TWI518356B - Optical device - Google Patents

Description

Optical device

The present invention relates to an optical device in which an antireflection film (AR film: Anti Reflection) is formed on a surface of a visible light transmissive substrate such as infrared absorbing glass. Furthermore, the refractive index referred to in this specification is the refractive index in the atmosphere.

The spectral sensitivity of a photographic element such as a CCD or a CMOS used in a digital camera or the like extends from a region of visible light to a region of infrared light. In the optical system directly in front of the photographic element, for example, an infrared absorbing glass is used as the visible light penetrating substrate, and the infrared light is absorbed by the infrared absorbing glass so that the photographic element can receive the visible light. The photographic image is approximated to the human visual sensation. Then, by forming an anti-reflection film on the surface of the visible light-transmitting substrate such as the infrared absorbing glass, the reflection loss of visible light is reduced, and the transmittance is improved.

In such an optical device in which the antireflection film is formed on the surface of the visible light-transmissive substrate, if the antireflection film is a single layer, the antireflection effect is not sufficient at any wavelength. Patent Document 1 also proposes a technique of an antireflection film composed of three layers having different refractive indices, and can prevent reflection of a spectrum of 400 nm to 700 nm as a whole in a visible light region.

Patent Document 1: Japanese Patent Laid-Open No. 5-2101

However, the environment in which the camera is used also has a high temperature and high humidity environment, and the assembly is here. The optical device of the camera optical system is expected to have no optical damage in an environment of high temperature and high humidity. The present inventors conducted an experiment in which an optical device was placed in a high-temperature and high-humidity environment for a long period of time. As a result, after the test, the optical device having a good visible light transmittance before the test, the moisture intruded into the inside of the substrate, and the substrate was dissolved to cause light scattering, thereby occurring. The overall appearance is white and cloudy, and the transmittance of visible light is extremely lowered. Therefore, the inventors of the present invention completed the present invention by conducting an effort to study the cause of the above-mentioned white turbidity phenomenon.

That is, the present invention has been made in view of the above circumstances, and an object thereof is to provide an optical device which is provided with an antireflection composed of a plurality of laminated films having different refractive indices on a surface of a visible light transmitting substrate such as an infrared absorbing glass. The film-formed optical device can prevent the occurrence of the above-mentioned white turbidity phenomenon even when placed in a high-temperature and high-humidity environment for a long time, and the penetration property is maintained as in the case of the test, and the weather resistance is excellent.

(1) In order to achieve the above object, the optical device of the present invention is provided with an antireflection film for preventing visible light reflection on at least one surface of a visible light transmissive substrate, wherein the antireflection film has a refractive index different from each other. The refractive index layer of two or more layers is formed, and at least one or more refractive index layers other than the refractive index layer having a low refractive index among the at least two or more refractive index layers contain at least Al ₂ O ₃ or ZrO. ₂ or a mixture of the materials as the material thereof, and the average particle diameter of the particles above the anti-reflection film is less than 25 nm.

The antireflection film may be provided on one surface of the visible light transmissive substrate or may be provided on both sides, and any of the cases may be included in the present invention. The film formation method of the antireflection film is not limited, and it is preferably formed by a physical vapor deposition method such as a vacuum deposition method. As long as the average particle diameter of the particles on the upper surface of the antireflection film is less than 25 nm, any average particle diameter may be sufficient, and the average particle diameter may be appropriately selected.

In the present invention, since the average particle diameter of the particles on the upper surface of the anti-reflection film is less than 25 nm, it is possible to prevent moisture from easily immersing in the anti-reflection film even when placed in a high-temperature and high-humidity environment for a long time, and as a result, it is prevented. In the case of white turbidity, the penetration of visible light can be maintained. When the optical device of the present invention is disposed directly in front of the camera imaging element, it is possible to provide a camera capable of maintaining a good photographic image for a long period of time and having excellent weather resistance.

In addition, the visible light transmissive substrate is not particularly limited as long as it can penetrate visible light.

(2) The preferred embodiment of the above (1) of the present invention is characterized in that at least two or more refractive index layer layers having different refractive indices are formed on the surface of the visible light-transmitting substrate, and at least from visible light The refractive index layer of the first layer from the penetrating substrate contains at least Al ₂ O ₃ or ZrO ₂ or a mixture thereof as its material.

In this case, the material of the refractive index layer of the first layer is at least composed of at least Al ₂ O ₃ or ZrO ₂ or a mixture thereof from at least the visible light-transmitting substrate, and the refractive index is in the range of 1.6 to 1.7. The range of Al ₂ O ₃ is formed as a medium refractive index layer, or ZrO ₂ having a refractive index in the range of 2.0 to 2.4 is formed into a high refractive index layer, so that there is an advantage that it is easy to design an antireflection film composed of a plurality of layers. . As a result, the spectral characteristics of the entire visible light region having an antireflection effect can be obtained. However, if at least the material of the refractive index layer of the first layer from the visible light-permeable substrate contains at least Al ₂ O ₃ or ZrO ₂ or a mixture of the above, when the moisture is immersed, there is a possibility that the substrate is easily dissolved. The past problems will be more likely to occur significantly. With this configuration, in combination with the above configuration, it is possible to prevent moisture from easily entering the antireflection film and to prevent white turbidity, and to maintain the visibility of visible light.

(3) The preferred embodiment of the above (1) of the present invention is as follows: The material of the light-transmitting substrate is a fluorophosphate-based glass containing copper ions or a phosphate-based glass.

In this case, when the material of the visible light-transmissive substrate is a fluorophosphate-based glass containing copper ions or a phosphate-based glass, the photographic element can be exposed to visible light in a state where the infrared absorbing effect is high, and the photographic image can be made. It approximates the human visual sensitivity. Moreover, the cause of the ghost and the flare can be reduced. However, when the material of the visible light-transmissive substrate is a fluorophosphate-based glass containing copper ions or a phosphate-based glass, dissolution may occur when moisture is immersed, and the conventional problem is more likely to occur remarkably. With this configuration, in combination with the above configuration, it is possible to prevent moisture from easily entering the antireflection film and to prevent white turbidity, and to maintain the visibility of visible light.

The optical device of the present invention can prevent the occurrence of white turbidity even when left in an environment of high temperature and high humidity for a long period of time, so that the weather resistance of the initial optical characteristics can be maintained for a long period of time.

1,1a,1b,1c‧‧‧optical devices

2‧‧‧Infrared absorption glass

3‧‧‧Anti-reflective film

3a‧‧‧The first layer of the refractive index layer

3b‧‧‧2nd layer of high refractive index layer

3c‧‧‧Layer 3 low refractive index layer

3d‧‧‧1st layer of high refractive index layer

3e‧‧‧2nd layer of low refractive index layer

3f‧‧‧The first layer of the refractive index layer

3g‧‧‧2nd layer of low refractive index layer

3h‧‧‧1st layer of high refractive index layer

3i‧‧‧2nd layer of low refractive index layer

3j‧‧‧3rd layer of high refractive index layer

3k‧‧‧4th layer of low refractive index layer

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a cross-sectional view showing an optical device according to an embodiment of the present invention.

Fig. 2 is a graph showing the wavelength versus reflectance characteristics of the above optical device.

Fig. 3(a) is a schematic view showing the state of the particles on the surface of the comparative example, and Fig. 3(b) is a schematic view showing the state of the particles on the surface of the embodiment.

Figure 4 is a cross-sectional view showing an optical device according to another embodiment of the present invention.

Figure 5 is a cross-sectional view showing an optical device according to still another embodiment of the present invention.

Figure 6 is a cross-sectional view showing an optical device according to still another embodiment of the present invention.

Figure 7 (a) shows the particles on the anti-reflection film in an optical device fabricated at an appropriate temperature. The SEM image (scanning electron microscope image) of the state and FIG. 7(b) show the SEM image of the particle state on the surface of the antireflection film in the optical device manufactured by the temperature.

Fig. 8(a) is a photograph taken from the side opposite to the light irradiation surface before and after the high temperature and high humidity test in the comparative example, and Fig. 8(b) is the opposite to the light irradiation surface before and after the high temperature and high humidity test in the embodiment. Photographs taken on the side.

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a cross-sectional view showing an optical device according to an embodiment of the present invention. Referring to Fig. 1, an optical device 1 includes an infrared absorbing glass 2 and an antireflection film 3 provided on a surface of the infrared absorbing glass 2.

In the case of the infrared absorbing glass 2, as long as it is a light-transmitting substrate, as long as it transmits visible light and absorbs infrared light, it is not particularly limited to the glass material, but a fluorophosphate containing copper ions is exemplified. Glass or phosphate glass containing copper ions.

The antireflection film 3 is composed of a laminated film which is formed on the surface of the infrared absorbing glass 2, and is formed by laminating the first layer, the second layer, and the third layer in three layers.

In the anti-reflection film 3, the first layer is the medium refractive index layer 3a having a refractive index of the middle of the three layers from the infrared absorbing glass 2, and the second layer is the above three layers from the infrared absorbing glass 2. The highest layer in the middle, that is, the high refractive index layer 3b, the third layer from the infrared absorbing glass 2 is a low refractive index layer 3c having a refractive index of the lowest of the above three layers.

In the first layer, the refractive index layer 3a has a refractive index of 1.6 to 1.7 and an optical film thickness of about 1/4 λ (where λ is a wavelength of about 520 nm, the same applies hereinafter), and contains Al _{2 .} At least one of O ₃ , ZrO ₂ , a mixture of Al ₂ O ₃ and ZrO ₂ is used as the material.

The second layer of the high refractive index layer 3b is a refractive index layer having a refractive index of 2.0 to 2.4 and an optical film thickness of about 1/2 λ, and contains a mixture of Al ₂ O ₃ , ZrO ₂ , Al ₂ O ₃ and ZrO ₂ . At least one of them is used as a material.

The third layer of the low refractive index layer 3c is a refractive index layer having a refractive index of 1.5 or less and an optical film thickness of about 1/4 λ, and is made of MgF ₂ or another material.

In the optical device 1 of such a configuration, as illustrated in FIG. 2, the reflectance in the visible light wavelength region of 400 to 700 nm is 1% or less. However, the range of this wavelength region varies from person to person, and is exemplified as an example. That is, the human eye responds to light in the range of about 400 to 620 nm in the dark, and responds to light in the range of about 420 to 700 nm in the bright place. On the other hand, a general camera photographic element (CCD) responds with high sensitivity to light in the range of 400 to 700 nm, and thus to light of wavelengths less than 400 nm or wavelengths of more than 700 nm (infrared). Will answer. Therefore, if the reflectance of the visible light wavelength region of 400 to 700 nm is set to 1% or less as shown in FIG. 2 so that the optical device 1 is disposed in the optical system directly in front of the image pickup element, the infrared light is absorbed by the optical device 1 without Will reach the photographic element. On the other hand, since visible light can reach the photographic element with high transmittance, a good photographic image close to the human eye can be obtained.

In the embodiment, the average particle diameter of the particles above the anti-reflection film 3 is less than 25 nm. If the average particle diameter of the particles is extremely small, the gap area between the particles on the upper surface of the anti-reflection film 3 becomes small. Therefore, even if it is left for a long time in a high-temperature and high-humidity environment, moisture does not easily enter the inside of the anti-reflection film 3. Effectively prevent the occurrence of white turbidity.

If the average particle diameter of the particles above the anti-reflection film 3 is 24 nm, the haze value When it is 0.3, the average particle diameter is preferably 24 nm or less, and if the average particle diameter is 21 nm, the haze value is less than 0.2, so the average particle diameter is preferably 21 nm or less.

In addition, the particle diameter is a value measured by an arithmetic biaxial average diameter ((long side + short side)/2) for each particle, and the average particle diameter is the particle diameter measured by 50 or more particles. The average winner.

The method of measuring the particle diameter is performed by measuring the long side and the short side length of 50 or more particles in a specific region obtained by the SEM image of the upper surface of the anti-reflection film 3.

Moreover, the upper surface of the anti-reflection film 3 means the surface of the anti-reflection film 3 which is connected to the atmosphere.

In this case, the state of the upper surface of each of the conventional anti-reflection films of the embodiment will be described with reference to Fig. 3, that is, Fig. 3(a) shows the state of the upper surface of the conventional antireflection film, and Fig. 3(b) shows the implementation. The state above the antireflective film of the type. In the conventional case, each of the particles 4a on the antireflection film has various diameters. Since the average particle diameter of the particles 4a is 25 nm or more, the area of the gap 5a between the respective particles 4a is schematically shown in Fig. 3(a). When it is left standing for a long period of time under high temperature and high humidity, moisture easily immerses into the inside of the antireflection film 3 from the gap 5a between the respective particles 4a on the upper surface of the antireflection film, and white turbidity occurs.

On the other hand, in the embodiment, the particles 4b on the upper surface of the anti-reflection film 3 have various sizes, but since the average particle diameter of the particles 4b is less than 25 nm, as shown schematically in Fig. 3(b), The gap area between the respective particles 4b on the anti-reflection film 3 is small, and even if it is left standing for a long time under high temperature and high humidity, moisture does not easily enter the inside of the anti-reflection film 3 from the upper surface of the anti-reflection film 3. Therefore, moisture is not easily immersed in the boundary of the respective refractive index layers 3a to 3c constituting the anti-reflection film 3, or the boundary between the anti-reflection film 3 and the infrared absorbing glass 2 is effective for a long period of time. To prevent the occurrence of white turbidity.

Figure 4 is a cross-sectional view of an optical device of another embodiment. In this embodiment, the antireflection film 3 is composed of a total of two layers of the high refractive index layer 3d of the first layer and the low refractive index layer 3e of the second layer from the infrared absorbing glass 2 from the infrared absorbing glass 2.

The first layer of the high refractive index layer 3d is a refractive index layer having a refractive index of 2.0 to 2.4 and an optical film thickness of about 1/2 λ, and contains a mixture of Al ₂ O ₃ , ZrO ₂ , Al ₂ O ₃ and ZrO ₂ . At least one of them is used as a material.

The second layer of the low refractive index layer 3e is a refractive index layer having a refractive index of 1.5 or less and an optical film thickness of about 1/4 λ, and is composed of MgF ₂ or another material.

Also in the case of this embodiment, the average particle diameter of the surface of the anti-reflection film 3 is less than 25 nm, and the area between the particles on the surface of the anti-reflection film becomes small, even in a high-temperature and high-humidity environment. It is not easy to be immersed in the interior of the anti-reflection film 3 to prevent the occurrence of white turbidity.

Figure 5 is a cross-sectional view of another embodiment of an optical device. In this embodiment, the antireflection film 3 is composed of two layers of the refractive index layer 3f in the first layer and the low refractive index layer 3g in the second layer from the infrared absorbing glass 2 from the infrared absorbing glass 2.

In the first layer, the refractive index layer 3f is a refractive index layer having a refractive index in the range of 1.6 to 1.7 and an optical film thickness of 1/4 λ to 1/2 λ, and contains Al ₂ O ₃ , ZrO ₂ , and Al _{2 .} At least any one of a mixture of O ₃ and ZrO ₂ .

The second layer of the low refractive index layer 3g is a refractive index layer having a refractive index of 1.5 or less and an optical film thickness of about 1/4 λ, and is composed of MgF ₂ or another material.

Also in the case of this embodiment, the average particle diameter of the surface of the anti-reflection film 3 is less than 25 nm, and the area of the gap between the particles above the anti-reflection film 3 becomes small, even at a high temperature. In the high-humidity environment, moisture is also less likely to be immersed in the interior of the anti-reflection film 3, preventing the occurrence of white turbidity.

Fig. 6 is a cross-sectional view showing another embodiment of the optical device 1c. In this embodiment, when the anti-reflection film 3 is formed by the infrared absorbing glass 2, the odd-numbered layer is a high-refractive-index layer, and the even-numbered layer is a low-refractive-index layer, and n(n=1, 2, 3, In the case of the antireflection film of the layer 4, the high refractive index layer 3h of the first layer, the low refractive index layer 3i of the second layer, and the high refractive layer of the third layer are obtained from the infrared absorbing glass 2 as an example. The ratio layer 3j and the fourth layer of the low refractive index layer 3k are composed of a total of four layers.

The first layer of the high refractive index layer 3h is a refractive index layer having a refractive index of 2.0 to 2.4 and an optical film thickness of about 0.13 λ, and contains a mixture of Al ₂ O ₃ , ZrO ₂ , Al ₂ O ₃ and ZrO ₂ . At least any one is used as a material.

The second layer of the low refractive index layer 3i is a refractive index layer having a refractive index of 1.5 or less and an optical film thickness of about 0.08 λ, and is made of MgF ₂ , SiO ₂ or another material.

The third layer of the high refractive index layer 3j is a refractive index layer having a refractive index of 2.0 to 2.4 and an optical film thickness of about 0.16 λ, and is composed of ZrO ₂ , TiO ₂ , and other materials.

The fourth layer of the low refractive index layer 3k has a refractive index of 1.5 or less and an optical film thickness of about 0.25 λ, and is made of MgF ₂ , SiO ₂ or another material.

Also in the case of this embodiment, the average particle diameter of the particles on the surface of the anti-reflection film 3 is less than 25 nm, and the area of the gap between the particles on the anti-reflection film 3 becomes small, even in a high-temperature and high-humidity environment. It is not easy to be immersed in the interior of the anti-reflection film 3 to prevent the occurrence of white turbidity.

(Example) <Method of Manufacturing Optical Device>

The optical device of the embodiment is composed of an infrared absorbing glass and an antireflection film, and the antireflection film is composed of a three-layer laminated film (refractive index layer) as in Fig. 1 . In the infrared absorbing glass, a fluorophosphate glass containing a copper ion having a cross-sectional dimension of about 20 mm × 30 mm in length and a thickness of about 0.30 mm and a refractive index of 1.56 and containing copper ions was used.

The first layer to the third layer constituting the antireflection film have the same plan view as the infrared absorbing glass, and the first layer has a refractive index layer of Al ₂ O ₃ and ZrO ₂ having a refractive index of 1.70 and an optical film thickness of 1/4 λ. The composition of the mixture. The second layer of the high refractive index layer is composed of ZrO ₂ having a refractive index of 2.10 and an optical film thickness of 1/2 λ. The low refractive index layer of the third layer is composed of MgF ₂ having a refractive index of 1.38 and an optical film thickness of 1/4 λ.

A method of forming each layer will be described. That is, the washed infrared absorbing glass is placed in a vacuum vapor deposition apparatus, and after vacuum evacuation, vacuum evaporation is started to form a film of each layer. The temperature of the infrared absorbing glass at the time of vacuum vapor deposition is arbitrarily changed. The optical film thickness of each layer is performed by controlling the reflectance on the monitor glass based on the optical film thickness monitoring method. Further, the haze value (turbidity) was measured in accordance with JIS 7136 before and after the high temperature and high humidity test.

The temperature shown in Table 1 is the temperature of the infrared absorbing glass at the time of vacuum vapor deposition in the film-forming antireflection film. In Table 1, "low ← temperature → high", "low ←" means the temperature is in the direction of the arrow. Lower, "→High" is the table temperature rising in the direction of the arrow. Similarly, Table 1 The haze value shown is the value measured by JIS 7136, which is obtained by digitizing the optical turbidity phenomenon of the optical device after the high temperature and high humidity test. In general, a blur degree of fog value of 0.3 or less is regarded as an allowable range in a photographic image of a camera, and a blur degree of a fog value of 0.2 or less is regarded as a range having no influence in a photographic image of a camera. Further, in Table 1, (1)-(3) indicates an appropriate temperature, and (4) and (5) indicate an allowable temperature, (6), (7) in terms of particle diameter and haze value on the upper surface of the antireflection film. Indicates that the temperature is exceeded, for example, above 300 °C.

At any suitable temperature (1), (2), and (3), the average particle diameter of the particles above the antireflection film is 16 nm, 17 nm, and 21 nm, respectively, and the gap area between the particles becomes small. The fog values were 0.11, 0.09, and 0.16, respectively, and no white turbidity occurred.

Further, in terms of allowable temperatures (4) and (5), the average particle diameter of the particles above the antireflection film is 22 nm and 24 nm, respectively, and the gap area between the particles is larger than the above-mentioned appropriate temperatures (1), (2), and (3). )Case. Further, the haze values were 0.20 and 0.30, respectively, although the white turbidity phenomenon was confirmed to be slight, but it was acceptable.

Further, in the case of exceeding the temperatures (6) and (7), the average particle diameter of the particles on the upper surface of the antireflection film is 25 nm and 30 nm, respectively, and the gap area between the respective particles is increased. Further, the fog values were 0.37 and 0.66, respectively, and the white turbidity phenomenon was clearly confirmed.

That is, when the average particle diameter of the particles is less than 25 nm, the gap area between the particles becomes small, so the haze value after the high-temperature and high-humidity test is small. That is, almost no white turbidity of the optical device occurs.

The average particle diameter of the particles above the antireflection film of the manufactured optical device was 17 nm and 30 nm, and the SEM images of the respective SEM images are shown in Fig. 7. Fig. 7(a) shows the surface state of an optical device in which an antireflection film is formed on an infrared absorbing glass at an appropriate temperature. Figure 7 (b) shows the surface state of the optical device in which the antireflection film is formed on the infrared absorbing glass beyond the temperature.

When these SEM images are compared, it is understood that when the antireflection film is formed at an appropriate temperature as shown in Fig. 7(a), the average particle diameter of the particles on the upper surface of the antireflection film is reduced to 17 nm, and the antireflection film is used. The area of the gap between the above particles becomes small. On the other hand, when the antireflection film is formed at a temperature exceeding the temperature as shown in Fig. 7(b), the average particle diameter of the particles on the upper surface of the antireflection film is increased to 30 nm, and the interparticle gaps on the upper surface of the antireflection film are obtained. The area becomes larger.

Fig. 8 (a) and (b) are photographs showing the state of occurrence of white turbidity before and after the high temperature and high humidity test of the comparative examples and the examples. Fig. 8(a) shows a comparative optical device which was produced at a temperature exceeding the average particle diameter of the particles of 30 nm, and Fig. 8(b) is an example optical device which was produced at an appropriate temperature and had an average particle diameter of 17 nm. In Fig. 8 (a) and (b), the left side is after the high temperature and high humidity test, and the right side is before the high temperature and high humidity test. The optical device can penetrate light from the back.

The comparative example shown in Fig. 8(a) was explained, that is, as shown in the photograph on the right side of Fig. 8(a) before the high-temperature and high-humidity test, the light was substantially penetrated and was not scattered on the surface of the optical device, so that it was dark. However, after the high-temperature and high-humidity test, as shown in the photograph on the left side of Fig. 8(a), water permeates into the inside of the optical device, and as a result of partial dissolution of the substrate, it is understood that the entire space is white turbid due to light scattering due to the formation space.

On the other hand, the embodiment shown in FIG. 8( b ) is described, that is, as shown in the right photograph of FIG. 8( b ) before the high-temperature and high-humidity test, the light is substantially penetrated and not reflected on the surface of the optical device, so that it is presented. Darker. Further, it was found that after the high-temperature and high-humidity test, as shown in the photo on the left side of Fig. 8(b), the moisture did not permeate into the inside of the optical device, so that it was not cloudy and was transparent. That is, it is apparent that there is no change in light transmittance in the optical device before and after the high temperature and high humidity test.

As described above, the optical device of the embodiment has an average particle diameter of the particles on the anti-reflection film of less than 25 nm, so that white turbidity does not occur even in a high-temperature and high-humidity environment, and the performance as an optical device can be maintained for a long period of time. Excellent weather resistance.

Further, in the above-described embodiment, an antireflection film having three layers of a low refractive index layer, a medium refractive index layer, and a high refractive index layer, and a high refractive index layer and a low refractive index layer are used. a two-layer antireflection film, an antireflection film using two layers of a medium refractive index layer and a low refractive index layer, and an antireflection film using an n layer having a high refractive index layer and a low refractive index layer (in an embodiment) n=4), but the design of the antireflection film is not limited to these embodiments, and may be constituted by a combination of the respective refractive index layers and the number of layers which can obtain desired antireflection characteristics.

The present invention may be embodied in other various forms without departing from the spirit or essential characteristics thereof. Therefore, the above-described embodiments and examples are merely illustrative in all aspects, and the explanation is not limited. The scope of the present invention is expressed by the scope of the claims, and is not limited by the description herein. Further, all modifications and alterations belonging to the equivalent scope of the claims are within the scope of the invention.

1,1a,1b,1c‧‧‧optical devices

2‧‧‧Infrared absorption glass

3‧‧‧Anti-reflective film

3a‧‧‧The first layer of the refractive index layer

3b‧‧‧2nd layer of high refractive index layer

3c‧‧‧Layer 3 low refractive index layer

Claims (3)

An optical device having an antireflection film for preventing visible light reflection on at least one surface of a visible light transmissive substrate, wherein the antireflection film is a refractive index laminated layer having at least two or more layers having different refractive indices. In the refractive index layer of at least two or more layers, at least one layer or more other than the refractive index layer having a low refractive index contains at least Al ₂ O ₃ or ZrO ₂ or a mixture thereof as a material thereof, and the anti-drug The upper surface of the reflective film is composed of the refractive index layer having a low refractive index, and the upper surface is composed of particles having an average particle diameter of less than 25 nm. The optical device according to claim 1, wherein the refractive index layer having at least two or more layers having different refractive indices is formed on the surface of the visible light transmissive substrate, and at least from the visible light transmissive substrate The refractive index layer of the first layer at least contains Al ₂ O ₃ or ZrO ₂ or a mixture thereof as its material. The optical device according to claim 1 or 2, wherein the material of the visible light transmissive substrate is a fluorophosphate-based glass containing copper ions or a phosphate-based glass.