Method of Pretreatment for Nail Coating, Method of Decorating Nail and Plasma Irradiation Device

This non-provisional application claims the benefit under 35 U.S.C. § 119 (a) to Patent Application No. 2024-058091, filed in Japan on Mar. 29, 2024, and Patent Application No. 2025-032114, filed in Japan on Feb. 28, 2025, which are hereby expressly incorporated by reference into the present application.

The present invention relates to a method of pretreatment for nail coating, a method of decorating a nail, and a plasma irradiation device.

Nail coating, such as nail art including nail polish and gel nail polish, is performed on the nails, for the purpose of decorating and protecting nails. A lacquer (nail polish), an acrylic resin, an ultraviolet-curable resin or the like is used for nail coating. There are cases where a stone is allowed to adhere to the nail polish, the acrylic resin or the ultraviolet-curable resin.

Before performing nail coating, polishing (sanding) nails to roughen the nail surface, or wiping nails with an organic solvent such as acetone for removing dirt or grease, has been performed, in order to improve the adhesion of lacquer (nail polish), an acrylic resin or an energy ray-curable resin. However, polishing nails causes whitening and a decrease in the strength of the nails. Further, the use of an organic solvent may cause the percutaneous absorption of the organic solvent or the discoloration of the nails.

There is a surface treatment device for a nail, including a plasma generation source for performing a pretreatment of the nail surface by non-thermal plasma, in order to improve the adhesion of an energy ray-curable nail coating agent to the nail (Patent Document 1). However, the gas type of the plasma, in the plasma generation source disclosed in Patent Document 1, is not particularly described.

Further, there is a method in which the plasma of a gas containing argon as a main component and containing krypton, hydrogen or nitrous oxide is used on a nail, for the purpose of cosmetic bleaching of the nail (Patent Document 2). However, Patent Document 2 does not disclose gas types other than the gas containing argon as a main component, and in addition, the irradiation of plasma is performed for the bleaching of the nail, and not as a pretreatment step for nail coating.

An object of the present invention is to provide a method of pretreatment for nail coating, a method of decorating a nail and a plasma irradiation device, which provide an excellent effect in the adhesion to a nail coating by performing an appropriate plasma treatment, at the time of performing nail coating.

The present inventors have discovered that the above-described object can be achieved when the gas to be used in the generation of plasma is nitrogen gas, oxygen gas and/or carbon dioxide gas, thereby arriving at the present invention.

Specifically, the present invention includes the following [] to [].

[1] A method of pretreatment for nail coating, the method including irradiating plasma to a nail or a nail coating liquid applied to the nail, before or during the step of applying the nail coating liquid to the nail,

The method of pretreatment for nail coating, the method of decorating a nail and the plasma irradiation device, according to the present invention, provide effects such as an excellent adhesion to a nail coating, by performing an appropriate plasma treatment.

Embodiments of the method of pretreatment for nail coating, the method of decorating a nail and the plasma irradiation device will be described below more specifically.

The method of pretreatment for nail coating according to the present embodiment is a method of pretreatment for nail coating, the method including irradiating plasma to a nail or a nail coating liquid applied to the nail, before or during the step of applying the nail coating liquid to the nail, wherein the gas used for generating the plasma is one or more gases selected from the group consisting of nitrogen gas, oxygen gas and carbon dioxide gas.

The plasma irradiation is performed as a pretreatment for the application of the nail coating liquid. The “nail coating liquid” as used herein refers to a liquid to be applied to a fingernail of a human hand or a toenail of a human foot. Specifically, the definition of the nail coating liquid includes a liquid for a base coat, a lacquer liquid referred to as “nail polish” and a liquid for a top coat. The definition of the nail coating liquid also includes liquids for the protection and reinforcement of nails, such as those for sports, and those for the elderly and musical instrument players, in addition to those for decoration. Materials to be used for nail coating are not particularly limited, and examples thereof include resins such as acrylic resins, urethane resins, and nitrocellulose resins. Further, known curing methods such as curing by drying and curing by an energy ray such as UV can also be used for nail coating.

The plasma is irradiated to a nail before the application of a liquid for a base coat, by a plasma irradiation device. Further, the plasma can be irradiated to a base coat formed by drying a base coating liquid applied to the nail. In addition, the plasma can be irradiated to a nail polish formed by drying a lacquer liquid applied to the nail. It is preferred to use an irradiation device based on the principle of non-thermal equilibrium plasma, referred to as low-temperature plasma or atmospheric pressure plasma, as the plasma irradiation device. In such a plasma irradiation device, plasma is generated by applying a voltage to the gas continuously supplied to the device.

One type of gas selected from the group consisting of nitrogen gas, oxygen gas and carbon dioxide gas is used, as the gas to be supplied to the plasma irradiation device to generate plasma. These gases may be used singly, or as a mixture of a plurality of gases. For example, it is possible to use a simulated air gas containing about 78% nitrogen gas and about 21% oxygen gas, with the balance being carbon dioxide gas and/or an impurity gas(es). It is also possible to use air. Further, it is possible to use a gas containing: one gas selected from the group consisting of nitrogen gas, oxygen gas and carbon dioxide gas; and water vapor.

The effects to be described below, such as an adhesive force to a nail coating, can be expected, by the plasma irradiation using one gas selected from the group consisting of nitrogen gas, oxygen gas, and carbon dioxide gas.

Performing the pretreatment of irradiating plasma to a nail using the above-described gas improves the adhesion of the nail coating liquid to be applied to the nail after the plasma irradiation. This eliminates the need for polishing the nail before the application of the nail coating liquid, which has been conventionally performed for the purpose of improving the adhesion. Therefore, it is possible to avoid a decrease in the thickness of the nail due to polishing, making it possible to prevent the whitened appearance and a decrease in the strength of the nail. Nail thickness affects the moisture content of nails, and a lower nail thickness makes the nails more susceptible to cracking and the like. However, the present embodiment requires no polishing before the application of the nail coating liquid, and thus it is possible to prevent nail cracking and the like, and helps to maintain healthy nails. Since the moisture content of nails tends to decrease in the elderly, in particular, the fact that polishing can be avoided as much as possible has a large effect particularly for the elderly.

Moreover, the improvement in the adhesion of the nail coating liquid enables the number of reapplications to be reduced.

The reason why the plasma irradiation improves adhesion is thought to be because adhesive functional groups are generated on the nail surface irradiated with the plasma.

Further, during the step of applying any of the coating liquids in general, including a base coat, a nail polish and a top coat, the adhesion of the nail polish to the base coat applied to a nail is expected to improve, by irradiating plasma to the base coat. In addition, the adhesion of the top coat to the nail polish is expected to improve, by irradiating plasma to the nail polish applied to the nail.

As described above, performing the pretreatment of irradiating plasma to a nail using the above-described gas eliminates the need for polishing the nail before the application of the nail coating liquid, and accordingly, the thickness of the nail does not decrease, making it possible to prevent nail cracking. Further, the occurrence of nail cracking can be prevented, because any of the nail coating liquids for the protection and reinforcement of nails, such as those for sports, and those for the elderly and musical instrument players, can be applied thinly without uneven spots per a single application. In addition, by irradiating plasma to the surface of the underlying layer when such a nail coating liquid is applied in layers, the adhesion between coating liquid layers can be expected to improve, making it possible to easily reinforce the nail, and to prevent the nail from cracking and scratching.

Performing the pretreatment of irradiating plasma to a nail using the above-described gas makes it possible to clean the surface of the nail by a dry-cleaning effect. This eliminates the need for a degreasing treatment of wiping the nail surface with a nail polish remover or an organic solvent such as acetone, which has been conventionally performed for the purpose of improving the adhesion. Therefore, it is possible to reduce the percutaneous absorption of the organic solvent, and to prevent the discoloration of the nail.

Performing the pretreatment of irradiating plasma to a nail using the above-described gas makes it possible to improve the wettability of the surface of the nail. This allows for reducing the uneven spots in the nail coating liquid to be applied. A beauty serum may be applied to the nail surface before the application of the nail coating liquid thereto. Uneven spots in the beauty serum can be reduced by pretreatment of plasma irradiation using the above-described gas. Therefore, it is possible to evenly apply the beauty serum and the nail coating liquid. Therefore, it is possible to reduce the treatment time for performing nail coating, such as nail art.

The reason why the wettability is improved by the plasma irradiation is thought to be because the surface free energy of the nail surface irradiated with the plasma increases.

Performing the pretreatment of irradiating plasma to a nail using the above-described gas makes it possible to eliminate bacteria attached to the surface of the nail. Performing the pretreatment of irradiating plasma makes it possible to decompose and remove dirt such as bacteria or oils and fats on the nail and the fingertip. Therefore, it can be expected to prevent bacterial infection and to prevent the occurrence of green nail and the like. Further, the treatment of nail coating can be performed under good hygiene. Furthermore, due to dry cleaning without using any surfactant or organic solvent, a physical burden is allowed to be smaller than that in the case of using a surfactant or an organic solvent.

There are cases where a beauty serum is applied to the nail surface before the application of the nail coating liquid thereto or after the removal of the nail coating liquid therefrom. Performing the pretreatment of irradiating plasma to a nail using the above-described gas before the application of the beauty serum makes it possible to promote the penetration of the beauty serum into the nail plate, lateral nail folds, nail grooves and the like. The moisture content of nails and skin is improved, by promoting the penetration of the beauty serum by the plasma irradiation. In other words, the moisture retention effect of the beauty serum is improved. A decrease in the moisture content of nails and skin may be one of the causes for the occurrence of cracks and fissures in the nails and the skin around the nails. That is, it can be expected to alleviate or to prevent the occurrence of cracks and fissures in the nails and the skin around the nails, and the like, by the plasma irradiation. The improvement in the moisture retention effect of the beauty serum can be expected to promote the action of the nail matrix which is a source of the healthy nail.

In both the cases of applying the nail coating liquid after application of the beauty serum and of applying the nail coating liquid without applying the beauty serum, performing the pretreatment of irradiating plasma using the above-described gas in advance makes it possible to enhance the effects of the beauty serum and the nail coating liquid to support nail care.

The effects described above work synergistically, making it possible to reduce the treatment time for performing nail coating, and to perform the application of the nail coating liquid that serves to maintain healthy nails and achieves a high adhesion, under good hygiene.

Furthermore, the healthy nail can be grown due to the above-described effects such as the improvement in adhesion, the prevention of nail cracking, the elimination of requirement of degreasing treatment, the improvement in wettability, the sterilization, and the penetration of the beauty serum. This offers a useful value to a person needing nail care. For example, in a sport athlete, a pitcher in baseball as a specific example, nail cracking affects play, and the defective nail leads to an injury. Therefore, the healthy nail can be grown for the purpose of reducing injuries affecting play, such as nail cracking.

Next, an embodiment of the method of decorating a nail will be described specifically.

The method of decorating a nail according to the present embodiment is a method of decorating a nail, the method including:

The “curable nail coating liquid” as used herein refers to a coating liquid which is cured by performing a curing treatment after the application, or by a polymerization reaction, among the liquids to be applied to a fingernail of a human hand or a toenail of a human foot. Such a curable nail coating liquid may be, for example, an energy ray-curable resin which is cured by the irradiation of an energy ray, such as a photocurable resin, particularly, an ultraviolet-curable (UV-curable) resin, and is referred to as “gel nail polish”. Further, the definition of the curable nail coating liquid includes an acrylic resin, a urethane resin, nitrocellulose and the like, which are used for attaching false nails and for nail sculpturing.

The step of irradiating plasma to the nail is performed, before the step of applying a curable nail coating liquid to the nail. It is also possible to irradiate plasma to the curable nail coating liquid which is applied to the nail and is before or after curing. It is preferred to use an irradiation device based on the principle of non-thermal equilibrium plasma, referred to as low-temperature plasma or atmospheric pressure plasma, as the plasma irradiation device for irradiating plasma. In such a plasma irradiation device, plasma is generated by applying a voltage to the gas continuously supplied to the device.

One type of gas selected from the group consisting of nitrogen gas, oxygen gas and carbon dioxide gas is used, as the gas to be supplied to the plasma irradiation device to generate plasma. These gases may be used singly, or as a mixture of a plurality of gases. For example, it is possible to use a simulated air gas containing about 78% nitrogen gas and about 21% oxygen gas, with the balance being carbon dioxide gas and/or an impurity gas(es). It is also possible to use air.

The effects to be described below can be obtained, by the plasma irradiation using one gas selected from the group consisting of nitrogen gas, oxygen gas and carbon dioxide gas.

Performing the plasma irradiation treatment on a nail using the above-described gas improves the adhesion of the curable nail coating liquid to be applied to the nail after the plasma irradiation. This eliminates the need for polishing the nail before the application of the curable nail coating liquid, which has been conventionally performed for the purpose of improving the adhesion. Therefore, it is possible to avoid a decrease in the thickness of the nail due to polishing, making it possible to prevent the whitened appearance and a decrease in the strength of the nail. The nail thickness affects the moisture content of nails, and a lower nail thickness makes the nails more susceptible to cracking and the like. However, the present embodiment requires no polishing before the application of the curable nail coating liquid, and thus it is possible to prevent nail cracking and the like, and helps to maintain healthy nails. Since the moisture content of nails tends to decrease in the elderly, in particular, the fact that polishing can be avoided has a large effect particularly for the elderly.

Moreover, the improvement in the adhesion of the nail coating liquid enables the number of reapplications to be reduced. The reason why the plasma irradiation improves adhesion is thought to be because adhesive functional groups are generated on the nail surface irradiated with the plasma.

In cases where the application and the curing of the curable nail coating liquid are performed repeatedly to decorate a nail, the adhesion of the curable nail coating liquid applied as the top coat to the curable nail coating liquid applied as the base coat is expected to improve, by irradiating plasma to the curable nail coating liquid which is applied to the nail and is before or after curing.

Performing the plasma irradiation treatment on a nail using the above-described gas makes it possible to clean the surface of the nail by a dry-cleaning effect. This eliminates the need for a degreasing treatment of wiping the nail surface with a nail polish remover or an organic solvent such as acetone, which has been conventionally performed for the purpose of improving the adhesion. Therefore, it is possible to reduce the percutaneous absorption of the organic solvent, and to prevent the discoloration of the nail.

Performing the plasma irradiation treatment on a nail using the above-described gas makes it possible to improve the wettability of the surface of the nail. This allows for reducing the uneven spots in the curable nail coating liquid to be applied. A beauty serum may be applied to the nail surface before the application of the nail coating liquid thereto. Uneven spots in the beauty serum can be reduced by performing the plasma irradiation treatment using the above-described gas. Therefore, it is possible to evenly apply the beauty serum and the nail coating liquid. Therefore, it is possible to reduce the treatment time for performing nail coating.

The reason why the wettability is improved by the plasma irradiation is thought to be because the surface free energy of the nail surface irradiated with the plasma increases.

As described above, performing the plasma irradiation treatment to a nail using the above-described gas eliminates the need for polishing the nail before the application of the nail coating liquid, and accordingly, the thickness of the nail does not decrease, making it possible to prevent nail cracking. Further, the occurrence of nail cracking can be prevented, because the nail coating liquid can be applied thinly without uneven spots per a single application. In addition, by irradiating plasma to the surface of the underlying layer when the nail coating liquid is applied in layers, a good adhesion between coating liquid layers can be expected, making it possible to reinforce the nail, and to prevent the nail from cracking and scratching.

Performing the plasma irradiation treatment to a nail using the above-described gas makes it possible to eliminate bacteria attached to the surface of the nail. Performing the plasma irradiation makes it possible to decompose and remove dirt such as bacteria or oils and fats on the nail and the fingertip. Therefore, it can be expected to prevent bacterial infection and to prevent the occurrence of green nail and the like. Further, the treatment of nail coating can be performed under good hygiene. Furthermore, due to dry cleaning without using any surfactant or organic solvent, a physical burden is allowed to be smaller than that in the case of using a surfactant or an organic solvent.

There are cases where a beauty serum is applied to the nail surface before the application of the nail coating liquid thereto or after the removal of the nail coating liquid therefrom. Performing the plasma irradiation treatment to a nail using the above-described gas before the application of the beauty serum makes it possible to promote the penetration of the beauty serum into the nail plate, lateral nail folds, nail grooves and the like. The moisture content of nails and skin is improved, by promoting the penetration of the beauty serum by the plasma irradiation. In other words, the moisture retention effect of the beauty serum is improved. A decrease in the moisture content of nails and skin may be one of the causes for the occurrence of cracks and fissures in the nails and the skin around the nails. That is, it can be expected to alleviate or to prevent the occurrence of cracks and fissures in the nails and the skin around the nails, and the like, by the plasma irradiation. The improvement in the moisture retention effect of the beauty serum can be expected to promote the action of the nail matrix which is a source of the healthy nail.

In both the cases of applying the nail coating liquid after application of the beauty serum and of applying the nail coating liquid without applying the beauty serum, performing the plasma irradiation treatment using the above-described gas in advance makes it possible to enhance the effects of the beauty serum and the nail coating liquid to support nail care.

The effects described above work synergistically, making it possible to reduce the treatment time for performing nail coating, and to perform the application of the curable nail coating liquid that serves to maintain healthy nails and achieves a high adhesion, under good hygiene.

Furthermore, the healthy nail can be grown due to the above-described effects such as the improvement in adhesion, the prevention of nail cracking, the elimination of requirement of degreasing treatment, the improvement in wettability, the sterilization, and the penetration of the beauty serum. This offers a useful value to a person needing nail care. For example, in a sport athlete, a pitcher in baseball as a specific example, nail cracking affects play, and the defective nail leads to an injury. Therefore, the healthy nail can be grown for the purpose of reducing injuries affecting play, such as nail cracking.

Next, another embodiment of the method of decorating a nail will be described specifically.