WO2013172382A1

WO2013172382A1 - Optical element

Info

Publication number: WO2013172382A1
Application number: PCT/JP2013/063565
Authority: WO
Inventors: 秀一朗川岸; 照夫山下
Original assignee: Hoya株式会社
Priority date: 2012-05-15
Filing date: 2013-05-15
Publication date: 2013-11-21
Also published as: TW201400850A; JPWO2013172382A1; JP5883505B2; CN104321670B; CN104321670A; TWI588517B

Abstract

An optical element (1) is provided with an optical film (20). The optical film (20) is provided with an aluminum oxide layer (21) which comprises aluminum oxide as the main component and which has an optical film factor (x) of 0.010 to 2.00 as defined on the basis of optical thickness (nd) and central wavelength (λ₀). Further, the optical film (20) exhibits a shift of 0.50 % or less between the first reflectance (R1) at ordinary temperature and the second reflectance (R2) at the time of heating, both reflectances being measured at the same wavelength in the central wavelength bandwidth.

Description

Optical element

The present invention relates to an optical element.

An optical element such as an optical glass lens is coated with an optical thin film on the surface to be an optical surface in order to obtain desired optical characteristics. As an optical thin film, a single-layer film or a multilayer film is known in recent years, and an optical thin film having a multilayer structure including an aluminum oxide (Al ₂ O ₃ ) layer may be used (see, for example, Patent Document 1). .

JP-A-9-159803

However, the optical thin film including the aluminum oxide layer may cause uneven color on the surface of the optical element when the optical surface of the optical element is coated. This color unevenness is caused by locally non-uniform film quality (film refractive index, film density, etc.) of the optical thin film in the plane of the optical surface. Occurrence of color unevenness is a factor that lowers the product yield due to non-uniformity of optical characteristics (for example, reflectance and coat color quality (color)) of the optical thin film. Therefore, it is desired to prevent the occurrence of color unevenness.

An object of the present invention is to provide an optical element provided with an optical thin film having a uniform and dense film quality in which color unevenness does not occur even if the optical thin film includes an aluminum oxide layer.

The present invention has been devised to achieve the above object.
In order to achieve the above object, the inventors of the present application first examined the cause of color unevenness. As a result, color unevenness is caused by the aluminum oxide layer taking in moisture or the like during or after film formation. This can be said to be clear from the verification result of the shift amount (the wavelength shift, in other words, the change amount of the spectral characteristics at normal temperature and at the time of heating) whose details will be described later.

Based on such knowledge, the inventors of the present application have made further studies and as a result, if an aluminum oxide layer having a uniform and dense film quality can be realized, it is possible to prevent the intake of moisture and the like that cause color unevenness. I got the idea that it might be.

The present invention has been made based on the above-described new knowledge and idea by the present inventors. That is, the inventors of the present application have arrived at the problem solving means described below based on the above-described new knowledge and idea.

An optical element according to an embodiment of the present invention includes an optical thin film. The optical thin film includes an aluminum oxide layer having an optical thin film coefficient in a range of 0.010 or more and 2.00 or less, which is defined on the basis of an optical film thickness and a center wavelength. In the same wavelength, the shift amount between the first reflectance at normal temperature and the second reflectance at heating is 0.50% or less.

According to the present invention, even an optical thin film including an aluminum oxide layer can provide an optical element including an optical thin film having a uniform and fine film quality that does not cause color unevenness.

It is principal part sectional drawing which shows the structural example of the optical element to which Embodiment 1 of this invention was applied. It is explanatory drawing which plotted on the two-dimensional coordinate plane the specific example of the relationship between the wavelength of the light of the optical thin film (aluminum oxide layer) in Example 1 of this invention, and the reflectance of light. It is explanatory drawing about the comparative example 1 used as the comparison object with Example 1 of this invention. It is principal part sectional drawing which shows the structural example of the optical element to which Embodiment 2 of this invention was applied. It is explanatory drawing which plotted on the two-dimensional coordinate plane the specific example of the relationship between the wavelength of the light of the optical thin film in Example 2 of this invention, and the reflectance of light. It is explanatory drawing about the comparative example 2 used as the comparison object with Example 2 of this invention. It is explanatory drawing which plotted on the two-dimensional coordinate plane one specific example of the relationship between the wavelength of the light of the optical thin film in Example 3 of this invention, and the reflectance of light. It is explanatory drawing which plotted on the two-dimensional coordinate plane one specific example of the relationship between the wavelength of the light of the optical thin film in Example 4 of this invention, and the reflectance of light. It is explanatory drawing which plotted on the two-dimensional coordinate plane one specific example of the relationship between the wavelength of the light of the optical thin film in Example 5 of this invention, and the reflectance of light.

Embodiments

1 and 2 of the present invention will be described below with reference to the drawings.
Here, each embodiment will be described in the following order.
1. 1. Overall configuration of optical element 2. Configuration of optical thin film Deposition procedure

In addition, the following description is common to the first and second embodiments.
4). 4. Effects of

Embodiments

1 and 2 Modified example

In Embodiment 1, the optical thin film formed on the optical surface of the optical element is formed of a single layer film. In Embodiment 2 described later, the optical thin film formed on the optical surface of the optical element is formed of a multilayer film.

In the following embodiments, the center wavelength band will be described by taking the wavelength band of visible light as an example, the wavelength region is 400 nm to 700 nm, and the center wavelength λ ₀ is 550 nm. In the following description, the optical thin film coefficient can be in the range of 0.010 to 2.00. In the description regarding numerical values other than those in the wavelength region, “numerical value to numerical value” includes values at both ends unless otherwise specified.

Embodiment 1

<1. Overall configuration of optical element>
First, the overall configuration of the optical element will be described.

An optical element is an element that performs some kind of optical processing on light (particularly visible light), and specifically includes optical devices such as lenses, prisms, mirrors, filters, light guides, and diffraction elements.

FIG. 1 is a cross-sectional view of an essential part showing a configuration example of an optical element to which the present invention is applied.
As shown in FIG. 1, in the optical element 1, an optical surface 5 of an optical element substrate 10 that is an element substrate is coated with an optical thin film 20.

The optical element substrate 10 is made of an optical glass material, and an optical functional surface such as a spherical surface, an aspherical surface, a plane, or a diffraction grating is formed on the surface of the optical element substrate 10 as an optical surface 5. Further, as the optical glass material of the optical element substrate 10, for example, M-TAFD305, M-LAC130, M-BACD12, M-FDS2, M-FD80, M-TAFD307, M-FCD1, M-FCD500, M-PCD4 M-TAF101, E-FDS1, E-FDS2, TAFD30, TAFD35, TAF1, FCD100, FCD505, BACD5 (manufactured by HOYA Corporation) and the like can be used.

<2. Configuration of optical thin film>
Next, the optical thin film 20 formed on the optical surface 5 of the optical element substrate 10 of the optical element 1 will be described.

The optical thin film 20 has a function of assisting the optical action (optical characteristics) of the optical element 1, and specifically has a function of reducing (preventing) reflection of light on the lens surface.

The layer located on the side in contact with the optical surface 5 of the optical element substrate 10 is a layer (hereinafter referred to as “aluminum oxide layer”) 21 formed of aluminum oxide (alumina). However, in the first embodiment, the aluminum oxide layer 21 is formed by a film forming process in which film constituent particles are deposited with ion energy of 10 eV or more. Specifically, ion beam assisted deposition (Ion-beam Assisted Deposition, hereinafter referred to as “IAD”), which will be described later, is used. When this aluminum oxide layer 21 is used as the optical thin film 20, the relationship between the wavelength of light and the reflectance of light is measured in a wavelength region of 400 nm to 700 nm before and after heat treatment up to a predetermined temperature at which moisture can be removed. It has a film structure in which the maximum change in light reflectance is 0.50% or less.

Here, “before the heat treatment” means before the optical thin film 20 is heated (that is, when the optical thin film 20 is at room temperature), and “after the heat treatment” means that the optical thin film 20 is heated. The heating time is shown. In addition, the “maximum change in light reflectance” refers to the first reflectance R1 at normal temperature and the second reflectance R2 at heating at the same wavelength in the wavelength region of 400 nm to 700 nm. An absolute value of the difference (hereinafter referred to as a shift amount ΔR (= | R1-R2 |)) is shown.

Moreover, as a preferable aspect of the present embodiment, the aluminum oxide layer 21 has a first reflectance R1 at a normal temperature and a second reflectance R2 at the time of heating at the same wavelength in a wavelength region of 400 nm to 700 nm. The film structure has a shift amount ΔR of 0.30% or less. In the following description, “normal temperature” means 25 ° C., and “heating” means, for example, the case of heating to 150 ° C.

Further, as an aspect of this embodiment, the refractive index n of the aluminum oxide layer 21 is 1.64 or more and 1.70 or less. The details of the film forming procedure for forming the aluminum oxide layer 21 and the layer structure of the aluminum oxide layer 21 will be described later.

<3. Deposition procedure>
Next, a film forming procedure of the optical thin film 20 having the above-described configuration will be described.
The optical thin film 20 is formed by depositing thin film particles on the optical surface 5 of the optical element substrate 10 of the optical element 1.

(Film formation process)
The film forming process for forming the aluminum oxide layer 21 will be described in detail.

(Aluminum oxide layer deposition method)
In the film forming process of the first embodiment, the aluminum oxide layer 21 is formed by using ion beam assisted deposition (hereinafter, abbreviated as “IAD”) to form the film-constituting particles into an optical element with an ion energy of 10 eV or more. It is formed by a film forming process for depositing on the optical surface 5 of the substrate 10.

Here, the IAD irradiates the film-forming object with gas ions (and the same amount of electrons for neutralization) with an ion gun during vacuum deposition, and uses the kinetic energy to This is a film forming process to be deposited. According to such IAD, the ion energy to be irradiated can be increased, and a uniform and dense film quality film can be obtained. Here, the “uniform and dense film quality” in the case where the optical thin film 20 is formed of one aluminum oxide layer is a predetermined value that can remove moisture with respect to the relationship between the wavelength of light and the reflectance of light. It is defined as having a film structure in which the maximum value of the change in the reflectance of light in the wavelength region of 400 nm to 700 nm is 0.50% or less before and after the heat treatment up to the temperature. The “uniform and dense film quality” in the case where the optical thin film 20 is formed from a multilayer film including an aluminum oxide layer is the first reflectance at normal temperature in the same wavelength region of 400 nm to 700 nm. It is defined as having a film structure in which the shift amount ΔR between R1 and the second reflectance R2 during heating is 0.30%. Note that color unevenness does not occur if the film has the “uniform and dense film quality” referred to here.

(Conditions for aluminum oxide layer formation)
The IAD film forming conditions in the film forming process of the first embodiment are as follows.

For example, when the ion gun used for IAD is a thermionic excitation type ion gun, a mixed gas of oxygen and argon is used as the introduction gas in the film forming chamber, and the introduction gas flow rate is set to oxygen: 0 to 200 SCCM ( Standard Cubic Centimeter per Minutes) and Argon: At least one of 0 to 200 SCCM is increased from 0 SCCM. Regarding the output of the ion gun, the voltage and current applied to the filament of the ion gun are set to filament voltage: 10 to 100 V and filament current: 15 to 150 A, respectively. Furthermore, the voltage and current applied to the anode of the ion gun are set to an anode voltage of 10 to 500 V and an anode current of 1 to 30 A, respectively. The film forming rate is set to 0.01 to 1.50 nm / sec.

In the first embodiment, a thin film forming apparatus including a thermionic excitation type ion gun is used (not shown). In this thermoelectron excitation type ion gun, by increasing the number of filaments that are thermoelectron generating members constituting the ion gun, film-constituting particles are deposited with ion energy of 10 eV or more, and a uniform and dense film quality layer is formed. Can be formed.

Further, for example, when the ion gun used for IAD is a radio frequency (RF) excitation type ion gun, the output of the ion gun includes the voltage applied to the acceleration electrode of the ion gun, and the current with an acceleration voltage of 10 to 1500 V, acceleration current: 10 to 1500 mA. For the acceleration electrode, a positive voltage is applied between the electrode and the ground. The voltage and current applied to the suppressor electrode of the ion gun are set to suppressor voltage: 0 to 1000 V and suppressor current: 10 to 100 mA, respectively. For suppressors, a voltage between the electrode and ground is applied to-. Other conditions are the same as in the case of the above-described thermionic ion gun.

(Film quality of aluminum oxide layer)
When film formation is performed under such conditions, film constituent particles of the aluminum oxide layer 21 are deposited on the optical surface 5 of the optical element substrate 10 with ion energy of 10 eV or more (specifically, for example, about 1000 eV). Therefore, a uniform and dense film-like aluminum oxide layer 21 is formed on the optical surface 5 of the optical element substrate 10.

Next, the embodiment of the present invention will be specifically described with reference to examples. However, it is needless to say that the present invention is not limited to the following examples.

Moreover, the oxide film which comprises a layer should just be desired film quality, and the composition is not specifically limited. The composition of the aluminum oxide film, those containing aluminum oxide which is stoichiometric composition _(Al 2 _{O 3)} is a stable, although described as _{the Al} 2 _{O 3} layer in the following _description, Al 2 _{O 3} When the composition is Al _x O _y , for example, y / x = 1 to 2 may be present. The same applies to various oxide films such as a silicon oxide film and a tantalum oxide film described below.

In the following description, the layer numbers are assigned in order from the optical surface 5 side of the lens substrate 10. Further, the refractive index of each layer is n, the physical film thickness is d, the optical film thickness is nd, the optical thin film coefficient is x, and the center wavelength is λ ₀ . The optical film thickness nd is represented by the product of the refractive index n and the physical film thickness d.

The optical thin film coefficient x is expressed by the following equation (1) and is defined based on the optical film thickness nd and the center wavelength λ ₀ .
Optical thin film coefficient x = nd × (1 / ( λ 0/4)) ··· Equation (1)

Further, the optical thin film coefficient x of the aluminum oxide layer which is defined based on the optical film thickness nd and the center wavelength λ ₀ and contains aluminum oxide as a main component is set in the range of 0.010 or more and 2.000 or less. The center wavelength λ ₀ is described as 550 nm, but can be set to 500 nm, 1000 nm, 2000 nm, or the like. The physical thickness d of the aluminum oxide layer can be set in the range of 8.0 nm or more and 500.0 nm or less. In the above formula (1) and the following description, “4” is used as a value for dividing the center wavelength λ ₀ , but is not limited thereto. For example, it can be an integer such as “2” or “6”.

Example 1
Specifically, in Example 1, the following optical thin film 20 was formed.
Table 1 shows the film configuration of the optical thin film 20 according to Example 1. Table 2 shows film forming conditions of the optical thin film 20 according to the first embodiment.

As the optical element substrate 10, M-TAFD305 (manufactured by HOYA Co., Ltd.), which is a glass mold lens glass type, was used. An optical thin film 20 having a single layer structure was formed on the optical surface 5 of the optical element substrate 10. The optical thin film 20 is an Al ₂ O ₃ layer 21 having a physical film thickness of 92.91 nm.

The Al ₂ O ₃ layer 21 was subjected to film formation under the following film formation conditions in order to deposit film constituent particles with an ion energy of 90 eV. That is, in the film forming process for forming the Al ₂ O ₃ layer 21, a thermoelectron excitation type ion gun is used as the ion gun, and the voltage applied to the anode and the current are set to an anode voltage of 90 V and an anode current of 15 A, respectively. did. The voltage and current applied to the filament were filament voltage: 55 V and filament current: 90 A, respectively. Further, a mixed gas of oxygen (O ₂ ) and argon (Ar) was used as the introduced gas in the film formation chamber, the O ₂ gas flow rate was set to 35 SCCM, and the Ar gas flow rate was set to 5 SCCM. Moreover, the temperature of the optical element base material 10 which is a film formation target was set to 250 ° C. The evaporation rate (film formation rate) of Al ₂ O ₃ was set to 0.10 nm / sec.

When the relationship between the wavelength of light and the reflectance of light was measured for the optical thin film 20 (single layer film composed of the aluminum oxide layer 21) under the above film forming conditions, the result shown in FIG. 2 was obtained. It was.

FIG. 2 is an explanatory diagram in which the relationship between the light wavelength and the light reflectance of the optical thin film 20 (aluminum oxide layer 21) in Example 1 is plotted on a two-dimensional coordinate plane. In FIG. 2, the wavelength of light and the reflectance of light for the aluminum oxide layer 21 at room temperature and when heated to 150 ° C., which is an example of a predetermined temperature at which moisture can be removed, are shown. The relationship is plotted on a two-dimensional coordinate plane in which the horizontal axis is the wavelength of light (unit: nm) and the vertical axis is the reflectance of light (unit:%).

FIG. 2 shows a specific example of the relationship between the wavelength of light and the reflectance of the aluminum oxide layer 21 obtained by performing IAD under the conditions described in the first embodiment. In the partially enlarged view of FIG. 2, the reflectances R1 and R2 indicate the reflectance at normal temperature and the reflectance at the time of heating, respectively, at a predetermined wavelength.

Table 3 shows (A) reflectivity R1 at room temperature, (B) reflectivity R2 at heating, and shift amount ΔR at the wavelengths 400 nm, 500 nm, 600 nm, and 700 nm in FIG. (A difference between the reflectance R1 at normal temperature and the reflectance R2 at the time of heating is expressed in absolute value). Further, the two right-hand columns of Table 3 show the maximum shift amount ΔRmax and minimum shift amount ΔRmin at wavelengths of 400 nm to 700 nm in FIG. 2 and the wavelengths at ΔRmax and ΔRmin, respectively.

As is apparent from the contents shown in FIGS. 2 and 3, the aluminum oxide layer 21 has a plot position on the two-dimensional coordinate plane regarding the relationship between the wavelength of light and the reflectance at normal temperature and when heated. It turns out that there is almost no change. In other words, the plot positions are closer to each other, and it can be seen that the change in reflectance is extremely small between room temperature and heating.

Referring to FIG. 2, the reflectance shift amount ΔR at normal temperature and during heating is specifically as follows.

In the visible wavelength range of 400 nm to 700 nm, the reflectance shift (change) amount ΔR is greatest when the wavelength is 415 nm. The reflectivity R1 at normal temperature is 6.893%, whereas the reflectivity R2 at heating is 6.951%, and the difference between them (the amount of shift ΔR in reflectivity between normal temperature and heating) Is 0.058%. The shift amount ΔR is the smallest when the wavelengths are 433 nm, 665 nm, and 666 nm, and the shift amount ΔR is 0.014%. In such a wavelength band, the shift amount ΔR also belongs to the range of the minimum value 0.014% to the maximum value 0.058% for other wavelengths. That is, in the wavelength band of 400 nm or more and 700 nm or less, the shift amount ΔR is 0.058 or less, which is extremely small.

Thus, the reason why the shift amount ΔR is extremely small is that the aluminum oxide layer 21 has a uniform and dense film quality.

According to the measurement results shown in FIG. 2 and Table 3, the aluminum oxide layer 21 has a uniform and dense film quality at least in the wavelength region of 400 nm to 700 nm, which is the visible region, and no color unevenness occurred. Moreover, if it is the optical thin film 20 in Example 1, it can be said that an antireflection function can fully be exhibited in a visible region. In addition, the optical thin film 20 formed in Example 1 is a single layer film comprised by the aluminum oxide layer, and it is more preferable to make shift amount (DELTA) R into 0.10% or less.

(Comparative Example 1)
FIG. 3 is an explanatory diagram of Comparative Example 1 that is a comparison target with Example 1 of the present invention. For comparison with the contents shown in FIG. 2, FIG. 3 shows the wavelength and reflection of light when an aluminum oxide layer formed on the optical surface 5 of the optical element substrate 10 is formed by vacuum deposition. A specific example of the relationship with the rate is shown.
As the optical element substrate 10, M-BACD12 (manufactured by HOYA Corporation), which is a glass mold lens glass type, was used. Then, an optical thin film made of a single layer film was formed on the optical surface 5 of the optical element substrate 10.

Specifically, in Comparative Example 1, the following optical thin film was formed.
Table 4 shows the film configuration of the optical thin film according to Comparative Example 1. Table 5 shows the film forming conditions of the optical thin film according to Comparative Example 1.

The optical thin film is an Al ₂ O ₃ layer having a physical thickness of 84.41 nm formed by vacuum deposition. The Al ₂ O ₃ layer was subjected to film formation under the film formation conditions shown in Table 5 in order to deposit Al ₂ O ₃ . That is, in the Al ₂ O ₃ layer deposition process, oxygen (O ₂ ) gas was used as the introduced gas in the deposition process chamber, and the O ₂ gas flow rate was 15 SCCM. Moreover, the temperature of the optical element base material 10 which is a film formation target was set to 250 ° C. Moreover, the evaporation rate (film formation rate) of Al ₂ O ₃ was set to 0.80 nm / sec.

When the relationship between the wavelength of light and the reflectance of light was measured for the optical thin film (single layer film composed of an aluminum oxide layer) under the above film forming conditions, the result shown in FIG. 3 was obtained.

3 shows that the relationship between the wavelength of light and the reflectance shown in FIG. 3 is greatly different between the plot position on the two-dimensional coordinate plane at normal temperature and when heated. Specifically, the shift (change) amount of the reflectance at normal temperature and heating in FIG. 3 is as shown in Table 6 and below. In Table 6, on the left side of Table 6, (A) reflectivity R1 (not shown) at normal temperature and (B) reflectivity R2 (not shown) at the wavelengths of 400 nm, 500 nm, 600 nm, and 700 nm in FIG. ) And the shift amount ΔR (the absolute value of the difference between the reflectance at normal temperature and the reflectance at the time of heating). The rightmost column of Table 6 shows the maximum shift amount ΔRmax at wavelengths of 400 nm to 700 nm in FIG. 3 and the wavelength at ΔRmax.

In the visible wavelength range of 400 nm to 700 nm, the reflectance shift amount ΔR is greatest when the wavelengths are 489 nm and 502 nm. When the wavelength is 489 nm, the reflectance at normal temperature is 7.293%, whereas the reflectance at heating is 6.786%, and the difference (shift in reflectance between normal temperature and heating) The amount ΔR) is 0.507%. Further, when the wavelength is 502 nm, the reflectance at normal temperature is 7.349%, whereas the reflectance at heating is 6.842%, and the difference (reflection between normal temperature and heating) The rate shift amount ΔR) is 0.507%.
That is, in the wavelength band of 400 nm or more and 700 nm or less, the maximum amount of reflectance shift ΔR between the room temperature and the time of heating exceeds 0.50%.

As described above, in the case of an aluminum oxide layer formed by vacuum deposition, the shift amount ΔR is large because the formed aluminum oxide layer is porous, and moisture and the like at normal temperature (that is, before treatment for removing moisture). This is thought to be due to the removal of moisture and the like that was taken in during the heating. In other words, since the maximum value of the shift amount ΔR exceeds 0.50%, such an aluminum oxide layer is not uniform and dense film quality.

Considering the above-described contents of FIGS. 2 and 3 comprehensively, the maximum value of the reflectance shift amount ΔR during normal temperature and heating in the wavelength region of 400 nm to 700 nm is 0.50% or less (preferably 0 .30% or less, more preferably 0.10% or less), it can be said that the aluminum oxide layer 21 has a uniform and dense film quality.

Embodiment 2

Next, Embodiment 2 will be described. In the second embodiment, as described above, the optical thin film 20 formed on the optical surface 5 of the optical element substrate 10 is formed of a multilayer film. The first embodiment and the second embodiment include many common parts. Therefore, in the following description of the second embodiment, parts different from the first embodiment will be mainly described.

<1. Overall configuration of optical element>
The overall configuration of the optical element is the same as that of the first embodiment.

<2. Configuration of optical thin film>

Next, the configuration of the optical thin film 20 (multilayer film) formed on the optical surface 5 of the optical element substrate 10 of the optical element 1 shown in FIG. 4 will be described. FIG. 4 is a cross-sectional view of an essential part showing a configuration example of an optical element as an example of the optical element 1 to which Embodiment 2 of the present invention is applied. The optical thin film 20 shown in FIG. 4 has an antireflection film function, and the optical element substrate 10 is an optical glass lens. The optical thin film 20 has an eight-layer structure including first to eighth layers formed in order from the optical surface 5 side of the optical element substrate 10 so as to obtain an antireflection function. In addition, the optical thin film 20 may be comprised from m layers (m is an integer greater than or equal to 2) other than eight layers.

(First layer)
The configuration of the first layer is the same as that of the first embodiment.

(2nd to 7th layers)
Of the multilayer films from the first layer to the eighth layer, the second layer to the seventh layer formed so as to overlap the aluminum oxide layer 21 as the first layer are a low refractive index material layer and a high refractive index material layer. And a repetitive structure portion in which and are alternately stacked. More specifically, the second layer, the fourth layer, and the sixth layer are the low refractive index material layers 22, 24, and 26. The third layer, the fifth layer, and the seventh layer are the high refractive index material layers 23, 25, and 27. As a material for forming the low refractive index material layers 22, 24 and 26, for example, silicon oxide having a refractive index n of 1.45 to 1.50 can be used. As a material for forming the high refractive index material layers 23, 25 and 27, for example, tantalum oxide having a refractive index n of 2.00 to 2.35 can be used.

Note that the layer structure of the repetitive structure portion mentioned here is only one specific example. For example, regarding the number of layers constituting the repetitive structure portion, the low refractive index material layer and the high refractive index material layer as described above are not composed of 3 layers each for 6 layers in total, but 4 layers each for 8 layers in total. As such, it may have another layer structure. Further, for example, as a material for forming the low refractive index material layers 22, 24 and 26, aluminum oxide, magnesium fluoride, aluminum fluoride, yttrium fluoride, neodymium fluoride, or the like is used instead of silicon oxide as described above. It doesn't matter. Furthermore, for example, as a material for forming the high refractive index material layers 23, 25, and 27, titanium oxide, niobium oxide, zirconium oxide, palladium oxide, zinc oxide, or the like may be used instead of tantalum oxide as described above. . In addition, each layer from the second layer to the eighth layer may use a mixed material obtained by mixing these materials in an appropriate ratio.

(8th layer)
Of the multilayer films from the first layer to the eighth layer, the eighth layer located on the outer surface side is a layer 28 formed of magnesium fluoride. The eighth layer is formed of another low refractive index material such as silicon oxide, aluminum fluoride, yttrium fluoride, or neodymium fluoride as long as it functions as a protective film. It does not matter.

<3. Deposition procedure>
Next, a film forming procedure of the optical thin film 20 having the above-described configuration will be described.
The optical thin film 20 is formed in order from the first layer to the eighth layer on the optical surface 5 of the optical element substrate 10 of the optical element 1.

(First layer deposition process)
Since the first layer film forming step is the same as that of the first embodiment, the description thereof is omitted.

(2nd layer deposition process to 8th layer deposition process)
After the aluminum oxide layer 21 is formed in the first layer forming step, the second layer forming step for forming the second layer, the third layer forming step for forming the third layer, and the fourth A fourth layer forming step for forming a layer, a fifth layer forming step for forming a fifth layer, a sixth layer forming step for forming a sixth layer, and a seventh layer for forming a seventh layer A film forming process and an eighth layer film forming process for forming the eighth layer are sequentially performed.

In the second layer film forming step to the eighth layer film forming step, the second layer to the eighth layer can be formed by IAD as in the case of the film forming step of the first embodiment described above. However, the second layer film forming step to the eighth layer film forming step are not necessarily performed by IAD, and may be formed by, for example, vacuum deposition.

Note that the details of the second layer film forming step to the eighth layer film forming step may be performed using a known technique, and thus the description thereof is omitted here. In addition, when IAD is used in the second layer forming process to the m-th layer forming process, the film can be formed under the above-described film forming conditions and the conditions specifically shown below.

The optical thin film 20 for coating the optical surface 5 of the optical element substrate 10 of the optical element 1 is formed by sequentially performing the first layer forming process to the eighth layer forming process as described above.

Next, the second embodiment of the present invention will be specifically described with reference to examples. However, it is needless to say that the present invention is not limited to the following examples.
FIGS. 5 and 7 to 9 are explanatory diagrams for Embodiments 2 to 5 of the present invention. FIG. 6 is an explanatory diagram for Comparative Example 2.

Moreover, the oxide film which comprises each layer should just be desired film quality, and the composition is not specifically limited. The composition of the aluminum oxide film, since those containing aluminum oxide which is stoichiometric composition _(Al 2 _{O 3)} is a stable, although described as _{the Al} 2 _{O 3} layer in the following _description, Al 2 _{O 3} When the composition is Al _x O _y , for example, y / x = 1 to 2 may exist. The same applies to various oxide films such as a silicon oxide film and a tantalum oxide film described below.

(Example 2)
Specifically, in Example 2, the optical thin film 20 shown in Table 7 was formed.
Table 7 shows the film configuration of the optical thin film 20 according to Example 2. Table 8 shows the film forming conditions of the optical thin film 20 according to Example 2.

In Example 2, M-LAC130 (manufactured by HOYA Corporation), which is a glass type for glass mold lenses, was used for the optical element substrate 10. Then, an optical thin film 20 having an eight-layer structure was formed on the optical surface 5 of the optical element substrate 10. That is, the first layer in the optical thin film 20 is an Al ₂ O ₃ layer 21 having a physical thickness of 10.00 nm formed by IAD.

The second to seventh layers are a SiO ₂ layer 22 having a physical thickness of 4.20 nm, a Ta ₂ O ₅ layer 23 having a physical thickness of 28.44 nm, a SiO ₂ layer 24 having a physical thickness of 16.45 nm, Repetitive structure in which a Ta ₂ O ₅ layer 25 having a physical thickness of 74.71 nm, a SiO ₂ layer 26 having a physical thickness of 15.04 nm, and a Ta ₂ O ₅ layer 27 having a physical thickness of 30.86 nm are sequentially stacked. Part. The second to seventh layers constituting this repetitive structure are also formed by IAD.

The eighth layer serving as the outermost surface layer of the optical thin film 20 is an MgF ₂ layer 28 having a physical thickness of 97.74 nm formed by vapor deposition.

Thus, the optical thin film 20 is a multilayer film 21 to 28 formed by laminating a plurality of film forming materials, and the multilayer films 21 to 28 are silicon oxide layers 22, 24, 26 formed of silicon oxide. And tantalum oxide layers 23, 25, 27 formed of tantalum oxide.

Among these multilayer films, the Al ₂ O ₃ layer 21 was subjected to film formation under the following film formation conditions in order to deposit film constituent particles with ion energy of 90 eV. That is, in the first layer deposition step for depositing the Al ₂ O ₃ layer 21, a thermoelectron excitation type ion gun is used as the ion gun, and the voltage applied to the anode and the current are anode voltage: 90 V and anode current, respectively. : 18A. The voltage and current applied to the filament were filament voltage: 55 V and filament current: 90 A, respectively. Furthermore, a mixed gas of O ₂ and Ar was used as the introduced gas in the film formation chamber, the O ₂ gas flow rate was 40 SCCM, and the Ar gas flow rate was 10 SCCM. Moreover, the temperature of the optical element base material 10 which is a film formation target was set to 250 ° C. The evaporation rate (film formation rate) of Al ₂ O ₃ was set to 0.10 nm / sec. Incidentally, the evaporation rate (deposition rate) of SiO ₂ is 0.30 nm / sec, the evaporation rate (deposition rate) of Ta ₂ O ₅ is 0.50 nm / sec, and the evaporation rate (deposition rate) of MgF ₂ is 0. 80 nm / sec.

When the relationship between the light wavelength and the light reflectance was measured for the optical thin film 20 formed under the above film forming conditions, the result shown in FIG. 5 was obtained.

FIG. 5 is an explanatory diagram in which a specific example of the relationship between the light wavelength and the light reflectance of the optical thin film in Example 2 of the present invention is plotted on a two-dimensional coordinate plane. In the partially enlarged view of FIG. 5, the reflectances R1 and R2 indicate the reflectance R1 at normal temperature and the reflectance R2 at the time of heating at a predetermined wavelength. In the following description, the absolute value of the difference between the reflectance R1 at normal temperature and the reflectance R2 at the time of heating is described as the shift amount ΔR.

Table 9 shows five columns on the left side of Table 9, (A) reflectivity R1 at normal temperature, (B) reflectivity R2 at heating, and shift amount ΔR at wavelengths of 400 nm, 500 nm, 600 nm, and 700 nm in FIG. (A difference between the reflectance R1 at normal temperature and the reflectance R2 at the time of heating is expressed in absolute value). The right two columns of Table 9 show the maximum shift amount ΔRmax and minimum shift amount ΔRmin at wavelengths of 400 nm to 700 nm in FIG. 5 and the wavelengths at ΔRmax and ΔRmin, respectively.

As is clear from the contents shown in FIG. 5 and Table 9, the aluminum oxide layer 21 has a plot position on the two-dimensional coordinate plane regarding the relationship between the wavelength of light and the reflectance at normal temperature and when heated. It can be seen that there has been little change. That is, the plot positions are closer to each other, and it can be seen that the shift amounts ΔR of the reflectances R1 and R2 during normal temperature and during heating are extremely small. In addition, it can be seen that in the wavelength band of 400 nm to 700 nm, the reflectance is 0.50% or less and it has an antireflection function.

Specifically, the shift amount of the reflectance during normal temperature and heating in FIG. 5 is as follows. Focusing on the wavelength band of 400 nm or more and 700 nm or less, which is the visible range, the reflectance shift amount is the largest when the wavelength is 400 nm. The reflectance R1 at the normal temperature is 0.222%, whereas the reflectance R2 at the heating is 0.278%, and the difference (the reflectance shift amount ΔR between the normal temperature and the heating). Is 0.056%. The shift amount ΔR is the smallest when the wavelengths are 670 nm and 680 nm, and the difference in reflectance between room temperature and heating is 0%. In the wavelength band of 400 nm or more and 700 nm or less, the difference in reflectance between room temperature and heating also falls within the range of the minimum value 0% to the maximum value 0.056% for other wavelengths. That is, in the wavelength band of 400 nm or more and 700 nm or less, the shift amount ΔR of the reflectances R1 and R2 at normal temperature and heating is 0.30% or less, and the aluminum oxide layer 21 can be said to have a uniform and dense film quality. . In the optical thin film 20 in Example 2, no color unevenness occurred. It can also be said that the antireflection function can be sufficiently exerted in the visible region.

(Comparative Example 2)

Specifically, in Comparative Example 2, the following optical thin film having an antireflection function was formed.
Table 10 shows the film configuration of the optical thin film according to Comparative Example 2. Table 11 shows the film forming conditions of the optical thin film according to Comparative Example 2.

Here, Comparative Example 2 will be described for comparison with Example 2 described above. FIG. 6 is an explanatory diagram of Comparative Example 2 that is a comparison target with Example 2 of the present invention. In Comparative Example 2, the following optical thin film was formed using the vacuum deposition method.

For the optical element substrate 10 of the optical element 1, M-BACD12 (manufactured by HOYA Corporation), which is a glass mold lens glass type, was used. Then, an optical thin film having a four-layer structure having an antireflection function was formed on the optical surface 5 of the optical element substrate 10.

That is, the first to fourth layers in the optical thin film are an Al ₂ O ₃ layer having a physical film thickness of 59.66 nm, an Al ₂ O ₃ layer having a physical film thickness of 91.84 nm, and a physical film thickness of 115.58 nm. This is a repetitive structure portion in which a ZrO ₂ + TiO ₂ layer and a MgF ₂ layer having a physical thickness of 89.43 nm are sequentially laminated. The first to fourth layers constituting the repetitive structure are formed under the following conditions.

The gas flow rate of O ₂ , which is the introduced gas in the film forming chamber, is 15 SCCM for the first Al ₂ O ₃ layer and the third ZrO ₂ + TiO ₂ layer, respectively, and the second Al ₂ O ₃ layer. The layer was 13 SCCM. Moreover, the temperature of the optical element base material 10 which is a film formation target was set to 250 ° C. Moreover, the evaporation rate (film formation rate) of Al ₂ O ₃ , ZrO ₂ + TiO ₂ , and MgF ₂ is 0.80 nm / sec.

FIG. 6 shows the result of measuring the relationship between the wavelength of light and the reflectance of the optical thin film formed under the above conditions. Table 12 shows five columns on the left side of Table 12, (A) reflectivity R1 at room temperature at wavelengths of 400 nm, 500 nm, 600 nm, and 700 nm in FIG. 6 (not shown in FIG. 6), and (B) reflection at the time of heating. The ratio R2 (not shown in FIG. 6) and the shift amount ΔR (the difference between the reflectance R1 at normal temperature and the reflectance R2 at the time of heating are expressed in absolute values) are shown. The rightmost column of Table 12 shows the maximum shift amount ΔRmax at wavelengths of 400 nm to 700 nm in FIG. 6 and the wavelength at ΔRmax.

The relationship between the wavelength of light and the reflectance shown in FIG. 6 and Table 12 shows that the plot position on the two-dimensional coordinate plane is greatly different between normal temperature and heating. Specifically, the shift amount ΔR of the reflectance at the normal temperature and at the time of heating in FIG. 6 is as follows. In the visible wavelength range of 400 nm to 700 nm, the reflectance shift amount ΔR is greatest when the wavelength is 400 nm. When the wavelength is 400 nm, the reflectance R1 at room temperature is 0.350%, whereas the reflectance R2 at heating is 0%, and the difference (shift amount ΔR) is 0.350%. It has become. That is, in the wavelength band of 400 nm or more and 700 nm or less, the shift amount ΔR has a large maximum value exceeding 0.30%, and cannot be said to be uniform and dense film quality. In the optical thin film 20 in Comparative Example 2, color unevenness is observed, and it cannot be said that the antireflection function can be sufficiently exhibited in the visible region.

(Example 3 to Example 5)
Next, Examples 3 to 5 will be described. In the third to fifth embodiments, the description already given in the second embodiment is omitted, and the contents different from the second embodiment are described.
In the third to fifth embodiments, common descriptions are described first. In Examples 3 to 5, the results of the heat treatment as in Examples 1 and 2 are not shown. However, since the inventors did not cause color unevenness in the examples shown below, We believe that the invention can be applied.

In Examples 3 to 5, M-LAC130 (manufactured by HOYA Corporation) was used for the optical element substrate 10. Tables 13, 15, and 17 show the film configuration of the optical thin film 20 according to each example. Tables 14, 16, and 18 show film forming conditions of the optical thin film 20 according to each example. FIG. 7 to FIG. 9 are explanatory diagrams in which one specific example of the relationship between the light wavelength and the light reflectance of the optical thin film in each embodiment is plotted on a two-dimensional coordinate plane. Similarly to the above-described embodiment, the optical thin film 20 in Embodiments 3 to 5 has an antireflection function. In addition, the description of what is repeated in each table is omitted.

(Example 3)
In Example 3, the physical film thickness d of the aluminum oxide layer of the first layer is changed, and in addition to the first layer, the third layer and the fifth layer are composed of the aluminum oxide layer. Further, the _second , fourth, and sixth layers were made of Ta ₂ O ₅ without using SiO ₂ as a film constituent material.

When the relationship between the wavelength of light and the reflectance of light was measured for the optical thin film 20 obtained by film formation under the above film formation conditions, the result shown in FIG. 7 was obtained. According to the measurement results shown in FIG. 7, it can be seen that the reflectance is kept low at least in the visible wavelength range of 400 nm to 700 nm. Moreover, in the optical thin film 20 in Example 3, no color unevenness was confirmed.

Also, from this result, it can be said that the aluminum oxide layer 21 may be formed not only in the first layer but also in the third layer and the fifth layer, and the physical film thickness d may be changed.

(Example 4)
In Example 4, the first aluminum oxide layer is formed by IAD using an RF excitation electron gun. Further, the number of layers of the optical thin film 20 is changed from 8 layers to 10 layers.

With respect to the optical thin film 20 obtained by film formation under the above film formation conditions, the relationship between the wavelength of light and the reflectance of light was measured, and the result shown in FIG. 8 was obtained. According to the measurement results shown in the figure, it can be seen that the reflectance is kept low at least in the wavelength region of 400 nm to 700 nm which is the visible region. Moreover, in the optical thin film 20 in Example 4, the color nonuniformity was not confirmed.

Also, from this result, it can be said that the aluminum oxide layer 21 may be a high-frequency discharge excitation electron gun as long as it is a film forming process in which film constituent particles are deposited with an ion energy of 10 eV or more. Moreover, it was confirmed that the number of layers of the optical thin film 20 is not limited to eight and may be a plurality of layers.

(Example 5)
In Example 5, while the physical film thickness d of the first aluminum oxide layer 21 is increased, the number of layers of the optical thin film 20 is changed from 8 layers to 10 layers.

When the relationship between the wavelength of light and the reflectance of light was measured for the optical thin film 20 obtained by film formation under the above film formation conditions, the result shown in FIG. 9 was obtained. According to the measurement results shown in the figure, it can be seen that the reflectance is kept low at least in the wavelength region of 400 nm to 700 nm which is the visible region. Moreover, in the optical thin film 20 in Example 5, the color nonuniformity was not confirmed.

Also, from this result, it can be said that the aluminum oxide layer 21 may be increased in physical thickness d.

(Summary)
Considering the results of Examples 1 to 5 described above and Comparative Examples 1 and 2, if the optical thin film 20 includes the Al ₂ O ₃ layer 21 in Examples 1 to 5, the Al ₂ O ₃ layer 21 is Since the film quality is uniform and dense, even when the optical surface 5 of the optical element substrate 10 is coated, it is possible to realize a good antireflection function without causing color unevenness.

<4. Effect of

Embodiments

1 and 2>
According to the optical thin film 20 described in the first and second embodiments, the following effects can be obtained.

According to

Embodiments

1 and 2, the aluminum oxide layer 21 is formed by IAD, which is a film forming process in which film constituent particles are deposited with an ion energy of 10 eV or more, and the aluminum oxide layer 21 has a uniform film quality. It has become. That is, the aluminum oxide layer 21 has a shift amount ΔR of 0.30% between the first reflectance R1 at normal temperature and the second reflectance R2 at the time of heating at the same wavelength in the wavelength region of 400 nm to 700 nm. It has the following film structure.

Therefore, since the aluminum oxide layer 21 in the first and second embodiments has a uniform and dense film quality with little room for taking up moisture and the like, it is effective to take up moisture and the like that cause color unevenness. Can be prevented. Therefore, even when the aluminum oxide layer 21 is positioned so as to be in contact with the optical surface 5 of the optical element substrate 10 or when the aluminum oxide layer 21 is formed in the second to mth layers, the product of the optical element 1 Color unevenness that may cause a decrease in yield does not occur. Therefore, it is possible to correct non-uniformity of optical characteristics (for example, refractive index n and light transmittance) in the surface of the optical surface 5 due to color unevenness. That is, according to the present embodiment, even if the optical thin film includes the aluminum oxide layer 21, the optical thin film 20 in which color unevenness does not occur can be obtained.

Further, according to the first and second embodiments, since the aluminum oxide layer 21 has “uniform and dense film quality” by the formation by IAD, the refractive index n of the aluminum oxide layer 21 is 1.64 or more. A high refractive index of 1.70 or less can be realized. That is, such a high refractive index is obtained because the aluminum oxide layer 21 has a uniform film quality. Therefore, by realizing such an aluminum oxide layer 21 having a high refractive index, it is possible to avoid the occurrence of color unevenness that may cause a decrease in product yield of the optical element 1.

<5. Modification>
Although

Embodiments

1 and 2 have been described above, the disclosure content described above shows exemplary embodiments of the present invention. That is, the technical scope of the present invention is not limited to the exemplary embodiments described above.

In the above-described embodiment, the case where IAD is performed as an example of the film forming process for depositing the film constituent particles with the ion energy of 10 eV or more in forming the aluminum oxide layer 21 is described. However, the film forming process for forming the aluminum oxide layer 21 may be a film forming process using a technique other than IAD, such as sputtering, as long as the film constituent particles are deposited with an ion energy of 10 eV or more. I do not care.

In the second embodiment, the case where the second to mth layers constituting the optical thin film 20 are formed using IAD is taken as an example. However, the film forming process for forming each layer may be a film forming process in which film constituent particles are deposited with an ion energy of 10 eV or more for at least an aluminum oxide layer, and other layers are not particularly limited. Absent.

Further, in the above-described second embodiment, the case where the first to eighth layers or the tenth layer are sequentially formed as an example of the film forming procedure of the optical thin film 20 is described. However, the optical thin film 20 may be formed separately from the optical element substrate 10 of the optical element 1 instead of the film forming procedure described in the above embodiment. In that case, the optical thin film 20 formed separately from the optical element substrate 10 is applied to the optical surface 5 of the optical element substrate 10 to coat the optical surface 5.

In the first and second embodiments, the optical element is an optical glass lens, and the optical surface 5 of the lens substrate of the optical glass lens is coated with an antireflection film as an example. However, the present invention can be applied to an optical element other than the optical glass lens, for example, an optical element such as a spherical glass lens, an aspheric glass lens, an optical filter, or a diffraction grating, as in the above-described embodiment.

In the first and second embodiments described above, the wavelength band of visible light is taken as an example of the center wavelength band, and the wavelength region is 400 nm to 700 nm (center wavelength λ ₀ is 550 nm), but the present invention is not limited to this. . For example, the center wavelength band can be set within a range of 200 nm to 2000 nm, and can be set as a visible light region within a range of 380 nm to 780 nm, and preferably set within a range of 400 nm to 700 nm. it can. In addition, the center wavelength band can be set in a range (ultraviolet region) of 200 nm or more and 380 nm or less. The central wavelength band can be set in a range (infrared region) of 780 nm or more and 2000 nm or less. The center wavelength λ ₀ can be set as appropriate within the set wavelength band. When the center wavelength band is in the range of 400 nm to 700 nm, the center wavelength λ ₀ can be set to 550 nm. preferable.

In addition, a calculation example of the optical thin film coefficient x in Example 1 is shown using the above-described formula (1).

(Calculation example in the case of Example 1)
From Formula (1) and Table 1, an example of calculating the optical thin film coefficient x in Example 1 is shown.
1. The wavelength band is set to 400 nm to 700 nm, and the center wavelength λ ₀ in the set wavelength band is set to 550 nm.
2. Next, the refractive index n and the physical film thickness d are defined. In the first embodiment, n = 1.6745 and d = 92.91.
3. The numerical values defined in the above 1 and 2 are substituted into the above equation (1) to obtain the value of the optical thin film coefficient x (x = 1.131).

In the first and second embodiments described above, the optical thin film 20 has been described as an example. However, the present invention is not limited to this. The present invention can be applied to optical thin films such as IR cut filters and UV cut filters.

In the above-described first embodiment, the example in which the shift amount ΔR is 0.50% or less has been described. However, the present invention is not limited to this. The shift amount ΔR may be 0.30% or less, and preferably 0.20% or less. More preferably, the shift amount ΔR can be set to 0.10% or less, and can also be set to 0.070% or less.

In the above-described second embodiment, the example in which the shift amount ΔR is 0.30% or less has been described. However, the present invention is not limited to this. The shift amount ΔR may be 0.20% or less, and preferably 0.15% or less. More preferably, the shift amount ΔR can be set to 0.10% or less, and can also be set to 0.070% or less.

Moreover, the following conditions and apparatus were used for the film density of the aluminum oxide layer 21 formed to have a physical film thickness of 89 nm on the flat glass substrate 10 under the film forming conditions of Example 1 described above. Measured.

The film density was measured by a high-resolution Rutherford backscattering analysis method using a high-resolution RBS (Rutherford Backscattering Spectrometry) analyzer (manufactured by Kobe Steel, Ltd.).

As a result of measuring the film density of the aluminum oxide layer 21 thus obtained, the film density was 2.93 g / cm ³ .

Further, in Examples 2 to 5 described above, the example in which the aluminum oxide layer is provided in the first layer has been described, but the present invention is not limited thereto. The aluminum oxide layer can be disposed in any of the second to mth layers.

Moreover, in the above-described third embodiment, an example in which three aluminum oxide layers are provided in the first, third, and fifth layers has been described. However, the present invention is not limited to this. Two aluminum oxide layers may be provided on the second and fourth layers, or four or more layers may be provided. The aluminum oxide layer can be provided continuously with the second and third layers, for example.

Finally,

Embodiments

1 and 2 of the present invention will be summarized using drawings and the like.

The optical element 1 according to the embodiment of the present invention includes an optical thin film 20 as shown in FIGS. 1 and 4. The optical thin film 20 includes an aluminum oxide layer 21 having an optical thin film coefficient in the range of 0.010 or more and 2.00 or less defined based on the optical film thickness nd and the center wavelength λ _0. The shift amount ΔR between the first reflectance R1 at normal temperature and the second reflectance R2 at the time of heating is 0.50% or less at the same wavelength in the central wavelength band.

Also preferably, the optical film thickness is defined based on the refractive index n and the physical film thickness d, and the refractive index n is in the range of 1.64 to 1.70.

Still more preferably, the physical film thickness d is in the range of not less than 8.0 nm and not more than 500.0 nm.

Still more preferably, the optical thin film 20 is a single layer film composed of the aluminum oxide layer 21, and the shift amount ΔR is 0.10% or less.

Still more preferably, the optical thin film 20 is a multilayer film 21 to 28 formed by laminating a plurality of film forming materials, and the multilayer films 21 to 28) are silicon oxide layers formed of silicon oxide ( 22, 24, 26) and a tantalum oxide layer (23, 25, 27) formed of tantalum oxide.

Also, in another aspect, it can be grasped as follows. The optical thin film 20 according to the embodiment of the present invention has a multilayer structure in which multilayer films (21 to 28) are laminated as shown in FIG. The first layer 21 disposed on the surface 5 and in contact with the optical surface 5 of the multilayer films (21 to 28) is formed by a film forming process for depositing film constituting particles with an ion energy of 10 eV or more. The aluminum oxide layer 21 has a relationship between the wavelength of light and the reflectance of light in a wavelength region of 400 nm to 700 nm before and after heat treatment up to a predetermined temperature at which moisture can be removed. It has a film structure in which the maximum change in light reflectance is 0.50% or less.

Also preferably, the aluminum oxide layer 21 has a refractive index n of 1.64 or more and 1.70 or less.

Furthermore, preferably, the multilayer films (21 to 28) include, in addition to the aluminum oxide layer 21, a low refractive index material layer (22, 24, and 26) and a high refractive index material layer (23, 25, and 27) and a repeating structure portion alternately stacked.

Also, in another aspect, it can be grasped as follows. In the optical element 1 according to the embodiment of the present invention, as shown in FIG. 4, the optical surface 5 of the element substrate 10 is coated with an optical thin film 20, and the optical thin film 20 is formed of a multilayer film (21 to 28). The first layer 21 on the side in contact with the optical surface 5 of the multilayer films (21 to 28) is deposited by a film forming process in which film constituent particles are deposited with an ion energy of 10 eV or more. The aluminum oxide layer 21 is formed, and the aluminum oxide layer 21 has a wavelength of 400 nm to 700 nm before and after heat treatment up to a predetermined temperature at which moisture can be removed with respect to the relationship between the wavelength of light and the reflectance of light. It has a film structure in which the maximum change in the reflectance of light in the region is 0.50% or less.

Also preferably, the optical element 1 is made of an optical glass lens.

Also, in another aspect, it can be grasped as follows. As shown in FIG. 4, the method of manufacturing the optical thin film 20 according to the embodiment of the present invention has a multilayer structure in which multilayer films (21 to 27) are laminated, and the element base material of the optical element 1 10 is a method of manufacturing an optical thin film 20 that is used by being disposed on the optical surface 5, and an aluminum oxide layer 21 is used as the first layer 21 on the side in contact with the optical surface 5 of the multilayer films (21 to 27). A first layer film forming step formed by a film forming process for depositing film constituent particles with an ion energy of 10 eV or more, and the aluminum oxide layer 21 formed in the first layer film forming step has a light wavelength and a light reflectance. The film structure is such that the maximum change in the reflectance of light in the wavelength region of 400 nm to 700 nm is 0.50% or less before and after heat treatment up to a predetermined temperature at which moisture can be removed. ing.

Also, in another aspect, it can be grasped as follows. The manufacturing method of the optical element 1 according to the embodiment of the present invention is a manufacturing method of the optical element 1 in which the optical surface 5 of the element base 10 is coated with an optical thin film 20 as shown in FIG. An optical thin film forming step for forming an optical thin film 20 having a multilayer structure in which the multilayer films (21 to 28) are laminated on the optical surface 5, the optical thin film forming step including the multilayer films (21 to 28). A first layer film forming step of forming an aluminum oxide layer 21 by a film forming process for depositing film constituent particles with an ion energy of 10 eV or more as the first layer 21 on the side in contact with the optical surface 5 of the first layer 21; The aluminum oxide layer 21 formed in the single-layer film forming step has a relationship between the wavelength of light and the reflectance of light in a wavelength region of 400 nm to 700 nm before and after heat treatment up to a predetermined temperature at which moisture can be removed. Kicking the maximum value of the change in reflectance of the light is 0.50% or less, and has a film structure.

The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 ... Optical element 5 ... Optical surface 10 ... Optical element base material 20 ... Optical thin film 21 ...

Aluminum oxide layer

22, 24, 26 ... Low refractive

index material layer

23, 25, 27 ... High refractive index material layer n ... Refractive index d ... Physical film thickness x ... Optical thin film coefficient λ ₀ ... Center wavelength R1 ... First reflectance R2 ... Second reflectance ΔR ... Shift amount.

Claims

An optical element comprising an optical thin film,
The optical thin film is
An aluminum oxide layer having an optical thin film coefficient in a range of 0.010 or more and 2.00 or less, which is mainly composed of aluminum oxide and defined based on an optical film thickness and a center wavelength,
An optical element in which the shift amount between the first reflectance at normal temperature and the second reflectance at heating is 0.50% or less at the same wavelength in the central wavelength band.
The optical film thickness is defined based on refractive index and physical film thickness,
The refractive index is in the range of 1.64 or more and 1.70 or less,
The optical element according to claim 1.
The physical film thickness is in the range of not less than 8.0 nm and not more than 500.0 nm.
The optical element according to claim 2.
The optical thin film is a single layer film composed of the aluminum oxide layer,
The shift amount is 0.10% or less.
The optical element according to any one of claims 1 to 3.
The optical thin film is
A multilayer film formed by laminating a plurality of film forming materials,
The multilayer film is
A silicon oxide layer formed of silicon oxide;
A tantalum oxide layer formed of tantalum oxide,
The optical element according to any one of claims 1 to 3.