JP7797320B2 - Liquid anti-fog coating agent - Google Patents

Description

The present invention relates to a liquid anti-fog coating agent.

Anti-fog coating agents are coating liquids that can be applied to the surface of an item to form an anti-fog film, preventing fogging on the surface. They are used in a variety of products, including automobile headlamps, camera lenses, face shields, and eyeglasses.

In particular, anti-fog coatings used on the inside of automobile headlamp covers (lenses) require long-term durability that is not affected by the external environment. In this case, it is important to not only prevent water marks caused by components leaching from the coating during condensation, but also to maintain anti-fog properties even after long-term environmental testing.

A variety of such anti-fog coating agents have been proposed to date. For example, a coating composition that imparts anti-reflection and anti-fog properties to a substrate having a surface onto which the coating composition is applied is known, and that contains a porous inorganic metal oxide and a surfactant containing at least one hydrophobic group and at least one hydrophilic anionic group (Patent Document 1).

An anti-fogging agent composition comprising a specific copolymer (A), a polyfunctional blocked isocyanate compound (B), and a surfactant (C) has also been proposed (Patent Document 2).

Furthermore, an anti-fog coating composition containing a colloidal silica mixture containing acidic elongated colloidal silica and pH-adjusting elongated colloidal silica is known (Patent Document 3).

Other known compositions include an anti-fog coating composition containing long-shaped colloidal silica and spherical colloidal silica (Patent Document 4), and an anti-fog coating composition containing long-shaped colloidal silica and a silane derivative compound mixture containing at least a silane derivative compound having a polyethylene glycol chain in its molecule and a silane derivative compound having an epoxy group in its molecule (Patent Document 5).

JP 2010-131651 Patent Publication No. 2016-169287 Patent Publication No. 2019-19253 International Publication WO2021/140931 International Publication WO2021/141044

As described in Patent Documents 4 and 5, in particular, the applicant of the present application has devised a new, highly hydrophilic coating film whose main component is colloidal silica, and has developed an anti-fogging agent that does not leave water marks and has excellent anti-fogging durability.

However, while these conventional technologies can provide satisfactory anti-fogging performance, there is still room for improvement in the appearance of the coating film.

In anti-fog coatings using inorganic fine particles such as colloidal silica, the primary particle size is maintained by the electronic repulsion of the particles. However, depending on the dispersion medium used, particle aggregation can easily occur, causing the appearance of the transparent film to deteriorate. In particular, when coating by spraying, there is a problem of particle aggregation occurring easily once the coating is applied to the substrate. This can result in the coating having a pronounced unevenness known as "citrus peel," or the formation of localized aggregates, which can cause poor appearance. Therefore, even if the desired anti-fog properties are achieved, such poor appearance can reduce the commercial value of the anti-fog product.

The present invention therefore aims to provide a coating agent that can form a coating film that has excellent anti-fogging properties and a good appearance.

The inventors conducted extensive research in light of the problems with the prior art and discovered that a composition containing specific ingredients can achieve the above objectives, leading to the completion of the present invention.

That is, the present invention relates to the following liquid anti-fogging coating agent.
1. A liquid coating agent,
(A) long-shaped colloidal silica,
(B) spherical colloidal silica,
(C) a silane derivative compound having a polyethylene glycol chain in the molecule;
A liquid anti-fog coating agent comprising (D) a silane derivative compound having an epoxy group in the molecule (excluding the silane derivative compound of (C) above), and (E) a solvent including (E1) water, (E2) a first organic solvent having a surface tension of 35 mN/m or more, and (E3) a second organic solvent having a surface tension of less than 35 mN/m.
2. The liquid anti-fog coating agent according to item 1, wherein the surface tension of the first organic solvent is 35 to 72 mN/m, and the surface tension of the second organic solvent is 20 to 30 mN/m.
3. The liquid anti-fog coating agent according to item 1, wherein the boiling point of the first organic solvent is 120° C. or higher, and the boiling point of the second organic solvent is 120° C. or higher.
4. The liquid anti-fog coating agent according to item 1, wherein the water accounts for 85 to 97 wt %, the first organic solvent accounts for 2 to 10 wt %, and the second organic solvent accounts for 1 to 5 wt %, based on a total of 100 wt % of the solvents.
5. The liquid anti-fogging coating agent according to item 1, wherein the content of the spherical colloidal silica is 20 to 50 parts by weight out of a total of 100 parts by weight of the elongated colloidal silica and the spherical colloidal silica.
6. As the solid content,
(A) Long-sized colloidal silica: 45 to 75% by weight,
(B) spherical colloidal silica: 20 to 45% by weight,
(C) a silane derivative compound having a polyethylene glycol chain in the molecule: 0.1 to 5% by weight,
(D) Silane derivative compound having an epoxy group in the molecule: 0.1 to 5% by weight
2. The liquid anti-fogging coating agent according to Item 1, comprising:
7. The liquid anti-fog coating agent according to item 1, further comprising a surfactant.
8. The liquid anti-fog coating agent according to item 1, which is applied by spraying.
9. A spray product comprising a spray device including a liquid storage section and a spray nozzle for spraying a liquid into the liquid storage section, wherein the liquid storage section is filled with the liquid anti-fogging coating agent according to any one of items 1 to 7.
10. An anti-fogging coating film comprising a coating film of the liquid anti-fogging coating agent according to any one of items 1 to 7.
11. An article comprising the anti-fogging coating film according to item 10 laminated on the surface of a substrate.

The present invention provides a coating agent that can form a coating film that exhibits excellent anti-fogging properties and a good appearance.

In particular, the liquid anti-fog coating agent of the present invention uses highly hydrophilic inorganic fine particles (spherical silica, elongated silica) as its main component, and an aqueous solvent containing two organic solvents with different surface tensions. This allows for the maintenance of appropriate gaps between the inorganic fine particles while suppressing aggregation that could affect appearance during film formation (when the coating liquid hardens or solidifies).

In other words, by suppressing such aggregation, it is possible to form a coating film with a good appearance. Furthermore, by maintaining appropriate gaps between the inorganic fine particles, the water absorption properties of those gaps are maintained, which effectively demonstrates the high hydrophilicity of the inorganic fine particles, resulting in excellent anti-fogging properties and, ultimately, high anti-fogging durability.

FIG. 1 is a diagram showing the results of observing the appearance of coating films of Examples and Comparative Examples (at 20x magnification).

1. Anti-Fog Coating Agent The liquid anti-fogging coating agent of the present invention (the coating agent of the present invention) is
(A) long-shaped colloidal silica (component A),
(B) spherical colloidal silica (component B),
(C) a silane derivative compound having a polyethylene glycol chain in the molecule (component C);
(D) a silane derivative compound having an epoxy group in the molecule (excluding the silane derivative compound (C) above) (component D), and (E) a solvent (component E) containing (E1) water, (E2) a first organic solvent having a surface tension of 35 mN/m or more, and (E3) a second organic solvent having a surface tension of less than 35 mN/m.
The present invention is characterized by comprising:

(1) Regarding Each Component (1-1) Component A The long colloidal silica of Component A is a colloidal solution in which long colloidal silica ( _SiO2 or its hydrate) in water is dispersed. The long colloidal silica is composed of primary silica particles covalently bonded to each other to form long strings. The diameter of the primary silica particles (average primary particle size) is not particularly limited, but is typically about 5 to 300 nm. In the present invention, the long colloidal silica can spread and adsorb onto the surface of the substrate to form a coating, and therefore can be suitably used as the active ingredient of the coating agent of the present invention.

Examples of long-sized colloidal silica include chain-shaped colloidal silica and pearl necklace-shaped colloidal silica. The aspect ratio of the long-sized colloidal silica may be, for example, 4 or more, but is not limited to this.

Colloidal silica using water as a dispersion medium can be acidic, neutral, or basic. While any of these can be used in the present invention, particular examples include acidic elongated colloidal silica, which exhibits a strong acidity of pH 1 to 3 when dispersed in water; neutral elongated colloidal silica, which exhibits a weak acidity, neutrality, or weak basicity of pH 4 to 9; and basic elongated colloidal silica, which exhibits a pH of 10 to 14. These can be used alone or in combination.

In this case, when using a mixture of multiple colloidal silicas, it is preferable to use them in combination so that the coating agent of the present invention does not affect the substrate to which it is applied (usually in the weakly acidic to weakly basic range, particularly in the pH range of about 7 to 10). For example, a combination of acidic long-sized colloidal silica and basic long-sized colloidal silica, a combination of basic long-sized colloidal silica and acidic long-sized colloidal silica, or neutral long-sized colloidal silica can be used alone.

This type of elongated colloidal silica itself can be publicly known or commercially available. Examples of commercially available products include those with the product names "ST-OUP," "ST-UP," "ST-PS-S," "ST-PS-M," "ST-PS-SO," and "ST-PS-MO" (all manufactured by Nissan Chemical Industries, Ltd.).

The solids content of Component A in the coating agent of the present invention is not limited and can be set appropriately depending on, for example, the desired performance, application, and area of application. However, it is usually around 45 to 75% by weight, and preferably 50 to 70% by weight. This more reliably achieves both excellent anti-fogging properties and a good appearance.

(1-2) Component B The spherical colloidal silica, which is component B, is a colloidal solution in which spherical silica ( _SiO2 or its hydrate) is dispersed in water.

The spherical colloidal silica has a roughly spherical particle shape in water. Therefore, the aspect ratio of the spherical colloidal silica may be, for example, approximately 1.5 or less, but is not limited to this. The diameter (average particle size) of the primary particles of the silica is not limited, but is typically approximately 5 to 300 nm. In the present invention, two or more types of spherical colloidal silica with different average particle sizes can also be used. This allows for the formation of a denser coating film, which prevents the elution of coating components and effectively suppresses or prevents the occurrence of "water drip marks" as shown in Test Example 1 below.

Generally, spherical colloidal silica is acidic, neutral, or basic, but the present invention uses basic spherical colloidal silica that contains ammonium ions as described above and exhibits a pH of 10 to 14. These can be used alone or in combination.

Such spherical colloidal silica can be any known or commercially available product. Examples of commercially available basic spherical colloidal silica include products with the names "ST-N," "ST-NS," and "ST-N-40" (all manufactured by Nissan Chemical Industries, Ltd.). Examples of acidic spherical colloidal silica include products with the names "ST-O," "ST-OS," and "ST-O-40" (all manufactured by Nissan Chemical Industries, Ltd.).

The solids content of Component B in the coating agent of the present invention is not limited and can be set appropriately depending on, for example, the desired performance, application, and site of application, but is typically around 20 to 45% by weight, with 25 to 40% by weight being particularly preferred. Setting it within this range ensures that excellent anti-fogging properties and a good appearance can be achieved.

The ratio of component A to component B is not limited, but it is preferable that the ratio of component B be 20 to 50 parts by weight, with the total of both being 100 parts by weight, and it is even more preferable that it be 25 to 40 parts by weight. This allows for better film-forming properties, anti-fogging durability (water stain resistance), and a better appearance.

(1-3) Component C A silane derivative compound having a polyethylene glycol chain in the molecule is used as component C. Specifically, at least one of the compounds represented by the following general formulas (1-1) to (1-3) can be used.

As the compound represented by general formula (1-1),
(wherein R ¹ , R ² and R ³ are the same or different and each represent an alkyl group having 1 to 3 carbon atoms; R ⁴ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms; n is an integer of 1 to 5; and m is an integer of 1 to 20, preferably 4 to 20, and more preferably 4 to 15.)

The silane derivative compound represented by general formula (1-1) has alkoxy groups (i.e., groups of -OR ¹ , -OR ² and -OR ³ ) that can react with long sized silica and spherical silica, and a hydrophilic group (-OCH ₂ CH ₂ -) containing a polyethylene glycol chain that has high affinity for water. Because the silane derivative compound represented by general formula (1-1) has a substituent that can react with long sized silica and a hydrophilic group, the silane derivative compound bonds to the long sized silica and spherical silica, and can impart hydrophilicity to the coating film formed by the coating agent of the present invention.

Specific examples of silane derivative compounds represented by general formula (1-1) include polyethylene glycol-modified alkoxysilanes such as methoxy PEG-10 propyl trimethoxysilane and ethoxy PEG-10 propyl trimethoxysilane. Other examples that can be used include 2-[hydroxy(polyethyleneoxy)ethyl]trimethoxysilane, 3-[hydroxy(polyethyleneoxy)propyl]trimethoxysilane, 4-[hydroxy(polyethyleneoxy)butyl]trimethoxysilane, 2-[alkoxy(polyethyleneoxy)ethyl]trimethoxysilane, 3-[alkoxy(polyethyleneoxy)propyl]trimethoxysilane, and 4-[alkoxy(polyethyleneoxy)butyl]trimethoxysilane.

The silane derivative compound represented by general formula (1-1) itself can be a commercially available product. Examples of commercially available products include "Dynasylan 4148" and "Dynasylan 4150" (both from Evonik Japan Co., Ltd.) and "Methoxy PEG-10 Propyltrimethoxysilane" (PG series) (Azmax Co., Ltd.).

Further, as the compound represented by the general formula (1-2),
(wherein R ¹¹ , R ¹² , R ¹³ and R ¹⁴ are the same or different and are alkyl groups having 1 to 3 carbon atoms; A is selected from the group consisting of -O-, -NHCOO-, -OCO-, -COO-, -OCH ₂ CH(OH)CH ₂ O-, -OCH ₂ CH ₂ CH(OH)O-, -S-, -SCO- and -COS-; n1 is an integer of 1 to 5; and m1 is an integer of 1 to 20, preferably 4 to 20, and more preferably 4 to 15.) Among the silane derivative compounds represented by general formula (1-2), the most preferred group for A in the formula is -O-.

The silane derivative compound represented by the general formula (1-2) has an alkoxy group (i.e., groups of —OR ¹¹ , —OR ¹² and —OR ¹³ ) capable of reacting with long-sized silica, and a hydrophilic group (—CH ₂ CH ₂ O—) containing a polyethylene glycol chain that has a high affinity for water.

The silane derivative compound represented by general formula (1-2) has a substituent that can react with long-shaped silica and a hydrophilic group, which allows the silane derivative compound to bond to the long-shaped silica and impart hydrophilic properties to the coating film formed by the coating agent of the present invention.

Specific examples of silane derivative compounds represented by general formula (1-2) include 3-[acetoxy(polyethyleneoxy)propyl]triethoxysilane, 2-[acetoxy(polyethyleneoxy)ethyl]trimethoxysilane, 3-[acetoxy(polyethyleneoxy)propyl]trimethoxysilane, and 4-[acetoxy(polyethyleneoxy)butyl]trimethoxysilane.

The silane derivative compound represented by general formula (1-2) itself can be a known or commercially available product. Commercially available products include 3-[acetoxy(polyethyleneoxy)propyl]triethoxysilane (Gelest Inc.), a silane derivative compound having a polyethylene glycol chain and an acyl group in the molecule.

As the compound represented by the general formula (1-3),
(wherein R ²¹ , R ²² and R ²³ are the same or different and are an alkyl group having 1 to 3 carbon atoms; R ²⁴ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms; B is selected from the group consisting of -NHCOO-, -OCO-, -COO-, -OCH ₂ CH(OH)CH ₂ O-, -OCH ₂ CH ₂ CH(OH)O-, -S-, -SCO- and -COS-; n2 is an integer of 1 to 5; and m2 is an integer of 1 to 20, preferably 4 to 20, and more preferably 4 to 15.) A compound represented by the following formula can be used. Of the silane derivative compounds represented by general formula (1-3), the most preferred group for B in the formula is -NHCOO- (a urethane group).

The silane derivative compound represented by the general formula (1-3) has alkoxy groups (i.e., groups of -OR ²¹ , -OR ²² and -OR ²³ ) that can react with long-sized silica, and a hydrophilic group (-CH ₂ CH ₂ O-) that contains a polyethylene glycol chain that has high affinity for water.

The silane derivative compound represented by general formula (1-3) has a substituent capable of reacting with long-shaped silica and a hydrophilic group, which allows the silane derivative compound to bond to the long-shaped silica and impart hydrophilic properties to the coating film formed by the coating agent of the present invention.

Specific examples of silane derivative compounds represented by general formula (1-3) include 2-hydroxy(polyethyleneoxy)ethyl [3-(trimethoxysilyl)propyl]carbamate, 2-hydroxy(polyethyleneoxy)ethyl [3-(triethoxysilyl)propyl]carbamate, 2-alkoxy(polyethyleneoxy)ethyl [3-(trimethoxysilyl)propyl]carbamate, 2-alkoxy(polyethyleneoxy)ethyl [3-(triethoxysilyl)propyl]carbamate, and 2-alkoxy(polyethyleneoxy)ethyl [4-(trimethoxysilyl)butanoate] ester.

Furthermore, among the silane derivative compounds represented by general formula (1-3), silane derivative compounds having a polyethylene glycol chain and a urethane group in the molecule are most preferred. Silane derivative compounds having a polyethylene glycol chain and a urethane group in the molecule can be synthesized by reacting an alkoxysilane compound having an isocyanato group, such as isocyanatopropyltrimethoxysilane or isocyanatopropyltriethoxysilane, with polyethylene glycol.

In this specification, among the silane derivative compounds represented by general formula (1-3), silane derivative compounds having a polyethylene glycol chain and a urethane group in the molecule, which are particularly suitable for use in embodiments, may be referred to as "urethane silanes." Furthermore, the silane derivative compounds represented by general formulas (1-1), (1-2), and (1-3) may be collectively referred to as "silane derivative compounds having a polyethylene glycol chain in the molecule."

The solids content of Component C in the coating agent of the present invention is not limited and can be set appropriately depending on, for example, the desired performance, application, and site of application, but is typically approximately 0.1 to 5% by weight, with 1 to 4% by weight being particularly preferred. Setting it within this range ensures that excellent anti-fogging properties and a good appearance can be achieved.

(1-4) Component D A silane derivative compound having an epoxy group in the molecule (excluding the silane derivative compound (C) above) is used as component D. As component D, a silane derivative compound represented by general formula (2) can be used.
(In the formula, R ⁵ , R ⁶ and R ⁷ are the same or different and each represents an alkyl group having 1 to 3 carbon atoms, p is an integer of 1 to 5, and X is an organic group containing an epoxy group.)

This has alkoxy groups (i.e., groups of —OR ⁵ , —OR ⁶ and —OR ⁷ ) that can react with the long-shaped silica, and X (X is an organic group containing an epoxy group). Examples of the organic group containing an epoxy group include, but are not limited to, a glycidyl group.

The silane derivative compound represented by general formula (2) has a substituent that can react with the long-shaped silica, which enables the silane derivative compound to crosslink between the long-shaped silica particles.

Specific examples of silane derivative compounds represented by general formula (2) include epoxy group-containing silane derivative compounds such as 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, and 3-glycidoxypropylmethyldiethoxysilane.

Silane derivative compounds containing an epoxy group within the molecule can also be commercially available products such as "Dynasylan GLYEO" (Evonik Japan Co., Ltd.), "KBM402," "KBM403," "KBE402," and "KBE403" (all manufactured by Shin-Etsu Chemical Co., Ltd.). These silane derivative compounds react with and bond to long-shaped silica particles, cross-linking the silica particles and increasing the strength of the coating film while also imparting hydrophilic properties to the coating film.

The solids content of component D in the coating agent of the present invention is not limited and can be set appropriately depending on, for example, the desired performance, application, and site of application, but is typically approximately 0.1 to 5% by weight, with 1 to 4% by weight being particularly preferred. Setting it within this range more reliably ensures excellent anti-fogging properties, a good appearance, and other properties.

(1-6) Component E Component E is a solvent (aqueous solvent) containing (E1) water, (E2) a first organic solvent having a surface tension of 35 mN/m or more, and (E3) a second organic solvent having a surface tension of less than 35 mN/m. The use of such a specific aqueous solvent makes it possible to form a coating film with excellent appearance (particularly a coating film with excellent coating film leveling and in which the formation of orange peel, aggregates, etc. is effectively suppressed), especially when the coating agent of the present invention is applied by spraying.

While the mechanism by which the present invention produces a coating film with both high anti-fogging properties and excellent appearance is unclear, when the first organic solvent is used alone, the inorganic fine particles dry (cure) while maintaining their primary particle size, forming a dense coating film with no gaps, which results in the desired water absorption and in unsatisfactory anti-fogging properties. On the other hand, when the second organic solvent is used alone, the inorganic fine particles dry (cure) while forming secondary particle sizes, resulting in the formation of a coating film with many aggregated particles, which causes the coating film to have poor appearance. Based on these findings, it is surmised that the combined use of the first and second organic solvents maintains appropriate gaps while suppressing aggregation that would otherwise cause poor appearance, resulting in the formation of a coating film with both excellent anti-fogging properties and good appearance. Thus, in the present invention, the combined use of the first and second organic solvents achieves effects that cannot be achieved with either the first or second organic solvent alone, and therefore a synergistic effect of the two organic solvents is achieved.

Various types of water can be used, such as pure water, ultrapure water, and tap water. The amount of water contained in 100% by weight of component E is not limited, but is usually about 85 to 97% by weight, and preferably 90 to 96% by weight. If there is too little water, the dispersion stability of the inorganic fine particles may decrease. Furthermore, if there is too much water, the surface tension of the coating liquid may decrease, potentially reducing the coating film leveling ability.

The first organic solvent typically has a surface tension of 35 mN/m or more, preferably 35 to 72 mN/m, and more preferably 50 to 72 mN/m. A first organic solvent with such a surface tension has the function of suppressing particle aggregation in the coating agent of the present invention.

Specific examples of the first organic solvent include at least one of dipropylene glycol, propylene glycol, 1,2 butanediol, 1,3 butanediol, and 1,4 butanediol.

The content of the first organic solvent per 100% by weight of component E is not limited, but is typically about 2 to 10% by weight, and preferably 3 to 9% by weight. If the amount of the first organic solvent is too small, particle aggregation may occur more easily, which may result in a deterioration in the appearance of the coating film. Furthermore, if the amount of the first organic solvent is too large, the coating film may become too dense, making it difficult to achieve the desired anti-fogging effect.

The second organic solvent typically has a surface tension of less than 35 mN/m, and preferably 20 to 30 mN/m. A second organic solvent with such a surface tension has the function of increasing the porosity of the coating film in the coating agent of the present invention.

Specific examples of the second organic solvent include at least one of diethylene glycol monobutyl ether, 1-methoxy-2-propanol, isopropyl alcohol, diethylene glycol monoethyl ether, and diethylene glycol monomethyl ether.

The content of the second organic solvent per 100% by weight of component E is not limited, but is typically around 1 to 5% by weight, and preferably 1 to 3% by weight. If the amount of the second organic solvent is too small, the porosity of the coating film may become too low, resulting in a risk of not achieving the anti-fogging effect due to water absorption. Furthermore, if the amount of the second organic solvent is too large, particle aggregation may occur more easily, which may result in a deterioration in the appearance of the coating film.

In the coating agent of the present invention, the ratio (weight ratio) of the first organic solvent to the second organic solvent can be set, for example, in the range of about first organic solvent:second organic solvent = (1.5-3.5):1, but is not limited to this.

In addition, in the present invention, it is preferable that both the first organic solvent and the second organic solvent are high-boiling point solvents. More specifically, it is preferable that both have boiling points of 120°C or higher (particularly 150 to 250°C). By using such high-boiling point solvents, an appropriate evaporation time is ensured, resulting in the formation of a coating film with a good appearance.

The above surface tensions of the first and second organic solvents can be measured using the Wilhelmy plate method at a measurement temperature of 25°C.

In the present invention, the solvent, which is component E, is preferably a solution (mixed solution) in which the first organic solvent and the second organic solvent are dissolved in water, but it is not necessary for all of them to be completely dissolved as long as the effects of the present invention are not impaired.

The content of component E in the coating agent of the present invention can be set appropriately depending on, for example, the coatability and film-forming properties of the coating agent of the present invention. For example, it can be set so that the solids concentration of the coating agent of the present invention is approximately 5 to 90% by weight, and preferably within the range of 5 to 50%, but is not limited to this.

(1-7) Other Components The coating agent of the present invention can be appropriately blended with additives typically contained in paint compositions (surfactants, dyes, pigments, plasticizers, dispersants, preservatives, matting agents, antistatic agents, flame retardants, etc.) within a range that does not impair the effects of the present invention. The surfactant may be any of anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants. The addition of a surfactant allows the coating agent of the present invention to be applied more smoothly to the substrate. When a surfactant is used, the amount can be set to, for example, about 0.01 to 0.3 wt % in the coating agent of the present invention, but is not limited to this.

(2) Properties of the Coating Agent of the Present Invention The coating agent of the present invention can usually be used in liquid form. In this case, as described above, component E is used as a solvent. The viscosity and other properties of the coating agent of the present invention can be appropriately set depending on the application, type of substrate, etc.

In particular, when applying the coating agent of the present invention by spraying, it is preferable to set the viscosity (25°C) to approximately 1 to 100 mPa·s, but this can be set appropriately depending on the specifications of the spray equipment, etc.

2. Production of the Coating Agent of the Present Invention The coating agent of the present invention can be produced by uniformly mixing the above-mentioned components. The order of mixing is not particularly limited, and the components may be mixed simultaneously or sequentially.

Mixing can also be carried out using known or commercially available equipment such as a mixer or kneader.

3. Use of the Coating Agent of the Present Invention The coating agent of the present invention can be applied to the surface of a substrate in the same manner as known or commercially available anti-fog coating agents, to form a coating film (anti-fog coating film) made from the coating agent of the present invention as a cured film on the surface of the substrate. The present invention also includes such anti-fog coating films made from the coating agent of the present invention.

The material of the substrate is not particularly limited and may be, for example, plastic, glass, metal, ceramic, rubber, etc. Furthermore, the substrate may be a material constituting any of raw materials, primary products, and final products. Examples of such final products include lighting devices, headlights (covers, lenses, etc.), windows, lenses, lens covers, monitors, monitor covers, eyeglasses/sunglasses, goggles, face shields, face guards, helmets, etc. Thus, articles in which an anti-fog coating film made from the coating agent of the present invention is laminated on the surface of a substrate constituting the article are also encompassed by the present invention.

Articles of the present invention that include an anti-fog coating film have excellent anti-fog properties due to the coating film. Moreover, even when the article is exposed to unexpectedly high temperature conditions, the formation of drip marks and other problems can be effectively suppressed, maintaining a good appearance. Furthermore, coating films made with the coating agent of the present invention adhere strongly to substrates such as plastics and have high adhesion, making them highly durable at high temperatures and able to provide long-term anti-fog properties. Furthermore, the coating film can also suppress the formation of orange peel and aggregates that are prone to occur with conventional coating agents, thereby achieving a good appearance as well.

The method for applying the coating agent of the present invention to a substrate is not limited, and various coating methods can be used, such as the doctor blade method, bar coating method, dipping method, spray method (air spray method), roller brush method, and roller coater method.

The coating agent of the present invention is particularly suitable for application by spraying. While conventional coating agents tend to result in poor coating film appearance, the coating agent of the present invention, when applied by spraying, can more reliably form a coating film that suppresses orange peel and the formation of aggregates. Therefore, the present invention also encompasses a spray product in which a liquid container is filled with the coating agent of the present invention in a spray device that includes a liquid container and a spray nozzle that sprays liquid into the liquid container.

The spray device itself is not limited, and any known or commercially available device can be used. The spray device may be either manual or electric. Therefore, for example, a commercially available spray device can be used (sprayed) under normal conditions by filling the liquid reservoir with the coating agent of the present invention.

The coating thickness is not particularly limited, but it should be adjusted so that the thickness of the final anti-fogging coating film is within the range of approximately 0.1 to 10 μm, but is not limited to this.

After application, the wet coating can be dried to form an anti-fogging coating. Air drying is acceptable, but heat drying is preferred. The heat drying temperature should be high enough to allow the silica and silane derivative to react and the solvent to evaporate. The heating temperature is, for example, approximately 80 to 150°C, and particularly 100 to 140°C. This allows the reaction to proceed smoothly and the solvent to evaporate.

The heating method is not particularly limited and can be, for example, heating with a heating device such as a burner or oven, or heating with hot air from a dryer or the like. When the coating film made from the coating agent of the present invention dries in this way, the elongated colloidal silica (and optionally spherical colloidal silica) spread on the substrate surface becomes elongated silica (and optionally spherical silica) and forms the desired cured film. Meanwhile, the silane derivative compound bonds with these silica particles, cross-linking them and forming a strong, high-order structure.

In this way, by applying the coating agent of the present invention to an article, an anti-fogging coating film can be formed, resulting in an article coated with such a coating film. At the same time, the specific solvent (component E) of the present invention aligns the inorganic fine particles (silica particles) while maintaining appropriate gaps during evaporation, allowing for the formation of a coating film with a relatively smooth, uniform surface, which also gives the coating a good appearance.

The article of the present invention has excellent anti-fogging properties due to its coating film. Moreover, as described above, by forming a coating film using two types of colloidal silica in combination in the presence of a specific solvent, it is possible to effectively suppress phenomena that cause noticeable changes in appearance, such as the formation of aggregates, orange peel, and water drip marks, even when the article is exposed to unexpectedly high temperature conditions. Furthermore, the coating film produced by the coating agent of the present invention firmly adheres to substrates such as plastics and has high adhesion, making it highly durable at high temperatures and able to maintain anti-fogging properties for long periods of time.

The following examples and comparative examples will explain the features of the present invention in more detail. However, the scope of the present invention is not limited to these examples.

Examples 1 to 4
A liquid coating agent was prepared by uniformly mixing the components shown in Table 1. The content of each component is expressed in "% by weight."

Comparative Examples 1 to 4
A liquid coating agent was prepared in the same manner as in Example 1, except that the composition was changed as shown in Table 1.

The meanings of the abbreviations in Table 1 are as follows:
"ST-OUP": Snowtex OUP, Nissan Chemical Industries, Ltd., acidic elongated colloidal silica (solid content 15% by weight, aqueous dispersion)
"ST-UP": Snowtex UP, Nissan Chemical Industries, Ltd., Na ⁺ -containing basic elongated colloidal silica (solid content 20% by weight, aqueous dispersion)
"ST-N": Snowtex N, Nissan Chemical Industries, Ltd., NH ₄ ⁺ -containing spherical basic colloidal silica with a particle size of 12 nm (solid content 20% by weight, aqueous dispersion)
"ST-NXS": Snowtex NXS, Nissan Chemical Industries, Ltd., NH ₄ ⁺ -containing basic spherical colloidal silica with a particle size of 5 nm (solid content 15% by weight, aqueous dispersion)
"FT-150": Futergent 150, Neos Co., Ltd., anionic surfactant (solid content 100% by weight)
"D-4148": Dynasylan 4148, Evonik Japan Co., Ltd., silane derivative compound having a polyethylene glycol chain in the molecule (solid content 100% by weight)
"KBM-403": Shin-Etsu Chemical Co., Ltd., silane derivative compound having an epoxy group in the molecule (solid content 100% by weight)
"DPG": Dipropylene glycol (boiling point 230°C, surface tension 71.4 mN/m)
・ "1,3-BD": 1,3 butanediol (boiling point 208°C, surface tension 37.8 mN/m)
"BDG": Diethylene glycol monobutyl ether (boiling point 231°C, surface tension 29.1 mN/m)
"PGM": 1-methoxy-2-propanol (boiling point 120°C, surface tension 27.7mN/m)

Test Example 1
A coating film was formed on a substrate using the coating agent prepared in each of the Examples and Comparative Examples to prepare a sample.
A coating agent was applied to a 1 mm thick polycarbonate substrate. The application was performed by spray coating, and the amount of coating was adjusted so that the thickness of the coating film (cured film) after the coating agent cured would be 1 μm. The substrate coated with the coating agent was placed in an oven at 110° C. and heated for 15 minutes to form a cured film, thereby obtaining a sample. Using the obtained sample, various performance evaluations were performed using the methods shown below.

(1) Zeta potential The zeta potential of the coating agent was measured using an Otsuka Electronics "ELSZ-1000." Zeta potential is the potential difference between the slip surface in the electric double layer and a portion sufficiently distant from the interface. Because it can evaluate the electrostatic repulsion characteristics (≒ cohesion) between particles, it is an important parameter in controlling the particle cohesion state in the coating film.

(2) Porosity The surface of the cured film was observed using a field emission scanning electron microscope (FE-SEM), and the obtained image was used to calculate the percentage of voids on the coating surface. More specifically, the grayscale image was binarized, the brightness range of the voids was set, and the area ratio of the voids to the entire image was then read and calculated using software.

(3) Appearance of coating film The appearance of the cured film was observed visually and using a microscope to check the leveling state and film smoothness. As a result, if no particular abnormalities were observed, it was marked as "○", and if a granular appearance due to leveling or particle agglomerations was observed, it was marked as "×".
For reference, the observation results of Example 1 and Comparative Example 3 (20x magnification) are shown in Figure 1. Figure 1A shows the observation results of Example 1. Figure 1B shows the observation results of Comparative Example 2. In Figure 1A, the surface does not have a granular appearance, and the surface has a good appearance. The granular objects in Figure 1A are thought to be secondary agglomerates of particles (colloidal silica component, etc.), but these are minute agglomerates that do not impair the appearance of the coating film, do not affect the effects of the present invention, and are not a problem in practical use. In Figure 1B, the surface has a granular (island-like) appearance, and agglomeration is noticeable.

(4) Haze: Measured using a haze meter in accordance with Japanese Industrial Standard JIS K 7136. A haze value of less than 0.7 was marked as "Good", and a haze value of 0.7 or more was marked as "Poor".

(5) Anti-fogging properties A sample was placed with the coating film facing downward at a height of 1 cm above the water surface of a 40°C hot water bath, and the coating film was exposed to steam from the hot water bath for 10 seconds. During this time, it was visually confirmed whether or not a haze had formed on the coating film. When no haze was observed on the coating film, it was marked as "◯", and when haze was observed, it was marked as "X".

(6) Water Dripping Property The sample that had been subjected to the anti-fogging property evaluation in (2) above was left standing vertically for 30 minutes to dry, and the presence or absence of water drip marks on the sample surface was visually confirmed. When no water drip marks were observed, the sample was marked with "○", and when water drip marks were observed, the sample was marked with "×".

(7) Anti-fogging property after durability test After the sample was left to stand in an environment of a temperature of 50° C. and a humidity of 95% for 240 hours, the anti-fogging property was evaluated as described in (5) above.

As is clear from the results in Table 1, Examples 1 to 4 contained the solvent of the present invention, had a zeta potential within the range of -27 to -33 mV, and exhibited good appearance and anti-fogging durability.

Comparative Example 1 did not contain a high-boiling point solvent, and could not be applied uniformly to the polycarbonate substrate.

Comparative Example 2 did not contain a high-boiling-point solvent with a surface tension of less than 35 mN/m, resulting in a low porosity and insufficient anti-fogging durability.

In Comparative Example 3, a sufficient amount of high-boiling solvent with a surface tension of 35 mN/m or more was blended, but the amount of high-boiling solvent with a surface tension of less than 35 mN/m was too high, resulting in a granular surface (poor appearance).

In Comparative Example 4, the surface was granular (poor appearance) because a high-boiling-point solvent with a surface tension of 35 mN/m or more was not blended.

The coating agent of the present invention can be applied to the surface of a substrate to effectively form an anti-fogging coating film. This makes it possible to provide a variety of articles with anti-fogging properties (such as lighting devices, headlights, windows, lenses, lens covers, monitors, monitor covers, eyeglasses/sunglasses, goggles, face shields, face guards, helmets, etc.).

Claims (12)

A liquid coating agent,
(A) long-shaped colloidal silica,
(B) spherical colloidal silica,
(C) a silane derivative compound having a polyethylene glycol chain in the molecule;
(D) a silane derivative compound having an epoxy group in the molecule (excluding the silane derivative compound (C) above), and (E) a solvent including (E1) water, (E2) a first organic solvent having a surface tension of 35 mN/m or more, and (E3) a second organic solvent having a surface tension of less than 35 mN/m,
In a total of 100% by weight of the solvents, water accounts for 85 to 97% by weight, the first organic solvent accounts for 2 to 10% by weight, and the second organic solvent accounts for 1 to 5% by weight, and the ratio (weight ratio) of the first organic solvent to the second organic solvent is first organic solvent:second organic solvent=(1.5 to 3.5):1;
A liquid anti-fogging coating agent characterized by: The liquid anti-fog coating agent according to claim 1, wherein the surface tension of the first organic solvent is 35 to 72 mN/m and the surface tension of the second organic solvent is 20 to 30 mN/m. The liquid anti-fog coating agent according to claim 1, wherein the boiling point of the first organic solvent is 120°C or higher, and the boiling point of the second organic solvent is 120°C or higher. 2. The liquid anti-fog coating agent according to claim 1, wherein the second organic solvent accounts for 1 to 3 wt % of the total amount of the solvents, 100 wt %. the first organic solvent is at least one of dipropylene glycol, propylene glycol, 1,2 butanediol, 1,3 butanediol, and 1,4 butanediol;
2. The liquid anti-fog coating agent according to claim 1, wherein the second organic solvent is at least one of diethylene glycol monobutyl ether, 1-methoxy-2-propanol, isopropyl alcohol, diethylene glycol monoethyl ether, and diethylene glycol monomethyl ether. The liquid anti-fog coating agent according to claim 1, wherein the content of spherical colloidal silica is 20 to 50 parts by weight out of a total of 100 parts by weight of elongated colloidal silica and spherical colloidal silica. As solid content,
(A) Long-sized colloidal silica: 45 to 75% by weight,
(B) spherical colloidal silica: 20 to 45% by weight,
(C) a silane derivative compound having a polyethylene glycol chain in the molecule: 0.1 to 5% by weight,
(D) Silane derivative compound having an epoxy group in the molecule: 0.1 to 5% by weight
The liquid anti-fog coating agent of claim 1 , comprising: The liquid anti-fog coating agent according to claim 1, further comprising a surfactant. The liquid anti-fog coating agent according to claim 1, which is applied by spraying. A spray product comprising a spray device including a liquid storage section and a spray nozzle for spraying a liquid into the liquid storage section, wherein the liquid storage section is filled with the liquid anti-fogging coating agent according to any one of claims 1 to 8 . An anti-fogging coating film comprising a coating film of the liquid anti-fogging coating agent according to any one of claims 1 to 8 . An article comprising the anti-fog coating film according to claim 11 laminated on the surface of a substrate.