阅读说明：本技术 防反射膜及光学部件 (Antireflection film and optical member ) 是由 高桥裕树 于 2018-03-23 设计创作，主要内容包括：本发明能够提供一种防反射膜及光学部件。设置于光学部件(1)的光学基材(2)上的防反射膜(3)具备：反射率调整膜(4),包含第1层(10)、比第1层(10)高折射率的第2层(11)及比第2层(11)低折射率的第3层(12),且自表面(4a)起的厚度为20nm以上且小于150nm；及光催化膜(5),包含含有二氧化钛的一层以上的光催化活性层(14),设置于反射率调整膜(4)与光学基材(2)之间且反射率调整膜侧的界面(5a)配置于自表面(4a)起150nm以下的位置,并且光催化活性层(14)的合计厚度为350nm以上且1000nm以下。(The invention can provide an antireflection film and an optical member. An antireflection film (3) provided on an optical substrate (2) of an optical component (1) is provided with: a reflectance control film (4) which comprises a 1 st layer (10), a 2 nd layer (11) having a higher refractive index than the 1 st layer (10), and a 3 rd layer (12) having a lower refractive index than the 2 nd layer (11), and which has a thickness of 20nm or more and less than 150nm from a surface (4 a); and a photocatalytic film (5) that includes one or more photocatalytically active layers (14) containing titanium dioxide, is provided between the reflectance adjustment film (4) and the optical substrate (2), and has an interface (5a) on the reflectance adjustment film side disposed at a position that is 150nm or less from the surface (4a), and has a total thickness of the photocatalytically active layers (14) that is 350nm or more and 1000nm or less.)

1. An antireflection film provided on an optical substrate, the antireflection film comprising:

a reflectance control film including a 1 st layer, a 2 nd layer disposed on a surface side of the antireflection film with respect to the 1 st layer and having a higher refractive index than the 1 st layer, and a 3 rd layer disposed on the surface side with respect to the 2 nd layer and having a lower refractive index than the 2 nd layer, and having a thickness of 20nm or more and less than 150nm from the surface; and

a photocatalytic film comprising one or more photocatalytically active layers containing titanium dioxide, the photocatalytic film being provided between the reflectance control film and the optical substrate, and an interface on the reflectance control film side being disposed at a position of 150nm or less from the surface, and the photocatalytically active layers having a total thickness of 350nm or more and 486nm or less.

2. The antireflection film according to claim 1,

the material forming the 1 st layer is selected from SiO₂Magnesium fluoride, Si₃N₄The material (a) of (b) is,

the material forming the 2 nd layer is selected from TiO₂、ITO、ZnO、SnO₂、In₂O₃、Nb₂O₅、Ta₂O₅A material of TiN or ZrO,

the material forming the 3 rd layer is selected from SiO₂Magnesium fluoride, Si₃N₄The material of (1).

3. The antireflection film according to claim 2,

the material forming the 1 st layer and the material forming the 3 rd layer are both SiO₂Or magnesium fluoride.

4. The antireflection film according to claim 2,

the material for forming the 2 nd layer is TiO₂。

5. The antireflection film according to claim 2,

the photocatalytically active layer included in the photocatalytic film is a multilayer.

6. The antireflection film according to claim 1,

the photocatalytically active layer included in the photocatalytic film is one layer.

7. The antireflection film according to any one of claims 1 to 6,

the crystal structure of titanium dioxide contained in the photocatalytically active layer is an anatase structure.

8. The antireflection film according to any one of claims 1 to 6,

the photocatalytically active layer further contains one or more elements selected from the group consisting of nitrogen, sulfur, chromium, antimony, and cerium.

9. The antireflection film according to any one of claims 1 to 6,

the 3 rd layer comprises silicon dioxide and forms the surface.

10. An optical member having the antireflection film according to any one of claims 1 to 9 provided on an optical substrate.

11. The optical component of claim 10,

the optical substrate is a lens.

Technical Field

The present invention relates to an antireflection film and an optical member.

Background

Dirt adheres to the surface of an optical component such as a lens or a cover of a camera installed outdoors, such as a monitoring camera or a vehicle-mounted camera, and the surface of the optical component to which dirt adheres is generally hydrophobic. When the surface of the hydrophobic optical member is wetted with water, water droplets remain on the surface of the optical member, and the water droplets obstruct the field of view. Therefore, as an antireflection film constituting the surface of the optical member, an antireflection film in which the hydrophilicity of the surface is maintained by the self-cleaning action of titanium dioxide having photocatalytic activity is known.

The antireflection film described in patent document 1 is an antireflection film provided on a substrate, and is formed by alternately laminating 4 layers of a high refractive index layer containing titanium dioxide and a low refractive index layer containing silicon dioxide, and the surface of the antireflection film is formed of the low refractive index layer. In the thickness of each layer of the examples, the thickness of the 1 st layer as a high refractive index layer, the 2 nd layer as a low refractive index layer, the 3 rd layer as a high refractive index layer, and the 4 th layer as a low refractive index layer constituting the surface were 15nm, 30nm, 120nm, and 90nm, respectively, in this order from the substrate side.

The antireflection film described in patent document 2 is an antireflection film provided on a substrate, and is formed by alternately laminating 4 layers of a high refractive index layer containing titanium dioxide and a low refractive index layer containing silicon dioxide, and the surface of the antireflection film is composed of a low refractive index layer, as in the antireflection film described in patent document 1. Further, regarding the thickness of each layer of the examples, the 1 st layer as a high refractive index layer was 20nm, the 2 nd layer as a low refractive index layer was 25nm, the 3 rd layer as a high refractive index layer was 240nm, and the 4 th layer as a low refractive index layer constituting the surface was 90nm in this order from the substrate side.

Prior art documents

Patent document

Patent document 1: japanese laid-open patent publication No. 2008-003390

Patent document 2: japanese patent laid-open publication No. 2016-224113

Disclosure of Invention

Technical problem to be solved by the invention

The self-cleaning effect of titanium dioxide is provided by decomposing dirt attached to the surface by oxygen radicals generated in titanium dioxide. In the anti-reflection film described in patent document 1 and the anti-reflection film described in patent document 2, the 3 rd layer containing titanium dioxide is covered with the 4 th layer constituting the surface of the anti-reflection film, and the 4 th layer is preferably thin in view of efficiently transporting oxygen radicals generated in the 3 rd layer to the surface of the anti-reflection film. Further, the 3 rd layer is preferably thick from the viewpoint of increasing the generation amount of oxygen radicals.

On the other hand, in view of the practical use as an antireflection film, for example, in order to realize an average reflectance of 1% or less in a wavelength range of 400nm to 700nm, it is preferable that the thickness of the 4 th layer containing silica constituting the surface of the antireflection film is 20nm or more, and the thickness of the 3 rd layer containing titania adjacent to the 4 th layer is 150nm or less.

In the antireflection film described in patent document 1, the thickness of the 4 th layer containing silicon dioxide is 90nm, and the thickness of the 3 rd layer containing titanium dioxide is 120 nm. In this case, oxygen radicals are insufficient, and a self-cleaning effect sufficient to maintain the hydrophilicity of the surface may not be obtained. In the antireflection film described in patent document 2, the thickness of the 4 th layer containing silicon dioxide is 90nm, and the thickness of the 3 rd layer containing titanium dioxide is 240 nm. In this case, the band having an average reflectance of 1% or less is narrowed, and there is a possibility that the practical applicability as an antireflection film is poor.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an antireflection film and an optical member that can achieve both improvement of reflectance characteristics and maintenance of hydrophilicity of the surface.

Means for solving the technical problem

An antireflection film according to an aspect of the present invention is an antireflection film provided on an optical substrate, and includes: a reflectance control film including a 1 st layer, a 2 nd layer disposed on a surface side of the antireflection film with respect to the 1 st layer and having a higher refractive index than the 1 st layer, and a 3 rd layer disposed on the surface side with respect to the 2 nd layer and having a lower refractive index than the 2 nd layer, and having a thickness of 20nm or more and less than 150nm from the surface; and a photocatalytic film including one or more photocatalytically active layers containing titanium dioxide, the photocatalytic film being provided between the reflectance control film and the optical substrate, and an interface on the reflectance control film side being disposed at a position of 150nm or less from the surface, and the total thickness of the photocatalytically active layers being 350nm or more and 1000nm or less.

In the optical member according to one aspect of the present invention, the antireflection film is provided on an optical substrate.

Effects of the invention

According to the present invention, an antireflection film and an optical member can be provided that can achieve both improvement in reflectance characteristics and maintenance of hydrophilicity of the surface.

Drawings

Fig. 1 is a schematic diagram for explaining an example of an optical member according to an embodiment of the present invention.

Fig. 2 is a schematic view of a modification of the optical member of fig. 1.

Fig. 3 is a schematic view of another modification of the optical member of fig. 1.

Fig. 4 is a schematic diagram showing the crystal structure of the anatase structure of titanium dioxide.

Fig. 5 is a graph showing XRD measurement results of the photocatalytic film containing titanium oxide.

Fig. 6 is a graph showing XRD measurement results of the photocatalytic film containing titanium oxide.

Detailed Description

The optical member 1 shown in fig. 1 includes an optical substrate 2 and an antireflection film 3 provided on the optical substrate 2.

The optical substrate 2 may be an optical element such as a lens, or may be a thin film, and the form is not particularly limited. Examples of the lens include an in-vehicle lens, a monitoring camera lens, an interchangeable lens, and a television camera. When the optical substrate 2 is a film, the optical member 1 is used while being attached to the surface of an optical element such as a lens. The material of the optical substrate 2 is glass or resin, and examples of the resin include polycarbonate, cycloolefin, polyimide, and the like, and polyimide having excellent heat resistance and a glass transition temperature of 300 ℃ or more, preferably 350 ℃ or more is preferable in relation to a method for producing an antireflection film described later.

The antireflection film 3 includes a reflectance adjustment film 4 and a photocatalytic film 5 provided between the reflectance adjustment film 4 and the optical substrate 2. The photocatalytic film 5 generates oxygen radicals by light irradiation, and the oxygen radicals generated in the photocatalytic film 5 decompose the dirt attached to the surface 4a of the reflectance control film 4 that is in contact with the external air. The self-cleaning action provided by the oxygen radicals can inhibit the surface 4a from becoming hydrophobic.

Preferably, the surface 4a is formed of a hydrophilic material. Here, the term "hydrophilic" on the surface 4a means that the contact angle with water is 10 ° or less, and the contact angle is measured by the sessile drop method specified in JIS R3257. As the hydrophilic material forming the surface 4a, SiO can be exemplified₂(silica), and the like.

The reflectance control film 4 includes a 1 st layer 10, a 2 nd layer 11 disposed on the surface 4a side of the 1 st layer 10 and having a higher refractive index than the 1 st layer 10, and a 3 rd layer 12 disposed on the surface 4a side of the 2 nd layer 11 and having a lower refractive index than the 2 nd layer 11. As a material for forming the 1 st layer 10 and the 3 rd layer 12, SiO can be exemplified₂、MgF₂(magnesium fluoride), Si₃N₄(silicon nitride) and Al₂O₃A low refractive index material having a refractive index of 1.6 or less, such as (alumina), and TiO can be exemplified as a material for forming the 2 nd layer 11 having a relatively high refractive index₂(titanium dioxide), ITO (tin-doped indium oxide), ZnO (zinc oxide), SnO₂(tin dioxide), In₂O₃(indium oxide), Nb₂O₅(niobium pentoxide), Ta₂O₅High refractive index materials having a refractive index of 1.8 or more, such as tantalum pentoxide, TiN (titanium nitride), and ZrO (zirconium oxide).

When the 3 rd layer 12 is made of hydrophilic SiO₂In the formation, as shown in fig. 1, the surface 4a can be formed of the 3 rd layer 12. On the other hand, when the 3 rd layer 12 is made of non-hydrophilic MgF₂Or Al₂O₃In the formation, as shown in fig. 2, a hydrophilic surface layer 13 may be provided on the surface 4a side of the 3 rd layer 12, and the surface 4a may be formed by the surface layer 13.

The 3 rd layer 12 or the surface layer 13 forming the surface 4a may be formed in a porous state having fine irregularities from the viewpoint of making the surface 4a hydrophilic, and is preferably formed in a solid state from the viewpoint of improving abrasion resistance.

In addition, an intermediate layer may be provided between the 1 st layer 10 and the 2 nd layer 11. As the intermediate layer, an intermediate layer having an intermediate refractive index between the refractive index of the 1 st layer 10 and the refractive index of the 2 nd layer 11 can be exemplified. Likewise, an intermediate layer may be provided between the 2 nd layer 11 and the 3 rd layer 12.

The thickness of each of the 1 st layer 10, the 2 nd layer 11, and the 3 rd layer 12 can be appropriately set according to the refractive index of each layer, the wavelength range in which reflection is suppressed, and the like. For example, when the 1 st and 3 rd layers 10, 12 comprise SiO₂The 2 nd layer 11 contains TiO₂And when the average reflectance is less than 1% in the wavelength range of 400nm to 700nm, the thickness of the 1 st layer 10 is preferably 15nm to 40nm, the thickness of the 2 nd layer 11 is preferably 10nm to 25nm, and the thickness of the 3 rd layer 12 is preferably 20nm to 100 nm. Wherein the entire thickness of the reflectance control film 4 is 20nm or more and less than 150 nm. If the thickness of the entire reflectance control film 4 is less than 20nm, reflectance characteristics having an average reflectance of 1% or less may not be obtained in the wavelength range of 400nm to 700 nm. If the entire thickness of the reflectance adjusting film 4 is 150nm or more, the transport of oxygen radicals generated in the photocatalytic film 5 to the surface 4a is hindered, and the self-cleaning effect may not be obtained.

The photocatalytic film 5 contains TiO₂A photocatalytically active layer 14 of (titanium dioxide). The photocatalytically active layer 14 may be a single layer as shown in fig. 1, or may be a plurality of layers as shown in fig. 3. When the photocatalytic film 5 includes a plurality of photocatalytically active layers 14, as a material of the intermediate layer 15 interposed between adjacent two photocatalytically active layers 14, a material other than the above-described low refractive index material (SiO) can be exemplified₂、MgF₂、Si₃N₄Etc.) and TiO₂Other high refractive index materials (ITO, ZnO, SnO)₂、In₂O₃、Nb₂O₅、Ta₂O₅TiN, ZrO, etc.).

From the viewpoint of exhibiting a self-cleaning effect, the total thickness of the photocatalytically active layer 14 is 350nm or more and 1000nm or less, preferably 350nm or more and 500nm or less. In addition, the interface 5a on the reflectance control film 4 side of the photocatalytic film 5 is disposed at a position of 150nm or less from the surface 4a, from the viewpoint of efficiently transporting oxygen radicals generated in the photocatalytically active layer 14 to the surface 4 a.

The thicknesses of each layer forming the reflectance adjusting film 4 and each layer forming the photocatalytic film 5 are measured by an optical film thickness meter (incorporated in a film forming machine described later). The film thickness of the sample was measured by observation with a Transmission Electron Microscope (TEM) as a cross-section, and it was confirmed whether or not the measured value of the optical film thickness and the measured value of the TEM were equal to each other at-3 nm to +3 nm.

TiO contained in the photocatalytically active layer 14 is preferable₂The crystal structure of (a) is an anatase structure. With rutile-structured TiO₂In contrast, TiO of anatase structure₂Has excellent photocatalytic activity. In addition, as shown in fig. 4, the crystal structure of the anatase structure is tetragonal, and has a structure in which Ti is surrounded by 6O.

TiO contained in the photocatalytic active layer 14₂At least one element selected from the group consisting of N (nitrogen), S (sulfur), Cr (chromium), Sb (antimony), and Ce (cerium) may be doped. By doping these elements, the photocatalytic activity of the photocatalytically active layer 14 can be further improved. The doping amount is preferably 0.01 mol% or more and 0.05 mol% or less in terms of a molar ratio of Ti to the doping element. By TiO₂Part of Ti ions on the film surface is replaced by cations (Cr)³⁺、Sb³⁺、Ce³⁺) Or TiO₂Part of the oxygen ions on the membrane surface is replaced by anions (N, S (valence number is not labeled in various words)), and the photocatalytic activity can be improved. Among these, when the amount of the doping element is less than 0.01 mol%, improvement of TiO by substitution with the above-mentioned ion cannot be expected₂The photocatalytic activity of the film, and if the amount of the doping element exceeds 0.05 mol%, the doping element is agglomerated in TiO₂On the surface of the film, it is possible to make TiO₂The photocatalytic activity of the film decreases.

The antireflection film 3 described above is produced by sequentially forming the photocatalytic film 5 and the reflectance adjusting film 4 on the optical substrate 2, and a vapor deposition method can be used for the film formation. SiO-containing by vapor deposition₂Layer 1 of equal low refractive index 10, TiO₂Equal-height refractive index 2 nd layer 11 and SiO₂The formation of the reflectance adjusting film 4 of the 3 rd layer 12 having a low refractive index is well known, and the formation of the photocatalytic film 5 will be described below.

In the presence of TiO₂In the formation of the photocatalytically active layer 14, Ti can be used as a vapor deposition material₃O₅(titanium pentoxide). By using Ti₃O₅As a deposition material, with TiO₂The photocatalytically active layer 14 having less oxygen vacancies can be formed as a vapor deposition material.

By photocatalytic reaction of TiO contained in the active layer 14₂Electrons in the valence band are excited to the conduction band by the irradiation of light, and oxygen is reduced by the electrons excited to the conduction band by oxygen to generate oxygen radicals. In this electron transition, an oxygen vacancy forms a trap level between a valence band level and a conduction band level, and an electron excited into the conduction band is trapped in the oxygen vacancy. As a result, electrons contributing to the generation of oxygen radicals are reduced, and the photocatalytic activity is lowered. By using Ti₃O₅The vapor deposition material can suppress the generation of oxygen vacancies and can improve the photocatalytic activity of the photocatalytic active layer 14.

The temperature of the optical substrate 2 is preferably set to 300 ℃ to 350 ℃ when the photocatalytic active layer 14 is formed. Thereby, TiO having an anatase structure can be promoted₂And (4) generating. If the temperature of the optical substrate 2 is too low (e.g., 200 ℃ or lower), the TiO having an amorphous structure which does not exhibit photocatalytic activity is promoted₂When the temperature of the optical substrate 2 is too high (for example, 400 ℃ or higher), the rutile-structured TiO is promoted₂And (4) generating.

It is preferable that the photocatalytic active layer 14 is formed in an atmosphere into which oxygen is introduced, and the flow rate of oxygen is set to 100 × 1.69 × 10 in terms of 0 ℃^-3Pa·m³120X 1.69X 10,/sec or more^-3Pa · m3/sec or less. Thus, TiO having an anatase structure can be improved₂The crystallinity of (2) can further improve the photocatalytic activity of the photocatalytic active layer 14.

It is preferable that the photocatalytic film 5 formed on the optical substrate 2 is annealed, the temperature of the annealing atmosphere (hereinafter referred to as annealing temperature) is set to 350 ℃ to 400 ℃, and the annealing time is set to 2 hours to 6 hours. This can improve the continuity of the photocatalytic activity of the photocatalytic active layer 14.

Presuming the persistence of photocatalytic activity based on annealing the photocatalytic film 5 with TiO₂The reduction of the energy level of the impurity contained in (1) has a correlation, and TiO is considered to be the same as the oxygen vacancy level₂The energy level of the impurity contained in (1) is TiO₂The electrons generated in (b) become trap levels in transition, and the photocatalytic activity of the photocatalytic active layer 14 is lowered. In the experiment conducted by the present inventors, it was confirmed by Electron Paramagnetic Resonance (ESR) measurement that TiO was annealed to the photocatalytic film 5 under the above-described conditions₂The energy level of impurities contained in (1) is reduced.

Further, the effect of sustaining the photocatalytic activity of the annealed photocatalytic active layer 14 is also affected by the annealing atmosphere, and the effect of sustaining the photocatalytic activity can be improved by annealing the photocatalytic film 5 in the air as compared with the case where the photocatalytic film 5 is annealed in oxygen.

And, when TiO is contained in the photocatalytic film 5 (photocatalytic active layer 14)₂When the film is doped with a different element (N, S, Cr, Sb, Ce), TiO can be formed on the film by using an ion implantation apparatus₂The sample of the film is doped, and the doping method can be, for example, the method described in japanese patent application laid-open No. 9-262482. Then, the film formation of the reflectance adjusting film 4 is performed after doping with the different element.

Hereinafter, experimental examples will be described.

<TiO₂Crystal structure of photocatalytic film>

Using Ti₃O₅As a deposition material, white plate glass (FD110 HOYA) was used as an optical substrate, and TiO-containing material was deposited by electron beam deposition₂A single photocatalytic film having a thickness of 300nm is formed on an optical substrate. In addition, the film forming machine uses SHINCRON CO.Manufactured ACE-1800. Further, the temperature of the optical substrate at the time of film formation of the photocatalytic film is changed in the range from not heated to 400 ℃ while being changed in the range from 0 to 120X 1.69X 10^-3Pa·m³The flow rate of oxygen introduced into the chamber of the film forming machine was varied in the range of/sec, the obtained photocatalytic film was subjected to X-ray diffraction (XRD) measurement, and TiO contained in the photocatalytic film was analyzed₂The crystal structure of (1). The measurement apparatus and measurement conditions used in the XRD measurement are as follows.

An apparatus: RINT-2500 (manufactured by Rigaku Corporation)

Source of radiation: cu k alpha 55kV and 280mA

An optical system

Divergent Slit (DS: Divergence Slit): 1.0 degree

Scattering Slit (SS): 1.0 degree

Receiving Slit (RS): 0.3mm

The results of the analysis of the crystal structure are shown in table 1.

[ Table 1]

As shown in Table 1, when the temperature of the optical base material at the time of forming the photocatalytic film was set to 300 ℃ or more and 350 ℃ or less, TiO having an anatase structure was obtained₂. The amount of oxygen introduced during the formation of the photocatalytic film was 100X 1.69X 10 in terms of 0 ℃ C^-3Pa·m³120X 1.69X 10,/sec or more^-3Pa·m³At a temperature of sec or less, highly crystalline anatase-structured TiO having excellent photocatalytic activity is obtained₂. With respect to TiO₂The crystallinity of (4) is such that the temperature of the optical substrate is 300 ℃ and the amount of oxygen introduced is 70X 1.69X 10^-3Pa·m³XRD measurement results at/sec are shown in FIG. 5, and similarly, the temperature of the optical base material was set to 300 ℃ and the oxygen introduction amount was set to 100X 1.69X 10^-3Pa·m³The XRD measurement results at/sec are shown in FIG. 6.

In the XRD measurement results of both FIGS. 5 and 6, the XRD peak positions were the same as those of TiO in anatase₂The peak positions (literature values) of (A) are consistent with each other, but the base line on the low angle side (2 θ ≦ 40 °) is lowered and the intensity of each peak is increased in the XRD measurement result shown in fig. 6, as compared with the XRD measurement result shown in fig. 5. From this, it is found that the amount of oxygen introduced is 100X 1.69X 10^-3Pa·m³TiO at/sec₂The crystallinity of (2) is relatively high.

< film thickness dependence of photocatalytic Activity of photocatalytic film >

Next, TiO was evaluated₂The photocatalytic activity of the photocatalytic film is related to the film thickness. Using Ti₃O₅As a deposition material, white plate glass (FD110 HOYA) was used as an optical substrate, and TiO-containing material was deposited by electron beam deposition₂The single-layer photocatalytic film of (2) is formed on an optical substrate. Furthermore, SiO is used₂As a deposition material, SiO with a thickness of 50nm was deposited by electron beam deposition₂The film was formed on the photocatalytic film to prepare an evaluation sample. The temperature of the optical substrate at the time of forming the photocatalytic film was set to two temperatures of 300 ℃ and 350 ℃, and the amount of oxygen introduced was set to 100 × 1.69 × 10^-3Pa·m³Sec, will be subjected to SiO₂The temperature of the optical substrate during film formation was the same as that during film formation of the photocatalytic film, and the amount of oxygen introduced was 0.

SiO on the surface of a sample is measured by the following procedure for a plurality of evaluation samples with the thickness of the photocatalytic film changed in the range of 10nm to 500nm₂The contact angle of the film with water, and the film thickness dependence of the photocatalytic activity of the photocatalytic film was evaluated from the contact angle. In the measurement of the contact angle, first, an automobile wax (trade name "New Willson", manufactured by Willson) was wiped on the sample surface using a cotton swab, and after 24 hours had elapsed since the wax was applied, the wax applied to the sample surface was removed with a neutral detergent and water, and the contact angle θ 1 with water of the sample surface from which the wax was removed was measured. Then, the sample surface was irradiated with ultraviolet light, and after irradiation, the contact angle θ 2 with water of the sample surface was measured again. In addition, a light source of ultraviolet lightUV-B ultraviolet lamp 20WGL20SE manufactured by SANKYO DENKI Co., Ltd. was used, and irradiation conditions were set to UV illuminance of 3mw/cm²The irradiation time was 40 minutes (equivalent to 7.2J/cm)²). The contact angle measuring apparatus used DM300 manufactured by Kyowa Interface Science co. Hereinafter, the step of measuring the contact angle is referred to as a WAX test.

The measurement results of the contact angle θ 2 are shown in table 2. The contact angle θ 2 in table 2 is an average value of the measurement values obtained by measuring the contact angle three times for each sample.

[ Table 2]

The contact angle θ 1 was 50 ° or more in any of the evaluation samples. On the other hand, as shown in table 2, the contact angle θ 2 after the ultraviolet irradiation of the sample having the photocatalytic film thickness of 350nm or more is 5 ° or less, which is called super-hydrophilicity. From the measurement results, it was found that TiO contained in the photocatalytic film was expressed₂In the self-cleaning action(s), the thickness of the photocatalytic film (the total thickness of the photocatalytic active layers) is required to be 350nm or more.

< continuation of photocatalytic Activity of photocatalytic film >

Next, the above evaluation sample having a photocatalytic film thickness of 350nm and the above evaluation sample having a photocatalytic film thickness of 500nm were subjected to annealing in air while changing the annealing temperature and the annealing time. The above WAX test was repeated on the annealed sample, and the photocatalytic activity of the photocatalytic film was evaluated for its persistence by the number of tests in which the contact angle with water of the sample surface after ultraviolet irradiation was 5 ° or less.

The results of the evaluation of the durability are shown in Table 3. The number of tests in table 3 is the number of times when the annealing time was 4 hours.

[ Table 3]

As shown in table 3, it is understood that the durability of the photocatalytic activity of the photocatalytic film is improved by annealing in air at an annealing temperature of 350 ℃ to 400 ℃. The annealing temperature is suitably determined depending on the thickness of the photocatalytic film, and is preferably 350 ℃ when the thickness of the photocatalytic film is 350nm, and preferably 400 ℃ when the thickness of the photocatalytic film is 500 nm. The number of tests in table 3 was the number of times when the annealing time was 4 hours, and the same results as in table 3 were obtained within the range of 2 to 6 hours.

< reflectance characteristics and self-cleaning action of optical Member >

Next, the optical members shown in fig. 1 and 2 were produced, and the reflectance characteristics and the self-cleaning effect of the produced optical members were evaluated. The optical members of experimental examples 1, 2, 4 to 7 have the structures shown in fig. 1, and films containing TiO were sequentially formed on the optical substrate 2₂The single-layer photocatalytic film 5 and the reflectance adjusting film 4 are formed of a material containing SiO in this order from the optical substrate 2 side₂Layer 1 of (2), containing TiO₂And layer 2 of (1) and comprising SiO₂The 3 rd layer 12 of (b) constitutes the reflectance adjusting film 4. The optical member of experimental example 3 has the structure shown in fig. 2, and films containing TiO were sequentially formed on the optical substrate 2₂The single-layer photocatalytic film 5 and the reflectance adjusting film 4 are formed of MgF in this order from the optical substrate 2 side₂Layer 1 of (2), containing TiO₂Layer 2 of (2) containing MgF₂And layer 3 of (2) and comprising SiO₂The surface layer 13 constitutes the reflectance adjusting film 4. In the optical member of experimental example 8, the film containing TiO was sequentially formed on the optical substrate 2₂And a single layer photocatalytic film 5 comprising SiO₂The single-layer reflectance adjusting film 4.

In the optical members of experimental examples 1 to 8, a white plate glass (manufactured by FD110 HOYA) was used in common as the optical substrate 2. And, comprises TiO₂The single-layer photocatalytic film 5 is formed using Ti₃O₅The temperature of the optical substrate 2 as a deposition material was set to 350 ℃ and oxygen was addedThe introduction amount was set to 100X 1.69X 10^-3Pa·m³And/sec, film formation was performed by electron beam evaporation. The photocatalytic film 5 formed on the optical substrate 2 was annealed in air at an annealing temperature of 350 ℃ for 4 hours. And, the reflectance adjusting film 4 contains TiO₂The 2 nd layer 11 of (2) is formed by using Ti₃O₅As a vapor deposition material, the temperature of the optical substrate 2 was 350 ℃ and the amount of oxygen introduced was 100X 1.69X 10^-3Pa·m³And/sec, film formation was performed by electron beam evaporation. SiO is contained in the reflectance adjusting film 4₂The 1 st layer 10, the 3 rd layer 12 and the surface layer 13 of (A) are formed of SiO₂As a vapor deposition material, film formation was performed by electron beam vapor deposition with the temperature of the optical substrate 2 set to 350 ℃ and the amount of oxygen introduced set to 0. The reflectance adjusting film 4 contains MgF₂The 1 st layer 10 and the 3 rd layer 12 of (A) are formed using MgF₂As a vapor deposition material, film formation was performed by electron beam vapor deposition with the temperature of the optical substrate 2 set to 350 ℃ and the amount of oxygen introduced set to 0.

The reflectance characteristics were evaluated based on the presence or absence of pulsation (fluctuation) and the degree of pulsation in the reflectance characteristic curve in the wavelength range of 400nm to 700nm, and the average reflectance in the wavelength range of 400nm to 700 nm. The average reflectance is a value obtained by measuring the reflectance at each wavelength at intervals of 1nm and dividing the total value of the reflectances by the number of measurements. The evaluation a is performed when the average reflectance is 0.5% or less and no pulsation is present, the evaluation B is performed when the average reflectance is 1.0% or less and relatively weak pulsation is present, the evaluation C is performed when the average reflectance is 1.0% or less and relatively strong pulsation is present, and the evaluation D is performed when the average reflectance is greater than 1.0%. The self-cleaning effect was evaluated by performing the above-described WAX test 10 times and adjusting the contact angle with water of the surface 4a of the film 4 according to the reflectance after the irradiation of ultraviolet light.

The results of the evaluation of the reflectance characteristics and the self-cleaning effect are shown in table 4.

[ Table 4]

As shown in table 4, in the optical member of experimental example 4 in which the total thickness of the reflectance adjustment film 4 was 315nm, the interface 5a of the photocatalytic film 5 on the reflectance adjustment film 4 side was disposed at a position of 315nm deeper than 150nm from the surface 4a of the reflectance adjustment film 4. In this case, the transport of oxygen radicals generated in the photocatalytic film 5 to the surface 4a is hindered, and the self-cleaning effect is reduced. As a result, the contact angle of the surface 4a was 22.4 °. In addition, in the optical member of experimental example 5 in which the thickness of the photocatalytic film 5 was 200nm, the self-cleaning effect was reduced due to insufficient oxygen radicals generated in the photocatalytic film 5. As a result, the contact angle of the surface 4a was 15.2 °. The reflectance adjusting film 4 is formed of only SiO₂The optical member of experimental example 8 having the layer 110 of (1) had an average reflectance of 1.3% in a wavelength range of 400 to 700nm, and was not practically used as an antireflection film. On the other hand, in the optical members of experimental examples 1 to 3, 6 and 7 in which the total thickness of the reflectance adjustment film 4 is 20nm or more and less than 150nm, the interface 5a of the photocatalytic film 5 is disposed at a position of 150nm or less from the surface 4a, and the thickness of the photocatalytic film 5 is 350nm or more and 1000nm or less, the average reflectance in the wavelength range of 400 to 700nm is 1.0% or less, and the optical members have practical applicability as an antireflection film. Further, the contact angle of the surface 4a is 5 ° or less, and the hydrophilicity of the surface 4a is maintained by the self-cleaning action.

In particular, in the optical members of experimental examples 1 to 3 in which the photocatalytic film 5 has a thickness of 350nm to 500nm, the average reflectance in the wavelength range of 400 to 700nm is 0.5% or less and the reflectance characteristic curve in the wavelength range of 400 to 700nm is a flat curve without pulsation. From the above results, the thickness of the photocatalytic film 5 is preferably 350nm or more and 500nm or less, whereby the reflectance characteristics of the antireflection film 3 can be improved.

<TiO of photocatalytic film₂Crystal structure and self-cleaning action>

The optical members of experimental examples 9 to 11 all had the same configuration as the optical member of experimental example 2. However, contains TiO₂Of a single layerThe conditions for forming the photocatalytic film 5 were different for each experimental example, and in the optical member of experimental example 9, the temperature of the optical substrate 2 was set to 350 ℃ and the amount of oxygen introduced was set to 100 × 1.69 × 10^-3Pa·m³And/sec, film formation was performed by electron beam evaporation. In the optical member of experimental example 10, the temperature of the optical substrate 2 was set to 400 ℃ and the amount of oxygen introduced was set to 100 × 1.69 × 10^-3Pa·m³And/sec, film formation was performed by electron beam evaporation. In the optical member of experimental example 11, the temperature of the optical substrate 2 was set to 200 ℃ and the amount of oxygen introduced was set to 100 × 1.69 × 10^{- 3}Pa·m³And/sec, film formation was performed by electron beam evaporation. The TiO contained in the photocatalytic film 5 thus formed was measured by XRD₂As a result of analysis of the crystal structure of (a), the optical member of experimental example 9 was of an anatase structure, the optical member of experimental example 10 was of a rutile structure, and the optical member of experimental example 11 was of an amorphous structure. The WAX test was performed 10 times on the optical members of experimental examples 9 to 11, and the contact angle of the surface 4a of the reflectance adjusting film 4 with water after the ultraviolet irradiation was evaluated for TiO₂Correlation of crystal structure with self-cleaning action.

Adding TiO into the mixture₂The evaluation results of the correlation of the crystal structure with the self-cleaning effect are shown in table 5.

[ Table 5]

As shown in Table 5, the photocatalytic film 5 contained rutile-structured TiO₂In the optical member of experimental example 10, the contact angle of the surface 4a of the reflectance adjustment film 4 was 30 °, and the photocatalytic film 5 included TiO having an amorphous structure₂In the optical member of experimental example 11, the contact angle of the surface 4a of the reflectance adjusting film 4 was 50 °, whereas the photocatalytic film 5 included TiO having an anatase structure₂In the optical member of experimental example 9, the contact angle of the surface 4a of the reflectance adjustment film 4 was 4.8 °, and the hydrophilicity of the surface 4a was maintained by the self-cleaning action. According to the above knotPreferably, TiO contained in the photocatalytic film 5₂The crystal structure of (a) is an anatase structure, whereby the photocatalytic activity of the photocatalytic film 5 can be improved to enhance the self-cleaning action.

< doping and self-cleaning action on photocatalytic film >

The optical members of experimental examples 12 to 14 all had the same configuration as the optical member of experimental example 2. However, in the presence of TiO₂The single-layer photocatalytic film 5 of (a) was doped with different elements in each experimental example, N (nitrogen) was doped in the optical member of experimental example 12, Cr (chromium) was doped in the optical member of experimental example 13, and Ce (cerium) was doped in the optical member of experimental example 14. The optical members of experimental examples 12 to 14 were subjected to the above-described WAX test 10 times, and the correlation between the doping element and the self-cleaning effect was evaluated from the contact angle with water of the surface 4a of the reflectance adjustment film 4 after the ultraviolet irradiation.

The evaluation results of the correlation between the doping element and the self-cleaning effect are shown in table 6.

[ Table 6]

As shown in table 6, the optical member of experimental example 12 doped with N, the optical member of experimental example 13 doped with Cr, and the optical member of experimental example 14 doped with Ce all had smaller average reflectance in the wavelength range of 400 to 700nm and smaller contact angle of the surface 4a of the reflectance adjustment film 4 than the optical member of experimental example 2. From the above results, TiO contained in the photocatalytic film 5 can be contained₂N, Cr and Ce are doped, and the photocatalytic activity of the photocatalytic film 5 can be improved by doping the elements to enhance the self-cleaning effect. In addition, when S (sulfur) is doped, TiO is considered to be doped similarly to the case of N₂A part of the oxygen ions of (2) is replaced with S ions to improve the photocatalytic activity of the photocatalytic film 5, and when Sb (antimony) is doped, a part of the Ti ions is replaced with Ti ions as in the case of doping Cr and CeThe photocatalytic activity of the photocatalytic film 5 is also improved by the Sb ions.

< self-cleaning action of multilayer photocatalytic film >

In the optical members of experimental examples 15 to 17, the photocatalytic film 5 and the reflectance adjusting film 4 were formed on the optical substrate 2 in this order, and the optical member was formed from the optical substrate 2 side containing TiO in this order₂The photocatalytically active layer 14 of (1), comprising SiO₂And an intermediate layer 15 comprising TiO₂The photocatalytically active layer 14 of (2) constitutes the photocatalytic film 5 and is secondarily composed of a material containing SiO from the side of the optical substrate 2₂Layer 1 of (2), containing TiO₂And layer 2 of (1) and comprising SiO₂The 3 rd layer 12 of (b) constitutes the reflectance adjusting film 4. However, the photocatalytic film 5 contains SiO₂The film thickness of the intermediate layer 15 (a) was varied for each experimental example, and was set to 1nm for the optical member of experimental example 15, 2nm for the optical member of experimental example 16, and 3nm for the optical member of experimental example 17.

In the optical members of experimental examples 15 to 17, a white plate glass (manufactured by FD110 HOYA) was used in common as the optical substrate 2. And, comprises TiO₂The 1 st photocatalytic layer 14 and the 2 nd photocatalytic layer 14 are formed using Ti₃O₅As a vapor deposition material, the temperature of the optical substrate 2 was 350 ℃ and the amount of oxygen introduced was 100X 1.69X 10^-3Pa·m³And/sec, film formation was performed by electron beam evaporation. And, comprises SiO₂The intermediate layer 15 of (2) is formed of SiO₂As a vapor deposition material, film formation was performed by electron beam vapor deposition with the temperature of the optical substrate 2 set to 350 ℃ and the amount of oxygen introduced set to 0. The photocatalytic film 5 formed on the optical substrate 2 was annealed in air at an annealing temperature of 350 ℃ for 4 hours. And, the reflectance adjusting film 4 contains TiO₂The 2 nd layer 11 of (2) is formed by using Ti₃O₅As a vapor deposition material, the temperature of the optical substrate 2 was 350 ℃ and the amount of oxygen introduced was 100X 1.69X 10^-3Pa·m³And/sec, film formation was performed by electron beam evaporation. SiO is contained in the reflectance adjusting film 4₂The 1 st layer 10, the 3 rd layer 12 and the surface layer 13 of (A) are formed of SiO₂As a vapor deposition material, film formation was performed by electron beam vapor deposition with the temperature of the optical substrate 2 set to 350 ℃ and the amount of oxygen introduced set to 0.

The optical members of experimental examples 15 to 17 were subjected to the above-described WAX test 10 times, and the correlation between the thickness of the intermediate layer 15 of the photocatalytic film 5 and the self-cleaning effect was evaluated from the contact angle with water of the surface 4a of the reflectance adjustment film 4 after the irradiation with ultraviolet light.

The evaluation results of the correlation between the thickness of the intermediate layer 15 and the self-cleaning effect are shown in table 7.

[ Table 7]

As shown in table 7, each of the optical members of experimental examples 15 to 17 and the photocatalytic film 5 of the optical member of experimental example 2 was substantially the same except for whether or not the photocatalytic film 5 was divided into two photocatalytic active layers 14 through the intermediate layer 15. The average reflectance of each of the optical members of experimental examples 15 to 17 at a wavelength of 400 to 700nm was 0.5% or less as in the optical member of experimental example 2, and the contact angle of the surface 4a of the reflectance adjustment film 4 of each of the optical members of experimental examples 15 to 17 was 4.8 ° as in the optical member of experimental example 2. From the above results, it is understood that the photocatalytic film 5 may include two photocatalytically active layers 14 through the intermediate layer 15.

As described above, the antireflection film disclosed in the present specification is an antireflection film provided on an optical substrate, and includes: a reflectance control film including a 1 st layer, a 2 nd layer disposed on a surface side of the antireflection film with respect to the 1 st layer and having a higher refractive index than the 1 st layer, and a 3 rd layer disposed on the surface side with respect to the 2 nd layer and having a lower refractive index than the 2 nd layer, and having a thickness of 20nm or more and less than 150nm from the surface; and a photocatalytic film including one or more photocatalytically active layers containing titanium dioxide, the photocatalytic film being provided between the reflectance control film and the optical substrate, and an interface on the reflectance control film side being disposed at a position of 150nm or less from the surface, and the total thickness of the photocatalytically active layers being 350nm or more and 1000nm or less.

In the antireflection film disclosed in the present specification, the total thickness of the photocatalytic active layers is 350nm to 500 nm.

In the antireflection film disclosed in the present specification, the photocatalytic active layer included in the photocatalytic film is a single layer.

In the antireflection film disclosed in the present specification, the crystal structure of titanium dioxide contained in the photocatalytically active layer is an anatase structure.

The antireflection film disclosed in the present specification is an antireflection film in which the photocatalytic active layer further contains at least one element selected from the group consisting of nitrogen, sulfur, chromium, antimony, and cerium.

In the antireflection film disclosed in the present specification, the 3 rd layer contains silica and forms the surface.

In the optical member disclosed in the present specification, the antireflection film is provided on an optical substrate.

In the optical member disclosed in the present specification, the optical substrate is a lens.

Industrial applicability

The present invention can be used for optical components such as a lens and a cover of an outdoor camera such as a monitoring camera and a vehicle-mounted camera.

The embodiments of the present invention have been described in detail, but these are merely examples, and the present invention can be implemented in various modified forms without departing from the spirit and scope thereof. The present application is based on the japanese patent application (japanese patent application 2017-079008) filed on 12/4/2017, the contents of which are incorporated herein by reference.

Description of the symbols

1-optical member, 2-optical substrate, 3-antireflection film, 4-reflectance adjusting film, 4 a-surface, 5-photocatalytic film, 5 a-interface, 10-1 st layer, 11-2 nd layer, 12-3 rd layer, 14-photocatalytic active layer, 15-intermediate layer.