JPH10255510A - Vehicular headlamp lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a headlamp lens having an antifouling function. SOLUTION: A thin film composed chiefly of titanium oxide and having the function of a photocatalyst is formed on at least a portion of an irregularly shaped lens surface. Dirt is removed as it is decomposed by ultraviolet radiation on the surface of the thin film. The lens may be made of glass or synthetic resin. The titanium oxide may be in the form of fine particles or generated by the thermal decomposition of an alkoxide of titanium on the lens surface. The thickness of the thin film is preferably from 5 to 3000nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a lens used for a headlight for a vehicle such as an automobile.

[0002]

2. Description of the Related Art Conventionally, a vehicle headlamp generally includes a lens, a light source, and a reflector, and the lens portion gives glare to an oncoming vehicle with light emitted from a light source bulb. Since it is necessary to transmit light efficiently and reach a distant place, a deformed lens made of glass or transparent synthetic resin is used. In the case of glass, hard or semi-hard glass made of borosilicate glass is generally used, but soft glass such as soda-lime glass may be used in a projector type aspherical lens. In the case of a synthetic resin, polycarbonate or polymethyl methacrylate is generally used as a material capable of satisfying the required transparency and impact strength.

As a light source, a halogen lamp having a small size and a high lamp efficiency has been widely used, but recently, a halogen lamp such as a metal halide lamp or a high-pressure mercury lamp has been used.
An ID (high-intensity discharge) lamp or a xenon lamp has been put to practical use. In addition, HID lamps and xenon lamps emit a greater amount of ultraviolet light together with visible light than halogen lamps, and the above-mentioned synthetic resins such as polycarbonate and polymethyl methacrylate hardly transmit ultraviolet light, Degraded by ultraviolet rays
It is known to yellow. Therefore, when an HID lamp or a xenon lamp is combined with a synthetic resin deformed lens, usually, a strong UV-absorbing bulb or an inner lens as disclosed in, for example, JP-A-3-141501 is used. Ultraviolet rays are not directly irradiated to the outer lens.

[0004] Incidentally, since the lens portion of such a headlight may not be in the driver's field of view during use, the dirt is noticeable compared to other vehicle-mounted glass such as a window glass and a rearview mirror portion. Hateful. For this reason, cleaning tends to be overtaken, and dirt gradually adheres and accumulates, making it very difficult to remove. Furthermore, window treatments and rear-view mirrors are often surface treated with the expectation of a water-repellent effect, whereas ordinary headlights are treated with such surface treatments. Not
The more easily the dirt adhered, the less it was difficult to remove.

If a large amount of such unremovable dirt adheres to the lens portion to lower the transparency, not only the appearance is impaired, but also the illuminance may be reduced. Therefore, at present, measures for preventing dirt have been required even for such a headlight shaped lens.

Incidentally, various methods have been developed so far to prevent the general stain on the glass surface. For example, Japanese Patent Application Laid-Open Nos. Hei 7-289895 and Hei 7-29166 have been developed.
No. 7 discloses a method of coating a glass surface with a fluoroalkylsilane compound in order to expect a water-repellent effect. It is said that the film formed by the above method has a large contact angle with water droplets, so that it is difficult for dirt to adhere to the surface, and even if it does, it can be easily removed by wiping and cleaning.

Further, JP-A-7-300399 and JP-A-7-257938 also disclose glasses which have an antibacterial action by containing silver ions or zinc ions. These methods are
The antibacterial effect of metal ions is used to impart antibacterial properties to glass, thereby preventing contamination of organic substances such as microorganisms.

As a further method of preventing contamination, a method using a photocatalytic substance having an effect of decomposing the contamination has been proposed. As disclosed in, for example, Japanese Patent Application Laid-Open No. 1-169866, a film containing titanium oxide powder is provided on the surface of a bulb of a fluorescent lamp. This method has the features that it can be performed at low cost and that film formation is easy. The mechanism of the contamination prevention is such that the film receives the ultraviolet rays emitted from the lamp, thereby causing the electron holes to move in the titanium oxide, so that the surface has an oxidizing power by the electron transfer reaction thus caused. That is, by the oxidizing power, dirt attached to the surface of the film is decomposed and removed.

However, at present, it is difficult to apply the above-described various methods for preventing contamination to a deformed lens for a headlight as it is.

First, in the case of a method of coating the surface with a film having a water-repellent function, the formed film has a water-repellent effect and is less likely to adhere to dirt. There is also a drawback that dirt is conspicuous as it shrinks and becomes sticky as it is. Further, a coating liquid using fluorosilicone or the like is expensive, and it is very disadvantageous in terms of cost to use it for a deformed lens having a large area. Moreover, once adhered and solidified dirt hardly disappears naturally, it has to be cleaned eventually, and it is difficult to remove the sticky dirt.

Next, the antifouling measures utilizing the antibacterial action of metal ions keep the metal in an ion state and elute it to the outside, so that applicable glass and film compositions are limited. However, it may not be applicable for chemical and optical reasons. In addition, the effect is observed only when the ions are present on the surface, and the effect is limited although the elution is gradually performed over a long period of time. Furthermore, even if it is effective for dirt derived from microorganisms and the like, it is difficult to expect an effect for dirt on a headlight lens to which a large amount of wax or oil adheres.

[0012]

Therefore, studies were made on the application of a titanium oxide thin film to a headlight lens.
That is, this thin film is formed on the surface of a deformed lens for a headlight, and the dirt attached to the surface of the film is decomposed and removed using the photocatalytic effect of titanium oxide, thereby preventing the surface of the deformed lens from being contaminated. It was investigated.

JP-A-60-52939 discloses a window glass provided with an ultraviolet shielding film as an example in which a titanium oxide thin film is applied to glass for vehicles.
This uses the fact that titanium oxide, vanadium oxide, and the like are ultraviolet absorbing materials, and attempts to cut off ultraviolet rays of sunlight hitting a driver. By forming a thin film of titanium oxide on the surface of a window glass by vacuum evaporation, it is said that the UV-B region which is particularly harmful to the human body is 315 to 315.
The effect of blocking ultraviolet rays in the wavelength range of 290 nm is obtained.

However, the above-mentioned method of forming a titanium oxide thin film can be satisfactorily carried out on a simple, generally planar object such as a window glass, but is applicable to a headlight shaped lens having a complicated shape. It has been difficult to apply it as it is because of limitations in the process and the like.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the conventional deformed lens for a headlamp, and a titanium oxide film having a photocatalytic effect is efficiently formed on the surface so that even if dirt adheres to the surface, ultraviolet rays may be emitted. It is an object of the present invention to provide a headlight lens for a vehicle, which is capable of being naturally decomposed by photodecomposition and maintaining transparency naturally.

[0016]

A headlight lens for a vehicle according to the present invention is characterized in that a thin film mainly composed of titanium oxide and having a photocatalytic function is formed on at least a part of the surface of the headlight lens. I have.

In the present invention, when a titanium oxide thin film is formed on a lens surface, titanium oxide fine particles that have already been crystallized are dispersed in a solvent such as ethyl alcohol, isopropyl alcohol, or acetic acid to prepare a coating solution. A spray (spray coat) may be applied to the surface of the substrate made of glass or synthetic resin by using a spray. Alternatively, a coating liquid containing an alkoxide of titanium may be prepared and spray-coated on the surface of the lens to be heated in advance in the same manner, so that titanium oxide can be formed on the surface of the substrate by a so-called sol-gel method. In forming the thin film, in addition to the spray coating method, for example, a coating method such as a dipping (dip coating) method can be similarly applied. In order to form a titanium oxide thin film favorably, the surface of the substrate is preferably heated to 250 to 650 ° C. before being heated or cooled before the application of the coating liquid. Examples of the titanium alkoxide that can be used in the present invention include titanium tetraisopropoxide and titanium tetranormal butoxide.

The present invention can be similarly applied to not only a glass modified lens but also a synthetic resin modified lens. In the case of a synthetic resin variant lens, at the time of molding, immediately after molding, or before and after annealing, a coating solution prepared in the same manner as in the case of glass, preferably a coating solution containing titanium oxide fine particles, is spray-coated in the same manner. can do. Alternatively, the coating liquid may be applied to the inside of the mold in advance and then applied to a resin surface by pouring a high-temperature material, or titanium oxide fine particles may be added to the raw material for melting and molding.

Here, in the prepared coating solution, the preferable concentration of both titanium oxide fine particles and titanium alkoxide, which are the main components of the solute, is in the range of 1 to 50%. If it is less than 1%, a very large amount of liquid must be sprayed to obtain a preferable thickness in order to obtain a photocatalytic action, in which case the temperature of the substrate is lowered and the film strength is sufficient. It is not preferable because it does not become a problem. 50
%, The viscosity of the coating solution increases, causing problems such as clogging of the spray, and even if formed, the film becomes cloudy and the transmittance decreases, which is also undesirable. .

Here, if the alkoxide of silicon is further added to the above coating solution at a ratio of 40 wt% or less based on the amount of the solvent and mixed well, the light transmittance and the mechanical strength of the formed film are further enhanced. be able to. In addition, this addition also has the effect of increasing the surface area of the film, improving the resolution, and making the surface less likely to become dirty, making it easier to remove dirt. The silicon alkoxide can be added in the same manner when titanium oxide fine particles are used as the solute or when titanium alkoxide is used, and the same effect can be obtained. Examples of the silicon alkoxide that can be used in the present invention include silicon tetraethoxide (tetraethoxysilane), silicon tetraisopropoxide, and silicon tetranormal butoxide.

In the present invention, in order to further enhance the photocatalytic effect of titanium oxide, cerium oxide may be added to the coating solution. Cerium oxide functions to absorb ultraviolet rays more and enhance the photocatalytic effect of titanium oxide. However, the addition amount is preferably within 10 wt% with respect to titanium oxide, and when it exceeds 10 wt%,
It is not preferable because coloring of the film becomes conspicuous, the transmittance of visible light decreases, and the illuminance decreases.

Normally, ultraviolet light having a wavelength longer than about 300 nm is transmitted through glass. Therefore, in the case of a deformed lens for a headlamp made of glass, even if a photocatalyst substance is provided on the outer surface of the lens, the ultraviolet light emitted from the light source is titanium oxide. And the effect can be exerted, so that a photocatalytic effect is brought about. At this time, even if the amount of ultraviolet light emitted from the light source is very small, a sufficient photocatalytic effect is brought about for the decomposition of dirt. Furthermore, in the daytime when no light is received from the light source, sunlight containing a large amount of ultraviolet rays hits the lens, thereby obtaining a very large photocatalytic effect. As described above, since the photocatalytic function operates almost always during traveling, the lens surface is hardly stained.

On the other hand, when the headlight shaped lens is made of synthetic resin, the synthetic resin hardly transmits ultraviolet rays, and as described above, the ultraviolet rays emitted from the lamp do not directly irradiate the lens when used. Because
It is thought that sunlight is mainly used from the outside as a light source that provides a photocatalytic effect.

In the present invention, the preferable adhesion amount of titanium oxide is 5 to 3000 n in terms of the thickness of the thin film.
m. More preferably 100 to 2000 nm
Range. If the thickness is less than 5 nm, the function of the photocatalyst is too small, and the effect of the present invention cannot be sufficiently obtained.
When the distance exceeds m, the transmittance of light from the light source in the visible region decreases, and the illuminance decreases.

In the present invention, the thin film of titanium oxide can be easily formed on the surface of the deformed lens by the above-mentioned structure, so that the adhered dirt is disassembled and removed without requiring special cleaning. Can be maintained for a long time in a favorable state in terms of appearance and illuminance. Further, by forming the titanium oxide thin film on the surface, the mechanical strength and the chemical strength of the lens are improved, and the deterioration is suppressed.

Among the dirt on the headlight, those which can be satisfactorily decomposed and removed by the photocatalytic effect of the titanium oxide thin film according to the present invention include, for example, oil contained in exhaust gas, soot, insect body fluid, Alternatively, waxes and the like can be mentioned.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to embodiments.

<Example 1> Prior to forming a titanium oxide thin film, 2200 g of ethyl alcohol and 50 g of acetic acid were added to 500 g of titanium tetraisopropoxide.
The coating solution was prepared by stirring and mixing well for 5 hours. After leaving the obtained coating liquid as it was for 24 hours, the coating liquid was sprayed with a spray gun on the outer surface of the deformed glass lens after press molding and before annealing. At this time, the air pressure was adjusted to 3.0 kg / cm ² and the flow rate was adjusted to 150 g / min, and the spraying speed was 0.6 seconds per 10 cm ² . After that, annealing was performed according to a conventional method to obtain a 110 nm-thick, in-vehicle deformed lens of the present invention coated with a titanium oxide film having a photocatalytic effect.

In order to examine the effect of the photocatalyst on the obtained lens, a thinner red ink for a printer was applied to the surface of the coating film, and the light transmittance before and after irradiation with sunlight for 5 hours was measured. . Then, the magnitude of the photocatalytic effect was determined by increasing the transmittance. The result is shown in FIG. According to FIG.
The light transmittance after irradiation (dotted line) was larger than the light transmittance before irradiation (solid line) in the entire measurement wavelength range, and it was clear that a sufficient photocatalytic effect was working.

Example 2 Prior to the formation of a titanium oxide thin film, 2000 g of ethyl alcohol and 35 g of acetic acid were added to 500 g of titanium tetraisopropoxide.
After mixing well for 5 hours, the mixture was left as it was for 24 hours. Further, 100 g of acetylacetone was added, and finally, 2150 g of ethyl alcohol was added to adjust the concentration, thereby preparing a coating solution. And the air pressure is 3.5 kg / cm
² 、 Adjust the flow rate to 120g / min and spray speed 1
Spraying was carried out in the same manner as in Example 1 except that the time was set to 0.6 seconds per 0 cm ² . As a result, an in-vehicle deformed lens of the present invention having a 150 nm-thick photocatalytic titanium oxide coat was obtained. The transmittance of light was measured for the obtained modified lens in the same manner as in Example 1, and the magnitude of the photocatalytic effect was examined.

<Example 3> Prior to the formation of a titanium oxide thin film, 2300 g of ethyl alcohol and 50 g of acetic acid were added to 500 g of titanium tetraethoxide, mixed well for 5 hours, and then 50 g of cerium nitrate hexahydrate was added. The mixture was further stirred and mixed for 5 hours. Then, after allowing to stand for 24 hours, 100 g of acetylacetone was added, and 2,000 g of ethyl alcohol was further added to adjust the concentration to prepare a coating solution.

Then, spray coating was performed under the same conditions as in Example 1. As a result, an in-vehicle deformed lens of the present invention having a 120 nm-thick titanium oxide coat having a photocatalytic effect was obtained. The transmittance of light was measured for the obtained modified lens in the same manner as in Example 1, and the magnitude of the photocatalytic effect was examined.

Table 1 shows that the transmittance of the modified lenses of Examples 1 to 3 before and after irradiation with sunlight, that is, the transmittance before and after the dirt is decomposed by sunlight. The change is shown for the results measured for 500 nm light. As is clear from Table 1, the light transmittance after decomposition was increased by about 25 to 30% as compared with that before decomposition.

[0034]

[Table 1] <Example 4> Fine particles of titanium oxide having an average particle diameter of 12 nm were sprayed onto a mold for molding a synthetic resin, and then the compound in a molten state was poured into the mold. According to
An in-vehicle deformed lens having a thickness of 150 nm and coated with titanium oxide having a photocatalytic effect was obtained. The condition of spray coating of titanium oxide fine particles was air pressure 2.5 kg / c.
m ² , flow rate 170 g / min, spray speed 10 cm ²
Per second.

Example 5 Titanium oxide fine particles having an average particle diameter of 10 nm were added to a plastic hard coat solution for 30 watts.
Then, after dip coating, a polycarbonate resin irregular lens was immersed in the coating liquid and then pulled up at a speed of 25 cm / min to perform dip coating. After pulling, 2 at 75 ° C
After drying the solvent for 0 minutes, it was further heated at 120 ° C. for 30 minutes. As a result, an in-vehicle deformable lens having a 250 nm-thick titanium oxide coat having a photocatalytic effect was obtained.

[0036]

As described above, according to the present invention, a titanium oxide thin film having a photocatalytic effect is efficiently formed on the surface of a deformed lens. Thus, a lens for a vehicle headlamp that can be held in the vehicle can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing light transmittance curves before and after photolysis in Example 1 of the present invention.

Claims (7)

[Claims] 1. A headlight lens for a vehicle, wherein a thin film mainly composed of titanium oxide and having a photocatalytic function is formed on at least a part of the surface of the headlight lens. 2. The vehicle headlight lens according to claim 1, wherein said headlight lens is made of glass. 3. The vehicle headlight lens according to claim 1, wherein the headlight lens is made of a synthetic resin. 4. The headlight lens for a vehicle according to claim 1, wherein the thin film is mainly composed of fine particle titanium oxide. 5. The method according to claim 1, wherein the thin film is mainly composed of titanium oxide generated by thermal decomposition of an alkoxide of titanium on the surface of the headlight lens. Headlight lens for vehicles. 6. The vehicle according to claim 1, wherein the photocatalytic function is realized by at least one of light emitted from a light source and sunlight. Headlight lens. 7. The method according to claim 1, wherein said thin film has a thickness of 5 to 3000 nm.
7. The vehicle headlight lens according to 3, 4, 5, or 6.