Fluororesin modification method and modification device

Abstract

To provide an improved method and apparatus for modifying a fluororesin.SOLUTION: A method for modifying a fluororesin includes: a first step of irradiating a first fluid containing an organic compound containing at least any one of oxygen atoms and nitrogen atoms with ultraviolet light indicating intensity in a wavelength region of at least 205 nm or less, and bringing the first fluid irradiated with the ultraviolet light into contact with a fluororesin; and a second step of irradiating a second fluid containing gas or misty water with the ultraviolet light, and bringing the second fluid irradiated with the ultraviolet light into contact with the fluororesin. A modifying apparatus includes at least one fluid supply port for supplying a first fluid containing an organic compound containing at least one of oxygen atoms and nitrogen atoms, and a second fluid containing gas or misty water into a chamber, and a light source for irradiating the first fluid and second fluid in the chamber with ultraviolet light indicating intensity in a wavelength region of a wavelength of 205 nm or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for modifying a fluororesin. [Background technology]

[0002] Methods for modifying hydrophobic fluororesins to make them hydrophilic have been known.

[0003] Patent Document 1 describes a method in which a substrate 91 made of fluororesin is brought into contact with the surface of an ethanol aqueous solution 90, and a main surface 92 of the substrate 91 in contact with the ethanol aqueous solution 90 is irradiated with ultraviolet light from an ArF excimer laser to modify the main surface 92 to be hydrophilic (see Figure 10). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 6-279590 Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Document 1 discloses two methods for irradiating ultraviolet light onto main surface 92. As shown in Fig. 10, in the first method, a light source 95a is placed above a container 93 that stores an ethanol aqueous solution 90, and ultraviolet light L8 is irradiated onto main surface 92 from the back side of substrate 91, passing through substrate 91. In the second method, a light source 95b is placed below container 93, and ultraviolet light L9 is irradiated onto main surface 92 via container 93 and ethanol aqueous solution 90.

[0006] When the first method is adopted, only thin substrates can be processed because the ultraviolet light L8 passes through the substrate 91, and even for thin substrates, there are problems that the ultraviolet light L8 is absorbed by the substrate 91, reducing the amount of ultraviolet light L8 that reaches the main surface 92, and that the fluororesin that makes up the substrate 91 is altered by the ultraviolet light L8. When the second method is adopted, there is a problem that when the ultraviolet light L9 passes through the container 93 and the ethanol aqueous solution 90, the ultraviolet light L9 is absorbed by the ethanol aqueous solution 90 or scattered by the ethanol aqueous solution 90, significantly reducing the amount of ultraviolet light L9 that reaches the main surface 92.

[0007] In view of these problems, an object of the present invention is to provide an improved method and apparatus for modifying fluororesin. [Means for solving the problem]

[0008] The method for modifying a fluororesin of the present invention includes a first step of irradiating a first fluid containing an organic compound containing at least one of an oxygen atom and a nitrogen atom with ultraviolet light having an intensity in a wavelength range of at least 205 nm or less, and bringing the first fluid irradiated with the ultraviolet light into contact with a fluororesin; and a second step of irradiating a second fluid containing gas or atomized water with the ultraviolet light and bringing the second fluid irradiated with the ultraviolet light into contact with a fluororesin.

[0009] In the present invention, ultraviolet light having an intensity in a wavelength range of at least 205 nm or less is used to radicalize an organic compound containing at least one of an oxygen atom and a nitrogen atom in the first step, and to radicalize gaseous or atomized water in the second step.

[0010] The terms used in this specification are explained below. "Radical" refers to an atom or molecule with an unpaired electron. As will be explained in detail later, radicals have high reactivity with other molecules due to their unpaired electron. "Radicalization" refers to the generation of radicals from a radical source. "An organic compound containing at least one of an oxygen atom and a nitrogen atom" means that the molecular structure of the organic compound contains at least one oxygen atom or nitrogen atom.

[0011] The first fluid contains an organic compound containing at least one of an oxygen atom and a nitrogen atom. The organic compound exists in the first fluid in the form of a gas, liquid, or mist. In the first step, the organic compound containing at least one of an oxygen atom and a nitrogen atom is radicalized by the ultraviolet light. The radicals obtained from the organic compound containing at least one of an oxygen atom and a nitrogen atom hydrophilize the surface of the hydrophobic fluororesin. In the second step, water molecules (HO) contained in the second fluid are radicalized by the ultraviolet light to generate OH radicals and hydrogen radicals. The generated OH radicals and hydrogen radicals hydrophilize the surface layer of the fluororesin. The "surface layer" includes the surface of the object and the interior of the object near the surface.

[0012] In the present invention, ultraviolet light is used to radicalize the first fluid and the second fluid, and the generated radicals are used to hydrophilize the surface layer of the fluororesin. In Patent Document 1, ultraviolet light from an ArF excimer laser is irradiated onto the ethanol aqueous solution, but the purpose of irradiating ultraviolet light in Patent Document 1 is to radicalize the ethanol molecules in the ethanol aqueous solution, not the water molecules in the ethanol aqueous solution. In this respect, the present invention is significantly different from Patent Document 1.

[0013] The target of irradiation with the ultraviolet light in the second step is a second fluid containing gaseous or misty water. The expression "second fluid containing gaseous or misty water" refers to the second fluid containing gaseous HO (i.e., water vapor) or liquid HO, where the liquid is composed of particles that can float in the fluid. Because the attenuation of ultraviolet light passing through a gaseous or misty second fluid is less than the attenuation of ultraviolet light passing through water stored in a container, more ultraviolet light can be irradiated onto the fluororesin. This allows for more hydrophilicity than conventional methods.

[0014] Making a fluororesin surface hydrophilic refers to a process that increases the surface's affinity for water molecules. Replacing fluorine atoms on the surface of a fluororesin with polar functional groups that do not contain fluorine atoms increases the hydrophilicity of the fluororesin surface. As will be described in more detail later, modifying a fluororesin from hydrophobic to hydrophilic allows, for example, for it to be firmly bonded to other materials.

[0015] The second step may be performed after the first step, or the first and second steps may be performed in parallel. One method for performing the first and second steps in parallel involves irradiating a gaseous or misty mixed fluid, which is a mixture of a gaseous or misty first fluid and a gaseous or misty second fluid, with ultraviolet light. As will be described in detail later, when the mixed fluid is irradiated with ultraviolet light, organic compounds in the first fluid and water molecules in the second fluid are radicalized in parallel, hydrophilizing the surface layer of the fluororesin (i.e., the surface and the interior near the surface). Hydrophilizing not only the surface but also the interior near the surface improves bonding strength. Furthermore, performing multiple steps in parallel shortens the processing time and simplifies the equipment and system. When the second step is performed after the first step, the first fluid may contain an organic compound present as a liquid.

[0016] At least one of the first step and the second step may be performed by irradiating ultraviolet light toward the fluid in contact with the fluororesin. To irradiate ultraviolet light toward the fluid in contact with the fluororesin, for example, a light source emitting the ultraviolet light is brought close to the fluororesin, and the fluid is allowed to flow through the gap while irradiating the ultraviolet light from the light source toward the fluororesin. This allows the fluid near the surface of the fluororesin or inside the fluororesin to be targeted for radicalization, which is necessary for the modification treatment. As a result, many radicals can be brought into contact with the fluororesin.

[0017] The organic compound may contain at least one of a hydroxy group, a carbonyl group, and an ether bond, and since a functional group containing at least one of a hydroxy group, a carbonyl group, and an ether bond can be formed on the surface of the fluororesin, the surface of the fluororesin can be imparted with strong hydrophilicity.

[0018] The organic compound may include at least one selected from the group consisting of alcohols, ketones, aldehydes, carboxylic acids, and phenols.

[0019] The organic compound may include at least one selected from the group consisting of alcohols having 10 or less carbon atoms and ketones having 10 or less carbon atoms.

[0020] The organic compound may include at least one selected from the group consisting of alcohols having 2 to 4 carbon atoms and acetone. Alcohols having 2 to 4 carbon atoms and acetone are easy to obtain and economical. Alcohols having 2 to 4 carbon atoms are safe and easy to handle. Acetone has a high vapor pressure and is therefore likely to form a relatively high-concentration atmosphere.

[0021] The organic compound may contain at least one of an amino group, an imino group, or a cyano group.

[0022] The organic compound may include at least one selected from the group consisting of amines having 4 or less carbon atoms and nitriles having 4 or less carbon atoms. Amines having 4 or less carbon atoms and nitriles having 4 or less carbon atoms are easily available and economical.

[0023] The ultraviolet light may be generated by a xenon excimer lamp.

[0024] The reforming device of the present invention comprises: at least one fluid supply port for supplying into the chamber a first fluid containing an organic compound containing at least one of oxygen atoms and nitrogen atoms, and a second fluid containing gas or atomized water; a light source that irradiates ultraviolet light having an intensity in a wavelength range of 205 nm or less toward the first fluid and the second fluid in the chamber; The surface layer of the object to be treated is made hydrophilic by the first fluid irradiated with ultraviolet light and the second fluid irradiated with ultraviolet light.

[0025] The fluid supply port may be located, for example, on the wall or ceiling of the chamber. When there is only one fluid supply port, the fluid supply port is typically connected to both a supply source of the first fluid and a supply source of the second fluid. However, the supply source may be an integrated supply source that supplies both the first fluid and the second fluid. When there is only one fluid supply port and an integrated supply source is used, the fluid supply port is connected to the integrated supply source. When there are multiple fluid supply ports, at least one fluid supply port is connected to the supply source of the first fluid, and the remaining fluid supply ports are connected to the supply source of the second fluid. When the fluid supply port is connected to the supply source, a fluid supply path such as a pipe may be used between the fluid supply port and the supply source. [Effects of the Invention]

[0026] An improved method and apparatus for modifying fluororesin can be provided. [Brief explanation of the drawings]

[0027] [Figure 1] FIG. 1 is a diagram showing an embodiment of a fluororesin reforming system. [Figure 2A] FIG. 1 is a diagram illustrating a modification mechanism. [Figure 2B] FIG. 1 is a diagram illustrating a modification mechanism. [Figure 2C] FIG. 1 is a diagram illustrating a modification mechanism. [Figure 2D] FIG. 1 is a diagram illustrating a modification mechanism. [Figure 3A]FIG. 1 is a diagram illustrating a modification mechanism. [Figure 3B] FIG. 1 is a diagram illustrating a modification mechanism. [Figure 3C] FIG. 1 is a diagram illustrating a modification mechanism. [Figure 3D] FIG. 1 is a diagram illustrating a modification mechanism. [Figure 4] FIG. 10 is a diagram illustrating a first modified example of a fluid supply source. [Figure 5] FIG. 10 is a diagram illustrating a second modified example of the fluid supply source. [Figure 6] FIG. 10 is a diagram illustrating a first modified example of the reformer. [Figure 7] FIG. 10 is a diagram illustrating a second modified example of the reformer. [Figure 8A] The results of ATR-FTIR analysis of the surface layers of five samples. [Figure 8B] The results of ATR-FTIR analysis of the surface layers of five samples. [Figure 9] 1 is a graph showing the relationship between treatment time and contact angle. [Figure 10] FIG. 1 is a diagram illustrating a conventional method for modifying a fluororesin. DETAILED DESCRIPTION OF THE INVENTION

[0028] The embodiments will be described with reference to the drawings. Note that the drawings disclosed in this specification are merely schematic illustrations. That is, the dimensional ratios on the drawings do not necessarily match the actual dimensional ratios, and the dimensional ratios between the drawings do not necessarily match.

[0029] [Reforming system overview] An embodiment of a fluororesin reforming system and a fluororesin reforming method using the reforming system is shown below. Figure 1 shows the fluororesin reforming system. The reforming system 100 includes a reformer 20 and a fluid supply source 30 that supplies a fluid to the reformer 20.

[0030] The modifying device 20 includes a light source 3 and a fluid supply port 2 connected to a fluid supply source 30. The fluid supply source 30 supplies a first fluid F1 containing an organic compound containing at least one of oxygen atoms and nitrogen atoms, and a second fluid F2 containing water molecules to the chamber 5. The first fluid F1, the second fluid F2, and the fluid supply source 30 will be described in detail below.

[0031] The ultraviolet light L1 emitted by the light source 3 is vacuum ultraviolet light, more specifically, ultraviolet light that exhibits intensity at least in a wavelength range of 205 nm or less. As used herein, "ultraviolet light that exhibits intensity at least in a wavelength range of 205 nm or less" refers to light that has an emission band at 205 nm or less. Examples of such light include: (1) light that exhibits intensity over a broad wavelength range and exhibits an emission spectrum in which the peak emission wavelength at which the maximum intensity is 205 nm or less; (2) light that exhibits an emission spectrum in which multiple maximum intensities (multiple peaks) are present and any of the multiple peaks is within the wavelength range of 205 nm or less; and (3) light in which light at 205 nm or less accounts for at least 30% of the total integrated intensity in the emission spectrum.

[0032] The light source 3 may be, for example, a xenon excimer lamp. The peak emission wavelength of the xenon excimer lamp is 172 nm. The light emitted from the xenon excimer lamp is easily absorbed by the first fluid containing an organic compound containing at least one of oxygen atoms and nitrogen atoms, and the second fluid containing gaseous or atomized water. The organic compound containing at least one of oxygen atoms and nitrogen atoms and the water molecules each generate a large number of radicals.

[0033] [Processing object] In this embodiment, the workpiece 10 is an object entirely made of fluororesin. However, the workpiece 10 may be an object that is not entirely made of fluororesin. The workpiece 10 only needs to have an area where the fluororesin is exposed on at least a portion of its surface. The workpiece 10 may be a rigid plate-like substrate, a long flexible film, or a three-dimensional shape that is not plate-like.

[0034] Specific examples of the workpiece 10 include medical fluororesin and high-frequency printed wiring boards. Converting the surface of the fluororesin from hydrophobic to hydrophilic can increase the adhesive strength between the fluororesin and other materials. In the case of a printed wiring board, for example, the adhesive strength between the fluororesin base material and the copper plating film can be increased, which is expected to result in the copper plating being less likely to peel off.

[0035] [Generation of radicals from the first fluid by the reformer] The mechanism of radical generation in the first fluid by the reformer is explained below. First, the case of an organic compound containing oxygen atoms is explained. Ethanol (C2H5OH) is used as an example of an organic compound containing oxygen atoms. The chemical reaction formula for the process of generating radicals by irradiating ethanol molecules with ultraviolet light (hν) is shown below. [ka] [ka] [ka]

[0036] As shown in the above formulas (1) to (3), when an ethanol molecule is irradiated with ultraviolet light (hν), the energy of the ultraviolet light breaks the bonds between the atoms that make up the ethanol molecule, generating a radical consisting of carbon, hydrogen, and oxygen atoms (sometimes referred to as a "{CHO} radical") and a hydrogen radical (sometimes referred to as "H·"). {CHO} radicals include those in which C is radicalized and those in which O is radicalized. Depending on whether C or O is radicalized and the position of C, the three types of {CHO} radicals shown in the above formulas (1) to (3) are formed. However, it is not necessarily the case that each {CHO} radical is generated in equal proportions.

[0037] The three types of chemical reaction formulas shown in the above formulas (1) to (3) are for the {CHO} radical having one atom with an unpaired electron. By irradiating with ultraviolet light, {CHO} radicals having two or more atoms with unpaired electrons may also be generated.

[0038] Next, we will explain the case of organic compounds containing nitrogen atoms. As an example of an organic compound containing nitrogen atoms, we will take ethylamine (C2H5NH2). The chemical reaction formula for the process of generating radicals by irradiating ethylamine molecules with ultraviolet light (hν) is shown below. [ka] [ka] [ka]

[0039] As shown in the above formulas (4) to (6), when an ethylamine molecule is irradiated with ultraviolet light (hν), the energy of the ultraviolet light breaks the bonds between the atoms that make up the ethylamine molecule, generating radicals consisting of carbon, hydrogen, and nitrogen atoms (sometimes referred to as "{CHN} radicals") and hydrogen radicals. Radicals are atoms or molecules with unpaired electrons. {CHN} radicals include those in which C is radicalized and those in which N is radicalized. Depending on whether C or N is radicalized and the position of C, the three types of {CHN} radicals shown in the above formulas (4) to (6) are formed. It is not necessarily the case that each {CHN} radical is generated in equal proportions.

[0040] The three types of chemical reaction formulas shown in the above formulas (4) to (6) are for the {CHN} radical having one atom with an unpaired electron. By irradiating with ultraviolet light, {CHN} radicals having two or more atoms with unpaired electrons may also be generated.

[0041] [Modification mechanism] 2A to 2D, the mechanism of modifying the surface layer of the workpiece 10 by the first and second steps when the first fluid is an organic compound containing oxygen atoms will be described. 2A to 2D are diagrams illustrating the chemical structure of the surface or surface layer of the fluororesin of the workpiece 10 so that it can be understood.

[0042] Figure 2A shows the generation of radicals immediately before the fluororesin 11 (here, PTFE) is modified. As shown in Figure 2A, many fluorine atoms (F) bonded to carbon atoms (C) are present on the surface of the fluororesin 11 before surface modification. Near the surface of the fluororesin 11, {CHO} radicals generated from ethanol molecules and hydrogen radicals are present.

[0043] The fluorine atoms contained in the fluororesin 11 are bonded to carbon atoms. The bond energy between a carbon atom and a fluorine atom is as high as 485 kJ / mol, and therefore, a very large amount of energy is required to separate the fluorine atom from the carbon atom using heat or light.

[0044] Here, the electronegativity of a fluorine atom is 4.0, while that of a hydrogen atom is 2.2, which is significantly different. Therefore, hydrogen radicals can approach fluorine atoms due to electrostatic attraction, forming HF (hydrogen fluoride), thereby severing the bond between the fluorine atom and the carbon atom. The bond energy between hydrogen and fluorine atoms is even higher, at 568 kJ / mol, and HF leaves the fluororesin surface as a gas, so the HF production reaction proceeds irreversibly. At the sites where fluorine atoms have been extracted from the surface of the fluororesin 11, {CHO} radicals or hydrogen radicals bond.

[0045] FIG. 2B shows the state of the fluororesin 11 of FIG. 2A after surface modification with radicals from the first fluid. While FIG. 2B illustrates an example in which six fluorine atoms have been abstracted, with hydrogen radicals bonding to three of the atoms and {CHO} radicals bonding to the remaining three, fluorine atoms may remain on the surface. Furthermore, the number of hydrogen radical bonds and the number of {CHO} radical bonds do not have to be the same. For example, {CHO} radicals may bond to all of the sites from which fluorine atoms have been abstracted. Functional groups consisting of carbon atoms, hydrogen atoms, and oxygen atoms (hereinafter sometimes referred to as "{CHO} functional groups") are present on at least a portion of the surface of the fluororesin 11.

[0046] In FIG. 2B, the {CHO} functional group shown in (a) is formed by bonding the {CHO} radical obtained by the above formula (3) with the fluororesin 11. In FIG. 2B, the {CHO} functional group shown in (b) is formed by bonding the {CHO} radical obtained by the above formula (1) with the fluororesin 11. In FIG. 2B, the {CHO} functional group shown in (c) is formed by bonding the {CHO} radical obtained by the above formula (2) with the fluororesin 11.

[0047] The {CHO} functional group bonded to the fluororesin 11 has polarity. The {CHO} functional groups shown in (b) and (c) in FIG. 2B each have a hydroxyl group at their terminals and therefore exhibit strong hydrophilicity. The {CHO} functional group shown in (a) in FIG. 2B forms an ether bond with the fluororesin 11 and therefore exhibits a certain degree of hydrophilicity, although not as strong as a hydroxyl group. Note that for convenience of explanation, FIG. 2B shows an arrangement in which different functional groups, i.e., (a), (b), and (c), are adjacent to each other; however, in practice, the same functional groups may be adjacent to each other.

[0048] 2C shows how, in the second step, water molecules contained in the second fluid approach the surface of the fluororesin 11 and radicals are generated from the water molecules. As shown in FIG. 2C, when ultraviolet light is irradiated onto gaseous or atomized HO, the energy of the ultraviolet light breaks the bonds between HO in the HO, generating OH radicals (sometimes written as "OH·") and hydrogen radicals.

[0049] FIG. 2D shows the surface of the fluororesin after the second step. The surface of the fluororesin 11 has many hydrocarbon groups. OH radicals and hydrogen radicals generated from HO cleave C-H bonds contained in the hydrocarbon groups and extract hydrogen atoms from the hydrocarbon groups. Then, as shown in FIG. 2D, the OH radicals generated from HO bind to the locations where the hydrogen atoms were extracted. In FIG. 2D, the functional groups enclosed in dashed circles represent functional groups added in the second step. Thus, by performing the second step, OH groups are added to the hydrocarbon groups added in the first step, further enhancing the hydrophilicity of the fluororesin surface.

[0050] In addition, if the surface of fluororesin 11 is hydrophilized in the first step, water molecules can approach the surface of fluororesin 11 in the second step, as shown in FIG. 2C. Some water molecules can penetrate into the interior of fluororesin 11 near the surface. The water molecules that have penetrated into fluororesin 11 are decomposed by ultraviolet light L1 to generate hydrogen radicals and OH radicals.

[0051] Hydrogen radicals present inside the fluororesin 11 near its surface cleave C-F bonds present inside the fluororesin near its surface, abstracting fluorine. OH radicals bond to the sites from which fluorine has been abstracted, generating OH groups (see FIG. 2D). Note that hydrogen atoms may also be abstracted from the bound OH radicals, generating CO groups. CO groups are also oxygen-based functional groups that exhibit hydrophilicity. In this way, hydrophilicity progresses inside the fluororesin 11 near its surface. Note that, as shown in FIG. 2D, hydrogen radicals may also bond to the sites from which fluorine has been abstracted.

[0052] The above is the modification mechanism of the surface layer of the fluororesin by the first and second steps when the first fluid is an organic compound containing oxygen atoms. In principle, the second step proceeds after the first step. However, both the first and second steps proceed locally within the chamber over a short period of time. Therefore, in practice, the first and second steps may be performed in parallel. Details will be described later.

[0053] The reaction of generating radicals by irradiating a gas with ultraviolet light proceeds regardless of pressure, so the chamber where the reaction takes place does not necessarily need to be in a reduced pressure environment. However, in order to quickly replace the atmosphere in chamber 5 with a desired gas atmosphere, a vacuum pump may be connected to fluid outlet 6 so that the pressure inside chamber 5 can be reduced.

[0054] Next, with reference to Figures 3A to 3D, a modification mechanism of the surface layer of the workpiece 10 by the first step and the second step when the first fluid is an organic compound containing nitrogen atoms will be described. Figures 3A to 3D are diagrams illustrating the chemical structure of the fluororesin surface or surface layer of the workpiece 10 so that it can be understood. In the following, explanations of parts common to the modification mechanism when the first fluid is an organic compound containing oxygen atoms will be omitted as appropriate.

[0055] Figure 3A shows the generation of radicals just before the fluororesin 11 (here, PTFE) is modified. As shown in Figure 3A, ethylamine molecules absorb ultraviolet light to generate {CHN} radicals and hydrogen radicals. The hydrogen radicals cleave C-F bonds. The {CHN} radicals or hydrogen radicals bond to the sites where fluorine has been extracted from the surface of the fluororesin 11.

[0056] Figure 3B shows the state of the fluororesin 11 of Figure 3A after surface modification with radicals from the first fluid. Figure 3B illustrates an example in which six fluorine atoms have been abstracted, three of which have been bonded to hydrogen radicals, and the remaining three have been bonded to {CHN} radicals. Thus, functional groups consisting of carbon atoms, hydrogen atoms, and nitrogen atoms (hereinafter sometimes referred to as "{CHN} functional groups") are present on at least a portion of the surface of the fluororesin 11.

[0057] In Fig. 3B, the {CHN} functional group shown in (d) is formed by bonding the {CHN} radical obtained by the above formula (6) with the fluororesin 11. In Fig. 3B, the {CHN} functional group shown in (e) is formed by bonding the {CHN} radical obtained by the above formula (4) with the fluororesin 11. In Fig. 3B, the {CHN} functional group shown in (f) is formed by bonding the {CHN} radical obtained by the above formula (5) with the fluororesin 11.

[0058] 3C shows how radicals of the second fluid are generated in the second step. FIG. 3D shows how the surface layer of fluororesin 11 is modified with the generated second fluid. In FIG. 3D, the functional groups enclosed in dashed circles represent functional groups added in the second step. Even when the first fluid is an organic compound containing nitrogen atoms, performing the second step further enhances hydrophilicity of the surface of the fluororesin, just as in the case when the first fluid is an organic compound containing nitrogen atoms.

[0059] The above is the mechanism by which the fluororesin surface is modified in the first and second steps. In the sections "Radical generation of the first gas by the modifying device" and "Modification mechanism," ethanol (C2H5OH) was used as an example of an organic compound containing oxygen atoms, and ethylamine (C2H5NH2) was used as an example of an organic compound containing nitrogen atoms. However, these examples are not the only examples, and any fluid containing an organic compound containing at least one of oxygen and nitrogen atoms can be used for the hydrophilization in the first step.

[0060] However, it is preferable that the organic compound containing an oxygen atom contains at least one of a hydroxy group, a carbonyl group, and an ether bond. Since functional groups containing at least one of a hydroxy group, a carbonyl group, and an ether bond can be formed on the surface of the fluororesin, strong hydrophilicity can be imparted to the surface of the fluororesin. It is particularly preferable that the organic compound contains at least one selected from the group consisting of alcohols, ketones, aldehydes, carboxylic acids, and phenols. Furthermore, it is preferable that the organic compound contains at least one selected from the group consisting of alcohols having 10 or fewer carbon atoms and ketones having 10 or fewer carbon atoms. Among these, alcohols having 2 to 4 carbon atoms and acetone are easy to obtain and economical. In particular, alcohols having 2 to 4 carbon atoms are excellent in safety and ease of handling. Furthermore, acetone has a high vapor pressure and is therefore likely to form a relatively high-concentration atmosphere. It is also preferable that the organic compound containing a nitrogen atom contains at least one of an amino group, an imino group, or a cyano group. It is particularly preferable that the organic compound contains at least one selected from the group consisting of amines having 4 or fewer carbon atoms and nitriles having 4 or fewer carbon atoms. For example, methylamine, ethylamine, or acetonitrile is preferable.

[0061] [Fluid supply source] The fluid supply source 30 of this embodiment will be described with reference to Figure 1. The fluid supply source 30 has a container 55 containing an ethanol aqueous solution 51 and a carrier gas supply pipe 52 that supplies a carrier gas G1 to the ethanol aqueous solution 51 in the container 55. By feeding the carrier gas G1 into the ethanol aqueous solution 51, the ethanol aqueous solution 51 is volatilized by a bubbling method, and a first fluid F1 containing ethanol gas and a second fluid F2 containing water vapor can be simultaneously extracted and sent to the reformer 20 via the fluid supply pipe 56. In this case, the first step and the second step can be performed in parallel in the reformer 20.

[0062] The carrier gas G1 is an inert gas such as nitrogen gas. The fluid supply source 30 can send a mixed fluid obtained by mixing the carrier gas G1, a first fluid F1 containing ethanol gas, and a second fluid F2 containing water vapor to the reformer 20 via the fluid supply pipe 56. The second fluid F2 may contain atomized water in addition to water vapor.

[0063] The fluid supply source 30 can adjust the mixture ratio of ethanol gas, water vapor, and carrier gas G1 in the mixed fluid in the reformer 20 by adjusting the liquid volume, temperature, ethanol concentration, etc. in the ethanol aqueous solution 51. The supply amount of carrier gas G1 can be adjusted using a valve 54 while monitoring a flow meter 53. A supply pipe for supplying the ethanol aqueous solution 51 to the container 55 may be provided. A discharge pipe for discharging the ethanol aqueous solution 51 from the container 55 may be provided. A heater for controlling the temperature of the ethanol aqueous solution 51 in the container 55 may be provided. The ethanol aqueous solution 51 in this embodiment is a mixture of absolute ethanol and water in a ratio of 1:1. In this specification, absolute ethanol refers to high-concentration ethanol in which ethanol accounts for 95 vol% or more.

[0064] [Reforming device] The reforming apparatus 20 will be described in detail with reference to Figure 1. The reforming apparatus 20 includes a chamber 5, a light source 3, a fluid supply port 2 that supplies a first fluid F1 and a second fluid F2 into the chamber 5, a fluid discharge port 6 that discharges the fluids in the chamber 5 back into the chamber 5, and a table 15 on which a workpiece 10 is placed. In this embodiment, the light source 3 is disposed in a light source chamber 8 that is disposed above the chamber 5, and the light source chamber 8 and the chamber 5 are separated by a light-transmitting material such as quartz glass.

[0065] The reforming apparatus 20 is used, for example, in the following procedure. The workpiece 10 is carried onto the table 15 from outside the reforming apparatus 20 by a transport mechanism (not shown). A first fluid F1 and a second fluid F2 are supplied into the chamber 5 from the fluid supply port 2, and the atmosphere in the chamber 5 is replaced with the first fluid F1 and the second fluid F2. After the replacement is complete, the light source 3 is turned on to perform the reforming process while continuing to supply the first fluid F1 and the second fluid F2 to the chamber 5. After the reforming process is complete, the light source 3 is turned off, the supply of the first fluid F1 and the second fluid F2 is stopped, and the workpiece 10 is carried out from the table 15 to outside the chamber 5.

[0066] [Variations] The fluid supply source and the reformer may be configured in various ways. Modifications of the fluid supply source and the reformer are shown below.

[0067] A first modified example of the fluid supply source will be described with reference to Figure 4. The fluid supply source 31 includes a container 65 containing an ethanol liquid 61 and a container 75 containing water 71, which is a liquid.

[0068] A carrier gas supply pipe 62 is inserted into the ethanol liquid 61, and a carrier gas G1 is sent from the carrier gas supply pipe 62 to volatilize the ethanol liquid 61 by a bubbling method. As a result, a first fluid F1 containing the carrier gas G1 and ethanol gas is extracted. The ethanol liquid 61 is preferably high-concentration ethanol or anhydrous ethanol. The ethanol liquid 61 may also be an aqueous ethanol solution.

[0069] A carrier gas supply pipe 72 is inserted into the liquid water 71, and a carrier gas G2 is sent through the carrier gas supply pipe 72 to volatilize the water 71 by a bubbling method. This results in a second fluid F2 containing the carrier gas G2 and water vapor. The water 71 may be volatilized by heating, stirring, or applying ultrasonic vibrations to the water 71. As described above, the water contained in the second fluid F2 does not necessarily have to be water vapor, and may be atomized water suspended in the carrier gas G1.

[0070] The pipe 66 through which the first fluid F1 flows and the pipe 76 through which the second fluid F2 flows are joined at a joining section 67 and connected to the reformer 20. The pipe 66 and the pipe 76 may be connected to the reformer 20 separately without joining the pipes 66 and 76. The carrier gas G1 and the carrier gas G3 may be the same gas or different gases.

[0071] The mixture ratio of the first fluid F1 and the second fluid F2 can be adjusted by adjusting the flow rate ratio of the carrier gas G1 and the carrier gas G2. A flow rate adjustment valve for adjusting the mixture ratio of the two fluids may be disposed at the confluence 67.

[0072] By flowing carrier gas G1 without flowing carrier gas G2, the first fluid F1 can be sent to the reformer without sending the second fluid F2 to the reformer 20. Conversely, by flowing carrier gas G2 without flowing carrier gas G1, the second fluid F2 can be sent to the reformer 20 without sending the first fluid F1 to the reformer 20. Furthermore, a three-way valve for switching the flows of the two fluids may be disposed in the confluence part 67. The timing of supplying the first fluid F1 and the second fluid F2 can be shifted.

[0073] A second modified example of the fluid supply source will be described with reference to FIG. 5. The fluid supply source 32 employs a direct vaporization system. The fluid supply source 32 includes a container 85 containing an ethanol aqueous solution 81, a carrier gas supply pipe 87 through which a carrier gas G6 flows, a vaporizer 88, a mass flow controller 83 for controlling the amount of the ethanol aqueous solution 81, and a mass flow controller 84 for controlling the amount of the carrier gas G6. Fixed amounts of the carrier gas G6 and the ethanol aqueous solution 81 are supplied to the vaporizer 88 using the mass flow controllers (83, 84). The vaporizer 88 uses the supplied carrier gas G6 to instantly vaporize the entire amount of the supplied ethanol aqueous solution 81. As shown in FIG. 5, the ethanol aqueous solution 81 can be transported from the container 85 containing the ethanol aqueous solution 81 by supplying a pressurized gas G5 to the container 85. In addition, although FIG. 5 shows a configuration in which an ethanol aqueous solution 81 containing a first fluid F1 and a second fluid F2 is supplied to the vaporizer 88, the first fluid F1 and the second fluid F2 may be supplied separately to the vaporizer 88.

[0074] A first modified example of the reforming device will be described with reference to Figure 6. In the reforming device 21, two light sources 3 are arranged so that the longitudinal direction of each light source 3 faces from the front to the back of the drawing. A plurality of fluid supply ports 2 for the first fluid F1 and the second fluid F2 are provided on the ceiling of the chamber 1 so that the workpiece 10 can be treated evenly. The position and number of the fluid supply ports 2 can be set taking into consideration the flows of the first fluid F1 and the second fluid F2. Similarly, the position and number of the fluid discharge ports 6 can also be set.

[0075] Each light source 3 is housed in a tube 33 that extends from the front to the back of the drawing. At least the portion of the tube 33 that faces the workpiece 10 is made of a material that transmits ultraviolet light L1, such as quartz glass. The space 34 between the light source 3 and the tube 33 is filled with an inert gas that does not easily absorb ultraviolet light. This also prevents any altered fluid in the atmosphere from adhering to the surface of the light source 3, preventing a decrease in the illuminance of the light source 3.

[0076] The first fluid F1 and the second fluid F2 may be fed into the chamber 5 simultaneously as a mixed fluid (F1+F2) as shown in Fig. 6. Alternatively, the first fluid F1 may be fed into the chamber 5, and then the second fluid F2 may be fed into the chamber 5. Furthermore, the first step and the second step may be carried out in different chambers.

[0077] A second modified example of the reforming device will be described with reference to Figure 7. In the reforming device 22, ultraviolet light L1 is irradiated from a light source 3 toward a second fluid F2 passing through a pipe 46. This causes the second fluid F2 to be radicalized. Then, the second fluid F2 containing hydrogen radicals and OH radicals is sprayed from a tip 47 of the pipe 46 toward the workpiece 10 placed on the table 15. When the hydrogen radicals and OH radicals come into contact with the surface of the fluororesin of the workpiece 10, a hydrophilic layer is formed on the surface of the workpiece 10.

[0078] In this embodiment, by moving the workpiece 10 and the tip 47 relative to each other while maintaining a distance between them, it is possible to selectively process only the area of ​​the workpiece 10 that needs to be modified. Also, in this embodiment, it is not necessary to fill the entire processing space enclosed by a chamber or the like with the second fluid F2. Note that the modifying device 22 can be used in the same way both when using the first fluid F1 and when using a mixed fluid of the first fluid F1 and the second fluid F2.

[0079] The above describes one embodiment of the reforming system and modified examples of the fluid supply source and reforming device that constitute the reforming system. However, the present invention is not limited to the above embodiment and modified examples, and various modifications and improvements can be made to the above embodiment and modified examples without departing from the spirit of the present invention. [Example]

[0080] The effectiveness of the above modification method was confirmed by ATR-FTIR analysis and contact angle measurement experiments.

[0081] [ATR-FTIR analysis] Five PTFE (polytetrafluoroethylene) substrates manufactured by Yodogawa Hutech Co., Ltd. were prepared as the objects to be treated 10, and four of them were subjected to a hydrophilization treatment of the surface of the objects to be treated 10 using the modification system 100 of the embodiment shown in Figure 1.

[0082] The common processing conditions were as follows: The substrate was placed in the chamber 5 at a distance of 1 mm from the light source 3. A xenon excimer lamp with a peak wavelength of 172 nm was used as the light source 3. The irradiance on the surface of the light source 3 was 30 mW / cm. 2 Nitrogen gas was used as carrier gas G1 at a flow rate of 2 L (2 × 10 -3 m 3 ) was fed to vaporize the liquid in the container 55 by bubbling. As will be described later, the liquid differs depending on the sample.

[0083] Samples S1 to S5 have the following characteristics. [Table 1]

[0084] Sample S1 is a substrate (PTFE resin) that has not been modified. Sample S2 was irradiated with ultraviolet light for 30 seconds in an ethanol gas atmosphere, i.e., it was a sample that had undergone only the first step for 30 seconds. Sample S3 was irradiated with ultraviolet light for 120 seconds in an ethanol gas atmosphere, i.e., it was a sample that had undergone only the first step for 120 seconds. Sample S4 was irradiated with ultraviolet light for 30 seconds in an atmosphere of vaporized ethanol aqueous solution. In other words, it was a sample that underwent the first and second steps for 30 seconds. The ethanol aqueous solution was 10 mL (1 × 10 -5 m 3 ) absolute ethanol and 10 mL (1 × 10 -5 m 3 ) and water. Sample S5 was irradiated with UV light for 120 seconds in an atmosphere of vaporized ethanol solution. In other words, it was a sample that underwent both the first and second steps for 120 seconds. The ethanol solution used for S5 was the same as that used for S4.

[0085] Figures 8A and 8B show the results of ATR-FTIR analysis of the surface layers of five samples. In ATR-FTIR, a crystal with a higher refractive index than the sample is attached to the sample surface, infrared light is irradiated onto the sample from the crystal side, and the total reflected light that penetrates near the surface and is reflected is measured to obtain the absorption spectrum of the sample surface layer (approximately 1 μm from the surface). In Figures 8A and 8B, the horizontal axis represents wavenumber and the vertical axis represents absorbance. High absorbance indicates large amounts of absorbed infrared light energy. In each figure, S1 to S5 represent the absorption spectra of samples S1 to S5, respectively. The measurement device used was a Bruker VERTEX 70v. Diamond was used as the high-refractive-index crystal. The angle of incidence of the infrared light was 45 degrees.

[0086] The OH bond on the surface has a wave number of 3300 to 3400 cm -1 The surface C-H bond has a wave number of 2900 to 3000 cm -1 From Figure 8A, it can be seen that the number of OH bonds and CH bonds in the surface layer is higher in samples S5, S4, S3, S2, and S1 in that order. The C=O bonds in the surface layer have a wave number of 1700 to 1710 cm -1 From Figure 8B, it can be seen that the number of C=O bonds in the surface layer is highest in samples S5, followed by S4, S3, S2, and S1.

[0087] Since untreated sample S1 contains almost no OH, C═O, or C═O bonds, it is clear that these bonds are the result of modification of the fluororesin surface layer. Furthermore, since the surface modification progresses in the order of samples S5, S4, S3, and S2, it is clear that samples S4 and S5, which were modified in an ethanol aqueous solution atmosphere, have more surface modification than samples S2 and S3, which were modified only in an ethanol gas atmosphere, and that samples S3 and S5, which were treated for 120 seconds, have more surface modification than samples S2 and S4, which were treated for 30 seconds.

[0088] [Contact angle measurement] Using the modification system 100 of the embodiment shown in FIG. 1, a hydrophilization treatment was performed on the surface of the object 10 to be treated. The object 10 was made of PTFE (polytetrafluoroethylene) manufactured by Yodogawa Hutech Co., Ltd. Nitrogen gas was supplied to the liquid in the container 55 as a carrier gas G1 at a flow rate of 2 L (2 × 10) per minute. -3 m 3 ), and the liquid in the container 55 was vaporized by bubbling and supplied to the chamber 5. As will be described later, the liquid differs depending on the sample. The substrate was placed in the chamber 5 at a distance of 1 mm from the light source 3. The light source 3 was a xenon excimer lamp with a peak wavelength of 172 nm. The irradiance at the surface of the light source 3 was 30 mW / cm. 2 Nitrogen gas was used as carrier gas G1 at a flow rate of 2 L (2 × 10 -3 m 3 ) was fed into the container 55, and the liquid in the container 55 was vaporized by bubbling. A contact angle meter DMs-401 manufactured by Kyowa Interface Science Co., Ltd. was used to measure the water contact angle. The contact angle was calculated from the measurement results of the contact angle meter using an ellipse curve fitting method. This contact angle calculation was performed at three locations on the surface of the same workpiece 4. The water contact angles measured at the three locations were averaged, and this average value was determined to be the final water contact angle. Other measurement conditions for the water contact angle were in accordance with JIS R 3257, "Test method for wettability of substrate glass surfaces."

[0089] FIG. 9 is a graph showing the relationship between the modification treatment time (sec) and the contact angle (deg). The horizontal axis represents the treatment time of the object 10, and the vertical axis represents the water contact angle on the surface of the object 10. The lower the water contact angle, the more hydrophilic the object 10 is.

[0090] As shown in FIG. 9, the contact angle before treatment is 119 degrees, indicating high hydrophobicity. The solid line D1 is the measurement result when an ethanol aqueous solution is used as the "liquid in container 55," and the first fluid and the second fluid are used (i.e., when both the first step and the second step are performed). The dashed line D2 is the measurement result when an ethanol liquid (absolute ethanol) is used as the "liquid in container 55," and only the first fluid is used (i.e., when only the first step is performed). The dashed line D3 is the measurement result when water is used as the "liquid in container 55," and only the second fluid is used.

[0091] 9, it can be seen that when both the first and second steps are performed, hydrophilization can be achieved in a shorter time than when only the first step is performed. It can also be seen that hydrophilization cannot be achieved by the second step alone, but can be achieved by performing the second step in combination with the first step. [Explanation of symbols]

[0092] 1: Chamber 2 :Fluid supply port 3:Light source 5: Chamber 6 :Fluid outlet 7: Tip 8:Light source room 10: Object to be treated 11: Fluorine resin 15: Table 20, 21, 22: Reformer 30,31,32:Fluid supply source 33: Tube 34: Space 46: Piping 47: (pipe) tip 51,81: Aqueous ethanol solution 52: Carrier gas supply pipe 53:Flowmeter 54: Valve 55,65,75,85: Container 56:Fluid supply pipe 61: Ethanol solution 62: Carrier gas supply pipe 66,76:Piping 67: Junction 71:Water 72, 87: Carrier gas supply pipe 83,84: Mass flow controller 88: Vaporizer 100: Reforming system F1: First fluid F2:Second fluid G1, G2, G3, G6: Carrier gas G5: Compressed gas L1: Ultraviolet light

Claims

1. a first step of irradiating a first fluid containing an organic compound containing an oxygen atom with ultraviolet light having an intensity in a wavelength range of at least 205 nm or less, and bringing the first fluid irradiated with the ultraviolet light into contact with a fluororesin; a second step of irradiating a second fluid containing gas or atomized water with the ultraviolet light and bringing the second fluid irradiated with the ultraviolet light into contact with the fluororesin; A method for modifying a fluororesin, comprising:

2. 2. The method according to claim 1, wherein the ultraviolet light is irradiated onto a gaseous or mist-like mixed fluid obtained by mixing the first fluid and the second fluid in a gaseous or mist-like state, and the first step and the second step are carried out in parallel.

3. The method according to claim 1, wherein the second step is carried out after the first step.

4. The modification method according to any one of claims 1 to 3, wherein at least one of the first step and the second step is performed by irradiating the ultraviolet light toward a fluid in contact with the fluororesin.

5. 4. The method according to claim 1, wherein the organic compound contains at least one of a hydroxy group, a carbonyl group, and an ether bond.

6. 6. The method according to claim 5, wherein the organic compound includes at least one selected from the group consisting of alcohols, ketones, aldehydes, carboxylic acids, and phenols.

7. 7. The method according to claim 6, wherein the organic compound includes at least one selected from the group consisting of alcohols having 10 or less carbon atoms and ketones having 10 or less carbon atoms.

8. 8. The method according to claim 7, wherein the organic compound includes at least one selected from the group consisting of alcohols having 2 to 4 carbon atoms and acetone.

9. 4. The method according to claim 1, wherein the ultraviolet light is generated by a xenon excimer lamp.

10. at least one fluid supply port for supplying a first fluid containing an organic compound containing an oxygen atom and a second fluid containing gas or atomized water into the chamber; a light source that irradiates the first fluid and the second fluid in the chamber with ultraviolet light that exhibits intensity in a wavelength range of 205 nm or less; A modifying apparatus, characterized in that a surface layer of an object to be treated is made hydrophilic by the first fluid irradiated with ultraviolet light and the second fluid irradiated with ultraviolet light.

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