JPH09228134A - Antifogging helmet shield and antifogging method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an antifogging helmet shield having a transparent surface layer containing photocatalyst particles on the surface of a helmet shield substrate, exhibiting hydrophilic nature according to light excitation to uniformly spread the condensed water attached to the surface, effective for preventing the fogging and having improved functionality. SOLUTION: An essentially transparent surface layer containing photocatalyst particles such as anatase titanium oxide (the thickness of the surface layer is preferably <=0.4μm) is formed on the surface of a helmet shield substrate. The surface of the surface layer exhibits hydrophilic nature according to the light excitation of the photocatalyst. The surface layer preferably further contains silica, a solid acid and a silicone and the refractive index of the surface layer is preferably <=2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-fogging helmet shield and a method for anti-fogging a helmet shield.

[0002]

2. Description of the Related Art A helmet shield for motorcycles receives rain or splashes, and discrete water droplets adhere to the surface thereof, and the surfaces thereof are covered, blurred, mottled, clouded, or lost in visibility. Is often experienced.
In addition, the helmet shield may become cloudy due to sighing in cold weather or in the rain, and visibility may be lost. Generally, the surface of an article is fogged because when the surface is placed at a temperature below the dew point of the atmosphere, moisture in the atmosphere condenses and condenses on the surface. If the condensed water droplets are sufficiently fine and their diameter is about 1/2 of the wavelength of visible light, the water droplets scatter light, the helmet shield becomes apparently opaque, and visibility is lost. If moisture condensation proceeds further and fine condensed water droplets coalesce with each other to grow into larger discrete water droplets, the surface will be shaded due to refraction of light at the water droplet-surface interface and the water-air interface. Blurred, mottled, or cloudy with no visibility. As used herein, the term "anti-fog" broadly refers to a technique for preventing optical hindrance due to such fogging, growth of condensed water droplets, and adhesion of water droplets.

As is well known, the conventionally used antifogging method is to apply an antifogging composition containing a hydrophilic compound such as polyethylene glycol or a water repellent compound such as silicone to the surface. . However, this kind of anti-fog coating is only temporary, and has the drawback that it is easily removed by washing or contact and loses its effect early.

[0004]

When the visibility of the helmet shield is lost as described above, it hinders the safe driving of the motorcycle. Then, the objective of this invention is providing the helmet shield which can implement | achieve a high degree of visibility, and its anti-fog method. Another object of the present invention is to provide a helmet shield capable of maintaining a high degree of hydrophilicity for a long period of time and exhibiting an antifogging property, and a method of preventing the same. Another object of the present invention is to provide a helmet shield capable of maintaining a high degree of hydrophilicity almost permanently and exhibiting anti-fogging property, and a method for preventing the same.

[0005]

SUMMARY OF THE INVENTION The present invention is based on the discovery that, in a member having a surface layer containing a photocatalyst formed thereon, when the photocatalyst is photoexcited, the surface of the member is highly hydrophilized. This phenomenon is considered to proceed by the following mechanism. That is, when the photocatalyst is irradiated with light having an energy larger than the energy gap between the valence band upper end and the conduction band lower end of the photocatalyst, the electrons in the valence band of the photocatalyst are excited to generate conduction electrons and holes. The action of either or both of them probably imparts polarity to the surface and collects polar components such as water and hydroxyl groups. Then, one or both of conduction electrons and holes and the above-mentioned polar component cooperate with each other to cut off a chemical bond between the surface and the contaminant chemically adsorbed on the surface, and to cause a chemical adsorbed water on the surface. Is adsorbed, and a physically adsorbed water layer is formed thereon. Further, once the surface of the member is highly hydrophilized, the hydrophilicity of the surface is maintained for a certain period even if the member is kept in a dark place.

The present invention provides an antifog helmet shield having a surface layer containing a substantially transparent photocatalyst on the surface of a helmet shield substrate. By providing a surface layer containing a photocatalyst, in response to photoexcitation of the photocatalyst, the surface of the surface layer exhibits hydrophilicity, the condensed water and / or water droplets of the attached moisture spread evenly on the surface of the layer, Moisture condensate and / or water drops will prevent fogging or overhang.

In a preferred embodiment of the present invention, the surface layer further contains silica. By containing silica, the surface is likely to exhibit a high degree of hydrophilicity near a water wetting angle of 0 °, and the hydrophilicity retention when held in a dark place is improved. The reason seems to be related to the ability of silica to store water in its structure.

In a preferred embodiment of the present invention, the surface layer further contains a solid super strong acid.
By containing a super strong acid, the surface is likely to exhibit a high degree of hydrophilicity close to a water wetting angle of 0 °, and at the same time, the hydrophilicity maintaining property when kept in a dark place is improved. The reason is that when the surface layer contains a super strong acid, the polarity of the surface is extremely large irrespective of the presence or absence of light, so that water molecules, which are polar molecules, are selectively adsorbed over hydrophobic molecules. Easy to make. Therefore, a stable physically adsorbed water layer is easily formed, and even if the layer is kept in a dark place, the hydrophilicity of the surface can be maintained at a high level for a considerably long period.

In a preferred embodiment of the present invention, the surface layer further contains silicone.
By containing silicone, by photoexcitation of the photocatalyst, at least a part of the organic group bonded to the silicon atom in the silicone is replaced with a hydroxyl group, and a physically adsorbed water layer is formed on the organic group, so that the surface is It exhibits a high degree of hydrophilicity close to a water wetting angle of 0 °, and improves the hydrophilicity maintaining ability when kept in a dark place.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Next, a specific structure of the present invention will be described. As shown in FIG. 1 or FIG. 2, a layer containing a photocatalyst is formed on the surface of the base material on the surface of the antifogging helmet shield in the present invention. By taking such a surface structure, the helmet shield surface is highly hydrophilized in response to photoexcitation of the photocatalyst. As a result, even if the moisture in the atmosphere condenses and adheres, it does not grow in the form of water droplets but becomes a uniform water film.
Or, it is prevented from being clouded or covered by water drops.

In FIG. 1, when the surface layer is composed of only the photocatalyst, the photocatalyst is preferably an oxide.
By doing so, the oxide shows hydrophilicity in the state where the pollutants in the environment are not adsorbed, so that the pollutants are rejected by the photoexcitation action and the adsorbed water layer is formed, so that the oxides easily exhibit hydrophilicity. A uniform water film can be formed. In FIG. 2, M represents a metal element. Therefore, in the case of FIG. 2, the outermost surface is made of a general inorganic oxide. Again,
Since the oxide is hydrophilic when the pollutants in the environment are not adsorbed, the photocatalytic titanium oxide mixed into the surface layer other than the inorganic oxide removes the contaminants by the photoexciting action, and the adsorbed water layer Is formed, a uniform water film can be formed.

For the helmet shield substrate of the present invention, transparent plastics such as polycarbonate, acrylic, and other transparent plastics, and transparent plastics such as plastics having a transparent hard coat provided thereon can be preferably used.

A photocatalyst is a photocatalyst of electrons in the valence band when irradiated with light (excitation light) having an energy (that is, a short wavelength) larger than the energy gap between the conduction band and the valence band of the crystal. A substance that is excited (photoexcited) to generate conduction electrons and holes. For example, anatase-type titanium oxide, rutile-type titanium oxide, tin oxide, zinc oxide, dibismuth trioxide, tungsten trioxide, and oxide oxide. Diiron, strontium titanate and the like can be preferably used. Here, as the light source used for photoexcitation of the photocatalyst, sunlight, street lights, night lights, light sources in the running environment such as tunnel lighting may be used, or a light source that can emit excitation light as auxiliary equipment or portable equipment. May be used. Further, a storage container dedicated to the helmet shield of the present invention may be provided, and a light source capable of emitting excitation light may be installed therein. The light source used in that case is, for example, an incandescent lamp, a metal halide lamp,
A mercury lamp, a xenon lamp, a germicidal lamp, a fluorescent lamp and the like can be preferably used. In order to make the surface of the base material highly hydrophilic by photoexcitation of the photocatalyst, the illuminance of the excitation light is 0.001
It suffices if mW / cm ² or more, but 0.01 mW / cm ²
It is preferable that it is at least 0.1 mW / cm ² and more preferable.

The film thickness of the surface layer containing the photocatalyst is 0.4.
It is preferable that the thickness is less than or equal to μm. Then, white turbidity due to irregular reflection of light can be prevented, and the surface layer becomes substantially transparent. More preferably, the thickness of the surface layer containing the photocatalyst is 0.2 μm or less. that way,
Coloring of the surface layer due to light interference can be prevented.
Also, the thinner the surface layer, the better its transparency. Further, when the film thickness is reduced, the wear resistance of the surface layer is improved. The surface of the surface layer may be further provided with a wear-resistant or corrosion-resistant protective layer capable of being made hydrophilic and other functional films.

The surface layer preferably has a refractive index that is not so high as that of the substrate. Preferably, the refractive index of the surface layer is 2 or less. Then, light reflection at the interface between the substrate and the surface layer and the interface between the surface layer and air can be suppressed. In order to reduce the refractive index of the surface layer to 2 or less, a substance having a refractive index of 2 or less is used for the photocatalyst, or if the photocatalyst has a refractive index of 2 or more, another substance having a refractive index of 2 or less is used for the surface layer. To be added. As a photocatalyst having a refractive index of 2 or less, tin oxide (refractive index: 1.9) or the like can be used. 2
Photocatalysts having the above refractive index include anatase type titanium oxide (refractive index 2.5) and rutile type titanium oxide (refractive index 2.7). In this case, other substances having a refractive index of 2 or less, For example, calcium carbonate (refractive index 1.6), calcium hydroxide (refractive index 1.6), magnesium carbonate (refractive index 1.5), strontium carbonate (refractive index 1.5), dolomite (refractive index 1.7). ), Calcium fluoride (refractive index 1.4), magnesium fluoride (refractive index 1.4), silica (refractive index 1.5), alumina (refractive index 1.6), silica sand (refractive index 1.6). ), Montmorillonite (refractive index 1.
5), kaolin (refractive index 1.6), sericite (refractive index 1.6), zeolite (refractive index 1.5), tin oxide (refractive index 1.9) and the like may be added to the surface layer.

Metals such as Ag, Cu and Zn can be added to the surface layer. The surface layer to which the metal is added can kill bacteria and fungi attached to the surface even in a dark place.

The surface layer has pt, Pd, Ru, R
A platinum group metal such as h, Ir, Os can be added. The surface layer to which the metal is added can enhance the oxidation-reduction activity of the photocatalyst and improve the deodorizing and purifying action and the like. In addition, when a solid acid is added in addition to the photocatalyst, the acidity of the solid acid is improved by the addition of a platinum group metal, so that the hydrophilicity is also improved, and the formation of a water film on the attached water is further promoted. The hydrophilicity when the excitation light is not irradiated to the photocatalyst for a long period of time is also improved. Mo can be added to the surface layer. When a solid acid is added in addition to the photocatalyst, the addition of Mo increases the acidity of the solid acid, so that the hydrophilicity is also improved, and the formation of a water film on the attached water is further promoted. The hydrophilicity when light is not irradiated is also improved.

When the substrate is a glass containing alkali network modifying ions such as sodium (soda lime glass, parallel plate glass, etc.), an intermediate layer such as silica may be formed between the substrate and the surface layer. Good. Then, the diffusion of the alkali network modifying ions from the base material to the surface layer during the firing is prevented, and the photocatalytic function is more effectively exhibited.

The term "hydrophilic" refers to the property of easily fitting into the surface when water is dropped, and generally means a state where the water wetting angle is less than 90 °. The term “high hydrophilicity” in the present invention refers to a property that is highly compatible when water is dropped on the surface, and more specifically, a state where the water wetting angle is about 10 ° or less. In particular, as disclosed in PCT / JP96 / 00734, the water wetting angle is preferably 10 ° or less, more preferably 5 ° or less, as disclosed in PCT / JP96 / 00734.

The solid acid used in the present invention includes Al carrying sulfuric acid.
₂ O ₃ , sulfuric acid supported TiO ₂ , sulfuric acid supported ZrO ₂ , sulfuric acid supported SnO ₂ , sulfuric acid supported Fe ₂ O ₃ , sulfuric acid supported SiO ₂ ,
Sulfuric acid supporting HfO ₂ , TiO ₂ / WO ₃ , WO ₃ / SnO
₂ , WO ₃ / ZrO ₂ , WO ₃ / Fe ₂ O ₃ , SiO _{2
· Al 2 O 3, TiO 2} / SiO 2, TiO 2 / Al 2
O ₃ , TiO ₂ / ZrO _{2 and the} like can be preferably used.

Next, a method for forming the surface layer will be described. First, the production method in the case where the surface layer is composed of only the photocatalyst will be described by taking the case where the photocatalyst is anatase type titanium oxide as an example. In this case, there are roughly three methods. One method is a sol coating and firing method, the other method is an organic titanate method, and the other method is an electron beam evaporation method. (1) Sol-coating and firing method Anatase-type titanium oxide sol is applied to the surface of a substrate by a method such as spray coating, dip coating, flow coating, spin coating, or roll coating, and then fired. (2) Organic titanate method Titanium alkoxide (tetraethoxy titanium, tetramethoxy titanium, tetrapropoxy titanium, tetrabutoxy titanium, etc.), titanium acetate, titanium chelate, etc. are added with a hydrolysis inhibitor (hydrochloric acid, ethylamine, etc.). , After diluting with a non-aqueous solvent such as alcohol (ethanol, propanol, butanol, etc.), while partially or completely proceeding the hydrolysis, the mixture is spray-coated, dip-coated, Apply by methods such as flow coating method, spin coating method, roll coating method,
dry. By drying, the hydrolysis of the organic titanate is completed to produce titanium hydroxide, and a layer of amorphous titanium oxide is formed on the surface of the base material by dehydration-condensation polymerization of the titanium hydroxide. Thereafter, the amorphous titanium oxide is calcined at a temperature equal to or higher than the crystallization temperature of anatase to cause a phase transition from the amorphous titanium oxide to the anatase titanium oxide. (3) Electron beam evaporation method An amorphous titanium oxide layer is formed on the surface of a substrate by irradiating a titanium oxide target with an electron beam. After that, firing at a temperature higher than the crystallization temperature of anatase,
Phase transition of amorphous titanium oxide to anatase titanium oxide.

Next, the case where the surface layer is composed of a photocatalyst and silica will be described by taking the case where the photocatalyst is anatase type titanium oxide as an example. In this case, for example, there are the following three methods. One method is the sol coating firing method, the other is the organic titanate method, the other is 4
This is a functional silane method. (1) Sol coating and baking method A mixture of anatase-type titanium oxide sol and silica sol is applied to the substrate surface by a method such as a spray coating method, a dip coating method, a flow coating method, a spin coating method, and a roll coating method, and then fired. I do. (2) Organic titanate method Titanium alkoxides (tetraethoxytitanium, tetramethoxytitanium, tetrapropoxytitanium, tetrabutoxytitanium, etc.), titanium acetate, titanium chelate, and other organic titanates are added with a hydrolysis inhibitor (hydrochloric acid, ethylamine, etc.) and silica sol. Add alcohol (ethanol,
After diluting with a non-aqueous solvent such as propanol, butanol, etc., and then allowing the hydrolysis to proceed partially or completely, the mixture is spray-coated, dip-coated, flow-coated,
It is applied by a method such as spin coating or roll coating and dried. By drying, the hydrolysis of the organic titanate is completed to produce titanium hydroxide, and a layer of amorphous titanium oxide is formed on the surface of the base material by dehydration-condensation polymerization of the titanium hydroxide. Thereafter, the amorphous titanium oxide is calcined at a temperature equal to or higher than the crystallization temperature of anatase to cause a phase transition from the amorphous titanium oxide to the anatase titanium oxide. (3) Tetrafunctional silane method A mixture of tetraalkoxysilane (tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, tetramethoxysilane, etc.) and anatase type titanium oxide sol is spray-coated or dip-coated on the surface of a substrate. , A flow coating method, a spin coating method, a roll coating method, or the like, and if necessary, hydrolyzing to form silanol, and then silanol is subjected to dehydration condensation polymerization by a method such as heating.

Next, the case where the surface layer is composed of a photocatalyst and a solid acid will be described by taking as an example the case where the photocatalyst is anatase type titanium oxide and the solid acid is TiO ₂ / WO ₃ . In this case, the ammonia solution of tungstic acid and anatase type titanium oxide sol are mixed, and if necessary, a mixture diluted with a diluent (water, ethanol, etc.) is spray-coated or dip-coated on the surface of the substrate. Law,
It is applied by a method such as a flow coating method, a spin coating method, a roll coating method or the like, and baked.

Next, the case where the surface layer is composed of a photocatalyst and silicone will be described by taking the case where the photocatalyst is anatase type titanium oxide as an example. The method in this case is to mix a coating composed of uncured or partially cured silicone or a precursor of silicone and anatase type titanium oxide sol, and hydrolyze the precursor of silicone as needed, and then mix the mixture. Spray coating method on the surface of the substrate,
It is applied by a method such as a dip coating method, a flow coating method, a spin coating method, a roll coating method, etc., and a hydrolyzate of a silicone precursor is subjected to dehydration polycondensation by a method such as heating to obtain anatase type titanium oxide particles. A surface layer made of silicone is formed. The formed surface layer, by photoexcitation of anatase type titanium oxide by irradiation with light including ultraviolet rays, at least a part of the organic group bonded to the silicon atom in the silicone molecule is substituted with a hydroxyl group, and further on it. A physically adsorbed water layer is formed,
It exhibits a high degree of hydrophilicity. Here, the precursor of silicone includes methyltrimethoxysilane, methyltriethoxysilane, methyltributoxysilane, methyltripropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltributoxysilane, ethyltripropoxysilane, and phenyl. Trimethoxysilane, phenyltriethoxysilane, phenyltributoxysilane,
Phenyltripropoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldibutoxysilane, dimethyldipropoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, diethyldibutoxysilane, diethyldipropoxysilane, phenylmethyldimethoxysilane, phenylmethyl Diethoxysilane, phenylmethyldibutoxysilane, phenylmethyldipropoxysilane, γ-glycidoxypropyltrimethoxysilane, a hydrolyzate thereof, and a mixture thereof can be suitably used.

[0025]

EXAMPLE A primer coating (Shin-Etsu Silicone, PC-7A) was applied on a 10 cm square polycarbonate plate by a flow coating method, and then dried at 120 ° C. for 20 minutes,
The substrate was coated with a primer resin layer. Next, a silicone-based hard coating agent (Shin-Etsu Silicone, KP-8
After applying 5) by flow coating,
It was dried for 0 minutes to form a hard coat layer. Next, after the hard coat layer is subjected to corona discharge treatment, a titanium oxide-containing coating composition (anatase type titanium oxide sol (Nissan Chemical,
TA-15) 56 parts by weight and silica sol (Japan Synthetic Rubber,
(Grasca solution A) (33 parts by weight), diluted with ethanol, and further added with 11 parts by weight of trimethoxysilane (Nippon Synthetic Rubber, solution of Glasca solution B)) by a flow coating method, and then at 120 ° C. for 30 minutes. A sample was obtained by heat treatment and curing. After leaving this sample in the dark for several days,
UV light source (Sankyo Electric, Black Light Blue (BL
B) 0.5 mW / cm ^{2 on} the surface of the sample using a fluorescent lamp)
The sample was irradiated with ultraviolet rays at an ultraviolet illuminance of about 1 hour to obtain a # 1 sample. For comparison, a # 2 sample in which a 10 cm square polycarbonate plate was left in the dark for several days was also prepared. First, a water drop was dropped on the # 1 sample and the # 2 sample, and the state after the drop was observed and the contact angle with water was measured. Here, the contact angle with water is measured using a contact angle measuring device (Kyowa Interface Science, CA-X150).
Evaluation was made based on the contact angle with water 30 seconds after dropping. as a result#
When a water droplet was dropped from the microsyringe on one surface of one sample, it was observed that the water droplet spreads uniformly on the surface of the sample in the form of a water film. Further, the contact angle with water after 30 seconds was highly hydrophilized to about 0 °. On the other hand, in the case of the # 2 sample, when a water drop was dropped on the sample surface from the microsyringe, the water droplet adapted to the surface but did not reach a uniform water film state. The contact angle with water after 30 seconds is 6
It was 0 °. Next, the # 1 sample and the # 2 sample were blown to examine whether or not clouding occurred. As a result, fogging occurred in the # 2 sample, but no fogging occurred in the # 1 sample.
Further, the # 1 sample was left in the dark for 2 days thereafter,
A sample was obtained. Then, for the # 3 sample, the contact angle with water was similarly measured by a contact angle measuring device. As a result, when a water drop was dropped on the sample surface from the microsyringe on the # 3 sample, it was observed that the water droplet spread uniformly on the sample surface like a # 1 sample. The contact angle with water was maintained at about 3 °. Next, the presence or absence of fogging after spraying was observed for the # 3 sample. As a result, no fogging was observed.

[0026]

According to the present invention, the helmet shield surface is provided with the surface layer containing the substantially transparent photocatalytic titanium oxide particles, so that the photocatalyst can be photoexcited in response to photoexcitation.
The surface of the surface layer is hydrophilic, so that condensed water and / or water droplets of the adhered moisture are spread evenly on the surface of the layer to prevent the condensed water of moisture and / or water droplets from clouding or covering. become.

[Brief description of drawings]

FIG. 1 is a diagram showing a surface structure of an antifogging helmet shield according to the present invention.

FIG. 2 is a view showing another surface structure of the antifogging helmet shield according to the present invention.

Claims (10)

[Claims] 1. A helmet shield substrate surface is provided with a surface layer containing substantially transparent photocatalyst particles, and the surface of the layer exhibits hydrophilicity in response to photoexcitation of the photocatalyst, and the wetted layer is adhered. An anti-fog helmet shield, wherein minute condensed water and / or water droplets spread evenly on the surface of the layer and are prevented from being fogged or covered by the moisture condensed water and / or water droplets. 2. The anti-fog helmet shield according to claim 1, wherein the surface layer further contains silica. 3. The anti-fog helmet shield according to claim 1, wherein the surface layer further contains a solid acid. 4. The anti-fog helmet shield according to claim 1, wherein the surface layer further contains silicone. 5. The surface of the surface layer exhibits hydrophilicity of 10 ° or less in terms of contact angle with water in response to photoexcitation of the photocatalyst. Anti-fog helmet shield. 6. The antifogging helmet shield according to claim 1, wherein the surface layer has a thickness of 0.4 μm or less. 7. The antifog helmet shield according to claim 1, wherein the surface layer has a thickness of 0.2 μm or less. 8. A hydrophilic protective layer is further provided on the surface of the surface layer.
The anti-fog helmet shield described in 5. 9. The antifog helmet shield according to claim 1, wherein the surface layer has a refractive index of 2 or less. 10. The step of preparing the helmet shield according to claim 1, wherein the photocatalyst contained in the surface layer of the helmet shield is photoexcited to make the surface of the layer hydrophilic, and the wetted layer is adhered. Anti-fog method for a helmet shield, which comprises the step of allowing minute condensed water and / or water droplets to spread uniformly on the surface of the layer.