Optical thin films

Abstract

To provide a low-cost optical thin film that sufficiently suppresses deformation of a base material, has high performance, has a higher degree of freedom in designing, and can be formed easily.SOLUTION: An optical thin film 1 includes: at least one first film having a first material; at least one second film having a second material; and at least one third film having a third material. The first material is an oxide compound containing Ti and La. The first film has tensile stress. A refractive index of the first film and a refractive index of the second film are higher than a refractive index of the third film. The third film has compression stress. In the optical thin film 1, a change in surface accuracy of a film deposition target surface U when formed for the film deposition target surface U in one side in a plate-like base material 2 made of synthetic quartz glass that is 30 mm in a diameter and 3 mm in a thickness is equal to or less than 0.2λ with λ as 632.8 nm.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This invention relates to an optical thin film in which multiple films are stacked. [Background technology]

[0002] An optical laminate described in Japanese Patent Publication No. 59-10901 (Patent Document 1) is known. In this optical laminate, TiO2 vapor-deposited films and SiO2 vapor-deposited films are alternately laminated on a substrate that deforms due to the internal stress of the deposited films. Furthermore, in this optical laminate, the internal stress of the TiO2 vapor-deposited film and the internal stress of the SiO2 vapor-deposited film are balanced. In this optical laminate, the internal stress of the TiO2 vapor-deposited film, which has tensile stress, balances the internal stress of the SiO2 vapor-deposited film, thus suppressing substrate deformation.

[0003] Recently, the film density of one or more films in optical thin films having multiple films has been increased to improve the performance of the optical thin film. When the film density of the TiO2 film is increased, the tensile stress of the TiO2 film decreases, and furthermore, the tensile stress of the TiO2 film becomes compressive stress. Therefore, the suppression of substrate deformation by the optical laminate described above is not performed when a TiO2 film with a higher film density is used. In the optical thin film described in Japanese Patent Publication No. 2003-277911 (Patent Document 2), an oxide compound containing Ti and La is used as the material for the high refractive index film instead of the TiO2 film. In this case, the high refractive index film can have tensile stress while having a high film density. Therefore, by combining it with a low refractive index film made of SiO2 that has compressive stress, the optical thin film can be formed with high performance while suppressing deformation of the substrate. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 59-10901 [Patent Document 2] Japanese Patent Publication No. 2003-277911 [Overview of the project] [Problems that the invention aims to solve]

[0005] The optical thin film described above has a structure in which the optical thickness of the high refractive index film is three times that of the low refractive index film in order to balance the compressive stress of the low refractive index film. More specifically, in the film structure, the low refractive index film is indicated by "L", the high refractive index film is indicated by "H", and to the left of them, the design wavelength is λ D as λ D When the optical film thickness of the film is indicated by a number such that an optical film thickness equivalent to / 4 is 1, an optical film thickness twice that is 2, and so on, and the number representing the optical film thickness and "H" or "L" are arranged sequentially from left to right with the substrate side on the left, the above optical thin film has a repeating structure of (1L3H). Furthermore, the above-mentioned optical thin films have a structure in which a tensile stress film and a compressive stress film are always adjacent to each other. The design of the optical thin films described above is limited by such structures. For example, if a reflective film, i.e., a mirror, that reflects light in a predetermined wavelength range is formed from the above optical thin film, the wavelength range in which sufficient reflectivity is achieved becomes extremely narrow. Furthermore, the ease and cost of forming the above-mentioned optical thin films can be improved, especially since high-refractive-index optical thin films are thick.

[0006] Therefore, the main objective of this disclosure is to provide an optical thin film in which deformation of the substrate is sufficiently suppressed. Furthermore, another primary objective of this disclosure is to provide optical thin films with higher performance. Another main objective of this disclosure is to provide optical thin films with greater design flexibility. In addition, yet another main objective of this disclosure is to provide optical thin films that are easier and less expensive to form. [Means for solving the problem]

[0007] This specification discloses an optical thin film. This optical thin film may comprise one or more first films having a first material. The optical thin film is Different from the first material The optical thin film may comprise one or more second films having a second material. The optical thin film may comprise one or more third films having a third material. The first material may be an oxide compound containing Ti and La. The first film may have tensile stress. The refractive index of the first film and the second film may be higher than the refractive index of the third film. The third film may have compressive stress. [Effects of the Invention]

[0008] The main effect of this disclosure is to provide an optical thin film in which deformation of the substrate is sufficiently suppressed. Furthermore, another main effect of this disclosure is the provision of optical thin films with higher performance. Another key effect of this disclosure is that it provides optical thin films with greater design flexibility. In addition, yet another main effect of this disclosure is that optical thin films are provided that are easier to form and less expensive. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic diagram of an optical product including an optical thin film in this disclosure. [Figure 2] This is a schematic diagram relating to the warp δ of the substrate. [Figure 3] This graph shows the reflectance distributions of S-polarized and P-polarized light in the wavelength range including the design wavelength for Example 1. [Figure 4] This graph shows the reflectance distributions of S-polarized and P-polarized light in the wavelength range including the design wavelength for Example 2. [Figure 5] This graph shows the reflectance distributions of S-polarized and P-polarized light in the wavelength range including the design wavelength according to Example 3. [Figure 6] This graph shows the reflectance distributions of S-polarized and P-polarized light in the wavelength range including the design wavelength according to Example 4. [Figure 7]This graph shows the reflectance distributions of S-polarized and P-polarized light in the wavelength range including the design wavelength according to Example 5. [Figure 8] This graph shows the reflectance distributions of S-polarized and P-polarized light in the wavelength range including the design wavelength according to Example 6. [Figure 9] This graph shows the reflectance distributions of S-polarized and P-polarized light in the wavelength range including the design wavelength for Example 7. [Figure 10] This graph shows the reflectance distributions of S-polarized and P-polarized light in the wavelength range including the design wavelength for Example 8. [Figure 11] This graph shows the reflectance distributions of S-polarized and P-polarized light in the wavelength range including the design wavelength according to Example 9. [Figure 12] This graph shows the reflectance distributions of S-polarized and P-polarized light in the wavelength range including the design wavelength for Example 10. [Figure 13] This graph shows the reflectance distributions of S-polarized and P-polarized light in the wavelength range including the design wavelength for Example 11. [Figure 14] This graph shows the reflectance distributions of S-polarized and P-polarized light in the wavelength range including the design wavelength for Example 12. [Figure 15] This graph shows the reflectance distributions of S-polarized and P-polarized light in the wavelength range including the design wavelength for Example 13. [Figure 16] This graph shows the reflectance distributions of S-polarized and P-polarized light in the wavelength range including the design wavelength for Example 14. [Figure 17] This graph shows the reflectance distributions of S-polarized and P-polarized light in the wavelength range including the design wavelength for Example 15. [Figure 18] This graph shows the reflectance distributions of S-polarized and P-polarized light in the wavelength range including the design wavelength for Comparative Example 1. [Figure 19] This graph shows the reflectance distributions of S-polarized and P-polarized light in the wavelength range including the design wavelength for Comparative Example 2. [Figure 20] This graph shows the reflectance distributions of S-polarized and P-polarized light in the wavelength range including the design wavelength for Comparative Example 3. [Figure 21] This graph shows the reflectance distributions of S-polarized and P-polarized light in the wavelength range including the design wavelength for Comparative Example 4. [Figure 22] This graph shows the reflectance distributions of S-polarized and P-polarized light in the wavelength range including the design wavelength for Comparative Example 5. [Figure 23] This graph shows the reflectance distributions of S-polarized and P-polarized light in the wavelength range including the design wavelength for Comparative Example 6. [Figure 24] This graph shows the reflectance distributions of S-polarized and P-polarized light in the wavelength range including the design wavelength for Comparative Example 7. [Figure 25] This graph shows the GDDrs and GDDrp related to Example 1. [Figure 26] This graph shows GDDrs and GDDrp related to Example 2. [Figure 27] This graph shows the GDDrs and GDDrp related to Example 3. [Figure 28] This graph shows the GDDrs and GDDrp related to Example 4. [Figure 29] This graph shows the GDDrs and GDDrp related to Example 5. [Figure 30] This graph shows the GDDrs and GDDrp related to Example 6. [Figure 31] This graph shows the GDDrs and GDDrp related to Example 7. [Figure 32] This graph shows the GDDrs and GDDrp related to Example 8. [Figure 33] This graph shows the GDDrs and GDDrp related to Example 9. [Figure 34] This graph shows the GDDrs and GDDrp related to Example 10. [Figure 35] This graph shows the GDDrs and GDDrp related to Example 11. [Figure 36] This graph shows the GDDrs and GDDrp related to Example 12. [Figure 37] This graph shows the GDDrs and GDDrp related to Example 13. [Figure 38] This graph shows the GDDrs and GDDrp related to Example 14. [Figure 39] This graph shows the GDDrs and GDDrp related to Example 15. [Figure 40] This graph shows GDDrs and GDDrp for Comparative Example 1. [Figure 41] This graph shows GDDrs and GDDrp related to Comparative Example 2. [Figure 42] This graph shows GDDrs and GDDrp related to Comparative Example 3. [Figure 43] This graph shows GDDrs and GDDrp related to Comparative Example 4. [Figure 44] This graph shows GDDrs and GDDrp related to Comparative Example 5. [Figure 45] This graph shows GDDrs and GDDrp related to Comparative Example 6. [Figure 46] This graph shows the GDDrs and GDDrp related to Comparative Example 7. [Figure 47] This document shows graphs illustrating the change in surface accuracy, Rp width ratio, and GDDrp width ratio for Examples 1-6 and Comparative Examples 1-6, as well as tables showing the first pair ratio pT and the values ​​of t, h, and c in the physical film thickness ratio. [Modes for carrying out the invention]

[0010] Examples of embodiments relating to this disclosure will be described below with reference to the drawings as appropriate. The embodiments of this disclosure are not limited to these examples.

[0011] As shown in Figure 1, the optical thin film 1 according to this disclosure is formed on the outside of the surface of the substrate 2. The outside of the substrate 2 can also be called the anti-substrate side. The outside of the substrate 2 can also be called the environment side. If the environment is the atmosphere, the outside of the substrate 2 can also be called the atmosphere side. The surface of the substrate 2 on which the optical thin film 1 is placed is the deposition surface U. Note that multiple optical thin films 1 may be formed on a single substrate 2. In this case, the multiple optical thin films 1 may be formed on multiple parts of a single deposition surface U, or they may be formed on multiple deposition surfaces U.

[0012] An optical product P is formed from the optical thin film 1 and the substrate 2. The optical product P is, for example, a mirror, more specifically a galvanometer mirror or a low-dispersion mirror. Galvano mirrors can be used in the field of laser processing. The incident angle range with sufficient reflectivity in a galvano mirror is preferably sufficiently wide to facilitate laser path control. Therefore, the wavelength range with sufficient reflectivity in a galvano mirror needs to be sufficiently wide. Low-dispersion mirrors can be used in femtosecond laser optics. Femtosecond laser optics use ultrashort pulses on the order of femtoseconds, i.e., femtosecond pulses. A femtosecond is 10⁻¹⁰ -15 It is a second. The peak intensity of femtosecond pulsed light is, for example, 10 12The power output is approximately W (watt) or higher. Femtosecond pulsed light is composed of light of various wavelengths superimposed in a phase-aligned manner. That is, femtosecond pulsed light contains light across a wide wavelength range. Therefore, in a femtosecond laser optical system, the wavelength range with sufficiently low group velocity delay dispersion (GDD) and the wavelength range with sufficiently high reflectivity in the low-dispersion mirror must be sufficiently wide. When a femtosecond light pulse propagates through a medium where the speed of light differs for each wavelength, i.e., a medium where the group velocity of light is wavelength-dependent, light of one wavelength travels relatively faster than light of another wavelength in its propagation direction, or due to their superposition, the pulse width broadens or the peak intensity decreases. The shift in the speed of light depending on the wavelength due to the wavelength dependence of the group velocity of light is called chirp. The characteristics of femtosecond pulsed light are impaired by the amount by which the pulse width broadens or the peak intensity decreases due to chirp, so it is required that the occurrence of chirp in the low-dispersion mirror be suppressed. Therefore, the absolute value of the GDD for a low-dispersion mirror must be sufficiently small. If the optical product P is a mirror, the outside of the substrate 2 can be said to be either the incident medium side or the reflective medium side. Furthermore, the optical product P may include other components. For example, an interlayer may be placed between the film-forming surface U of the substrate 2 and the optical thin film 1. The interlayer may be a single layer or a multilayer. Alternatively, a surface layer may be placed on the outside of the optical thin film 1. The surface layer may be a single layer or a multilayer.

[0013] The base material 2 may be in the form of a plate or a block. If the base material 2 is in the form of a plate, it becomes a substrate. Substrate 2 is, for example, a substrate or a prism. The material of base material 2 may be, for example, optical glass BK7 (hereinafter simply referred to as "BK7"), quartz glass, glass ceramics, ceramics, crystals, or semiconductors. Note that the quartz glass may be synthetic quartz glass. Also, the glass ceramics may be clear ceramic. The coefficient of linear expansion of base material 2 is 2 × 10⁻⁶, from the viewpoint of suppressing its own deformation due to temperature changes. -6A value less than / ℃ is preferable.

[0014] Optical thin film 1 is a multilayer film containing multiple films. It is preferable that the optical thin film 1 contains at least three types of materials. Specifically, it is preferable that the optical thin film 1 contains a first material, a second material, and a third material. Preferably, in the optical thin film 1, some of the multiple films have compressive stress, and other parts have tensile stress.

[0015] It is preferable that an oxide compound containing Ti and La is used as the material for part or all of a film having tensile stress. The first material is preferably an oxide compound containing Ti and La. A film having the first material is the first film. Hereinafter, the oxide compound containing Ti and La may be referred to as TiO2-La2O3. TiO2-La2O3 films, which are made of TiO2-La2O3, are used as high refractive index films. TiO2-La2O3 is a mixture of Ti oxide and La oxide. TiO2-La2O3 films exhibit tensile stress even when the film density is sufficiently high. The TiO2-La2O3 film is the first film.

[0016] It is preferable that TiO2, an oxide of Ti, be used as part or all of the material of a film having compressive stress. The second material is preferably TiO2. A film having the second material is the second film. A TiO2 film, which is a film made of TiO2, is used as a high refractive index film. TiO2 is a titanium oxide, or titania. Alternatively, it is preferable that Ta2O5, an oxide of Ta, be used as another part or all of the material of the film having compressive stress. The second material may also be Ta2O5. The second film may also be a Ta2O5 film. A Ta2O5 film, which is a film made of Ta2O5, is used as a high refractive index film. Ta2O5 is tantalum oxide, or tantara. Alternatively, it is preferable that Nb2O5, an oxide of Nb, be used as another part or all of the material of the film having compressive stress. The second material may also be Nb2O5. The second film may also be an Nb2O5 film. An Nb2O5 film, which is a film made of Nb2O5, is used as a high refractive index film. Nb2O5 is a niobium oxide, or niobia. Alternatively, it is preferable that ZrO2, an oxide of Zr, be used as another part or all of the material of the film having compressive stress. The second material may also be ZrO2. The second film may also be a ZrO2 film. A ZrO2 film, which is a film made of ZrO2, is used as a high refractive index film. ZrO2 is a zirconium oxide, and is zirconia. Alternatively, it is preferable that HfO2, an oxide of Hf, be used as another part or all of the material of the film having compressive stress. The second material may also be HfO2. The second film may also be an HfO2 film. An HfO2 film, which is a film made of HfO2, is used as a high refractive index film. HfO2 is a hafnium oxide, or hafnia.

[0017] Furthermore, it is preferable that SiO2, an oxide of Si, be used as the material for part or all of another film having compressive stress. The third material is preferably SiO2. A film having the third material is the third film. An SiO2 film, which is a film made of SiO2, is used as a low refractive index film. SiO2 is a silicon oxide, and is silica.

[0018] The refractive indices of the first and second layers are higher than those of the third layer. In the optical thin film 1, it is preferable that the first or second film and the third film are arranged alternately. In the optical thin film 1, it is preferable that pairs of the first and third films, and pairs of the second and third films are used. In the optical thin film 1, if the film closest to the substrate 2 is the first or second film, it is preferable that the third film is arranged in an even-numbered position counting from the substrate 2 side. In the optical thin film 1, if the film closest to the substrate 2 is the third film, it is preferable that the third film is arranged in an odd-numbered position counting from the substrate 2 side. Furthermore, in the optical thin film 1, at least any two of the TiO2 film, Ta2O5 film, Nb2O5 film, ZrO2 film, and HfO2 film may be used in combination. For example, a TiO2 film may be used as the second - 1 film, and a ZrO2 film may be used as the second - 2 film. Also, a medium - refractive - index film may be further arranged.

[0019] Hereinafter, the film structure of the optical thin film 1 can be described in the following manner. That is, the TiO2 - La2O3 film is denoted as "H". Also, the TiO2 film is denoted as "T". Further, the SiO2 film is denoted as "L". Also, the Ta2O5 film is denoted as "A". Further, the Nb2O5 film is denoted as "B". Furthermore, the ZrO2 film is denoted as "Z". In addition, the HfO2 film is denoted as "F".

[0020] A number is arranged to the left of "H". The number to the left of "H" is the optical film thickness of the TiO2 - La2O3 film divided by λ D / 4. λ D is the design wavelength, for example, 645 nm (nanometers). A number is arranged to the left of "T". The number to the left of "T" is the optical film thickness of the TiO2 film divided by λ D / 4. A number is arranged to the left of "L". The number to the left of "L" is the optical film thickness of the SiO2 film divided by λ D / 4. A number is arranged to the left of "A". The number to the left of "A" is the optical film thickness of the Ta2O5 film divided by λ D / 4. A number is arranged to the left of "B". The number to the left of "B" is the optical film thickness of the Nb2O5 film divided by λ D / 4. Furthermore, hereinafter, no number is arranged to the left of "Z" and to the left of "F".

[0021] [[ID= The arrangement of the film in optical thin film 1 may be described by enclosing the predetermined pattern in parentheses and indicating the number of repetitions to the upper right of it, if it includes the repetition of a predetermined pattern. For example, "(1L2H) 3 The film structure of the optical thin film 1 shown in " is, in order from the substrate 2 side, λ D A SiO2 film having an optical thickness of 4, and 2×λ D This pattern consists of three repetitions of a TiO2-La2O3 film with an optical thickness of 4, and is equivalent to "1L2H1L2H1L2H". In this case, the number of optical thin films is 6. Also, "(1L2H) 3 The film structure of optical thin film 1, indicated by "1L", is equivalent to "1L2H1L2H1L2H1L". In this case, the number of films in optical thin film 1 is 7.

[0022] In optical thin film 1, from the viewpoint of reducing costs while obtaining sufficient performance, the number of TL pairs as the first pair is set to x T If we let y be the number of HL pairs as the second pair number, then p is the first pair number ratio, which is the ratio of the number of TL pairs to the total number of TL pairs and HL pairs. T It is preferable that this is between 0.09 and 0.55. Here, the ratio of the first pair p T is, p T =x T / (x T +y) is the number of TL pairs x T is the number of pairs of TiO2 films and adjacent SiO2 films on the outside in the film structure of optical thin film 1. The HL pair number y is the number of pairs of TiO2-La2O3 films and adjacent SiO2 films on the outside in the film structure of optical thin film 1.

[0023] Furthermore, in optical thin film 1, from the viewpoint of reducing costs while obtaining sufficient performance, if the total physical thickness of one or more TiO2 films is denoted as t, the total physical thickness of one or more TiO2-La2O3 films is denoted as h, and the total physical thickness of one or more SiO2 films is denoted as c, then the ratio of these, the physical thickness ratio t:h:c, is preferably t:h:c = 0.12~0.19:0.17~0.28:0.63~0.64. That is, in the physical thickness ratio t:h:c, the value of t is preferably in the range of 0.12 to 0.19, the value of h is preferably in the range of 0.17 to 0.28, and the value of c is preferably in the range of 0.63 to 0.64. The total physical thickness of the TiO2 films, t, is the second subtotal physical thickness. The total physical thickness of the TiO2-La2O3 films, h, is the first subtotal physical thickness. The total physical thickness of the SiO2 films, c, is the third subtotal physical thickness.

[0024] Furthermore, in optical thin film 1, from the viewpoint of reducing costs while obtaining sufficient performance, the number of AL pairs as the third pair is set to x A In this case, the second pair ratio p is the ratio of the number of AL pairs to the total number of AL pairs and HL pairs. A It is preferable that this is between 0.05 and 0.20. Here, the second pair ratio p A is, p A =x A / (x A +y) is the number of AL pairs x A This is the number of pairs of Ta2O5 films and adjacent SiO2 films on the outside of them that exist in the film structure of optical thin film 1.

[0025] Furthermore, in the optical thin film 1, from the viewpoint of reducing costs while obtaining sufficient performance, the number of BL pairs as the fourth pair is set to x B In this case, the third pair ratio p is the ratio of BL pairs to the total number of HL pairs. B It is preferable that this is between 0.05 and 0.20. Here, the ratio of the third pair p B is, p B =x B / (x B (+y) The number of BL pairs is xB This is the number of pairs of Nb2O5 films and adjacent SiO2 films on the outside of them that exist in the film structure of optical thin film 1.

[0026] In addition, it is preferable that in the film structure of the optical thin film 1, one of the TL pair, AL pair, BL pair, ZL pair, and FL pair is arranged in the outermost part. A TL pair is a pair consisting of a TiO2 film and an adjacent SiO2 film on its outer side. An AL pair is a pair consisting of a Ta2O5 film and an adjacent SiO2 film on its outside. A BL pair is a pair consisting of an Nb2O5 film and an adjacent SiO2 film on its outside. A ZL pair is a pair consisting of a ZrO2 film and an adjacent SiO2 film on its outside. An FL pair is a pair consisting of an HfO2 film and an adjacent SiO2 film on its outside. The refractive indices of the TiO2 film in the TL pair, the Ta2O5 film in the AL pair, the Nb2O5 film in the BL pair, the ZrO2 film in the ZL pair, and the HfO2 film in the FL pair are all greater than the refractive index of the TiO2-La2O3 film. Therefore, the performance of optical thin film 1 is improved. Furthermore, when any of the TL pair, AL pair, BL pair, ZL pair, and FL pair are arranged on the outermost side, the SiO2 film becomes the outermost film. Therefore, the durability of optical thin film 1 is improved. [Examples]

[0027] Next, embodiments of the present disclosure are shown. However, the examples provided are not intended to limit the scope of this disclosure. Furthermore, depending on how the present invention is interpreted, the examples may be substantial comparative examples that fall outside the scope of the disclosure, or the comparative examples may be substantial examples that fall within the scope of the disclosure.

[0028] As an example, a plate-shaped substrate 2 was prepared or simulated with various optical thin films 1 formed on one side. This side is the surface U to be coated. On the other hand, as a comparative example, a plate-shaped substrate 2 was prepared or simulated with various optical thin films similar in structure to the optical thin film 1 formed on one side. In both the example and the comparative example, the design wavelength λ D A mirror is envisioned that reflects light in the wavelength range including this wavelength, with this wavelength as the central wavelength. The material of base material 2 is at least one of optical glass BK7, synthetic quartz glass, or clear ceramic. Base material 2 is a circular plate with a diameter of 30 mm. The thickness of base material 2 is 3 mm.

[0029] Each optical thin film 1 in Examples 1 to 6 includes a TiO2-La2O3 film, a TiO2 film, and an SiO2 film. The design wavelength λ in each optical thin film 1 in Examples 1 to 6 D The wavelength is 645 nm. The film densities of the TiO2-La2O3 film, TiO2 film, and SiO2 film exceed those of conventional deposited films when deposited using methods such as ion-assisted evaporation or sputtering. The TiO2-La2O3 film, TiO2 film, and SiO2 film are high-density films. The film structure of the optical thin film 1 in Example 1 is (1T1L) 2 (1H1L) 7 The ratio is 1T2L. The number of films in optical thin film 1 of Example 1 is 20. The ratio of the first pair in optical thin film 1 of Example 1 is p. T is, p T =3 / (3+7)=0.30. The physical film thickness ratio t:h:c in the optical thin film 1 of Example 1 is t:h:c=0.099:0.271:0.631. The optical thin film 1 of Example 1 was actually formed on each of the substrates 2 of optical glass BK7, synthetic quartz glass, and clear ceramic. Hereinafter, the combination of the substrate 2 of optical glass BK7 and the optical thin film 1 of Example 1 may be referred to as Example 1-B. Also, the combination of the substrate 2 of synthetic quartz glass and the optical thin film 1 of Example 1 may be referred to as Example 1-Q. Furthermore, the combination of the substrate 2 of clear ceramic and the optical thin film 1 of Example 1 may be referred to as Example 1-C. Other examples and comparative examples may be similarly described. The film structure of optical thin film 1 in Example 2 is (1T1L) 3 (1H1L) 7 The ratio is 1T2L. The number of films in optical thin film 1 of Example 2 is 22. The ratio of the first pair in optical thin film 1 of Example 2 is p. T The ratio is 0.36. The physical film thickness ratio t:h:c in the optical thin film 1 of Example 2 is t:h:c = 0.120:0.248:0.631. Example 2 was actually formed on each of the substrates 2 of optical glass BK7, synthetic quartz glass, and clear ceramic, i.e., Examples 2-B, 2-Q, and 2-C. The film structure in optical thin film 1 of Example 3 is (1T1L) 3 (1H1L) 7 The ratio is 1T1L1T2L. The number of films in optical thin film 1 of Example 3 is 24. The ratio of the first pair in optical thin film 1 of Example 3 is p. T The ratio is 0.42. The physical film thickness ratio t:h:c in optical thin film 1 of Example 3 is t:h:c = 0.139:0.229:0.632. Examples 3-B, 3-Q, and 3-C were actually formed.

[0030] The film structure in optical thin film 1 of Example 4 is (1T1L) 3 (1H1L) 5 (1T1L) 2 The ratio is 1T2L. The number of films in optical thin film 1 of Example 4 is 22. The ratio of the first pair in optical thin film 1 of Example 4 is p. T The value is 0.55. The physical film thickness ratio t:h:c in optical thin film 1 of Example 4 is t:h:c = 0.183:0.179:0.638. Examples 4-B, 4-Q, and 4-C were actually formed. The film structure in optical thin film 1 of Example 5 is (1T1L) 4 (1H1L) 6 The ratio is 1H2L. The number of films in optical thin film 1 of Example 5 is 22. The ratio of the first pair in optical thin film 1 of Example 5 is p. TThe value is 0.36. The physical film thickness ratio t:h:c in optical thin film 1 of Example 5 is t:h:c = 0.120:0.248:0.631. Example 5 was simulated for Examples 5-B and 5-Q. The film structure of optical thin film 1 in Example 6 is (1H1L) 7 (1T1L) 3 The ratio is 1T2L. The number of films in optical thin film 1 of Example 6 is 22. The ratio of the first pair in optical thin film 1 of Example 6 is p. T The value is 0.36. The physical film thickness ratio t:h:c in optical thin film 1 of Example 6 is t:h:c = 0.120:0.248:0.631. Example 6 was simulated for Examples 6-B and 6-Q.

[0031] Each of the optical thin films 1 in Examples 7 and 8 includes a TiO2-La2O3 film, a Ta2O5 film, and an SiO2 film. The design wavelength λ in each of the optical thin films 1 in Examples 7 and 8 D It is 645nm. The film structure in optical thin film 1 of Example 7 is (1H1L) 14 (1A1L) 2 The ratio is 1A2L. The number of films in optical thin film 1 of Example 7 is 34. The ratio of the second pair in optical thin film 1 of Example 7 is p. A The value is 0.18. Example 7 was simulated for Examples 7-B, 7-Q, and 7-C. The film structure in optical thin film 1 of Example 8 is (1H1L) 16 The ratio is 1A2L. The number of films in optical thin film 1 of Example 8 is 34. The ratio of the second pair in optical thin film 1 of Example 8 is p. A The value is 0.06. Example 8 was simulated for Examples 8-B, 8-Q, and 8-C.

[0032] The optical thin film 1 of Example 9 includes a TiO2-La2O3 film, a TiO2 film, and an SiO2 film. The design wavelength λ in the optical thin film 1 of Example 9 D It is 645nm. The film structure in optical thin film 1 of Example 9 is (1H1L) 10The ratio is 1T2L. The number of films in optical thin film 1 of Example 9 is 22. The ratio of the first pair in optical thin film 1 of Example 9 is p. T The value is 0.09. Example 9 was simulated for Examples 9-B, 9-Q, and 9-C.

[0033] Each optical thin film 1 in Examples 10 and 11 includes a TiO2-La2O3 film, an Nb2O5 film, and an SiO2 film. The design wavelength λ in each optical thin film 1 in Examples 10 and 11 D It is 645nm. The film structure of optical thin film 1 in Example 10 is (1H1L) 14 (1B1L) 2 The ratio is 1B2L. The number of films in optical thin film 1 of Example 10 is 34. The ratio of the third pair in optical thin film 1 of Example 10 is p. B The value is 0.18. Example 10 was simulated for Examples 10-B, 10-Q, and 10-C. The film structure of optical thin film 1 in Example 11 is (1H1L) 16 The ratio is 1B2L. The number of films in optical thin film 1 of Example 11 is 34. The ratio of the third pair in optical thin film 1 of Example 11 is p. B The value is 0.06. Example 11 was simulated for Examples 11-B, 11-Q, and 11-C.

[0034] The optical thin film 1 of Comparative Example 1 includes a TiO2 film and an SiO2 film. Comparative Example 1 Optics Design wavelength λ in thin film 1 D Its wavelength is 633 nm. The film structure of the optical thin film 1 in Comparative Example 1 is (1T1L) 7 The ratio is 1T2L. The number of films in optical thin film 1 of Comparative Example 1 is 16. The ratio of the first pair in optical thin film 1 of Comparative Example 1 is p. T is, p T =8 / (8+0)=1. The physical film thickness ratio t:h:c in the optical thin film 1 of Comparative Example 1 is t:h:c=0.337:0:0.663. Comparative Example 1 was actually formed for Comparative Examples 1-B, 1-Q, and 1-C.

[0035] Each optical thin film 1 in Comparative Examples 2 to 6 includes a TiO2-La2O3 film and an SiO2 film. The design wavelength λ in the optical thin film 1 of Comparative Example 2 D The design wavelength λ in each optical thin film 1 of Comparative Examples 3-6 D It is 645nm. The film structure of the optical thin film 1 in Comparative Example 2 is (1H1L) 11 The ratio is 1H2L. The number of films in optical thin film 1 of Comparative Example 2 is 24. The ratio of the first pair in optical thin film 1 of Comparative Example 2 is p. T is, p T =0 / (0+12)=0. The physical film thickness ratio t:h:c in the optical thin film 1 of Comparative Example 2 is t:h:c=0:0.383:0.617. Comparative Example 2 was actually formed for Comparative Examples 2-B and 2-Q. The film structure of the optical thin film 1 in Comparative Example 3 is (1.5H0.5L). 14 The concentration is 1.5H1L. The number of films in optical thin film 1 of Comparative Example 3 is 30. The ratio of the first pair in optical thin film 1 of Comparative Example 3 is p. T The value is 0. The physical film thickness ratio t:h:c in the optical thin film 1 of Comparative Example 3 is t:h:c = 0:0.655:0.345. Comparative Example 3 was simulated for Comparative Examples 3-B, 3-Q, and 3-C.

[0036] The film structure of the optical thin film 1 in Comparative Example 4 is (0.5H1.5L). 14 The amount is 0.5H2L. The number of films in optical thin film 1 of Comparative Example 4 is 30. The ratio of the first pair in optical thin film 1 of Comparative Example 4 is p. T The value is 0. The physical film thickness ratio t:h:c in optical thin film 1 of Comparative Example 4 is t:h:c = 0:0.180:0.820. Comparative Example 4 was simulated for Comparative Examples 4-B, 4-Q, and 4-C. The film structure of the optical thin film 1 in Comparative Example 5 is (1.5H0.5L). 6 1.5H1L (0.5H1.5L) 7 The amount is 0.5H2L. The number of films in optical thin film 1 of Comparative Example 5 is 30. The ratio of the first pair in optical thin film 1 of Comparative Example 5 is p. Tis 0. The physical film thickness ratio t:h:c in the optical thin film 1 of Comparative Example 5 is t:h:c = 0:0.372:0.628. Comparative Example 5 was simulated for Comparative Examples 5-B, 5-Q, and 5-C. The film structure in the optical thin film 1 of Comparative Example 6 is (1.5H0.5L) 5 1.5H1L(0.5H1.5L) 8 0.5H2L. The number of films in the optical thin film 1 of Comparative Example 6 is 30. The ratio p of the number of the first pairs in the optical thin film 1 of Comparative Example 6 T is 0. The physical film thickness ratio t:h:c in the optical thin film 1 of Comparative Example 6 is t:h:c = 0:0.342:0.658. Comparative Example 6 was simulated for Comparative Examples 6-B, 6-Q, and 6-C.

[0037] The optical thin film 1 of Comparative Example 7 includes a Ta2O5 film and a SiO2 film. The design wavelength λ in the optical thin film 1 of Comparative Example 7 D is 645 nm. The film structure in the optical thin film 1 of Comparative Example 7 is (1A1L) 16 1A2L. The number of films in the optical thin film 1 of Comparative Example 7 is 34. The ratio p of the number of the second pairs in the optical thin film 1 of Comparative Example 7 A is 1. Comparative Example 7 was simulated for Comparative Examples 7-B, 7-Q, and 7-C.

[0038] The optical thin film 1 of Example 12 includes a TiO2-La2O3 film, a TiO2 film, and a SiO2 film. The design wavelength λ in the optical thin film 1 of Example 12 D is 645 nm. The film structure in the optical thin film 1 of Example 12 is (1H1L) 3 (1T1L) 7 1T2L. The number of films in the optical thin film 1 of Example 12 is 22. The ratio p of the number of the first pairs in the optical thin film 1 of Example 12 T is 0.73. Example 12 was simulated for Examples 12-B, 12-Q, and 12-C.

[0039] The optical thin film 1 of Example 13 includes a TiO2-La2O3 film, a Ta2O5 film, and an SiO2 film. The design wavelength λ in the optical thin film 1 of Example 13 D It is 645nm. The film structure in optical thin film 1 of Example 13 is (1H1L) 11 (1A1L) 5 The ratio is 1A2L. The number of films in optical thin film 1 of Example 13 is 34. The ratio of the second pair in optical thin film 1 of Example 13 is p. A The value is 0.35. Example 13 was simulated for Examples 13-B, 13-Q, and 13-C.

[0040] The optical thin film 1 of Example 14 includes a TiO2-La2O3 film, a TiO2 film, and an SiO2 film. The design wavelength λ in the optical thin film 1 of Example 14 D It is 645nm. The film structure of optical thin film 1 in Example 14 is (1H1L) 4 (1T1L) 6 The ratio is 1T2L. The number of films in optical thin film 1 of Example 14 is 22. The ratio of the first pair in optical thin film 1 of Example 14 is p. T The value is 0.64. Example 14 was simulated for Examples 14-B, 14-Q, and 14-C.

[0041] Example 15 Optics Thin film 1 includes a TiO2-La2O3 film, an Nb2O5 film, and an SiO2 film. Example 15 Optics Design wavelength λ in thin film 1 D It is 645nm. The film structure of optical thin film 1 in Example 15 is (1H1L) 11 (1B1L) 5 It is 1B2L. The number of films in optical thin film 1 of Example 15 is 34. The ratio of the third pair in optical thin film 1 of Example 15 is p B The value is 0.35. Example 15 was simulated for Examples 15-B, 15-Q, and 15-C.

[0042] The formation or simulation of the TiO2-La2O3 films in each optical thin film 1 of Examples 1-15 and Comparative Examples 2-6 was performed using Merck KGaA's "Substance H4". Hereinafter, TiO2-La2O3 will be simply referred to as "H4".

[0043] Then, the surface accuracy changes were measured or calculated for the formed or simulated Examples 1-Q to 15-Q and Comparative Examples 1-Q to 7-Q. A change in surface accuracy is a change in surface accuracy. Surface accuracy is the difference in height between the highest and lowest points of the surface roughness on the film deposition surface U of the substrate 2. The height direction is perpendicular to the film deposition surface U without considering the roughness, or to the film deposition surface U with the roughness averaged out. Surface accuracy can also be called the peak-valley value, or PV value. Surface accuracy is often measured using a He-Ne laser interferometer. The wavelength λ of the He-Ne laser is 632.8 nm. Surface accuracy is generally expressed in units of λ = 632.8 nm. That is, surface accuracy is generally expressed as a multiple of λ = 632.8 nm. For example, if the surface accuracy is 63.28 nm, it is expressed as 0.1λ. The sign of surface accuracy is often negative for convex surfaces and positive for concave surfaces, and this follows below. At the current level of polishing, a surface accuracy of 0.25λ or less is considered high-precision polishing. In Examples 1-15 and Comparative Examples 1-6, the film deposition target surface U of the substrate 2 was polished to 0.25λ or less in its standalone state before the formation of the optical thin film 1.

[0044] The surface accuracy of the optical thin film 1 in the optical product P changes from the surface accuracy of the target surface U before the formation of the optical thin film 1, due to the formation of the stressed optical thin film 1 on the target surface U. The formation of the stressed optical thin film 1 on the target surface U causes the plate-shaped substrate 2 to warp, and the surface accuracy of the outer surface of the optical thin film 1 changes from the surface accuracy of the target surface U before the formation of the optical thin film 1. The curvature δ of the plate-shaped substrate 2, i.e., the substrate, is shown in Figure 2. The warp δ of the substrate can be calculated by the following procedure. Furthermore, the description in Japanese Patent Publication No. 7188754, concerning a method for predicting the warp of optical products, can be referenced.

[0045] Specifically, regarding the stress of a single-layer thin film on a circular substrate, Stoney's equation is solved for the radius of curvature r, and the following equation (1) is obtained. Here, σ is the internal stress of the thin film, d is the physical thickness of the thin film, and E s The Young's modulus of the substrate is v. s ∫ is the Poisson's ratio of the substrate, b is the thickness of the substrate, l is the radius of the substrate, r is the radius of curvature of the substrate, and δ0 is the warpage of the substrate before film deposition. The signs of the various stresses are positive for tensile stress and negative for compressive stress. In the case of tensile stress, the substrate becomes convex towards the optical thin film 1, as shown in Figure 2. In the case of compressive stress, the plate-shaped substrate 2 becomes convex on the side opposite to the optical thin film 1.

[0046]

number

[0047] Furthermore, in order to extend the calculation for a single-layer optical thin film to a multilayer optical thin film 1 having a high refractive index film and a low refractive index film, the internal stress σ is given by the true stress σ as shown in equation (2) below. i It is understood separately as thermal stress. Thermal stress is the coefficient of linear expansion α of the optical thin film 1 in the optical product P. f And the coefficient of linear expansion α of the base material 2 s It is proportional to the difference. True stress σ i This is determined by the material of the membrane. E f The Young's modulus of the multilayer optical thin film 1 is v f θ is the Poisson's ratio of the multilayer optical thin film 1, T is the temperature at which the warpage δ was measured, and τ is the temperature at which the warpage δ was measured. fit T d The temperature during the formation of the multilayer optical thin film 1 is τ. fit This is one of the fitting parameters determined by fitting using multiple sample values ​​in order to improve the accuracy of calculating the curvature δ.

[0048]

number

[0049] And, true stress σ i This can be understood as an approximate mean true stress, as shown in equation (3) below. fit σ H The true stress in the material of the high refractive index film is a fit To further improve the accuracy of calculating the curvature δ, one of the fitting parameters determined by fitting using multiple sample values ​​is b. fit σ L b is the true stress in the material of the low refractive index film. fit To further improve the accuracy of calculating the curvature δ, one of the fitting parameters determined by fitting using multiple sample values ​​is d. H d is the total film thickness of the high refractive index film in the multilayer optical thin film 1. L This is the total film thickness of the low refractive index film in the multilayer optical thin film 1.

[0050]

number

[0051] Also, Young's modulus E f This is understood as the approximate average Young's modulus, as shown in equation (4) above. H The Young's modulus of a high refractive index film is E L This is the Young's modulus of a low refractive index film. Furthermore, Poisson's ratio v f This can be understood as an approximate mean Poisson's ratio, as shown in equation (5) above. H The Poisson's ratio of the high refractive index film, v L This is the Poisson's ratio of a low refractive index film. In addition, the coefficient of linear expansion α f α is understood as an approximate mean coefficient of linear expansion as shown in equation (6) above. H α is the coefficient of linear expansion of a high refractive index film. L This is the coefficient of linear thermal expansion of a low refractive index film.

[0052] Various fitting parameters a fit ,b fit ,τfit The value was determined such that f in equation (7) below is minimized, where N is the number of samples and δ m,j δ is the measured value of the warp in the j-th sample. c This is the calculated value of warping, calculated using the characteristic and conditional values ​​assumed to be present in the j-th sample. Various fitting parameters a are chosen to minimize f in equation (7). fit ,b fit ,τ fit Once determined, the warp δ of the substrate can be calculated with sufficient accuracy using equations (1) to (6). Furthermore, this calculation of warp δ can be applied to substrates 2 other than circular substrates.

[0053]

number

[0054] If the warpage δ of the substrate is measured or calculated, the surface accuracy after the formation of the optical thin film 1 can be determined, and the change in surface accuracy after the formation of the optical thin film 1 can be determined. The various data used in calculating the change in surface accuracy using the warp δ of the substrate are as follows, and are summarized in Tables 1 and 2.

[0055] The coefficient of linear expansion of TiO2 (1 / °C, the same applies below) is 4.4E-6. "E-6" is the number to its left plus 10. -6 This means multiplying by 10. Similarly, for any integer a, "Ea" is multiplied by the number to its left. -a This means multiplying by . The coefficient of thermal expansion of H4 is 4.4E-6. The coefficient of thermal expansion of SiO2 is 2.1E-6.

[0056] The Young's modulus (GPa, gigapascals, hereafter the same) of TiO2 is 136. The Young's modulus of H4 is 136. The Young's modulus of SiO2 is 87. The Poisson's ratio of TiO2 is 0.27. The Poisson's ratio of H4 is 0.27. The Poisson's ratio of SiO2 is 0.11.

[0057] The coefficient of thermal expansion of Clear Ceram is 0. The coefficient of thermal expansion of synthetic quartz glass is 5.9E-7. The coefficient of thermal expansion of optical glass BK7 is 9.4E-6. The Young's modulus of Clear Ceram is 90.0. The Young's modulus of synthetic quartz glass is 72.0. The Young's modulus of optical glass BK7 is 78.6. The Poisson's ratio of Clear Serum is 0.25. The Poisson's ratio of Synthetic Quartz Glass is 0.17. The Poisson's ratio of Optical Glass BK7 is 0.21.

[0058] [Table 1]

[0059] In the formation and simulation of optical thin film 1, which includes a TiO2-La2O3 film (H4 film in this case), a TiO2 film, and an SiO2 film, a deposition temperature of 81.7°C is used. In this case, the true stress (MPa, megapascals, hereafter the same) of the TiO2 film is -14.7. The sign of the true stress is positive for tensile stress and negative for compressive stress, similar to the sign of the warpage δ. The true stress of the H4 film is 277.9. The true stress of the SiO2 film is -173.6. In the formation and simulation of optical thin film 1, which includes an H4 film, a Ta2O5 film, and a SiO2 film, a deposition temperature of 190°C is used. In this case, Ta 2 O 5 film The true stress of the H4 film is -145.4. The true stress of the SiO2 film is 252.8. The true stress of the SiO2 film is -207.0. In the formation and simulation of optical thin film 1, which includes an H4 film, an Nb2O5 film, and an SiO2 film, a deposition temperature of 146°C is used. In this case, Nb 2 O 5 film The true stress of the H4 film is -171.3. The true stress of the SiO2 film is 252.8. The true stress of the SiO2 film is -192.2.

[0060] [Table 2]

[0061] The surface accuracy change for Example 1-Q was 0.036λ. The surface accuracy change for Example 2-Q was -0.011λ. The surface accuracy change for Example 3-Q was -0.052λ. The surface accuracy change for Example 4-Q was -0.104λ. The surface accuracy change for Example 5-Q was -0.062λ. The surface accuracy change for Example 6-Q was -0.062λ.

[0062] The surface accuracy change for Example 7-Q was -0.075λ. The surface accuracy change for Example 8-Q was -0.011λ. The surface accuracy change for Example 9-Q was 0.047λ. The surface accuracy change for Example 10-Q was -0.081λ. The surface accuracy change for Example 11-Q was -0.012λ.

[0063] The surface accuracy change for Example 12-Q was -0.170λ. The surface accuracy change for Example 13-Q was -0.172λ. The surface accuracy change for Example 14-Q was -0.143λ. The surface accuracy change for Example 15-Q was -0.185λ.

[0064] The surface accuracy change for Comparative Example 1-Q was -0.215λ. The surface accuracy change for Comparative Example 2-Q was 0.127λ. The surface accuracy change for Comparative Example 3-Q was 0.472λ. The surface accuracy change for Comparative Example 4-Q was -0.308λ. The surface accuracy change for Comparative Example 5-Q was 0.052λ. The surface accuracy change for Comparative Example 6-Q was -0.002λ. The surface accuracy change for Comparative Example 7-Q was -0.527λ.

[0065] These surface accuracy changes are shown in the left-hand section of Table 3.

[0066] [Table 3]

[0067] Furthermore, for the formed or simulated Examples 1-15 and Comparative Examples 1-7, the design wavelength λ DThe R of the reflectance of S-polarized light in the wavelength range including s of The reflectance R of distributed and P-polarized light p The distributions of each were measured or calculated. Figures 3-17 show the reflectance distributions for Examples 1-15. Figures 18-24 show the reflectance distributions for Comparative Examples 1-7. The wavelength range shown in Figures 3-24 is 540 nm to 760 nm. Furthermore, the reflection of the high-reflectivity band in the light incident on the optical product P is brought about by the optical thin film 1, not the substrate 2. Therefore, each optical thin film 1 in Examples 1 to 15 and Comparative Examples 1 to 7 exhibits the same reflectivity distribution regardless of the material of the substrate 2.

[0068] Furthermore, the reflectance R of P-polarized light in each optical thin film 1 of Examples 1 to 15 and Comparative Examples 1 to 7 p From the distribution of R p The width was determined. R p The width is the size of the wavelength range where the reflectance is 50% or higher. Also, each R p Design width λ D R corresponds to the quotient obtained by dividing by p The width ratio was determined. R p The width ratio is R p Width ratio=R p Width / design wavelength λ D That is the case. These R p The width ratio is shown in the center of Table 3 above.

[0069] R in Example 1 p The width ratio was 0.212. R in Example 2 p The width ratio was 0.212. R in Example 3 p The width ratio was 0.250. R in Example 4 p The width ratio was 0.269. R in Example 5 p The width ratio was 0.222. R in Example 6 p The width ratio was 0.225.

[0070] R in Example 7 p The width ratio was 0.185. R in Example 8p The width ratio was 0.184. R in Example 9 p The width ratio was 0.202. R in Example 10 p The width ratio was 0.188. R in Example 11 p The width ratio was 0.184.

[0071] R in Example 12 p The width ratio was 0.264. R in Example 13 p The width ratio was 0.193. R in Example 14 p The width ratio was 0.257. R in Example 15 p The width ratio was 0.207.

[0072] R in Comparative Example 1 p The width ratio was 0.287. R of Comparative Example 2 p The width ratio was 0.198. R of Comparative Example 3 p The width ratio was 0.143. R of Comparative Example 4 p The width ratio was 0.146. R of Comparative Example 5 p The width ratio was 0.144. R of Comparative Example 6 p The width ratio was 0.146. R of Comparative Example 7 p The width ratio was 0.219.

[0073] Furthermore, for the simulated Examples 1-15 and Comparative Examples 1-7, the design wavelength λ D GDD in the wavelength range including rs and GDD rp However, each was calculated. In the above, even in the case where the optical product P was actually formed, GDD rs and GDD rp This was calculated through simulation. GDD is the Group Delay Dispersion, and it is an indicator of the phase shift after reflection relative to the phase before reflection when reflecting pulsed light on the order of femtoseconds. GDD = -∂ 2 φ / ∂ω 2Here, ω is the angular frequency and φ is the reflection phase. φ is a function of ω. The unit of GDD is fs. 2 That is, it is the square of a femtosecond. The smaller the absolute value of GDD, the more the phase shift is suppressed. Furthermore, the description of GDD in Japanese Patent Publication No. 7195022, by the present inventor, can be considered. GDD r This is the GDD when reflected. In the embodiments and comparative examples of this application, the GDD when transmitted is not of interest, so GDD and GDD r This can be interpreted in a similar sense. GDD rs This is the GDD of S-polarized light when reflected. rp This is the GDD of P-polarized light when reflected.

[0074] Figures 25-39 show the GDDs of Examples 1-15. rs and GDD rp This is shown. Figures 40-46 show the GDD of Comparative Examples 1-7. rs and GDD rp This is shown. Note that the wavelength range shown in Figures 25-46 is between 540 nm and 760 nm. Furthermore, the reflection of the high-reflectivity band in the light incident on the optical product P is brought about by the optical thin film 1, not the substrate 2. Therefore, each optical thin film 1 in Examples 1-15 and Comparative Examples 1-7 is the same regardless of the material of the substrate 2, and the GDD rs Distribution and each GDD rp It exhibits a distribution.

[0075] Furthermore, in each optical thin film 1 of Examples 1-15 and Comparative Examples 1-7, GDD rp From the distribution, GDD rp The width was determined. GDD rp The width is, GDD rp of This is the magnitude of the wavelength range where the absolute value is 50 or less. Also, GDD rp Design width λ D GDD equivalent to the quotient obtained by dividing by rp The width ratio was determined. GDD rp The width ratio is GDDrp Width ratio = GDD rp Width / design wavelength λ D That is the case. These GDDs rp The width ratio is as shown in Table 3 above. right side It is shown here.

[0076] GDD of Example 1 rp The width ratio was 0.147. GDD of Example 2 rp The width ratio was 0.142. GDD of Example 3 rp The width ratio was 0.146. GDD of Example 4 rp The width ratio was 0.162. GDD of Example 5 rp The width ratio was 0.140. GDD of Example 6 rp The width ratio was 0.177.

[0077] GDD of Example 7 rp The width ratio was 0.133. GDD of Example 8 rp The width ratio was 0.124. GDD of Example 9 rp The width ratio was 0.143. GDD of Example 10 rp The width ratio was 0.141. GDD of Example 11 rp The width ratio was 0.126.

[0078] GDD in Example 12 rp The width ratio was 0.204. GDD of Example 13 rp The width ratio was 0.145. GDD of Example 14 rp The width ratio was 0.202. GDD of Example 15 rp The width ratio was 0.163.

[0079] GDD in Comparative Example 1 rp The width ratio was 0.224. GDD of Comparative Example 2 rp The width ratio was 0.134. GDD of Comparative Example 3 rp The width ratio was 0.078. GDD of Comparative Example 4 rp The width ratio was 0.081. GDD of Comparative Example 5 rpThe width ratio was 0.081. GDD of Comparative Example 6 rp The width ratio was 0.081. GDD of Comparative Example 7 rp The width ratio was 0.158.

[0080] The characteristics of Examples 1-15 and Comparative Examples 1-7 are described below. Figure 47 shows the change in surface accuracy divided by λ, i.e., the amount of change, for optical thin film 1 relating to at least one of a TiO2-La2O3 film (H4 film) and a TiO2 film in Examples 1 to 6 and Comparative Examples 1 to 6, and R p Width ratio and GDD rp This is a graph showing the width ratio. In Figure 47, the change in surface accuracy for substrate 2 other than quartz is also shown. The horizontal axis in Figure 47 is arranged from left to right in order of the largest change in surface accuracy. A positive change in surface accuracy corresponds to tensile stress, and a negative change in surface accuracy corresponds to compressive stress. In the graph of Figure 47, the right vertical axis is R p Width ratio and GDD rp The various width ratios are collectively referred to as "bandwidth / center wavelength." Bandwidth corresponds to the width of the wavelength range, and the center wavelength is the design wavelength λ. D It corresponds to. Furthermore, Figure 47 shows the proportion of the first pair in each optical thin film 1, p. T The values ​​of t, h, and c in the physical film thickness ratio are shown.

[0081] The optical thin film 1 of Comparative Example 1 is an alternating layer of two materials: a TiO2 film and an SiO2 film. In the optical thin film 1 of Comparative Example 1, R p Width ratio and GDD rp Both the width-to-weight ratio is sufficiently large, and the wavelength range in which incident light is sufficiently reflected, as well as the wavelength range in which chirp is suppressed, are sufficiently wide. However, the surface accuracy changes significantly due to compressive stress. Here, one criterion for a desirable surface accuracy change is that its absolute value is 0.125λ or less. This criterion of an absolute value of 0.125λ or less for the surface accuracy change will be referred to as the first surface accuracy change criterion below. Furthermore, one criterion for a desirable surface accuracy change that is more gradual than the first surface accuracy change criterion is that its absolute value is 0.2λ or less. This criterion of an absolute value of 0.2λ or less for the surface accuracy change will be referred to as the second surface accuracy change criterion below. Furthermore, a preferred R p As one criterion for width ratio, R p One characteristic is that the width ratio is 0.15 or higher. Also, a favorable GDD rp As one criterion for width ratio, GDD rp One example is that the width ratio is 0.10 or greater. Furthermore, the first surface accuracy change criterion and R p Width ratio and GDD rp It is not mandatory to satisfy all of the width ratio criteria. When assessing the characteristics of Examples 1-15 and Comparative Examples 1-7, even if optical thin film 1 does not meet any of the criteria, the extent to which optical thin film 1 approaches these criteria will be taken into consideration as appropriate. In addition, factors other than these criteria will also be taken into consideration as appropriate. In the optical thin film 1 of comparative example 1, R p Standards for width ratio and GDD rp While both width ratio criteria are fully met, the first surface accuracy change criterion falls far short. In comparative example 1, optical thin film 1 also fails to meet the second surface accuracy change criterion.

[0082] Optical thin film 1 in Comparative Examples 2-6 is an alternating layer of two materials: an H4 film and an SiO2 film. In comparative example 2, optical thin film 1, R p Width ratio and GDD rp Both width ratios meet the criteria. In contrast, the optical thin film 1 of Comparative Example 2 slightly fails to meet the first surface accuracy change criterion. The optical thin film 1 of Comparative Example 2 meets the second surface accuracy change criterion. In the optical thin film 1 of Comparative Example 3, R p Width ratio and GDD rp The width ratio does not meet the standard, Rp and GDD rp Each wavelength range is narrow. Furthermore, in the optical thin film 1 of Comparative Example 3, the first surface accuracy change criterion and the second surface accuracy change criterion are significantly not met. In comparative example 4, optical thin film 1, R p Width ratio and GDD rp The width ratio does not meet the standard, R p and GDD rp Each wavelength range is narrow. Furthermore, in the optical thin film 1 of Comparative Example 4, the first surface accuracy change criterion and the second surface accuracy change criterion are largely not met. In the optical thin film 1 of Comparative Example 5, although the first surface accuracy change criterion is sufficiently met, R p Width ratio and GDD rp The width ratio does not meet the standard, R p and GDD rp Each wavelength range is narrow. In the optical thin film 1 of Comparative Example 6, the first surface accuracy change criterion is met very well, but R p Width ratio and GDD rp The width ratio does not meet the standard, R p and GDD rp Each wavelength range is narrow.

[0083] In contrast to the above, the optical thin films 1 in Examples 1-6, 9, 12, and 14 are alternating films of three materials: TiO2 film, H4 film, and SiO2 film. In the optical thin film 1 of Example 1, the first surface accuracy change criterion is sufficiently met, and the surface accuracy is maintained at a level comparable to a polished surface. Furthermore, in the optical thin film 1 of Example 1, R p Width ratio and GDD rp All width ratios fully meet the standards, R p and GDD rp Each wavelength range is sufficiently wide. In the optical thin film 1 of Example 2, the first surface accuracy change criterion is sufficiently satisfied. Also, in the optical thin film 1 of Example 2, R p Width ratio and GDD rp The width ratios all fully meet the standards. In the optical thin film 1 of Example 3, the first surface accuracy change criterion is sufficiently satisfied. Also, in the optical thin film 1 of Example 3, R p Width ratio and GDD rpThe width ratios all fully meet the standards. In the optical thin film 1 of Example 4, the first surface accuracy change criterion is met. Also, in the optical thin film 1 of Example 4, R p Width ratio and GDD rp The width ratios all fully meet the criteria. In optical thin film 1 of Example 4, in particular, R p The width ratio is the largest among Examples 1 to 6. In the optical thin film 1 of Example 5, the first surface accuracy change criterion is sufficiently satisfied. Also, in the optical thin film 1 of Example 5, R p Width ratio and GDD rp The width ratios all fully meet the standards. In the optical thin film 1 of Example 6, the first surface accuracy change criterion is sufficiently satisfied. Also, in the optical thin film 1 of Example 6, R p Width ratio and GDD rp The width ratios all fully meet the criteria. In particular, in optical thin film 1 of Example 6, GDD rp The width ratio is the largest among Examples 1 to 6.

[0084] In the optical thin film 1 of Example 9, the first surface accuracy change criterion is sufficiently satisfied. Also, in the optical thin film 1 of Example 9, R p Width ratio and GDD rp The width ratios all fully meet the criteria. The ratio of the first pair in Example 9 is p. T This is the smallest value among Examples 1-6, 9, 12, and 14, and is 0.09.

[0085] In the optical thin film 1 of Example 12, R p Width ratio and GDD rp The width ratio fully meets the standard. In the optical thin film 1 of Example 12, the first surface accuracy change criterion is slightly not met. In the optical thin film 1 of Example 12, the second surface accuracy change criterion is met. The absolute value of the surface accuracy change in the optical thin film 1 of Example 12 is similar to the surface accuracy change in the optical thin film 1 of Comparative Example 2, while the R in the optical thin film 1 of Example 12 is different. p Width ratio and GDD rp The width ratio is R of optical thin film 1 in comparative example 2. p Width ratio and GDD rp It is larger than the width ratio. In the optical thin film 1 of Example 14, R p Width ratio and GDD rp The width ratio fully meets the standard. In optical thin film 1 of Example 14, the first surface accuracy change criterion is slightly not met. In optical thin film 1 of Example 14, the second surface accuracy change criterion is met. The absolute value of the surface accuracy change in optical thin film 1 of Example 14 is similar to the surface accuracy change in optical thin film 1 of Comparative Example 2, while the R in optical thin film 1 of Example 14 is different. p Width ratio and GDD rp The width ratio is R of optical thin film 1 in comparative example 2. p Width ratio and GDD rp Larger than the width ratio. The ratio of the first pair in Example 14, p. T It is 0.64.

[0086] In each of the optical thin films 1 in Examples 1-6, 9, 12, and 14, the first pair ratio p T As the value increases, the absolute value of the change in surface accuracy tends to increase. The proportion of the first pair, p T From the viewpoint of suppressing changes in surface accuracy, it is preferable that the value is 0.55 or less, with the value of 0.55 in Example 4 being used as the threshold. This preferred ratio of the first pair p T The range includes optical thin films 1 from Examples 1-6 and 9, but does not include optical thin films 1 from Examples 12 and 14. On the other hand, the proportion of the first pair p T If the first pair ratio p is too small, it approaches Comparative Example 1 where the H4 film does not fit, resulting in a large change in surface accuracy, and it becomes difficult to obtain the performance improvement effect of the high-density H4 film. T The value is preferably 0.09 or greater, with 0.09 being the threshold value in Example 9.

[0087] Also, surface accuracy changes and R p Width ratio and GDD rp In the optical thin films 1 of Examples 2 to 6, which show an even better balance with the width ratio, the physical film thickness ratio t:h:c falls within the range of t:h:c = 0.12~0.19:0.17~0.28:0.63~0.64. Therefore, in the optical thin film 1, it is more preferable that the physical film thickness ratio t:h:c falls within the range of t:h:c = 0.12~0.19:0.17~0.28:0.63~0.64.

[0088] The optical thin films 1 in Examples 7, 8, and 13 are alternating layers of three materials: Ta2O5 film, H4 film, and SiO2 film. In the optical thin films 1 of Examples 7, 8, and 13, a Ta2O5 film can be used. In the optical thin film 1 of Example 7, the first surface accuracy change criterion is sufficiently met, and the surface accuracy is maintained at a level comparable to a polished surface. Furthermore, in the optical thin film 1 of Example 7, R p Width ratio and GDD rp All width ratios meet the criteria, R p and GDD rp Each wavelength range is wide. The second pair ratio p in the optical thin film 1 of Example 7 A It is 0.18. In the optical thin film 1 of Example 8, the first surface accuracy change criterion is sufficiently satisfied. Also, in the optical thin film 1 of Example 8, R p Width ratio and GDD rp The width ratios all meet the criteria. The ratio of the second pair in optical thin film 1 of Example 8 is p. A It is 0.06. In the optical thin film 1 of Example 13, the first surface accuracy change criterion is slightly not met. In the optical thin film 1 of Example 13, the second surface accuracy change criterion is met. On the other hand, in the optical thin film 1 of Example 13, R p Width ratio and GDD rp The width ratios all meet the criteria. The ratio of the second pair in optical thin film 1 of Example 13 is p. A It is 0.35. In the optical thin film 1 of Example 13, the surface accuracy change, R p Width ratio and GDD rp In terms of width ratio, it is similar to Comparative Example 2, but in Example 13, unlike Comparative Example 2, Ta2O5 can be used.

[0089] In each of the optical thin films 1 in Examples 7, 8, and 13, the second pair ratio p A As the value increases, the absolute value of the change in surface accuracy tends to increase. The proportion of the second pair, pA From the perspective of suppressing the change in surface accuracy, it is preferable that the value obtained by adding 0.02 to 0.18, which is the value in Example 7, is used as the threshold value, and it is 0.20 or less. In this preferable second pair number ratio p A range, each optical thin film 1 of Examples 7 and 8 is included, and the optical thin film 1 of Example 13 is not included. On the other hand, if the second pair number ratio p A is too small, the change in surface accuracy becomes large, and it becomes difficult to obtain the performance improvement effect by the high-density H4 film. Therefore, for the second pair number ratio p A it is preferable that the value obtained by subtracting 0.01 from 0.06, which is the value in Example 8, is used as the threshold value, and it is 0.05 or more. In addition, the adjustment from the values of the examples at the above-mentioned respective threshold values is based on the upward trend of the change in surface accuracy corresponding to the increase in the second pair number ratio p A and the trend of performance change corresponding to the decrease in the second pair number ratio p A and is carried out in consideration of these.

[0090] Each optical thin film 1 of Examples 10, 11, and 15 is an alternating film of three materials, namely, a Nb2O5 film, a H4 film, and a SiO2 film. In the optical thin film 1 of Example 10,11,15 a Nb2O5 film can be used. In the optical thin film 1 of Example 10, the first surface accuracy change criterion is sufficiently satisfied, and the surface accuracy is maintained at about the polished surface level. Also, in the optical thin film 1 of Example 10, R p width ratio and GDD rp width ratio both satisfy the criteria, and the R p and GDD rp each wavelength range is wide. The third pair number ratio p B in the optical thin film 1 of Example 10 is 0.18. In the optical thin film 1 of Example 11, the first surface accuracy change criterion is sufficiently satisfied. Also, in the optical thin film 1 of Example 11, R p width ratio and GDD rp width ratio both satisfy the criteria. The third pair number ratio p B in the optical thin film 1 of Example 11 is 0.06. In the optical thin film 1 of Example 15, the first surface accuracy change criterion is slightly not satisfied. In the optical thin film 1 of Example 15, the second surface accuracy change criterion is satisfied. On the other hand, in the optical thin film 1 of Example 15, R p width ratio and GDD rp both width ratios satisfy the criteria. The third pair number ratio p B in the optical thin film 1 of Example 15 is 0.35. In the optical thin film 1 of Example 15, surface accuracy change, R p width ratio and GDD rp width ratio are similar to those of Comparative Example 2. However, in Example 15, different from Comparative Example 2, Nb2O5 can be used.

[0091] In each of the optical thin films 1 of Examples 10, 1, and 15, as the third pair number ratio p B increases, the absolute value of the surface accuracy change tends to increase. The third pair number ratio p B is preferably 0.20 or less, with a value obtained by adding 0.02 to 0.18, which is the value in Example 11, as the threshold from the viewpoint of suppressing surface accuracy change. The optical thin films of Examples 10 and 11 are within this preferred range of the third pair number ratio p B while the optical thin film 1 of Example 15 is not. On the other hand, if the third pair number ratio p B is too small, the surface accuracy change becomes large and it becomes difficult to obtain the performance improvement effect by the high-density H4 film. Therefore, the third pair number ratio p B is preferably 0.05 or more, with a value obtained by subtracting 0.01 from 0.06, which is the value in Example 11, as the threshold. In addition, the adjustment from the values of the examples at the above thresholds is made in consideration of the upward trend of the surface accuracy change according to the increase in the third pair number ratio p B and the performance change trend according to the decrease in the third pair number ratio p B .

[0092] Furthermore, in the optical thin films 1 of Examples 1-4 and 6-15, a film with a higher refractive index than the H4 film, such as a TiO2 film, a Ta2O5 film, or a Nb2O5 film, is positioned outside the outermost H4 film. Therefore, in the optical thin films 1 of Examples 1-4 and 6-15, incident light can be received by a film with a higher refractive index than the H4 film before it reaches the H4 film, improving the performance of the optical product P, such as its reflective performance. [Explanation of symbols]

[0093] 1. Optical thin film, 2. Substrate, P. Optical product, U. Surface to be coated.

Claims

1. One or more first films having a first material, One or more second films having a second material different from the first material, One or more third films having a third material, It is equipped with, The first material is an oxide compound containing Ti and La, The first film has tensile stress, The refractive index of the first film and the refractive index of the second film are higher than the refractive index of the third film. The third film has compressive stress. An optical thin film characterized by the following features.

2. Formed on the substrate, The coefficient of linear expansion of the substrate is 2 × 10 －６ / ℃ is less than The optical thin film according to feature 1.

3. When formed on one side of a synthetic quartz glass substrate with a diameter of 30 mm and a thickness of 3 mm, the change in surface accuracy of that one side is 0.2λ or less, with λ = 632.8 nm. The optical thin film according to feature 1.

4. The second material is an oxide of Ti, The third material is an oxide of Si. The optical thin film according to feature 1.

5. The first film or the second film and the third film are arranged alternately. If the number of pairs of the second and third films is defined as the first pair number, the number of pairs of the first and third films is defined as the second pair number, and the ratio of the first pair number to the sum of the first and second pair numbers is defined as the first pair number ratio, The ratio of the first pair is 0.09 or more and 0.55 or less. The optical thin film according to feature 4.

6. The physical film thickness ratio t:h:c, which is the ratio of the first subtotal physical film thickness h (the sum of the physical film thicknesses of the first film), the second subtotal physical film thickness t (the sum of the physical film thicknesses of the second film), and the third subtotal physical film thickness c (the sum of the physical film thicknesses of the third film), is t:h:c = 0.12 to 0.19:0.17 to 0.28:0.63 to 0.

64. The optical thin film according to feature 4.

7. Formed on the substrate, The coefficient of linear expansion of the substrate is 2 × 10 －６ Less than / ℃, The second material is an oxide of Ti, The third material is an oxide of Si, The first film or the second film and the third film are arranged alternately. If the number of pairs of the second and third films is defined as the first pair number, the number of pairs of the first and third films is defined as the second pair number, and the ratio of the first pair number to the sum of the first and second pair numbers is defined as the first pair number ratio, The ratio of the first pair is 0.09 or more and 0.55 or less. The optical thin film according to feature 1.

8. The second material is an oxide of Ta, The third material is an oxide of Si. The optical thin film according to feature 1.

9. The first film or the second film and the third film are arranged alternately. If the number of pairs of the second and third films is defined as the third pair number, the number of pairs of the first and third films is defined as the second pair number, and the ratio of the third pair number to the sum of the third and second pair numbers is defined as the second pair number ratio, The ratio of the second pair is 0.05 or more and 0.20 or less. The optical thin film according to feature 8.

10. The second material is an oxide of Nb, The third material is an oxide of Si. The optical thin film according to feature 1.

11. The first film or the second film and the third film are arranged alternately. If the number of pairs of the second and third films is defined as the fourth pair number, the number of pairs of the first and third films is defined as the second pair number, and the ratio of the fourth pair number to the sum of the fourth and second pair numbers is defined as the third pair number ratio, The ratio of the third pair is 0.05 or more and 0.20 or less. The optical thin film according to feature 10.

12. Formed on the substrate, The second film is positioned further outward than the first film, which is positioned closest to the substrate. The optical thin film according to feature 1.

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