Method for forming a thin film on a solid surface using atmospheric pressure plasma, and atmospheric pressure plasma apparatus used in the method.

Abstract

The present invention provides a method for forming a thin film on a solid surface using atmospheric pressure plasma, which allows for the rapid formation of a thin film that is physically and chemically strong and solvent-insoluble on most solid surfaces, thereby reducing manufacturing costs and producing no residue during the process, as well as an atmospheric pressure plasma apparatus used in this method. [Solution] A method for forming a thin film on a solid surface using atmospheric pressure plasma, wherein the thin film is physically and chemically strong and solvent-insoluble, and the method comprises the steps of adsorbing or coating polyethylene glycol over the entire solid surface, and irradiating the solid surface on which polyethylene glycol has been adsorbed or coated with a predetermined rare gas atmospheric pressure plasma to cause a plasma crosslinking reaction of the polyethylene glycol on the solid surface, thereby forming a thin film of polyethylene glycol on the solid surface.

Description

[Technical Field]

[0001] This invention relates to a method for forming a thin film on a solid surface using atmospheric pressure plasma, which forms a thin film that is physically and chemically strong and solvent-insoluble on most solid surfaces, and to an atmospheric pressure plasma apparatus used in this method. [Background technology]

[0002] Micro-sized solid particles are used in a variety of fields. For example, powders used in foundation cosmetics have particle sizes ranging from 10 nm to 20 μm, and various shapes are used, including flattened, spherical, hollow, and irregular shapes. The materials used for the powders vary widely, with polymers such as polyethylene and acrylic, and inorganic powders such as titanium dioxide and zinc oxide being commonly used. These differences significantly impact the feel of the product, its adherence to the skin, its moisturizing effect, and its UV protection capabilities.

[0003] In general, ultrafine particles with a diameter of approximately 100 nm or less relative to the particle size tend to be avoided in cosmetics due to concerns about their penetration into the skin. On the other hand, many problems remain with the UV-blocking materials currently used in UV cosmetics and other products.

[0004] Currently, two types of UV shielding materials are used: organic (chemical) and inorganic (non-chemical). For example, organic materials such as cinnamic acid, benzophenone, and triazine are used, but because these absorb incident UV light through changes in their molecular structure, the effects of the resulting products on the skin cannot be ruled out, and they may become subject to regulation.

[0005] Furthermore, as non-chemical materials, titanium dioxide and zinc oxide are highly effective as UV reflectors due to their high refractive index and transparency, and are widely used, but each still presents significant problems. For example, titanium dioxide has strong photo-oxidation properties due to its absorption of ultraviolet light, and it is well known that this can cause oxidative decomposition of surrounding organic matter or damage to the skin. Zinc oxide, while not to the same extent as titanium dioxide, also has photo-oxidation properties and some solubility in cosmetic materials, which presents its own problems.

[0006] However, it is clear that if the photo-oxidation properties of titanium dioxide, which has a high refractive index, can be suppressed, it would be more suitable as a cosmetic material than zinc oxide. Therefore, various attempts have been made to suppress the photo-effect of titanium dioxide.

[0007] The conventional first method involves coating titanium dioxide with a silane coupling agent or silicone. A conventional second method involves directly forming a polymerized film on the surface of titanium dioxide particles. A conventional third method is a physical method that enables the formation of extremely strong thin films by sputtering in a vacuum plasma or amorphous carbon deposition. A conventional fourth method involves forming a silica thin film on the titanium oxide powder surface using atmospheric pressure plasma CVD (Chemical Vapor Deposition) of tetraethoxysilane (Non-Patent Literature 1). [Prior art documents] [Patent Documents]

[0008] [Non-Patent Document 1] 9th.Simposium on Plasma Science of Materials.(1997.9) [Disclosure of the Invention] [Problems that the invention aims to solve]

[0009] According to the conventional first method, due to the difficulty of obtaining a homogeneous thickness in nature, etc., there is a possibility that unreacted portions remain on a part of the surface, and there is a drawback that the light reaction blocking property is not sufficient.

[0010] According to the conventional second method, polymerization reaction accelerators, catalysts, etc. may be used, and there are concerns about the influence on health due to their residues.

[0011] According to the conventional third method, since vapor deposition on fine powder requires long-time treatment in a vacuum, there are no practical examples.

[0012] According to the conventional fourth method, although the effect of preventing the coloring and odor generation of the dispersion can be recognized even when irradiating ultraviolet rays to a dispersion obtained by dispersing silica-treated titanium oxide in squalane, in addition to the need for preliminary complicated powder treatment to perform this treatment, plasma oxidation treatment has to be performed for a long time, and there is a disadvantage that the manufacturing cost becomes enormous.

[0013] An object of the present invention is to solve the above-mentioned drawbacks of the prior art, form a physically and chemically strong and solvent-insoluble thin film on almost all solid surfaces in a short time, reduce the manufacturing cost, and provide a method for forming a thin film on a solid surface using atmospheric pressure plasma without residues associated with the treatment and an atmospheric pressure plasma device used in the method.

Means for Solving the Problems

[0014] In order to achieve the above object, a method for forming a thin film on a solid surface using atmospheric pressure plasma according to the invention described in claim 1 is a method for forming a thin film on a solid surface, which forms a physically and chemically strong and solvent-insoluble thin film on the solid surface using atmospheric pressure plasma, a step of adsorbing or applying polyethylene glycol to the entire solid surface, a step of irradiating a solid surface adsorbed or applied with polyethylene glycol with a predetermined rare gas atmospheric pressure plasma to cause a plasma crosslinking reaction of the polyethylene glycol on the solid surface to form a thin film of polyethylene glycol on the solid surface It is something that is provided.

[0015] The method for forming a thin film on a solid surface according to claim 2 is characterized in that, in the invention described in claim 1, the noble gas is helium gas, argon gas, or a mixture thereof.

[0016] To achieve the above objective, the method for forming a solid surface thin film using atmospheric pressure plasma according to claim 3 is: A method for forming a thin film on a solid surface using atmospheric pressure plasma, which enables the adsorption or application of polyethylene glycol to the entire surface of a hydrophobic solid even when polyethylene glycol cannot be adsorbed or applied to the entire surface of the solid, and forms a thin film on the solid surface that is physically and chemically strong and insoluble in solvents, A process of oxidizing the surface of a hydrophobic solid by irradiating it with a mixed gas plasma of a rare gas and oxygen gas, A step of adsorbing or coating polyethylene glycol onto the entire oxidized solid surface, A process to obtain a polyethylene glycol film on a solid surface to which polyethylene glycol has been adsorbed or coated, by irradiating a predetermined rare gas atmospheric pressure plasma to cause a plasma crosslinking reaction of polyethylene glycol on the solid surface. It is characterized by having the following features.

[0017] The method for forming a thin film on a solid surface according to claim 4 is characterized in that, in the invention described in claim 3, the noble gas is helium gas, argon gas, or a mixture thereof.

[0018] To achieve the above objective, the atmospheric pressure plasma apparatus according to claim 5 is: An atmospheric pressure plasma apparatus used in a solid surface thin film formation method for forming a thin film on a solid surface that is physically and chemically strong and solvent-insoluble, using atmospheric pressure plasma, A cylindrical body that can rotate around a horizontally positioned axis of rotation, A first electrode provided on the outer circumference of the cylindrical body, A second electrode of a predetermined shape is provided inside the cylindrical body, An introduction means for introducing atmospheric pressure noble gas into the cylindrical body, A discharge means for discharging gas from inside the cylinder, A power supply device that supplies high-frequency high-voltage voltage to the first electrode and the second electrode, It is characterized by having the following features. [Effects of the Invention]

[0019] According to the method for forming a thin film on a solid surface using atmospheric pressure plasma according to the invention described in claim 1, • It is possible to form a thin film on a solid surface that is physically and chemically strong and insoluble in solvents. • Thin films can be formed on solid surfaces in a short time. • The process is simple and manufacturing costs can be reduced. • When forming a thin film that is physically and chemically strong and insoluble in solvents on a solid surface, no residue is generated. • Manufacturing costs can also be reduced.

[0020] According to the method for forming a thin film on a solid surface according to claim 3, Even hydrophobic solids can have their surfaces oxidized with a mixed gas plasma of rare gas and oxygen gas, allowing polyethylene glycol to be adsorbed or applied to the solid surface. • It is possible to form a thin film on a solid surface that is physically and chemically strong and insoluble in solvents. • Thin films can be formed on solid surfaces in a short time. • The process is simple and manufacturing costs can be reduced. • When forming a thin film that is physically and chemically strong and insoluble in solvents on a solid surface, no residue is generated. • Manufacturing costs can also be reduced.

[0021] According to the solid surface thin film forming apparatus of the invention described in claim 5, • Its simple structure ensures reliable thin-film formation on solid surfaces. • It can oxidize hydrophobic solid surfaces. • A thin film that is physically and chemically strong and insoluble in solvents can be formed on a solid surface easily and at low cost. [Brief explanation of the drawing]

[0022] [Figure 1] This flowchart illustrates an overview of a method for forming a thin film on a solid surface using atmospheric pressure plasma according to an embodiment of the present invention. [Figure 2] This figure shows an example of the configuration of an atmospheric pressure plasma apparatus used in a solid surface thin film formation method according to an embodiment of the present invention. [Figure 3] This is a characteristic diagram showing the hydrophilicity of a thin film formed on a solid surface by a solid surface thin film formation method using atmospheric pressure plasma according to an embodiment of the present invention. [Figure 4] This characteristic diagram shows the results of measuring the ultraviolet absorption capacity of a thin film formed on a solid surface by a solid surface thin film formation method using atmospheric pressure plasma according to an embodiment of the present invention. [Figure 5] This is a characteristic diagram illustrating the wettability evaluation under condition 1 in a solid surface thin film formation method using atmospheric pressure plasma according to another embodiment of the present invention. [Figure 6] This is a characteristic diagram illustrating the wettability evaluation under condition 2 in a solid surface thin film formation method using atmospheric pressure plasma according to another embodiment of the present invention. [Figure 7] This is a characteristic diagram illustrating the state of a solid surface when the solid surface thin film formation method using atmospheric pressure plasma according to another embodiment of the present invention is not applied. [Figure 8] This characteristic diagram illustrates the results of measuring the surface molecular structure of a solid formed using a solid surface thin film formation method using atmospheric pressure plasma according to another embodiment of the present invention, and the surface molecular structure of the solid at each step before plasma crosslinking. [Figure 9] This characteristic diagram illustrates the results of measuring the surface molecular structure of a solid surface with a thin film formed using a solid surface thin film formation method using atmospheric pressure plasma according to another embodiment of the present invention, as well as the surface molecular structure of a solid surface with a thin film formed using this method and a solid surface with a thin film formed using this method. [Modes for carrying out the invention]

[0023] Hereinafter, embodiments and examples for carrying out the present invention will be described with reference to the drawings. Figure 1 is a flowchart illustrating the outline of a solid surface thin film formation method using atmospheric pressure plasma according to an embodiment of the present invention.

[0024] In Figure 1, the method for forming a thin film on a solid surface using atmospheric pressure plasma is divided into cases where the solid surface is hydrophilic and cases where it is hydrophobic. If the solid surface is hydrophobic, a plasma oxidation treatment (step 0) is performed in advance before proceeding to the next step 1. However, if the solid surface is hydrophilic, the process consists of a step of adsorbing or coating polyethylene glycol onto the solid surface (step 1) and a treatment method (step 2) in which a predetermined rare gas atmospheric pressure plasma is irradiated onto the solid surface on which polyethylene glycol has been adsorbed or coated to cause a plasma crosslinking reaction of polyethylene glycol on the solid surface to obtain a polyethylene glycol film on the solid surface.

[0025] Further details will be provided. In embodiments for carrying out the present invention (hereinafter also simply referred to as "embodiments of the present invention"), titanium dioxide powder is used as the solid. This is because titanium dioxide is suitable as a cosmetic material as long as its photo-oxidation properties can be suppressed.

[0026] Furthermore, in embodiments of the present invention, polyethylene glycol (hereinafter referred to as PEG) or polylactic acid (hereinafter referred to as PLA) is used to suppress the photo-oxidation properties of titanium dioxide. The reason for using PEG is that non-crosslinked PEG possesses both strong hydrophilicity and lipophilicity, is inert to biomolecules such as proteins and cells and does not form adsorptions or bindings, is non-toxic, and is soluble in water and alcohol. On the other hand, non-crosslinked PLA has a molecular structure similar to that of PEG and is a material used in DDS (drug delivery systems) due to its biodegradable properties. Plasma crosslinking is possible with a similar process to that of PEG, but since the crosslinking process for PEG and PLA is substantially the same, only the processing of PEG will be described here.

[0027] [Process 1] In an embodiment of the present invention, step 1 involves immersing titanium oxide powder in PEG alcohol or aqueous solution to adsorb PEG onto the entire surface of the titanium oxide powder. Thereafter, the PEG-coated titanium oxide powder is dried.

[0028] [Process 2] In step 1, the titanium oxide powder, which has PEG adsorbed and coated over its entire surface, is exposed to a rare gas atmospheric pressure plasma atmosphere. That is, the titanium oxide powder is irradiated with a predetermined rare gas atmospheric pressure plasma to cause a plasma crosslinking reaction of the PEG on the surface of the titanium oxide powder, thereby obtaining a PEG crosslinked film on the surface of the titanium oxide powder.

[0029] Here, in step 2, roughly He + Electron → He * (2 3 S), Electronic energy approximately 20 [eV]) ...(1) Electron excitation reaction He*+PEG (surface)→Crosslinked PEG+He ...(2) (Here, He* is a metastable electronic excited state of He.) The reaction shown takes place, thereby obtaining a PEG film on the surface of the titanium oxide powder. Thus, in step 2, the reaction is completed with only reaction (2) following reaction (1), and does not involve oxidation or reduction reactions, making it an energy-saving reaction. The crosslinking reaction of relatively low molecular weight polymers and the solid surface thin-film formation mechanism by atmospheric pressure plasma irradiation described above can be applied not only to hydrophilic polymers such as PEG and PLA, but also to crosslinking and thin-film formation of fluorine-based and silicon-based hydrophobic polymers and low molecular weight polymers with various reactive functional groups such as amino groups, amide groups, carboxyl groups, and sulfone groups onto solid surfaces. Furthermore, since the crosslinking reaction in step 2 does not subject the PEG film on the titanium oxide powder surface to excessive chemical stress such as oxidation, it is less likely to damage the original PEG molecular structure itself. As a result, a dense solid thin film can be easily constructed on the titanium oxide powder surface while maintaining the hydrophilic molecular structure characteristic of PEG.

[0030] Figure 2 shows an example configuration of an atmospheric pressure plasma apparatus used to perform step 2 in the solid surface thin film formation method according to an embodiment of the present invention. In Figure 2, the atmospheric pressure plasma device 1 is a plasma device that can irradiate titanium oxide powder, on which PEG has been attached to a solid surface, with plasma in an atmospheric pressure atmosphere. This atmospheric pressure plasma apparatus 1 comprises a cylindrical body 3 rotatable around a rotation axis 2 arranged horizontally, a first electrode 4 provided on the outer circumference of the cylindrical body, a second electrode 5 of a predetermined shape provided inside the cylindrical body, a gas introduction means 6 for introducing atmospheric pressure rare gas into the cylindrical body, a gas discharge means 7 for discharging the gas inside the cylindrical body, and a power supply device 8 for supplying high-frequency high-voltage voltage to the first electrode and the second electrode. The apparatus generates a rare gas atmospheric pressure plasma between the first electrode 4 and the second electrode 5 and irradiates the titanium oxide powder with He gas atmospheric pressure plasma to plasma crosslink the PEG on the entire surface of the titanium oxide powder.

[0031] To further explain the above structure, the rotating shaft 2 is composed of a left central shaft tube 21, a right central shaft tube 22, a resin joint 23, and metal central bearings 24 and 25. Both central bearings are electrically connected to an external ground. The left central shaft tube 21 and the right central shaft tube 22 are made of conductive hollow pipes that allow gas to flow, but the left end of the left central shaft tube 21 and the right end of the right central shaft tube 22 are closed to stop the flow of gas. Furthermore, the left central shaft tube 21 of the rotating shaft 2 is an axis that extends from the center to the left side of the shown part, and the right central shaft tube 22 of the rotating shaft 2 is an axis that extends from the center to the right side of the shown part.

[0032] The right end of the left central shaft pipe 21 and the left end of the right central shaft pipe 22 are connected at the center of the diagram by a resin joint 23. This resin joint 23 maintains the central axis of the left central shaft pipe 21 and the right central shaft pipe 22, and also prevents the flow of gas between the two shaft pipes 21 and 22.

[0033] Furthermore, the left central shaft tube 21 is fixed by the central shaft tube bearing 24, and the right central shaft tube bearing 25, both of which stop the rotation axis of the central shaft tube. The cylindrical body 3 described above comprises a Pyrex® glass rotating cylinder 31 (also simply referred to as "rotating cylinder 31"), polycarbonate flanges 32 and 33 fixed to both ends of the rotating cylinder 31, Wilson seals 34 and 35 positioned on the outside of the flanges 32 and 33, and flange fastening fittings 36 and 37. The flanges 32 and 33 are positioned on rotating rubber cylinders 38 and 39, and the rotational force of the rotating rubber cylinders 38 and 39 is transmitted to the flanges 32 and 33, causing the rotating cylinder 31 to rotate.

[0034] The first electrode 4 is also called a high-voltage wire mesh electrode, and this high-voltage wire mesh electrode is a stainless steel mesh electrode provided along the outer surface of the rotating cylinder 31, and is formed to be slightly shorter than the lateral length of the rotating cylinder 31.

[0035] The second electrodes 5,5 are also called ground electrodes, and these ground electrodes 5,5 are provided inside the rotating cylinder 31 and are formed in a spiral (coil) shape from copper pipe. Hereinafter, these ground electrodes 5,5 will also be referred to as coiled ground electrodes. One coiled ground electrode 5 is fixed to the left central shaft tube 21, and the other coiled ground electrode 5 is fixed to the right central shaft tube 22. These coiled ground electrodes 5,5 are arranged along the inner surface of the rotatable glass cylindrical tube 31 and are set up so that a discharge gap 9 is formed at a slight distance from the inner surface of the glass cylindrical tube 31. In this embodiment, the shortest distance between this discharge gap 9 (i.e., the inner surface of the glass rotating cylinder 31 and the coiled ground electrodes 5,5) is approximately 7 [mm], which effectively becomes the discharge space (discharge gap) 9.

[0036] Furthermore, one coil-shaped ground electrode 5 is grounded via the left central shaft tube 21 and central bearing 24, while the other coil-shaped ground electrode 5 is grounded via the left central shaft tube 22 and central bearing 25.

[0037] The gas introduction means 6 consists of a T-joint 61 provided on the left side of the central bearing 24 of the left central shaft pipe 21, the left central shaft pipe 21 with its left end closed, and a gas inlet 62 provided on the left central shaft pipe 21 inside the rotating cylinder 31 of the cylindrical body 3. It is designed to take in He gas from the gas inlet 61a of the T-joint 61 and supply He gas into the rotating cylinder 31 from the discharge port 62 via the left central shaft pipe 21. The gas discharge means 7 consists of a T-joint 71 provided on the right side of the central bearing 25 of the right central shaft pipe 22, the right central shaft pipe 22, and an intake port 72 provided on the right central shaft pipe 22 inside the rotating cylinder 31 of the cylindrical body 3. It is designed to take in He gas from inside the rotating cylinder 31 from the intake port 72 and discharge it from the gas outlet 71a of the T-joint 71 via the right central shaft pipe 22.

[0038] Reference numeral 8 denotes a power supply device, which is connected to the first electrode 4 and to ground, and can supply a high-frequency high-voltage to the first electrode 4 and the second electrode 5.

[0039] To explain in more detail, in Figure 2, for example, a Pyrex® glass rotating cylinder 31 with an outer diameter of 120 mm and a length of 230 mm is sealed on both sides by polycarbonate flanges 32 and 33. The glass rotating cylinder 31 and the flanges 32 and 33 are integrated by an O-ring packing. The flanges 32 and 33 are in contact with the rotating rubber cylinders 38 and 39 of the ball mill that rotate below them, and can rotate together with the rotation of the rotating rubber cylinders 38 and 39.

[0040] On the other hand, the stainless steel central shaft tubes (left central shaft tube 21 and right central shaft tube 22) with a diameter of approximately 10 mm do not rotate, but by providing Wilson seals 34 and 35 in the center of the flanges 32 and 33 on both sides of the glass rotating cylinder 31, it is possible to rotate only the glass rotating cylinder 31 while isolating it from the outside air.

[0041] Furthermore, He gas at atmospheric pressure and a flow rate of 3 [SLM] is introduced into the glass rotating cylinder 31 from the discharge port 62 through the T-joint 61 and the inside of the left central shaft pipe 21, and the gas is discharged from the suction port 72 of the right central shaft pipe 22 through the right central shaft pipe 22 and via the T-joint 71.

[0042] An atmospheric pressure plasma device 1 with this structure operates as follows: A high-frequency, high-voltage current is applied from a power supply unit 8 between a stainless steel mesh electrode (first electrode) 4 installed on the outer surface of the glass rotating cylinder 31 and coil-shaped ground electrodes (second electrodes) 5, 5 inside the rotating cylinder 31. At the same time, helium (He) gas is introduced into the rotating cylinder 31 through a T-joint 61, a left central shaft pipe 21, and a discharge port 62. The He gas is supplied into the glass rotating cylinder 31 at atmospheric pressure with a flow rate of 3 [SLM]. A glow discharge (plasma flow) is generated inside the glass rotating cylinder 31 filled with He gas.

[0043] A certain amount of titanium oxide powder (with PEG adsorbed and coated on its entire surface) that has been pre-filled into the glass rotating cylinder 31 is exposed to a plasma flow for a certain period of time while being rotated and stirred together with the glass rotating cylinder 31.

[0044] Here, a high-frequency voltage of, for example, 100 kHz was applied from the power supply unit 8 to the wire mesh electrode (first electrode) 4 on the outside of the rotating cylinder 31 and the coil-shaped ground electrodes (second electrode) 5, 5 inside the rotating cylinder 31. An automatic matching unit was also used as needed. The discharge frequency does not have to be 100 kHz; it may be a higher frequency or even a lower frequency. In this embodiment, He gas was used as the atmospheric pressure noble gas for discharge, but argon (Ar) gas or a mixture thereof may also be used.

[0045] Furthermore, although the coil-shaped ground electrodes 5,5, which are discharge electrodes inside the glass rotating cylinder 31, are formed in a spiral shape (coil shape) in this embodiment, the shape is not limited to this. For example, the electrode structure may be one in which a plurality of straight rod-shaped conductors are arranged at regular intervals along the rotation axis 2, maintaining a constant distance from the inner circumferential surface of the glass rotating cylinder 31, or a shape such as a metal mesh cylindrical body with a coarse mesh.

[0046] In the atmospheric pressure plasma apparatus 1 according to this embodiment, the discharge process is performed as follows. First, each individual titanium oxide powder is coated with PEG adsorbed onto its entire surface (Step 1). These 30 grams of titanium oxide powder are thrown into the glass rotating cylinder 31 of the cylindrical body 3 of the atmospheric pressure plasma device 1. Furthermore, by supplying high-frequency power at a discharge power of 300 w for 30 minutes between the first electrode (wire mesh electrode) 4 and the second electrode (coil-shaped ground electrode) 5, 5 from the power supply device 8, atmospheric pressure plasma is generated in the discharge space, and discharge treatment is performed on the titanium oxide powder coated with adsorbed PEG. As explained again, the discharge space (discharge void) 9 refers to the space (void) between the inner surface of the glass rotating cylinder 31 and the spiral-shaped electrodes (second electrodes) 5, 5 inside the glass rotating cylinder 31.

[0047] Then, when the titanium oxide powder is subjected to discharge treatment in the discharge space 9, the glass rotating cylinder 31 of the cylindrical body 3 rotates together with the rotation of the rotating rubber cylinders 38 and 39, with which the flanges 32 and 33 are in contact. As the glass rotating cylinder 31 rotates in this way, the titanium oxide powder inside the glass rotating cylinder 31 is stirred within the discharge space 9 and evenly exposed to atmospheric pressure plasma.

[0048] In this way, according to the embodiment of the present invention, by obtaining the above-described process, titanium oxide powder can be obtained in which a PEG film is formed on the surface of each titanium oxide powder.

[0049] Next, the titanium dioxide powder obtained by this embodiment will be subjected to the following tests to examine the state of PEG film formation on the surface of the titanium dioxide powder: (a) hydrophilicity test, (b) relationship between the thickness of the adsorbed film on titanium dioxide and the amount added, (c) UV irradiation test, (d) dispersibility of PEG-crosslinked titanium dioxide particles in pure water, (e) measurement of ultraviolet absorption capacity, (f) efficacy as a cosmetic additive, and (g) overall summary.

[0050] (i) Regarding hydrophilicity tests Figure 3 is a characteristic diagram showing the hydrophilicity of a thin film formed by a solid surface thin film formation method using atmospheric pressure plasma according to an embodiment of the present invention, with the horizontal axis representing the immersion time t and the vertical axis representing "l squared". The hydrophilicity test was performed using the capillary lifting method ("Dictionary of Powder Technology Terms," ​​published by the Society of Powder Technology, Japan) to determine whether the surface of the plasma-treated PEG-coated titanium oxide powder in the above embodiment was coated with hydrophilic cross-linked PEG. This capillary rise method is primarily used to measure the surface energy or contact angle of a powder surface. It involves uniformly packing powder into a vertically positioned glass tube with an inner diameter of 5 mm, immersing the lower end in a benzyl alcohol solution, and measuring the time change in the position l of the tip of the tube from the lower end as the liquid rises within the tube due to capillary action. The square of l (l) is used to measure this change. 2 (to be displayed as) l 2 ={(rγCOSθ) / 2η}t ...(1 set) It is known that this will happen. Here, r is the inner radius of the capillary, γ is the surface tension of the liquid, and η is the viscosity of the liquid. θ corresponds to the contact angle with the solid plane. In reality, r, γ, and η are constants, so "l 2 / square meter (hereinafter referred to as "m") 2 The magnitude of the slope between "(denoted as ")" and "immersion time t [seconds]" represents the surface energy including the constant term. A high surface energy means that the wettability is high, that is, the hydrophilicity is high.

[0051] In Figure 3, the crosslinked PEG-coated titanium oxide powder is l 2 The solid line shows the measured values ​​for immersion time t (seconds). The dotted line shows the slope. In reality, there is a distribution in the diameter of spherical titanium oxide, so calculating the exact surface energy is complex. However, the magnitude of the slope itself represents the strength of hydrophilicity, so it is possible to compare the hydrophilicity of untreated titanium oxide particles by measuring them using the same device.

[0052] When measuring the capillary rise of untreated titanium dioxide using glass tubes of the same diameter, no liquid rise was observed inside the glass tube when one end of the tube was immersed in benzyl alcohol. This is thought to be because the untreated titanium dioxide particles do not have hydrophilicity.

[0053] Furthermore, Figure 3 shows that in the PEG-coated titanium oxide crosslinked powder, the position of the liquid tip rises smoothly over time as the immersed liquid in the tube rises. In contrast, in the state where PEG was simply adsorbed or coated onto the titanium oxide powder before crosslinking (the state after step 1), the liquid rise completely stopped shortly after immersion in benzyl alcohol. This is thought to be because the uncrosslinked PEG film dissolved into the rising benzyl alcohol and filled the gaps in the powder (increase in viscosity η), stopping the liquid from rising.

[0054] From the above description, it is clear that a solid film with strong hydrophilicity and insolubility in benzyl alcohol is formed on the surface of the crosslinked PEG-coated titanium oxide obtained according to the embodiment of the present invention.

[0055] (b) Regarding the relationship between the thickness and the addition amount of the PEG adsorption film on titanium oxide Regarding the titanium oxide used in the embodiment of the present invention, the surface area of each of these titanium oxide powders is 14 [1 g / m 2 according to the data of "Toho Titanium Co., Ltd." where it is manufactured. That is, if PEG is spread over the entire surface of the powder with a thickness of 1 [nm] on an area of 1.4 × 10 19 [nm 2 / g], the volume will be 1 [nm] × 1.4 × 10 19 [nm 2 / g], and the calculation result will be 0.014 [cm 3 (cubic centimeter)]. Assuming the specific gravity of PEG is 1.1, then 1.1 × 0.014 [cm 3 = 0.0154 [g PEG] / [g titanium oxide] In the case of 30 [g] of titanium oxide, 0.015 × 30 = 0.45 [g]. In fact, 0.9 [g] of PEG was adhered in total amount. It means that an extremely thin PEG film of about 2 [nm] or less was formed on the surface of the titanium oxide particles in terms of calculation.

[0056] (c) Regarding the UV irradiation test It is important to know how the titanium oxide powder with an extremely thin PEG film formed obtained in the embodiment of the present invention behaves when exposed to UV (ultraviolet). Therefore, the PEG-crosslinked titanium oxide powder was mixed with squalane, and the intensity of the odor generated after irradiating with ultraviolet rays was observed.

[0057] Here, squalane (C 30 H 62Titanium dioxide (TID) is a saturated hydrocarbon and is often used as an ingredient in cosmetics because it is believed to have cosmetic effects. In the same manner as in the conventional method, where the intensity of the odor generated after mixing PEG-coated titanium dioxide powder with squalane and irradiating it with ultraviolet light was measured, the intensity of the odor generated after mixing the PEG-crosslinked titanium dioxide obtained in the embodiment of the present invention with squalane and irradiating it with ultraviolet light was observed.

[0058] First, 0.8 g of PEG-free titanium dioxide powder was taken and mixed with 8 ml of squalane. This mixture was then placed in a 300 ml Pyrex® Erlenmeyer flask and thoroughly dispersed. Subsequently, the mixture was irradiated with ultraviolet light from a low-pressure mercury lamp for 1 hour. A 190 W mercury lamp manufactured by Kyoshin Electric Co., Ltd. was used, and ultraviolet light was irradiated for 1 hour at a distance of approximately 15 cm from the bottom of the Erlenmeyer flask. After heating at 100 °C for 1 hour, the powder and liquid turned light brown, and a strong odor was observed in the liquid.

[0059] Previously, Ono et al. (Non-Patent Literature 1) reported that when untreated titanium dioxide powder was dispersed in squalane and irradiated with ultraviolet light, a strong odor was observed. As mentioned earlier, GCMS observation of the odor revealed the generation of large amounts of acetone and other organic acid molecules. This is known as the photochemical effect of titanium dioxide in air (Honda-Fujishima effect), and it is believed that the strong odor was generated as a result of titanium dioxide photo-oxidizing squalane molecules, producing peroxides such as organic acids.

[0060] On the other hand, the intensity of the odor generated after irradiating the PEG crosslinked titanium oxide powder obtained in the embodiment of the present invention with ultraviolet light was observed as follows. First, the same amount (0.8 g) of PEG cross-linked titanium dioxide powder as above was mixed with the same amount (8 ml) of squalane as above, and then the mixture was placed in a 300 ml Erlenmeyer flask and thoroughly dispersed as described above. After that, ultraviolet light was irradiated for 1 hour using a low-pressure mercury lamp. The ultraviolet light irradiation was performed at a distance of approximately 15 cm from the bottom of the Erlenmeyer flask for 1 hour. Furthermore, the Erlenmeyer flask was then heated at 100 °C for 1 hour.

[0061] As a result of irradiating with ultraviolet light and heating for another hour, no color change was observed inside the Erlenmeyer flask, and there was virtually no odor generation, confirming that odor generation was suppressed. This indicates that by coating the titanium dioxide powder surface with an extremely thin cross-linked PEG of only a few nanometers, direct contact between the titanium dioxide crystal surface and squalane molecules was effectively blocked, thereby strongly suppressing the chemical reaction between the oxygen in the air dissolved in the squalane and the titanium dioxide.

[0062] This result represents a completely new finding and provides a novel method for effectively inhibiting photochemical reactions on solid surfaces using a very simple approach. It goes without saying that, by using the embodiments of the present invention, it is possible to construct crosslinked PEG films on solid powders such as polymer particles and zinc oxide particles.

[0063] (ii) Dispersibility of PEG-crosslinked titanium dioxide powder (PEG-crosslinked titanium dioxide particles) in pure water In the embodiment of the present invention, when the PEG crosslinked titanium oxide powder (PEG crosslinked titanium oxide particles) obtained was ultrasonically dispersed in pure water, it maintained its dispersion even after one week.

[0064] In contrast, when a certain amount of raw titanium oxide powder, which is not coated with cross-linked PEG, was ultrasonically dispersed in pure water, most of it settled and accumulated after just one day. Thus, the PEG-crosslinked titanium oxide powder (PEG-crosslinked titanium oxide particles) obtained by the embodiments of the present invention is thought to have improved dispersibility in water because the hydrophilicity of the PEG-crosslinked thin film on its surface greatly contributed to this improvement.

[0065] (e) Measurement of ultraviolet absorption capacity Figure 4 is a characteristic diagram showing the results of measuring the ultraviolet absorption capacity of a solid surface thin film using an atmospheric pressure plasma-based solid surface thin film formation method according to an embodiment of the present invention, with wavelength [nm] on the horizontal axis and absorbance on the vertical axis.

[0066] First, regarding sunlight, the ultraviolet (UV) region of sunlight that has adverse effects on human skin is classified into UV-A (400-320 nm), UV-B (320-290 nm), and UV-C (below 290 nm) based on their wavelength range. Of these, the UV-C region is almost entirely lost in the ozone layer of the atmosphere, so the wavelength ranges that should be reduced for use in cosmetics are effectively the UV-A and UV-B regions.

[0067] A small amount of titanium oxide powder coated with crosslinked PEG obtained according to an embodiment of the present invention was taken and diluted and dispersed in pure water to 0.0004%. The solution was placed in a quartz cuvette for spectrometers (10 mm × 10 mm × 45 mm), and the absorbance of ultraviolet light was measured using a Shimadzu UV-Vis. spectrometer (UV-1850). The measurement results are shown in Figure 4.

[0068] As shown in Figure 4, the ultraviolet absorption of the crosslinked PEG-coated titanium oxide powder obtained in the embodiment of the present invention starts in the UV-C region at 200 nm, with the maximum absorption peak occurring around 380 nm in the UV-B region. Furthermore, the absorbance in the UV-A region gradually decreases towards longer wavelengths.

[0069] Generally, UV-B rays are considered to be the strongest contributor to sunburn, and since UV protection has focused on the SPF (Special Protection Factor) in this region, the fact that the maximum absorption point of the cross-linked PEG-coated titanium oxide powder obtained in the embodiment of the present invention is in this region is considered the most desirable characteristic.

[0070] On the other hand, the UV-A region has only received supplementary evaluations (such as PA++). However, UV-A ultraviolet rays, which are said to have several times the energy of UV-B rays in sunlight, penetrate deep into the skin and are involved in skin aging and the occurrence of photosensitivity, so the ability to block UV-A rays has become increasingly important in recent years. For this reason, the crosslinked PEG-coated titanium oxide powder obtained in the embodiment of the present invention exhibits a gradual decrease in absorbance in the UV-A region, which can be said to be a desirable characteristic as an ultraviolet protection property.

[0071] (h) Regarding the efficacy as a cosmetic additive When the cross-linked PEG-coated titanium dioxide powder obtained in the embodiment of the present invention was applied very thinly directly to the skin, such as the back of the hand, the PEG made direct contact with the skin, resulting in a significantly smoother and softer feel compared to untreated titanium dioxide, and also exhibiting superior spreadability on the skin. This is one of the reasons why the cross-linked PEG-coated titanium dioxide powder obtained in the embodiment of the present invention is highly regarded by cosmetics experts.

[0072] (T) Summary The titanium dioxide powder (particles) obtained by PEG plasma crosslinking according to the embodiments of the present invention can effectively lose the photo-oxidation catalytic properties of titanium dioxide. This appears to be a completely new finding. Furthermore, the titanium dioxide powder (particles) obtained by PEG plasma crosslinking according to the embodiments of the present invention can be used to easily obtain an ultraviolet protection film.

[0073] Furthermore, the titanium oxide powder (particles) obtained by PEG plasma crosslinking according to the embodiments of the present invention is industrially very advantageous because it allows for the creation of denser, ultrathin films that are insoluble in solvents such as alcohol and water in a short time, compared to silane coupling and the like.

[0074] In addition, the method for forming a thin film on a solid surface using atmospheric pressure plasma according to an embodiment of the present invention has the following advantages. • It is possible to form a thin film on a solid surface that is physically and chemically strong and insoluble in solvents. • Thin films can be formed on solid surfaces in a short time. • The process is simple and manufacturing costs can be reduced. • When forming a thin film that is physically and chemically strong and insoluble in solvents on a solid surface, no residue is generated. • Manufacturing costs can also be reduced.

[0075] <Other Modes and Examples for Carrying Out the Invention> Next, other embodiments and examples for carrying out the present invention will be described. Other embodiments and examples for carrying out the present invention are characterized in that PEG plasma crosslinking can be performed on a solid surface even when the solid surface cannot adsorb or coat PEG. The reason why PEG is not adsorbed or coated on the solid surface is that the solid is hydrophobic. Therefore, other embodiments and examples for carrying out the present invention are characterized in that the hydrophobicity of the solid is eliminated, and otherwise they are the same as the embodiments and examples for carrying out the present invention described above.

[0076] Here, we will use polyethylene particles (PE particles, sometimes called PE powder) as an example of a hydrophobic solid. PE particles are strongly hydrophobic. Therefore, even if you try to adsorb or coat PEG onto the surface of PE particles, they will hardly adsorb any PEG, and coating is not possible.

[0077] In order to make the surface of such PE particles hydrophilic, in other embodiments and other examples for carrying out the present invention, the hydrophobic surface of the PE particles is exposed to an atmospheric pressure plasma of an oxygen-containing noble gas (pretreatment step). The atmospheric pressure plasma used here can be realized, for example, by introducing helium gas and oxygen gas into an atmospheric pressure plasma apparatus 1, as shown in Figure 2, and causing a plasma discharge in the discharge space.

[0078] This atmospheric pressure plasma device 1 is used, and a predetermined amount of PE particles (or PE powder) is introduced into its cylindrical body 3.

[0079] Next, by operating the atmospheric pressure plasma apparatus 1 under the following discharge conditions, the PE particles (or PE powder) can be exposed to the atmospheric pressure plasma. The discharge conditions for the atmospheric pressure plasma device 1 were as follows: The gases used were 3 [SLM] of helium (He) and 15-20 [SCCM] of oxygen (O2). The power applied between electrodes 4 and 5 of the atmospheric pressure plasma device 1 was 300 [W], and the discharge time was 20 [minutes]. For the PE particles, 30 g of polyethylene PE fine particles (Mipelon 10 [μmφ] manufactured by Sumitomo Chemical Co., Ltd.) were used. For the PEG, low molecular weight PEG1000 manufactured by Kanto Chemical Co., Ltd. was used.

[0080] In such an atmospheric pressure plasma apparatus 1, under the discharge conditions described above, the hydrophobic surface of the PE particles (or PE powder) is oxidized by oxygen atoms generated in the atmospheric pressure plasma, and then the oxidized PE particles (or PE powder) are removed from the cylindrical body 3. The removed PE particles will have an oxidized surface and will be hydrophilic. To confirm whether the surface of the PE particles after discharge treatment is hydrophilic, we will compare it with the properties of the raw material PE particles before atmospheric pressure plasma treatment.

[0081] First, when the raw PE particles before discharge treatment were placed in a container filled with pure water and ultrasonic waves were applied to the container for a predetermined time, the state of the PE particles was observed. The PE particles could not be dispersed at all in the pure water and floated on the surface. This is thought to be because the raw PE particles are water-repellent (hydrophobic). In this state, it is clear that hydrophilic PEG cannot be adsorbed or coated onto the surface of the PE particles.

[0082] In contrast, in this pretreatment process, the PE particles, after being exposed to atmospheric pressure plasma for discharge oxidation treatment, are completely dispersed in a container filled with pure water when placed in the container. This suggests that the surface of the PE particles has become hydrophilic. Through this treatment, the surface of the PE particles was made suitable for adsorption of PEG thin films.

[0083] [Adsorption process (1st process)] To adsorb PEG onto the surface of PE particles, a liquid solution of PEG dissolved in ethanol was used. Two weight concentrations of the PEG solution were used: a 10% solution and a 2% solution. The adsorption time for adsorbing PEG onto the surface of the PE particles was set to 30 minutes. After adsorbing PEG onto the surface of the PE particles, the particles were filtered through filter paper and vacuum-dried. In this embodiment, the PE particles, after adsorbing PEG, were aggregated, so they were lightly pressed after drying to form a powder. In a 10% weight solution of low molecular weight PEG1000, the thickness of the adhesion film on the surface of the PEG particles after drying was estimated to be approximately 1 μm based on the measurement of the mass change before and after adsorption.

[0084] [Plasma Crosslinking Process (Second Process)] The PE particles obtained in the adsorption step (first step) by adsorbing PEG onto the surface of the PE particles were returned to the rotating cylinder 31 of the cylindrical body 3 of the atmospheric pressure plasma apparatus 1 and subjected to plasma treatment with He gas only. The operating conditions for atmospheric pressure plasma device 1 were a discharge power value of 232 [W] and a processing time of 20 [minutes]. The plasma-treated PE particles, extracted from the rotating cylinder 31 of the cylindrical body 3 of the atmospheric pressure plasma apparatus 1, remained nearly white, with a slight milky white tint, even when adsorbed at weight concentrations of 10% and 2%. The surface texture was relatively soft and felt moister compared to commercially available PE powder raw materials.

[0085] [Wettability evaluation] We will conduct wettability tests on both the two types of PE particles after plasma treatment and the PE particles that have undergone plasma oxidation treatment followed by only 10% PEG adsorption, using the aforementioned "wettability evaluation method using the capillary rise method." The results are shown in Figures 5 to 7. Here, Figure 5 is a characteristic diagram illustrating the wettability evaluation when PEG is plasma-treated after adsorption of 10% PEG in a solid surface thin film formation method using atmospheric pressure plasma according to another embodiment of the present invention, with the horizontal axis representing immersion time t and the vertical axis representing "l squared (l) 2 These are derived from the phrases "(to be written as)" respectively.

[0086] As can be seen from Figure 5, the slope of the graph (l 2 / t) is 7.0 × 10 -7 (10 to the power of -7)m 2 s -1 This indicates that it has high hydrophilicity. The value of this slope is the same as the value of cross-linked PEG-coated titanium dioxide (6.9 × 10) in Figure 3. -7 )m 2 s -1 This closely matches the results, suggesting that the hydrophilicity of the PEG coated on the surface is evident regardless of the type of uncoated material.

[0087] Figure 6 is a characteristic diagram illustrating the wettability evaluation when PE is plasma-treated after 2% adsorption of PEG in a solid surface thin film formation method using atmospheric pressure plasma according to another embodiment of the present invention, with the horizontal axis representing the immersion time t and the vertical axis representing "l squared".

[0088] As can be seen from Figure 6, the slope of the graph (l 2 / t) is 9.6 × 10 -7 (10 to the power of -7)m 2 s -1 As can be seen, it can be confirmed that it has high hydrophilicity, similar to what is shown in Figure 5.

[0089] Figure 7 is a characteristic diagram illustrating the wettability evaluation of PE simply by adsorbing PEG in a 10% solution, in a case where the solid surface thin film formation method using atmospheric pressure plasma according to other embodiments of the present invention is not applied, with the horizontal axis representing the immersion time t and the vertical axis representing "l squared (l) 2 These are the parts taken from each of the following: As can be seen from Figure 7, the slope of each graph of PE particles that were not plasma crosslinked after adsorption to PE particles in PEG10[%] solution (l 2 / t) are each 1.9 × 10 -7 (10 to the power of -7)m 2 s -1 As shown in Figure 7, the slope decreases significantly. Furthermore, as shown in Figure 7, the process stagnates after 1200 seconds. This is thought to be because the PEG film dissolves in the benzyl alcohol of the immersion solution, increasing the viscosity of the immersion solution as it rises, causing the rise to stop.

[0090] Furthermore, it has been found that PE particles that have strong hydrophobicity are oxidized by plasma treatment in the pretreatment step, and are even more hydrophilic than PE particles that have been crosslinked in the plasma crosslinking step (second step). However, as the peroxide on the surface evaporates and is lost over time, the hydrophilicity is gradually lost.

[0091] [Measurement of surface molecular structure using FTIR-ATR] The surface molecular structure of plasma-crosslinked PE particles obtained by a solid surface thin film formation method using atmospheric pressure plasma according to another embodiment of the present invention will be measured, and the surface molecular structure of PE particles without plasma crosslinking will be measured. By comparing the measurement results, it will be confirmed that the surface of the plasma-crosslinked PE particles has the expected performance.

[0092] This FTIR-ATR method for measuring surface molecular structure utilizes total internal reflection, in which light rays reflected internally from the surface of the transmitting medium pass slightly beyond the mirror interface into the sample as part of the reflection process, and then return to the transmitting medium. If a material with a lower refractive index than the transmitting medium is placed in contact with the reflective surface, light will pass through the material to a depth of several micrometers, producing an absorption spectrum. This method allows for obtaining multiple internal reflections on the sample surface. Measurements were performed using JASCO's FT / IR-4000typeA and ATRPRO410-S.

[0093] Figure 8 is a characteristic diagram illustrating the results of measuring the surface molecular structure of a solid formed using an atmospheric pressure plasma-based solid surface thin film formation method according to another embodiment of the present invention, and the surface molecular structure of the solid at each step before plasma crosslinking, using the above measuring instrument. The horizontal axis represents wavenumber [ / cm] and the vertical axis represents absorbance [au].

[0094] Furthermore, in Figure 8, (a) shows the measurement results of the surface molecular structure of completely untreated PE particles, (b) shows the measurement results of the surface molecular structure of PE particles that have only been oxidized in the pretreatment step, (c) shows the measurement results of the surface molecular structure of PE particles that have only been coated (adsorbed) with PEG1000 [weight%] after being oxidized in the pretreatment step, and (d) shows the measurement results of the surface molecular structure of PE particles obtained by crosslinking the PE particles in (c) in the plasma crosslinking step. In Figure 8, the results of assigning each peak are shown below. ·CH stretching vibration i) Antisymmetric stretching vibration (νas CH2): 2915 [ / cm] ii) Symmetrical stretching vibration (νas CH2): 2850 [ / cm] ·C=O stretching vibration: 1704[ / cm] ·CH2 angle vibration: 1469[ / cm] • The absorption band for the scissor vibration (δsCH2) in the hydrocarbon spectrum occurs at a nearly constant position around 1465 [ / cm]. • COC antisymmetric stretching vibration (1 1 1 4 [ / cm]) The characteristic absorption of ethers in the infrared region is associated with the stretching vibrations of the COC system. In the spectra of aliphatic ethers, the most characteristic absorption is a single absorption band in the region of 1085–1150 [ / cm] due to antisymmetric stretching of the COC system, which usually occurs around 1125 [ / cm].

[0095] We will consider this based on the points mentioned above. The results of the FTIR-ATR measurements for untreated PE particles (Figure 8(a)), oxidized PE particles (Figure 8(b)), PE particles with PEG thin film formation (Figure 8(c)), and PE particles that were crosslinked after PEG thin film formation (Figure 8(d)) are as follows.

[0096] (i) For the untreated PE particles in Figure 8(a), CH stretching vibrations and CH bending vibrations, which are characteristic of PE, are observed. (ii) For the oxidized PE particles in Figure 8(b), CH stretching vibrations and CH bending vibrations are observed. A slight increase in C=O stretching vibrations is also observed. (iii) CH stretching vibration, CH bending vibration, and CO stretching vibration can be observed in the PEG thin film-forming PE particles in Figure 8(c). The formation of the PEG thin film results in a peak in the COC antisymmetric stretching vibration that is not seen in figures (a) and (b). Considering that the structure of PEG is H(OCH2CH2)nOH, this indicates that a thin film of PEG was formed on the surface. (iv) In the PE particles that were crosslinked after forming a PEG thin film in Figure 8(d), CH stretching vibrations, CH bending vibrations, and CO stretching vibrations are observed. By forming a PEG thin film and crosslinking it, the splitting of the CH stretching vibration peak group disappeared, and the shape of the peak group broadened. This indicates that the vibrational structure became more complex as the crosslinking reaction progressed and the molecular chains inside the PEG became entangled. In addition, the peak of the COC antisymmetric stretching vibration became smaller compared to the PEG thin film formed PE particles in Figure 8(c). This is thought to be because when crosslinking was performed with He plasma, part of the PEG structure on the surface was ablated and decomposed by the plasma energy.

[0097] Next, as a comparison, we measured the surface molecular structure of PEG20000 (molecular weight 20000), a polymer insoluble in ethanol, using FTIR-ATR.

[0098] Figure 9 is a characteristic diagram showing the results of measuring the surface molecular structure of PEG, a polymer insoluble in ethanol and the like, by FTIR-ATR as a comparative reference in other embodiments and examples of the present invention, with the horizontal axis representing wavenumber [ / cm] and the vertical axis representing absorbance [au].

[0099] In Figure 9, two characteristic peaks of the PEG structure are observed: (1) CH stretching vibration (2888 [ / cm]) and (4) COC antisymmetric stretching (1103 [ / cm]). Here again, the COC antisymmetric stretching vibration is observed as a characteristic peak of PEG, confirming that PEG was adsorbed onto the PE particles in the PE particles with PEG1000 adsorbed, as shown in Figure 8(c).

[0100] From the above, we can conclude the following. PEG (polyethylene glycol), a type of solid polymer, is known to have extremely low physiological effects on the human body, making it suitable for implantation in the body. However, PE particles (powder) intended for use in cosmetics and other products have high water repellency, making it difficult for them to adsorb highly hydrophilic PEG.

[0101] Therefore, in other embodiments and examples of the present invention, PE particles are plasma-oxidized in a mixed gas of helium and oxygen (He / O2). The surface of the PE particles treated in this way is covered with peroxide immediately after the plasma oxidation treatment, so PEG can be easily adsorbed. However, since the peroxide gradually oxidizes and evaporates in the air over time and is lost from the surface, the hydrophilicity decreases over time.

[0102] Furthermore, in other embodiments and examples of the present invention, PEG is adsorbed onto the surface of PE particles treated with oxidizing plasma in a PEG-ethanol solution, and then the PE particles with the PEG adsorbed onto their surface are exposed to He plasma to promote the crosslinking reaction of PEG on the surface of the PE particles, thereby forming a crosslinked film that is insoluble in ethanol or benzyl alcohol. The PEG-crosslinked PE particles (powder) retain strong hydrophilicity, have high transparency, exhibit a unique milky white color, and have a moist and smooth feel. While the hydrophilicity of oxidized PE particles (powder) is temporary, the surface of PEG-crosslinked PE particles (powder) according to other embodiments and examples of the present invention can retain strong hydrophilicity semi-permanently, making them stably usable in cosmetics and the like. The method for forming a solid surface thin film using atmospheric pressure plasma according to other embodiments and examples of the present invention has the following advantages. • It is possible to form a thin film on a solid surface that is physically and chemically strong and insoluble in solvents. • Thin films can be formed on solid surfaces in a short time. • The process is simple and manufacturing costs can be reduced. • When forming a thin film that is physically and chemically strong and insoluble in solvents on a solid surface, no residue is generated. • Manufacturing costs can also be reduced.

[0103] In this invention, titanium dioxide (TiO2) particles were used as an example of a hydrophilic solid, and polyethylene (PE) particles were used as an example of a hydrophobic solid. However, it goes without saying that the invention is not limited to these examples, and PEG plasma-crosslinked films can be formed on solid surfaces. [Explanation of Symbols]

[0104] 1. Atmospheric pressure plasma device 2 rotation axes 3 cylinder 4. First electrode 5. Second electrode 6. Gas introduction means 7. Gas discharge means 8 Power supply 21 Left center axis 22 Right center axis 23 Resin joints 24,25 Center bearing 31. Glass Rotating Cylinder 32,33 Polycarbonate flange 34,35 Wilson Seal 61 T-joint 62 Discharge port 71 T-joint 72 Inlet

Claims

1. A method for forming a thin film on a solid surface using atmospheric pressure plasma, wherein a thin film that is physically and chemically strong and insoluble in solvents is formed on the solid surface, A step of adsorbing or coating polyethylene glycol onto the entire solid surface, A process of forming a thin film of polyethylene glycol on a solid surface to which polyethylene glycol has been adsorbed or coated by irradiating a predetermined rare gas atmospheric pressure plasma to cause a plasma crosslinking reaction of polyethylene glycol on the solid surface. A method for forming a thin film on a solid surface using atmospheric pressure plasma equipped with the following features.

2. The method for forming a thin film on a solid surface using atmospheric pressure plasma according to claim 1, characterized in that the noble gas is helium gas, argon gas, or a mixture thereof.

3. A method for forming a thin film on a solid surface using atmospheric pressure plasma, which enables the adsorption or application of polyethylene glycol to the entire surface of a hydrophobic solid even when polyethylene glycol cannot be adsorbed or applied to the entire surface of the solid, and forms a thin film on the solid surface that is physically and chemically strong and insoluble in solvents, A process of oxidizing the surface of a hydrophobic solid by irradiating it with a mixed gas plasma of a rare gas and oxygen gas, A step of adsorbing or coating polyethylene glycol onto the entire oxidized solid surface, A process to obtain a polyethylene glycol film on a solid surface to which polyethylene glycol has been adsorbed or coated, by irradiating a predetermined rare gas atmospheric pressure plasma to cause a plasma crosslinking reaction of polyethylene glycol on the solid surface. A method for forming a thin film on a solid surface using atmospheric pressure plasma equipped with the following features.

4. The method for forming a thin film on a solid surface using atmospheric pressure plasma according to claim 3, characterized in that the noble gas is helium gas, argon gas, or a mixture thereof.

5. An atmospheric pressure plasma apparatus used in a solid surface thin film formation method for forming a thin film on a solid surface that is physically and chemically strong and insoluble in solvents using atmospheric pressure plasma, A cylindrical body that can rotate around a horizontally positioned axis of rotation, A first electrode provided on the outer circumference of the cylindrical body, A second electrode of a predetermined shape is provided inside the cylindrical body, An introduction means for introducing atmospheric pressure noble gas into the cylindrical body, A discharge means for discharging gas from inside the cylinder, A power supply device that supplies high-frequency high-voltage voltage to the first electrode and the second electrode. An atmospheric pressure plasma device characterized by being equipped with the following features.

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