Hair dyeing method

Abstract

The present invention provides a hair dyeing method which comprises a step 1 and a step 2 in this order, and does not comprise a step for rinsing hair between the step 1 and the step 2, and comprises a step for rinsing hair after the step 2: step 1: a step for applying an agent A to hair, the agent A having a pH value of 8-11 and containing the following components (a1) and (a2): (a1) a compound represented by general formula (1) or a salt thereof; the dashed line represents the presence or absence of a pi bond, R1 represents a hydroxyl group or an acetoxy group, R2 represents a hydrogen atom or-COOR (R represents a hydrogen atom, a methyl group or an ethyl group), and R3 represents a hydrogen atom, an acetyl group, a methyl group or an ethyl group); (a2) an alkaline agent; step 2: A step for applying agent B to hair, said agent B containing the following component (b): (b) alkali metal salt or alkaline earth metal salt selected from among organic acid salts or inorganic salts having 6 or less carbon atoms # imgabs0 #

Description

Technical Field

[0001] The present invention relates to a hair dyeing method. Background Art

[0002] Conventionally, air-oxidized hair dyes using 5,6-dihydroxyindole, 5,6-dihydroxyindoline, or derivatives thereof as melanin precursors are known as hair dyes for gray hair. These melanin precursors can dye hair without the use of an oxidizing agent, and therefore, when used in hair dyes, they minimize damage to keratinous fibers and offer high convenience as dyes for hair dyes.

[0003] For example, Japanese Patent Application Laid-Open No. 63-170309 (Patent Document 1) discloses a method for dyeing keratinous fibers using an indole derivative in combination with an iodide, with the goal of dyeing human keratinous fibers using an indole derivative in a manner that allows for a strong color to be obtained with a very short exposure time without deteriorating the hair.

[0004] Japanese Patent Application Laid-Open No. 1-319413 (Patent Document 2) discloses a method for dyeing hair by sequentially treating with a metal ion-containing composition and a dye composition containing 5,6-dihydroxyindole-2-carboxylic acid, with the goal of obtaining a dyed product having a natural luster and glossiness, no smearing, and exhibiting durability against light and moisture, thereby being both light-stable and shampoo-stable.

[0005] Japanese Patent Publication No. 8-505155 (Patent Document 3) discloses a method for dyeing keratinous fibers, particularly human hair, using 5,6-dihydroxyindole and / or its derivatives as dyeing agents, with the goal of improving light resistance and achieving dyeing that exhibits good resistance to repeated washing and perspiration. This method uses a simple salt or polymer of inorganic or organic magnesium that is soluble in a medium. Summary of the Invention

[0006] The present invention relates to the following [1].

[0007] [1] A hair dyeing method comprising the following steps 1 and 2 in sequence, wherein there is no step of rinsing the hair between the steps 1 and 2, and there is a step of rinsing the hair after the step 2.

[0008] Step 1: Applying Agent A to the hair.

[0009] The pH value of the agent A is 8-11 and contains the following components (a1) and (a2):

[0010] (a1) a compound represented by the following general formula (1) or a salt thereof,

[0011]

[0012] (wherein, the dotted line indicates the presence or absence of a π bond; R 1 represents a hydroxyl group or an acetoxy group; R 2 represents a hydrogen atom, or -COOR (R is a hydrogen atom, a methyl group or an ethyl group); R 3 represents a hydrogen atom, an acetyl group, a methyl group or an ethyl group;)

[0013] (a2) alkali agent;

[0014] Step 2: Applying Agent B to the hair.

[0015] The B agent contains the following component (b):

[0016] (b) an alkali metal salt or alkaline earth metal salt selected from organic acid salts or inorganic salts having 6 or less carbon atoms. DETAILED DESCRIPTION

[0017] However, the method described in Patent Document 1 generates iodine through the reaction between iodide and hydrogen peroxide, which in turn develops a brownish color. Since hydrogen peroxide is required, this method poses a problem of hair damage. The method described in Patent Document 2, because hair is treated with a composition containing transition metal ions, can exhibit toxicity or physiological activity due to interactions with bioorganic molecules, and this can also affect the dyed hair after treatment. Furthermore, the ion concentration in water varies by region, and rinsing hair treated with a melanin precursor using water with varying ion concentrations can affect hair dyeability. Therefore, the method described in Patent Document 3 has room for improvement in terms of enhancing hair dyeability.

[0018] The present invention relates to a hair dyeing method that can achieve stable hair dyeing performance of a melanin precursor without being damaged by oxidation through a simple process, and further improve the hair dyeing performance.

[0019] The present inventors have discovered that the above-mentioned problems can be solved by a hair dyeing method comprising: step 1 of applying to the hair an agent A containing a predetermined melanin precursor and an alkaline agent and having a pH value within a specific range; and step 2 of applying to the hair an agent B containing a specific alkali metal salt or alkaline earth metal salt; wherein the method does not include a hair rinsing step between steps 1 and 2, but includes a hair rinsing step after step 2, thereby completing the present invention.

[0020] According to the present invention, a hair dyeing method can be provided that can achieve stable hair dyeing performance of a melanin precursor without being damaged by oxidation by a simple process, and further improve the hair dyeing properties.

[0021] [definition]

[0022] In this specification, "good hair dyeing properties" means a high degree of hair dyeing. A high degree of hair dyeing means a large color difference (ΔE) between the hair before and after dyeing, and can be specifically evaluated by the method described in the Examples.

[0023] In this specification, "stable hair dyeing performance of the melanin precursor" means that the hair dye is less susceptible to the influence of the ion concentration of water that varies depending on the region, and exhibits stable and excellent hair dyeing performance, compared to a case where the step of applying the above-mentioned agent B to the hair without rinsing after applying the above-mentioned agent A is not performed.

[0024] [Hair dyeing method]

[0025] The hair dyeing method of the present invention (hereinafter also referred to as "the method of the present invention") comprises the following steps 1 and 2 in sequence, and does not comprise a step of rinsing the hair between the steps 1 and 2, but comprises a step of rinsing the hair after the step 2.

[0026] Step 1: Applying Agent A to the hair.

[0027] The pH value of the agent A is 8-11 and contains the following components (a1) and (a2):

[0028] (a1) a compound represented by the following general formula (1) or a salt thereof,

[0029]

[0030] (wherein, the dotted line indicates the presence or absence of a π bond; R 1 represents a hydroxyl group or an acetoxy group; R 2 represents a hydrogen atom, or -COOR (R is a hydrogen atom, a methyl group or an ethyl group); R 3 represents a hydrogen atom, an acetyl group, a methyl group or an ethyl group;)

[0031] (a2) alkali agent;

[0032] Step 2: Applying Agent B to the hair.

[0033] The B agent contains the following component (b):

[0034] (b) an alkali metal salt or alkaline earth metal salt selected from organic acid salts or inorganic salts having 6 or less carbon atoms.

[0035] The present invention can provide a hair dyeing method which, by adopting the above-mentioned structure, i.e., applying agent A in step 1 and then performing step 2 of applying agent B to the hair to which agent A has been applied, can achieve stable hair dyeing performance of the melanin precursor in a simple process without damage due to oxidation, and further improve hair dyeing properties.

[0036] The reason why the present invention exhibits the above-mentioned effects is considered to be as follows.

[0037] In the method of the present invention, after applying Agent A containing a predetermined melanin precursor and an alkaline agent within a specific pH range to the hair, Agent B containing a specific alkali metal salt or alkaline earth metal salt is applied to the hair without rinsing it off, and then applied over the applied Agent A. This treatment increases the ion concentration in the hair, making it less susceptible to the effects of, for example, the ion concentration of the water used to rinse the hair. Furthermore, without requiring complex procedures, the hair dyeing performance of the melanin precursor can be achieved in a simple process, resulting in improved hair dyeing properties.

[0038] <Process 1>

[0039] In step 1, agent A is applied to the hair.

[0040] The pH value of the agent A is 8-11 and contains the following components (a1) and (a2):

[0041] (a1) a compound represented by the following general formula (1) or a salt thereof,

[0042]

[0043] (wherein, the dotted line indicates the presence or absence of a π bond; R 1 represents a hydroxyl group or an acetoxy group; R 2 represents a hydrogen atom, or -COOR (R is a hydrogen atom, a methyl group or an ethyl group); R 3 represents a hydrogen atom, an acetyl group, a methyl group or an ethyl group;)

[0044] (a2) Alkali agent.

[0045] (Dose A)

[0046] Agent A used in step 1 contains the following components (a1) and (a2), and has a pH of 8 to 11.

[0047] (a1) a compound represented by the following general formula (1) or a salt thereof,

[0048]

[0049] (wherein, the dotted line indicates the presence or absence of a π bond; R 1 represents a hydroxyl group or an acetoxy group; R 2represents a hydrogen atom, or -COOR (R is a hydrogen atom, a methyl group or an ethyl group); R 3 represents a hydrogen atom, an acetyl group, a methyl group or an ethyl group;)

[0050] (a2) Alkali agent.

[0051] 《Ingredient (a1): Melanin precursor》

[0052] Agent A contains component (a1) which is a compound represented by the above general formula (1) or a salt thereof. Component (a1) is a melanin precursor that is polymerized by air oxidation and converted into a melanin pigment, and functions as a hair dye.

[0053] The compound represented by the general formula (1) is an indole derivative, an indoline derivative, or a salt thereof, and in the present invention, one kind or a combination of two or more kinds thereof can be used.

[0054] From the viewpoint of improving hair dyeing properties, component (a1) is more preferably an indole derivative (ie, a π bond exists in the dotted line portion in the general formula (1)).

[0055] From the viewpoint of improving the availability and hair dyeing properties of component (a1), in the above general formula (1), R 1 Preferably, hydroxyl group, R 2 It is preferably a hydrogen atom or -COOR (R is a hydrogen atom, a methyl group or an ethyl group), and more preferably a hydrogen atom or -COOH. 3 Preferred is a hydrogen atom.

[0056] Examples of the compound represented by the general formula (1) include 5,6-dihydroxyindole, 5,6-dihydroxyindole-2-carboxylic acid, 5,6-dihydroxyindole-2-carboxylic acid methyl ester, 5,6-dihydroxyindole-2-carboxylic acid ethyl ester, N-methyl-5,6-dihydroxyindole, N-methyl-5,6-dihydroxyindole-2-carboxylic acid, N-ethyl-5,6-dihydroxyindole, N-ethyl-5,6-dihydroxyindole-2-carboxylic acid, N-acetyl-5,6-dihydroxyindole, N-acetyl-5,6-dihydroxyindole-2-carboxylic acid, 5-acetoxy-6-hydroxyindole, 5-acetoxy-6-hydroxyindole-2-carboxylic acid, 5,6 -dihydroxyindoline, 5,6-dihydroxyindoline-2-carboxylic acid, 5,6-dihydroxyindoline-2-carboxylic acid methyl ester, 5,6-dihydroxyindoline-2-carboxylic acid ethyl ester, N-methyl-5,6-dihydroxyindoline, N-methyl-5,6-dihydroxyindoline-2-carboxylic acid, N-ethyl-5,6-dihydroxyindoline, N-ethyl-5,6-dihydroxyindoline-2-carboxylic acid, N-acetyl-5,6-dihydroxyindoline, N-acetyl-5,6-dihydroxyindoline-2-carboxylic acid, 5-acetoxy-6-hydroxyindoline, 5-acetoxy-6-hydroxyindoline-2-carboxylic acid, etc., and one or more of these can be used.

[0057] Examples of salts of the compound represented by the general formula (1) include hydrochlorides, hydrobromides, sulfates, phosphates, acetates, propionates, lactates, citrates, etc. Hydrobromides are preferred from the viewpoint of improving the availability and hair dyeing properties.

[0058] Furthermore, in the general formula (1), R 2 In the case of -COOH, examples of the salt of the compound represented by the general formula (1) include carboxylates (R 2 -COO - X + (X + for Na + , K + Alkali metals, Ca + Mg + alkaline earth metal ions, ammonium ions and other cations)).

[0059] From the viewpoint of improving hair dyeing properties, component (a1) preferably contains one or more selected from 5,6-dihydroxyindole, 5,6-dihydroxyindole-2-carboxylic acid, 5,6-dihydroxyindoline, 5,6-dihydroxyindole-2-carboxylic acid, and salts thereof, more preferably contains one or more selected from 5,6-dihydroxyindole, 5,6-dihydroxyindole-2-carboxylic acid, and 5,6-dihydroxyindoleline hydrobromide, further preferably contains one or more selected from 5,6-dihydroxyindole and 5,6-dihydroxyindole-2-carboxylic acid, and even more preferably contains 5,6-dihydroxyindole and 5,6-dihydroxyindole-2-carboxylic acid.

[0060] When component (a1) contains 5,6-dihydroxyindole and 5,6-dihydroxyindole-2-carboxylic acid, the molar ratio of 5,6-dihydroxyindole to 5,6-dihydroxyindole-2-carboxylic acid is preferably in the range of 50:50 to 99:1, more preferably in the range of 80:20 to 99:1, and even more preferably in the range of 85:15 to 95:5, from the viewpoint of improving hair dyeing properties.

[0061] When component (a1) contains 5,6-dihydroxyindole and 5,6-dihydroxyindole-2-carboxylic acid, the molar ratio of 5,6-dihydroxyindole to 5,6-dihydroxyindole-2-carboxylic acid in component (a1) can be quantified by reverse phase HPLC.

[0062] From the viewpoint of improving hair dyeing properties, the content of component (a1) in agent A is preferably 0.02% by mass or more, more preferably 0.05% by mass or more, and further preferably 0.1% by mass or more, and from the viewpoint of economic efficiency, preferably 5.0% by mass or less, more preferably 3.0% by mass or less, further preferably 2.0% by mass or less, further preferably 1.0% by mass or less, further more preferably 0.8% by mass or less, further more preferably 0.6% by mass or less, further more preferably 0.5% by mass or less. From the viewpoint above, the content of component (a1) in agent A is preferably 0.02-5.0% by mass, more preferably 0.05-3.0% by mass, further preferably 0.05-2.0% by mass, further more preferably 0.05-1.0% by mass, further more preferably 0.1-0.8% by mass, further more preferably 0.1-0.6% by mass, further more preferably 0.1-0.5% by mass.

[0063] 《Ingredient (a2): Alkaline agent》

[0064] Component (a2) has a function of improving hair dyeing properties by swelling the hair and opening the cuticle, thereby allowing coloring ingredients such as component (a1) to penetrate into the interior of the hair.

[0065] Component (a2) is not particularly limited as long as it is an alkali agent commonly used in hair dye compositions, and may be either an inorganic alkali agent or an organic alkali agent. Component (a2) is preferably ammonia or an organic alkali agent from the viewpoint of improving hair dyeing properties.

[0066] Preferred alkali agents as component (a2) include ammonia; alkanolamines such as monomethanolamine, dimethanolamine, trimethanolamine, monoethanolamine, diethanolamine, triethanolamine, trishydroxymethylaminomethane, and 2-amino-2-methyl-1-propanol; alkylamines such as methylamine, dimethylamine, ethylamine, diethylamine, N-methylethylamine, propylamine, and butylamine; and aralkylamines such as benzylamine. One or more of these can be used. From the perspective of water solubility, the number of carbon atoms in the alkanolamine, alkylamine, or aralkylamine is preferably 1 to 10, more preferably 1 to 8.

[0067] Among the above, from the perspective of improving hair dyeing properties, component (a2) preferably contains one or more selected from ammonia, alkanolamines, alkylamines, and aralkylamines, more preferably contains one or more selected from ammonia and alkanolamines, and even more preferably contains alkanolamines. Among the alkanolamines, from the perspective of improving hair dyeing properties, component (a2) preferably contains one or more selected from monoethanolamine, trishydroxymethylaminomethane, and 2-amino-2-methyl-1-propanol, more preferably contains one or more selected from monoethanolamine and 2-amino-2-methyl-1-propanol, and even more preferably contains monoethanolamine.

[0068] From the viewpoint of improving hair dyeing properties, the content of the alkanolamine in the component (a2) is preferably 70% by mass or more, more preferably 80% by mass or more, and still more preferably 90% by mass or more and 100% by mass or less.

[0069] From the perspective of allowing component (a1) to penetrate into the hair and promoting the polymerization reaction of component (a1) in the hair to improve hair dyeing properties, the content of component (a2) in Agent A is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.5% by mass or more, even more preferably 1.0% by mass or more, even more preferably 2.0% by mass or more. From the perspective of suppressing hair damage, it is preferably 10% by mass or less, more preferably 7.5% by mass or less, even more preferably 5.0% by mass or less. From this perspective, the content of component (a2) in Agent A is preferably 0.01 to 10% by mass, more preferably 0.1 to 7.5% by mass, even more preferably 0.5 to 5.0% by mass, even more preferably 1.0 to 5.0% by mass, even more preferably 2.0 to 5.0% by mass.

[0070] pH Regulator

[0071] From the viewpoint of adjusting the pH value to the desired range described below, promoting the polymerization reaction of the component (a1) in the hair, and improving the hair dyeing properties, it is preferred that Agent A further contain a pH adjuster.

[0072] Since Agent A contains an alkaline agent as component (a2), a protonating agent is preferably used as the pH adjuster for Agent A. The protonating agent may be a monobasic acid or a polybasic acid, and may be an organic acid (having 1 to 8 carbon atoms, excluding ascorbic acid) or an inorganic acid.

[0073] The protonating agent may be, for example, one or more selected from hydrochloric acid, sulfuric acid, phosphoric acid, formic acid, acetic acid, and citric acid. From the viewpoint of adjusting the pH of Agent A to the following range, one or more selected from phosphoric acid and citric acid are preferred.

[0074] When Agent A contains a pH adjuster, from the viewpoint of adjusting the pH value of Agent A to the following range, the content of the pH adjuster in Agent A is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, and even more preferably 0.2% by mass or more, and is preferably 5.0% by mass or less, more preferably 4.0% by mass or less, even more preferably 3.5% by mass or less, even more preferably 2.5% by mass or less, and even more preferably 1.5% by mass or less.

[0075] Other ingredients

[0076] Agent A may contain, in addition to the above-mentioned components, components commonly used in hair dye compositions as appropriate, within a range that does not impair the purpose of the present invention. Examples of such components include water, lower alcohols, aqueous media such as low-molecular-weight diols and triols having 6 or fewer carbon atoms, surfactants, viscosity modifiers, silicones, aromatic alcohols, coloring components other than component (a1), polymers, oils, antidandruff agents, vitamins, bactericides, anti-inflammatory agents, preservatives, chelating agents, moisturizers, pearlescent agents, ceramides, fragrances, and ultraviolet absorbers.

[0077] Agent A may contain the following component (b). From the viewpoint of hair dyeing properties, the content of component (B) in Agent A is preferably 10% by mass or less, more preferably 8% by mass or less, more preferably 5% by mass or less, and even more preferably 3.5% by mass or less.

[0078] pH value

[0079] From the perspective of improving hair dyeing properties, the pH value of Agent A is 8 or higher, preferably 9 or higher, more preferably 9.5 or higher, and even more preferably 9.8 or higher. Furthermore, from the perspective of improving hair dyeing properties and suppressing hair damage, the pH value is 11 or lower, preferably 10.8 or lower, and even more preferably 10.5 or lower. From these perspectives, the pH value of Agent A is 8 to 11, preferably 9 to 10.8, more preferably 9.5 to 10.8, and even more preferably 9.8 to 10.5.

[0080] The pH value is a value measured at 25° C., and can be specifically measured by the method described in Examples.

[0081] From the perspective of suppressing hair damage, Agent A preferably contains substantially no oxidizing agents such as hydrogen peroxide and sodium bromate. Agent A containing substantially no oxidizing agents means that the content of the oxidizing agent in Agent A is preferably less than 0.1% by mass, more preferably less than 0.01% by mass, and even more preferably 0% by mass.

[0082] The dosage form of Agent A is not particularly limited and may be in any form, such as liquid, foam, paste, cream, solid, or powder. From the perspective of application to hair by painting, dipping, or the like, Agent A is preferably in the form of a liquid, paste, or cream.

[0083] The preparation method of Agent A is not particularly limited. For example, it can be prepared by mixing component (a1), component (a2), and other components used as needed using a known stirring device. From the perspective of avoiding polymerization of component (a1), Agent A is preferably prepared under an inert gas atmosphere such as nitrogen.

[0084] (Agent A is applied to hair)

[0085] In step 1, the hair may be dry or wet when Agent A is applied. The method for applying Agent A to the hair can be any method that allows Agent A to come into contact with the hair. Examples include methods of applying Agent A to the hair and methods of immersing the hair in Agent A.

[0086] In step 1, from the perspective of balancing hair dyeing properties and economic efficiency, the amount of Agent A applied to the hair is preferably in a bath ratio (dry mass of hair: mass of Agent A) of 1:0.05 to 1:20, more preferably 1:0.3 to 1:10, and even more preferably 1:0.5 to 1:5. The dry mass of hair refers to the mass of hair washed with shampoo, dried with hot air from a hair dryer for 30 minutes, and then left to stand at a temperature of 25°C and a relative humidity of 65% for at least one day and night.

[0087] The hair to be applied is preferably the head, and any hair may be applied to at least a portion of the head.

[0088] In step 1, when Agent A is applied to the hair by applying it to the hair, the application time is preferably 10 seconds or longer, more preferably 30 seconds or longer, and even more preferably 1 minute or longer, from the perspective of allowing the components of Agent A to penetrate into the hair. From the perspective of reducing the burden on the operator, the application time is preferably 10 minutes or shorter, more preferably 5 minutes or shorter.

[0089] In step 1, when agent A is applied to the hair by immersing the hair in agent A, from the above-mentioned viewpoint, the immersion time is preferably 1 minute or longer, more preferably 3 minutes or longer, and preferably 30 minutes or shorter, more preferably 20 minutes or shorter.

[0090] In step 1, Agent A is preferably applied to the hair by applying it to the hair or immersing it in it, and then left to stand. The total standing time can be appropriately adjusted depending on the desired hair color tone. From the perspective of allowing the components of Agent A to penetrate the hair, it is preferably 1 minute or longer, more preferably 3 minutes or longer, and even more preferably 5 minutes or longer. From the perspective of reducing the burden on the operator, it is preferably 60 minutes or shorter, more preferably 30 minutes or shorter, and even more preferably 20 minutes or shorter. From these perspectives, the time Agent A is applied to the hair is preferably 1 to 60 minutes, more preferably 3 to 30 minutes, and even more preferably 5 to 20 minutes.

[0091] In step 1, the temperature at which Agent A is applied to the hair is not particularly limited. From the perspective of the handleability of Agent A, it is preferably 40°C or lower, more preferably 35°C or lower. From the perspective of improving hair dyeing properties, it is preferably 15°C or higher, more preferably 20°C or higher, and even more preferably 25°C or higher. From these perspectives, the temperature at which Agent A is applied to the hair is preferably 15-40°C, more preferably 20-35°C. Furthermore, if Agent A is left to stand after application, the temperature during this standing is not particularly limited, but is preferably 25-50°C, more preferably 30-40°C.

[0092] From the perspective of achieving stable hair dyeing performance of the melanin precursor and improving hair dyeing properties, the method of the present invention does not include a hair rinsing step (hereinafter referred to as a "rinsing step") after applying Agent A to the hair and before applying Agent B to the hair. In other words, Agent B is applied to the hair after Agent A has been applied.

[0093] (Dose B)

[0094] Agent B used in step 2 contains the following component (b):

[0095] (b) an alkali metal salt or alkaline earth metal salt selected from organic acid salts or inorganic salts having 6 or less carbon atoms.

[0096] <<Ingredient (b)>>

[0097] Component (b) increases the ion concentration, making the hair less susceptible to the ion concentration of water used for rinsing. Examples of alkali metal salts include sodium salts and potassium salts. Examples of alkaline earth metal salts include calcium salts and magnesium salts. One or more of these salts may be used. Examples of organic acid salts having 6 or fewer carbon atoms include carboxylates, dicarboxylates, citrates, malates, succinates, and lactates. Examples of inorganic salts include nitrates, sulfates, and chlorides.

[0098] Among these, from the viewpoint of stabilizing the hair dyeing performance of the melanin precursor and improving the hair dyeing properties, component (b) is preferably one or more selected from the chlorides, carboxylates, sulfates and carbonates of sodium, potassium, calcium and magnesium, more preferably one or more selected from the chlorides, carboxylates and sulfates of sodium, potassium, calcium and magnesium, further preferably one or more selected from the group consisting of sodium chloride, potassium chloride, calcium chloride, magnesium chloride, calcium acetate, potassium acetate, calcium sulfate and potassium sulfate, further more preferably one or more selected from the group consisting of sodium chloride, magnesium chloride, calcium acetate and potassium sulfate.

[0099] From the perspective of further stabilizing the hair dyeing performance of the melanin precursor and improving hair dyeing properties, the content of component (b) in Agent B is preferably 0.001% by mass or more, more preferably 0.005% by mass or more, and even more preferably 0.01% by mass or more. From the perspective of economic efficiency and ease of application to hair, it is preferably 95% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less. From these perspectives, the content of component (b) in Agent B is preferably 0.001 to 95% by mass, more preferably 0.005 to 85% by mass, and even more preferably 0.01 to 80% by mass.

[0100] Furthermore, when Agent B is made into a liquid or foamy form, the content of component (b) in Agent B is preferably 0.05 to 30% by mass, and more preferably 0.1 to 10% by mass. When Agent B is made into a paste or ointment, the content of component (b) in Agent B is preferably 50 to 95% by mass, and more preferably 60 to 80% by mass.

[0101] Other ingredients

[0102] Agent B may contain, in addition to the above-mentioned ingredients, ingredients commonly used in hair dye compositions as appropriate, within a range that does not impair the purpose of the present invention. Examples of such ingredients include aqueous media such as water, lower alcohols, low molecular weight diols and triols having 6 or fewer carbon atoms, surfactants, viscosity modifiers, silicones, aromatic alcohols, polymers, oils, antidandruff agents, vitamins, bactericides, anti-inflammatory agents, preservatives, chelating agents, moisturizers, pearlescent agents, ceramides, fragrances, and ultraviolet absorbers.

[0103] From the perspective of suppressing hair damage, Agent B preferably contains substantially no oxidizing agent. "Agent B contains substantially no oxidizing agent" means that the oxidizing agent content in Agent B is preferably less than 0.1% by mass, more preferably less than 0.01% by mass, and even more preferably 0% by mass. That is, in the hair dyeing method of the present invention, Agents A and B preferably contain no oxidizing agent. Examples of the oxidizing agent include those listed above for Agent A, and the oxidizing agent content also means the content described in Agent A.

[0104] The dosage form of Agent B is not particularly limited and can be in any form such as liquid, foam, paste, ointment, solid, or powder, preferably in liquid, foam, paste, or ointment.

[0105] The method for preparing agent B is not particularly limited, and it can be prepared, for example, by blending component (b) and other components as needed, and mixing them using a known stirring apparatus or the like.

[0106] (Apply Agent B to hair)

[0107] In step 2, the hair to which Agent B is applied is the hair to which Agent A has already been applied. The method for applying Agent B to the hair may be any method that allows Agent B to come into contact with the hair, and examples thereof include a method of applying Agent B to the hair and a method of immersing the hair in Agent B. Of these, applying Agent B to the hair is preferred from the perspective of further stabilizing the hair dyeing performance of the melanin precursor and improving hair dyeing properties.

[0108] In step 2, from the viewpoint of further stabilizing the hair dyeing performance of the melanin precursor and improving the hair dyeing properties, as well as from the viewpoint of economic efficiency, the agent B is applied to the hair at a bath ratio (dry mass of hair: mass of component (b)) of preferably 1:0.00005 or more, more preferably 1:0.00005 to 1:1, more preferably 1:0.005 to 1:0.5, and even more preferably 1:0.012 to 1:0.15.

[0109] In step 2, when agent B is applied to the hair by applying the agent B to the hair, the application time is preferably 10 seconds or longer, more preferably 30 seconds or longer, and even more preferably 1 minute or longer, from the viewpoint of further stabilizing the hair dyeing performance of the melanin precursor and improving the hair dyeing properties. From the viewpoint of reducing the burden on the operator, the application time is preferably 10 minutes or shorter, more preferably 5 minutes or shorter.

[0110] In step 2, after applying Agent B to the hair, it is preferably followed by a step of acclimating the agent to the hair. Examples of methods for acclimating Agent B to the hair include rubbing the hair to which Agent B has been applied. From the perspective of further stabilizing the dyeing properties of the melanin precursor and improving hair dyeing performance, the time for acclimating Agent B to the hair is preferably 20 seconds or longer, more preferably 40 seconds or longer, and even more preferably 50 seconds or longer. From the perspective of reducing the burden on the hair conditioner, the time for acclimating Agent B to the hair is preferably 20 minutes or shorter, more preferably 10 minutes or shorter, and even more preferably 3 minutes or shorter. In view of this, the time for acclimating Agent B after application to the hair is preferably 20 seconds to 20 minutes, more preferably 40 seconds to 10 minutes, and even more preferably 50 seconds to 3 minutes.

[0111] In step 2, the temperature at which Agent B is applied to the hair is not particularly limited. However, from the perspective of ease of handling of Agent B, it is preferably 40°C or lower, more preferably 35°C or lower. From the perspective of improving hair dyeing properties, it is preferably 15°C or higher, more preferably 20°C or higher. From these perspectives, the temperature at which Agent B is applied to the hair is preferably 15 to 40°C, more preferably 20 to 35°C.

[0112] <Rinsing process>

[0113] The method of the present invention includes a step of rinsing Agent A and Agent B applied to the hair after step 2 (hereinafter also referred to as the "rinsing step"). The rinsing step is performed, for example, by rinsing Agent A and Agent B applied to the hair with water. The temperature of the water is not particularly limited, but is preferably 35 to 45°C. The time for rinsing the hair is not particularly limited, but from the perspective of further stabilizing the hair dyeing performance of the melanin precursor and improving hair dyeing properties, it is preferably 10 seconds or longer, more preferably 20 seconds or longer, and preferably 5 minutes or shorter, more preferably 3 minutes or shorter, and even more preferably 1 minute or shorter.

[0114] <Drying process>

[0115] The method of the present invention preferably includes a step of drying the hair (hereinafter also referred to as the "drying step") after the rinsing step. The drying step is a step of reducing the moisture content of the hair and may include, for example, performing one or more drying treatments selected from towel drying, hair dryer drying (with cold air or hot air), and air drying to actively reduce the moisture content of the hair. Preferably, a combination of two or more of these drying treatments is performed.

[0116] From the perspective of stabilizing the hair dyeing performance of the melanin precursor and improving the hair dyeing properties, the time from the end of the rinsing step to the start of the drying step is preferably 20 minutes or less, more preferably 17 minutes or less, and further preferably 15 minutes or less. The lower limit is not particularly limited and is 10 seconds or more.

[0117] Hereinafter, the present invention further discloses the following details regarding the above-mentioned embodiment.

[0118] <1>

[0119] A hair dyeing method comprising the following steps 1 and 2 in sequence, wherein after step 1, step 2 is performed on the agent A applied to the hair, and after step 2, the hair is rinsed.

[0120] Step 1: Applying Agent A to the hair.

[0121] The pH value of the above-mentioned agent A is 8-11 and contains the following components (a1) and (a2):

[0122] (a1) a compound represented by the following general formula (1) or a salt thereof,

[0123]

[0124] (wherein, the dotted line indicates the presence or absence of a π bond; R 1 represents a hydroxyl group or an acetoxy group; R 2 represents a hydrogen atom, or -COOR (R is a hydrogen atom, a methyl group or an ethyl group); R 3 represents a hydrogen atom, an acetyl group, a methyl group or an ethyl group;)

[0125] (a2) alkali agent;

[0126] Step 2: Applying Agent B to the hair.

[0127] The above-mentioned Agent B contains the following ingredient (b):

[0128] (b) an alkali metal salt or alkaline earth metal salt selected from organic acid salts or inorganic salts having 6 or less carbon atoms.

[0129] <2>

[0130] The hair dyeing method of <1>, wherein the component (a1) is selected from 5,6-dihydroxyindole, 5,6-dihydroxyindole-2-carboxylic acid, 5,6-dihydroxyindole-2-carboxylic acid methyl ester, 5,6-dihydroxyindole-2-carboxylic acid ethyl ester, N-methyl-5,6-dihydroxyindole, N-methyl-5,6-dihydroxyindole-2-carboxylic acid, N-ethyl-5,6-dihydroxyindole, N-ethyl-5,6-dihydroxyindole-2-carboxylic acid, N-acetyl-5,6-dihydroxyindole, N-acetyl-5,6-dihydroxyindole-2-carboxylic acid, 5-acetoxy-6-hydroxyindole, 5-acetoxy-6-hydroxyindole-2-carboxylic acid, 5,6-dihydroxyindoline, 5,6-dihydroxyindoline-2-carboxylic acid Acid, methyl 5,6-dihydroxyindoline-2-carboxylate, ethyl 5,6-dihydroxyindoline-2-carboxylate, N-methyl-5,6-dihydroxyindoline, N-methyl-5,6-dihydroxyindoline-2-carboxylic acid, N-ethyl-5,6-dihydroxyindoline, N-ethyl-5,6-dihydroxyindoline-2-carboxylic acid, N-acetyl-5,6-dihydroxyindoline, N-acetyl-5,6-dihydroxyindoline-2-carboxylic acid, 5-acetoxy-6-hydroxyindoline and 5-acetoxy-6-hydroxyindoline-2-carboxylic acid, and one or more of the hydrochlorides, hydrobromides, sulfates, phosphates, acetates, propionates, lactates and citrates of these compounds, preferably the hydrobromides of these compounds.

[0131] <3>

[0132] The hair dyeing method according to <1> or <2>, wherein the component (a1) preferably comprises one or more selected from 5,6-dihydroxyindole, 5,6-dihydroxyindole-2-carboxylic acid, 5,6-dihydroxyindoline, 5,6-dihydroxyindole-2-carboxylic acid, and salts thereof, more preferably comprises one or more selected from 5,6-dihydroxyindole, 5,6-dihydroxyindole-2-carboxylic acid, and 5,6-dihydroxyindoleline hydrobromide, further preferably comprises one or more selected from 5,6-dihydroxyindole and 5,6-dihydroxyindole-2-carboxylic acid, and further more preferably comprises a mixture of 5,6-dihydroxyindole and 5,6-dihydroxyindole-2-carboxylic acid.

[0133] <4>

[0134] The hair dyeing method according to any one of <1> to <3>, wherein R 2 When -COOH is present, the salt of the compound represented by the general formula (1) is its carboxylate (R 2 -COO - X + (X + is a cation)).

[0135] <5>

[0136] The hair dyeing method according to any one of <1> to <4>, wherein when the component (a1) contains 5,6-dihydroxyindole and 5,6-dihydroxyindole-2-carboxylic acid, the molar ratio of the 5,6-dihydroxyindole to the 5,6-dihydroxyindole-2-carboxylic acid is preferably in the range of 50:50 to 99:1, more preferably in the range of 80:20 to 99:1, and even more preferably in the range of 85:15 to 95:5.

[0137] <6>

[0138] The hair dyeing method according to any one of <1> to <5>, wherein the content of the component (a1) is preferably 0.02 to 5.0% by mass, more preferably 0.05 to 3.0% by mass, further preferably 0.1 to 2.0% by mass, further preferably 0.1 to 1.0% by mass, further more preferably 0.1 to 0.8% by mass, further more preferably 0.1 to 0.6% by mass, further more preferably 0.1 to 0.5% by mass.

[0139] <7>

[0140] The hair dyeing method according to any one of <1> to <6>, wherein the component (a2) is an inorganic alkaline agent or an organic alkaline agent, preferably ammonia or an organic alkaline agent.

[0141] <8>

[0142] A hair dyeing method as described in any one of <1> to <7>, wherein the above-mentioned component (a2) is one or more selected from ammonia, alkanolamine, alkylamine, and arylalkylamine, and the number of carbon atoms of the above-mentioned alkanolamine, alkylamine, or arylalkylamine is preferably 1 to 10, more preferably 1 to 8.

[0143] <9>

[0144] The hair dyeing method according to any one of <1> to <8>, wherein the component (a2) preferably comprises one or more selected from ammonia, alkanolamines, alkylamines, and aralkylamines, more preferably comprises one or more selected from ammonia and alkanolamines, and even more preferably comprises alkanolamines.

[0145] <10>

[0146] The hair dyeing method according to any one of <1> to <9>, wherein the component (a2) preferably comprises one or more selected from monoethanolamine, trishydroxymethylaminomethane and 2-amino-2-methyl-1-propanol, more preferably comprises one or more selected from monoethanolamine and 2-amino-2-methyl-1-propanol, and even more preferably comprises monoethanolamine.

[0147] <11>

[0148] The hair dyeing method according to any one of <1> to <10>, wherein the content of the alkanolamine in the component (a2) is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more and 100% by mass or less.

[0149] <12>

[0150] In the hair dyeing method according to any one of <1> to <11>, the content of the component (a2) in the agent A is preferably 0.01 to 10% by mass, more preferably 0.1 to 7.5% by mass, further preferably 0.5 to 5.0% by mass, further more preferably 1.0 to 5.0% by mass, further more preferably 2.0 to 5.0% by mass.

[0151] <13>

[0152] A hair dyeing method as described in any one of <1> to <12>, wherein the above-mentioned agent A further contains a pH adjuster, and preferably the above-mentioned pH adjuster is a protonating agent selected from one or more monobasic acids and polybasic acids, or one or more protonating agents selected from organic acids (having 1 to 8 carbon atoms, excluding ascorbic acid) and inorganic acids. The protonating agent is preferably one or more selected from hydrochloric acid, sulfuric acid, phosphoric acid, formic acid, acetic acid, and citric acid, and more preferably one or more selected from phosphoric acid and citric acid.

[0153] <14>

[0154] The hair dyeing method of <13>, wherein, when the above-mentioned agent A contains the above-mentioned pH adjuster, the content of the above-mentioned pH adjuster in the above-mentioned agent A is preferably 0.05 mass% or more, more preferably 0.1 mass% or more, and further preferably 0.2 mass% or more, and is preferably 5.0 mass% or less, more preferably 4.0 mass% or less, further preferably 3.5 mass% or less, further more preferably 2.5 mass% or less, and further more preferably 1.5 mass% or less.

[0155] <15>

[0156] A hair dyeing method as described in any one of <1> to <14>, wherein the above-mentioned agent A further contains one or more selected from the group consisting of an aqueous medium, a surfactant, a viscosity modifier, silicone, an aromatic alcohol, a coloring component other than component (a1), a polymer, an oil, an anti-dandruff agent, a vitamin agent, a bactericide, an anti-inflammatory agent, a preservative, a chelating agent, a moisturizer, a pearlescent agent, a ceramide, a fragrance, and a UV absorber.

[0157] <16>

[0158] The hair dyeing method according to any one of <1> to <15>, wherein the pH value of the agent A at 25°C is 8 to 11, preferably 9 to 10.8, more preferably 9.5 to 10.8, and even more preferably 9.8 to 10.5.

[0159] <17>

[0160] The hair dyeing method according to any one of <1> to <16>, wherein the agent A contains substantially no oxidizing agent.

[0161] <18>

[0162] The hair dyeing method according to any one of <1> to <17>, wherein the formulation of the agent A is liquid, foam, paste, cream, solid, or powder, preferably liquid, paste, or cream.

[0163] <19>

[0164] The hair dyeing method according to any one of <1> to <18>, wherein the hair is in a dry state or a wet state when the agent A is applied.

[0165] <20>

[0166] The hair dyeing method according to any one of <1> to <19>, wherein the method of applying the agent A to the hair is a method of contacting the agent A with the hair, preferably a method of applying the agent A to the hair or a method of immersing the hair in the agent A.

[0167] <21>

[0168] The hair dyeing method according to any one of <1> to <20>, wherein the amount of the agent A applied to the hair is preferably 1:0.05 to 1:20, more preferably 1:0.3 to 1:10, and even more preferably 1:0.5 to 1:5, in terms of bath ratio (dry mass of hair:mass of agent A).

[0169] <22>

[0170] In the hair dyeing method according to any one of <1> to <21>, when the agent A is applied to the hair by coating, the application time is preferably 10 seconds or longer, more preferably 30 seconds or longer, further preferably 1 minute or longer, and preferably 10 minutes or shorter, more preferably 5 minutes or shorter.

[0171] <23>

[0172] In the hair dyeing method according to any one of <1> to <21>, when the agent A is applied to the hair by immersion, the immersion time is preferably 1 minute or longer, more preferably 3 minutes or longer, and preferably 30 minutes or shorter, more preferably 20 minutes or shorter.

[0173] <24>

[0174] The hair dyeing method according to any one of <1> to <23>, wherein the agent A is applied to the hair and then left to stand for a total time of preferably 1 to 60 minutes, more preferably 3 to 30 minutes, and even more preferably 5 to 20 minutes.

[0175] <25>

[0176] In the hair dyeing method according to any one of <1> to <24>, the temperature when the agent A is applied to the hair is preferably 15 to 40°C, more preferably 20 to 35°C.

[0177] <26>

[0178] The hair dyeing method according to any one of <1> to <25>, wherein the component (b) contains one or more selected from alkali metal salts and alkaline earth metal salts.

[0179] <27>

[0180] The hair dyeing method according to any one of <1> to <26>, wherein the component (b) contains one or more organic acid salts having 6 or less carbon atoms selected from carboxylates, dicarboxylates, citrates, malates, succinates, and lactates.

[0181] <28>

[0182] The hair dyeing method according to any one of <1> to <27>, wherein the component (b) contains one or more inorganic salts selected from nitrates, sulfates, and chlorides.

[0183] <29>

[0184] The hair dyeing method according to any one of <1> to <28>, wherein the component (b) is at least one selected from chlorides, carboxylates, sulfates, and carbonates of sodium, potassium, calcium, and magnesium.

[0185] <30>

[0186] The hair dyeing method according to any one of <1> to <29>, wherein the content of the component (b) in the agent B is preferably 0.001 to 95% by mass, more preferably 0.005 to 85% by mass, and even more preferably 0.01 to 80% by mass.

[0187] <31>

[0188] A hair dyeing method as described in any one of <1> to <30>, wherein the above-mentioned B agent further contains one or more selected from the group consisting of an aqueous medium, a surfactant, a viscosity modifier, silicone, an aromatic alcohol, a polymer, an oily agent, an anti-dandruff agent, a vitamin agent, a bactericide, an anti-inflammatory agent, a preservative, a chelating agent, a moisturizer, a pearlescent agent, a ceramide, a fragrance, and a UV absorber.

[0189] <32>

[0190] The hair dyeing method according to any one of <1> to <31>, wherein the agent B does not substantially contain an oxidizing agent.

[0191] <33>

[0192] The hair dyeing method according to any one of <1> to <32>, wherein both the agent A and the agent B do not contain an oxidizing agent.

[0193] <34>

[0194] The hair dyeing method according to any one of <1> to <33>, wherein the formulation of the agent B is in liquid, foam, paste, cream, solid, or powder form.

[0195] <35>

[0196] The hair dyeing method according to any one of <1> to <34>, wherein the method of applying the agent B to the hair is a method of bringing the agent B into contact with the hair, preferably a method of applying the agent B to the hair or a method of immersing the hair in the agent B.

[0197] <36>

[0198] The hair dyeing method according to any one of <1> to <35>, wherein the amount of the agent B applied to the hair is preferably 1:0.0001 to 1:1, more preferably 1:0.001 to 1:0.5, and even more preferably 1:0.01 to 1:0.15, in terms of bath ratio (dry mass of hair:mass of component (b)).

[0199] <37>

[0200] In the hair dyeing method according to any one of <1> to <36>, when the agent B is applied to the hair by coating, the application time is preferably 10 seconds or longer, more preferably 30 seconds or longer, further preferably 1 minute or longer, and preferably 10 minutes or shorter, more preferably 5 minutes or shorter.

[0201] <38>

[0202] The hair dyeing method according to any one of <1> to <37>, wherein after applying the agent B to the hair, there is a further step of allowing it to adapt to the hair, and the adaptation time in this case is preferably 20 seconds to 20 minutes, more preferably 40 seconds to 10 minutes, and even more preferably 50 seconds to 3 minutes.

[0203] <39>

[0204] In the hair dyeing method according to any one of <1> to <38>, the temperature when applying the agent B to the hair is preferably 25 to 40°C, more preferably 30 to 35°C.

[0205] <40>

[0206] The hair dyeing method according to any one of <1> to <39>, wherein the rinsing step is performed by rinsing the agent A and the agent B with water, and the temperature of the water is preferably 35 to 45°C.

[0207] <41>

[0208] In the hair dyeing method according to any one of <1> to <40>, the rinsing time in the step of rinsing the hair is preferably 10 seconds or longer, more preferably 20 seconds or longer, and preferably 5 minutes or shorter, more preferably 3 minutes or shorter, and even more preferably 1 minute or shorter.

[0209] <42>

[0210] The hair dyeing method according to any one of <1> to <41>, wherein the step of rinsing the hair is followed by a drying step of drying the hair, preferably performing one or more drying treatments selected from the group consisting of towel drying, hair dryer drying (with cold air or hot air), and air drying, and more preferably performing a combination of two or more drying treatments.

[0211] <43>

[0212] As in the hair dyeing method of <42>, the time from the completion of the above-mentioned rinsing step to the start of the above-mentioned drying step is preferably 20 minutes or less, more preferably 17 minutes or less, and further preferably 15 minutes or less, and the lower limit is not particularly limited and is 10 seconds or more.

[0213] [Example]

[0214] Hereinafter, the present invention will be described with reference to Examples, but the present invention is not limited to the scope of the Examples. In the present Examples, various measurements and evaluations were performed by the following methods.

[0215] pH measurement

[0216] The pH value of Agent A at 25° C. was measured using a pH meter (F-72, manufactured by Horiba, Ltd.).

[0217] Color difference ΔE before and after dyeing

[0218] Hair tresses were dyed using the methods described in each example. The colors of the hair tresses before and after the dyeing treatment were measured at six locations on each hair tress using a colorimeter ("CR-400" manufactured by Konica Minolta Co., Ltd.).

[0219] L0 * 、a0 * 、b0 * : Color of hair bundle before dyeing (average value of 6 points)

[0220] L1 * 、a1 * 、b1 * : Color of the hair bundle after dyeing (average value of 6 points). * 、a * 、b * Refers to the CIE1976 L * a * b * L specified by the color system * 、a * 、b * .

[0221] Furthermore, the color difference ΔE was calculated using the following formula.

[0222] ΔE={(ΔL * ) 2 +(Δa * ) 2 +(Δb * ) 2} 1 / 2

[0223] Furthermore, ΔL * :L1 * -L0 * , Δa * :a1 * -a0 * , Δb * :b1 * -b0 * .

[0224] A larger ΔE value indicates a higher degree of dyeing and better hair dyeing properties. ΔE is preferably 20 or greater for practical purposes.

[0225] <Improved hair dyeability>

[0226] The difference in ΔE between the hair bundle without applying the following Agent B and the hair bundle with Agent B applied by each method was determined (the difference from ΔE without Agent B). A larger difference than this ΔE means improved hair dyeing properties.

[0227] <Preparation of hair bundles for evaluation>

[0228] An untreated hair tress (a 10 cm long, 1 g white hair tress from a Chinese woman, "BM-WA" manufactured by Beaulax Co., Ltd.) was washed twice with a standard shampoo with the following composition, dried with hot air from a hair dryer for 30 minutes, and then allowed to stand at a temperature of 25°C and a relative humidity of 65% for at least one day and night to prepare a hair tress for evaluation of the degree of dyeing and improvement in dyeability.

[0229]

[0230] Example 1

[0231] The components shown in Table 1 were blended in the proportions described in Table 1 and mixed until uniform, thereby preparing Agent A and Agent B.

[0232] Agent A was applied to the hair tress in the state shown in Table 1 at the bath ratio (dry hair mass: mass of Agent A) shown in Table 1 and allowed to stand for the time shown in Table 1 (Step 1). Agent B was applied to the hair tress to which Agent A had been applied at the bath ratio (dry hair mass: mass of component (b)) shown in Table 1 and rubbed for the time shown in Table 1 to acclimate (Step 2). The hair tress was then rinsed with water (approximately 40°C) for 30 seconds (Rinsing Step). After 15 minutes, the hair tress was dried with cold air from a hair dryer for 15 minutes (Drying Step). The dried hair tress was measured and evaluated using the above methods. Furthermore, the improvement in hair dyeability was evaluated by determining the difference in ΔE compared to the following Comparative Example 1, in which Agent B was not applied. The results are shown in Table 1.

[0233] In addition, the compounding amounts (mass %) described in Table 1 are all amounts of active ingredients, and the total of Agent A and Agent B is 100 mass %.

[0234] Comparative Example 1

[0235] The hair dyeing treatment, measurement, and evaluation were performed in the same manner as in Example 1, except that the step of applying Agent B (Step 2) was not performed. The results are shown in Table 1.

[0236] Comparative Example 2

[0237] Hair dyeing, measurement, and evaluation were performed in the same manner as in Example 1, except that Agent B was applied to the hair tress (Step 2), rinsed with water (approximately 40°C) for 30 seconds (Rinsing Step), and 15 minutes later, Agent A was applied to the hair tress that had been blow-dried with cold air from a hair dryer (Step 1). The results are shown in Table 1.

[0238] Comparative Example 3

[0239] The hair dyeing treatment, measurement, and evaluation were performed in the same manner as in Example 1, except that Agent B was applied to the hair bundle that had undergone Step 1, the rinsing step, and the drying step. The results are shown in Table 1.

[0240] Comparative Example 4

[0241] The ingredients listed in Table 1 were blended in the proportions described in Table 1 and mixed until uniform, thereby preparing Agent A. Agent A was applied to the hair tresses in the conditions shown in Table 1 at the bath ratio (dry hair mass: mass of Agent A) shown in Table 1 and allowed to stand for the time indicated in Table 1 (Step 1). The hair tresses were then rinsed with water (approximately 40°C) for 30 seconds (rinsing step). After 15 minutes, the hair tresses were dried with cold air from a hair dryer for 15 minutes (drying step). The dried hair tresses were measured and evaluated using the methods described above. The results are shown in Table 1.

[0242] [Table 1]

[0243]

[0244] Example 2

[0245] The components shown in Table 2 were blended at the blending ratios described in Table 2 and mixed until uniform, thereby preparing Agent A and Agent B.

[0246] Agent A was applied to the hair tress in the state shown in Table 2 at the bath ratio (dry hair mass: mass of Agent A) shown in Table 2 and allowed to stand for the time shown in Table 2 (Step 1). Agent B was applied to the hair tress with Agent A at the bath ratio (dry hair mass: mass of component (b)) shown in Table 2 and rubbed for the time shown in Table 2 to acclimate the hair tress (Step 2). The hair tress was then rinsed with water (approximately 40°C) for 30 seconds (Rinsing Step). After 15 minutes, the hair tress was dried with cold air from a hair dryer for 15 minutes (Drying Step). The dried hair tress was measured and evaluated using the above methods. Furthermore, the improvement in hair dyeability was evaluated by determining the difference in ΔE compared to Comparative Example 5, described below, in which Agent B was not applied. The results are shown in Table 2.

[0247] In addition, the compounding amounts (mass %) described in Table 2 are all amounts of active ingredients, and the total of Agent A and Agent B is 100 mass %.

[0248] Comparative Example 5

[0249] The hair dyeing treatment, measurement, and evaluation were performed in the same manner as in Example 2, except that the step of applying Agent B (Step 2) was not performed. The results are shown in Table 2.

[0250] Comparative Example 6

[0251] Hair dyeing, measurement, and evaluation were performed in the same manner as in Example 2, except that Agent B was applied to the hair tress (Step 2), rinsed with water (approximately 40°C) for 30 seconds (Rinsing Step), and 15 minutes later, Agent A was applied to the hair tress that had been blow-dried with cold air from a hair dryer (Step 1). The results are shown in Table 2.

[0252] Comparative Example 7

[0253] The hair dyeing treatment, measurement, and evaluation were performed in the same manner as in Example 2, except that Agent B was applied to the hair bundle that had undergone Step 1, the rinsing step, and the drying step. The results are shown in Table 2.

[0254] Comparative Example 8

[0255] The ingredients listed in Table 2 were blended in the proportions described in Table 2 and mixed until uniform, thereby preparing Agent A. Agent A was applied to the hair tresses in the conditions shown in Table 2 at the bath ratio (dry hair mass: mass of Agent A) shown in Table 2 and allowed to stand for the time indicated in Table 2 (Step 1). The hair tresses were then rinsed with water (approximately 40°C) for 30 seconds (rinsing step). After 15 minutes, the hair tresses were dried with cold air from a hair dryer for 15 minutes (drying step). The dried hair tresses were measured and evaluated using the methods described above. The results are shown in Table 2.

[0256] [Table 2]

[0257]

[0258] Examples 3 and 4

[0259] The components shown in Table 3 were blended at the blending ratios described in Table 3 and mixed until uniform, thereby preparing Agent A and Agent B.

[0260] Agent A was applied to the hair tress in the state shown in Table 3 at the bath ratio (dry hair mass: mass of Agent A) shown in Table 3 and allowed to stand for the time shown in Table 3 (Step 1). Agent B was applied to the hair tress with Agent A at the bath ratio (dry hair mass: mass of component (b)) shown in Table 3 and rubbed for the time shown in Table 3 to allow acclimatization (Step 2). The hair tress was then rinsed with water (approximately 40°C) for 30 seconds (Rinsing Step). Immediately thereafter, the hair tress was dried with cold air from a hair dryer for 15 minutes (Drying Step). The dried hair tress was measured and evaluated using the above methods. Furthermore, the improvement in hair dyeability was evaluated by determining the difference in ΔE compared to the following Comparative Example 9, in which Agent B was not applied. The results are shown in Table 3.

[0261] In addition, the compounding amounts (mass %) described in Table 3 are all amounts of active ingredients, and the total of Agent A and Agent B is 100 mass %.

[0262] Comparative Example 9

[0263] The hair dyeing treatment, measurement, and evaluation were performed in the same manner as in Examples 3 and 4, except that the step of applying Agent B (Step 2) was not performed. The results are shown in Table 3.

[0264] [Table 3]

[0265]

[0266] Examples 5 to 8

[0267] The components shown in Table 4 were blended in the proportions described in Table 4 and mixed until uniform, thereby preparing Agent A and Agent B.

[0268] Agent A was applied to the hair tress in the state shown in Table 4 at the bath ratio (hair dry mass: mass of Agent A) shown in Table 4 and allowed to stand for the time shown in Table 4 (Step 1). Agent B was applied to the hair tress to which Agent A had been applied at the bath ratio (hair dry mass: mass of component (b)) shown in Table 4 and rubbed for the time shown in Table 4 to allow for acclimatization (Step 2). The hair tress was then rinsed with water (approximately 40°C) for 30 seconds (Rinsing Step). Immediately thereafter, the hair tress was dried with cold air from a hair dryer for 15 minutes (Drying Step). The dried hair tress was measured and evaluated using the above methods. Furthermore, the improvement in hair dyeability was evaluated by determining the difference in ΔE compared to the following Comparative Example 11, in which Agent B was not applied. The results are shown in Table 4.

[0269] In addition, the compounding amounts (mass %) described in Table 4 are all amounts of active ingredients, and the total of Agent A and Agent B is 100 mass %.

[0270] Comparative Example 10

[0271] The hair dyeing treatment, measurement, and evaluation were carried out in the same manner as in Examples 5 to 8, except that the component (b) was not added to the agent B. The results are shown in Table 4.

[0272] Comparative Example 11

[0273] The hair dyeing treatment, measurement, and evaluation were performed in the same manner as in Examples 5 to 8, except that the step of applying Agent B (Step 2) was not performed. The results are shown in Table 4.

[0274] [Table 4]

[0275]

[0276] The components described in Tables 1 to 4 are as follows.

[0277] (a1) 5,6-dihydroxyindole and 5,6-dihydroxyindole-2-carboxylic acid mixture: A mixture produced by the method described in Japanese Patent No. 5570161 was used. The molar ratio of 5,6-dihydroxyindole to 5,6-dihydroxyindole-2-carboxylic acid was 90:10 (hereinafter sometimes referred to as "DHI"). Furthermore, a 1% by mass solution of (a1) containing HO / ethanol = 4 / 1 (wt / wt) was prepared and added to Agent A.

[0278] (b) NaCl: Sodium chloride (grilling salt S: Nippon Salt Manufacturing Co., Ltd.)

[0279] (b) MgCl2·6H2O: magnesium chloride hexahydrate (Fujifilm Wako Pure Chemical Industries, Ltd.). The concentration of MgCl2 in Agent B was adjusted to the concentration shown in the table.

[0280] (b) (CH3COO)2Ca·H2O: calcium acetate monohydrate (Fujifilm Wako Pure Chemical Industries, Ltd.). The concentration of (CH3COO)2Ca in Agent B was adjusted to the concentrations shown in the table.

[0281] (b) K2SO4: Potassium sulfate (Fujifilm Wako Pure Chemical Industries, Ltd.)

[0282] Sodium laureth sulfate: (27% aqueous solution: manufactured by Kao Corporation, Emal 227-PH11)

[0283] As shown in Tables 1 to 4, the method of the present invention can achieve stable hair dyeing performance of the melanin precursor without damage due to oxidation, and further improve hair dyeing properties by a simple process.

[0284] Recipe Example 1

[0285] (a1) DHI 0.5%

[0286] (a2) Monoethanolamine 3%

[0287] Ascorbic acid 0.6%

[0288] Sodium sulfite 0.5%

[0289] Propylene glycol 2%

[0290] Quartamin 86W 1%

[0291] Nikkol BC-2 2%

[0292] Nikkol BC-40 2%

[0293] Kalcol 8098 3%

[0294] Kalcol 220-80 3%

[0295] 75% phosphoric acid (as needed)

[0296] Water balance

[0297] pH 10.2

[0298] ·Quartamin86W: Stearyltrimethylammonium chloride 28% aqueous solution (Kao Corporation)

[0299] Nikkol BC-2: Ceteth-2 (Nippon Surfactant Industries Co., Ltd.)

[0300] Nikkol BC-40: Ceteth-40 (Nippon Surfactant Industries Co., Ltd.)

[0301] ·Kalcol 8098: Stearyl alcohol (Kao Corporation)

[0302] ·Kalcol 220-80: Behenyl alcohol (Kao Corporation)

[0303] The components shown in Formulation Example 1 were blended and mixed until uniform to prepare Agent A. Hair was treated with Agent B prepared separately in the same manner as in Example 1. As a result, hair dyeing properties were better than when Agent B was not used.

[0304] Recipe Example 2

[0305] (a1) DHI 0.075%

[0306] (a2) Monoethanolamine 1%

[0307] Ascorbic acid 0.4%

[0308] Sodium sulfite 0.35%

[0309] Propylene glycol 2%

[0310] Quartamin 86W 3%

[0311] Nikkol BC-2 0.5%

[0312] Nikkol BC-40 1%

[0313] Kalcol 8098 2%

[0314] Kalcol 220-80 4%

[0315] 75% phosphoric acid (as needed)

[0316] Water balance

[0317] pH 10.2

[0318] ·Quartamin86W: Stearyltrimethylammonium chloride 28% aqueous solution (Kao Corporation)

[0319] Nikkol BC-2: Ceteth-2 (Nippon Surfactant Industries Co., Ltd.)

[0320] Nikkol BC-40: Ceteth-40 (Nippon Surfactant Industries Co., Ltd.)

[0321] ·Kalcol 8098: Stearyl alcohol (Kao Corporation)

[0322] ·Kalcol 220-80: Behenyl alcohol (Kao Corporation)

[0323] The components shown in Formulation Example 2 were blended and mixed until uniform to prepare Agent A. Hair was treated with Agent B prepared separately in the same manner as in Example 2. The results showed better hair dyeing properties compared to the case where Agent B was not used.

[0324] [Industrial Applicability]

[0325] According to the present invention, a hair dyeing method can be provided, which can achieve stable hair dyeing performance of a melanin precursor without damage due to oxidation by a simple process, thereby improving hair dyeing properties.

Claims

1. A hair dyeing method, wherein: The hair dyeing method comprises steps 1 and 2 in sequence, and does not comprise a step of rinsing hair between steps 1 and 2, but comprises a step of rinsing hair after step 2. Step 1: Applying Agent A to the hair. The pH value of the agent A is 8-11 and contains the following components (a1) and (a2): (a1) a compound represented by the following general formula (1) or a salt thereof, Wherein, the dotted line indicates the presence or absence of a π bond; R 1 represents a hydroxyl group or an acetoxy group; R 2 represents a hydrogen atom, or -COOR, wherein R is a hydrogen atom, a methyl group or an ethyl group; R 3 represents a hydrogen atom, an acetyl group, a methyl group or an ethyl group; (a2) alkali agent; Step 2: Applying Agent B to the hair. The B agent contains the following component (b): (b) an alkali metal salt or alkaline earth metal salt selected from organic acid salts or inorganic salts having 6 or less carbon atoms.

2. The hair dyeing method according to claim 1, wherein The component (b) is one or more selected from the group consisting of chlorides, carboxylates, sulfates, and carbonates of sodium, potassium, calcium, and magnesium.

3. The hair dyeing method according to claim 1 or 2, wherein: The content of the component (a1) in the agent A is 0.05 to 1.0% by mass.

4. The hair dyeing method according to any one of claims 1 to 3, wherein In the step 2, the agent B is applied to the hair at a bath ratio of 1:0.0001 or greater, where the bath ratio is the dry mass of the hair: the mass of the component (b).

5. The hair dyeing method according to any one of claims 1 to 4, wherein The component (a2) contains one or more selected from ammonia and alkanolamines.

6. The hair dyeing method according to any one of claims 1 to 5, wherein The agent A and the agent B do not contain an oxidizing agent.

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