JP2022078385A - Optical member and method for manufacturing the same - Google Patents

Abstract

To provide an optical member having a functional film having photocatalytic activity and low reflectance.SOLUTION: An optical member 1 includes a translucent member 2 and a functional film 3 for covering the translucent member 2. The functional film 3 includes photocatalyst particles activated by ultraviolet rays and a binder layer 5 for covering the translucent member 2. At least part of the photocatalyst particles constitutes photocatalyst secondary particles 4. At least part of the photocatalyst secondary particles 4 is partially buried in the binder layer 5. A thickness of the functional film 3 is greater than or equal to 15 nm and less than or equal to 200 nm.SELECTED DRAWING: Figure 1

Description

The present invention relates to an optical member and a method for manufacturing the same.

The method for producing a photocatalytic functional material described in Patent Document 1 includes a step of preparing a sputtering target for forming a photocatalyst film formed by press-molding a raw material containing a photocatalyst powder at a temperature at which the photocatalytic action does not deteriorate, and sputtering for forming a photocatalyst film. It includes a step of forming a photocatalytic film on the substrate by a sputtering method at a temperature at which the substrate having low heat resistance is not deformed by using a target.

Japanese Unexamined Patent Publication No. 2015-11524

However, when the optical member is manufactured by the manufacturing method described in Patent Document 1, the reflectance tends to be relatively high.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an optical member having a functional film having photocatalytic activity and having a low reflectance.

An exemplary optical member of the present invention includes a translucent member and a functional film that covers the translucent member. The functional film includes photocatalytic particles activated by ultraviolet rays and a binder layer covering the translucent member. At least a part of the photocatalytic particles constitutes photocatalytic secondary particles. At least a part of the photocatalytic secondary particles is partially buried in the binder layer. The thickness of the functional film is 15 nm or more and 200 nm or less.

In the method for producing an exemplary optical member of the present invention, a functional film is formed by applying a coating liquid containing photocatalytic particles activated by ultraviolet rays and a binder raw material to the surface of the translucent member by a wet process. It has a coating process. The functional film includes a binder layer covering the translucent member and the photocatalytic particles. At least a part of the photocatalytic particles constitutes photocatalytic secondary particles. At least a part of the photocatalytic secondary particles is partially buried in the binder layer. The thickness of the functional film is 15 nm or more and 200 nm or less.

An exemplary invention can provide an optical member comprising a functional film having photocatalytic activity and having a low reflectance.

FIG. 1 is a schematic view of an example of an optical member according to the first embodiment of the present invention. FIG. 2 is a schematic view of a modification 1 of the optical member of FIG. FIG. 3 is a schematic view of a modification 2 of the optical member of FIG. FIG. 4 is a graph showing the relationship between the integrated strength of the titanium atoms of the optical members (A-1) to (A-6) manufactured in the examples and the thickness of the functional film. FIG. 5 is a graph showing the results of accelerated deterioration tests of the optical members (B-1) to (B-3) manufactured in the examples. FIG. 6 is a graph showing the results of accelerated deterioration tests of the optical members (B-4) to (B-6) manufactured in the examples. FIG. 7 is a graph showing the results of the wiping test of the optical members (B-1) to (B-3) manufactured in the examples. FIG. 8 is a graph showing the results of the wiping test of the optical members (B-4) to (B-6) manufactured in the examples. FIG. 9 is a graph showing the spectral reflectances of the optical members (C-1) to (C-4) manufactured in the examples. FIG. 10 is a graph showing the spectral reflectances of the optical members (D-1) to (D-2) manufactured in the examples.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the figure, the same or corresponding parts are designated by the same reference numerals and the description is not repeated.

In the present specification, the "average particle size" of particles, fine particles or aggregates is determined by observing with a scanning electron microscope (SEM). Specifically, from the measurement targets (particles, fine particles or aggregates) observed by the SEM image, any 50 measurement targets whose entire image can be confirmed are selected. For each measurement target, the maximum diameter and the minimum diameter are measured respectively, and the average value is used as the particle size of each measurement target. Then, the average value of the particle size of each of the 50 measurement targets is defined as the "average particle size". The maximum diameter is the length of the longest line segment among the line segments that pass through the geometric center of the measurement target and whose ends are located at the outer edges of the measurement target. The minimum diameter is the length of the shortest line segment among the line segments that pass through the geometric center of the measurement target and whose ends are located at the outer edges of the measurement target.

As used herein, "thickness" means average thickness. The "thickness" is measured by a contact type film thickness measuring device (for example, "DekTakXT-S" manufactured by Bruker).

<First Embodiment: Optical member>
The optical member according to the first embodiment of the present invention includes a translucent member and a functional film that covers the translucent member. The functional film includes photocatalytic particles activated by ultraviolet rays and a binder layer covering a translucent member. At least a part of the photocatalytic particles constitutes photocatalytic secondary particles. At least a part of the photocatalytic secondary particles is partially buried in the binder layer. The thickness of the functional film is 15 nm or more and 200 nm or less. Hereinafter, the photocatalytic particles activated by ultraviolet rays may be simply referred to as "photocatalytic particles".

Since the functional film contains photocatalytic particles, it has excellent photocatalytic activity. Specifically, the functional membrane has high hydrophilicity. That is, the functional film has high wettability to water. Therefore, when water droplets adhere to the functional film, a film of water having a substantially uniform thickness is formed on the surface of the functional film. Further, even when the hydrophilicity of the functional film decreases with use, the hydrophilicity is restored by irradiation with ultraviolet rays.

Since the optical member according to the first embodiment has a functional film, it is suitable as an optical member used in an environment where water adheres. The optical member according to the first embodiment is suitable as, for example, an optical member used outdoors. Specifically, the optical member according to the first embodiment is suitable as a lens of an in-vehicle camera for monitoring the surroundings of a vehicle.

The optical member according to the first embodiment includes a functional film having photocatalytic activity and has a low reflectance. The reason is as follows. In general applications (eg, paints for walls or windows), the thicker the functional film, the better the photocatalytic activity, so there is a tendency to form a relatively thick functional film. However, in the optical member, if the functional film is too thick, the reflectance is lowered, which causes an image defect (for example, a ghost image or flare). The present inventor has discovered that by reducing the thickness of the functional film to 15 nm or more and 200 nm or less, the functional film can exhibit sufficient photocatalytic activity and suppress the reflectance of the optical member. The present invention is an invention based on the above findings. That is, in the optical member according to the first embodiment, since the thickness of the functional film is 15 nm or more and 200 nm or less, the functional film exhibits sufficient photocatalytic activity and has low reflectance.

The functional film also includes a binder layer. The binder layer covers the translucent member. At least a part of the photocatalytic particles constitutes photocatalytic secondary particles. Then, at least a part of the photocatalytic secondary particles is partially buried in the binder layer. In the optical member according to the first embodiment, since the photocatalyst secondary particles are partially embedded in the binder layer, the photocatalyst secondary particles are difficult to be detached, and the wear resistance of the functional film is excellent. Further, the optical member according to the first embodiment has a function because not all the photocatalytic secondary particles are completely buried in the binder layer (that is, at least a part of the photocatalytic secondary particles are exposed from the binder layer). The photocatalytic activity of the film is excellent.

Hereinafter, the optical member 1 according to the first embodiment will be described with reference to FIG. 1. FIG. 1 is a schematic view of the optical member 1 according to the first embodiment. The optical member 1 includes a translucent member 2 and a functional film 3 that covers the translucent member 2. The functional film 3 includes photocatalytic particles and a binder layer 5. At least a part of the photocatalyst particles constitutes the photocatalyst secondary particles 4. At least a part of the photocatalytic secondary particles 4 is partially buried in the binder layer 5. Specifically, in the vicinity of the lower layer of the functional film 3, the photocatalytic secondary particles 4 are partially or completely buried in the binder layer 5. Hereinafter, the photocatalytic secondary particles 4 partially or completely buried in the binder layer 5 may be referred to as “buried particles”. The photocatalytic secondary particles 4 partially buried in the binder layer 5 are partially exposed from the binder layer 5. In the vicinity of the surface layer of the functional film 3, the photocatalytic secondary particles 4 are deposited on the buried particles. The photocatalytic secondary particles 4 deposited on the buried particles are completely exposed from the binder layer 5.

[Translucent member]
As shown in FIG. 1, the translucent member 2 is composed of a single member. However, as shown in Modification 1 described later, the translucent member of the optical member according to the first embodiment may be composed of a plurality of members. The translucent member 2 has translucency. That is, the translucent member 2 transmits light. The translucent member 2 may be transparent or translucent. The translucent member 2 contains, for example, glass or resin.

The shape of the translucent member 2 is, for example, a lens shape. When the shape of the translucent member 2 is lenticular, the radius of curvature of the lens surface of the translucent member 2 is preferably 10 mm or more and 15 mm or less. When the radius of curvature of the translucent member 2 is less than 10 mm, the thickness of the functional film 3 tends to vary greatly between the central portion of the translucent member 2 and the outer edge portion of the translucent member 2. When the radius of curvature of the translucent member 2 exceeds 15 mm, it tends to be difficult to impart a desired angle of view to the optical member 1.

[Functional membrane]
The functional film 3 has photocatalytic activity. Specifically, the functional membrane 3 has hydrophilicity. The static contact angle of the surface of the functional film 3 with respect to pure water is preferably 30.0 degrees or less, more preferably 20.0 degrees or less, still more preferably 10.0 degrees or less. Hereinafter, the static contact angle with respect to pure water may be simply referred to as "contact angle". Here, the contact angle of the functional film 3 is a value measured in an environment where the temperature is 23 ° C. ± 3 ° C. and the relative humidity is 50% ± 3% after the functional film 3 is sufficiently irradiated with ultraviolet rays. The irradiation conditions of ultraviolet rays are, for example, a wavelength of 352 nm, an irradiation time of 96 hours, and an irradiance of 1 mW / cm ² .

The functional film 3 covers at least a part of the surface of the translucent member 2. The functional film 3 preferably covers the entire surface of the translucent member 2 that is not covered by other members.

The thickness of the functional film 3 is 15 nm or more and 200 nm or less as described above. The thickness of the functional film 3 is preferably 20 nm or more and 180 nm or less, and more preferably 30 nm or more and 160 nm or less. The thickness of the functional film 3 is particularly preferably 40 nm or more. By setting the thickness of the functional film 3 to 15 nm or more, the functional film 3 exhibits sufficient photocatalytic activity. By setting the thickness of the functional film 3 to 200 nm or less, the reflectance of the optical member 1 can be reduced.

(Photocatalytic particles)
The photocatalyst particles are primary particles containing a photocatalyst. At least a part of the photocatalyst particles constitutes the photocatalyst secondary particles 4. At least a part of the photocatalytic particles may be contained in the functional film 3 in the state of primary particles. As long as the photocatalyst particles contain the photocatalyst, the photocatalyst particles may further contain components other than the photocatalyst. Examples of the component other than the photocatalyst include a component having an electron-capturing effect. Examples of the substance having an electron-supplementing effect include gold, silver, copper, platinum, palladium, iron, nickel, cobalt, zinc and copper oxide. The content ratio of the photocatalyst in the photocatalyst particles is preferably 90% by mass or more, more preferably 99% by mass or more, still more preferably 100% by mass.

Examples of the photocatalyst contained in the photocatalyst particles include titanium oxide, strontium titanate, zinc oxide, silicon carbide, gallium phosphate, cadmium sulfide, cadmium selenide and molybdenum trisulfide. The photocatalytic particles preferably contain titanium oxide. When the photocatalytic particles contain titanium oxide, the photocatalytic activity of the functional film 3 is further improved.

Examples of titanium oxide include anatase-type titanium oxide, rutile-type titanium oxide, and brookite-type titanium oxide. As the titanium oxide, anatase-type titanium oxide is preferable from the viewpoint of photocatalytic activity.

When the photocatalyst particles contain titanium oxide, it is preferable that the optical member 1 has an integrated intensity of titanium atoms measured by fluorescent X-rays of 600 or more and 35,000 or less. The integrated strength of the titanium atom is more preferably 4,000 or more and 30,000 or less, and further preferably 8,000 or more and 30,000 or less. The integrated strength of titanium atoms is roughly proportional to the thickness of the functional film 3 and the content ratio of titanium oxide in the functional film 3. That is, the thicker the functional film 3, the higher the integrated strength of the titanium atom. Further, the higher the content ratio of titanium oxide in the functional film 3, the higher the integrated strength of titanium atoms. In the optical member 1 in which the integrated strength of titanium atoms is in the range of 600 or more and 35,000 or less, the thickness of the functional film 3 and the content ratio of titanium oxide in the functional film 3 are appropriate. As a result, the optical member 1 is more balanced between the high photocatalytic activity of the functional film 3 and the low reflectance.

From the viewpoint of improving the photocatalytic activity of the functional film 3, it is preferable that a part of the photocatalytic secondary particles 4 is partially or completely exposed on the surface of the functional film 3. Specifically, the ratio of particles partially or completely exposed on the surface of the functional film 3 (hereinafter, may be referred to as exposed particles) among all the photocatalytic secondary particles 4 is 1% or more. Is preferable, 5% or more is more preferable, and 10% or more is further preferable. The ratio of exposed particles is calculated from the ratio of the number of exposed particles among any 100 photocatalytic secondary particles 4 by observing the cross section of the functional film 3 with an electron microscope.

The occupied area ratio of the photocatalytic particles in the plan view of the functional film 3 is preferably 5% or more and 100% or less, and more preferably 10% or more and 80% or less. By setting the occupied area ratio of the photocatalytic particles to 5% or more, the photocatalytic activity of the functional film 3 can be further improved. By setting the occupied area ratio of the photocatalyst particles to 80% or less, the reflectance of the optical member 1 can be further improved. The occupied area ratio of the photocatalyst particles is measured by observing a range of 6 μm × 4 μm on the surface of the functional film 3 by SEM.

The average particle size of the primary particles of the photocatalyst particles is preferably 1 nm or more and 20 nm or less, and more preferably 5 nm or more and 18 nm or less. When the average particle size of the primary particles of the photocatalyst particles is 1 nm or more and 20 nm or less, the translucency of the optical member 1 is improved.

The average particle size of the photocatalyst secondary particles 4 is preferably 10 nm or more and 90 nm or less, and more preferably 10 nm or more and 50 nm or less. When the average particle size of the photocatalyst secondary particles 4 is 10 nm or more, the photocatalyst secondary particles 4 are easily exposed from the binder layer 5. As a result, the photocatalytic activity of the functional film 3 is further improved. When the average particle size of the photocatalyst secondary particles 4 is 90 nm or less, the translucency of the functional film 3 is improved.

The photocatalytic secondary particles 4 may form aggregates. As described above, since the photocatalyst secondary particles 4 form an aggregate, the photocatalyst secondary particles 4 are easily exposed on the surface of the functional film 3. As a result, the photocatalytic activity of the functional film 3 is further improved. Further, since the photocatalyst secondary particles 4 form an aggregate, the translucency of the functional film 3 is improved. The average particle size of the aggregate is preferably 15 nm or more and 200 nm or less, and more preferably 60 nm or more and 150 nm or less. When the average particle size of the agglomerates is 20 nm or more, the photocatalytic secondary particles 4 are more easily exposed on the surface of the functional film 3. When the average particle size of the aggregate is 200 nm or less, the translucency of the functional film 3 is further improved. The plurality of aggregates may be in contact with each other in the binder layer 5. As described above, the plurality of aggregates are in contact with each other in the binder layer 5, so that the battery structure is formed and the photocatalytic activity of the functional film 3 is improved.

The maximum reflectance for incident light having a wavelength of 450 nm or more and 780 nm or less incident from the surface side of the functional film 3 is preferably 5.0% or less, more preferably 2.0% or less. By setting the maximum reflectance to 5.0% or less in this way, it is possible to more effectively suppress image defects when the optical member 1 is used. Here, the reflectance is a reflectance measured at an incident angle of 0 degrees using a reflectance measuring device (for example, "USPM-RU" manufactured by Olympus Co., Ltd.).

(Binder layer)
The binder layer 5 contains a binder. The binder may be either an inorganic binder or an organic binder. Examples of the inorganic binder include silica and silicate. Examples of the organic binder include a resin. From the viewpoint of suppressing decomposition of the binder due to photocatalytic activity, the binder is preferably an inorganic binder, and more preferably silica or silicate.

The thickness of the binder layer 5 is preferably 5 nm or more and 50 nm or less, and more preferably 10 nm or more and 30 nm or less. When the thickness of the binder layer 5 is 5 nm or more, the desorption of the photocatalytic secondary particles 4 is effectively suppressed. As a result, the wear resistance of the functional film 3 is further improved. When the thickness of the binder layer 5 is 50 nm or less, the photocatalytic secondary particles 4 are easily exposed from the binder layer 5. As a result, the photocatalytic activity of the functional film 3 is further improved.

<Modification 1>
Next, the optical member 11 according to the modification 1 of the optical member 1 will be described with reference to FIG. The optical member 11 includes a translucent member 12 and a functional film 13 that covers the translucent member 12. The translucent member 12 includes a base material 12a and an antireflection film 12b that covers the base material 12a. The functional film 13 covers the antireflection film 12b in the translucent member 12. The functional film 13 includes a photocatalytic secondary particle 14 and a binder layer 15. At least a part of the photocatalytic secondary particles 14 is partially buried in the binder layer 15.

Compared to the optical member 1 of FIG. 1, the optical member 11 according to the modification 1 is said that the translucent member 12 is not a single member but is composed of a plurality of members (base material 12a and antireflection film 12b). Only the point is different. Therefore, the description overlapping with the optical member 1 will be omitted. The translucent member 12 is provided with the antireflection film 12b, so that the translucent member 12 is excellent in optical characteristics.

(Base material)
The base material 12a has translucency. That is, the base material 12a transmits light. The base material 12a may be transparent or translucent. The base material 12a contains glass or resin.

(Anti-reflective coating)
The antireflection film 12b suppresses the reflection of light. Specifically, the optical member 11 is provided with the antireflection film 12b to prevent light that is about to enter the translucent member 12 from the surface on the functional film 13 side from being reflected on the surface on the functional film 13 side. do.

The antireflection film 12b may have a single-layer structure or a multi-layer structure. The antireflection film 12b contains, for example, a metal or a metal oxide. The antireflection film 12b is, for example, a vapor deposition film or a sputtering film.

The thickness of the antireflection film 12b is preferably 200 nm or more and 400 nm or less. When the thickness of the antireflection film 12b is less than 200 nm, a sufficient antireflection effect tends not to be obtained. When the thickness of the antireflection film 12b exceeds 400 nm, the productivity of the optical member 1 tends to decrease.

<Modification 2>
Next, the optical member 21 according to the second modification of the optical member 1 will be described with reference to FIG. The optical member 21 includes a translucent member 22 and a functional film 23 that covers the translucent member 22. The functional film 23 includes a photocatalytic secondary particle 24 and a binder layer 25. Part of the photocatalyst secondary particles 24 is partially buried in the binder layer 25, and the remaining part is completely buried in the binder layer 25. Specifically, the photocatalytic secondary particles 24 existing near the surface layer of the functional film 23 are partially buried in the binder layer 25. The photocatalytic secondary particles 24 existing in a portion other than the vicinity of the surface layer of the functional film 23 are completely buried in the binder layer 25.

The optical member 21 according to the second modification is different from the optical member 1 in FIG. 1 in that all the photocatalytic secondary particles 24 are partially or completely buried in the binder layer 25. The functional film 23 of the optical member 21 according to the second modification has a maximum thickness similar to that of the functional film 3 of the optical member 1 of FIG. 1, but has a large average thickness. This is because the functional film 3 of the optical member 1 in FIG. 1 has relatively large irregularities, whereas the functional film 23 of the optical member 21 according to the second modification is relatively flat. In the optical member 21 according to the modification 2, the description overlapping with the optical member 1 will be omitted. The optical member 21 is superior to the optical member 1 in FIG. 1 in the wear resistance of the functional film 23.

[Other variants]
The optical member according to the first embodiment has been described above with reference to the drawings. However, the optical member according to the first embodiment is not limited to the optical member 1 of FIG. 1, the optical member 11 of FIG. 2, and the optical member 21 of FIG. Specifically, in the optical member according to the first embodiment, the functional film may further contain other components.

<Second Embodiment: Manufacturing Method of Optical Member>
A method for manufacturing an optical member according to a second embodiment of the present invention will be described. The method for manufacturing an optical member includes a coating step of forming a functional film by applying a coating liquid containing photocatalytic particles activated by ultraviolet rays and a binder raw material to the surface of the translucent member by a wet process. The functional film includes a binder layer covering a translucent member and photocatalytic particles. At least a part of the photocatalytic particles constitutes photocatalytic secondary particles. At least a part of the photocatalytic secondary particles is partially buried in the binder layer. The thickness of the functional film is 15 nm or more and 200 nm or less. As a method for manufacturing an optical member, the optical member according to the first embodiment can be easily and surely manufactured. In particular, by using a wet process for applying the coating liquid, a functional film having the above-mentioned layer structure can be easily and surely formed.

[Applying process]
The coating liquid used in the coating step preferably further contains a solvent. As the solvent, an aqueous solvent is preferable. The water-based solvent contains water and additives. Additives include, for example, organic acids, alcohol compounds and ammonia. The content ratio of the additive in the aqueous solvent is preferably more than 0% by mass and 20% by mass or less. Examples of organic acids include formic acid, acetic acid, propionic acid, succinic acid, citric acid and malic acid. Examples of the alcohol compound include methanol, ethanol, isopropyl alcohol, n-propyl alcohol and butanol.

Examples of the wet process include a spin coating method, a roll coating method, a bar coating method, a dip coating method, a spray coating method, and a method in which these are combined (for example, a dip spin coating method). As the wet process, a spin coating method, a dip coating method or a dip spin coating method is preferable from the viewpoint of easily and surely forming a relatively thin functional film having a thickness of 15 nm or more and 200 nm or less.

It is preferable that the method for manufacturing the optical member further includes a surface treatment step for treating the surface of the translucent member before the coating step. Examples of the surface treatment include plasma treatment, electron beam treatment, corona treatment and frame treatment. Examples of the plasma treatment include high frequency discharge plasma treatment and atmospheric pressure glow discharge plasma treatment. A plurality of these surface treatments can be used in combination.

(Binder raw material)
Examples of the binder raw material contained in the coating liquid include silane compounds and silica particles. Examples of the silane compound include alkoxysilane, silazane, and oligomers made from these (hereinafter, may be referred to as silicate oligomers). Alkoxysilane is a compound represented by the general formula "Si (R ¹ ) _4-X (OR ² ) _X ". In the general formula, R ¹ represents a hydrogen atom, an alkyl group having 1 or more and 10 or less carbon atoms, or an aryl group having 1 or more and 10 or less carbon atoms. R ² represents an alkyl group having 1 or more carbon atoms and 3 or less carbon atoms. R ² preferably represents a methyl group or an ethyl group. In the general formula, X represents an integer of 1 or more and 4 or less, and preferably represents 4. Examples of the alkoxysilane include tetramethoxysilane and tetraethoxysilane. As the binder raw material, a silane compound is preferable, a silicate oligomer is more preferable, and a silicate oligomer made from an alkoxysilane as a raw material is further preferable.

The content ratio of the photocatalyst particles in the coating liquid is preferably 0.01% by mass or more and 50% by mass or less. When the coating liquid is applied by the spin coating method or the dip spin coating method, the rotation speed is preferably 500 rpm or more and 10000 rpm or less. The solid content concentration of the coating liquid is preferably 0.1% by mass or more and 10% by mass or less.

In this step, it is preferable to heat-treat the coating liquid after coating. The heat treatment promotes the removal of volatile components in the coating liquid. When the coating liquid contains a silane compound as a binder raw material, the heat treatment promotes a chemical reaction of the silane compound (for example, a hydrolysis condensation reaction). As the heating conditions, for example, the treatment temperature may be 60 ° C. or higher and 200 ° C. or lower, and the treatment time may be 10 minutes or longer and 10 hours or shorter.

By this step, as shown in FIG. 1, the binder layer 5 is formed from the binder raw material in the coating liquid. The binder layer 5 covers the translucent member 2. At least a part of the photocatalyst particles constitutes the photocatalyst secondary particles 4. At least a part of the photocatalytic secondary particles 4 is partially buried in the binder layer 5.

[Optical member (A-3)]
The optical member (A-3) was manufactured by the following method. The optical member (A-3) had a structure similar to that of the optical member 11 shown in FIG.

(Translucent member)
As a base material, a lens (“TAFD-5G” manufactured by HOYA Corporation, composition: glass, radius of curvature of the lens surface of 12 mm) was prepared. Next, an antireflection film (composition: SiO ₂ layer, TiO ₂ layer, and Ta ₂ O ₅ layer) was formed on the lens. The total thickness of the antireflection film was about 300 nm. As a result, a translucent member was obtained. Next, the surface of the antireflection film of the translucent member was surface-treated. As the surface treatment, plasma treatment using a plasma surface modifier was performed.

(Coating liquid)
As a coating liquid, 100 g of a coating agent (“ST-K50” manufactured by Ishihara Sangyo Co., Ltd.) was prepared. This coating agent contained 0.3 g of titanium oxide particles (primary particle size 5 to 7 nm, secondary particle size 20 to 85 nm), 0.3 g of a binder raw material (silicate), and 99.4 g of a solvent. The solvent was a mixed solvent of water, isopropyl alcohol and ethanol.

The above-mentioned coating liquid was applied to the surface of the antireflection film of the translucent member. The coating liquid was applied using a spin coater (“MS-B100” manufactured by Mikasa Co., Ltd.) at a rotation speed of 3000 rpm. After coating, heat treatment was performed at 85 ° C. for 30 minutes. As a result, an optical member (A-3) was obtained.

The cross section of the optical member (A-3) was observed with a TEM (transmission electron microscope). In the optical member (A-3), the average particle size of the photocatalytic secondary particles was about 40 nm.

The thickness of the functional film of the optical member (A-3) was measured using a contact type film thickness measuring device (“DekTakXT-S” manufactured by Bruker).

The optical member (A-3) was irradiated with fluorescent X-rays from the functional film side, and the integrated intensity of titanium atoms was measured. A fluorescent X-ray measuring machine (“JSX-3202EV” manufactured by JEOL Ltd.) was used for the measurement. The measurement area was 7 mmφ.

[Optical members (A-1) to (A-2) and (A-4) to (A-6)]
The optical members (A-1) to (A) were manufactured by the same method as the optical member (A-3) except that the rotation speed of the spin coater when applying the coating liquid was changed as shown in Table 1 below. -2) and (A-4) to (A-6) were produced. For the optical members (A-1) to (A-2) and (A-3) to (A-6), the thickness of the functional film and the integral of the titanium atom are obtained by the same method as that of the optical member (A-3). The intensity was measured. The measurement results are shown in Table 1 and FIG. 4 below.

As shown in Table 1 and FIG. 4, when a coating liquid having the same composition was used for forming the functional film, the thickness of the formed functional film and the integrated strength of the optical member were generally proportional to each other.

[Optical members (B-1) to (B-6)]
Next, the optical member (B-1) was manufactured by the same method as that for the optical member (A-3), except that the rotation speed of the spin coater when applying the coating liquid was changed as shown in Table 2 below. ... (B-6) was manufactured. For the optical members (B-1) to (B-6), the thickness of the functional film and the integrated strength of the titanium atom were measured by the same method as that of the optical member (A-3). The measurement results are shown in Table 2 below.

[Accelerated deterioration test]
Next, the photocatalytic activity of the functional films of the optical members (B-1) to (B-6) was evaluated. First, the optical members (B-1) to (B-6) were heated at 120 ° C. for 30 minutes to reduce the hydrophilicity of the surface of the functional film (accelerated deterioration test). Next, the contact angle of the surface of the functional film of the optical members (B-1) to (B-6) immediately after the accelerated deterioration test was measured. The obtained result was taken as the contact angle at "irradiation time 0 hours". For the measurement of the contact angle, pure water was used as a sample, and an automatic contact angle meter (“DMo-601” manufactured by Kyowa Interface Science Co., Ltd.) was used as a measuring device. In this embodiment, the subsequent measurement of each contact angle was also performed by the above-mentioned automatic contact angle meter. In this embodiment, the contact angle of the surface of the functional film is determined to be good when it is 30 degrees or less, better when it is 20 degrees or less, and particularly good when it is 15 degrees or less.

Next, the surfaces of the functional films of the optical members (B-1) to (B-6) were irradiated with ultraviolet rays. The irradiation conditions of ultraviolet rays were a wavelength of 352 nm, a radiation time of 75 hours, and an irradiance of 1 mW / cm ² . Then, when the irradiation time of ultraviolet rays reaches a certain time (1 hour, 2 hours, 3 hours, 4 hours, 6 hours, 24 hours, 48 hours, 72 hours or 75 hours) shown in Table 3 below, each optical device is used. The contact angle on the surface of the member functional film was measured. The measurement results are shown in Table 3, FIG. 5 and FIG. 6 below. In Table 3 below, "-" indicates that the contact angle was not measured at the corresponding time.

As shown in Tables 3, 5 and 6, each optical member immediately after the accelerated deterioration test (irradiation time 0 hours) had a relatively high contact angle of the functional film. Further, the optical member (B-1) remained at a high contact angle of the functional film even after being irradiated with ultraviolet rays for 72 hours. That is, the functional film of the optical member (B-1) exhibited almost no photocatalytic activity. On the other hand, in the optical members (B-2) to (B-6), the contact angle of the functional film was reduced to 30 degrees or less by irradiating with ultraviolet rays. That is, the functional films of the optical members (B-2) to (B-6) exhibited photocatalytic activity. From this, it is judged that the thickness of the functional film is preferably 15 nm or more in order to fully exert the photocatalytic activity of the functional film.

Further, in the optical members (B-2) to (B-4), the thicker the functional film (higher integrated strength), the faster the rate of decrease in the contact angle of the functional film tends to be. However, in the optical members (B-4) to (B-6), the rate of decrease in the contact angle of the functional film was about the same. From the above, it is judged that the photocatalytic activity of the functional film improves as the functional film becomes thicker, but reaches a plateau when the functional film becomes thicker than a certain level.

[Wipe test]
The wear resistance of the functional film was measured for the optical members (B-1) to (B-6). First, the contact angle on the surface of the functional film of each optical member was measured. The obtained result was taken as the initial contact angle (A).

Next, using a paper wiper (“Kay Dry (registered trademark)” manufactured by Nippon Paper Crecia Co., Ltd.), the surface of the functional film of each optical member was lightly rubbed 10 times back and forth. Then, the contact angle on the surface of the functional film of each optical member was measured. The obtained result was used as the contact angle (B) for the first wiping treatment.

Next, the surface of the functional film of each optical member was irradiated with ultraviolet rays. The irradiation conditions of ultraviolet rays were a wavelength of 352 nm, 4 hours, and an irradiance of 1 mW / cm ² . When irradiating with ultraviolet rays, the contact angle on the surface of the functional film of each optical member was measured 1 hour, 2 hours, 3 hours or 4 hours after the start of irradiation. The obtained results are shown in the contact angle (C) of the first UV irradiation (1 hour), the contact angle (D) of the first UV irradiation (2 hours), and the contact angle of the first UV irradiation (3 hours), respectively. The contact angle (F) was set to E) and the first UV irradiation (4 hours).

Next, using a paper wiper (“Kay Dry (registered trademark)” manufactured by Nippon Paper Crecia Co., Ltd.), the surface of the functional film of each optical member was lightly rubbed 20 times back and forth. Then, the static contact angle on the surface of the functional film of each optical member was measured. The obtained result was used as the contact angle (G) for the second wiping treatment.

Next, the surface of the functional film of each optical member was irradiated with ultraviolet rays. The irradiation conditions of ultraviolet rays were a wavelength of 352 nm, 24 hours, and an irradiance of 1 mW / cm ² . At the time of irradiation with ultraviolet rays, the contact angle of the surface of the functional film of each optical member was measured 1 hour, 2 hours, 3 hours, 4 hours, 8 hours or 24 hours after the start of irradiation. The obtained results are shown in the contact angle (H) of the second UV irradiation (1 hour), the contact angle (I) of the second UV irradiation (2 hours), and the contact angle of the second UV irradiation (3 hours), respectively. J), the contact angle (K) of the second UV irradiation (4 hours), the contact angle (L) of the second UV irradiation (8 hours), and the contact angle (M) of the second UV irradiation (24 hours).

The contact angle of the functional film of the optical member (B-1) was remarkably high at the second stage of the wiping treatment, and the contact angle did not decrease even when irradiated with ultraviolet rays. Therefore, the optical member (B-1) was judged to have insufficient wear resistance of the functional film, and the subsequent tests were omitted.

Next, using a paper wiper (“Kay Dry (registered trademark)” manufactured by Nippon Paper Crecia Co., Ltd.), the surface of the functional film of each optical member was lightly rubbed 30 times back and forth. Then, the contact angle on the surface of the functional film of each optical member was measured. The obtained result was used as the contact angle (N) for the third wiping treatment.

Next, the surface of the functional film of each optical member was irradiated with ultraviolet rays. The irradiation conditions of ultraviolet rays were a wavelength of 352 nm, 96 hours, and an irradiance of 1 mW / cm ² . At the time of irradiation with ultraviolet rays, the contact angle on the surface of the functional film of each optical member was measured 1 hour, 2 hours, 3 hours, 4 hours, 20 hours or 96 hours after the start of irradiation. The obtained results are shown in the contact angle (O) of the third UV irradiation (1 hour), the contact angle (P) of the third UV irradiation (2 hours), and the contact angle of the third UV irradiation (3 hours), respectively. Q), the contact angle (R) of the third UV irradiation (4 hours), the contact angle (S) of the third UV irradiation (20 hours), and the contact angle (T) of the third UV irradiation (96 hours).

The measurement results are shown in Table 4, FIG. 7 and FIG. 8 below.

As shown in Tables 4, 7 and 8, each optical member was subjected to a wiping treatment to increase the contact angle on the surface of the functional film (decreased hydrophilicity). It is determined that this is because the photocatalytic secondary particles were desorbed from the functional film by the wiping treatment and organic substances adhered to the surface of the functional film. On the other hand, each optical member exhibited photocatalytic activity by irradiation with ultraviolet rays, and the contact angle was lowered (hydrophilicity was restored).

As described above, the optical member (B-1) has insufficient wear resistance of the functional film. On the other hand, in the optical members (B-2) to (B-6), the contact angle of the functional film was lowered to 30 degrees or less by irradiating the optical members with ultraviolet rays even after the wiping treatment was performed three times. That is, the functional films of the optical members (B-2) to (B-6) had sufficient wear resistance. From this, it is judged that the thickness of the functional film is preferably 15 nm or more in order to secure the wear resistance of the functional film.

[Optical members (C-1) to (C-4)]
Next, the optical member (C-1) was manufactured by the same method as that for the optical member (A-3), except that the rotation speed of the spin coater when applying the coating liquid was changed as shown in Table 5 below. -(C-4) was manufactured. For the optical members (C-1) to (C-4), the thickness of the functional film and the integrated strength of the titanium atom were measured by the same method as that of the optical member (A-3). The measurement results are shown in Table 5 below.

[Reflectance]
For the optical members (C-1) to (C-4), the maximum reflectance with respect to the incident light having a wavelength of 450 nm or more and 780 nm or less incident from the surface side of the functional film was measured. For the measurement, a reflectance measuring device (“USPM-RU” manufactured by Olympus Co., Ltd.) was used to measure the reflectance measured at an incident angle of 0 degrees. In the measurement, first, a graph of the spectral reflectance in the wavelength range of 380 nm or more and 800 nm or less was created. A graph of spectral reflectance is shown in FIG. Based on the spectral reflectance graph, the maximum reflectance for incident light having a wavelength of 450 nm or more and 780 nm or less was determined. For each optical member, the maximum reflectance and the wavelength of the incident light when the maximum reflectance is measured are shown below.

Optical member (C-1): Maximum reflectance 0.8% (wavelength 656 nm)
Optical member (C-2): Maximum reflectance 1.2% (wavelength 655 nm)
Optical member (C-3): Maximum reflectance 1.7% (wavelength 655 nm)
Optical member (C-4): Maximum reflectance 2.3% (wavelength 655 nm)

If the maximum reflectance of the optical member is 5.0% or less, it can sufficiently withstand practicality, but 2.5% or less is preferable in consideration of manufacturing error. As is clear from the optical members (C-1) to (C-4), the thicker the functional film, the higher the maximum reflectance of the optical member. From the viewpoint of suppressing the maximum reflectance of the optical member, it is judged that the thickness of the functional film is preferably 200 nm or less.

[Optical member (D-1)]
A titanium oxide vapor-deposited film was formed on the surface of the antireflection film of the translucent member. A thin-film deposition device was used to form the thin-film deposition film. As a result, an optical member (D-1) was obtained.

[Optical member (D-2)]
Next, the optical member (D-2) was manufactured by the same method as that for the optical member (A-3), except that the rotation speed of the spin coater when applying the coating liquid was changed as shown in Table 6 below. Manufactured.

For the optical members (D-1) to (D-2), the thickness of the functional film and the integrated strength of the titanium atom were measured by the same method as that of the optical member (A-3). The measurement results are shown in Table 5 below. The functional film of the optical member (D-1) was a film in which titanium oxide particles were densely packed, and its surface was smooth. Unlike the functional film 3 of FIG. 1, the functional film 13 of FIG. 2, and the functional film 23 of FIG. 3, the functional film of the optical member (D-1) had almost no gaps between the titanium oxide particles.

[Reflectance]
For the optical members (D-1) to (D-2), the maximum reflectance with respect to the incident light having a wavelength of 450 nm or more and 780 nm or less incident from the surface side of the functional film was measured. For the measurement, a reflectance measuring device (“USPM-RU” manufactured by Olympus Co., Ltd.) was used to measure the reflectance measured at an incident angle of 0 degrees. In the measurement, first, for the optical member (D-1), a graph of the spectral reflectance in the wavelength range of 380 nm or more and 780 nm or less was prepared. For the optical member (D-2), a graph of spectral reflectance in the wavelength range of 380 nm or more and 800 nm or less was created. A graph of spectral reflectance is shown in FIG. Based on the spectral reflectance graph, the maximum reflectance for incident light having a wavelength of 450 nm or more and 780 nm or less was determined. For each optical member, the maximum reflectance and the wavelength of the incident light when the maximum reflectance is measured are shown below.

Optical member (D-1): Maximum reflectance 22.6% (wavelength 775 nm)
Optical member (D-2): Maximum reflectance 0.7% (wavelength 657 nm)

As is clear from the optical members (D-1) to (D-2), the optical member having the functional film formed by thin film deposition had a high maximum reflectance. From this, from the viewpoint of suppressing the maximum reflectance of the optical member, the photocatalytic particles contained in the functional film do not exist in a densely packed state, but exist in a state in which secondary particles are formed and appropriately dispersed. Is judged to be preferable. Further, it is judged that it is preferable that the functional film has appropriate unevenness.

The present invention is suitable as an optical member for a sensor or a photographing device or a method for manufacturing the same.

1,11,21 Optical member 2,12,22 Translucent member 12a Base material 12b Antireflection film 3,13,23 Functional film 4,14,24 Photocatalytic secondary particles 5,15,25 Binder layer

Claims (9)

Translucent member and
A functional film that covers the translucent member is provided.
The functional membrane is
It contains photocatalytic particles activated by ultraviolet rays and a binder layer covering the translucent member.
At least a part of the photocatalytic particles constitutes photocatalytic secondary particles.
At least a part of the photocatalytic secondary particles is partially buried in the binder layer.
An optical member having a functional film having a thickness of 15 nm or more and 200 nm or less. The optical member according to claim 1, wherein the photocatalytic particles contain titanium oxide. The optical member according to claim 2, wherein the integrated intensity of titanium atoms measured by fluorescent X-rays is 600 or more and 35,000 or less. The optical member according to any one of claims 1 to 3, wherein the ratio of the occupied area of the photocatalytic particles in the plan view of the functional film is 5% or more and 100% or less. The optical member according to any one of claims 1 to 4, wherein the average particle size of the photocatalytic secondary particles is 10 nm or more and 50 nm or less. The optical member according to any one of claims 1 to 5, wherein the maximum reflectance for incident light having a wavelength of 450 nm or more and 780 nm or less incident from the surface side of the functional film is 5.0% or less. The optical member according to any one of claims 1 to 6, wherein the functional film has a thickness of 40 nm or more. The translucent member is
With the base material
The optical member according to any one of claims 1 to 7, further comprising an antireflection film covering the substrate. It is provided with a coating step of forming a functional film by applying a coating liquid containing photocatalytic particles activated by ultraviolet rays and a binder raw material to the surface of a translucent member by a wet process.
The functional membrane is
The binder layer covering the translucent member and the photocatalytic particles are included.
At least a part of the photocatalytic particles constitutes photocatalytic secondary particles.
At least a part of the photocatalytic secondary particles is partially buried in the binder layer.
A method for manufacturing an optical member, wherein the thickness of the functional film is 15 nm or more and 200 nm or less.

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