JPH0978541A - Reflector for road marker with self-purifying surface - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the reduction of the reflection factor of a reflector by covering the surface of the reflector with a transparent layer containing a semiconductor photocatalyst. SOLUTION: The whole surface of a support layer 18 fixed with retroreflective glass beads 16 is covered with a reflecting film 20 formed by aluminum deposition. The surface of a colored transparent plate 22 is coated with a transparent layer 30 containing grains of a semiconductor photocatalyst. An air layer 24 is provided between the glass beads 16 and the transparent plate 22, and the support layer 18 is fixed to the frame 26 of a line of sight guide marker via an adhesive 28 to form a reflector for a road marker. As the photocatalyst of the transparent layer 30 is excited by the sunlight, the surface of the transparent layer 30 is made hydrophilic, and blots are hardly stuck. The blots stuck to the surface are washed away by rain water at the time of a rainfall. Excellent visibility can be exerted over a long period.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a road sign reflector such as a line of sight guide (deliner). More specifically, the present invention relates to a road sign reflector having excellent visibility at night, in which dirt is unlikely to adhere and the surface is self-cleaned by rainfall.

[0002]

2. Description of the Related Art Reflectors for retroreflecting the light of vehicle headlights are provided on the shoulders and guardrails of roads to facilitate the recognition of roads at night or guide the eyes of the driver. ing.

[0003]

[Problems to be Solved by the Invention] According to the report, the most common opinion written in the sign box provided at the prefectural police headquarters is that the visibility of the reflector is not good. . It is considered that this is because the combustion products in the exhaust gas, tire wear powder, and dirt such as urban dust adhere to the surface of the reflection plate and reduce the reflectance of the reflection plate.

An object of the present invention is to provide a reflector for a road sign which can exhibit excellent visibility for a long period of time.

[0005]

The present inventors have discovered that photoexcitation of a photocatalyst makes the surface of the photocatalyst highly hydrophilic. The present invention is based on such a discovery, and the present invention is
The surface of the reflector for a road sign is coated with a transparent layer containing a semiconductor photocatalyst. During the daytime, the photocatalyst of the road sign reflector is irradiated with the sun and photoexcited by the sunlight. With photoexcitation, the surface of the photocatalyst-containing layer is highly hydrophilized so that the contact angle with water is 10 ° or less, more specifically 5 ° or less, and particularly about 0 °. Once highly hydrophilic, the hydrophilicity of the surface persists at night.

On such a highly hydrophilic surface,
Combustion products in exhaust gas and hydrophobic substances such as tire abrasion powder and urban dust are unlikely to adhere. Since the superhydrophilic surface is not electrostatically charged, dirt is unlikely to adhere. Moreover, the reflector is sometimes exposed to rainfall. Since the affinity of the superhydrophilized surface for water is greater than the affinity for hydrophobic substances such as combustion products and tire abrasion powder,
Dirt adhering to the surface is easily released from the surface by rainwater, washed off by rainwater each time it rains, and the surface is self-cleaning (self-cleaning). In this way, the surface of the reflector is always kept clean, so that the light of the headlight is well reflected and excellent visibility is exhibited.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a gaze guide 12 provided with a reflector 10 for a road sign according to the present invention. The reflector 10 is supported by a support 14 fixed to a road or a guardrail.

Referring to FIG. 2, the reflection plate 10 is provided with a supporting layer 18 to which glass beads 16 for retroreflection having a particle size of, for example, about 50 μm are fixed, and the entire surface of the supporting layer 18 is a reflection layer formed by aluminum vapor deposition. It is covered by the membrane 20. The glass beads 16 are covered with a colored transparent plate 22 made of polycarbonate or the like. In the illustrated embodiment, the reflector 10 is of the so-called "capsule lens" type, and an air layer 24 is provided between the glass beads 16 and the transparent plate 22. The support layer 18 is fixed to the frame 28 of the visual guide 12 by an adhesive 26.

The surface of the transparent plate 22 is coated with a transparent layer 30 containing semiconductor photocatalyst particles. Preferably, the photocatalyst-containing layer 30 has a thickness of about 0.1 μm or less. With such a film thickness, it is possible to prevent the transparent plate 22 from being deteriorated by the photooxidation action of the photocatalyst.
The most preferable photocatalyst is titania (TiO ₂ ). Titania is harmless and chemically stable. Both anatase titania and rutile titania can be used. When the photocatalytic titania photoexcited by UV light, water is a hydroxyl group by photocatalysis (OH ^-)
It is believed that it is chemisorbed to the surface in the form of, resulting in the surface becoming superhydrophilic. Other photocatalysts that can be used include
ZnO, there is a metal oxide such as _{SnO 2, SrTiO 3, WO 3} , Bi 2 O 3, Fe 2 O 3. These metal oxides, like titania, since the metal element and oxygen are present on the surface, the surface hydroxyl (OH ^-) adsorbs considered hungry.

Since the refractive index of titania is considerably higher than that of the plastic such as polycarbonate constituting the transparent plate 22 (refractive index of anatase is 2.52, refractive index of rutile is 2.76), the photocatalyst containing layer 30 is used. When it is formed of only titania, the reflection of light at the interface between the photocatalyst containing layer 30 and the transparent plate 22 becomes remarkable, and the retroreflectance of the reflection plate 10 decreases. Therefore, by adding about 20% by weight of silica to the photocatalyst containing layer 30, the photocatalyst containing layer 3
It is preferable to reduce the difference between the refractive index of 0 and the refractive index of the transparent plate 22.

The silica-containing photocatalyst-containing layer 30 is a precursor of amorphous silica (eg, tetraethoxysilane, tetraisopropoxysilane, tetra-n-propoxysilane,
Tetraalkoxysilanes such as tetrabutoxysilane and tetramethoxysilane; silanols which are hydrolysates thereof; or polysiloxanes having an average molecular weight of 3000 or less)
It can be formed by applying a mixture of the crystalline titania sol and the surface of the transparent plate 22. The amorphous silica precursor is optionally hydrolyzed to form silanol, and then heated at a temperature of about 100 ° C or higher to subject the silanol to dehydration polycondensation, whereby the titania is bound to the amorphous silica. The photocatalyst containing layer 30 is obtained.

The photocatalyst-containing layer 30 of the reflection plate 10 is photoexcited by sunlight in the daytime, and the surface of the photocatalyst-containing layer 30 is made hydrophilic so that the contact angle with water is 10 ° or less, particularly about 0 °. When the entire surface of the support layer 18 is covered with the reflective film 20, the ultraviolet light reflected by the reflective film 20 can be effectively used for exciting the photocatalyst.

On the surface of the photocatalyst containing layer 30 which has been made highly hydrophilic in this way, it is difficult for the combustion products in the exhaust gas and the hydrophobic substances such as tire abrasion powder and urban dust to adhere. Further, the surface of the superhydrophilized photocatalyst-containing layer 30 adsorbs moisture in the air and is not charged by static electricity, so that dirt is less likely to be attached by static electricity. Further, since the contact angle of inorganic substances such as mud and soil with water is 20 ° to 50 °, the photocatalyst-containing layer 30 superhydrophilized to have a contact angle with water of about 0 °. Inorganic dust such as mud and dirt does not adhere easily.

Reflector 10 is occasionally exposed to rainfall. Since the affinity of the surface of the superhydrophilized photocatalyst-containing layer 30 for water is larger than the affinity for hydrophobic substances such as combustion products and tire abrasion powder, dirt attached to the surface of the photocatalyst-containing layer 30 is rainwater. Is released from the surface and washed away with rainwater every time it rains. Since the surface of the photocatalyst-containing layer 30 is self-cleaned in this manner, the retroreflective performance and visibility of the reflector 10 are ensured for a long period of time.

In another embodiment of the present invention, the low refractive index photocatalyst-containing layer 30 can be formed by dispersing photocatalyst particles in silicone (organopolysiloxane) at a ratio of 50% by weight or less. Therefore, it is possible to use a coating composition in which titania particles are dispersed in a film-forming element made of uncured or partially cured silicone or a silicone precursor.

As the film forming element, methyltrichlorosilane, methyltribromosilane, methyltrimethoxysilane, methyltriethoxysilane, methyltriisopropoxysilane, methyltri-t-butoxysilane; ethyltrichlorosilane, ethyltribromosilane, Ethyltrimethoxysilane, ethyltriethoxysilane, ethyltriisopropoxysilane, ethyltrit-butoxysilane; n-propyltrichlorosilane, n-propyltribromosilane, n-propyltrimethoxysilane,
n-propyltriethoxysilane, n-propyltriisopropoxysilane, n-propyltri-t-butoxysilane; n-hexyltrichlorosilane, n-hexyltribromosilane, n-hexyltrimethoxysilane, n
-Hexyltriethoxysilane, n-hexyltriisopropoxysilane, n-hexyltrit-butoxysilane; n-decyltrichlorosilane, n-decyltribromosilane, n-decyltrimethoxysilane, n-decyltriethoxysilane, n -Decyltriisopropoxysilane, n-decyltri-t-butoxysilane; n-octadecyltrichlorosilane, n-octadecyltribromosilane, n-octadecyltrimethoxysilane, n-octadecyltriethoxysilane, n-octadecyltriisopropoxysilane, n-octadecyltri-t-butoxysilane; phenyltrichlorosilane, phenyltribromosilane, phenyltrimethoxysilane, phenyltriethoxysilane, phenyltriisopropoxysilane, phenyltrisilane -Butoxysilane; tetrachlorosilane, tetrabromosilane, tetramethoxysilane, tetraethoxysilane, tetrabutoxysilane, dimethoxydiethoxysilane; dimethyldichlorosilane, dimethyldibromosilane, dimethyldimethoxysilane, dimethyldiethoxysilane; diphenyldisilane Chlorosilane, diphenyldibromosilane, diphenyldimethoxysilane,
Diphenyldiethoxysilane; phenylmethyldichlorosilane, phenylmethyldibromosilane, phenylmethyldimethoxysilane, phenylmethyldiethoxysilane; trichlorohydrosilane, tribromohydrosilane, trimethoxyhydrosilane, triethoxyhydrosilane, triisopropoxyhydrosilane, tri-t -Butoxyhydrosilane; vinyltrichlorosilane, vinyltribromosilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriisopropoxysilane,
Vinyltri-t-butoxysilane; trifluoropropyltrichlorosilane, trifluoropropyltribromosilane, trifluoropropyltrimethoxysilane, trifluoropropyltriethoxysilane, trifluoropropyltriisopropoxysilane, trifluoropropyltrit-butoxysilane; γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyldiethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltriisopropoxy Silane, γ-glycidoxypropyltri-t-butoxysilane; γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryl Riloxypropyltrimethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-methacryloxypropyltriisopropoxysilane, γ-methacryloxypropyltri-t-butoxysilane; γ-aminopropylmethyldimethoxysilane, γ- Aminopropylmethyldiethoxysilane, γ
-Aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-aminopropyltriisopropoxysilane, γ-aminopropyltri-t-butoxysilane; γ-mercaptopropylmethyldimethoxysilane, γ-mercaptopropylmethyldiethoxysilane , Γ-mercaptopropyltrimethoxysilane, γ-
Mercaptopropyltriethoxysilane, γ-mercaptopropyltriisopropoxysilane, γ-mercaptopropyltri-t-butoxysilane; β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, β-
(3,4-Epoxycyclohexyl) ethyltriethoxysilane; their partial hydrolysates; and their mixtures can be used.

When this coating composition is applied to the surface of the transparent plate 22 and the silicone is cured, the titania is photoexcited by irradiation of ultraviolet rays or the sun, and the silicone molecules are formed on the surface of the silicone layer by the action of a photocatalyst. A silicone derivative in which the organic group bonded to the silicon atom is at least partially substituted with a hydroxyl group is formed, and the surface of the silicone layer is superhydrophilized to such an extent that the contact angle with water is about 0 °.

[0018]

[Examples] 0.3 part by weight of liquid B (trimethoxymethylsilane) of silicone coating composition "GLASCA" of Japan Synthetic Rubber and liquid A of "GLASCA" (silica sol, solid content 13%,
pH = 4) 0.9 parts by weight and nitric acid-deflocculating anatase titania sol as a photocatalyst (Nissan Kagaku, TA-15, average crystallite diameter 12 nm, solid content 15%, pH = 1) 1.6 parts by weight , And mixed with 45.2 parts by weight of ethanol as a solvent, and after stirring for 2 hours, trimethoxymethylsilane was partially subjected to hydrolysis and dehydration polycondensation, and applied on a polycarbonate plate by a flow coating method, and then at 100 ° C. The anatase-type titania formed a silicone-dispersed coating by drying at the temperature of.

20 W of black light blue (B
LB) A fluorescent lamp (Sankyo Denki, FL20BLB) was used to irradiate the surface of the sample with ultraviolet light for 5 days at an ultraviolet light intensity of 0.5 mW / cm ² (ultraviolet light intensity higher than the band gap energy of anatase-type titania). The contact angle of water on the surface of this sample was measured with a contact angle measuring instrument (Kyowa Interface Science Co., Ltd., Model CA-X
150, low angle side detection limit 1 °),
The measuring instrument read 0 °, indicating superhydrophilicity.

[0020]

According to the present invention, dirt is prevented from adhering to the reflector for a road sign, and the dirt adhering to the surface is washed away by rainwater each time it rains, and the surface of the reflector is self-cleaned. Therefore, the visibility of the reflector can be improved.

[Brief description of drawings]

FIG. 1 is a front view of a gaze guide provided with a road sign reflector of the present invention.

FIG. 2 is a schematic enlarged cross-sectional view of the reflector shown in FIG.

[Explanation of symbols]

 10: Reflector for road sign 30: Photocatalyst containing layer

Front page continued (72) Inventor Eiichi Kojima 2-1-1 Nakajima, Kokurakita-ku, Kitakyushu, Fukuoka Totoki Equipment Co., Ltd. No. 1 Totoki Co., Ltd. (72) Inventor Atsushi Kitamura 2-1-1 Nakajima, Kokurakita-ku, Kitakyushu, Fukuoka Prefecture Totoki Co., Ltd.

Claims (4)

[Claims] 1. The surface of a reflective plate for a road sign is coated with a transparent layer containing a semiconductor photocatalyst, and the surface of the photocatalyst containing layer is hydrophilized as the photocatalyst is photoexcited by sunlight. A road sign reflector, wherein dirt attached to the surface of the sign reflector is washed off by rainwater when the sign reflector is exposed to rainfall. 2. The reflector for a road sign according to claim 1, wherein the photocatalyst-containing layer is formed of a silica layer in which photocatalyst particles are dispersed. 3. The photocatalyst-containing layer is formed by a silicone layer in which photocatalyst particles are dispersed, and the surface of the silicone layer has an organic group bonded to a silicon atom of a silicone molecule which is at least partially hydroxylated by the action of the photocatalyst. The reflector for a road sign according to claim 1, which is formed of a silicone derivative substituted with. 4. The photocatalyst comprises titania.
Or the reflector for road signs based on 3.