JP2835535B2 - Anti-reflection coating for optical components - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antireflection film applied to an optical component which is advantageously used for light incident at an angle of 45 ° from a medium. is there.

[Prior Art] An optical article such as a lens or a reflector is often provided with an antireflection film on its surface. The reason for requiring such an antireflection film is mainly the following two reasons. No. One reason is that, when the number of optical components to be configured increases, the resulting transmitted light tends to decrease due to the reflection loss of the surface generated thereby, and the transmitted light is prevented from decreasing. The other main reason is that a reflected image from an optical component to be constructed may have an adverse effect on other components, and the formation of the reflected image is prevented.

For the reasons described above, it has been conventionally known that an optical component is coated with a single-layer or multilayer antireflection film. However, the single-layer antireflection film has a disadvantage that the low reflection wavelength range is narrow and the residual reflectance is large. On the other hand, a multilayer antireflection film is formed, for example, in a visible region (400 nm to 700 nm) by means such as selection of film material and adjustment of film thickness.
m) is widely used today because it has an antireflection effect over a wide range of m). As a multilayer anti-reflection film, a film having an anti-reflection effect up to the near infrared region of 800 nm, and even 900 nm, has been developed, and a wider band is being promoted.

By the way, in the majority of conventional optical products such as lenses and reflectors, light is incident on the surface perpendicularly or almost perpendicularly, and the multilayer reflective film provided on those optical products is incident perpendicularly on the surface. It was prepared so as to exhibit a good antireflection effect on light.

On the other hand, an optical system in which incident light is not perpendicular to an optical component but is incident at an angle of, for example, 45 ° from a medium is also used, and an optical component of such an optical system (reflecting mirror, etc.) includes a glass substrate. It is known that a beam splitter film or a dichroic film is provided thereon, and a multilayer antireflection film is provided on the opposite side. Recently, optical components of the optical system utilizing oblique incidence have been employed in, for example, a projection type display called a liquid crystal vision. Is desired.

[Problems to be Solved by the Invention] The anti-reflection films proposed so far are designed in consideration of the light reflection characteristic of light that enters vertically from a medium such as air. There is no known antireflection film that is flat and has low reflectance over a wide wavelength range with respect to light incident at an angle of 45 ° from a medium. But,
The reflection loss on the substrate surface at oblique incidence is larger than that at normal incidence, and there is a problem that transmitted light is further reduced particularly when a large number of optical components are used.

Therefore, an object of the present invention is to obliquely incident light,
It is possible to prevent the problems of flare and light purity that adversely affect optical components used at an angle of 透過 and decrease of transmitted light due to reflection loss on the surface of optical components over a wide wavelength range. An object of the present invention is to provide an antireflection film for an optical component.

[Means for Solving the Problem] The antireflection film for solving the above problems provided by the present invention is a multilayer film composed of a seven-layer film, a nine-layer film, or an eleven-layer film as described below.

(1) the refractive index for the seven-layer film type d line (n _d) is formed on the optical glass substrate in the range of 1.50 to 1.54, an antireflection effect for light incident at an angle of 45 ° from the medium side An anti-reflection film composed of a multilayer film as shown in the figure, wherein the multilayer film includes a first layer, a second layer, a third layer, a fourth layer, a fifth layer, and a sixth layer in order from the medium side to the substrate side. Layer, seventh
The even-numbered layers are made of a high-refractive-index material having a refractive index higher than the refractive index of the substrate and in the range of 2.20 to 2.45, and the odd-numbered layers are formed of a material having a refractive index lower than the substrate and 1.40. A low refractive index material having a refractive index in the range of 〜1.48, and the refractive index of the i-th layer is n _i , and the optical thickness of the i-th layer is n _i
When n _d (i is an integer of 1 to 7), the optical film thickness of each layer is as follows: 0.29012λ ₀ <n ₁ d ₁ <0.30806λ ₀ 0.16820λ ₀ <n ₂ d ₂ <0.18590λ ₀ 0.01805λ ₀ <n ₃ d ₃ <0.02441λ ₀ 0.32446λ ₀ <n ₄ d ₄ <0.35150λ ₀ 0.10049λ ₀ <n ₅ d ₅ <0.10887λ ₀ 0.06516λ ₀ <n ₆ d ₆ <0.07496λ ₀ 0.57885λ _{0 <n 7 d 7 <0.66599λ} 0 However, lambda _0; antireflection film that satisfies the design dominant wavelength.

(2) the refractive index with respect to nine-layer film type d line (n _d) is formed on the optical glass substrate in the range of 1.50 to 1.54, an antireflection effect for light incident at an angle of 45 ° from the medium side An anti-reflection film composed of a multilayer film as shown in the figure, wherein the multilayer film includes a first layer, a second layer, a third layer, a fourth layer, a fifth layer, and a sixth layer in order from the medium side to the substrate side. Layer, seventh
A layer, an eighth layer, a ninth layer, and a nine-layer film, wherein the even-numbered layer is made of a high-refractive-index material having a refractive index higher than the refractive index of the substrate and in the range of 2.20 to 2.45. A low refractive index material having a refractive index lower than the refractive index of the substrate and in the range of 1.40 to 1.48; and the refractive index of the i-th layer is n _i , and the optical thickness of the i-th layer is n _i
When n _d (i is an integer of 1 to 9), the optical film thickness of each layer is as follows: 0.29600λ ₀ <n ₁ d ₁ <0.30800λ ₀ 0.16100λ ₀ <n ₂ d ₂ <0.17700λ ₀ 0.02050λ ₀ <n ₃ d ₃ <0.02770λ ₀ 0.33300λ ₀ <n ₄ d ₄ <0.36100λ ₀ 0.10200λ ₀ <n ₅ d ₅ <0.11000λ ₀ 0.07440λ ₀ <n ₆ d ₆ <0.08060λ ₀ 0.26200λ _{0 <n 7 d 7 <0.29600λ} 0 0.00674λ 0 <n 8 d 8 <0.01250λ 0 0.20600λ 0 <n 9 d 9 <0.03100λ 0 However, lambda _0; antireflection film that satisfies the design dominant wavelength.

(3) the refractive index for the 11-layer film type d line (n _d) is formed on the optical glass substrate in the range of 1.50 to 1.54, an antireflection effect for light incident at an angle of 45 ° from the medium side An anti-reflection film composed of a multilayer film as shown in the figure, wherein the multilayer film includes a first layer, a second layer, a third layer, a fourth layer, a fifth layer, and a sixth layer in order from the medium side to the substrate side. Layer, seventh
A high refractive index, wherein the even layer has a refractive index higher than the refractive index of the substrate and in the range of 2.20 to 2.45, comprising an eleven-layer film named a layer, an eighth layer, a ninth layer, a tenth layer, and an eleventh layer. made of a material, the odd layer is composed of a low refractive index material having a refractive index in the and scope of 1.40 to 1.48 lower than the refractive index of the substrate, and the refractive index of the i-th layer n _i and optical i-th layer, Target film thickness n _i
When n _d (i is an integer of 1 to 11), the optical film thickness of each layer is as follows: 0.2940λ ₀ <n ₁ d ₁ <0.3060λ ₀ 0.1540λ ₀ <n ₂ d ₂ <0.1700λ ₀ 0.0166λ ₀ <n ₃ d ₃ <0.0248λ ₀ 0.3540λ ₀ <n ₄ d ₄ <0.3920λ ₀ 0.0923λ ₀ <n ₅ d ₅ <0.1020λ ₀ 0.0864λ ₀ <n ₆ d ₆ <0.0954λ ₀ 0.1490λ ₀ <n ₇ d ₇ <0.1830λ ₀ 0.0107λ ₀ <n ₈ d ₈ <0.0161λ ₀ 0.0242λ ₀ <n ₉ d ₉ <0.0725λ ₀ 0.0100λ ₀ <n ₁₀ d ₁₀ <0.0186λ ₀ 0.0279λ ₀ < n ₁₁ d ₁₁ <0.0836λ ₀ where λ ₀ ; an antireflection film that satisfies the design dominant wavelength.

Examples of the low-refractive-index substance constituting the odd-numbered layer and having a refractive index of 1.40 to 1.48 include SiO ₂ and SiO _2.
The main component is a substance having a refractive index in the above range. In addition, the refractive index constituting the above even-numbered layer 2.20 ~
Examples of the high-refractive-index substance in the range of 2.45 include TiO ₂ and a substance containing TiO ₂ as a main component and having a refractive index in the above-mentioned range.

The antireflection film of the present invention, the high refractive index material and the low refractive index material, for example, using a known thin film forming technology such as a vacuum evaporation method, the optical thickness of each of the above range. Can be formed by alternately depositing and laminating on a substrate so as to satisfy the following. As a substrate,
Glass is used.

FIG. 1 shows an example of the use form and the effect of the antireflection film of the present invention.

FIG. 1 shows a substrate 1, a beam splitter film or a red reflection dichroic film 2, and an antireflection film 7 according to the present invention.
An example of an optical component comprising: The incident light 3 is applied to the substrate 1
Obliquely incident at an angle of 45 °. The incident light 3 is separated into reflected light (surface reflected light) 4 and transmitted light 5 by the beam splitter film 2. A part of the transmitted light 5 is reflected by the back surface of the substrate 1, passes through the beam splitter film 2 again from the back side as back surface reflected light 6, and exits together with the surface reflected light 4 (that is, is synthesized). go. As a result, the obtained reflected light easily forms a flare or a double image.
An antireflection film 7 is provided on the back surface of the substrate 1 in order to prevent a decrease in the purity of reflected light due to the formation of such flare or double image.

In FIG. 1, when 2 is a red reflective dichroic film, light 3 incident on the substrate 1 obliquely is reflected by the red reflective dichroic film 2 into reflected light (surface reflected light) 4 showing red. , Cyan transmitted light 5. A part of the transmitted light 5 is reflected on the back surface of the substrate 1, passes through the red reflection dichroic film 2 from the back side again as the back surface reflected light 6, and is synthesized together with the front surface reflected light 4 and exits. As a result, the purity of the red surface reflected light 4 is reduced. An anti-reflection film 7 is provided on the back surface of the substrate 1 to prevent such a decrease in the purity of the reflected light.

Note that the antireflection film of the present invention is generally provided only on the back side of the substrate as described above. Further, without providing the beam splitter film or the red reflection dichroic, they may be provided on both sides of the substrate. Examples of the optical system components provided on both sides of the substrate include a compensator.
Further, the antireflection film of the present invention can be used for lenses.

[Effects of the Invention] The antireflection film according to the present invention has an excellent reflection in a wide wavelength band, particularly for light obliquely incident on a substrate at an angle of 45 °, as will be apparent from examples described later. Shows the preventive effect. The optical product provided with the antireflection film of the present invention is effective as a light antireflection film when light is perpendicularly incident on the film surface, as in the related art.
When attached to the surface of an optical component that uses light obliquely incident at an angle of 45 ° to the substrate, it can be used over a wide wavelength band, compared to various conventionally known multilayer antireflection films. It shows a remarkably excellent anti-reflection effect, and as a result,
Significant reduction of undesired phenomena such as flare generation, double image formation, and color turbidity due to the back surface reflected light reflected on the back surface of the substrate is realized.

[Examples] (1) Seven-layer film type An optical glass substrate is made of SiO ₂ for odd-numbered layers, and Ti is used for even-numbered layers.
A multi-layer anti-reflection film using O ₂ is formed by vacuum evaporation so as to have a seven-layer structure as schematically shown in FIG. 2 and to have the optical film thickness shown in Table 1 respectively.

FIG. 3 shows the incident angle of the above-mentioned seven-layer type multilayer antireflection film.
45 is a spectrum showing a spectral reflectance characteristic at 45 °. From this spectrum, the above-mentioned seven-layer type multilayer antireflection film has a broad band from 400 nm to 700 nm for incident light at an incident angle of 45 °,
It can be seen that a very flat antireflection effect is exhibited.

(2) Nine-layer film type For the optical glass substrate, use SiO ₂ for the odd-numbered layers and Ti for the even-numbered layers.
A multi-layer anti-reflection film using O ₂ is formed by vacuum evaporation so as to have a nine-layer structure as schematically shown in FIG.

FIG. 5 shows the angles of incidence of the nine-layer type multilayer antireflection film.
45 is a spectrum showing a spectral reflectance characteristic at 45 °. From this spectrum, the 9-layer type multilayer anti-reflection film has a broad band from 400 nm to 700 nm for incident light at an incident angle of 45 °,
It can be seen that a very flat antireflection effect is exhibited.

(3) 11-layer film type SiO ₂ is used for the odd-numbered layers on the optical glass substrate, and Ti is used for the even-numbered layers.
A multi-layer anti-reflection film using O ₂ is formed by vacuum evaporation so as to have an 11-layer structure as schematically shown in FIG. 6 and to have the optical film thickness shown in Table 3 respectively.

FIG. 7 shows the angle of incidence of the 11-layer type multilayer antireflection film.
45 is a spectrum showing a spectral reflectance characteristic at 45 °. From this spectrum, the 11-layer type multilayer antireflection film has a broad band from 400 nm to 700 nm for incident light at an incident angle of 45 °,
It can be seen that a very flat antireflection effect is exhibited.

[Brief description of the drawings]

FIG. 1 is a schematic view showing the mode of use and operation of the antireflection film of the present invention. FIG. 2 is a configuration diagram of a seven-layer antireflection film of the present invention, and FIG. 3 is a spectrum showing typical spectral reflectance characteristics of the antireflection film. FIG. 4 is a configuration diagram of a nine-layer antireflection film of the present invention, and FIG. 5 is a spectrum showing typical spectral reflectance characteristics of the antireflection film. FIG. 6 is a configuration diagram of an 11-layer antireflection film of the present invention, and FIG. 7 is a spectrum showing typical spectral reflectance characteristics of the antireflection film. 1: Substrate 2: Beam splitter film or red reflective dichroic film 3: Incident light 4: Reflected light (surface reflected light) 5: Transmitted light 6: Backside reflected light 7: Anti-reflection film

Claims (3)

(57) [Claims] 1. An optical glass substrate having a refractive index (n _d ) with respect to d-line in the range of 1.50 to 1.54, and having a refractive index of 45 nm from the medium side.
An anti-reflection film made of a multilayer film exhibiting an anti-reflection effect with respect to light incident at an angle of ゜, wherein the multilayer film is a first anti-reflection film in order from the medium side to the substrate side.
And a seven-layer film named a second layer, a third layer, a fourth layer, a fifth layer, a sixth layer, and a seventh layer, wherein the even layers are higher than the refractive index of the substrate and in the range of 2.20 to 2.45. The odd-numbered layer is made of a low-refractive-index material having a refractive index lower than that of the substrate and having a refractive index in the range of 1.40 to 1.48, and the refractive index of the i-th layer is n. _i , and the optical thickness of the _i- th layer is n _i n
_{When d} (i is an integer of 1 to 7), the optical film thickness of each layer is as follows: 0.29012λ ₀ <n ₁ d ₁ <0.30806λ ₀ 0.16820λ ₀ <n ₂ d ₂ <0.18590λ ₀ 0.01805 λ ₀ <n ₃ d ₃ <0.02441λ ₀ 0.32446λ ₀ <n ₄ d ₄ <0.35150λ ₀ 0.10049λ ₀ <n ₅ d ₅ <0.10887λ ₀ 0.06516λ ₀ <n ₆ d ₆ <0.07496λ ₀ 0.57885λ ₀ <N ₇ d ₇ <0.66599λ ₀ where λ ₀ ; an antireflection film that satisfies the design dominant wavelength. 2. An optical glass substrate having a refractive index (n _d ) with respect to d-line in the range of 1.50 to 1.54, and having a refractive index of 45 from the medium side.
An anti-reflection film made of a multilayer film exhibiting an anti-reflection effect with respect to light incident at an angle of ゜.
Layer, second layer, third layer, fourth layer, fifth layer, sixth layer, seventh layer
A layer, an eighth layer, a ninth layer, and a nine-layer film, wherein the even-numbered layer is made of a high-refractive-index material having a refractive index higher than the refractive index of the substrate and in the range of 2.20 to 2.45. A low refractive index material having a refractive index lower than the refractive index of the substrate and in the range of 1.40 to 1.48; and the refractive index of the i-th layer is n _i , and the optical thickness of the i-th layer is n _{i
When di} (i is an integer of 1 to 9), the optical film thickness of each layer is as follows: 0.29600λ ₀ <n ₁ d ₁ <0.30800λ ₀ 0.16100λ ₀ <n ₂ d ₂ <0.17700λ ₀ 0.02050 λ ₀ <n ₃ d ₃ <0.02770λ ₀ 0.33300λ ₀ <n ₄ d ₄ <0.36100λ ₀ 0.10200λ ₀ <n ₅ d ₅ <0.11000λ ₀ 0.07440λ ₀ <n ₆ d ₆ <0.08060λ ₀ 0.26200λ _{0 <n 7 d 7 <0.29600λ 0} 0.00674λ 0 <n 8 d 8 <0.01250λ 0 0.20600λ 0 <n 9 d 9 <0.03100λ 0 However, lambda _0; antireflection film that satisfies the design dominant wavelength. 3. An optical glass substrate having a refractive index (n _d ) with respect to d-line in the range of 1.50 to 1.54.
An anti-reflection film made of a multilayer film exhibiting an anti-reflection effect with respect to light incident at an angle of ゜.
Layer, second layer, third layer, fourth layer, fifth layer, sixth layer, seventh layer
A high refractive index, wherein the even layer has a refractive index higher than the refractive index of the substrate and in the range of 2.20 to 2.45, comprising an eleven-layer film named a layer, an eighth layer, a ninth layer, a tenth layer, and an eleventh layer. made of a material, the odd layer is composed of a low refractive index material having a refractive index in the and scope of 1.40 to 1.48 lower than the refractive index of the substrate, and the refractive index of the i-th layer n _i and optical i-th layer, Target film thickness n _{i
When di} (i is an integer of 1 to 11), the optical film thickness of each layer is as follows: 0.2940λ ₀ <n ₁ d ₁ <0.3060λ ₀ 0.1540λ ₀ <n ₂ d ₂ <0.1700λ ₀ 0.0166 λ ₀ <n ₃ d ₃ <0.0248λ ₀ 0.3540λ ₀ <n ₄ d ₄ <0.3920λ ₀ 0.0923λ ₀ <n ₅ d ₅ <0.1020λ ₀ 0.0864λ ₀ <n ₆ d ₆ <0.0954λ ₀ 0.1490λ ₀ <N ₇ d ₇ <0.1830λ ₀ 0.0107λ ₀ <n ₈ d ₈ <0.0161λ ₀ 0.0242λ ₀ <n ₉ d ₉ <0.0725λ ₀ 0.0100λ ₀ <n ₁₀ d ₁₀ <0.0186λ ₀ 0.0279λ ₀ <n ₁₁ d _{11 <0.0836λ 0} However, lambda _0; antireflection film that satisfies the design dominant wavelength.