JP6853030B2 - Surface treatment liquid and hydrophilization treatment method - Google Patents

Description

The present invention relates to a surface treatment liquid and a method for hydrophilizing a body to be treated using the surface treatment liquid.

Conventionally, various surface treatment liquids have been used to modify the surface properties of various articles. Among the surface modifications, there is a great demand for hydrophilization of the surface of articles, and many chemicals and surface treatment liquids for hydrophilization have been proposed.

Regarding such a chemical for surface treatment, for example, at least an acrylamide monomer and a siloxy group-containing mono (meth) acrylate monomer having a specific skeleton are copolymerized as a surface conditioner capable of imparting hydrophilicity and antifouling property to the film surface. A copolymer having a weight average molecular weight of 1500 to 50,000 has been proposed (Patent Document 1).

Japanese Patent No. 5347523

However, when the hydrophilization treatment is performed using the surface conditioner described in Patent Document 1, even if the surface of the object to be treated is treated with a solution containing only the surface conditioner, the surface conditioner is the object to be treated. It is difficult to adhere to the surface and it is difficult to obtain the desired hydrophilic effect.
Therefore, in Patent Document 1, a liquid obtained by blending a solution of a surface conditioner with a resin such as an acrylic resin, a polyester resin, a urethane resin, an alkyd resin, an epoxy resin, or a polyamine resin as a film-forming component is used as a surface treatment liquid. ing.

When a surface treatment liquid containing the surface conditioner described in Patent Document 1 and a film-forming component is used, the surface of the object to be treated is covered with a film containing a resin, so that good hydrophilicity can be achieved. However, even the useful surface properties of the object to be treated are impaired.

The present invention has been made in view of the above problems, and is a surface treatment liquid capable of making the surface of the object to be treated good hydrophilic or hydrophobic even if it does not contain a film-forming resin. An object of the present invention is to provide a hydrophilization treatment method using the surface treatment liquid.

The present inventors have added (A) resin, anionic group and / or to a surface treatment liquid for hydrophilization treatment containing (A) resin, (B) ionic compound, and (S) water-containing solvent. We have found that the above problems can be solved by adding a water-soluble resin having a cationic group and adding a water-soluble non-polymer compound as the (B) ionic compound, and have completed the present invention. Specifically, the present invention provides the following.

A first aspect of the present invention comprises (A) a resin, (B) an ionic compound, and (S) a water-containing solvent.
(A) The resin is a water-soluble resin having an anionic group and / or a cationic group.
(B) The ionic compound is a water-soluble non-polymer compound, which is a surface treatment liquid used for hydrophilizing the surface of the object to be treated.

A second aspect of the present invention is a method for hydrophilizing the surface of another surface to be treated, which comprises applying the surface treatment liquid according to the first aspect to the surface of the object to be treated.

According to the present invention, a surface treatment liquid capable of performing good hydrophilicity or hydrophobicity on the surface of an object to be treated without containing a film-forming resin, and hydrophilization using the surface treatment liquid. A processing method and can be provided.

≪Surface treatment liquid≫
The surface treatment liquid contains (A) a resin, (B) an ionic compound, and (S) a water-containing solvent. Such a surface treatment liquid is used for hydrophilizing the surface of the object to be treated.
The resin (A) is a water-soluble resin having an anionic group and / or a cationic group.
The (B) ionic compound is a water-soluble non-polymer compound.
Hereinafter, essential or arbitrary components contained in the surface treatment liquid will be described.

<(A) resin>
The surface treatment liquid contains the resin (A) as a component for obtaining the desired surface treatment effect. The resin (A) has an anionic group and / or a cationic group. By having an anionic group and / or a cationic group, the resin (A) adheres to the surface of the object to be treated and makes it hydrophilic.

The resin (A) has a functional group I which is one or more groups selected from the group consisting of a hydroxyl group, a cyano group and a carboxy group, and a functional group II which is a hydrophilic group other than the functional group I. , Functional group II preferably contains an anionic group and / or a cationic group.
In this case, when the functional group II contains one or more groups selected from a hydroxyl group, a cyano group, and a carboxy group, the resin (A) does not have to have the functional group I.
The hydrophilic group containing the hydroxyl group and the carboxy group includes the hydroxyl group itself and the carboxy group itself.

When the resin (A) has a functional group I which is one or more groups selected from the group consisting of a hydroxyl group, a cyano group, and a carboxy group, the resin (A) adheres better to the surface of the object to be treated. It's easy to do.

The type of the resin (A) is not particularly limited as long as the resin (A) can be dissolved in the water-containing solvent (S). Examples of the resin (A) include (meth) acrylic resin, novolak resin, polyester resin, polyamide resin, polyimide resin, polyamideimide resin, silicone resin and the like.
Among these resins, a (meth) acrylic resin is preferable because it is easy to introduce a functional group and adjust the content ratio of a unit having a functional group.

(Anionic group and cationic group)
The resin (A) essentially has an anionic group and / or a cationic group. (A) Anionic and / or cationic groups in the resin provide hydrophilicity to the object to be treated.

The cationic group does not have to be a functional group consisting of a cation and a counter anion, and is not particularly limited as long as it is a functional group that can be cationized. The cation derived from the cationic group is preferably a cation containing ^{, for example, N +} , C ⁺ , B ⁺ , P ^+, etc., and more preferably a cation containing ^{N +.}
As the cationic group, a cyclic or acyclic amino group or a quaternary ammonium base is preferable because the resin (A) is easily available and a good surface treatment effect can be easily obtained.

As the resin (A), a polymer of a monomer having an unsaturated double bond is preferable. In such a case, the polymer preferably contains a structural unit derived from the compound represented by the following formula (a2) as a structural unit having a cationic group.
CH ₂ = CR ^2- (CO) _a- R ³ ... (a2)
(In the formula (a2), R ² is a hydrogen atom or a methyl group, R ³ is a group represented by -Y-R ^4- R ⁵ or an amino group, and Y is -O- or-. NH-, R ⁴ is a divalent organic group which may have a substituent, and R ⁵ is an amino group which may be substituted with a hydrocarbon group having 1 to 6 carbon atoms, or -N. It is a quaternary ammonium base represented by ⁺ R ⁶ R ⁷ R ⁸ · Z ^{− , and R 6} , R ⁷ and R ⁸ are independently hydrogen atoms or hydrocarbon groups having 1 to 6 carbon atoms, respectively. Yes, Z ⁻ is a counter anion, and a is 0 or 1.)

In the above formula (a2), when R ³ is a group represented by -Y-R ^4- R ^{5 , R 4} is a divalent organic group which may have a substituent. The divalent organic group is not particularly limited, but a divalent hydrocarbon group is preferable. The number of carbon atoms of the divalent hydrocarbon group is not particularly limited as long as the object of the present invention is not impaired. (A) Since the resin can be easily obtained and prepared, when R ⁴ is a divalent hydrocarbon group, the number of carbon atoms of the divalent hydrocarbon group is preferably 1 to 20, preferably 1 to 12. More preferably, 1 to 10 is particularly preferable, and 1 to 6 is most preferable.

The ^{divalent hydrocarbon group as R 4} may be an aliphatic group, an aromatic group, or a hydrocarbon group containing an aliphatic portion and an aromatic portion. When the divalent hydrocarbon group is an aliphatic group, the aliphatic group may be a saturated aliphatic group or an unsaturated aliphatic group. Further, the structure of the aliphatic group may be linear, branched, cyclic, or a combination of these structures.

As preferable specific examples of R ⁴ are methylene, ethane-1,2-diyl group, ethane-1,1-diyl group, propane-1,3-diyl, propane-1,1-diyl group, propane -2,2-diyl group, n-butane-1,4-diyl group, n-pentane-1,5-diyl group, n-hexane-1,6-diyl group, n-heptane-1,7-diyl group Group, n-octane-1,8-diyl group, n-nonan-1,9-diyl group, n-decane-1,10-diyl group, o-phenylene group, m-phenylene group, p-phenylene group, Examples thereof include naphthalene-2,6-diyl group, naphthalene-2,7-diyl group, naphthalene-1,4-diyl group, biphenyl-4,4'-diyl group and the like.

If the divalent hydrocarbon group as R ⁴ has a substituent, the examples of the substituent include a hydroxyl group, an alkoxy group having 1 to 6 carbon atoms, an aliphatic acyl group having from 2 to 6 carbon atoms, a halogen atom, Examples thereof include a nitro group and a cyano group.

When R ⁵ is an amino group which may be substituted with a hydrocarbon group having 1 to 6 carbon atoms, suitable specific examples thereof include an amino group, a methylamino group, an ethylamino group and an n-propylamino group. , Isopropylamino group, n-butylamino group, n-pentylamino group, n-hexylamino group, phenylamino group, dimethylamino group, diethylamino group, di-n-propylamino group, diisopropylamino group, di-n- Examples thereof include a butylamino group, a din-pentylamino group, a din-hexylamino group, and a diphenylamino group.

When R ⁵ is a quaternary ammonium base represented by ^{−N +} R ⁶ R ⁷ R ⁸ · Z ^{− , R 6} , R ⁷ and R ⁸ are independently hydrogen atoms or 1 to 1 carbon atoms, respectively. It is a hydrocarbon group of 6 and Z ⁻ is a counter anion.
Preferable examples of the hydrocarbon group having 1 to 6 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an n-pentyl group, an n-hexyl group, and a phenyl group. Can be mentioned.
The counter anion as Z ⁻ is not particularly limited as long as it is a monovalent anion, and a halide ion is preferable. Preferable examples of the halide ion include chloride ion, bromide ion, and iodide ion.

Preferable specific examples of the structural unit derived from the compound represented by the above-described formula (a2) include the following structural units a2-1 to a2-24. Among these structural units, the structural units a2-1 to a2-4, a2-17, and a2-18 are easy to obtain because the monomer compound can be easily obtained and a good surface treatment effect can be easily obtained. Is preferable.

The anionic group does not have to be a functional group composed of an anion and a counter cation, and is not particularly limited as long as it is a functional group that can be anionized.
Anionic groups are typically functional groups that exhibit Bronsted acidity. Preferable examples of the functional group exhibiting Bronsted acidity include a carboxy group, a sulfonic acid group, a sulfinic acid group, a phosphonic acid group, a phosphinic acid group, and a phenolic hydroxyl group.

These Bronsted acidic groups may form salts with counter cations. The counter cation is not particularly limited, and may be an organic cation or an inorganic cation such as a metal ion, and a metal ion is preferable. As the metal ion, an alkali metal ion is preferable, and for example, Li +, Na +, K +, and Sr + are preferable.

As the resin (A), a polymer of a monomer having an unsaturated double bond is preferable. In such a case, the polymer preferably contains a structural unit derived from the compound represented by the following formula (a3) as a structural unit having an anionic group.
CH ₂ = CR ^2- (CO) _b- R ⁹ ... (a3)
(In the formula (a3), R ² is a hydrogen atom or a methyl group, R ⁹ is a hydroxyl group or ^{a group represented by -A-R 10-} R ¹¹ , and A is -O- or -NH. -, R ¹⁰ is a divalent organic group which may have a substituent, R ¹¹ is a blended acidic group, b is 0 or 1, but b is 0. R ⁹ is not a hydroxyl group.)

In the above formula (a3), when R ⁹ is a group represented by -A-R ^10- R ^{11 , R 10} is a divalent organic group which may have a substituent. The divalent organic group is not particularly limited, but a divalent hydrocarbon group is preferable. The number of carbon atoms of the divalent hydrocarbon group is not particularly limited as long as the object of the present invention is not impaired. (A) Since the resin can be easily obtained and prepared, when R ¹⁰ is a divalent hydrocarbon group, the number of carbon atoms of the divalent hydrocarbon group is preferably 1 to 20, preferably 1 to 12. More preferably, 1 to 10 is particularly preferable, and 1 to 6 is most preferable.

The ^{divalent hydrocarbon group as R 10} may be an aliphatic group, an aromatic group, or a hydrocarbon group containing an aliphatic portion and an aromatic portion. When the divalent hydrocarbon group is an aliphatic group, the aliphatic group may be a saturated aliphatic group or an unsaturated aliphatic group. Further, the structure of the aliphatic group may be linear, branched, cyclic, or a combination of these structures.

Preferable specific examples of R ¹⁰ include methylene group, ethane-1,2-diyl group, ethane-1,1-diyl group, propane-1,3-diyl group, propane-1,1-diyl group and propane. -2,2-diyl group, n-butane-1,4-diyl group, n-pentane-1,5-diyl group, n-hexane-1,6-diyl group, n-heptane-1,7-diyl group Group, n-octane-1,8-diyl group, n-nonan-1,9-diyl group, n-decane-1,10-diyl group, o-phenylene group, m-phenylene group, p-phenylene group, Examples thereof include naphthalene-2,6-diyl group, naphthalene-2,7-diyl group, naphthalene-1,4-diyl group, biphenyl-4,4'-diyl group and the like.

When the ^{divalent hydrocarbon group as R 10} has a substituent, the substituents include a hydroxyl group, an alkoxy group having 1 to 6 carbon atoms, an aliphatic acyl group having 2 to 6 carbon atoms, and a halogen atom. Examples thereof include a nitro group and a cyano group.

The blended acidic group as R ¹¹ is preferably a carboxy group, a sulfonic acid group, a sulfinic acid group, a phosphonic acid group, a phosphinic acid group, and a phenolic hydroxyl group, preferably a carboxy group, a sulfonic acid group, a phosphonic acid group, and a phenol. A sex hydroxyl group is more preferable.

When R ¹¹ is not a phenolic hydroxyl group, the following groups are preferable as represented by ^{−R 10} −R ^11. In the following structural formula, R ¹¹ is a Bronsted acidic group other than the phenolic hydroxyl group.

Preferable specific examples of the structural unit derived from the compound represented by the above-described formula (a3) include the following structural units a3-1 to a3-20. Among these structural units, the structural units a3-1 to a3-10, a3-19, and a3-20 are easy to obtain because the monomer compound can be easily obtained and a good surface treatment effect can be easily obtained. Is preferable.

The amount of anionic group and / or cationic group in the resin (A) is not particularly limited as long as the object of the present invention is not impaired.
The molar ratio of the structural unit having an anionic group and / or the cationic group in all the structural units contained in the resin (A) is preferably 50 to 99.9 mol%, more preferably 60 to 99 mol%. , 70-99 mol% is particularly preferred.

(Functional group I)
The resin (A) preferably has a functional group I, which is one or more groups selected from the group consisting of a hydroxyl group, a cyano group, and a carboxy group. In this case, the resin (A) tends to adhere better to the surface of the object to be treated.

As the resin (A), a polymer of a monomer having an unsaturated double bond is preferable. In such a case, the polymer preferably contains a structural unit derived from the compound represented by the following formula (a4) as the structural unit having the functional group I.
CH ₂ = CR ^2- (R ¹² ) _c- CO-R ¹³ ... (a4)
(In formula (a4), R ² is a hydrogen atom or a methyl group, R ¹² is a divalent hydrocarbon group, c is 0 or 1, and R ¹³ is -OH, -OR ¹⁴ , Or -NH-R ¹⁴ , where R ¹⁴ is a hydrocarbon group substituted with one or more functional groups selected from the group consisting of hydroxyl groups, cyano groups, and carboxy groups.)

In the above formula (a4), R ¹² is a divalent hydrocarbon group. The number of carbon atoms of the divalent hydrocarbon group is not particularly limited as long as the object of the present invention is not impaired. (A) Since the resin can be easily obtained and prepared ^{, the number of carbon atoms of the divalent hydrocarbon group as R 12} is preferably 1 to 20, more preferably 1 to 12, and particularly preferably 1 to 10. , 1 to 6 are most preferable.

The ^{divalent hydrocarbon group as R 12} may be an aliphatic group, an aromatic group, or a hydrocarbon group containing an aliphatic portion and an aromatic portion. When the divalent hydrocarbon group is an aliphatic group, the aliphatic group may be a saturated aliphatic group or an unsaturated aliphatic group. Further, the structure of the aliphatic group may be linear, branched, cyclic, or a combination of these structures.

As preferable specific examples of R ¹² are methylene, ethane-1,2-diyl, ethane-1,1-diyl group, propane-1,3-diyl, propane-1,1-diyl group, propane -2,2-diyl group, n-butane-1,4-diyl group, n-pentane-1,5-diyl group, n-hexane-1,6-diyl group, n-heptane-1,7-diyl group Group, n-octane-1,8-diyl group, n-nonan-1,9-diyl group, n-decane-1,10-diyl group, o-phenylene group, m-phenylene group, p-phenylene group, Examples thereof include naphthalene-2,6-diyl group, naphthalene-2,7-diyl group, naphthalene-1,4-diyl group, biphenyl-4,4'-diyl group and the like.

R ¹³ was -OH, -OR ¹⁴ or -NH-R ¹⁴ , where R ¹⁴ was substituted with one or more functional groups selected from the group consisting of hydroxyl groups, cyano groups, and carboxy groups. It is a hydrocarbon group.
The ^{hydrocarbon group constituting the main skeleton of the group of R 14} may be a linear, branched or cyclic aliphatic group, or may be an aromatic hydrocarbon group.
The number of carbon atoms of the linear, branched, or cyclic aliphatic group is preferably 1 to 20, and more preferably 1 to 12.
Preferable examples of linear or branched aliphatic groups are methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group and tert-butyl group. , N-Pentyl group, Isopentyl group, Neopentyl group, sec-Pentyl group, tert-Pentyl group, n-Hexyl group, n-Heptyl group, n-octyl group, n-nonyl group, n-decyl group and the like. ..
Preferable examples of the cyclic aliphatic group include cyclooctyl groups such as cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, and cyclooctyl group, and adamantan, norbornan, isobornan, tricyclodecane, and the like. Examples thereof include a group obtained by removing one hydrogen atom from a polycycloalkane such as tetracyclododecane, and a group obtained by removing one hydrogen atom from a C1-C4 alkyl substituent of these polycycloalkanes.
Preferable examples of the aromatic hydrocarbon group include a phenyl group, a naphthyl group, an anthranyl group, a phenanthrenyl group, a biphenylyl group and the like. The aromatic hydrocarbon group may be substituted with a C1-C4 alkyl group such as a methyl group or an ethyl group.

As a particularly preferable specific example of the structural unit derived from the compound represented by the formula (a4), the following structural units a4-1 to a4-9 can be mentioned. Among the units a4-1 to a4-9 below, the structural units a4-1 to a4-4 are more preferable.

The amount of the functional group I in the resin (A) is not particularly limited as long as the object of the present invention is not impaired.
The molar ratio of the structural unit having the functional group I in all the structural units contained in the resin (A) is preferably 0.1 to 50 mol%, more preferably 1 to 20 mol%, and preferably 1 to 15 mol%. Especially preferable.

(Functional group II)
Functional group II is a hydrophilic group. The hydrophilic group is not particularly limited as long as it is a functional group conventionally recognized as a hydrophilic group by those skilled in the art, and can be appropriately selected from among them.

Specific examples of the hydrophilic group include a polyoxyalkylene group (for example, a polyoxyethylene group, a polyoxypropylene group, a polyoxyalkylene group in which an oxyethylene group and an oxypropylene group are blocked or randomly bonded), an amino group, and 4 Examples thereof include a higher ammonium base, a carboxy group, a hydroxyl group, a phosphonic acid group, a phosphinic acid group, and a sulfonic acid group. Further, an organic group containing these groups is also preferable as a hydrophilic group.

In terms of the excellent hydrophilicity effect, the hydrophilic group includes the following formula (a1):
-NH-R ¹ ... (a1)
(In the formula (a1), R ¹ is an alkyl group having 1 to 4 carbon atoms substituted with one or more groups selected from the group consisting of an amino group, a sulfonic acid group, a phosphonic acid group, and a hydroxyl group, or an alkyl group having 1 to 4 carbon atoms. It is a hydrogen atom.)
The group represented by is preferable.
For R ¹ , the amino group corresponds to a cationic group, and the sulfonic acid group and the phosphonic acid group correspond to an anionic group. Of the hydroxyl groups, phenolic hydroxyl groups correspond to anionic groups.

Specific examples of the hydrophilic group represented by the formula (a1) include an amino group and a group represented by the following formula.

Among the specific examples of the hydrophilic group represented by the above formula (A1), the following groups can be mentioned as more preferable groups.

Among the specific examples of the hydrophilic group represented by the above formula (a1), the following groups are particularly preferable.

As described above, as the resin (A), a polymer of a monomer having an unsaturated double bond such as a (meth) acrylic resin is preferable.
In this case, the resin (A) has the following formula (a5):
CH ₂ = CR ^2- CO-NH-R ¹ ... (a5)
(In the formula (a5), R ¹ is an alkyl group having 1 to 4 carbon atoms substituted with one or more groups selected from the group consisting of an amino group, a sulfonic acid group, a phosphonic acid group, and a hydroxyl group, or an alkyl group having 1 to 4 carbon atoms. It is a hydrogen atom, and R ² is a hydrogen atom or a methyl group.)
It is preferable to contain a structural unit derived from the monomer represented by.

In the formula (a5), R ¹ is as described above.

A particularly preferable specific example of the unit having a hydrophilic group derived from the monomer represented by the formula (a5) is the unit of the following a5-1 to a5-5. Among the following units, the units a5-1 to a5-4 are more preferable.

The molar ratio of the structural unit having the functional group II to all the structural units contained in the resin (A) is preferably 50 to 99.9 mol%, more preferably 60 to 99 mol%, and 70 to 99 mol%. Especially preferable.
However, when the structural unit having a functional group II contains any one of a hydroxyl group, a cyano group and a carboxy group, the ratio of the structural unit having a functional group II contained in the polymer may be 100 mol%. ..

The resin (A) may contain a structural unit that does not have an anionic group, a cationic group, a functional group I, and a functional group II.

When the resin (A) is a polymer of a monomer having an unsaturated bond, examples of the compound that gives a structural unit that does not have an anionic group, a cationic group, a functional group I, and a functional group II include, for example. Methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, -n-propyl (meth) acrylate, -n-butyl (meth) acrylate, isobutyl (meth) acrylate, (meth) ) Acrylic acid-tert-butyl, (meth) acrylate-n-pentyl, (meth) acrylate isopentyl, (meth) acrylate phenyl, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N- n-propyl (meth) acrylamide, N-isopropyl (meth) acrylamide, Nn-butyl (meth) acrylamide, Nn-pentyl (meth) acrylamide, N-isopentyl (meth) acrylamide, N-phenyl (meth) Acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-di-n-propyl (meth) acrylamide, N, N-di-n-butyl (meth) acrylamide, Examples thereof include N, N-di-n-pentyl (meth) acrylamide, styrene, α-methylstyrene, β-methylstyrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, and chlorostyrene.

The mass average molecular weight of the resin (A) is not particularly limited as long as it does not impair the object of the present invention. The mass average molecular weight of the resin (A) is preferably 50,000 to 3,000,000, preferably 50,000 to 2,000,000, from the viewpoint of solubility in the surface treatment solution and easy acquisition of the desired surface treatment effect. Is more preferable.
The mass average molecular weight of the resin (A) is a polystyrene-equivalent molecular weight measured by GPC.

The content of the resin (A) in the surface treatment liquid is not particularly limited as long as it does not impair the object of the present invention. The content of the (A) resin in the surface treatment liquid is 0.1 to 10% by mass because it is easy to obtain a desired surface treatment effect while preventing excessive adhesion of the (A) resin to the surface of the object to be treated. Is preferable, 0.2 to 7% by mass is more preferable, and 0.5 to 5% by mass is particularly preferable.

<(B) Ionic compound>
(B) The ionic compound may be a salt, an anionic compound that can be anionized, or a cationic compound that can be cationized. The (B) ionic compound may be an organic compound or an inorganic compound, but is preferably an organic compound from the viewpoint of (A) affinity with the resin and the like.

The ionic compound (B) is preferably a compound having one or more selected from a carboxy group, a phosphonic acid group, and a quaternary ammonium group because it is easy to obtain a good hydrophilization effect.

The molecular weight of the ionic compound (B) is preferably 500 or less, more preferably 400 or less, and particularly preferably 300 or less.
When a low molecular weight (B) ionic compound having a molecular weight within such a range is used, the (B) ionic compound easily adheres uniformly to the surface of the object to be treated, and a good hydrophilization effect is easily obtained. ..

(B) The ionic compound may be an aromatic compound containing an aromatic group or a non-aromatic compound containing no aromatic group. From the viewpoint of solubility in the surface treatment solution, the (B) ionic compound is preferably a non-aromatic compound. The non-aromatic compound may be an organic compound (aliphatic compound) or an inorganic compound.
Specific examples of the (B) ionic compound include ammonia, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, ethanolamine, diethanolamine, triethanolamine, 2-aminoethoxyethanol, ethylenediamine, pyrrolidine, piperazin, and morpholin. , Colin, and cationic compounds such as salts thereof; ethane-1,1-diphosphonic acid, ethane-1,1,2-triphosphonic acid, 1-hydroxyethane-1,1-diphosphonic acid, 1,2-carboxy. -1,2-phosphonoetan, 2-phosphonoetan-1-sulfonic acid, 2-phosphonobutane-1,2,4-tricarboxylic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, fumaric acid, maleic acid, Anionic compounds such as malic acid, citric acid, tartaric acid, aconitic acid, and salts thereof; amphoteric compounds such as betaine (eg, trimethylglycine), nitrilotris (methylenephosphonic acid), ethylenediaminetetraacetic acid;

（式（ｂ１）及び式（ｂ２）中、Ｒ^ｂ１、Ｒ^ｂ２、及びＲ^ｂ３は、それぞれ独立に水酸基又はハロゲン原子で置換されていてもよい炭素原子数１〜３のアルキル基であり、Ｒ^ｂ４は水酸基又はハロゲン原子で置換されていてもよい炭素原子数１〜３のアルキレン基である。
式（ｂ２）中、Ｘ⁻は１価のアニオンである。
式（ｂ３）中、Ｒ^ｂ５、Ｒ^ｂ６、Ｒ^ｂ７、及びＲ^ｂ８は、それぞれ独立に、単結合であるか、水酸基又はハロゲン原子で置換されていてもよい炭素原子数１〜３のアルキレン基であり、Ｒ^ｂ９は水酸基又はホスホン酸基である。） As suitable compounds (B) an ionic compound, -COO ^- group, -SO ₃ ^- group, or -PO ₃ ^- anionic groups, such as groups, the same molecule and a quaternary ammonium group as cationic group An amphoteric compound (B) contained therein, a quaternary ammonium salt (Bb) in which a nitrogen atom is substituted with at least one hydroxyl group-containing organic group, and an aliphatic polycarboxylic acid compound having two or more carboxy groups (B). -C) can be mentioned.
Preferred examples of the amphoteric compound (BA) include a compound represented by the following formula (b1). A preferable example of the quaternary ammonium salt (Bb) is a compound represented by the following formula (b2). Preferred examples of the aliphatic polycarboxylic acid compound (B-c) include a compound represented by the following formula (b3).

(In formulas (b1) and (b2), R ^b1 , R ^b2 , and R ^b3 are alkyl groups having 1 to 3 carbon atoms which may be independently substituted with hydroxyl groups or halogen atoms, respectively, and R ^b4 is an alkylene group having 1 to 3 carbon atoms which may be substituted with a hydroxyl group or a halogen atom.
In formula (b2), X ⁻ is a monovalent anion.
In formula (b3), R ^b5 , R ^b6 , R ^b7 , and R ^b8 are independently single-bonded or alkylene groups having 1 to 3 carbon atoms which may be substituted with hydroxyl groups or halogen atoms. R ^b9 is a hydroxyl group or a phosphonic acid group. )

In the formula (b1), R ^b1 , R ^b2 , and R ^b3 are alkyl groups having 1 to 3 carbon atoms which may be substituted with hydroxyl groups or halogen atoms. Examples of the halogen atom as the substituent include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
As R ^b1 , R ^b2 , and R ^b3 , an unsubstituted alkyl group is preferable. Suitable specific examples of R ^b1 , R ^b2 , and R ^b3 are methyl, ethyl, n-propyl, and isopropyl groups.

In the formula (b1), R ^b4 is an alkylene group having 1 to 3 carbon atoms which may be substituted with a hydroxyl group or a halogen atom. Examples of the halogen atom as the substituent include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
As R ^b4 , an unsubstituted alkylene group is preferable. Suitable specific examples of R ^b4 are methylene group, ethane-1,2-diyl group, ethane-1,1-diyl group, propane-1,3-diyl group, propane-1,1-diyl group, propane-. It is a 1,2-diyl group and a propane-2,2-diyl group, preferably a methylene group, an ethane-1,2-diyl group, and a propane-1,3-diyl group, more preferably a methylene group.

The compound represented by the formula (b1) is preferably so-called betaine, and specific examples thereof include trimethylglycine.

In the formula (b2), R ^b1 , R ^b2 , R ^b3 , and R ^b4 are as described in the formula (b1). ^{R b4} in the formula (b2) is preferably a methylene group, an ethane-1,2-diyl group, and a propane-1,3-diyl group, more preferably an ethane-1,2-diyl group.

^{X −} in the formula (b2) is a monovalent anion, and is not particularly limited as long as it does not impair the object of the present invention. Suitable anions include hydrogen ion, chloride ion, bromide ion, iodide ion, hydroxide ion, tartrate ion and the like.

Preferable specific examples of the compound represented by the formula (b2) include choline hydroxide, choline chloride, and choline bitartrate.

In formula (b3), R ^b5 , R ^b6 , R ^b7 , and R ^b8 are independently single-bonded or alkylene groups having 1 to 3 carbon atoms which may be substituted with hydroxyl groups or halogen atoms. Is. Examples of the halogen atom as the substituent include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.
As R ^b5 , R ^b6 , R ^b7 , and R ^b8 , a single bond or an unsubstituted alkylene group is preferable. Suitable specific examples of the unsubstituted alkylene group are methylene group, ethane-1,2-diyl group, ethane-1,1-diyl group, propane-1,3-diyl group, propane-1,1-diyl group. , Propan-1,2-diyl group, and propane-2,2-diyl group, preferably methylene group, ethane-1,2-diyl group, and propane-1,3-diyl group, preferably methylene group, and The ethane-1,2-diyl group is more preferred.

Preferable specific examples of the compound represented by the formula (b3) include citric acid and 2-phosphonobutane-1,2,4-tricarboxylic acid.

The content of the (B) ionic compound in the surface treatment liquid is not particularly limited as long as it does not impair the object of the present invention. The content of the (B) ionic compound in the surface treatment liquid is preferably 0.1 to 20% by mass, preferably 0.3 to 20% by mass, based on the mass of the (A) resin, because the desired hydrophilization effect can be easily obtained. 15% by mass is more preferable, and 0.5 to 10% by mass is particularly preferable.

<(C) Strong acid>
The surface treatment liquid may contain (C) a strong acid. (C) The pKa of the strong acid is 1 or less. In addition, pKa is a value in water.
The (C) strong acid promotes the adhesion or bond of the (A) resin to the surface of the object to be treated.
The type of (C) strong acid is not particularly limited as long as pKa is 1 or less. As the strong acid (C), two or more kinds of acids having a pKa of 1 or less can be used in combination.

Preferable examples of (C) strong acid are fluorinated aliphatic carboxylic acid (for example, trifluoroacetic acid), fluorosulfonic acid, alcan sulfonic acid having 1 to 30 carbon atoms (for example, methanesulfonic acid, dodecanesulfonic acid, etc.). , Aryl sulfonic acid (eg benzene sulfonic acid, p-toluene sulfonic acid, etc.), fluoroalcan sulfonic acid having 1 to 30 carbon atoms (eg trifluoromethane sulfonic acid, pentafluoroethane sulfonic acid, heptafluoropropane sulfonic acid, nonafluoro Butane sulfonic acid, undecafluoropentane sulfonic acid and tridecafluorohexane sulfonic acid), bissulfonylimide compound, cyclic sulfonylimide compound in which two sulfonyl groups are linked by a fluoroalkylene group, and N-acylfluoroalkane sulfonic acid amide. And so on.

When these (C) strong acids contain a fluoroalkyl group or a fluoroalkylene group, these groups may be a partially fluorinated fluoroalkyl group or a fluoroalkylene group and are completely fluorinated. It may be a perfluoroalkyl group or a perfluoroalkylene group.

Among these (C) strong acids, fluorosulfonic acid, alkanesulfonic acid having 1 to 30 carbon atoms, fluoroalcansulfonic acid having 1 to 30 carbon atoms, bis (fluoroalkylsulfonyl) imide acid, and two sulfonyl groups. Cyclic sulfonic acid, in which is linked with a fluoroalkylene group, and N-acylfluoroalcan sulfonic acid amide are preferable, and fluoroalcan sulfonic acid having 1 to 30 carbon atoms, a bissulfonylimide compound, and two sulfonyl groups are fluoroalkylene groups. Cyclic sulfonylimide compounds linked with, and N-acylfluoroalcan sulfonic acid amide are preferred.

As the fluoroalkane sulfonic acid having 1 to 30 carbon atoms, trifluoromethane sulfonic acid, pentafluoroethane sulfonic acid, heptafluoropropane sulfonic acid, nonafluorobutane sulfonic acid and the like are preferable.

式（Ｃ１）中、Ｘ^１及びＸ^２は、それぞれ独立に、少なくとも１つの電子吸引性基で置換された炭化水素基を表す。炭化水素基は、式（Ｃ１）で表される化合物の強酸性が損なわれない範囲で、電子吸引性基以外の種々の基で置換されていてもよい。Ｘ^１及びＸ^２の炭素原子数は、１〜２０が好ましく、１〜１０がより好ましく、１〜７が特に好ましい。
電子吸引性基で置換された炭化水素基としては、フッ素化アルキル基、ニトロ基を有するアリール基が好ましい。フッ素化アルキル基は、直鎖状でも、分岐鎖状でも、環状でもよい。フッ素化アルキル基は、完全にフッ素化されたパーフルオロアルキル基であるのが好ましい。ニトロ基を有するアリール基としては、ｏ−ニトロフェニル基、ｍ−ニトロフェニル基、及びｐ−ニトロフェニル基が好ましく、ｐ−ニトロフェニル基がより好ましい。 As the bissulfonylimide compound, the compound represented by the following formula (C1) is preferable.

In formula (C1), X ¹ and X ² each independently represent a hydrocarbon group substituted with at least one electron-withdrawing group. The hydrocarbon group may be substituted with various groups other than the electron-withdrawing group as long as the strong acidity of the compound represented by the formula (C1) is not impaired. The ^{number of carbon atoms of X 1} and X ² is preferably 1 to 20, more preferably 1 to 10, and particularly preferably 1 to 7.
As the hydrocarbon group substituted with the electron-withdrawing group, an alkyl fluorinated group and an aryl group having a nitro group are preferable. The fluorinated alkyl group may be linear, branched or cyclic. The fluorinated alkyl group is preferably a fully fluorinated perfluoroalkyl group. As the aryl group having a nitro group, an o-nitrophenyl group, an m-nitrophenyl group, and a p-nitrophenyl group are preferable, and a p-nitrophenyl group is more preferable.

Preferable specific examples of the compound represented by the formula (C1) include the compound of the following formula.

As the cyclic sulfonylimide compound in which two sulfonyl groups are linked by a fluoroalkylene group, a compound represented by the following formula (C2) is preferable.

Wherein (C2), X ³ represents a linear or branched alkylene group having at least one hydrogen atom is substituted with a fluorine atom. The number of carbon atoms of X ³ is 2-6, more preferably 3-5, most preferably 3.

Preferable specific examples of the compound represented by the formula (C2) include the compound of the following formula.

式（Ｃ３）中、Ｘ^４は、少なくとも１つの水素原子がフッ素原子で置換された直鎖状又は分岐状のアルキル基を表す。Ｘ^４の炭素原子数は、１〜１０が好ましく、１〜７がより好ましく、１〜３が特に好ましい。
Ｘ^５は、炭化水素基である。炭化水素基について、前述のＲ^１４の基の主骨格を構成する炭化水素基と同様である。 As the N-acylfluoroalkanesulfonic acid amide, a compound represented by the following formula (C3) is preferable.

Wherein (C3), X ⁴ represents a linear or branched alkyl group at least one hydrogen atom is substituted with a fluorine atom. The number of carbon atoms in X ⁴ are 1-10, more preferably 1-7, 1-3 are particularly preferred.
X ⁵ is a hydrocarbon group. For the hydrocarbon group, the same as the hydrocarbon group constituting the main skeleton of the group of the aforementioned R ^14.

Preferable specific examples of the compound represented by the formula (C3) include the compound of the following formula.

The content of the (C) strong acid in the surface treatment liquid is not particularly limited as long as the surface treatment can be performed satisfactorily. The content of (C) strong acid in the surface treatment liquid is preferably 0.1 to 20 parts by mass, more preferably 0.1 to 10 parts by mass, and 0.1 to 5 parts by mass with respect to 100 parts by mass of (A) resin. Parts by mass are particularly preferred.

<Other ingredients>
The surface treatment liquid may contain various components other than (A) resin, (B) ionic compound, (C) strong acid, and (S) water-containing solvent as long as the object of the present invention is not impaired. Examples of other components include colorants, surfactants, defoamers, viscosity modifiers, surfactants and the like.

<(S) Hydrous solvent>
The surface treatment liquid essentially contains (S) a water-containing solvent, and the (S) water-containing solvent may be water or an aqueous solution of an organic solvent.
The content of water in the (S) water-containing solvent is, for example, preferably 80% by mass or less, more preferably 50% by mass or less, and particularly preferably 10% by mass or less.

Examples of the organic solvent that the water-containing solvent may contain include, for example.
Alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, ethylene glycol, propylene glycol;
Sulfoxides such as dimethyl sulfoxide;
Sulfones such as dimethyl sulfone, diethyl sulfone, bis (2-hydroxyethyl) sulfone, tetramethylene sulfone;
Amides such as N, N-dimethylformamide, N-methylformamide, N, N-dimethylacetamide, N-methylacetamide, N, N-diethylacetamide;
Lactams such as N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-propyl-2-pyrrolidone, N-hydroxymethyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone;
Imidazolidinones such as 1,3-dimethyl-2-imidazolidinone, 1,3-diethyl-2-imidazolidinone, 1,3-diisopropyl-2-imidazolidinone;
Dialkyl glycol ethers such as dimethyl glycol, dimethyl diglycol, dimethyl triglycol, methyl ethyl diglycol, diethyl glycol, triethylene glycol butyl methyl ether;
Ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-n-propyl ether, ethylene glycol mono-n-butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, diethylene glycol mono-n- Butyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-n-butyl ether, dipropylene glycol monomethyl ether, di (Poly) alkylene glycol monoalkyl ethers such as propylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-n-butyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monoethyl ether;
(Poly) alkylene glycol monoalkyl ether acetates such as ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate;
Other ethers such as dimethyl ether, diethyl ether, methyl ethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, diisoamyl ether, diethylene glycol dimethyl ether, diethylene glycol methyl ethyl ether, diethylene glycol diethyl ether, tetrahydrofuran;
Lactyl alkyl esters such as methyl 2-hydroxypropionate and ethyl 2-hydroxypropionate; ethyl 2-hydroxy-2-methylpropionate, methyl 3-methoxypropionate, ethyl 3-methoxypropionate, 3-ethoxypropionic acid Methyl, ethyl 3-ethoxypropionate, ethyl ethoxyacetate, ethyl hydroxyacetate, methyl 2-hydroxy-3-methylbutanoate, 3-methyl-3-methoxybutyl acetate, 3-methyl-3-methoxybutyl propionate, acetic acid Ethyl, acetic acid-n-propyl, acetate-i-propyl, acetate-n-butyl, acetate-i-butyl, formate-n-pentyl, acetate-i-pentyl, propionate-n-butyl, ethyl butyrate, butyric acid Other esters such as -n-propyl, -i-propyl butyrate, -n-butyl butyrate, methyl pyruvate, ethyl pyruvate, -n-propyl pyruvate, methyl acetoacetate, ethyl acetoacetate, ethyl 2-oxobutanoate, etc. Kind;
Lactones such as β-propyrolactone, γ-butyrolactone, and δ-pentyrolactone;
And so on.
The above organic solvents also include water-insoluble organic solvents that do not mix freely with water. The water-insoluble organic solvent can be dissolved in the (S1) water-containing solvent by using it together with the water-soluble organic solvent.

<Preparation method of surface treatment liquid>
The method for preparing the surface treatment liquid is not particularly limited. The surface treatment liquid typically contains a predetermined amount of (A) resin, (B) ionic compound, (S) water-containing solvent, and (C) strong acid and other components, if necessary. It is prepared by mixing uniformly.

≪Hydrophilic treatment method≫
The hydrophilization treatment method using the surface treatment liquid described above usually includes application of the surface treatment liquid to the surface of the object to be treated. The method of applying the surface treatment liquid is not particularly limited. Specific examples of the coating method include a spin coating method, a spray method, a roller coating method, a dipping method and the like. When the object to be treated is a substrate, the spin coating method is preferable as the coating method because the surface of the substrate can be uniformly hydrophilized or hydrophobicized by uniformly applying the surface treatment liquid.

The material of the surface to which the surface treatment liquid of the object to be treated is applied is not particularly limited, and may be an organic material or an inorganic material.
Examples of the organic material include polyester resins such as PET resin and PBT resin, various nylons, polyimide resins, polyamide-imide resins, polyolefins such as polyethylene and polypropylene, polystyrenes, (meth) acrylic resins, and various resin materials such as polydimethylsiloxane. Can be mentioned.
Further, a photosensitive resin component contained in various resist materials and an alkali-soluble resin component are also preferable as the organic material.
Examples of the inorganic material include glass, silicon, and various metals such as copper, aluminum, iron, and tungsten. The metal may be an alloy.

The shape of the object to be processed is not particularly limited. The object to be processed may be a flat substrate, and may have a three-dimensional shape such as a spherical shape or a columnar shape. Further, the surface of the object to be treated may be smooth or may have regular or irregular irregularities.

After the surface treatment liquid is applied to the surface of the object to be treated, at least a part of the (S) water-containing solvent may be removed by heating the coating film, if necessary.

The portion of the object to be treated where the surface treatment liquid is applied may be rinsed if necessary. As described above, when the surface treatment liquid containing the resin (A) having a predetermined functional group is applied to the surface of the object to be treated, the resin (A) is satisfactorily adhered or bonded to the surface of the object to be treated.
However, a certain amount of the resin (A) that is not adhered to or bonded to the surface of the object to be treated is also present. Therefore, in order to reduce the influence of the resin (A) on the surface characteristics of the object to be treated, the resin (A) which is not adhered to or bonded to the surface of the object to be treated may be washed away by rinsing.

The surface treatment liquid contains (S) a water-containing solvent. Therefore, it is preferable to rinse with water. When the (S) water-containing solvent contains an organic solvent, it is also preferable to perform rinsing using an aqueous solution of the same organic solvent as the (S) water-containing solvent.

After applying the surface treatment liquid or rinsing, the surface of the object to be treated is dried as necessary to obtain a well-hydrophilized article.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

[Examples 1 to 9]
A solution was prepared by dissolving a resin having the following structure as the resin (A) in an aqueous ethanol solution at a concentration of 1% by mass. The ethanol concentration of the aqueous ethanol solution was 90% by mass.
In the following structural formula, the numerical value at the lower right of the parentheses in each structural unit represents the molar ratio (%) of each structural unit in the resin. The mass average molecular weight of the resin having the following structure is 800,000.

A surface treatment solution was obtained by dissolving the amount shown in Table 1 (mass% with respect to the amount of (A) resin) and the type of ionic compound in the obtained solution. The types of ionic compounds are as follows.
BI: 2-phosphonobutane-1,2,4-tricarboxylic acid B-II: 2-aminoethanol B-III: betaine anhydride B-IV: choline hydroxide

In Examples 1 to 9, a substrate having a surface made of polydimethylsiloxane was used as the object to be treated. The surface treatment liquid was dip-coated on the substrate. After dip coating, the substrate was dried at 80 ° C. for 5 minutes. The surface of the substrate after drying was rinsed with pure water. After rinsing, the surface of the substrate was dried by spraying nitrogen gas, and then the contact angle of water on the surface of the substrate after 2000 ms was measured. The measurement results are shown in Table 1.

[Comparative Example 1]
A surface treatment solution was obtained in the same manner as in Examples except that an ionic compound was not used.
Using the obtained surface treatment liquid, surface treatment of a substrate having a surface made of polydimethylsiloxane was performed in the same manner as in Examples, the surface of the substrate was dried, and then the contact angle of water on the surface of the substrate after 2000 ms was determined. It was measured. The measurement results are shown in Table 1.

According to Table 1, a water-soluble resin containing (A) a resin, (B) an ionic compound, and (S) a water-containing solvent, wherein the (A) resin has an anionic group and / or a cationic group. Therefore, it can be seen that the surface of the object to be treated can be satisfactorily hydrophilic by using a surface treatment liquid in which the (B) ionic compound is a water-soluble non-polymer compound.

Claims (9)

It contains (A) a resin, (B) an ionic compound, and (S) a water-containing solvent.
The resin (A) is a water-soluble resin having an anionic group and / or a cationic group, which is a polymer of a monomer having an unsaturated double bond, and is converted to polystyrene as measured by GPC. The mass average molecular weight is 50,000 to 3,000,000 .
(B) the ionic compound, Ri non-polymeric compound der water-soluble,
The ionic compound (B) is the following formula (b1), formula (b2), or formula (b3):

(In formulas (b1) and (b2), R ^b1 , R ^b2 , and R ^b3 are alkyl groups having 1 to 3 carbon atoms which may be independently substituted with hydroxyl groups or halogen atoms, respectively, and R ^b4 is an alkylene group having 1 to 3 carbon atoms which may be substituted with a hydroxyl group or a halogen atom.
In formula (b2), X ⁻ is a monovalent anion.
In formula (b3), R ^b5 , R ^b6 , R ^b7 , and R ^b8 are independently single-bonded or alkylene groups having 1 to 3 carbon atoms which may be substituted with hydroxyl groups or halogen atoms. R ^b9 is a hydroxyl group or a phosphonic acid group. )
Contains one or more compounds represented by
A surface treatment liquid used for hydrophilizing the surface of an object to be treated, wherein the water-containing solvent (S) is an aqueous solution of water or an organic solvent. (A) the resin, a hydroxyl group, which have a functional group I is one or more groups selected from the group consisting of cyano and carboxy groups, the surface treatment solution according to claim 1. The functional group I is based on the following formula (a4):
CH ₂ = CR ^2- (R ¹² ) _c- CO-R ¹³ ... (a4)
(In formula (a4), R ² is a hydrogen atom or a methyl group, R ¹² is a divalent hydrocarbon group, c is 0 or 1, and R ¹³ is -OH, -OR ¹⁴ , Or -NH-R ¹⁴ , where R ¹⁴ is a hydrocarbon group substituted with one or more functional groups selected from the group consisting of hydroxyl groups, cyano groups, and carboxy groups.)
The surface treatment liquid according to claim 2, which is derived from the monomer represented by. The resin (A) is based on the following formula (a1):
-NH-R ¹ ... (a1)
(In the formula (a1), R ¹ is an alkyl group having 1 to 4 carbon atoms substituted with one or more groups selected from the group consisting of an amino group, a sulfonic acid group, a phosphonic acid group, and a hydroxyl group, or an alkyl group having 1 to 4 carbon atoms. It is a hydrogen atom.)
The surface treatment liquid according to any one of claims 1 to 3, which has a group represented by. The resin (A) is based on the following formula (a5):
CH ₂ = CR ^2- CO-NH-R ¹ ... (a5)
(In the formula (a5), R ¹ is an alkyl group having 1 to 4 carbon atoms substituted with one or more groups selected from the group consisting of an amino group, a sulfonic acid group, a phosphonic acid group, and a hydroxyl group, or an alkyl group having 1 to 4 carbon atoms. It is a hydrogen atom, and R ² is a hydrogen atom or a methyl group.)
The surface treatment liquid according to any one of claims 1 to 4, which contains a structural unit derived from the monomer represented by. The surface treatment liquid according to any one of claims 1 to 5, further comprising (C) a strong acid having a pKa of 1 or less. The surface treatment solution according to any one of claims 1 to 6, wherein the ionic compound (B) has one or more selected from a carboxy group, a phosphonic acid group, and a quaternary ammonium group. The surface treatment solution according to any one of claims 1 to 7, wherein the ionic compound (B) has a molecular weight of 500 or less. A method for hydrophilizing the surface of an object to be treated, which comprises applying the surface treatment solution according to any one of claims 1 to 8 to the surface of the object to be treated.