Surface processing device, surface processing method, method for manufacturing surface-coated resin substrate, and surface-coated fluororesin substrate

Abstract

To provide a surface processing device and a surface processing method capable of efficiently modifying a surface of a resin substrate.MEANS FOR SOLVING THE PROBLEM: A surface processing device for performing plasma irradiation processing on a surface of a resin substrate includes: a substrate support portion having a first electrode; a plasma processing portion having a plurality of second electrodes; and a gas supply portion. The plurality of second electrodes are arranged in parallel at intervals, and a surface of the plurality of second electrodes facing the resin substrate has a substantially rectangular shape. The present disclosure also provides: a surface processing method for a resin substrate using the surface processing device; a method for manufacturing a surface-coated resin substrate; and a surface-coated fluororesin substrate manufactured by the same.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a surface treatment device, a surface treatment method, a method for producing a surface-coated resin substrate, and a surface-coated fluororesin substrate. [Background technology]

[0002] Resin substrates are functional materials with a variety of functions and are used in a wide range of applications. However, resin substrates can have drawbacks that make them unsuitable for their final applications, and most of these drawbacks are related to the surface properties of the resin substrate. For this reason, various surface treatment devices and methods have been developed and put into practical use as surface treatment technologies for modifying the surface of resin substrates. Among these surface treatment technologies, plasma treatment is advantageous in that it can modify only the surface of the resin substrate by irradiating the surface of the resin substrate with plasma. Patent Document 1 discloses a surface treatment device and a surface treatment method in which plasma is generated between a pair of opposing electrodes under pressure near atmospheric pressure, and a polyethylene substrate (100 mm × 100 mm, thickness: 40 μm) placed between the electrodes is plasma treated in an atmosphere with a monomer concentration of 1%, thereby forming a polymer film on the surface of the resin substrate and modifying the surface of the polyethylene substrate (resin substrate). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 10-287757 Summary of the Invention [Problem to be solved by the invention]

[0004] Resin substrates used for specific applications are available on the market in large surface areas, such as sheets and rolls. There is a high demand for surface treatment devices and methods that can efficiently modify the surface of large-area resin substrates. However, the plasma treatment surface treatment device disclosed in Patent Document 1 suffers from the problem that monomer is easily supplied to the edges of the resin substrate, but is difficult to supply to the center of the resin substrate, resulting in variations in the performance of the polymerized film. In other words, the larger the resin substrate, the greater the variation in the performance of the polymerized film formed by plasma treatment. Therefore, even if the surface treatment device disclosed in Patent Document 1 is enlarged, it has been considered technically difficult to immediately apply it to a surface treatment method for large-area resin substrates. Furthermore, a method for generating uniform plasma by uniformly discharging electricity between large-area electrodes when the area of a pair of electrodes is increased has not yet been established.

[0005] The present disclosure has been made in view of the above circumstances and provides a surface treatment device capable of performing uniform plasma treatment on the surface of a flat resin substrate. The present disclosure also provides a surface treatment method using the surface treatment device, a method for producing a surface-coated resin substrate, and a surface-coated fluororesin substrate produced by the method for producing a surface-coated resin substrate. [Means for solving the problem]

[0006] From a first aspect, the present disclosure provides a surface treatment apparatus for performing plasma irradiation treatment on a first surface of a resin substrate, the surface treatment apparatus comprising: a first electrode in the form of a flat plate arranged opposite to the second surface of the resin base; a plurality of second electrodes disposed opposite the first surface of the resin base; a plasma vessel containing a plurality of second electrodes; a power supply connected to at least one of the first electrode and the second electrode; a gas supply unit configured to supply a monomer gas and an inert gas into the plasma chamber; The surface treatment device provides a surface in which the second electrodes are arranged in parallel at intervals, and the surfaces of the second electrodes facing the first surface have a substantially rectangular shape.

[0007] From a second aspect, the present disclosure provides a surface treatment apparatus for plasma irradiation treatment of a first surface of a resin substrate, the surface treatment apparatus comprising: a plurality of discharge electrode pairs arranged opposite to each other on a first surface of the resin base; a plasma vessel containing a plurality of discharge electrode pairs; and a power supply device connected to the plurality of discharge electrode pairs; a gas supply unit configured to supply a monomer gas and an inert gas into the plasma chamber; The surface treatment apparatus provides a plurality of discharge electrode pairs arranged in a plurality of rows.

[0008] From a third aspect, the present disclosure provides a surface treatment device for plasma irradiation treatment of a first surface of a resin substrate, the surface treatment device comprising: a plurality of discharge electrode pairs arranged opposite to each other on a first surface of the resin base; a plasma vessel containing a plurality of discharge electrode pairs; a power supply connected to the discharge electrode pair; a gas supply unit configured to supply a monomer gas and an inert gas into the plasma chamber; The surface treatment apparatus includes a plurality of discharge electrode pairs arranged in a row.

[0009] From a fourth aspect, the present disclosure provides a surface treatment method including a surface treatment step of treating the surface of a resin substrate by plasma irradiation using any one of the surface treatment devices. From a fifth aspect, the present disclosure provides a method for producing a surface-coated resin substrate, including a surface treatment step of treating the surface of the resin substrate with plasma irradiation using any one of the surface treatment devices. From a sixth aspect, the present disclosure provides a surface-coated fluororesin substrate manufactured by the method for manufacturing a surface-coated resin substrate, the surface-coated fluororesin substrate comprising a fluororesin substrate and a (meth)acrylic resin layer provided on the fluororesin substrate, wherein the (meth)acrylic resin layer is chemically bonded to the fluororesin substrate. [Effects of the Invention]

[0010] According to the surface treatment device and surface treatment method of the present disclosure, the surface treatment of a resin substrate can be performed uniformly, and therefore, even when the resin substrate has a large surface area, it may be possible to perform surface modification more efficiently than with conventional techniques. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram of a surface treatment apparatus according to an embodiment of the present disclosure. [Figure 2A] 2 is a front view showing the relationship between a plasma torch and a resin base in the surface treatment device of FIG. 1. FIG. [Figure 2B] 2 is a side view showing the relationship between a plasma torch and a resin base in the surface treatment device of FIG. 1. FIG. [Figure 3A] 1 is a schematic cross-sectional view illustrating a relationship between a plasma torch and a resin substrate in a surface treatment device according to an embodiment of the present disclosure. [Figure 3B] FIG. 3B is a schematic cross-sectional view taken along the dotted line AA' in FIG. 3A. [Figure 3C] FIG. 3C is a schematic cross-sectional view showing an enlarged view of a portion B surrounded by a dotted line in FIG. 3B. [Figure 4] 1 is a graph showing the results of acrylic acid concentration measurement using a detector tube. [Figure 5] FIG. 5(a) is a schematic diagram of the peel test device, and FIG. 5(b) is an explanatory diagram of how to cut out the test piece to be used in the peel test. [Figure 6] 6(a) to 6(c) are graphs showing the results of measuring the peel strength of fluororesin substrates produced under test conditions with different acrylic acid temperatures in the steam generation tank. [Figure 7]7(a) to 7(c) are graphs showing the results of measuring the peel strength of fluororesin substrates produced under test conditions with different flow rate ratios of the monomer-containing gas and the inert gas. [Figure 8] 8(a) and 8(b) are graphs showing the measurement results of the peel strength of fluororesin substrates manufactured under test conditions with different plasma treatment times. [Figure 9] 9(a) and 9(b) are graphs showing the results of measuring the peel strength of fluororesin substrates manufactured under test conditions in which the voltages applied to the second electrodes 2a to 2e were different. DETAILED DESCRIPTION OF THE INVENTION

[0012] In this specification, the "first surface of the resin substrate" refers to the surface of the resin substrate that is the target of plasma treatment, and the "second surface of the resin substrate" refers to the opposite surface that is not the target of plasma treatment. The resin substrate will be described later in the section "First surface treatment device."

[0013] [First embodiment: First surface treatment device] Hereinafter, one embodiment of the present disclosure will be described with reference to the drawings (FIGS. 1, 2A, and 2B). The configurations shown in the drawings and the following description are merely examples, and the scope of the present disclosure is not limited to those shown in the drawings and the following description. Furthermore, the structure of the surface treatment device 40 of this embodiment will be described based on the top, bottom, left, and right of the drawings. For example, the first surface of the resin base 30 can also be expressed as the upper surface of the resin base 30.

[0014] FIG. 1 is a schematic diagram of a surface treatment device 40 according to an embodiment of the present disclosure. The surface treatment device 40 includes a substrate support unit 9 having a first electrode 1 (see FIG. 2A), a plasma treatment unit 50 having second electrodes 2a-2e (see FIG. 2A), and a gas supply unit 8. The substrate support unit 9 supports a resin substrate 30 as a sample. In this embodiment, the substrate support unit 9 is a part of a belt conveyor device 10. Note that the substrate support unit 9 is not limited to the belt conveyor device 10 and may be, for example, a slide transport device that slides the resin substrates 30 one by one on a table using a transport arm. The plasma treatment unit 50 is disposed near the upper surface of the substrate support unit 9 and performs plasma treatment on the upper surface (first surface) of the resin substrate 30 supported by the substrate support unit 9. The gas supply unit 8 supplies gases required for plasma treatment of the upper surface of the resin substrate 30 to the plasma treatment unit 50. The substrate support unit 9, the plasma processing unit 50, and the gas supply unit 8 will be described in detail below.

[0015] 2A is a front view showing the relationship between the plasma torch 4 and the resin substrate 30 in the surface treatment device 40 of FIG. 1, and FIG. 2B is a side view showing the relationship between the plasma torch 4 and the resin substrate 30 in the surface treatment device 40 of FIG. 1. The substrate support unit 9 is provided between the first electrode 1 and the plurality of second electrodes 2a-2e to support the resin substrate 30 so that the distances between the first electrode 1 and the plurality of second electrodes 2a-2e and the resin substrate 30 are approximately uniform. The belt conveyor device 10, which is the substrate support unit 9, is provided with a laminate of electrodes and dielectrics at the location where the plasma treatment unit 50 (see FIG. 1) is disposed. Specifically, a laminate including an upper dielectric 13a, a first electrode 1 laminated on the lower surface of the upper dielectric 13a, and a lower dielectric 13b laminated on the lower surface of the first electrode 1 is provided near the lower surface of the upper belt of the belt conveyor device 10 via the seal portion 14 of the plasma container 5. In this embodiment, the substrate support unit 9 constitutes a part of the belt conveyor device 10, and thus the resin substrate 30 can be moved so that plasma can be irradiated at a desired location on the upper surface (first surface) of the resin substrate 30. The belt conveyor entrance / exit of the plasma vessel 5 is sealed with a seal unit 14 to prevent air from entering through the belt conveyor entrance / exit. If the resin substrate 30 is a film wound in a roll, the substrate support unit 9 may be the core material of the roll. The substrate support unit 9 may also be equipped with a heating and cooling means for the resin substrate 30. The temperature inside the plasma vessel 5 during discharge is usually room temperature (approximately 25°C). However, depending on the type of monomer used, it may be preferable to heat and cool the gas inside the plasma vessel. The substrate support unit 9 is equipped with a heating and cooling means, which facilitates temperature adjustment. For example, when using a monomer with a high boiling point, it is preferable to heat it to maintain a gaseous state. The substrate support 9 may be made of any material or have any structure that does not prevent dielectric barrier discharge between the first electrode 1 and the second electrodes 2a to 2e of the plasma processing section 50 (see FIG. 1). Any one of the first electrode 1, the dielectric 13a, and the seal 14 of the plasma container 5 may also serve as the substrate support 9.

[0016] As shown in FIGS. 2A and 2B, the first electrode 1 is not particularly limited as long as it has a flat plate shape. Examples of the first electrode 1 include electrodes containing stainless steel, copper, copper alloy, iron, and graphite. Because the first electrode 1 may be exposed to a monomer gas atmosphere, an electrode made of a material with low corrosiveness is advantageous, and a suitable example is a stainless steel electrode. The width, length, and height of the first electrode 1 may be determined appropriately depending on the size of the first surface of the resin substrate 30, the output of the power supply device 7, and other factors. Generally, the width, length, and height of the first electrode 1 are in the ranges of 100 mm to 200 mm, 100 mm to 1000 mm, and 0.5 mm to 20 mm, respectively, and preferably 100 mm to 150 mm, 300 mm to 600 mm, and 5 mm to 12 mm, respectively. In the above embodiment, both sides of the first electrode 1 are covered with the dielectrics 13a and 13b. Alternatively, only the surface facing the second surface (lower surface) of the resin substrate 30 may be covered with the dielectric 13a. The dielectrics 13a and 13b may be made of any material or structure that does not inhibit the dielectric barrier discharge that occurs between the first electrode 1 and the plurality of second electrodes 2a to 2e. The dielectric barrier discharge is a discharge that occurs when a dielectric is disposed on at least one of the opposing electrodes and an AC voltage or pulse voltage is applied between the electrodes. The width and length of the dielectrics 13a and 13b are preferably equal to or greater than the width and length of the first electrode 1. Furthermore, if the thickness of the dielectrics 13a and 13b is too thick, a high voltage is required to generate the dielectric barrier discharge. If the thickness of the dielectrics 13a and 13b is too thin, a dielectric breakdown may occur when an AC voltage is applied, resulting in an arc discharge and the generation of heat. Generally, the thickness of the dielectrics 13a and 13b is appropriately determined within a range of 0.5 mm to 15 mm, and preferably 1 mm to 10 mm. Examples of the dielectrics 13a and 13b in the present disclosure include solid dielectrics such as resin, glass, silicon dioxide, aluminum oxide, zirconium dioxide, and barium titanate. The dielectrics 13a and 13b are preferably made of a material with high insulating properties so as to be able to withstand high voltage treatment, and a material with a high relative dielectric constant so as to have good electrical efficiency. A suitable example is PTFE.

[0017] The plasma processing unit 50 includes a plasma torch 4 having a plurality of second electrodes 2a to 2e, a plurality of second electrode support parts 3a to 3e that respectively support the plurality of second electrodes 2a to 2e, and a rectifying cover 43 that houses the plurality of second electrodes 2a to 2e, a plasma container 5 having a fixing member 45 that fixes the plasma torch 4, and a power supply unit 7.

[0018] 2A and 2B, there are five second electrodes in the plasma torch 4. The second electrodes 2a to 2e are rectangular parallelepipeds, the surface facing the first surface of the resin base 30 is rectangular, and the cross section perpendicular to the first surface of the resin base 30 is flat. 2A, there are five second electrodes 2a-2e, but the number may be four or less, or six or more. The number of second electrodes 2a-2e may be determined appropriately depending on the size of the first electrode 1, the size of the resin base 30, and the size of each of the second electrodes 2a-2e. The second electrodes 2a-2e may be made of any material or have any structure that allows each of the second electrodes 2a-2e to face the first electrode 1 and generate a dielectric barrier discharge. The second electrodes 2a-2e have a substantially rectangular shape on the surface facing the first surface of the resin substrate 30. The substantially rectangular shape is not limited to a rectangular shape and includes, for example, a rectangle with rounded corners and shapes with rounded ends in the longitudinal direction. Furthermore, the shape of a cross section perpendicular to the longitudinal direction of the second electrodes 2a-2e and perpendicular to the first surface of the resin substrate 30 is not particularly limited, and the surface facing the first surface of the resin substrate 30 may be flat, rounded, or dome-shaped. When an AC voltage is applied to the second electrodes 2a-2e, the electric field may be strong at the corners and straight lines. Therefore, the surface of the second electrodes 2a-2e facing the first surface of the resin substrate 30 is preferably rectangular, and the cross section perpendicular to the first surface of the resin substrate 30 is preferably flat. Furthermore, it is preferable that the second electrodes 2a-2e have the same shape. The size of each of the second electrodes 2a-2e may be determined appropriately depending on the size of the first electrode 1, the size of the first surface of the resin base 30, the output of the power supply 7, and the like. Generally, the width, length, and height of each of the second electrodes 2a-2e are in the ranges of 3 mm to 100 mm, 100 mm to 1000 mm, and 0.5 mm to 20 mm, respectively, and preferably 3 mm to 20 mm, 300 mm to 600 mm, and 5 mm to 12 mm, respectively. The second electrodes 2a-2e are connected in parallel when connected to a power supply 7. Examples of the second electrodes 2a-2e include electrodes containing stainless steel, copper, copper alloy, iron, and graphite. Because the first electrode 1 may be exposed to a monomer gas atmosphere, an electrode made of a material with low corrosiveness is advantageous, and a suitable example is a stainless steel electrode. The second electrodes 2a-2e are arranged in parallel with a gap therebetween. The gap between the second electrodes 2a-2e is not particularly limited, but it is preferable that a space exist between adjacent second electrodes 2a-2e through which gas can flow. If the gap between the second electrodes 2a-2e is too wide, the dielectric barrier discharge may be intermittent, potentially preventing uniform discharge from achieving plasma treatment. The gap between the second electrodes 2a-2e is, for example, 0.3 to 3 times, preferably 0.5 to 2.5 times, and more preferably 1 to 2 times the width of each of the second electrodes 2a-2e. The gap between adjacent second electrodes through which gas can flow allows the monomer gas to be rapidly supplied to the space between the opposing first electrode 1 and second electrode 2a-2e, making it possible to perform surface treatment of a resin substrate while maintaining a uniform distribution of the monomer gas concentration in the space between the electrodes. By having the plurality of second electrodes 2a to 2e configured as described above, the first surface treatment device of the present disclosure can perform a uniform surface treatment even when the resin base 30 has a large area.

[0019] The second electrodes 2a-2e are supported by second electrode support members 3a-3e. The shape of the second electrode support members 3a-3e is not particularly limited as long as it does not interfere with the discharge occurring between the first electrode 1 and the second electrodes 2a-2e and the flow of gas between adjacent second electrodes, and is preferably a rod shape such as a rectangular pillar or a cylinder. The second electrode support members 3a-3e are bonded to the surface of the resin base 30 that does not face the first surface, and preferably a space is provided around the second electrode support members 3a-3e through which gas can flow. The second electrode support members 3a-3e may include a conductor connecting the power supply 7 and the second electrodes 2a-2e. If the second electrode support members 3a-3e are composed only of a conductor, they are preferably made of the same material as the second electrodes 2a-2e. The size of each of the second electrode support portions 3a-3e may be determined appropriately depending on the size of the second electrodes 2a-2e. Generally, the width of the second electrode support portions 3a-3e is the same as the width of the second electrodes 2a-2e. The height of the second electrode support portions 3a-3e is not particularly limited, but if the second electrode support portions 3a-3e are conductive, a too low height may cause partial electric field concentration between the first electrode 1 and the second electrodes 2a-2e. For this reason, the height of the second electrode support portions 3a-3e is preferably 0.8 cm or more, for example, between 1.0 cm and 5.0 cm. The first electrode 1 and the second electrodes 2a-2e are arranged so that the distance between the opposing electrodes is approximately constant in order to prevent localized electric field concentration. The distance between the first electrode 1 and the second electrodes 2a-2e is not particularly limited as long as a dielectric barrier discharge can be generated between the electrodes, and is generally set appropriately in the range of several mm to several cm, and preferably 2 mm to 2 cm.

[0020] The plasma torch 4 is provided so as to irradiate plasma onto the first surface of the resin base 30. The plasma torch 4 includes a plurality of second electrodes 2a to 2e, and further includes a rectifying cover 43. The rectifying cover 43 has a U-shaped structure and accommodates the multiple second electrodes 2a-2e. The rectifying cover 43 is configured to allow the monomer gas and inert gas supplied from the gas supply unit 8 to flow in the longitudinal direction of the first electrode 1 and the multiple second electrodes 2a-2e. This allows the monomer gas to be quickly supplied between the first electrode 1 and the multiple second electrodes 2a-2e, helping to maintain a uniform concentration distribution of the monomer gas in the space between the electrodes. While the rectifying cover 43 may be configured to accommodate the multiple second electrodes 2a-2e, a smaller space within the rectifying cover 43 is advantageous because it makes it easier to regulate the gas flow. Furthermore, a smaller gap between the rectifying cover 43 and the seal unit 14 of the plasma container 5 (described later) is advantageous as long as it does not impede the movement of the resin substrate 30. The rectifying cover 43 is not limited to a U-shaped structure, and all corners may be right angles.

[0021] The plasma vessel 5 is a substantially sealed box-shaped vessel. The volume of the plasma vessel 5 is not particularly limited as long as it is large enough to accommodate the components necessary for the surface treatment device 40 of the present disclosure. However, since it is advantageous to completely replace the air in the plasma vessel 5 with gas supplied from a gas supply unit during plasma treatment, it is preferable that the volume of the plasma vessel 5 not be excessively large. To enable the state of the plasma to be confirmed, the cover plate 41 of the plasma vessel 5 is advantageously light-transmitting, and suitable examples thereof are glass or acrylic. Since the inside of the plasma vessel 5 may be exposed to a monomer gas atmosphere, from the viewpoint of corrosion prevention, the cover plate 41 may contain a less corrosive material, and a suitable example thereof is stainless steel. The plasma container 5 has a seal portion 14 provided between the first electrode 1 and the resin base 30. The seal portion 14 may also serve as the dielectric 13a. From the viewpoint of improving the airtightness of the plasma container 5, the seal portion is advantageously made of a rubbery resin. Furthermore, from the viewpoint of chemical resistance, a preferred example is a fluororesin, specifically PTFE.

[0022] The power supply device 7 is, for example, a high-frequency power supply device, and is configured to apply an AC voltage between the first electrode 1 and the plurality of second electrodes 2a to 2e. In one embodiment, the output terminals of the power supply device 7 are connected to the plurality of second electrodes 2a to 2e, and the first electrode 1 is connected to earth. The output of the power supply device 7 can be, for example, 50 W or more and 300 W or less. The output frequency of the power supply device 7 can be, for example, 20 kHz or more and 35 kHz or less. The power supply device 7 may, for example, pulse-control the output voltage. The conditions for applying the AC voltage to the electrodes will be described later.

[0023] The gas supply unit 8 includes a gas cylinder 20, a steam generation tank 21, and a power supply device 29 for the steam generation tank 21, and is configured to supply the monomer gas and the inert gas into the plasma vessel 5, particularly to the inside of the rectifying cover 43. In one embodiment, the gas supply unit 8 is configured to mix the monomer gas and the inert gas and then supply the mixture to the plasma vessel 5. In this specification, an inert gas refers to a gas that has little reactivity with the resin substrate or monomer. Examples of inert gases include rare gases such as helium and argon, and nitrogen gas. The inert gas preferably has a purity of 90% or more, more preferably 95% or more, and even more preferably 98% or more. Furthermore, oxygen has the function of deactivating radicals contained in the plasma, so it is preferable to avoid its inclusion as much as possible. Specifically, argon gas with a purity of 99.99% is preferred. The inert gas is supplied from, for example, a gas cylinder 20. The supply path of the inert gas may include, in addition to the gas cylinder, devices necessary for gas supply, such as gas piping, a flow rate limiting valve, a pressure adjusting valve, a flow meter, or a flow controller.

[0024] In this specification, a monomer refers to a compound having a polymerizable unsaturated bond. The monomer is not particularly limited, and any known monomer may be used. Specific examples of the monomer include (meth)acrylic monomers such as acrylic acid or its derivatives, methacrylic acid or its derivatives, acetylene-based monomers, and alcohol-based monomers. The above-mentioned monomers may be used alone or in combination. In a specific embodiment, the monomer is a (meth)acrylic monomer. The acrylic monomer is not particularly limited, and any known monomer can be used.Specifically, acrylic acid derivatives such as methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, tridecyl acrylate, stearyl acrylate, cyclohexyl acrylate, propyl acrylate, benzyl acrylate, isopropyl acrylate, sec-butyl acrylate, acrylic acid, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, dimethylaminoethyl acrylate, diethylaminoethyl acrylate, glycidyl acrylate, tetrahydrofurfuryl acrylate, allyl acrylate, ethylene glycol diacrylate, triethylene glycol diacrylate, tetraethylene glycol diacrylate, 1,3-butylene glycol diacrylate, trimethylolpropane triacrylate, 2-ethoxyethyl acrylate, ethoxyethoxyethyl acrylate, 2-methoxyethyl acrylate, phenoxyethyl acrylate, phenoxypolyethylene glycol acrylate, and dimethylaminoethyl acrylate methyl chloride salt, methyl methacrylate, ethylene methacrylate, butyl methacrylate, butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, tridecyl methacrylate, stearyl methacrylate, cyclohexyl methacrylate, propyl methacrylate, benzyl methacrylate, isopropyl methacrylate, sec-butyl methacrylate, methacrylic acid, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, glycidyl methacrylate, tetramethyl methacrylate Examples of methacrylic acid derivatives include trihydrofurfuryl, allyl methacrylate, ethylene glycol dimethacrylate, triethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, trimethylolpropane trimethacrylate, 2-ethoxyethyl methacrylate, ethoxyethoxyethyl methacrylate, 2-methoxyethyl methacrylate, phenoxyethyl methacrylate, phenoxypolyethylene glycol methacrylate, and dimethylaminoethyl methacrylate methyl chloride salt.Of the above (meth)acrylic monomers, acrylic acid, 2-hydroxyethyl methacrylate, and glycidyl methacrylate are preferred, and acrylic acid is particularly preferred.

[0025] The monomer gas can be used as is if the monomer itself is gaseous at room temperature, or can be converted to gas by heating if it is in liquid or solid form. If the monomer gas is liquid at room temperature or can be liquefied by heating, the monomer gas can be obtained by bubbling the liquid. Alternatively, the monomer gas can be supplied as a monomer-containing gas using the above-mentioned inert gas as a carrier gas. The monomer-containing gas can be supplied by circulating an inert gas through the headspace of the vapor generation tank 21. The vapor generation tank 21 is a liquid tank that generates vapor of the organic compound 23. The vapor generation tank 21 is a sealed liquid tank that includes a liquid tank for storing a liquid monomer (organic compound 23), a gas inlet 24 that supplies an inert gas to a headspace 26 above the liquid surface, and a gas outlet 25 that discharges the gas from the headspace 26. The headspace 26 is a space that includes the headspace above the liquid surface of the monomer. Furthermore, the gas inlet 24 and the gas outlet 25 are arranged in the vapor generation tank 21 so that the inert gas flows in a direction parallel to the liquid surface of the monomer. This prevents the inert gas flowing into the headspace 26 from being sprayed onto the liquid surface of the organic compound, thereby preventing the liquid surface from rippling and generating bubbles or mist. As a result, the monomer concentration in the gas supplied to the downstream gas junction 22 and the plasma chamber 5 from becoming abnormally high, and a monomer-containing gas containing a stable concentration of monomer gas can be supplied to the plasma chamber 5. The vapor generating tank 21 includes a temperature adjusting device 28 for adjusting the temperature of the liquid monomer.

[0026] Hereinafter, in this specification, the flow rate of the monomer-containing gas and the flow rate of the inert gas are represented by Q1 and Q2, respectively. Q1 and Q2 are expressed as the volume of gas flowing per unit time. The flow rate Q1 of the monomer-containing gas may be set appropriately depending on the type of monomer, the volume of the plasma vessel 5, and the like. For example, Q1 may be set to 0.1 to 100, 0.1 to 50, 0.1 to 20, 0.1 to 10, or 0.1 to 3 L / min, and preferably 0.5 to 2.0 L / min. The flow rate Q2 of the inert gas may be set appropriately depending on the volume of the plasma vessel 5. For example, Q2 may be set to 1 to 100, 1 to 50, 1 to 20, or 1 to 15 L / min, and preferably 5 to 12 L / min.

[0027] The gas supply unit 8 is equipped with a gas junction 22 where the inert gas and the monomer gas join and mix before being supplied into the plasma vessel 5. A flow rate limiting valve (not shown) is also provided, which can adjust the flow rates Q1 and Q2 of the monomer-containing gas and inert gas flowing into the gas junction, thereby adjusting the ratio of the monomer-containing gas to the inert gas. Flow meters 34a and 34b are also provided, which can measure the flow rates Q1 and Q2 of the monomer-containing gas and inert gas. The monomer gas and inert gas mixed in the gas junction 22 are supplied into the plasma vessel 5 through the gas inlet 11. The flow rate of the gas supplied into the plasma vessel 5 is expressed as the sum of the flow rate Q1 of the monomer-containing gas and the flow rate Q2 of the inert gas. The gas supplied into the plasma vessel 5 passes through the interior of the rectifying cover 43, more specifically between the first electrode 1 and the plurality of second electrodes 2a to 2e so that the gas flows in the longitudinal direction of the electrodes, and then diffuses throughout the gas phase within the plasma vessel 5 and is discharged to the outside from the gas exhaust section 12 via the ozone catalyst 42.

[0028] The concentration of the monomer gas in the plasma container 5 is not limited as long as the desired surface treatment is possible. The suitable concentration of the monomer gas varies depending on the type of monomer, but is preferably 200 to 30,000 ppm (volume), more preferably 200 to 10,000 ppm, more preferably 200 to 4,000 ppm, and even more preferably 200 to 1,000 ppm. When the monomer is acrylic acid, the preferred concentration of acrylic acid is 200 to 4,000 ppm, more preferably 300 to 900 ppm, and even more preferably 300 to 700 ppm. Furthermore, it is preferable that the concentration of the monomer gas is approximately uniform throughout the entire gas phase of the plasma container 5, particularly in the gas phase inside the rectifying cover 43.

[0029] The concentration of the monomer gas in the plasma vessel 5 can be evaluated by sampling the gas in the plasma vessel 5 and measuring the concentration using a known method. For example, the gas in the plasma vessel 5 can be collected using a syringe-type dilution vessel, diluted with air, and then subjected to a detector tube gas measuring instrument, GC, GC / MS, or the like. In a specific embodiment, the weight of the monomer in the vapor generation vessel 21 can be measured, and the concentration of the monomer gas can be calculated from the gas flow rate, the amount of weight loss of the monomer, and the like. Specific concentration measurement and evaluation methods are described in detail in the Examples. In one embodiment, an oxygen concentration measuring instrument 15 is installed in the plasma vessel 5 to monitor the oxygen concentration, which may interfere with plasma treatment.

[0030] The resin substrate 30 is not particularly limited, but preferably contains a resin that can be made hydrophilic by plasma treatment to generate hydrophilic functional groups such as hydroxyl groups, carbonyl groups, and carboxyl groups on the first surface of the resin substrate 30. Examples of the resin substrate 30 include a fluororesin substrate, polyphenylene sulfite, polyethylene, polybutylene terephthalate, polypropylene, and polyamide-66, with a fluororesin substrate being preferred. The resin substrate 30 is preferably a flat plate such as a film, sheet, or panel, but the surface of the resin substrate 30 may have irregularities. The resin substrate 30 may be made entirely of resin, or may be a substrate configured by coating a non-resin material with resin. Examples of non-resins include metal, glass, silicon, and known semiconductor thin films. In the surface treatment device 40 of this embodiment, the resin substrate is disposed between a first electrode and a plurality of second electrodes, and therefore the thickness of the resin substrate 30 is generally several tens of μm to several centimeters, and preferably 0.1 mm to 5 mm.

[0031] The fluororesin substrate is not particularly limited, and any known substrate can be used. Specific examples include substrates made of ethylene-tetrafluoroethylene copolymer (ETFE), polyvinyl fluoride resin (PVF), tetrafluoroethylene-perfluoroether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polytetrafluoroethylene (PTFE), vinylidene fluoride resin (PVDF), trifluorochloroethylene resin (PCTFE), ethylene-trifluorochloroethylene copolymer resin (ECTFE), etc. The fluororesin substrate may also contain additives such as pigments, fillers, and lubricants.

[0032] [Second embodiment: second surface treatment device] Unless otherwise specified, the components of the second surface treatment device of the present disclosure are the same as those described in the paragraph of the first surface treatment device of the present disclosure. Hereinafter, one embodiment of the present invention will be described with reference to the drawings (FIGS. 3A to 3C). The configurations shown in the drawings and the following description are merely examples, and the scope of the present invention is not limited to those shown in the drawings and the following description.

[0033] The second surface processing apparatus of the present disclosure differs from the first surface processing apparatus only in the configuration of the plasma processing unit 60, and the following mainly describes this difference. The plasma processing unit 60 includes a plurality of discharge electrode pairs 18a-18e arranged in a plurality of rows. While FIGS. 3A and 3B illustrate an example in which the first electrode 1 is provided, the first electrode 1 may be omitted. The discharge electrode pairs 18a-18e may be made of any material or have any structure that allows discharge to occur when a voltage is applied. The discharge electrode pairs 18a-18e may be included in the plasma ejection units 6a-6e, respectively. Each of the plasma ejection units 6a-6e includes a gas flow path member 31a-31e having a plasma ejection port 32a-32e, and a discharge electrode pair 18a-18e arranged in the flow path near the plasma ejection port.

[0034] The discharge electrode pairs 18a-18e may be made of any material or have any structure that allows grinding arc discharge or corona discharge to occur in each discharge electrode pair. Examples of the discharge electrode pairs 18a-18e include electrodes containing stainless steel, tungsten, copper, copper alloy, iron, and graphite. Because the discharge electrode pairs 18a-18e may be exposed to a monomer gas atmosphere, electrodes made of a material with low corrosiveness are advantageous, and a suitable example is tungsten electrodes. The discharge electrode pairs 18a-18e may be shaped, for example, as flat plates, needles, or rods, and may preferably be rods with a discharge portion at the tip bent in the shape of a check mark. The discharge electrode pairs 18a-18e include third electrodes 16a-16e and fourth electrodes 17a-17e. When the opposing third electrodes 16a-16e and fourth electrodes 17a-17e have different shapes (e.g., when the third electrode is a flat electrode and the fourth electrode is a needle-like electrode), the electric field strength becomes localized, which can cause corona discharge. When the opposing third electrodes 16a-16e and fourth electrodes 17a-17e have the same shape, specifically, when they are rod-shaped or needle-shaped, grinding arc discharge or corona discharge can occur. Grinding arc discharge is a type of discharge generated by applying a voltage while flowing gas between a pair of opposing discharge electrodes, and the discharge position is moved by the gas flowing between the electrodes. As shown by the dotted lines in Figure 3C, the gas flow between the pair of discharge electrodes generates a plasma flow directly below the pair of discharge electrodes. When the third electrodes 16a-16e and fourth electrodes 17a-17e are rod-shaped, for example, their diameter is 0.2-0.5 mm and the electrode spacing is 0.5-3 cm. In the embodiment of FIGS. 3A and 3B, the number of discharge electrode pairs is 30 and arranged in multiple rows. However, the number of discharge electrode pairs may be 29 or less, or 31 or more. Furthermore, the number of discharge electrode pairs 18a-18e may be determined appropriately depending on the size of the first surface of the resin base 30, the spacing between each discharge electrode pair, the output of the power supply device 7, and the like. The discharge electrode pairs may be arranged in a row. When the discharge electrode pairs are arranged in a row, the base support unit 9 preferably has a function of moving the resin base 30 so that the plasma irradiation treatment can be performed on the resin base 30. For example, the resin base 30 may be moved after a certain plasma irradiation treatment time has elapsed, or the resin base 30 may be moved at a low speed while the plasma irradiation treatment is performed. The flat first electrode 1 is as described in the "first surface treatment device" and is advantageously grounded. When the second surface treatment device of the present disclosure includes the first electrode 1, it can be advantageous for performing a uniform surface treatment since it can prevent unnecessary charge accumulation on the resin substrate 30.

[0035] Each of the plasma ejection parts 6a-6e is arranged so that the plasma ejection ports 32a-32e face the first surface of the resin base 30. As a result, the plurality of discharge electrode pairs 18a-18e are arranged so as to face the first surface of the resin base 30. The distance between the plasma ejection ports 32a-32e and the first surface of the resin base 30 is not particularly limited as long as plasma irradiation treatment is possible, but is generally several mm to several cm, specifically 5 mm to 3.0 cm, etc. For example, in surface treatment device 40 shown in FIG. 3A, gas flow path member 31c is a common member for six plasma ejection parts 6c. Gas inlet 11A is provided at one end of gas flow path member 31c. Gas flow path member 31c branches out so that gas supplied from gas inlet 11A is ejected from plasma ejection ports 32c of each plasma ejection part 6c. Discharge electrode pairs 18c are provided near each plasma ejection port 32c. Gas flow path member 31c is positioned so that these plasma ejection ports 32c face the first surface of resin base 30, thereby arranging discharge electrode pairs 18a-18e in a row. 3B includes a total of five gas flow path members and plasma ejection portions similar to the gas flow path member 31c and plasma ejection portion 6c (gas flow path members 31a-31e and plasma ejection portions 6a-6e). The five gas flow path members 31a-31e are arranged in parallel. Therefore, in the surface processing device 40 shown in FIGS. 3A and 3B, 30 plasma ejection portions 6a-6e and discharge electrode pairs 18a-18e are arranged in multiple rows. By arranging the gas flow path members 31a-31e in parallel, spaces through which gas can flow can be formed between the gas flow path members 31a-31e. This allows the gas ejected from the plasma ejection ports 32a-32e toward the resin base 30 to be exhausted through gaps between the gas flow path members, which is advantageous in that it is possible to suppress variations in the monomer concentration in the spaces between the plasma ejection ports 32a-32e and the resin base 30. In addition, the gas flow path members 31a-31e are supported by the plasma ejection port supports 19a-19e. This is advantageous in that it forms spaces above the gas flow path members 31a-31e through which gas can flow. In the second surface treatment device of the present disclosure, the plasma torch 4 includes a plurality of discharge electrode pairs 18a-18e, and further includes a rectifying cover 43. In the second surface treatment device of the present disclosure, the rectifying cover 43 is provided so that the gas ejected from the plasma ejection ports 32a-32e toward the resin substrate 30 is diffused throughout the gas phase of the plasma vessel 5 after passing through gaps between the gas flow path members. By virtue of the above-described configuration, the second surface treatment device of the present disclosure can perform a uniform surface treatment even when the resin base 30 has a large area.

[0036] In the second surface treatment apparatus of the present disclosure, the gas flowing into the flow path from gas inlet 11A may be an inert gas or a mixed gas of an inert gas and a monomer gas. When an inert gas is flowing into the flow path from gas inlet 11A, a separate gas inlet (not shown) may be provided to supply a monomer-containing gas into the flow path of rectifying cover 43. In this case, gas inlet 11A and flow rectifying cover 43 may be positioned so that the monomer-containing gas flows in the direction of extension of gas flow path members 31a-31e. This allows the monomer gas to be supplied to the space between plasma ejection ports 32a-32e and resin substrate 30, and further prevents variations in the monomer concentration. The flow rates of the monomer gas and the inert gas can be adjusted as appropriate. A high gas flow rate is advantageous in that the heat generated by the discharge is cooled by the gas. However, if the flow rate is too high, the time the gas is exposed to the discharge unit 33 is shortened, which can be disadvantageous in that the density of the generated plasma decreases. The preferred range of the flow rates of the monomer gas and the inert gas varies depending on the monomer gas concentration, the volume of the plasma vessel 5, and / or the voltage application conditions, but is preferably set so that the flow rate of the gas flowing from the gas inlet 11A into the gas flow path is 30 to 50 L / min.

[0037] [Third embodiment: surface treatment method] A third embodiment of the present disclosure is a surface treatment method (hereinafter also referred to as the "surface treatment method of the present disclosure") that includes a surface treatment step of plasma irradiation treatment of the surface of a resin substrate using any one of the surface treatment devices of the first or second embodiment of the present disclosure. In this specification, plasma treatment means irradiating the surface of a resin substrate with plasma. 1, a method for plasma irradiation treatment of the surface of a resin substrate 30 is exemplified. A gas containing an inert gas is supplied from a gas supply unit 8 to a plasma treatment unit 50 to cause the gas to flow, and an AC voltage is applied to the second electrodes 2a to 2e to generate a dielectric barrier discharge. In this state, plasma is irradiated onto the surface (first surface) of the resin substrate 30 to form radicals on the surface of the resin substrate 30, thereby making the surface of the resin substrate 30 hydrophilic.

[0038] In the surface treatment method of the present disclosure, when electrons contained in the plasma collide with the surface of a resin substrate, radicals (atoms or molecules having unpaired electrons) are generated on the surface of the resin substrate, thereby making the surface of the plasma-treated resin substrate hydrophilic. When the resin substrate is a fluororesin, for example, the C—F bonds of the fluororesin substrate are broken to generate radicals, as shown in formula (1). In formula (1), R is a fluororesin main chain containing carbon atoms, hydrogen atoms, oxygen atoms, and fluorine atoms. Formula (1): RF→R +F

[0039] The plasma used in this embodiment is preferably atmospheric pressure plasma obtained by gas discharge under atmospheric pressure. More preferably, it is non-thermal equilibrium plasma obtained by gas discharge under conditions that suppress Joule heating. In atmospheric pressure plasma, a strong electric field causes ionization of inert gases or ionization of organic compounds, resulting in the presence of electrons and ions. The surface treatment method of the present disclosure can be advantageously carried out at a temperature near room temperature (25°C) and at a pressure near atmospheric pressure. However, the gas in the plasma vessel 5 may be heated or cooled depending on the type of monomer used. In this specification, atmospheric pressure refers to normal pressure. Normal pressure does not strictly mean 1 atmosphere (1013 hPa) but refers to a pressure near 1 atmosphere. In this embodiment, a pressure of, for example, 500 to 2000 hPa may be used. Pressurization is advantageous in that it can prevent unintended gases (e.g., oxygen in the air) from entering the plasma vessel.

[0040] [Fourth embodiment: Method for manufacturing surface-coated resin substrate] A fourth embodiment of the present disclosure is a method for producing a surface-coated resin substrate, including a surface treatment step of plasma-irradiating the surface of the resin substrate using any one of the surface treatment devices according to the first or second embodiment of the present disclosure. While the third embodiment illustrates a surface treatment method in which the surface of the resin substrate is subjected to plasma irradiation to hydrophilize the surface, the plasma irradiation may be performed in an atmosphere in which a monomer gas and an inert gas supplied from a gas supply unit 8 are circulated. In this case, when the monomer reacts with radicals on the surface (first surface) of the resin substrate 30, a graft polymerization reaction (gas-phase polymerization reaction) proceeds, and a resin layer is formed as a surface coating layer chemically bonded to the resin substrate, thereby producing a surface-coated resin substrate.

[0041] When the resin substrate is a fluororesin substrate and the monomer is a (meth)acrylic monomer, the (meth)acrylic monomer reacts with radicals on the surface of the fluororesin substrate, causing a graft polymerization reaction (gas-phase polymerization reaction) to proceed, resulting in the formation of a (meth)acrylic resin layer, which is a surface coating layer chemically bonded to the fluororesin substrate. For example, when acrylic acid reacts with a radical (initial radical) on the surface of the fluororesin substrate, the radical adds to the double bond of the acrylic acid, as shown in formula (2), generating a growing radical. This growing radical repeatedly adds to the double bond of the acrylic acid, causing a polymerization reaction (e.g., formula (3)), resulting in the formation of a (meth)acrylic resin layer. Formula (2): R·+CH2=CHCOOH → R-CH2-C·HCOOH Formula (3): R·+n(CH2=CHCOOH) → R-(CH2-CHCOOH) n In this way, a surface coating layer can be formed on the surface of the fluororesin substrate. The (meth)acrylic resin layer is hydrophilic and has high chemical stability, which is advantageous in that the adhesiveness-improving effect of the plasma treatment is excellent in durability.

[0042] The voltage application conditions in the third and fourth embodiments of the present disclosure vary slightly depending on the type of inert gas used, the configuration of the electrodes, etc. Specifically, it is preferable to apply to the plurality of second electrodes included in the first surface treatment device of the present disclosure or the discharge electrode pair included in the second surface treatment device of the present disclosure a voltage having an applied voltage frequency of 1 kHz to 100 kHz, a discharge voltage of 1 kV to 20 kV, a pulse modulation frequency of 10 Hz to 200 Hz, and a pulse duty of 10% to 90%. If the frequency is lower than 1 kHz, the plasma temperature will increase, which may cause thermal damage to the material being treated. On the other hand, if it is higher than 100 kHz, the plasma density will decrease, which may result in a longer treatment time. If the discharge voltage is lower than 1 kV, the discharge may become unstable and stop. On the other hand, if it is higher than 20 kV, the discharge will become strong, causing an arc discharge, which will result in high-temperature plasma and may cause thermal damage to the material being treated. If the pulse modulation frequency is lower than 10 Hz, the discharge may become intermittent, which may result in a longer treatment time. On the other hand, if it is higher than 200 Hz, the plasma flare blowing out from the plasma flow irradiation section will become shorter, which may result in a smaller treatment area. Furthermore, if the pulse duty is lower than 10%, the plasma density may decrease. On the other hand, if it is higher than 90%, the plasma temperature may increase. More preferable frequency, discharge voltage, pulse modulation frequency and pulse duty are 10 kHz to 50 kHz, 5 kV to 15 kV, 30 Hz to 100 Hz and 30% to 70%, respectively. Furthermore, the voltage application time in the third and fourth embodiments of the present disclosure can be appropriately determined depending on the configurations of the first electrode 1, the second electrodes 2a-2e, the discharge electrode pairs 18a-18e, and the power supply 7, the desired thickness of the surface coating layer, and the like. Specifically, the voltage application time can be 10 to 100 seconds, and preferably 15 to 60 seconds. While it may be possible to form a homogeneous surface coating layer by extending the voltage application time, extending the voltage application time too long is not preferable because it increases the amount of homopolymerized monomers and may deteriorate the adhesion of the surface coating resin substrate.

[0043] The method for producing a surface-coated resin base according to the present disclosure may further include a step of forming a metal film or an insulating film on the (meth)acrylic resin layer by plating. Examples of materials for the metal film include copper, silver, and gold. Examples of methods for forming the metal film include gas phase methods such as vapor deposition and sputtering, and liquid phase methods such as plating. When a conductive resin is used for the resin base, electrolytic plating can be used as the plating method. Electroless plating can also be used. Examples of materials for the insulating film include polyimide. Examples of methods for forming the insulating film include heat treatment imidization.

[0044] [Fifth embodiment: surface-coated fluororesin substrate] A fifth embodiment of the present disclosure is a surface-coated fluororesin substrate comprising a fluororesin substrate and a (meth)acrylic resin layer provided on the fluororesin substrate, the (meth)acrylic resin layer being chemically bonded to the fluororesin substrate. In the fourth embodiment of the present disclosure, a method for producing a surface-coated resin substrate in which a surface coating layer is formed on the surface of a resin substrate was exemplified, but a surface-coated fluororesin substrate can also be produced when the resin substrate is a fluororesin substrate and the monomer is a (meth)acrylic monomer.

[0045] The surface-coated fluororesin substrate of the present disclosure has an extremely good surface condition and adhesiveness, and is homogeneous. In this specification, "homogeneous" means that there is little variation in the peel strength (adhesion strength) of the first surface of the surface-coated fluororesin substrate. The peel strength of the surface-coated fluororesin substrate can be evaluated by known methods. For example, it can be evaluated by JIS K6854 "Adhesives - Peel Adhesion Strength Test Method." Specific examples of evaluation methods are described in detail in the Examples. The thickness of the (meth)acrylic resin layer is not particularly limited, but is preferably 10 μm or less from the viewpoint of suppressing the generation of homopolymers and overpolymerization, and more preferably 0.01 μm to 1 μm. Furthermore, because the surface-coated fluororesin substrate of the present disclosure has the above-mentioned favorable properties, even if other thin films such as metal films or insulating films are formed on the resin layer, defects such as cracks are unlikely to occur in the other thin films. Therefore, the surface-coated fluororesin substrate can be suitably used as a material for electronic components such as flexible image display devices and flexible wiring boards. Therefore, the present disclosure also provides a surface-coated fluororesin substrate having a metal film further formed on the resin layer by a plating method. [Example]

[0046] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited thereto. All tests were performed using the surface treatment device 40 shown in Figures 1, 2A, and 2B. Unless otherwise specified, all tests were performed under atmospheric pressure (approximately 1013 hPa) and room temperature (25°C).

[0047] Test 1: Measurement of monomer concentration When the monomer-containing gas was supplied to the interior of the surface treatment device 40, the temperature of the organic compound 23 in the vapor generation tank 21 was changed, and the monomer concentration in the interior of the surface treatment device 40 was measured. A heater 27 (aluminum block) (width 19 mm × length 280.5 mm × height 35 mm) was placed in the steam generation tank 21, and then 26.07 g of acrylic acid (CH = CHCOOH, Fujifilm Wako Pure Chemical Industries, Ltd., content 98.0%+) was added as the organic compound 23 (acrylic acid surface area 307.5 mm 2A liquid depth of 26 mm was placed in the steam generation tank 21. The internal temperature of the steam generation tank 21 was kept constant at 25°C, 30°C, 55°C, or 60°C. After the internal temperature of the steam generation tank 21 was allowed to reach a steady state, argon gas (99.99%) was supplied from the gas inlet 24 to the headspace 26 of the steam generation tank 21. Thereafter, while maintaining the internal temperature of the steam generation tank 21, the flow rate of the argon gas supplied to the steam generation tank 21 was adjusted to 2 L / min. The acrylic acid-containing gas that had passed through the steam generation tank 21, i.e., the monomer-containing gas, and argon gas as an inert gas at a flow rate of 11 L / min were joined and mixed at the gas junction 22 to obtain a mixed gas. The mixed gas was supplied to the surface treatment device 40 through the gas inlet 11 at a flow rate of 13 L / min. By supplying the mixed gas, the air in the surface treatment device 40 was replaced with the mixed gas, thereby removing the air from the surface treatment device 40.

[0048] After removing the air from inside surface treatment device 40 with the mixed gas, the acrylic acid concentration was measured at spots (1) to (4) shown in FIG. 2B while continuing to supply the mixed gas. FIG. 2B is a side view showing the relationship between the plasma torch and the substrate in the surface treatment device of FIG. 1, and is an explanatory diagram of the measurement spots for the acrylic acid concentration. The first electrode, multiple second electrodes, and the like that constitute surface treatment device 40 of FIG. 1 will be explained in the description of Test 2 below. The acrylic acid concentration was measured by collecting the mixed gas from spots (1) to (4) using a syringe-type dilution container, diluting it 100 times with air, and then using a detector tube (Acetic Acid 81, manufactured by Gastec Corporation). Acrylic acid (CH2=CHCOOH) is an organic compound that shares a functional group (carboxyl group) with acetic acid (CH3-COOH), so it is possible to measure the acrylic acid concentration using a detector tube designed for acetic acid measurement. However, it has been found that the concentration measured by the detector tube is approximately 2 to 2.5 times the net acrylic acid concentration. For this reason, in Test 1, the results of the detector tube measurement were used to evaluate the acrylic acid concentration variation within the surface treatment device 40. The measurement results of the acrylic acid concentration using the detector tube are shown in Fig. 4. The mixed gas was sampled under the conditions that no AC voltage was applied to the first electrode 1 and the second electrodes 2a to 2e and no dielectric barrier discharge was generated in the discharge unit 33.

[0049] The following can be seen from Figure 4. Acrylic acid is a volatile organic compound, and by passing argon gas through the head space 26 of the vapor generating tank 21, a monomer-containing gas containing acrylic acid could be obtained. Furthermore, the higher the acrylic acid temperature in the vapor generation tank 21, the higher the acrylic acid concentration in the surface treatment device 40. Specifically, when the acrylic acid temperature was 25°C, 30°C, 55°C, and 60°C, the acrylic acid concentrations measured by the detector tube were approximately 2000 ppm, approximately 4000 ppm, approximately 5000 to 6000 ppm, and approximately 6000 to 8000 ppm, respectively. This is thought to be because, although acrylic acid can evaporate even at room temperature of 25°C, the higher the acrylic acid temperature, the greater the amount of evaporation. Furthermore, the higher the acrylic acid temperature, the greater the variation in acrylic acid concentration from spot to spot.

[0050] Test 2: Surface-coated fluororesin substrate manufacturing test The acrylic acid temperatures in the steam generation tank were set to 60°C, 55°C, and 30°C, and surface-coated fluororesin substrates of Examples 1 to 3 were produced using surface treatment device 40 equipped with first electrode 1 and five second electrodes 2a to 2e shown in FIGS. 1, 2A, and 2B. The first electrode 1 was a stainless steel electrode measuring 110 mm wide x 450 mm long x 10 mm high. The five second electrodes 2a to 2e were stainless steel electrodes measuring 4.5 mm wide x 250 mm long x 10 mm high. The spacing between each second electrode was 9.0 mm. Two second electrode support members 3a to 3e were joined to the upper sides of each of the second electrodes 2a to 2e, resulting in a plasma torch 4 equipped with a total of 10 second electrode support members. Each of the second electrode support members 3a to 3e was a stainless steel cylinder measuring 4.5 mm in diameter x 10 mm high. A container having a U-shaped structure with a height of 5 mm (all corners were right angles) was used as the rectifying cover 43. The outer frame of the rectifying cover 43 measured 110 mm wide x 250 mm long x 47 mm high, and the size of the space was 86 mm wide x 250 mm long x 42 mm high. The surface of the first electrode 1 facing the second electrodes 2a to 2e was covered with a dielectric 13a, and the back surface was covered with a dielectric 13b. The dielectrics 13a and 13b covering the first electrode 1 were made of PTFE measuring 110 mm wide x 450 mm long x 10 mm high. In the example, the substrate support 9 was a belt conveyor device 10, and a fluororesin film (Teflon (registered trademark) manufactured by DuPont: PFA: 210 mm x 80 mm x 0.25 mm) was placed on it as the sample 30. The material of the belt conveyor device 10 was polyvinyl chloride resin, and the height was 1.5 mm. The distance between the fluororesin film and the surfaces of the second electrodes 2a to 2e facing the fluororesin film was adjusted to be approximately 3 mm. In addition, the first electrode 1 was connected to the earth, and the second electrodes 2a to 2e were connected to the output terminals of a high-frequency high-voltage generator (power supply 7).

[0051] As in Test 1, a monomer-containing gas containing acrylic acid, which is organic compound 23, was supplied from vapor generation tank 21 to gas junction 22. The monomer-containing gas was merged with argon gas, which is an inert gas, at gas junction 22 to form a mixed gas, which was supplied into surface treatment device 40 through gas inlet 11. The gas flow rate Q1 (L / min) of the monomer-containing gas, the gas flow rate Q2 (L / min) of the inert gas, and the temperature of acrylic acid in vapor generation tank 21 in Examples 1 to 3 are shown in Table 1.

[0052] [Table 1]

[0053] While the mixed gas was flowing into the surface treatment device 40 at a flow rate of 13 L / min, an AC voltage (8.4 kV, frequency 20-25 kHz, discharge output 100 W) was applied to the second electrodes 2a-2e, causing a dielectric barrier discharge in the presence of the mixed gas and generating atmospheric pressure plasma. The dielectric barrier discharge caused blue to blue-purple light to be emitted between the second electrodes 2a-2e through which the mixed gas was flowing and the fluororesin film (discharge section 33). Plasma was generated for 15 seconds to treat the fluororesin film. As a result, the acrylic acid contained in the mixed gas was graft polymerized on the fluororesin film, resulting in a surface-coated fluororesin substrate in which the treated surface was coated with a polyacrylic acid resin layer.

[0054] In Examples 1 to 3, the weight of acrylic acid in the vapor generation tank 21 was measured before and after each test, and the amount of acrylic acid evaporated during the test was calculated. The concentration (ppm) of acrylic acid in the surface treatment device 40 during the test was calculated from conditions such as the amount of acrylic acid evaporated during the test, the gas flow rate, the temperature inside the device, and the molecular weight of acrylic acid. The formula for calculating the acrylic acid concentration is shown in formula (4).

[0055] Formula (4):

number

[0056] Test 3 Peel test A 90° peel test was carried out to evaluate the adhesive performance of the surface-coated fluororesin substrates of Examples 1 to 3 obtained in Test 2. The 90° peel test was carried out in accordance with JIS K6854-1 "Adhesives -- Test method for peel adhesion strength -- Part 1: 90° peel." The peel test method is shown in Figures 5(a) and 5(b). The 90° peel test was performed using a peel tester (digital force gauge, ZTA-100N, Imada Co., Ltd.) shown in Figure 5(a). The surface-coated fluororesin substrates of Examples 1 to 3 were washed with pure water, dried, and then cut into five test pieces measuring 50 mm in length and 35 mm in width as shown in Figure 5(b). The height of the test pieces was approximately 0.25 mm. The treated surface of the test piece was attached to a stainless steel plate 37 using double-sided tape 36 (KPS-25, peel strength 3.2 N / mm or more, special acrylic double-sided tape, 3M Japan Co., Ltd.), and then divided into two test pieces. A load of 10 kg was applied to each piece and the pieces were left to stand for 24 hours. The free end of the test piece was then clamped with the gripper jig 35 of the peel tester, and the stainless steel plate 37 was fixed to a base 38 with a jig 39, allowing it to slide left and right, so that the pulling angle of the test piece was always 90°. The test piece was pulled upward with the gripper jig 35 at a peel rate of 100 mm / min, and the peel strength (adhesion strength) (N / mm) when the test piece peeled was measured. Five test pieces were subjected to a peel test for each Example. The peel force curve obtained by the peel test is shown in Figure 6, and the average peel strength (N / mm) is shown in Table 1. Figures 6(a), 6(b), and 6(c) show the measurement results when the acrylic acid temperature was 60°C, 50°C, and 30°C, respectively. The vertical axis of Figure 6 represents peel strength (N / mm), and the horizontal axis represents peel length (mm). The thick peel strength curve in Figure 6 is the average of the peel strength curves of five test pieces, and the thin peel strength curves above and below it are peel strength curves obtained by adding the standard deviation to the average value. Unless otherwise specified in the figure, the average peel strength is the average value of the peel strength between peel lengths of 10 mm and 28 mm.

[0057] The results are shown in Table 1 and Figure 6. It is known that untreated fluororesin films have low adhesiveness. The peel strength of untreated PFA measured in a 90° peel test was 0.024 N / mm or less. The surface-coated fluororesin substrates of Examples 1 to 3 achieved average peel strengths of 1.09 to 1.25 N / mm, which were greater than those of untreated fluororesin films. In the surface-coated fluororesin substrates of Examples 1 to 3, the average peel strength of the produced surface-coated fluororesin substrates decreased as the acrylic acid temperature in the steam generation tank 21 increased and the acrylic acid concentration in the surface treatment device 40 increased. In the surface-coated fluororesin substrates of Examples 1 and 2, striped white discoloration was visible on the treated surface, and the peel strength was particularly low in the areas with striped discoloration. Generally, if the concentration of acrylic acid as a monomer is too high, the degree of polymerization of polyacrylic acid on the fluororesin substrate increases, which can lead to overpolymerization, or a homopolymer of the monomer can adhere to the surface of the fluororesin substrate. Under conditions where the acrylic acid temperature is high, the acrylic acid concentration increases, and it is thought that the peel strength of the fluororesin substrate decreases due to the occurrence of such overpolymerization or homopolymerization. Furthermore, the higher the acrylic acid temperature in the steam generation tank 21 and the higher the acrylic acid concentration in the surface treatment device 40, the greater the variation in the peel force curve. In other words, it was found that the variation in the peel force curve was smaller in the peel test using the surface-coated resin substrate of Example 3, which was produced under test conditions with a low acrylic acid temperature. The reason for this result is thought to be that, with reference to the results of Test 1, the higher the acrylic acid temperature in the steam generation tank 21, the greater the variation in the acrylic acid concentration in the surface treatment device 40.

[0058] Based on the results of Tests 1 to 3, it was decided to standardize the temperature of acrylic acid in the steam generation tank 21 to 30°C in the following tests.

[0059] Test 4: Surface-coated fluororesin substrate manufacturing test (gas flow rate ratio study) Surface-coated fluororesin substrates of Examples 4 and 5 were produced in the same manner as in Example 3 of Test 2, except for the gas flow rates Q1 and Q2. The peel strength of the produced surface-coated fluororesin substrates was evaluated using the method described in Test 3. The test conditions and the average peel strengths of the surface-coated fluororesin substrates of Examples 4 and 5 are shown in Table 2. Also, peel force curves are shown in Figure 7. Figures 7(a), 7(b), and 7(c) show the measurement results when the flow rate Q1 of the monomer-containing gas and the flow rate Q2 of the inert gas were Q1 = 2 L / min and Q2 = 11 L / min, Q1 = 1 L / min and Q2 = 12 L / min, and Q1 = 0.5 L / min and Q2 = 12.5 L / min, respectively.

[0060] [Table 2]

[0061] In Test 2, Example 3 and Test 4 (Examples 4 and 5) were the same tests except for the gas flow rate ratio of gas flow rates Q1 and Q2. The acrylic acid concentration in the surface treatment device was 1763 ppm in Example 3, 800 ppm in Example 4, and 308 ppm in Example 5. The average peel strength of the surface-coated fluororesin substrate was 1.25 N / mm in Example 3, 1.96 N / mm in Example 4, and 2.18 N / mm in Example 5. It was found that the evaporation amount of the acrylic acid in the surface treatment device can be adjusted by the acrylic acid temperature in the steam generation tank (essentially the results of Tests 1 and 2), and that the acrylic acid concentration in the surface treatment device can also be adjusted by changing the gas flow rate ratio of the monomer gas and the inert gas. Within the range of Tests 2 and 4 (acrylic acid concentration range of 308 to 3641 ppm), the lower the acrylic acid concentration in surface treatment device 40, the higher the average peel strength of the surface-coated fluororesin substrate produced, and the smaller the standard deviation of the peel force curve tended to be. From this, it was considered that, in the surface treatment method for a fluororesin substrate according to the present disclosure, a lower acrylic acid concentration is preferable for producing a surface-coated fluororesin substrate having a uniform and high peel strength, as long as it is within the concentration range in which the desired graft polymerization reaction can occur on the resin substrate surface.

[0062] Test 5: Surface-coated fluororesin substrate manufacturing test (treatment time study) Surface-coated fluororesin substrates of Examples 6 and 7 were produced in the same manner as in Test 4, except that the gas flow rates Q1 and Q2 were set to 0.8 L / min and 9.2 L / min, respectively, the mixed gas was flowed into the surface treatment device 40 at a flow rate of 10 L / min, and the treatment time for the fluororesin substrate was set to 30 seconds (Example 6) or 60 seconds (Example 7). The peel strength of the produced surface-coated fluororesin substrates was evaluated using the method described in Test 3. The test conditions and the average peel strengths of the surface-coated fluororesin substrates of Examples 6 and 7 are shown in Table 2. The peel force curves are also shown in Figure 8. Figures 8(a) and 7(b) show the measurement results when the plasma treatment times were 30 and 60 seconds, respectively.

[0063] Test 5 (Examples 6 and 7) was conducted under the same conditions except for the treatment time. The average peel strength of the surface-coated fluororesin substrate was 2.11 N / mm in Example 6 and 2.05 N / mm in Example 7. No significant difference in the average peel strength was observed even when the treatment time was changed. Therefore, it was considered that, under the conditions of this test, the average peel strength would not change significantly even if the treatment time was extended to 30 seconds or more. Furthermore, when the acrylic acid concentration and average peel strength of Example 4, which was under conditions of different gas flow rates and gas flow rate ratios but similar acrylic acid concentration values in surface treatment device 40, were compared to Example 4, the average peel strength of Example 6 was about 8% higher, even though the acrylic acid concentration in surface treatment device 40 was about 6% higher. For this reason, it is possible that a surface-coated fluororesin substrate with higher peel strength can be obtained by extending the treatment time from 15 seconds to 30 seconds. From another perspective, comparing the peel force curves in Figure 8, the longer the treatment time, the smaller the standard deviation of the peel force curve. Therefore, it is thought that by extending the treatment time, it is possible to produce surface-coated fluororesin substrates with uniform peel strength.

[0064] Test 6: Surface-coated fluororesin substrate manufacturing test (study of applied AC voltage output) Surface-coated fluororesin substrates of Examples 8 and 9 were produced in the same manner as in Test 5, except that the treatment time for the fluororesin substrate was 15 seconds and the conditions for the AC voltage applied to the second electrodes 2a to 2e were changed. Specifically, in Example 8, an AC voltage of 10.0 kV, a frequency of 20-25 kHz, and a discharge output of 150 W was applied to the second electrodes 2a to 2e, and in Example 8, an AC voltage of 10.5 kV, a frequency of 20-25 kHz, and a discharge output of 200 W was applied to the second electrodes 2a to 2e. The peel strength of the produced surface-coated fluororesin substrates was evaluated using the method described in Test 3. The test conditions and the average peel strengths of the surface-coated fluororesin substrates of Examples 8 and 9 are shown in Table 2. The peel force curves are also shown in Figure 9. Figures 9(a) and 9(b) show the measurement results when the output voltages were 10 kV and 10.5 kV, respectively.

[0065] Test 6 (Examples 8 and 9) was conducted under the same conditions except that the AC voltages applied to the second electrodes 2a to 2e were different and the discharge outputs were different. As shown in Table 2, the average peel strengths of the surface-coated fluororesin substrates of Examples 8 and 9 were 2.17 N / mm and 2.16 N / mm, respectively, and no significant difference was observed. For reference, an AC voltage of 8.4 kV was applied in Tests 2, 4, and 5 (Examples 1 to 7), and the discharge output was 100 W. However, for example, the surface-coated fluororesin substrate of Example 4 (acrylic acid concentration 800 ppm) was produced under conditions where the acrylic acid concentration was about 15% higher than in Examples 8 and 9 (acrylic acid concentration 694 ppm in both), and accordingly the average peel strength was about 11% lower. Therefore, at least within the range examined in Tests 2 and 4 to 6 (Examples 1 to 9) (the range where the discharge output is 100 W or more), changing the discharge output had almost no effect on the average peel strength of the obtained surface-coated fluororesin substrate, and it was thought that the peel strength of the surface-coated fluororesin substrate was mainly affected by the acrylic acid concentration in the surface treatment device 40. From another perspective, the device and method of the present disclosure enable surface treatment while appropriately adjusting the discharge conditions as long as a steady dielectric barrier discharge is obtained in the discharge section. Depending on the method of applying the AC voltage, the device and method of the present disclosure may be advantageous in that it is possible to obtain atmospheric pressure non-thermal equilibrium plasma while suppressing Joule heating. [Explanation of symbols]

[0066] 1: First electrode 2a to 2e: Second electrode 3a to 3e: Second electrode support 4: Plasma torch 5: Plasma container 6a to 6e: Plasma ejection part 7: Power supply 8: Gas supply part 9: Substrate support 10: Belt conveyor device 11, 11A: Gas inlet 12: Gas exhaust part 13a, 13b: Dielectric 14: Sealing part 15: Oxygen concentration measuring device 16a to 16e: Third electrode 17a to 17e: Fourth electrode 18a to 18e: Discharge electrode pair 19a to 19e: Support part for discharge electrode pair (support part for plasma ejection part) 20: Gas cylinder 21: Vapor generation tank 22: Gas confluence part 23: Organic compound 24: Gas inlet 25: Gas outlet 26: Headspace 27: Heater 28: Temperature control device 29: Power supply unit for steam generation chamber 30: Sample (resin substrate) 31, 31a to 31e: Gas flow path member 32a to 32e: Plasma nozzle 33: Discharge unit 34a, 34b: Flow meter 35: Gripper jig 36: Double-sided tape 37: Stainless steel plate 38: Stainless steel base 39: Fixing jig for stainless steel plate 40: Surface treatment device 41: Cover plate 42: Ozone catalyst 43: Rectification cover 45: Plasma torch fixing member 50, 60: Plasma treatment unit

Claims

1. A surface treatment device for performing plasma irradiation treatment on a first surface of a resin substrate, comprising: a first electrode having a flat plate shape and disposed opposite to the second surface of the resin base; a plurality of second electrodes disposed opposite the first surface of the resin base; a plasma vessel containing the plurality of second electrodes; a power supply connected to at least one of the first electrode and the second electrode; a gas supply unit configured to supply a monomer gas and an inert gas into the plasma vessel; The second electrodes are arranged in parallel with one another at intervals, and the surfaces of the second electrodes facing the first surface have a substantially rectangular shape.

2. The surface treatment apparatus according to claim 1 , wherein the plurality of second electrodes are provided so that a space through which the monomer gas and the inert gas can flow exists between two adjacent second electrodes.

3. the monomer gas is a (meth)acrylic monomer gas, 2. The surface treatment apparatus according to claim 1, wherein the inert gas is at least one gas selected from the group consisting of argon gas, nitrogen gas, and helium gas.

4. The surface treatment apparatus according to claim 1 , wherein the gas supply unit supplies the monomer gas and the inert gas into the plasma vessel so that the concentration of the monomer gas in the plasma vessel is 200 ppm or more and 4000 ppm or less.

5. 2. The surface treatment device according to claim 1, wherein the resin base is a fluororesin base.

6. A surface treatment device for performing plasma irradiation treatment on a first surface of a resin substrate, comprising: a plurality of discharge electrode pairs arranged opposite to the first surface of the resin base; a plasma vessel containing the plurality of discharge electrode pairs; a power supply device connected to the plurality of discharge electrode pairs; a gas supply unit configured to supply a monomer gas and an inert gas into the plasma vessel; The surface treatment device in which the plurality of discharge electrode pairs are arranged in a plurality of rows.

7. 7. The surface treatment device according to claim 6, wherein the plurality of discharge electrode pairs arranged in the plurality of rows are arranged so that a space through which the monomer gas and the inert gas can flow exists between two adjacent rows of discharge electrode pairs arranged in the plurality of rows.

8. A surface treatment device for performing plasma irradiation treatment on a first surface of a resin substrate, comprising: a plurality of discharge electrode pairs arranged opposite to the first surface of the resin base; a plasma vessel containing the plurality of discharge electrode pairs; a power supply device connected to the discharge electrode pair; a gas supply unit configured to supply a monomer gas and an inert gas into the plasma vessel; The surface treatment device in which the plurality of discharge electrode pairs are arranged in a row.

9. 9. The surface treatment device according to claim 6, wherein plasma generated by applying a voltage to the plurality of discharge electrode pairs is ejected onto the first surface of the resin base by an inert gas supplied from the gas supply unit.

10. further comprising a base support portion that supports the resin base, 9. The surface treatment apparatus according to claim 1, wherein the substrate support portion is movable so as to enable plasma irradiation treatment at a desired location on the first surface of the resin substrate.

11. A surface treatment method comprising a surface treatment step of treating the surface of the resin substrate with plasma irradiation using the surface treatment device according to any one of claims 1 to 8.

12. A method for producing a surface-coated resin substrate, comprising a surface treatment step of treating the surface of the resin substrate with plasma irradiation using the surface treatment device according to any one of claims 1 to 8.

13. the resin base is a fluororesin base, the monomer gas is a (meth)acrylic monomer gas, The method for producing a surface-coated resin substrate according to claim 12, wherein the surface treatment step includes a step of forming a (meth)acrylic resin layer on the surface of the resin substrate by the plasma irradiation treatment.

14. 13. The method for producing a surface-coated resin substrate according to claim 12, wherein the surface treatment step includes a step of generating plasma by applying an AC voltage having a frequency of 1 kHz to 100 kHz and a voltage of 1 kV to 20 kV.

15. The method for producing a surface-coated resin base according to claim 13, further comprising the step of forming a metal film on the (meth)acrylic resin layer by plating.

16. 14. A surface-coated fluororesin substrate manufactured by the method for manufacturing a surface-coated resin substrate according to claim 13, comprising: a fluororesin substrate; and a (meth)acrylic resin layer provided on the fluororesin substrate, wherein the (meth)acrylic resin layer is chemically bonded to the fluororesin substrate.

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