JP6943664B2 - Anti-fog coating composition and anti-fog coating film and anti-fog article - Google Patents

Description

The present invention relates to an anti-fog coating composition, an anti-fog coating film prepared by using the same, and an anti-fog article.

Lighting devices such as automobile headlights are mainly composed of a light source and a transparent member made of glass or plastic arranged in front of the light source. Then, the light emitted from the light source is irradiated to the outside and the peripheral portion of the lighting device through the transparent member. In such a lighting device, cloudiness may occur inside the transparent member (light source side), and the intensity of the irradiation light may decrease, causing a safety problem. In addition, the amount of light emitted through the cloudy transparent member is small, which can be a problem in terms of aesthetics.

Patent Document 1 discloses an anti-fog composition composed of a copolymer (A), a polyfunctional blocked isocyanate compound (B), and a surfactant (C). The anti-fog composition of Patent Document 1 utilizes a conventionally well-known anti-fog mechanism, and is a surfactant (C) present in an anti-fog coating film to which the anti-fog composition is applied. However, the surface tension of water adhering to the anti-fog coating film on the base material is reduced to instantly form a smooth water film to prevent diffused reflection of light, thereby preventing anti-fog. On the other hand, Patent Document 2 discloses an anti-fog agent containing an aqueous medium, necklace-shaped colloidal silica, a silane derivative, and a surfactant. Patent Document 2 uses necklace-shaped colloidal silica having a pH of 8 to 11 (that is, alkaline) when dispersed in an aqueous medium. The anti-fog agent of Patent Document 2 exhibits an anti-fog effect by coating the surface of the base material on which the coating film is formed with colloidal silica.

Japanese Unexamined Patent Publication No. 2016-169287 Japanese Unexamined Patent Publication No. 2005-126647

When a water film is formed on an anti-fog coating film made of an anti-fog composition containing a surfactant as a main component disclosed in Patent Document 1, the surfactant dissolves in water and locally The surfactant and water sometimes flowed together. When such a portion dries, water dripping marks may remain on the anti-fog article. Further, when colloidal silica exhibiting strong alkalinity in an aqueous medium is used as an anti-fog agent as in Patent Document 2, for unknown reasons, the colloidal silica coating the base material flows together with water. Water dripping marks may remain on the anti-fog article.
Therefore, an object of the present invention is to provide an anti-fog coating composition that exhibits an anti-fog effect for a long period of time without causing a change in appearance such as water dripping marks.

The antifogging coating composition according to the embodiment of the present invention is characterized by containing a colloidal silica mixture containing acidic elongated colloidal silica and elongated colloidal silica for pH adjustment.
Another embodiment of the present invention is an anti-fog coating containing an elongated colloidal silica mixture.
Yet another embodiment of the present invention is an anti-fog article comprising a substrate and an anti-fog coating.

The anti-fog coating film formed by using the anti-fog coating composition of the present invention instantly forms a smooth water film to prevent diffused reflection of light and has excellent anti-fog performance. The anti-fog coating film of the present invention is less likely to cause changes in appearance such as water dripping marks after drying. The anti-fog article (for example, a lighting device) using the anti-fog coating composition of the present invention is less likely to cause a change in appearance and can maintain a stable amount of light for a long period of time.

Embodiments of the present invention will be described below. One embodiment of the present invention is an antifogging coating composition containing a colloidal silica mixture containing acidic elongated colloidal silica and elongated colloidal silica for pH adjustment.

In the present embodiment, the anti-fog coating composition is a composition capable of forming a coating film on a base material such as glass or plastic to prevent fogging due to water droplets caused by water vapor. .. When there is a temperature difference between the two spaces separated by the base material, the humidity on the high temperature side condenses on the surface of the base material to form water droplets. These water droplets cause diffuse reflection of light, causing cloudiness. It is known that as a mechanism for preventing the formation of water droplets on the base material, there is a mechanism for instantly forming a water film of water adhering to the surface of the base material and a mechanism for instantly absorbing the water adhering to the surface of the base material. There is. The anti-fog coating composition of the present embodiment instantly forms a water film of water adhering to the surface of the base material to prevent the formation of water droplets to form an anti-fog coating film that prevents the base material from fogging.

The anti-fog coating composition of the present embodiment contains acidic elongated colloidal silica. Colloidal silica is a colloidal solution of silicon dioxide (silica, SiO ₂ ) or its hydrate. Depending on the nature of the dispersion medium, there are aqueous colloidal silica and organic solvent-based organosilica sol, and the silica particularly preferably used in the embodiment is colloidal silica. The primary particle size of the spherical silica that forms colloidal silica is usually about 10 to 300 nm, and this may aggregate to form larger secondary particles. The colloidal silica preferably used in this embodiment is a long colloidal silica. The long colloidal silica is a colloidal solution of the long silica in which the primary particles of silica are covalently bonded to form a long string. As such long colloidal silica, chain colloidal silica and pearl necklace-shaped colloidal silica are known. Since the elongated colloidal silica can spread and adsorb on the surface of the base material to form a film, it can be preferably used as a component of the anti-fog coating composition. There are acidic, neutral, and alkaline colloidal silicas using water as a dispersion medium. The colloidal silica preferably used as one component of the present embodiment is an acidic long colloidal silica which is dispersed in water and exhibits strong acidity of pH 1 to 3.

The anti-fog coating composition of the embodiment further contains an elongated colloidal silica for pH adjustment. The colloidal silica for pH adjustment is used to increase the pH of the acidic elongated colloidal silica described above to adjust the pH from weakly acidic to weakly alkaline. As described above, acidic elongated colloidal silica is preferably used because it can form a coating film after the dispersion medium evaporates to form a water film effectively and exert an anti-fog effect. .. However, if the acidity is too strong, the properties of the anti-fog coating composition will not be stable and handling may become difficult. Further, the strongly acidic anti-fog coating composition may damage the base material to be applied (for example, a metal base material or a predetermined plastic base material), and may not be used depending on the base material to be applied. Therefore, a pH adjuster is mixed to appropriately adjust the pH of the entire colloidal silica. As the pH adjuster, various alkaline compounds such as an inorganic base and an organic base can be used, but it is preferable to use colloidal silica for pH adjustment, which is easy to adjust the pH. When pH adjusting colloidal silica is used as the pH adjusting agent, it is more preferable that the pH adjusting colloidal silica is also a colloidal solution of long silica.

The acidic long colloidal silica and the long colloidal silica for pH adjustment are mixed so that the pH of the colloidal silica mixture is neutral to weakly alkaline (pH about 7 to 10). In order to make the pH of the colloidal silica mixture weakly alkaline, it is necessary to mix the acidic long colloidal silica and the long colloidal silica for pH adjustment so that the solid content weight ratio is 1: 4 to 5: 1. good. The solid content weight ratio is the ratio of the weight of solid content substantially to each colloidal silica.

The anti-fog coating composition of the embodiment may further contain a surfactant. In the anti-fog coating composition of the embodiment, the surfactant is used to assist the spread of colloidal silica on the surface of the substrate and facilitate the coating operation. As the surfactant, any of anionic surfactants, cationic surfactants, nonionic surfactants and amphoteric surfactants can be used, and one or more of these can be used. can. Examples of anionic surfactants include fatty acid salts such as sodium oleate and potassium oleate, higher alcohol sulfate esters such as sodium lauryl sulfate and ammonium lauryl sulfate, and alkylbenzene sulfone such as sodium dodecylbenzene sulfonate and sodium alkylnaphthalene sulfonate. Polyoxyethylene sulfate salts such as acid salts and alkylnaphthalene sulfonates, sodium naphthalene sulfonate formalin condensates, dialkyl sulfosuccinates, dialkyl phosphate salts, sodium polyoxyethylene alkylphenyl ether sulfate, and sulfonic acids containing perfluoroalkyl groups. Anionic fluorosurfactants such as salt type, carboxylate type containing perfluoroalkyl group, sulfonate type containing perfluoroalkenyl group, and carboxylate type containing perfluoroalkenyl group can be mentioned. Be done. As cationic surfactants, for example, amine salts such as ethanolamines, laurylamine acetate, triethanolamine monoaterate, stearamide ethyldiethylamine acetate, lauryltrimethylammonium chloride, stearyltrimethylammonium chloride, dilauryldimethylammonium chloride. , Distearyldimethylammonium chloride, lauryldimethylbenzylammonium chloride, quaternary ammonium salts such as stearyldimethylbenzylammonium chloride, cationic fluorine-based surfactants such as quaternary ammonium salt type containing perfluoroalkyl group or perfluoroalkenyl group. Activators can be mentioned.

Examples of the nonionic surfactant include polyoxyethylene higher alcohol ethers such as polyoxyethylene lauryl alcohol, polyoxyethylene lauryl ether and polyoxyethylene oleyl ether, and polyoxyethylene such as polyoxyethylene octylphenol and polyoxyethylene nonylphenol. Polyoxyethylene acyl esters such as alkylaryl ethers and polyoxyethylene glycol monostearate, polyoxyethylene sorbitan fatty acids such as polypropylene glycol ethylene oxide adducts, polyoxyethylene sorbitan monolaurates, and polyoxyethylene sorbitan monostearates. Esters, alkyl phosphates, phosphoric acid esters such as polyoxyethylene alkyl ether phosphoric acid esters, sugar esters, cellulose ethers, silicones such as polyether-modified silicone oils, ethylene oxide adducts containing perfluoroalkyl groups Type, amine oxide type containing perfluoroalkyl group, oligomer type containing perfluoroalkyl group, ethylene oxide adduct type containing perfluoroalkenyl group, amine oxide type containing perfluoroalkenyl group, perfluoroalkenyl group Nonionic fluorosurfactants such as oligomer-type surfactants containing the above can be mentioned. As amphoteric surfactants, quaternary ammonium salts such as uryltrimethylammonium chloride, dilauryldimethylammonium chloride, distearyldimethylammonium chloride, lauryldimethylbenzylammonium chloride, fatty acid type amphoteric such as dimethylalkyllaurylbetaine and dimethylalkylstearylbetaine. Examples thereof include surfactants, amphoteric sulfonic acid-type surfactants such as dimethylalkylsulfobetaine, betaine-type amphoteric fluorine-based surfactants containing alkylglycine, perfluoroalkyl group or perfluoroalkenyl group, and the like. .. Any of the above-mentioned surfactants can be preferably used as the surfactant of the present embodiment. The surfactant is preferably contained in an amount of about 0.01 to 0.10 parts by weight with respect to 100 parts by weight of the anti-fog coating composition.

Further, the anti-fog coating composition of the embodiment may contain an organic solvent. The colloidal silica mixture using water as a dispersion medium, which is the main component of the anti-fog coating composition of the embodiment, can be applied alone on the surface of the substrate to form an anti-fog coating film. However, if an organic solvent is further contained in this, the drying of water at the time of forming the coating film is promoted, so that the anti-fog coating film can be formed faster. The organic solvent that can be used in the embodiment is an organic solvent that is compatible with water or miscible with water in a predetermined range. Examples of such organic solvents include alcohols (methanol, ethanol, propanol, ethylene glycol, etc.), ethers (dimethoxyethane, tetrahydrofuran, dioxane, propylene glycol monomethyl ether, etc.), ketones (acetone, ethylmethyl ketone, etc.). Examples thereof include amides (dimethylformamide and the like), dimethylsulfoxide (DMSO), acetonitrile, nitromethane, and triethylamine. The organic solvent is preferably contained in an amount of about 10 to 20 parts by weight with respect to 100 parts by weight of the anti-fog coating composition.

For the suitable anti-fog coating composition of the present embodiment, first, acidic elongated colloidal silica and elongated colloidal silica for pH adjustment are prepared, and then mixed with a surfactant and an organic solvent, if necessary. Can be manufactured. Since the acidic long colloidal silica and the long colloidal silica for pH adjustment are dispersed in water as a dispersion medium at a specific solid content ratio, the solid content weight ratio thereof is 1: 4 to 5: 1. It can be calculated and mixed so as to be. In addition to these components, the antifogging coating composition of the embodiment includes additives usually contained in the coating composition (for example, dyes, pigments, plasticizers, dispersants, preservatives, matting agents, antistatic agents, and difficulties. (Flame retardant) can be appropriately blended.

The anti-fog coating composition of the embodiment appropriately blended with acidic elongated colloidal silica, elongated colloidal silica for pH adjustment, and optionally a surfactant and an organic solvent can be applied to the surface of the substrate. Examples of the base material include glass, plastic, and metal, and the anti-fog coating composition of the embodiment can be preferably applied particularly on transparent plastic. The anti-fog coating composition can be appropriately applied to the surface of the substrate by a conventional coating method such as a doctor blade method, a bar coating method, a dipping method, an air spray method, a roller brush method, or a roller coater method. The applied anti-fog coating composition can be heated to form an anti-fog coating film. The anti-fog coating composition may be heated to a temperature sufficient for water and, if contained, an organic solvent to evaporate. Although it depends on the type of organic solvent used, water and the organic solvent can be evaporated by heating to about 80 to 150 ° C., preferably about 100 to 150 ° C. The coating material of the antifogging coating composition can be heated by a heating device such as a burner or an oven, or by a heating method using warm air such as a dryer.

The anti-fog coating composition of the embodiment is applied to a base material and dried by heating to form an anti-fog coating film, whereby an anti-fog article can be obtained. Examples of the anti-fog article using the anti-fog coating composition of the present embodiment include a lighting device, a headlight, a window, a lens, a lens cover, a monitor, a monitor cover and the like. The anti-fog article of the embodiment has excellent anti-fog performance and does not cause an appearance change such as formation of water dripping marks.

(1) Preparation of anti-fog coating composition Acidic long colloidal silica (ST-OUP [solid content 15%], Nissan Chemical Industry Co., Ltd.), long colloidal silica for pH adjustment (ST-UP [solid content]) 20%], Nissan Chemical Industry Co., Ltd., surfactants (Futergent 100, fluorine-based anionic surfactants, Neos Co., Ltd.), organic solvent propylene glycol monomethyl ether [hereinafter PGM], Japanese emulsifiers (hereinafter PGM) Co., Ltd.) was mixed to prepare an antifogging coating composition. The composition of each anti-fog coating composition is shown in Table 1.

The meanings of the abbreviations in the table are as follows:
ST-OUP: Nissan Chemical Industry Co., Ltd. trade name, colloidal silica ST-UP: Nissan Chemical Industry Co., Ltd. trade name, colloidal silica IPA-ST-UP: Nissan Chemical Industry Co., Ltd. trade name, isopropyl alcohol as a dispersion medium Chain organosilica sol (solid content 15%)
PGM: Propylene glycol monomethyl ether

(2) pH measurement of anti-fog paint composition
The pH of each anti-fog coating composition was measured using a pH meter manufactured by HORIBA, Ltd .: D-53.

(3) Preparation of Anti-Fog Coating Film Each anti-fog coating composition was applied onto a polycarbonate resin plate base material. The coating was carried out by a bar coating method, and the thickness of the anti-fog coating film after the anti-fog coating composition was formed was adjusted to 1 μm. The base material coated with the anti-fog coating composition was placed in an oven at 100 ° C. and water and an organic solvent were evaporated for 5 minutes to form an anti-fog coating film. In this way, each anti-fog coating film test piece was obtained.

(4) Evaluation of stability of anti-fog coating composition Each anti-fog coating composition was placed in a glass sample bottle, left at room temperature for 30 days, and the state of the anti-fog coating composition was visually observed. Those in which no gel, agglomerates, precipitates, etc. were observed were described as "good", and those in which gels, agglomerates, precipitates, etc. were observed were described as "poor".

(5) Evaluation of coatability of anti-fog coating film composition The surface of the anti-fog coating film test piece was visually observed. Those in which a homogeneous coating film was obtained were described as "good", and those in which cissing or the like was observed on the surface of the coating film were described as "poor".

(6) Evaluation of anti-fog property of the coating film An anti-fog coating film test piece is placed at a height of 1 cm from the water surface of a hot water bath at 40 ° C. so that the coating film faces downward, and the coating film is exposed to the hot water bath. I applied steam. After 2 minutes, it was visually observed whether cloudiness was formed on the coating film. Those with no fogging on the surface of the coating film were described as "no fogging", and those with fogging on the surface of the coating film were described as "with fogging".

(7) Evaluation of Change in Appearance of Coating Film After evaluating the anti-fog property of the above-mentioned coating film, the anti-fog coating film test piece was kept standing vertically for 30 minutes and dried. After that, it was visually observed whether or not a water dripping mark was formed on the anti-fog coating film test piece. Steam from a warm water bath was applied to the anti-fog coating film test piece, and the test piece was kept standing vertically for 30 minutes and dried 5 times, and the formation of water dripping marks was visually observed in each test. For those with no dripping marks after the 5th test, "No dripping", for those with dripping marks after the 2nd to 5th tests, "There is dripping after the 2nd test", the 1st test Those with water dripping marks after the above were described as "the first sagging".

The antifogging coating composition according to the embodiment of the present invention in which the blending ratio of the acidic long colloidal silica and the long colloidal silica for pH adjustment was changed formed a coating film having excellent antifogging properties. .. Of these, with respect to the coating films using the anti-fog coating composition of Examples 3 and 4 in which the blending ratio of the acidic long colloidal silica was small, water dripping marks were observed in the fourth and second appearance change tests, respectively. However, the coating film with the anti-fog coating composition of Examples 1 and 2 in which the blending ratio of the acidic long colloidal silica was increased exhibited anti-fog property even after 5 tests.

On the other hand, in the coating film using the anti-fog coating composition of Comparative Example 1 in which only the long colloidal silica for pH adjustment was blended, water dripping marks were observed immediately after the anti-fog evaluation test and the appearance change test of the coating film. rice field. The anti-fog coating composition of Comparative Example 2 containing only acidic long colloidal silica was able to form an excellent coating film that did not form dripping marks, but the stability of the coating liquid was low and storage stability was difficult. was there. The anti-fog coating composition according to Comparative Example 3 containing no surfactant had poor coatability and could not form a coating film. The anti-fog coating composition according to Comparative Example 4 using the organosilica sol dispersed in isopropanol formed a coating film having low anti-fog property.

Claims (5)

An antifogging coating composition containing a mixture of colloidal silica containing acidic elongated colloidal silica and elongated colloidal silica for pH adjustment, and a surfactant, having a pH of 8.0 to 9.7. The antifogging coating composition according to claim 1, wherein the solid content weight ratio of the acidic elongated colloidal silica to the pH adjusting elongated colloidal silica is 1: 4 to 5: 1. The anti-fog coating composition according to claim 1 or 2 , further comprising an organic solvent. An anti-fog coating film formed from the anti-fog coating composition according to claim 1. An anti-fog article comprising a base material and the anti-fog coating film according to claim 4.