas between two electrodes facing each other, high-frequency power is applied to both electrodes to cause plasma discharge in a pressure atmosphere that generates plasma, and is disposed between both electrodes. A plasma processing method for performing a surface treatment of a workpiece,
A plasma processing method, wherein the high-frequency power is intermittently applied to both electrodes in synchronization with a time during which the predetermined gas passes through the workpiece.   The plasma processing method according to claim 1, wherein the object to be processed is a resin selected from a fluororesin, a polyethylene terephthalate resin, and a polyphenylene sulfide resin. Two electrodes facing each other,
Gas introduction / discharge means for continuously introducing and discharging a predetermined gas between the electrodes,
And a high-frequency power application means for intermittently applying high-frequency power to both electrodes in synchronism with the time during which the predetermined gas passes through the workpiece.

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