JP3277983B2 - Outdoor display panel and its cleaning method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a traffic sign, an advertising sign, an electric signboard, an aurora vision, a neon sign,
The present invention relates to an outdoor signboard such as a signboard for a shop, a nameplate, etc., and a method of cleaning the same.

[0002]

2. Description of the Related Art Outdoor display panels are contaminated by combustion products in exhaust gas from automobiles and the accumulation of dust floating in the atmosphere. Furthermore, in the rain, floating dust is carried by rain,
When flowing down the surface of the outdoor display panel, contaminants adhere to the surface along the path of rainwater, and when the surface is dried, striped dirt is formed.

[0003]

Such dirt on the outdoor display panel makes it difficult to see the display contents and disturbs the aesthetic view of the city. In addition, since many outdoor display boards are located at a high place, cleaning work is dangerous and time-consuming. An object of the present invention is to provide an outdoor display panel having a surface that is self-cleaned (self-cleaned) by rainfall without a dangerous cleaning operation, and a cleaning method thereof. It is another object of the present invention to provide an outdoor display panel having a surface that can be cleaned by watering or rinsing without dangerous cleaning work, and a method of cleaning the same. Another object of the present invention is to provide an outdoor display panel having a surface to which combustion products and dust are less likely to adhere.

[0004]

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 light having energy equal to or greater than the energy gap between the upper end of the valence band and the lower end of the conduction band of the photocatalyst is irradiated on the photocatalyst, the electrons in the valence band of the photocatalyst are excited to generate conduction electrons and holes. By either or both actions, polarities are probably imparted to the surface and polar components such as water and hydroxyl groups are collected. 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 a self-cleaning outdoor display panel provided with a surface layer containing photocatalyst particles on the surface of the outdoor display panel base material. By providing the surface layer containing the photocatalyst, the surface of the surface layer exhibits hydrophilicity in response to the photoexcitation of the photocatalyst, so that when the surface of the outdoor display panel is exposed to rainfall, deposits and / or contaminants are removed. It can be washed away by raindrops.

The present invention provides an antifouling outdoor display panel having a surface layer containing photocatalyst particles on the surface of an outdoor display panel substrate. By providing the surface layer containing the photocatalyst, the surface of the surface layer exhibits hydrophilicity in response to the photoexcitation of the photocatalyst, so that when rainwater containing the contaminant flows down the surface of the outdoor display panel, the contaminant is exposed to the surface. Is prevented.

The present invention provides an easy-to-clean outdoor display panel having a surface layer containing photocatalyst particles on the surface of an outdoor display panel substrate. By providing the surface layer containing the photocatalyst, the surface of the surface layer exhibits hydrophilicity in response to photoexcitation of the photocatalyst, so that the surface of the outdoor display panel can be easily washed with water.

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 fact that silica can store water in its structure.

In a preferred embodiment of the present invention, the surface layer further contains a solid superacid.
When the super strong acid is contained, the surface is likely to exhibit a high degree of hydrophilicity near a water wetting angle of 0 °, and the hydrophilicity retention when kept in a dark place is improved. The reason is that when a super-strong acid is contained in the surface layer, the polarity of the surface is extremely large regardless of the presence or absence of light, so water molecules that are polar molecules are selectively adsorbed rather than 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 the silicone, at least a part of the organic group bonded to the silicon atom in the silicone is replaced by a hydroxyl group by photoexcitation of the photocatalyst, and further, a physisorbed water layer is formed thereon, whereby the surface is formed. It exhibits a high degree of hydrophilicity near the water wetting angle of 0 °, and improves the hydrophilicity retention when kept in a dark place.

[0011]

Next, a specific configuration of the present invention will be described. On the surface of the outdoor display panel in the present invention,
As shown in FIG. 1 or FIG. 2, a layer containing a photocatalyst is formed on the surface of the substrate. With such a surface structure, the surface of the outdoor display panel is highly hydrophilized in response to photoexcitation of the photocatalyst. Thereby, the hydrophilicity of the surface becomes stronger than the lipophilicity. Thereby, when the surface of the outdoor display panel is exposed to rainfall, attached deposits and / or contaminants are washed away by raindrops. In addition, when rainwater containing the contaminant flows down the surface of the outdoor display panel, the contaminant is prevented from adhering to the surface. Further, it becomes easy to wash the surface of the outdoor display panel with water.

In FIG. 1, when the surface layer comprises only a 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 shows hydrophilicity in a state where the pollutant in the environment is not adsorbed, the pollutant is rejected by a photoexcitation effect of a photocatalyst mixed into the surface layer other than the inorganic oxide,
By forming the adsorbed water layer, a uniform water film can be formed.

The outdoor display panel according to the present invention includes a traffic sign,
Shows advertising billboards, electronic bulletin boards, aurora visions, neon signs, signboards for storefronts, nameplates, etc. The material is plastic base material such as polycarbonate or acrylic, or its painted plate, hard-coated plate; fluorescent display glass, plastic, etc. And the like covered with a transparent body.

A photocatalyst is a device that emits light (excitation light) having an energy (that is, a shorter wavelength) larger than the energy gap between the conduction band and the valence band of the crystal when the electrons in the valence band are irradiated. A substance that can generate conduction electrons and holes by excitation (photoexcitation). Examples thereof include anatase-type titanium oxide, rutile-type titanium oxide, tin oxide, zinc oxide, bismuth trioxide, tungsten trioxide, and tungsten oxide. Ferrous iron, strontium titanate and the like can be suitably used. Here, as a light source used for photoexcitation of the photocatalyst, sunlight; a light source in an environment such as a streetlight or a nightlight; or the like can be used. Here, as the electric lamp, a light source such as a fluorescent lamp, an incandescent lamp, a metal halide lamp, a mercury lamp, or a xenon lamp can be suitably used. In order for the substrate surface to be highly hydrophilized by photoexcitation of the photocatalyst, the illuminance of the excitation light is 0.001 mW /
cm ² suffices above, but preferably that it 0.01 mW / cm ² or more, and more preferably it 0.1 mW / cm ² or more.

The thickness of the surface layer containing the photocatalyst is 0.4
It is preferable that the thickness be not more than μm. Then, cloudiness 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. Then, it is possible to prevent the surface layer from being colored by light interference. 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.

A metal such as Ag, Cu or 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 includes 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 superacid is added in addition to the photocatalyst, the acidity of the solid superacid is improved by the addition of a platinum group metal, so that the hydrophilicity retention property is also improved, and the formation of a film of attached water is further promoted. In addition, the hydrophilicity retention when the photocatalyst is not irradiated with the excitation light for a relatively long period of time is also improved.

When the substrate is a glass containing an alkali network modifying ion such as sodium (soda lime glass, side-by-side 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 being easily conformed when water is dropped on the surface, and generally refers to 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, self-cleaning, easy cleaning with water,
PCT / JP96 / 00 for prevention of dirt adhesion due to rainfall
As disclosed in No. 734, the water wetting angle is preferably 10 ° or less, more preferably 5 ° or less.

In the present invention, the solid superacid is a strong acid containing a solid oxide having a Hammett acidity function Ho ≦ −11.93 as a constituent element.
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 or the like can be suitably used.

Next, a method for forming the surface layer will be described. First, a production method in the case where the surface layer is composed of only a photocatalyst will be described with reference to an example in which the photocatalyst is an anatase type titanium oxide. 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 A hydrolysis inhibitor (hydrochloric acid, ethylamine, etc.) is added to an organic titanate such as titanium alkoxide (tetraethoxytitanium, tetramethoxytitanium, tetrapropoxytitanium, tetrabutoxytitanium, etc.), titanium acetate, titanium chelate, etc. , After diluting with a non-aqueous solvent such as alcohol (ethanol, propanol, butanol, etc.) and then partially or completely allowing hydrolysis to proceed, the mixture is spray-coated, dip-coated, Apply by flow coating, spin coating, roll coating, etc.
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 Deposition Method An amorphous titanium oxide layer is formed on the surface of a base material 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 with reference to the case where the photocatalyst is an anatase type titanium oxide. In this case, for example, there are the following three methods. One method is a sol coating and baking method, the other is an organic titanate method, and the other is a 4 method.
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 A hydrolysis inhibitor (hydrochloric acid, ethylamine, etc.) and silica sol are added to an organic titanate such as titanium alkoxide (tetraethoxytitanium, tetramethoxytitanium, tetrapropoxytitanium, tetrabutoxytitanium, etc.), titanium acetate, titanium chelate, etc. 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 an anatase-type titanium oxide sol is spray-coated on the surface of the substrate, and dip-coated. After applying by a method such as a flow coating method, a spin coating method, and a roll coating method, and hydrolyzing as necessary to form a silanol, the 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 superacid is described with reference to the case where the photocatalyst is anatase type titanium oxide and the solid superacid is TiO ₂ / WO ₃ . In this case, a method of mixing an ammonia solution of tungstic acid and an anatase-type titanium oxide sol and, if necessary, diluting the mixture with a diluting liquid (water, ethanol, etc.) on the surface of the base material by spray coating, dip coating, or the like. It is applied by a method such as a flow coating method, a spin coating method, and a roll coating method, and is baked.

Next, the case where the surface layer is made of a photocatalyst and silicone will be described with reference to the case where the photocatalyst is anatase type titanium oxide. The method in this case is to mix a coating of uncured or partially cured silicone or a silicone precursor with an anatase-type titanium oxide sol, hydrolyze the silicone precursor if necessary, and then mix the mixture. Spray coating method on the surface of the substrate,
Dip coating method, flow coating method, spin coating method, applied by a method such as roll coating method, by subjecting the hydrolyzate of the silicone precursor to dehydration polycondensation by a method such as heating, anatase type titanium oxide particles and A surface layer made of silicone is formed. In the formed surface layer, at least a part of the organic group bonded to the silicon atom in the silicone molecule is replaced with a hydroxyl group by photoexcitation of the anatase type titanium oxide by irradiation with light including ultraviolet rays, and further thereon. The physical adsorption water layer is formed,
It exhibits a high degree of hydrophilicity. Here, silicone precursors include methyltrimethoxysilane, methyltriethoxysilane, methyltributoxysilane, methyltripropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltributoxysilane, ethyltripropoxysilane, 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 First, a primer paint (Toshiba Silicone, a paint obtained by diluting PH93 6 times with a toluene solvent) was applied to the surface of a 10 cm square PMMA plate by a spray coating method, and then dried at room temperature. Layer. Next, a silicone hard coating agent (Toshiba Silicone, Tosgard) was applied by a flow coating method, and dried at 90 ° C. for 3 hours to form a hard coat layer on the primer resin layer. Further, the surface of the hard coat layer was treated with a corona surface treatment device (Kasuga Electric) using a wire electrode as the electrode, a gap of 2 mm between the electrode tip and the sample surface, a voltage of 26 kV, a frequency of 39 kHz, and a sample feed speed of 4.2 m / min. Under the conditions, a high-frequency corona discharge treatment was performed to obtain a # 1 sample. On the other hand, 56 parts by weight of anatase-type titanium oxide sol (Nissan Chemical Co., TA-15, average particle size 12n)
m) and 33 parts by weight of silica sol (Nippon Synthetic Rubber, Glasca A solution), and after dilution with ethanol, 11 parts by weight of methyltrimethoxysilane (Nippon Synthetic Rubber, Glaska B)
Liquid) was added to prepare a coating composition containing titanium oxide.
The above coating composition was applied to a # 1 sample by a flow coating method, and cured by heat treatment at 90 ° C. for 3 hours.
A sample was obtained. This # 2 sample was placed in an ultraviolet light source (Sankyo Electric,
The surface of the sample was irradiated with ultraviolet light at an ultraviolet illuminance of 0.6 mW / cm ² for about 48 hours using a black light blue (BLB) fluorescent lamp) to obtain a # 3 sample. 10c for comparison
An m square PMMA plate sample was also prepared. First, sample # 3 and P
A water drop was dropped on the MMA plate 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 water droplets were dropped on the sample surface from the microsyringe of the three samples, it was observed that the water droplets spread uniformly over the sample surface 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 PMMA plate sample, when a water drop was dropped on the sample surface from the microsyringe, the water drop slightly adapted to the surface, but did not reach a uniform water film state. The contact angle with water after 30 seconds was 60 °.

Next, 1 part by weight of hydrophobic carbon black,
A slurry was prepared by suspending a powder mixture consisting of 1 part by weight of hydrophilic carbon black in water at a concentration of 1.05 g / liter. # 3 sample and PMMA inclined at 45 degrees
150 ml of the above slurry was allowed to flow down to the plate sample and dried for 15 minutes, and then 150 ml of distilled water was allowed to flow down and dried for 15 minutes. This cycle was repeated 25 times. The color difference change before and after the test was measured using a color difference meter (Tokyo Denshoku).
The color difference is ΔE according to Japanese Industrial Standards (JIS) H0201.
* Indication was used. As a result, while the color difference change was as large as 22 in the PMMA plate sample, the color difference change was only 0.6 in the # 3 sample.

[0026]

According to the present invention, on the surface of the outdoor display panel base material,
By providing the surface layer containing the photocatalyst particles, the surface of the outdoor display panel exhibits a high degree of hydrophilicity according to the photoexcitation of the photocatalyst, and is self-cleaned (self-cleaning) by rainfall, or sprayed or rinsed with water. It is possible to clean by a certain degree, or it becomes difficult for combustion products and dust brought by rainwater to adhere.

[Brief description of the drawings]

FIG. 1 is a diagram showing a surface structure of an outdoor display panel according to the present invention.

FIG. 2 is a diagram showing another surface structure of the outdoor display panel according to the present invention.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-7-171408 (JP, A) JP-A-6-266289 (JP, A) JP-A-6-278241 (JP, A) JP-A-62-1987 260717 (JP, A) JP-A-60-151250 (JP, A) JP-A-9-90889 (JP, A) JP-A-5-302173 (JP, A) JP-A-7-113272 (JP, A) JP-A-7-171403 (JP, A) JP-A-63-100042 (JP, A) JP-A-63-5301 (JP, A) JP-A-4-174679 (JP, A) JP-A-60-210641 (JP, A) JP-A-7-88367 (JP, A) JP-A-7-100378 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G09F 7/00 C09K 3 / 18

Claims (15)

(57) [Claims] A surface layer containing photocatalyst particles is provided on the surface of a substrate of an outdoor display panel, and the surface of said layer has a contact angle with water of 10 ° or less in response to photoexcitation of said photocatalyst. A self-cleaning outdoor display panel which exhibits a hydrophilic nature, thereby enabling attached deposits and / or contaminants to be washed away by raindrops when said layer of the outdoor display panel is exposed to rainfall. 2. A surface layer containing photocatalyst particles is provided on the surface of an outdoor display panel base material, and the surface of the layer has a contact angle with water of 10 ° or less in response to photoexcitation of the photocatalyst. An antifouling outdoor display panel having a hydrophilic property and preventing contaminants from adhering to the surface when rainwater containing the contaminant flows down the layer surface of the outdoor display panel. 3. A surface layer containing photocatalyst particles is provided on the surface of the outdoor display panel base material, and the surface of the layer is 10 ° or less in terms of a contact angle with water according to the photoexcitation of the photocatalyst. An easy-to-clean outdoor display panel having a hydrophilic property, whereby the surface of the layer of the outdoor display panel can be easily washed with water. 4. The outdoor display panel according to claim 1, wherein the surface layer further contains silica. 5. The outdoor display panel according to claim 1, wherein the surface layer further contains a solid superacid. 6. The outdoor display panel according to claim 1, wherein the surface layer further contains silicone. 7. A surface according to claim 1, wherein the surface of the surface layer exhibits a hydrophilicity of 5 ° or less in terms of a contact angle with water in response to photoexcitation of the photocatalyst. The outdoor display panel according to claim 1. 8. The outdoor display panel according to claim 1, wherein the thickness of the surface layer is 0.4 μm or less. 9. The outdoor display panel according to claim 1, wherein the thickness of the surface layer is 0.2 μm or less. 10. The method according to claim 1, wherein a protective layer capable of being made hydrophilic is further provided on the surface of the surface layer.
An outdoor display panel according to any one of claims 1 to 6. 11. The outdoor display panel according to claim 1, wherein the outdoor display panel is a traffic sign. 12. The outdoor display panel according to claim 1, wherein the outdoor display panel is an advertisement signboard. 13. The outdoor display panel according to claim 1, wherein the outdoor display panel is an electronic bulletin board. 14. A step of preparing the outdoor display panel according to claim 1; arranging the outdoor display panel outdoors; and photo-exciting a photocatalyst contained in a surface layer of the outdoor display panel, The surface of the layer is converted into a contact angle with water to be 1
Self-cleaning of the outdoor display panel, the method comprising: exposing the outdoor display panel to rainfall to wash off deposits and / or contaminants adhering to the surface of the layer by raindrops; Method. 15. A step of preparing the outdoor display panel according to claim 1, wherein the photocatalyst contained in the surface layer of the outdoor display panel is photo-excited to convert the surface of the layer into a contact angle with water. Rinsing the outdoor display panel with water to release sediment and / or contaminants adhering to the surface of the layer from the surface and to wash it off with water; A method for cleaning an outdoor display panel comprising: