WO2016147573A1

WO2016147573A1 - Hydrophilic lens

Info

Publication number: WO2016147573A1
Application number: PCT/JP2016/000995
Authority: WO
Inventors: 千春前田; 小林　信幸; 亨難波; 晃暢宮崎
Original assignee: パナソニックＩｐマネジメント株式会社
Priority date: 2015-03-19
Filing date: 2016-02-25
Publication date: 2016-09-22
Also published as: JP2018077260A

Abstract

Provided is a hydrophilic lens in which a hydrophilic layer formed by dispersing fine particles having photocatalytic activity in a network of a silicate material is formed on the surface of a glass base, wherein a hydrophilic coating having a low reflectance and simultaneously having a high hydrophilicity and a high hardness is formed on the surface thereof. The fine particles of the photocatalyst have an average particle size of 30 nm or less. The hydrophilic layer is controlled so that the thickness thereof is 10-30 nm and the surface thereof has an arithmetic mean roughness within the range of 0.7-1.9 nm.

Description

Hydrophilic lens

The technology disclosed here relates to a hydrophilic lens for a photographing device such as a camera and a video mainly used outdoors.

In recent years, cameras for monitoring rear view and side view have been installed outside the car so that parking can be performed more safely and securely (Fig. 1). Moreover, many surveillance cameras are installed not only in urban areas but also in private houses as a security measure.

¡Shooting devices such as cameras and video are installed outdoors, so they are exposed to wind and rain and exhaust gas, and raindrops and dirt adhere to the lens. In order to remove raindrops and dirt adhering to the lens, a hydrophilic lens in which a hydrophilic coat is formed on a glass substrate of the lens is known. The hydrophilic coat contains a photocatalyst that exhibits hydrophilicity upon exposure to ultraviolet rays, and imparts a self-cleaning action to the lens.

Patent Document 1 describes a technique for forming a hydrophilic antifogging layer by sputtering titanium oxide on the surface of a glass substrate in order to impart antifogging properties to the inner surface side of a watch cover glass. In order to reduce the luminous reflectance, the thickness of the antifogging layer is set to 5 nm or less. Further, an antireflection layer of an inorganic multilayer film in which high refractive index layers and low refractive index layers are alternately laminated is formed on the inner surface of the cover glass, and an antifogging layer is formed thereon.

Patent Document 2 describes a technique for forming a surface layer containing a photocatalyst such as titania and a compound such as silica capable of adsorbing a hydroxyl group on the surface of a substrate such as a tile. In order to obtain a physical contact angle reduction effect, the surface roughness (Ra) is set to 0.15 to 1 μm.

Patent Document 3 describes a pattern forming body having a photocatalyst-containing layer on a substrate containing a substance whose wettability is changed by the action of a photocatalyst by exposure of the pattern. Anatase-type titanium oxide or the like is used as the photocatalyst, and the photocatalytic reaction occurs efficiently.

JP 2011-149712 A Japanese Patent Laid-Open No. 10-237416 JP 2002-274077 A

A coating using a silicate composition (FIG. 2) in which fine particles 4 having photocatalytic activity such as titanium oxide are dispersed in a network 3 of a silicate material is generally known. Such a coat is also applied as a hydrophilic coat formed on the surface of the lens glass substrate in order to remove raindrops and dirt adhering to the lens.

The fine particles 4 having photocatalytic activity dispersed in the hydrophilic coat are photocatalysts that exhibit a catalytic action when irradiated with light. Titanium oxide is often used as the photocatalyst. Titanium oxide generates OH radicals on the surface by absorbing ultraviolet rays. Reaction of moisture in the air with the generated OH radicals generates OH groups on the surface. Super-hydrophilicity can be imparted to the surface of the hydrophilic coat by OH groups generated by light irradiation. Thereby, the hydrophilic coat exhibits a self-cleaning action.

On the other hand, since photocatalysts such as titanium oxide are essentially high refractive materials, the reflectance of the hydrophilic coat is increased. When the reflectance is high, a ghost is generated due to the reflection of incident light on the lens surface, and visibility is deteriorated. If the content of the photocatalyst in the hydrophilic coat is decreased in order to reduce the reflectance, the effect of imparting hydrophilicity is reduced and superhydrophilicity cannot be obtained.

The overall reflectance can be reduced by forming a multilayer antireflection layer in which a high refractive index layer and a low refractive index layer are alternately formed on a lens substrate, and forming a hydrophilic coat thereon. it can. However, if the reflectance of the outermost hydrophilic coat is too high, the overall reflectance cannot be sufficiently reduced. Therefore, even when the antireflection layer is formed, it is necessary to reduce the reflectance of the hydrophilic coat itself.

Cameras installed outdoors and video-taking equipment such as video, in particular, the cameras (rear view camera 1 and side view camera 2 shown in FIG. 1) that can monitor the rear view and side view mounted outside the automobile are traveling. Scratches are likely to occur due to rubbing of dust inside. If the hydrophilic coat is scratched and the surface becomes rough, the hydrophilicity decreases and the visibility deteriorates. In order to prevent the hydrophilic coat from being scratched, it is effective to increase the hardness of the hydrophilic coat.

For example, the commercial product A has high hydrophilicity but low hardness and good visibility at the beginning of use, but there is a problem that the hydrophilicity decreases due to scratches. On the other hand, when the hardness is increased in order to improve the durability like the commercial product B, there is a problem that the hydrophilicity is lowered. In addition, regarding the commercial product C that balances hydrophilicity and durability, both hydrophilicity and durability are not satisfactory levels (FIG. 3).

As described above, since the conventional technique cannot provide high hydrophilicity and high durability at the same time, it is necessary to develop a hydrophilic coat having high hydrophilicity and high durability at the same time.

That is, there is a strong demand for a hydrophilic coat having low reflectivity and having both high hydrophilicity and high durability.

In a hydrophilic lens in which a hydrophilic layer (hydrophilic coat) formed by dispersing fine particles 4 having photocatalytic activity in a network 3 of a silicate material is formed on the surface of a glass substrate, reflection is performed by controlling the thickness of the hydrophilic layer. It has been found that the rate can be reduced. Furthermore, it has been found that the hydrophilicity and hardness can be simultaneously increased by simultaneously controlling the average particle diameter of the fine particles 4 having photocatalytic activity dispersed in the hydrophilic layer, and the film thickness and surface roughness of the hydrophilic layer.

A silicate material for a hydrophilic coat according to the technique disclosed herein is a composition having a three-dimensional network structure including a bond (siloxane bond) of silicon (Si) and oxygen (O), and includes methyl silicate, ethyl silicate, methyl Illustrative are silicate polymers such as ethyl silicate. In general, after silanol is formed by hydrolyzing a silicate material, silanol is heated and subjected to dehydration condensation polymerization to form a coating having a three-dimensional network structure including siloxane bonds.

The fine particles 4 having photocatalytic activity dispersed in the hydrophilic coat by the technique disclosed herein are exemplified by fine particles such as titanium oxide.

The technology disclosed herein provides a hydrophilic lens having a glass substrate and a hydrophilic layer formed on the glass substrate. The hydrophilic layer includes a silicate material in which fine particles 4 having photocatalytic activity are dispersed. The film thickness of the hydrophilic layer is 30 nm or less, and the average particle size of the fine particles having photocatalytic activity is 30 nm or less. Alternatively, the hydrophilic layer may be formed to have a film thickness of 10 to 30 nm and an arithmetic average roughness Ra of the surface of 0.7 to 1.9 nm.

According to the technique disclosed herein, the film thickness of the hydrophilic layer is reduced to 30 nm or less, preferably 10 to 30 nm, whereby the reflectance can be reduced to the same level as the reflectance of the glass substrate itself. it can. If an antireflection layer is formed on a glass substrate and the hydrophilic layer is formed thereon, a reflectance sufficiently lower than the reflectance of the glass substrate itself can be achieved.

Further, by controlling the average particle diameter of the photocatalyst fine particles to 30 nm or less, the film thickness of the hydrophilic layer to 10 to 30 nm, and the arithmetic average roughness Ra of the surface to 0.7 to 1.9 nm. The hydrophilicity and hardness of the hydrophilic layer can be compatible at a high level.

According to the technology disclosed herein, it is possible to provide a hydrophilic lens having low reflectivity and having both high hydrophilicity and high hardness at the same time.

FIG. 1 is a diagram showing an automobile provided with a vehicle-mounted rear view and side view camera. FIG. 2 is a schematic diagram showing the structure of a silicate resin composition for hydrophilic coating in which fine particles having photocatalytic activity are dispersed in a network of silicate materials. FIG. 3 is a conceptual diagram comparing a commercial product and a developed product with respect to hydrophilicity and durability. FIG. 4 is a schematic diagram for explaining the contact angle. FIG. 5 is a schematic cross-sectional view of a hydrophilic lens in which a hydrophilic layer is directly formed on a glass substrate. FIG. 6 is a schematic cross-sectional view of a hydrophilic lens in which a hydrophilic layer is formed on an antireflection layer formed on a glass substrate. FIG. 7 is a diagram showing the relationship between the thickness of the hydrophilic layer and the reflectance. FIG. 8 is a diagram showing the relationship between the thickness of the hydrophilic layer and the reflectance. FIG. 9A is a diagram showing a photograph taken by a camera equipped with a lens having a low reflectance on the surface. FIG. 9B is a diagram showing a photograph taken with a camera equipped with a lens having a high reflectance on the surface. FIG. 10A is a view showing a photograph taken with mist droplets attached to the lens surface after the hydrophilic coating treatment. FIG. 10B is a view showing a photograph taken with mist droplets attached to the lens surface before the hydrophilic coating treatment. FIG. 11A is a diagram illustrating a photomicrograph of the surface after a rubbing test of a hydrophilic lens according to an example of the present disclosure. FIG. 11B is a diagram showing a photomicrograph of the surface after the rubbing test of the hydrophilic lens shown in the comparative example.

[Preparation of silicate resin composition for hydrophilic coating]
Preparation Example 1
Water and methanol are added as solvents to methyl silicate, titanium oxide sol having an average particle diameter of 4 nm, and an organometallic compound as a silicate curing catalyst to obtain a silicate composition A for hydrophilic coating.

Methyl silicate and titanium oxide sol are based on the total weight of silica equivalent weight (weight when converted to silica) and titanium oxide equivalent weight (weight when converted to titanium oxide) after hydrolysis / dehydration condensation polymerization reaction. It is added so that the titanium oxide equivalent weight is 60 to 80%. At that time, the concentration is adjusted so that the solid content concentration in the solution is 1.0 to 10.0% by weight.

The prepared hydrophilic silicate composition A is spin-coated on a glass disc having a diameter of 30.0 mm at 2000 to 5000 rpm, and further baked at 300 ° C., thereby forming a desired hydrophilic layer. .

Preparation Example 2
Water and methanol are added as solvents to methyl silicate, titanium oxide sol having an average particle diameter of 30 nm, and an organometallic compound as a silicate curing catalyst to obtain silicate composition B for hydrophilic coating.

The methyl silicate and titanium oxide sol are added so that the titanium oxide equivalent weight is 60 to 80% with respect to the total weight of the silica equivalent weight and the titanium oxide equivalent weight after the hydrolysis / dehydration condensation polymerization reaction. At that time, the concentration is adjusted so that the solid content concentration in the solution is 1.0 to 10.0% by weight.

Then, the prepared hydrophilic coating silicate composition B is spin-coated on a glass disc having a diameter of 30.0 mm at 2000 to 5000 rpm, and further baked at 300 ° C. to form a desired hydrophilic layer. .

Preparation Example 3
Water and methanol are added as solvents to methyl silicate, titanium oxide sol having an average particle size of 43 nm, and an organometallic compound as a silicate curing catalyst to obtain silicate composition C for hydrophilic coating.

Methyl silicate and titanium oxide sol are added so that the titanium oxide equivalent weight is 60% with respect to the total weight of the silica equivalent weight and the titanium oxide equivalent weight after the hydrolysis / dehydration condensation polymerization reaction. At that time, the solid content concentration in the solution is adjusted to 10.0% by weight.

Then, the prepared silicate composition C for hydrophilic coating was spin-coated on a glass disk having a diameter of 30.0 mm at 2000 to 5000 rpm, and further baked at 300 ° C. to form a desired hydrophilic layer.

Although the above three examples are given as preparation examples, a silicate composition for hydrophilic coating may be obtained using zinc oxide sol, tin oxide sol, or tungsten oxide sol instead of titanium oxide sol. Moreover, you may obtain the silicate type composition for hydrophilic coatings using what mixed 2 or more of titanium oxide sol, zinc oxide sol, tin oxide sol, and tungsten oxide sol instead of titanium oxide sol.

That is, as the fine particles 4 having photocatalytic activity, zinc oxide, tin oxide, tungsten oxide or the like may be used instead of titanium oxide, and plural kinds of fine particles may be present in the hydrophilic layer.

Next, the results of measuring the properties of the hydrophilic layer (hydrophilic coat) formed using the composition obtained in the Preparation Example are shown.

[Measuring means]
1. Film thickness measurement (1) Spectral ellipsometer The thickness of the hydrophilic layer is measured using a spectroscopic ellipsometer (UVISEL: manufactured by Horiba, Ltd.). Using a Xe lamp, light in the spectral range of 210 to 880 nm is incident on the hydrophilic layer to be measured, and the change in polarization of incident light and reflected light is measured to determine the film thickness.

(2) Step meter The thickness of the hydrophilic layer is measured using a step meter (DEKTAK 6M STYLUS PROFILER: manufactured by Veeco). The film thickness is obtained by measuring the level difference between the hydrophilic layer to be measured and the substrate using a stylus.

2. Particle size measurement (1) Particle size distribution meter The particle size distribution of the photocatalyst fine particles 4 is measured using a particle size distribution meter (Nanotrac wave UT151: manufactured by Microtrac).

(2) Electron Microscope The photocatalyst fine particles 4 to be measured are imaged using an electron microscope (S-4800 Scanning Electron Microscope: manufactured by Hitachi High-Technologies Corporation), and the obtained image is image-processed to calculate the particle size.

3. Surface Roughness Measurement Using a surface roughness meter (New View 6K: manufactured by ZYGO), the roughness curve of the surface of the hydrophilic layer to be measured is recorded, and its arithmetic average roughness Ra is measured.

4). Reflectance The reflectance of the hydrophilic layer is measured using a reflectometer (USPM-RU III: manufactured by Olympus Corporation). The reflectance is obtained by irradiating light having a wavelength of 550 nm.

In the technique disclosed herein, the reflectance is preferably 10% or less.

5. Contact angle measurement The hydrophilicity of the hydrophilic layer surface is evaluated by a static contact angle θ formed by water droplets on the surface of the hydrophilic layer to be measured, using an automatic contact angle meter (MD300, manufactured by Kyowa Interface Chemical Co., Ltd.). The contact angle θ means an angle formed between a sample surface and a tangent line where a water droplet contacts the sample surface (FIG. 4). In the figure, γ _S means the surface tension of the hydrophilic layer, γ _L means the surface tension of water, and γ _SL means the interfacial tension of the hydrophilic layer and water.

In the technique disclosed herein, a sample is defined as being hydrophilic if the contact angle θ is 30 ° or less, and super-hydrophilic if it is 10 ° or less. Practically, it is preferably 5 ° or less.

6). Hardness measurement The durability of the hydrophilic layer surface is evaluated by the pencil hardness determined by the pencil hardness test method (JIS K5600-5-4). The pencil hardness means the hardest pencil density at which the surface is scratched with a lead having a different pencil density and no flaw is generated. The pencil density is 6B, 5B, 4B, 3B, 2B, B, HB, F, H, 2H, 3H, 4H, 5H, 6H from the soft side to the hard side. Expose the pencil core 5-6 mm, and flatten the tip with abrasive paper so that it is cylindrical. The measurement object is set so that the surface is horizontal, the angle of the pencil is 45 ± 1 ° with respect to the surface, and a load of 750 ± 10 g is applied for measurement.

In the technology disclosed herein, it is preferable that the pencil hardness is 5H or more in order to show practically sufficient durability.

7). Scratch resistance measurement The durability of the hydrophilic layer surface is also evaluated by the scratch resistance observed in the rubbing test. A 500 g load is applied to a palm (palm fiber) scourer and the surface of the hydrophilic layer is rubbed 100 times, and then the generation of scratches is observed with a microscope.

Hereinafter, the technology disclosed herein will be described based on examples and comparative examples, but these examples are illustrative and do not limit the technology disclosed herein.

1. Effect of film thickness on the reflectance of the hydrophilic layer The silicate composition A was directly applied on the glass substrate 110 to form the hydrophilic layer 120 with various film thicknesses (FIG. 5). Further, an antireflection layer (AR layer) 230 in which a high refractive index (TaO ₅ ) layer and a low refractive index layer (SiO ₂ ) are alternately laminated is first formed on the glass substrate 210, and a silicate composition is formed thereon. Object A was applied to form hydrophilic layer 220 with various film thicknesses (FIG. 6). The film thickness of less than 30 nm was measured by spectroscopic ellipsometry, and the film thickness of 30 nm or more was measured by a step gauge.

The arithmetic average roughness Ra, the contact angle of water droplets and the reflectance were measured on the surface of each hydrophilic layer. The measurement results are shown in Table 1.

In the case of the hydrophilic lens 100 in which the hydrophilic layer 120 is directly formed on the glass substrate 110, when the thickness of the hydrophilic layer 120 is reduced to 30 nm or less, it is reflected to the same degree as the reflectance (4%) of the glass substrate 110 itself. The rate could be reduced (FIG. 7).

Furthermore, in the case of the hydrophilic lens 200 in which the antireflection layer 230 is formed on the glass substrate 210 and the hydrophilic layer 220 is formed thereon, when the thickness of the hydrophilic layer 220 is reduced to 30 nm or less, the glass substrate 210 itself It was possible to achieve a reflectance lower than that of 4% (FIG. 8).

If the thickness of the hydrophilic layer is 30 nm or less, the reflectance with respect to incident light with a wavelength of 550 nm is low, and when photographing through a lens, the incident light is reflected on the lens surface and a ghost like a ring of light does not occur (see FIG. 9A). Thereby, sufficiently good visibility can be obtained. However, when the thickness of the hydrophilic layer was 70 nm, the reflectance could not be sufficiently reduced even by the antireflection layer 230, and ghost was generated (FIG. 9B).

After the hydrophilic coat treatment for forming a hydrophilic layer using the composition A (FIG. 10A) and before the treatment (FIG. 10B), water was sprayed on the lens surface with a spray to confirm the state of mist droplet adhesion.

The lens after the hydrophilic coating treatment was less affected by the adhering mist and had good visibility. On the other hand, the visibility of the lens before the hydrophilic coating treatment was greatly deteriorated due to adhesion of mist droplets.

2. Influence of particle diameter of photocatalyst fine particles 4 and surface roughness of hydrophilic layer on hydrophilicity and hardness of hydrophilic layer First, a high refractive index (TaO ₅ ) layer and a low refractive index layer (SiO ₂ ) are alternately laminated on a glass substrate. The antireflection layer (AR layer) thus formed was formed, and silicate-based compositions A, B, and C were applied thereon to form hydrophilic layers with various film thicknesses. The film thickness of less than 30 nm was measured by spectroscopic ellipsometry, and the film thickness of 30 nm or more was measured by a step gauge.

The arithmetic average roughness Ra, pencil hardness, and contact angle of water droplets before and after the rubbing test were measured on the surface of each hydrophilic layer. The measurement results are shown in Table 2.

From the measurement results shown in Table 2, the average particle size of the fine particles is 30 nm or less, the thickness of the hydrophilic layer is 10 to 30 nm, and the arithmetic average surface roughness Ra of the hydrophilic layer surface is 0.7 to When the thickness is 1.7 nm, it can be seen that the hydrophilic layer exhibits a high pencil hardness (5H or more) and a low contact angle (30 ° or less) even after the rubbing test. After the rubbing test, there were no scratches on the surfaces of the hydrophilic layers of Examples 3 to 5 (FIG. 11A), and scratches were confirmed on the surfaces of the hydrophilic layers of Comparative Examples 3 and 4 (FIG. 11B).

The hydrophilic lens of the technology disclosed herein has low reflectance, and has high hydrophilicity and high hardness at the same time, so it is mounted on the outside of an automobile such as a camera and video, particularly an automobile. This is useful for cameras that monitor rear view and side view.

DESCRIPTION OF SYMBOLS 1 Rear view camera 2 Side view camera 3 Network of silicate material 4 Photocatalyst microparticle 100 Hydrophilic lens 110 Glass base material 120 Hydrophilic layer 200 Hydrophilic lens 210 Glass base material 220 Hydrophilic layer 230 Antireflection layer

Claims

A hydrophilic lens comprising a glass substrate and a hydrophilic layer formed on the surface of the glass substrate, wherein the hydrophilic layer includes a silicate material in which fine particles having photocatalytic activity are dispersed, and the thickness of the hydrophilic layer is 30 nm. A hydrophilic lens, wherein the average particle size of the fine particles is 30 nm or less, and the arithmetic average roughness of the surface of the hydrophilic layer is 0.7 to 1.9 nm.
The hydrophilic lens according to claim 1, wherein the hydrophilic layer has a thickness of 10 to 30 nm.
The hydrophilic lens according to claim 1 or 2, wherein the fine particles contain titanium oxide.
The hydrophilic lens according to any one of claims 1 to 3, wherein an antireflection layer is further formed between the glass substrate and the hydrophilic layer.