JP4690065B2 - Antireflection film and optical component - Google Patents

Description

  The present invention relates to an antireflection film suitably used for optical parts such as lenses and display panels, and an optical part including the antireflection film.

  In recent years, not only glass materials but also plastic materials excellent in weight reduction and cost reduction have been used as materials for optical components such as display panels and lenses. The plastic materials used for optical parts are diversifying, but most of them show a high refractive index of 1.45 to 1.70, which is similar to the refractive index of glass materials. The value is shown. Therefore, when these materials having a high refractive index are applied to a lens or the like, the reflectance of light increases, and this causes problems such as a decrease in the amount of transmitted light and reflection.

  Therefore, in order to prevent problems such as a decrease in the amount of transmitted light and reflection, usually, an antireflection film is formed by laminating a dielectric film on the surface of the optical component by sputtering or vacuum deposition. As an anti-reflection film, for example, as used in an optical pickup lens, anti-reflection characteristics are exhibited at a wavelength near 780 nm for CD (Compact Disk) and at a wavelength near 660 nm for DVD (Digital Versatile Disk). There is something to show.

  By the way, in the optical pickup lens, a technique for shortening the pickup wavelength is required to improve the recording density, and it is expected that many lenses using a wavelength band near 400 nm will be used in the future. . Therefore, from the viewpoint of compatibility and the like, an antireflection film that satisfies low reflectance characteristics in a shorter wavelength band than the conventionally used wavelength band in addition to the conventionally used wavelength band is desired. That is, an antireflection film capable of achieving a wide antireflection band is desired.

The following are proposed as an antireflection film for realizing a wide antireflection band. First, an antireflection film has been proposed in which thin films having a refractive index of 1.8 or more and thin films having a refractive index of 1.5 or less are alternately laminated, and the number of laminations is increased. Secondly, for example, an antireflection film has been proposed in which a single layer having a refractive index of 1.5 or less is formed on a plastic material optical component having a refractive index of 1.45 to 1.70. Thirdly, an antireflection film is proposed in which the entire antireflection film is composed of a SiO ₂ film having a refractive index of 1.3 to 1.4 (Patent Document 1). Fourthly, an antireflection film has been proposed in which several layers made of a fluororesin having a refractive index changed in the physical film thickness direction are stacked (Patent Document 2).
Japanese Patent Laid-Open No. 5-80202 Japanese Patent Laid-Open No. 10-227903

However, the antireflection film has the following problems. In the first antireflection film, the widening of the antireflection band is still insufficient. In addition, since the physical film thickness of the entire antireflection film is increased, the substrate may be deformed when a plastic material having low heat resistance is used as the optical substrate. This is because the time required for vapor deposition and sputtering increases because the physical film thickness of the entire antireflection film is increased, resulting in an increase in the substrate temperature.
The second antireflection film is advantageous for widening the wavelength band (the wavelength band can be increased as the refractive index of the film used is lower), but the reflectance is increased. There was a point.

The third antireflection film has a problem that it absorbs moisture from the outside air and causes a change in antireflection characteristics with time. This is due to the fact that the antireflection film is not dense but is formed with an inhomogeneous film quality. The cause is that the normal refractive index of SiO ₂ is 1.45 to 1.46, and the refractive index is set to 1.3 to 1.4 by controlling the incident angle of the vapor deposition material during film formation. I think that is because.
In the fourth antireflection film, it is necessary to continuously change the refractive index at the time of manufacture, and there are problems that manufacturing conditions are severe and it is difficult to provide an antireflection film having stable antireflection characteristics.

  The present invention has been made in view of the above-mentioned problems, and the object of the present invention is to provide an excellent antireflection characteristic while achieving a wide reflection band and to change the antireflection characteristic over time. An object of the present invention is to provide an antireflection film that can be suppressed and an optical component including the antireflection film.

  The inventors of the present invention have made extensive studies and found that the object can be achieved by setting the composition of the antireflection film in a composite manner, and have completed the present invention.

The antireflection film according to the first aspect of the present invention is an antireflection film in which at least two optical thin film layers having different refractive indexes are laminated on an optical substrate, and the optical thin film layer comprises magnesium fluoride. The optical thin film layer has a refractive index of 1.30 or more and 1.40 or less with respect to a wavelength of 600 nm, and the optical thin film layer has a refractive index of 1.30 or more and less than 1.35 with respect to a wavelength of 600 nm. And a layer having a refractive index of 1.35 or more and 1.40 or less with respect to a wavelength of 600 nm, and the refractive index of the outermost layer on which light is incident from the air surface of the optical thin film layer is 1 with respect to a wavelength of 600 nm. The layer having a refractive index of 1.35 or more and less than 1.35 is sandwiched between layers having the refractive index of 1.35 or more and 1.40 or less. is there.
In the following description, a layer having a refractive index in the range of 1.35 or more and 1.40 or less with respect to a wavelength of 600 nm is also referred to as a “high refractive index layer”.

According to the antireflection film of the first aspect of the present invention, the optical thin film layer is mainly composed of magnesium fluoride, and the refractive index is 1.30 nm or more and 1.40 nm or less with respect to a wavelength of 600 nm. Thus, it is possible to provide an antireflection film having excellent antireflection characteristics while achieving a wide antireflection band. Further, by setting the refractive index of the outermost layer to 1.35 or more with respect to a wavelength of 600 nm, it is possible to suppress the inside of the film from having a porous structure and to prevent water from being absorbed from the outside. As a result, it is possible to effectively suppress the temporal change of the antireflection characteristics. On the other hand, by setting the refractive index of the outermost layer to 1.40 or less with respect to the wavelength of 600 nm, it is possible to suppress an increase in the light absorptivity and to effectively prevent a decrease in the amount of transmitted light. A more preferable range of the refractive index of the outermost layer is 1.37 or more and 1,39 or less for a wavelength of 600 nm. Further, according to the configuration in which the layer having a refractive index of 1.30 or more and less than 1.35 is sandwiched between the layers having a refractive index of 1.35 or more and 1.40 or less, the low refractive index layer is provided inside the antireflection film. Therefore, the antireflection band can be more effectively widened. In addition, since the low refractive index layer is sandwiched between the high refractive index layers, the low refractive index layer that easily absorbs water can be protected by the high refractive index layer. As a result, it is possible to effectively suppress the occurrence of peeling and the generation of cracks and improve the mechanical strength.

The antireflection film according to the second aspect of the present invention is such that the refractive index of the lowermost layer in contact with the optical substrate in the optical thin film layer is 1.35 nm or more and 1.40 nm or less with respect to a wavelength of 600 nm. is there.
In the following description, a layer having a refractive index with respect to a wavelength of 600 nm in the range of 1.30 or more and less than 1.35 is also referred to as a “low refractive index layer”.

According to the antireflection film according to the second aspect of the present invention, by setting the refractive index of the lowermost layer of the optical thin film layer to 1.35 or more with respect to the wavelength of 600 nm, the inside of the film has a porous structure. It is possible to prevent the moisture inside the optical substrate from entering the optical thin film layer. Further, by setting the refractive index of the lowermost layer to 1.40 or less with respect to a wavelength of 600 nm, it is possible to suppress an increase in the light absorption rate and effectively prevent a decrease in the amount of transmitted light. In addition, it has an effect of increasing the adhesion between the optical substrate and the antireflection film. A more preferable range of the refractive index is 1.37 or more and 1,39 or less for a wavelength of 600 nm.

In the antireflection film according to the third aspect of the present invention, as the optical thin film layer, a layer having a refractive index with respect to a wavelength of 600 nm of 1.35 or more and 1.40 or less is a lowermost layer in contact with the outermost layer and the optical substrate. It is characterized by providing between. According to this configuration, since the high refractive index layer is provided in the inner layer of the antireflection film, an antireflection film having high film strength can be provided.

The antireflection film according to the fourth aspect of the present invention has a physical film thickness of the outermost layer of 5 nm or more and 300 nm or less. By setting the physical film thickness of the outermost layer to 5 nm or more, moisture in the outside air passes through the first layer and is absorbed by the second layer, resulting in a change in the refractive index of the film. It is possible to effectively suppress the change in optical characteristics over time. Further, by setting the thickness to 300 nm or less, it is possible to more effectively increase the antireflection band. A more preferable physical film thickness is 7 nm or more and 250 nm or less .

In the antireflection film according to the fifth aspect of the present invention, the physical film thickness of the lowermost layer is 2 nm or more and 300 nm or less. By setting the physical film thickness of the lowermost layer to 2 nm or more, moisture inside the optical substrate passes through the lowermost layer and is absorbed by the optical thin film layer (particularly, the low refractive index layer) laminated on the lowermost layer. Can be effectively suppressed. As a result, it is possible to prevent changes in optical characteristics over time. On the other hand, when the physical film thickness of the lowermost layer is 300 nm or less, it is possible to effectively achieve an increase in the antireflection band. A more preferable physical film thickness is 5 nm or more and 250 nm or less.

An optical component according to a sixth aspect of the present invention includes the antireflection film according to any one of the above aspects and an optical substrate. According to this aspect, it is possible to provide an optical component that is excellent in the antireflection characteristic while achieving a wide antireflection band and can suppress a change in the antireflection characteristic over time.

  According to the present invention, there is provided an antireflection film that is excellent in antireflection characteristics while achieving a wide antireflection band and that can suppress changes in antireflection characteristics over time, and an optical component including the antireflection film. There is an excellent effect that can be done.

  Hereinafter, an example of an embodiment to which the present invention is applied will be described. It goes without saying that other embodiments may also belong to the category of the present invention as long as they match the gist of the present invention.

FIG. 1 is a schematic cross-sectional view showing a configuration of an optical component according to this embodiment. An optical component 10 according to this embodiment includes an optical substrate 1 and an antireflection film 2. The antireflection film 2 is formed by laminating at least two optical thin film layers having different refractive indexes, each of which has magnesium fluoride (hereinafter abbreviated as “MgF ₂ ”) as a main component. Several layers of thin films are laminated, and the refractive index and physical film thickness of each layer are adjusted so as to satisfy desired optical characteristic conditions. The refractive index of the optical thin film layer with respect to a wavelength of 600 nm is set to be 1.30 or more and 1.40 or less. By doing so, it is possible to provide an antireflection film excellent in antireflection characteristics while achieving a wide antireflection band.

  The antireflection film 2 according to the present embodiment includes five optical thin film layers. Specifically, the optical thin film layer includes a first layer 3 (lowermost layer), a second layer 4, a third layer 5, a fourth layer 6, and a fifth layer 7 (outermost layer). FIG. 1 is a schematic diagram for explaining the present embodiment, and the physical film thickness and the like are different from actual sizes.

As the optical substrate 1, one made of amorphous glass, crystallized glass, plastic material, or other known materials can be used.
As the glass material, for example, a substrate made of oxide single crystal or oxide polycrystal such as LiNbO ₃ , LiTaO ₃ , TiO ₂ , SrTiO ₃ , Al ₂ O ₃ , MgO can be used. A single crystal or polycrystalline substrate made of a fluoride such as CaF ₂ , MgF ₂ BaF ₂ , or LiF may be used. Further, a single crystal or a polycrystalline substrate made of chloride or bromide such as NaCl, KBr, or KCl may be used.
As the plastic material, polymethacryl methacrylate (PMMA), polycarbonate (PC), polystyrene (PS), cyclic olefin resin, or the like can be used.

Hereinafter, the optical thin film layer according to the present embodiment will be described in detail.
The first layer 3 (lowermost layer) is a layer in contact with the optical substrate 1 and has a refractive index of 1.35 or more and 1.40 or less with respect to a wavelength of 600 nm (hereinafter referred to as a refractive index of 1.35 to 1 with respect to a wavelength of 600 nm). A layer in the range of .40 is also referred to as a “high refractive index layer”). By setting the refractive index of the lowermost layer of the optical thin film layer to 1.35 or more with respect to the wavelength of 600 nm, the inside of the film is prevented from having a porous structure, and moisture inside the optical substrate enters the optical thin film layer. Can be suppressed. Further, by setting the refractive index of the lowermost layer to 1.40 or less with respect to a wavelength of 600 nm, it is possible to suppress an increase in the light absorption rate and effectively prevent a decrease in the amount of transmitted light. In addition, it has an effect of increasing the adhesion between the optical substrate and the antireflection film. A more preferable range of the refractive index is 1.37 or more and 1,39 or less for a wavelength of 600 nm.
The physical film thickness was measured in the wavelength range of 400 to 800 nm using a spectroscopic ellipsometer. The refractive index was measured using a spectroscopic ellipsometer.

  The physical film thickness of the first layer 3 (lowermost layer) is preferably 2 nm or more and 300 nm or less. By setting the physical film thickness of the lowermost layer to 2 nm or more, moisture inside the optical substrate passes through the lowermost layer and is absorbed by the optical thin film layer (particularly, the low refractive index layer) laminated on the lowermost layer. Can be effectively suppressed. As a result, it is possible to prevent changes in optical characteristics over time. On the other hand, when the physical film thickness of the lowermost layer is 300 nm or less, it is possible to effectively achieve an increase in the antireflection band. A more preferable physical film thickness is 5 nm or more and 250 nm or less. In particular, when a plastic material that easily absorbs moisture is applied as the optical substrate 1, the effect is great. When a glass substrate that hardly absorbs moisture is used as the optical substrate 1, the high refractive index layer may not be provided.

The second layer 4 is a thin film made of MgF ₂ having a refractive index with respect to a wavelength of 600 nm of 1.30 or more and less than 1.35 (hereinafter, a layer having a refractive index in this range is also referred to as “low refractive index layer”). is there. By providing the low refractive index layer, the antireflection band can be expanded. The physical film thickness of the low refractive index layer is not particularly limited. However, as described above, when the physical film thickness is increased, the time required for vapor deposition or sputtering becomes longer, the substrate temperature rises, and the substrate is deformed. Therefore, it is determined in consideration of the substrate to be used, the required antireflection band, and the like. When used in the ultraviolet, visible, and infrared bands, the thickness is more preferably 300 nm or less from the viewpoint of antireflection properties.

The third layer 5 is a thin film made of MgF ₂ composed of a high refractive index layer having a refractive index with respect to a wavelength of 600 nm of 1.35 or more and 1.40 or less. Usually, the MgF ₂ film has a dense structure as the refractive index with respect to a wavelength of 600 nm is higher, and has a porous structure as the refractive index with respect to a wavelength of 600 nm is lower. Therefore, by using a high refractive index layer having a refractive index with respect to a wavelength of 600 nm of 1.35 or more and 1.40 or less as the intermediate layer, a dense structure can be formed in the intermediate layer and the mechanical strength of the film can be increased. it can. In order to effectively achieve the widening of the antireflection band, it is preferable that the third layer 5 has a physical film thickness that does not affect the antireflection effect.

The fourth layer 6 is an optical thin film layer made of MgF _{2 made} of a low refractive index layer having a refractive index with respect to a wavelength of 600 nm of 1.30 or more and less than 1.35. By providing the low refractive index layer, the antireflection band can be more effectively widened. Although the physical film thickness of the fourth layer 6 is not particularly limited, as described above, when the physical film thickness increases, the time required for vapor deposition and sputtering increases, and the substrate temperature rises and deformation of the substrate occurs. Therefore, it is determined in consideration of the substrate to be used, the required antireflection band, and the like. When used in the ultraviolet, visible, and infrared bands, the thickness is more preferably 300 nm or less from the viewpoint of antireflection properties.

The fifth layer 7 (outermost layer) is an optical thin film layer made of MgF ₂ composed of a high refractive index layer having a refractive index with respect to a wavelength of 600 nm of 1.35 or more and 1.40 or less. By setting the refractive index of the outermost layer to 1.35 or more with respect to a wavelength of 600 nm, it is possible to suppress the inside of the film from having a porous structure and to prevent water from being absorbed from the outside. As a result, it is possible to effectively suppress the temporal change of the antireflection characteristics. On the other hand, by setting the refractive index of the outermost layer to 1.40 or less with respect to the wavelength of 600 nm, it is possible to suppress the increase in the light absorption rate and effectively prevent the transmitted light amount from decreasing. it can. A more preferable range of the refractive index is 1.37 or more and 1,39 or less for a wavelength of 600 nm.

  The physical thickness of the fifth layer 7 (outermost layer) is preferably 5 nm or more and 300 nm or less. By setting the physical film thickness of the outermost layer to 5 nm or more, moisture in the outside air passes through the first layer and is absorbed by the second layer, resulting in a change in the refractive index of the film. It is possible to effectively suppress the change in optical characteristics over time. Further, by setting the thickness to 300 nm or less, it is possible to more effectively increase the antireflection band. A more preferable physical film thickness is 7 nm or more and 250 nm or less.

  In the present embodiment, the low refractive index layer is sandwiched between the high refractive index layers having strong film strength. By doing so, the low refractive index layer that easily absorbs moisture can be protected by the high refractive index layer. As a result, it is possible to effectively suppress the occurrence of peeling and the generation of cracks and improve the mechanical strength. In addition, it is possible to suppress an increase in microcracks that occur due to expansion of air and moisture inside the film in a high temperature environment.

  When the film strength is not required, when used in an environment where microcracks do not occur, or when used for applications where microcracks are not a problem, the third layer 5 that is the high refractive index layer is provided. It does not have to be.

Next, a method for manufacturing the antireflection film 2 will be described. The antireflection film 2 can be formed by a vacuum film forming method. Various film forming methods such as a vacuum deposition method, a sputtering method, a chemical vapor deposition method, and a laser brazing method can be used for the vacuum film forming method.
In the present embodiment, it is necessary to form a film that changes the refractive index of the optical thin film layer made of MgF ₂ . Usually, the film quality can be controlled by controlling the film forming conditions in the film forming method. When vacuum deposition is used, ion-assisted deposition that ionizes a part of the vapor flow and ion-biased to the substrate using an ion plating method, a cluster ion beam method, or an ion gun that simultaneously applies a bias to the substrate side Using this method is effective in controlling the film quality.
As the sputtering method, a DC reactive sputtering method, an RF sputtering method, an ion beam sputtering method, or the like can be used. Further, as the chemical vapor phase method, a plasma polymerization method, a light-assisted vapor phase method, a thermal decomposition method, a metal organic chemical vapor phase method, or the like can be used.

According to the anti-reflection film 2 according to the present embodiment, since it is composed of a single material mainly composed of MgF _2, excellent material, equipment, tact surface both. Therefore, cost reduction can be achieved. In addition, by using an antireflection film whose main component is MgF _{2 and} whose refractive index is in the range of 1.30 to 1.40 with respect to a wavelength of 600 nm, the antireflection band can be widened. it can. In addition, according to the present embodiment, it is possible to achieve a thin film without using a thick film like the first antireflection film described above as a conventional example, so that the deformation of the substrate particularly when a plastic material is used as an optical substrate. Etc. can be avoided.
The antireflection film 2 according to the present embodiment can be suitably used for, for example, a pickup lens for CD and DVD, a lens mounted on a mobile phone, a digital camera, and the like, but is not limited thereto, and is antireflection. It can be applied to all parts that require characteristics.

EXAMPLES Next, although an Example demonstrates this invention further more concretely, the scope of the present invention is not limited to the following example at all.
In addition, the physical film thickness and the refractive index measured the range of 400-800 nm using the spectroscopic ellipsometer (made by SOPRA). The reflectance was measured using a spectrophotometer (manufactured by Shimadzu Corporation) in the wavelength range of 350 to 800 nm.

Example 1 As the antireflection film according to Example 1, the configuration of the antireflection film 2 according to the above embodiment was used (see FIG. 1). As the optical substrate 1, a specific configuration of an optical thin film layer using a cyclic olefin-based resin substrate is as follows. That is, as the first layer 3 (lowermost layer), an MgF ₂ film having a physical film thickness of 3 nm and a refractive index of 1.38 with respect to a wavelength of 600 nm was laminated. The second layer 4 is an MgF ₂ layer having a physical film thickness of 43.7 nm and a refractive index of 1.30 with respect to a wavelength of 600 nm, and the third layer 5 is a physical film thickness of 3 nm and a refractive index of 600 nm. 1.38 MgF ₂ layers for, as a fourth layer 6, the physical film thickness the refractive index are laminated the MgF ₂ layers of 1.34 for the wavelength 600nm at 33.8Nm. The fifth layer 7 (outermost layer) was formed of an MgF ₂ layer having a physical film thickness of 10 nm and a refractive index of 1.38 with respect to a wavelength of 600 nm.

The high refractive index layers of the first layer 3, the third layer 5, and the fifth layer 7 were formed as follows using a vacuum evaporation apparatus. That is, MgF ₂ granules were used as the vapor deposition material, the degree of vacuum was 1.0 × 10 ⁻³ Pa, the introduction temperature was not used, and the substrate temperature at the start of film formation was 25 ° C. Film formation was performed at sec (that is, 10 Å / sec). Further, the low refractive index layers of the second layer 4 and the fourth layer 6 were made of MgF ₂ granules as a vapor deposition material, with a degree of vacuum of 1.5 × 10 ⁻² Pa, and with an introduced gas as Ar gas. Further, the film was formed under the condition that the amount of gas introduced was 50 sccm and the substrate temperature at the start of film formation was 25 ° C., and the deposition rate was 0.2 nm / sec (that is, 2 Å / sec).

Comparative Example 1 FIG. 2A is a schematic cross-sectional view illustrating a configuration of an optical component 100 according to Comparative Example 1. An antireflection film 102 is provided on the optical substrate 101. The antireflection film 102 has a two-layer structure including a first layer 103 and a second layer 104. The optical substrate 101 is made of a cyclic olefin-based resin substrate as in Example 1, and the first layer 103 is made of an MgF ₂ film having a physical film thickness of 94.9 nm and a refractive index of 1.30 with respect to a wavelength of 600 nm. Thus, the second layer 104 is made of an MgF ₂ film having a physical film thickness of 1 nm and a refractive index of 1.38 with respect to a wavelength of 600 nm. The optical component 100 is obtained by sequentially laminating the first layer 103 and the second layer 104 on the optical substrate 101 by the same method and conditions as in the first embodiment.

(Comparative example 2) FIG.2 (b) is a schematic sectional drawing which shows the structure of the optical component 200 which concerns on the comparative example 2. FIG. An antireflection film 202 is provided on the optical substrate 201. The antireflection film 202 has a two-layer structure including a first layer 203 and a second layer 204. The optical substrate 201 is made of a cyclic olefin resin substrate in the same manner as in Example 1, and the first layer 203 has a physical film thickness of 84.6 nm and a refractive index of MgF _{2 of} 1.30 with respect to a wavelength of 600 nm. The second layer 204 is made of a MgF ₂ film having a physical film thickness of 10.0 nm and a refractive index of 1.30 with respect to a wavelength of 600 nm. The optical component 200 is obtained by sequentially laminating the first layer 203 and the second layer 204 on the optical substrate 201. The first layer 203 was formed by the same method as the second layer 4 according to Example 1 described above. The second layer 204 is formed by using MgF ₂ granules as a deposition material, a vacuum degree of 1.1 × 10 ⁻² Pa, Ar as an introduction gas, a gas flow rate of 30 sccm, and a film formation start by vacuum deposition. The film was formed at a substrate temperature of 25 ° C. and a deposition rate of 0.3 nm / sec (ie, 3 Å / sec).

[Characteristic evaluation]
The optical components according to Example 1, Comparative Example 1, and Comparative Example 2 were evaluated for antireflection characteristics and mechanical characteristics over time. Specifically, the accelerated environmental resistance test was performed for 500 hours under the conditions of 85 ° C. and 85% RH. And the visual observation of the film | membrane surface of this sample and the tape peeling test were done. In addition, the reflectance was measured before and after the accelerated acceleration test.

In FIG. 3, the profile of the reflectance before and behind an environmental-resistant accelerated test in the wavelength 350-800 nm of the optical component which concerns on Example 1 is shown. 4A shows the reflectance profile of the optical component according to Comparative Example 1 before and after the environmental resistance acceleration test at wavelengths of 350 to 800 nm, and FIG. 4B shows the wavelength of the optical component according to Comparative Example 2 at 350 to 800 nm. The reflectance profile before and behind an environmental-resistant acceleration test in 800 nm is shown. Table 1 shows the film surface observation after the accelerated acceleration resistance test, the results of the tape peeling test, and the value of the change in reflectance at 500 nm.

  As shown in FIGS. 3 and 4, the reflectance of the optical component according to Example 1, Comparative Example 1 and Comparative Example 2 before the environmental resistance acceleration test shows almost the same profile. This is because the reflectance of the antireflection film 2 composed of the low refractive index layer and the high refractive index layer according to Example 1 is composed of only the low refractive index layer according to Comparative Example 1 and Comparative Example 2. It shows that there is no inferiority compared to the reflectance of the prevention film.

  As shown in FIG. 3, the reflectance after the environmental resistance acceleration test of the optical component according to Example 1 shows a profile that substantially matches the profile before the environmental resistance test, and no change in reflectance over time is observed. It was. The amount of change in reflectance at 500 nm was calculated and found to be 0.01%. On the other hand, as shown in FIG. 4, the reflectance after the accelerated environmental resistance test of the optical components according to Comparative Example 1 and Comparative Example 2 is confirmed over the entire wavelength range of 350 to 800 nm. It was. The amount of change in reflectance at a wavelength of 500 nm of the antireflection film 102 according to Comparative Example 1 and the antireflection film 202 according to Comparative Example 2 was calculated and found to be 0.40% and 1.00%, respectively. It can be seen that the optical component according to Example 1 can achieve a reflectance comparable to that of an antireflection film composed of only a low refractive index layer, and can suppress changes in antireflection characteristics over time.

  When the tape peeling test was performed after the accelerated environmental resistance test, as shown in Table 1, the antireflection film 2 of Example 1 according to the present invention did not peel. On the other hand, partial peeling occurred in the antireflection film 102 according to Comparative Example 1, and peeling of the entire surface occurred in the antireflection film 202 according to Comparative Example 2.

  When the film surface was observed after the accelerated environmental resistance test, as shown in Table 1, the antireflection film 2 of Example 1 according to the present invention showed no abnormality, whereas the antireflection film according to Comparative Example 1 was not observed. The film 102 had microcracks, and the antireflection film 202 according to Comparative Example 2 had cracks.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical substrate 2 Antireflection film 3 1st layer 4 2nd layer 5 3rd layer 6 4th layer 7 5th layer 10 Optical component

FIG. 2 is a schematic cross-sectional view illustrating a configuration of an optical component according to an embodiment. (A) Schematic sectional drawing which shows the structure of the optical component which concerns on the comparative example 1, (b) Schematic sectional drawing which shows the structure of the optical component which concerns on the comparative example 2. 5 is a reflectance profile with respect to the wavelength of the optical component according to the first embodiment. (A) The reflectance profile of the antireflection film according to Comparative Example 1, and (b) The reflectance profile of the antireflection film according to Comparative Example 2.

Claims (6)

An antireflection film in which at least two optical thin film layers having different refractive indexes are laminated on an optical substrate,
The optical thin film layer is composed mainly of magnesium fluoride,
The refractive index of the optical thin film layer is 1.30 or more and 1.40 or less with respect to a wavelength of 600 nm,
The optical thin film layer includes a layer having a refractive index with respect to a wavelength of 600 nm of 1.30 or more and less than 1.35, and a layer with a refractive index with respect to a wavelength of 600 nm of 1.35 or more and 1.40 or less.
Of the optical thin film layer, the refractive index of the outermost layer on which light enters from the air surface is 1.35 or more and 1.40 or less with respect to a wavelength of 600 nm ,
The antireflective film in which the layer having a refractive index of 1.30 or more and less than 1.35 is sandwiched between layers having the refractive index of 1.35 or more and 1.40 or less . The antireflection film according to claim 1,
Of the optical thin film layer, an antireflection film having a refractive index of a lowermost layer in contact with the optical substrate of 1.35 to 1.40 nm with respect to a wavelength of 600 nm . The antireflection film according to claim 1 or 2,
An antireflection film comprising a layer having a refractive index of 1.35 or more and 1.40 or less with respect to a wavelength of 600 nm as the optical thin film layer between the outermost layer and the lowermost layer in contact with the optical substrate. . In the antireflection film according to claim 1, 2, or 3,
An antireflection film in which a physical film thickness of the outermost layer is 5 nm or more and 300 nm or less . In the antireflection film according to any one of claims 1 to 4,
An antireflection film in which the physical film thickness of the lowermost layer is 2 nm or more and 300 nm or less . An optical component comprising the antireflection film according to claim 1 and an optical substrate .

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