JP2015206908A - Antireflection film and optical component having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antireflection film of an eleven layer structure with low reflectance ratio.SOLUTION: An antireflection film is obtained by alternatively laminating, by ten layers, a high refractive index film and a low refractive index film having a refractive index lower than that of the high refractive index film, and further laminating an ultra-low refractive index film having a refractive index further lower than that of the low refractive index film on the laminated ten layers.

Description

  The present invention relates to an antireflection film for light in the visible range used for a television camera, a video camera, a digital camera, an in-vehicle camera, a microscope, a telescope, and the like, and an optical component having the antireflection film.

  A high-performance zoom lens widely used for a photographic camera, a broadcast camera, and the like has a configuration of a mirror of a lens group composed of multiple layers. In general, such a zoom lens is composed of about 10 to 40 lenses. On the surface of these optical components such as lenses, a dielectric film having a refractive index different from the refractive index of the substrate is combined, and the thickness of each dielectric film is 1 / 2λ or 1 with respect to the center wavelength λ. Antireflection treatment by a multilayer film using an interference effect such as / 4λ is performed.

  In recent years, there has been a great demand for reducing the reflectance of such an antireflection film, and an antireflection film in which the reflectance in the visible region of 400 to 700 nm is reduced to 0.02 to 0.05% is already known.

  For example, JP 2007-94150 (Patent Document 1) discloses a high refractive index film having a refractive index of 1.85 to 2.45 and a low refractive index having a refractive index of 1.30 to 1.65 for the purpose of enhancing the antireflection effect in the visible range of 400 to 700 nm. An antireflection film having a five-layer or six-layer structure in which four or five films are formed on a substrate and an ultra-low refractive index film having a refractive index of 1.05 to 1.30 is formed on the outermost surface is disclosed. Patent Document 1 exemplifies a six-layer antireflection film having a reflectance of about 0.02% at a wavelength of 400 to 700 nm with respect to a substrate having a refractive index of 1.95.

JP-A-2009-8901 (Patent Document 2) discloses a high refractive index film having a refractive index N _H ≧ 2 and a low refractive index having a refractive index N _M ≦ 1.70 for the purpose of enhancing the antireflection effect in the visible region of 430 to 670 nm. An antireflection film of 8 to 10 layers is disclosed in which 7 to 9 layers are formed and an ultra-low refractive index film having a refractive index N _L ≦ 1.30 is formed on the outermost surface. Patent Document 2 exemplifies an antireflection film having a 10-layer structure in which a reflectance at a wavelength of 400 to 700 nm is about 0.03% with respect to a substrate having a refractive index of 1.519.

  JP-A-2013-250295 (Patent Document 3) is designed to reduce the high refractive index film to 1, 3, 5, 7, 9, 11 layers for the purpose of enhancing the antireflection effect in the visible to infrared range of 400 to 1600 nm. An antireflection film having a 12-layer structure in which a refractive index film is formed in 2, 4, 6, 8, and 10 layers and an ultra-low refractive index film having a refractive index of 1.2 to 1.29 is formed on the outermost surface is disclosed. Patent Document 3 exemplifies a 12-layer antireflection film having a reflectance of about 1.0% at a wavelength of 400 to 1600 nm with respect to substrates having a refractive index of 1.70 and 1.81, and this antireflection film has a visible region. A reflectance of about 1.0% is exhibited at 400 to 700 nm.

  However, the antireflection films described in Patent Document 1, Patent Document 2 and Patent Document 3 maintain good optical performance unless a strong light source enters the photographing screen, but a strong light source exists in the photographing screen. When entering, there is a problem that flare and ghost in the visible range occur and the contrast is lowered, and further improvement is desired.

Japanese Unexamined Patent Publication No. 2007-94150 JP 2009-8901 JP 2013-250295 A

  Accordingly, an object of the present invention is to provide an antireflection film having 11 layers and a low reflectance.

  As a result of diligent research in view of the above object, the present inventor alternately laminated 10 layers of a high refractive index film and a low refractive index film having a refractive index lower than that of the high refractive index film. It was found that an antireflection film formed by laminating an ultra-low refractive index film having a refractive index lower than that of a low refractive index film has an antireflection performance with a reflectance in the visible range of 400 to 700 nm of 0.01% or less. I came up with the invention.

That is, the antireflection film of the present invention is an antireflection film for visible wavelengths of 400 to 700 nm obtained by sequentially laminating a first layer to an eleventh layer on a substrate,
The first to tenth layers are formed by alternately laminating a high refractive index film and a low refractive index film having a lower refractive index than the high refractive index film, and the eleventh layer is formed from the low refractive index film. Further, it is characterized in that an ultra-low refractive index film having a lower refractive index is laminated.

  The first layer is preferably composed of a low refractive index film.

  Preferably, the refractive index of the substrate is 1.43 to 2.01, the refractive index of the low refractive index film is 1.37 to 1.51, and the refractive index of the high refractive index film is 1.9 to 2.5.

The refractive index of the first layer is 1.37 to 1.51 and the optical film thickness is 4 to 90 nm,
The refractive index of the second layer is 1.9 to 2.5 and the optical film thickness is 4 to 130 nm,
The third layer has a refractive index of 1.37 to 1.51 and an optical film thickness of 20 to 120 nm,
The refractive index of the fourth layer is 1.9 to 2.5 and the optical film thickness is 30 to 100 nm,
The refractive index of the fifth layer is 1.37 to 1.51 and the optical film thickness is 20 to 70 nm,
The refractive index of the sixth layer is 1.9 to 2.5 and the optical film thickness is 80 to 160 nm,
The refractive index of the seventh layer is 1.37 to 1.51 and the optical film thickness is 4 to 40 nm,
The refractive index of the eighth layer is 1.9 to 2.5 and the optical film thickness is 50 to 190 nm,
The refractive index of the ninth layer is 1.37 to 1.51 and the optical film thickness is 40 to 140 nm,
The refractive index of the tenth layer is 1.9 to 2.5 and the optical film thickness is 4 to 50 nm,
The eleventh layer preferably has a refractive index of 1.05 to 1.3 and an optical film thickness of 130 to 150 nm.

The low refractive index film is a film made of a material selected from the group consisting of MgF ₂ , SiO ₂ , a mixture of SiO ₂ and Al ₂ O ₃ , a fluororesin,
The high refractive index film is a mixture of _{TiO 2, Nb 2 O 5,} TiO 2 and _{Nb 2 O 5, Ta 2 O} 5, ZrO 2, HfO 2, CeO 2, La 2 O 3, ZnO, SnO 2, In 2 A material selected from the group consisting of O ₃ , ZnS, a mixture of In ₂ O ₃ and SnO _2, a mixture of ZnO and Al ₂ O _3, a mixture of ZnO and Ga ₂ O _{3, and} a mixture of TiO ₂ and La ₂ O ₃ A membrane consisting of
The ultra-low refractive index film is preferably a nanoporous film or a nanoparticle film made of a material selected from the group consisting of MgF ₂ , SiO ₂ , Al ₂ O ₃ and a fluororesin.

  The refractive index of the first layer is preferably lower than the refractive index of the substrate.

  The optical component of the present invention has the antireflection film.

  Since the antireflection film of the present invention exhibits low reflectance with 11 layers, even when a strong light source enters the photographing screen, visible light flare and ghost do not occur, and high optical performance with high contrast can be achieved. .

It is sectional drawing which shows typically an example of the antireflection film of this invention formed on the board | substrate. 4 is a graph showing 5 ° incident spectral reflectance of the antireflection film of Example 1. 6 is a graph showing 5 ° incident spectral reflectance of an antireflection film of Example 2. 6 is a graph showing 5 ° incident spectral reflectance of an antireflection film of Example 3. 6 is a graph showing 5 ° incident spectral reflectance of an antireflection film of Example 4. 10 is a graph showing 5 ° incident spectral reflectance of an antireflection film of Example 5. 10 is a graph showing 5 ° incident spectral reflectance of an antireflection film of Example 6. 10 is a graph showing 5 ° incident spectral reflectance of an antireflection film of Example 7. 10 is a graph showing 5 ° incident spectral reflectance of an antireflection film of Example 8. 10 is a graph showing 5 ° incident spectral reflectance of an antireflection film of Example 9. 10 is a graph showing 5 ° incident spectral reflectance of the antireflection film of Example 10. 14 is a graph showing 5 ° incident spectral reflectance of the antireflection film of Example 11. 14 is a graph showing 5 ° incident spectral reflectance of the antireflection film of Example 12. 5 is a graph showing 5 ° incident spectral reflectance of an antireflection film of Comparative Example 1. 6 is a graph showing 5 ° incident spectral reflectance of an antireflection film of Comparative Example 2. It is a graph which shows the refractive index dispersion | distribution of wavelength 350-750 nm of the film | membrane material used by the Example and the comparative example. 5 is a graph showing 5 ° incident spectral reflectances of antireflection films 1 and 2 of Comparative Example 3. 10 is a graph showing 5 ° incident spectral reflectance of an antireflection film 2 of Comparative Example 3.

[1] Antireflection film
(1) Configuration As shown in FIG. 1, the antireflection film of the present invention has a predetermined refractive index and optical film thickness [refractive index (n) × physical film thickness (d)] from the first layer 101 to the eleventh layer. A thin film up to the layer 111 is laminated on the surface of the substrate 3. The first to tenth layers are alternately laminated with a high refractive index film and a low refractive index film having a lower refractive index than the high refractive index film, and the eleventh layer is lower than the low refractive index film. It is an ultra-low refractive index film having a refractive index. In the first to tenth layers, it is preferable that the first layer is composed of a low refractive index film, that is, the radix layer is composed of a low refractive index film, and the even layer is composed of a high refractive index film. Furthermore, the refractive index of the first layer is preferably lower than the refractive index of the substrate.

  By configuring the refractive index of the first layer with a low refractive index film and setting it lower than the refractive index of the substrate, the reflectance (incident angle of 0 to 10 °) in the visible wavelength range of 400 to 700 nm is greatly reduced. Can be made. In particular, the effect of reducing the reflectance of a substrate having a high refractive index is great. In the case of a substrate having a high refractive index, since the reflectance of the substrate itself (uncoated) is high, it is more difficult to lower the reflectance than a substrate having a low refractive index. For example, when a substrate having a high refractive index of about 2.00 is used, even if a high refractive index film having a refractive index of 1.9 to 2.5 is provided as the first layer, a large interference effect is not obtained, and a high antireflection effect is obtained. I can't. Therefore, in the case of a substrate having a high refractive index, it is advantageous to form the first layer with a low refractive index film because a high antireflection effect is obtained.

The antireflection film of the present invention is more preferably an arbitrary wavelength between 400 to 700 nm on a substrate having a refractive index of 1.43 to 2.1 in order from the substrate surface.
A first layer 101 having a refractive index of 1.37 to 1.51 and an optical film thickness of 4 to 90 nm;
A second layer 102 having a refractive index of 1.9 to 2.5 and an optical film thickness of 4 to 130 nm,
A third layer 103 having a refractive index of 1.37 to 1.51 and an optical film thickness of 20 to 120 nm,
A fourth layer 104 having a refractive index of 1.9 to 2.5 and an optical film thickness of 30 to 100 nm,
A fifth layer 105 having a refractive index of 1.37 to 1.51 and an optical film thickness of 20 to 70 nm,
A sixth layer 106 having a refractive index of 1.9 to 2.5 and an optical thickness of 80 to 160 nm,
A seventh layer 107 having a refractive index of 1.37 to 1.51 and an optical thickness of 4 to 40 nm;
An eighth layer 108 having a refractive index of 1.9 to 2.5 and an optical thickness of 50 to 190 nm;
A ninth layer 109 having a refractive index of 1.37 to 1.51 and an optical thickness of 40 to 140 nm,
A tenth layer 110 having a refractive index of 1.9 to 2.5 and an optical film thickness of 4 to 50 nm and an eleventh layer 111 having a refractive index of 1.05 to 1.3 and an optical film thickness of 130 to 150 nm are laminated. Become.

Furthermore, in order to obtain a good antireflection effect at a wavelength of 400 to 700 nm, at a wavelength of 587.56 nm,
The refractive index of the first layer is preferably 1.38 to 1.50, the optical film thickness is preferably 5 to 89 nm,
The refractive index of the second layer is preferably 1.91 to 2.49, the optical film thickness is preferably 5 to 129 nm,
The refractive index of the third layer is preferably 1.38 to 1.50, the optical film thickness is preferably 21 to 119 nm,
The refractive index of the fourth layer is preferably 1.91 to 2.49, the optical film thickness is preferably 31 to 99 nm,
The refractive index of the fifth layer is preferably 1.38 to 1.50, the optical film thickness is preferably 21 to 69 nm,
The refractive index of the sixth layer is preferably 1.91 to 2.49, the optical film thickness is preferably 81 to 159 nm,
The refractive index of the seventh layer is preferably 1.38 to 1.50, the optical film thickness is preferably 5 to 39 nm,
The refractive index of the eighth layer is preferably 1.91 to 2.49, the optical film thickness is preferably 51 to 189 nm,
The refractive index of the ninth layer is preferably 1.38 to 1.50, the optical film thickness is preferably 41 to 139 nm,
The refractive index of the tenth layer is preferably 1.91 to 2.49, the optical film thickness is preferably 5 to 49 nm,
The refractive index of the eleventh layer is preferably 1.06 to 1.29, and the optical film thickness is preferably 131 to 149 nm.

(2) Material The low refractive index film constituting the layer having a refractive index of 1.37 to 1.51 is a film made of a material selected from the group consisting of MgF ₂ , SiO ₂ , a mixture of SiO ₂ and Al ₂ O ₃ , and a fluororesin. It is. Fluororesin includes tetrafluoroethylene resin (PTFE), trifluorinated methylene chloride resin (PCTFE), vinyl fluoride resin (PVF), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), fluoride Vinylidene resin can be used.

High refractive index film constituting the layer of the refractive index 1.9 to 2.5 _{is, TiO 2, Nb 2 O 5} , a mixture of TiO ₂ and _{Nb 2 O 5, Ta 2 O} 5, ZrO 2, HfO 2, CeO 2, La ₂ O ₃ , ZnO, SnO ₂ , In ₂ O ₃ , ZnS, a mixture of In ₂ O ₃ and SnO _2, a mixture of ZnO and Al ₂ O _3, a mixture of ZnO and Ga ₂ O ₃ , TiO ₂ and La ₂ O _{3 is} a film made of a material selected from the group consisting of ₃ mixtures.

The ultra-low refractive index film constituting the layer having a refractive index of 1.05 to 1.3 is a nanoporous film or a nanoparticle film made of a material selected from the group consisting of MgF ₂ , SiO ₂ , Al ₂ O ₃ and fluororesin. is there. As the nanoporous film or nanoparticle film, a porous film obtained by using a sol solution containing fine particles such as magnesium fluoride described in International Publication No. 2002/018982, described in International Publication No. 2006/030848 and MgF ₂ particles MgF ₂ porous optical thin film and an amorphous silicon oxide-based binder present between MgF ₂ particles JP 2006-3562, JP 2006-215542, JP 2007-94150 ( Patent Document 1), silica airgel film described in JP2008-225210A and JP2008-233403, "Journal of Sol-Gel Science and Technology", 2000 Year, Vol. 18, pp. 219-224, and the like.

  The eighth layer is preferably a nanoporous film mainly composed of silica, and is particularly preferably composed of the silica airgel film or the nanoporous silica film. Since a layer made of a silica airgel film or a nanoporous silica film has a low refractive index, an excellent antireflection function can be exhibited by providing this layer at a position farthest from the substrate. The pore diameter of the porous layer is preferably 0.005 to 0.2 μm, and the porosity is preferably 20 to 60%.

(3) Substrate The substrate 3 has a refractive index of 1.43 to 2.1, preferably 1.435 to 2.005, at a wavelength of 400 to 700 nm. By forming the antireflection film using the substrate 3 having such a refractive index, the optical performance can be satisfactorily improved in the wavelength region.

  Examples of the material of the substrate 3 include optical glass such as BaSF2, SF5, LaF2, LaSF09, LaSF01, LaSF016, LAK7, and LAK14, and ceramics such as Lumicera (registered trademark).

[2] Manufacturing method
(1) Formation method of the first layer to the tenth layer The first layer to the tenth layer of the antireflection film are preferably formed by a physical film formation method. Examples of the physical film forming method include a vacuum vapor deposition method, an ion assist vapor deposition method, an ion plating method, and a sputtering method. Among these, the sputtering method is particularly preferable in terms of manufacturing cost and processing accuracy.

(2) Formation method of the eleventh layer The nanoporous film or nanoparticle film of the eleventh layer is WO 2002/018982, WO 2006/030848, JP 2006-3562, JP 2006- 215542, JP 2007-94150 (Patent Document 1), JP 2008-225210, JP 2008-233403, “Journal of Sol-Gel Science and Technology” ”, 2000, Vol. 18, pp. 219-224, etc. The porous layer containing silica as a main component is preferably formed by a wet method, and particularly preferably a sol-gel method. That is, a wet gel composed of a silica skeleton-forming compound such as alkoxysilane is organically modified as necessary, an ultraviolet curable resin is mixed as a binder, and the obtained coating liquid is applied, dried and baked. Form. The following is a two-step reaction using an alkali and an acid described in “Journal of Sol-Gel Science and Technology”, 2000, Vol. 18, pp. 219-224. The method for forming a nanoporous silica film according to the present invention will be described in detail, but the present invention is not limited thereto.

  The nanoporous silica film is formed by a two-step reaction. (I) A step of adding an acidic catalyst to an alkaline sol prepared by hydrolysis and polycondensation of alkoxysilane under a basic catalyst to obtain a first sol; (ii) adding a mixture of alkoxysilane and water to the first sol and further proceeding hydrolysis and condensation polymerization to prepare a second sol; (iii) applying the obtained second sol on the substrate And a drying (heat treatment) step, (iv) an alkali treatment step, and (vi) a washing step.

(i) Step of preparing the first sol
(a) Alkoxysilane The alkoxysilane for producing the first sol is preferably a tetraalkoxysilane monomer or oligomer (condensation product). When a tetrafunctional alkoxysilane is used, a sol of colloidal silica particles having a relatively large particle size can be obtained. Tetraalkoxysilane is represented by Si (OR) ₄ [R is an alkyl group having 1 to 5 carbon atoms (methyl, ethyl, propyl, butyl, etc.) or an acyl group having 1 to 4 carbon atoms (acetyl etc.)]. Those are preferred. Specific examples of tetraalkoxysilane include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, diethoxydimethoxysilane and the like. Of these, tetramethoxysilane and tetraethoxysilane are preferred. A small amount of trifunctional or lower functional alkoxysilane may be added to the tetraalkoxysilane as long as the effects of the present invention are not impaired.

(b) Hydrolysis and polycondensation in the presence of a basic catalyst Hydrolysis and polycondensation proceed by adding an organic solvent, a basic catalyst and water to the alkoxysilane. As the organic solvent, alcohols such as methanol, ethanol, n-propanol, i-propanol, and butanol are preferable, and methanol or ethanol is more preferable. As the basic catalyst, ammonia, amine, NaOH or KOH is preferable. Preferred amines are alcohol amines or alkyl amines (methylamine, dimethylamine, trimethylamine, n-butylamine, n-propylamine, etc.).

The amount ratio between the organic solvent and the alkoxysilane is preferably set so that the concentration of the alkoxysilane is 0.1 to 10% by mass (silica concentration) in terms of SiO ₂ . When the silica concentration is more than 10% by mass, the particle size of the silica particles in the obtained sol becomes too large. On the other hand, when the silica concentration is less than 0.1, the particle size of the silica particles in the obtained sol becomes too small. The molar ratio of organic solvent / alkoxysilane is preferably in the range of 5 × 10 ^{2 to} 5 × 10 ⁴ .

The basic catalyst / alkoxysilane molar ratio is preferably 1 × 10 ⁻⁴ to 1, more preferably 1 × 10 ^{−4 to} 0.8, and particularly preferably 3 × 10 ^{−4 to} 0.5. . If the molar ratio of basic catalyst / alkoxysilane is less than 1 × 10 ⁻⁴ , hydrolysis reaction of alkoxysilane does not occur sufficiently. On the other hand, even if the molar ratio exceeds 1 and the base is added, the catalytic effect is saturated.

  The water / alkoxysilane molar ratio is preferably 1-40. If the water / alkoxysilane molar ratio is more than 40, the hydrolysis reaction proceeds too quickly, making it difficult to control the reaction, making it difficult to obtain a uniform silica airgel film. On the other hand, when it is less than 1, hydrolysis of alkoxysilane does not occur sufficiently.

  The alkoxysilane solution containing the basic catalyst and water is preferably aged by standing at 15 to 25 ° C. for about 30 minutes to 10 hours or by slowly stirring. By aging, hydrolysis and condensation polymerization proceed, and an alkaline sol is generated. The alkaline sol includes, in addition to a dispersion of colloidal silica particles, a dispersion in which colloidal silica particles are aggregated in a cluster.

(c) Hydrolysis and polycondensation in the presence of an acidic catalyst Add an acidic catalyst and water and an organic solvent as necessary to the obtained alkaline sol, lower the pH to about 1, and perform hydrolysis and condensation in an acidic state. The condensation polymerization is further advanced. Examples of the acidic catalyst include hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, acetic acid and the like. The same organic solvent as above can be used. The organic solvent / alkoxysilane molar ratio and the water / alkoxysilane molar ratio may be the same as described above. The sol containing the acidic catalyst is preferably aged by standing at 10 to 90 ° C. for about 15 minutes to 24 hours or slowly stirring. By aging, hydrolysis and condensation polymerization proceed to produce a first sol.

  The median diameter of the silica particles in the first sol is 100 nm or less, preferably 10 to 50 nm. The median diameter is measured by a dynamic light scattering method.

(ii) Step of preparing the second sol
(a) Alkoxysilane A mixture of alkoxysilane and water is added to the first sol, and hydrolysis and condensation polymerization are further advanced to prepare a second sol. As the alkoxysilane, Si (OR ¹ ) _x (R ² ) _4-x [x is an integer of 2 to 4. It is preferable to use a bifunctional to tetrafunctional compound represented by R ¹ is preferably an alkyl group having 1 to 5 carbon atoms (methyl, ethyl, propyl, butyl or the like) or an acyl group having 1 to 4 carbon atoms (acetyl or the like). R ² is preferably an organic group having 1 to 10 carbon atoms, for example, a hydrocarbon group such as methyl, ethyl, propyl, butyl, hexyl, cyclohexyl, octyl, decyl, phenyl, vinyl, allyl, and γ-chloropropyl, CF ₃ CH _2- , CF ₃ CH ₂ CH _2- , C ₂ F ₅ CH ₂ CH _2- , C ₃ F ₇ CH ₂ CH ₂ CH _2- , CF ₃ OCH ₂ CH ₂ CH _2- , C ₂ F ₅ OCH ₂ CH ₂ CH _2- , C ₃ F ₇ OCH ₂ CH ₂ CH _2- , (CF ₃ ) ₂ CHOCH ₂ CH ₂ CH _2- , C ₄ F ₉ CH ₂ OCH ₂ CH ₂ CH _2- , 3- (perfluoro (Cyclohexyloxy) propyl, H (CF ₂ ) ₄ CH ₂ OCH ₂ CH ₂ CH _2- , H (CF ₂ ) ₄ CH ₂ CH ₂ CH _2- , γ-glycidoxypropyl, γ-mercaptopropyl, 3,4 -Substituted hydrocarbon groups such as epoxycyclohexylethyl and γ-methacryloyloxypropyl.

  Specific examples of the bifunctional alkoxysilane include dimethyldialkoxysilane such as dimethyldimethoxysilane and dimethyldiethoxysilane. Specific examples of the trifunctional alkoxysilane include methyltrialkoxysilane such as methyltrimethoxysilane and methyltriethoxysilane, and phenyltrialkoxysilane such as phenyltriethoxysilane. Examples of the tetrafunctional alkoxysilane include tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetrabutoxysilane, and diethoxydimethoxysilane. The alkoxysilane is preferably trifunctional or more, more preferably methyltrialkoxysilane and tetraalkoxysilane.

  The water / alkoxysilane molar ratio is preferably 1-5. After the mixture of alkoxysilane and water is added to the first sol, it is aged by standing at 15-25 ° C. for about 1-20 days or stirring slowly. By aging, hydrolysis and polycondensation further proceed to produce a second sol. When the aging time exceeds 20 days, the median diameter of the silica particles in the sol becomes too large.

  The median diameter of the colloidal silica particles in the second sol is 1 to 100 nm, preferably 10 to 50 nm.

(iii) Application and drying process
(a) Application Examples of methods for applying the second sol to the surface of the substrate include dip coating, spray coating, spin coating, and printing. When applying to a three-dimensional structure such as a lens, a dipping method is preferred. The pulling speed in the dipping method is preferably about 0.1 to 3 mm / second.

  The organic solvent may be added as a dispersion medium in order to adjust the concentration and fluidity of the second sol and improve the coating suitability. The concentration of silica in the second sol at the time of application is preferably 0.1 to 20% by mass. If necessary, the second sol may be sonicated. Aggregation of colloidal particles can be prevented by ultrasonic treatment. The ultrasonic frequency is preferably 10 to 30 kHz, the output is preferably 300 to 900 W, and the treatment time is preferably 5 to 120 minutes.

(b) Drying (heat treatment)
The drying conditions for the coating film are appropriately selected according to the heat resistance of the substrate. In order to promote the polycondensation reaction, heat treatment may be performed at a temperature below the boiling point of water for 15 minutes to 24 hours, and then at a temperature of 100 to 200 ° C. for 15 minutes to 24 hours. By performing the heat treatment, the nanoporous silica film exhibits high scratch resistance.

(iv) Alkali treatment step The scratch resistance is further improved by treating the nanoporous silica membrane with an alkali. The alkali treatment is preferably performed by applying an alkali solution or leaving it in an ammonia atmosphere. The solvent of the alkaline solution can be appropriately selected according to the alkali, and water, alcohol and the like are preferable. The concentration of the alkaline solution is preferably 1 × 10 ^{−4 to} 20 N, and more preferably 1 × 10 ⁻³ to 15 N.

  Examples of the alkali include inorganic alkalis such as sodium hydroxide, potassium hydroxide, and ammonia; inorganic alkali salts such as sodium carbonate, sodium bicarbonate, ammonium carbonate, and ammonium bicarbonate; monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, Triethylamine, n-propylamine, di-n-propylamine, n-butylamine, di-n-butylamine, n-amylamine, n-hexylamine, laurylamine, ethylenediamine, hexamethylenediamine, aniline, methylaniline, ethylaniline, Cyclohexylamine, dicyclohexylamine, pyrrolidine, pyridine, imidazole, guanidine, tetramethylammonium hydroxide, tetraethylammonium hydroxide, Organic alkalis such as trabutylammonium hydroxide, monoethanolamine, diethanolamine, triethanolamine, choline; organic acid alkali salts such as ammonium formate, ammonium acetate, monomethylamine formate, dimethylamine acetate, aniline acetate, pyridine lactate, guanidinoacetic acid Etc. can be used.

When alkali treatment is performed by application of an alkaline solution, it is preferable to apply 10 to 200 mL per 1 cm ^{2 of} the nanoporous silica film. The application can be performed by the same method as that for applying the nanoporous silica film, and the spin coating method is preferred. The substrate rotation speed in the spin coating method is preferably about 1,000 to 15,000 rpm. The film after applying the alkaline solution is preferably stored at 1 to 40 ° C, more preferably at 10 to 30 ° C. The storage time is preferably 0.1 to 10 hours, more preferably 0.2 to 1 hour.

When the alkali treatment is performed in an ammonia atmosphere, the treatment is preferably carried out in an ammonia gas partial pressure of 1 × 10 ⁻¹ to 1 × 10 ⁵ Pa. The treatment temperature is preferably 1 to 40 ° C, more preferably 10 to 30 ° C. The treatment time is preferably 1 to 170 hours, more preferably 5 to 80 hours.

  If necessary, the alkali-treated nanoporous silica film is dried. Drying is preferably performed at a temperature of 100 to 200 ° C. for 15 minutes to 24 hours.

(v) Cleaning Step The nanoporous silica film after the alkali treatment may be cleaned as necessary. Washing is preferably performed by a method of immersing in water and / or alcohol, a method of showering, or a combination thereof. You may ultrasonically treat, immersing. The washing temperature is preferably 1 to 40 ° C., and the time is preferably 0.2 to 15 minutes. The nanoporous silica film is preferably washed with 0.01 to 1,000 mL of water and / or alcohol per 1 cm ² . The nanoporous silica film after washing is preferably dried at a temperature of 100 to 200 ° C. for 15 minutes to 24 hours. As alcohol, methanol, ethanol, and isopropyl alcohol are preferable.

[3] Optical component By applying the antireflection film of the present invention to the above-mentioned substrate, an optical component having an antireflection effect having a reflectance of about 0.01% or less in a visible light band of 400 to 700 nm can be obtained. The optical component of the present invention is suitable for a lens, a prism, a diffraction element, and the like mounted on an optical device such as a television camera, a video camera, a digital camera, an in-vehicle camera, a microscope, and a telescope. Particularly suitable for an interchangeable lens of a camera.

  The present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.

Example 1
On the S-FPL53 substrate (manufactured by OHARA, Inc., nd = 1.440), as shown in Table 1, as a first layer to a tenth layer, a SiO ₂ film having a refractive index of 1.481 and a TiO having a refractive index of 2.455 at a wavelength of 587.56 nm. _Two films were alternately formed by a sputtering method, and a silica airgel film having a refractive index of 1.150 at a wavelength of 587.56 nm was formed as an eleventh layer by a sol-gel method to produce an antireflection film. FIG. 2 shows the 5 ° incident spectral reflectance of this antireflection film.

Example 2
On the S-LAL10 substrate (manufactured by OHARA, Inc., nd = 1.720), with the structure shown in Table 2, as the first to tenth layers, a SiO ₂ film having a refractive index of 1.481 and a TiO having a refractive index of 2.455 at a wavelength of 587.56 nm _Two films were alternately formed by a sputtering method, and a silica airgel film having a refractive index of 1.150 at a wavelength of 587.56 nm was formed as an eleventh layer by a sol-gel method to produce an antireflection film. FIG. 3 shows the 5 ° incident spectral reflectance of this antireflection film.

Example 3
On the TAFD40 substrate (made by HOYA Corporation, nd = 2.000), with the structure shown in Table 3, as a first layer to a tenth layer, a SiO ₂ film having a refractive index of 1.481 and a TiO ₂ film having a refractive index of 2.455 at a wavelength of 587.56 nm Were alternately formed by a sputtering method, and a silica airgel film having a refractive index of 1.150 at a wavelength of 587.56 nm was formed as an eleventh layer by a sol-gel method to produce an antireflection film. FIG. 4 shows the 5 ° incident spectral reflectance of this antireflection film.

Example 4
On the S-FPL53 substrate (manufactured by OHARA, Inc., nd = 1.440), a SiO ₂ film having a refractive index of 1.481 and a TiO having a refractive index of 2.455 at a wavelength of 587.56 nm as the first to tenth layers in the configuration shown in Table 4 _Two films were alternately formed by a sputtering method, and a silica airgel film having a refractive index of 1.200 at a wavelength of 587.56 nm was formed as an eleventh layer by a sol-gel method to produce an antireflection film. The 5 ° incident spectral reflectance of this antireflection film is shown in FIG.

Example 5
An SiO ₂ film having a refractive index of 1.481 and a TiO having a refractive index of 2.455 on a S-LAL10 substrate (manufactured by OHARA INC., Nd = 1.720) and having the structure shown in Table 5 and having a refractive index of 1.481 at a wavelength of 587.56 nm as the first to tenth layers. _Two films were alternately formed by a sputtering method, and a silica airgel film having a refractive index of 1.1200 at a wavelength of 587.56 nm was formed as an eleventh layer by a sol-gel method to produce an antireflection film. FIG. 6 shows the 5 ° incident spectral reflectance of this antireflection film.

Example 6
On the TAFD40 substrate (HOYA Co., Ltd., nd = 2.000), with the structure shown in Table 6, as the first to tenth layers, a SiO ₂ film with a refractive index of 1.481 and a TiO ₂ film with a refractive index of 2.455 at a wavelength of 587.56 nm Were alternately formed by a sputtering method, and a silica airgel film having a refractive index of 1.200 at a wavelength of 587.56 nm was formed as an eleventh layer by a sol-gel method to produce an antireflection film. FIG. 7 shows the 5 ° incident spectral reflectance of this antireflection film.

Example 7
On the S-FPL53 substrate (manufactured by OHARA, Inc., nd = 1.440), as shown in Table 7, as a first layer to a tenth layer, a SiO ₂ film having a refractive index of 1.481 and a TiO having a refractive index of 2.455 at a wavelength of 587.56 nm. _Two films were alternately formed by a sputtering method, and a silica airgel film having a refractive index of 1.100 at a wavelength of 587.56 nm was formed as an eleventh layer by a sol-gel method to produce an antireflection film. The 5 ° incident spectral reflectance of this antireflection film is shown in FIG.

Example 8
On the S-LAL10 substrate (manufactured by OHARA, Inc., nd = 1.720), with the structure shown in Table 8, as a first layer to a tenth layer, a SiO ₂ film having a refractive index of 1.481 and a TiO having a refractive index of 2.455 at a wavelength of 587.56 nm _Two films were alternately formed by a sputtering method, and a silica airgel film having a refractive index of 1.100 at a wavelength of 587.56 nm was formed as an eleventh layer by a sol-gel method to produce an antireflection film. FIG. 9 shows the 5 ° incident spectral reflectance of this antireflection film.

Example 9
On the TAFD40 substrate (made by HOYA, nd = 2.000), the SiO ₂ film having a refractive index of 1.481 and the TiO ₂ film having a refractive index of 2.455 at a wavelength of 587.56 nm as the first layer to the tenth layer in the configuration shown in Table 9 Were alternately formed by a sputtering method, and a silica airgel film having a refractive index of 1.100 at a wavelength of 587.56 nm was formed as an eleventh layer by a sol-gel method to produce an antireflection film. FIG. 10 shows the 5 ° incident spectral reflectance of this antireflection film.

Example 10
On the S-FPL53 substrate (manufactured by OHARA, Inc., nd = 1.440), MgF ₂ film having a refractive index of 1.388 and HfO having a refractive index of 1.936 at a wavelength of 587.56 nm as a first layer to a tenth layer in the configuration shown in Table 10 _{The two} films were alternately formed by a vacuum deposition method, and a silica airgel film having a refractive index of 1.150 at a wavelength of 587.56 nm was formed as an eleventh layer by a sol-gel method to produce an antireflection film. FIG. 11 shows the 5 ° incident spectral reflectance of this antireflection film.

Example 11
On the S-LAL10 substrate (manufactured by OHARA, Inc., nd = 1.720), the composition shown in Table 11 is used. As the first to tenth layers, an MgF ₂ film having a refractive index of 1.388 and a HfO having a refractive index of 1.936 at a wavelength of 587.56 nm. _{The two} films were alternately formed by a vacuum deposition method, and a silica airgel film having a refractive index of 1.150 at a wavelength of 587.56 nm was formed as an eleventh layer by a sol-gel method to produce an antireflection film. FIG. 12 shows the 5 ° incident spectral reflectance of this antireflection film.

Example 12
On the TAFD40 substrate (HOYA Co., Ltd., nd = 2.000), with the configuration shown in Table 12, as the first to tenth layers, an MgF ₂ film having a refractive index of 1.388 and a HfO ₂ film having a refractive index of 1.936 at a wavelength of 587.56 nm Were alternately formed by a vacuum deposition method, and a silica airgel film having a refractive index of 1.150 at a wavelength of 587.56 nm was formed as an eleventh layer by a sol-gel method to produce an antireflection film. FIG. 13 shows the 5 ° incident spectral reflectance of this antireflection film.

Comparative Example 1
With reference to Example 1 of Patent Document 1 (Japanese Patent Laid-Open No. 2007-94150), on the S-FPL53 substrate (manufactured by OHARA, Inc., nd = 1.440), the first to fourth layers are configured as shown in Table 13. As a fifth layer, a silica airgel film having a refractive index of 1.150 at a wavelength of 587.56 nm is formed by alternately forming a Ta ₂ O ₅ film having a refractive index of 2.250 and a SiO ₂ film having a refractive index of 1.485 at a wavelength of 587.56 nm. Was formed by a sol-gel method to prepare an antireflection film. FIG. 14 shows the 5 ° incident spectral reflectance of this antireflection film.

Comparative Example 2
With reference to Example 2 of Patent Document 1 (Japanese Patent Laid-Open No. 2007-94150), on the S-LAL7 substrate (manufactured by OHARA, Inc., nd = 1.652), the structure shown in Table 14 and the first layer to the fifth layer As a sixth layer, a silica airgel film having a refractive index of 1.150 at a wavelength of 587.56 nm is formed by alternately forming a Ta ₂ O ₅ film having a refractive index of 2.250 and a SiO ₂ film having a refractive index of 1.485 at a wavelength of 587.56 nm. Was formed by a sol-gel method to prepare an antireflection film. FIG. 15 shows the 5 ° incident spectral reflectance of this antireflection film.

  The antireflection films of Comparative Examples 1 and 2 have a spectral reflectance of 5 ° incidence with respect to light in the visible range of 400 to 700 nm exceeding 0.01%, whereas the antireflection films of Examples 1 to 12 of the present invention Indicates that the spectral reflectance at 5 ° incidence with respect to light in the visible range of 400 to 700 nm is 0.01% or less, and has excellent low reflection characteristics.

  FIG. 16 shows representative values of refractive index dispersion at 350 to 750 nm of the materials used in Examples 1 to 12 and Comparative Examples 1 and 2. The silica airgel was omitted because the refractive index dispersion at a wavelength of 350 to 750 nm was negligibly small. As can be seen from these refractive index dispersions, the refractive index tends to increase on the short wavelength side in the visible region. The refractive index dispersion curve in FIG. 16 is obtained by plotting, as a representative value, an average value obtained by actually measuring a single layer coating film for the film material.

Comparative Example 3
Is it possible to obtain an antireflection film having a reflectance of 0.01% or less at a wavelength of 400 to 700 nm in the visible region by further optimizing the antireflection film having a 12-layer structure disclosed in Patent Document 3 (JP 2013-250295)? I confirmed. On the S-LAH53 substrate (manufactured by OHARA, Inc., nd = 1.806), Ta ₂ O ₅ (refractive index: 2.22), SiO ₂ with the same layer configuration (antireflection film 1 in Table 15) as Example 3 of Patent Document 3. _A 12-layer antireflection film composed of ₂ (refractive index 1.45) and an ultra-low refractive index film (refractive index 1.25) was constructed. The calculation result of the 5 ° incident spectral reflectance is shown by a solid line in Fig. 17-1. On the other hand, a 12-layer antireflection film (antireflection film 2 in Table 15) in which the optical film thickness of each layer was optimized by the gradient gradient method was configured so that the reflectance at a wavelength of 390 to 710 nm was as low as possible. . The calculation results of the 5 ° incident spectral reflectance are shown by chain lines in FIGS. 17-1 and 17-2.

  As is clear from FIGS. 17-1 and 17-2, the present embodiment can be achieved by simply adjusting and optimizing the optical film thickness of the 12-layer antireflection film of Japanese Patent Application Laid-Open No. 2013-250295. Thus, an antireflection film having a reflectance of 0.01% or less at a wavelength of 400 to 700 nm could not be obtained.

1. Antireflection film
101 ... 1st layer
102 ... 2nd layer
103 ... 3rd layer
104 ... 4th layer
105 ... 5th layer
106 ・ ・ ・ 6th layer
107 ... 7th layer
108 ・ ・ ・ 8th layer
109 ... 9th layer
110 ... 10th layer
111 ... 11th layer 2 ... Substrate

Claims (7)

An antireflection film for a visible wavelength of 400 to 700 nm formed by sequentially laminating a first layer to an eleventh layer on a substrate,
The first to tenth layers are formed by alternately laminating a high refractive index film and a low refractive index film having a lower refractive index than the high refractive index film, and the eleventh layer is formed from the low refractive index film. An antireflection film comprising an ultra-low refractive index film having a lower refractive index.   2. The antireflection film according to claim 1, wherein the first layer is composed of a low refractive index film.   3. The antireflection film according to claim 1, wherein the substrate has a refractive index of 1.43 to 2.01, the low refractive index film has a refractive index of 1.37 to 1.51, and the high refractive index film has a refractive index of 1.9. An antireflection film characterized by being -2.5. In the antireflection film according to any one of claims 1 to 3,
The refractive index of the first layer is 1.37 to 1.51 and the optical film thickness is 4 to 90 nm,
The refractive index of the second layer is 1.9 to 2.5 and the optical film thickness is 4 to 130 nm,
The third layer has a refractive index of 1.37 to 1.51 and an optical film thickness of 20 to 120 nm,
The refractive index of the fourth layer is 1.9 to 2.5 and the optical film thickness is 30 to 100 nm,
The refractive index of the fifth layer is 1.37 to 1.51 and the optical film thickness is 20 to 70 nm,
The refractive index of the sixth layer is 1.9 to 2.5 and the optical film thickness is 80 to 160 nm,
The refractive index of the seventh layer is 1.37 to 1.51 and the optical film thickness is 4 to 40 nm,
The refractive index of the eighth layer is 1.9 to 2.5 and the optical film thickness is 50 to 190 nm,
The refractive index of the ninth layer is 1.37 to 1.51 and the optical film thickness is 40 to 140 nm,
The refractive index of the tenth layer is 1.9 to 2.5 and the optical film thickness is 4 to 50 nm,
An antireflection film, wherein the eleventh layer has a refractive index of 1.05 to 1.3 and an optical film thickness of 130 to 150 nm. The antireflection film according to claim 1,
The low refractive index film is a film made of a material selected from the group consisting of MgF ₂ , SiO ₂ , a mixture of SiO ₂ and Al ₂ O ₃ , a fluororesin,
Mixtures of the high refractive index film is _{TiO 2, Nb 2 O 5,} TiO 2 and _{Nb 2 O 5, Ta 2 O} 5, ZrO 2, HfO 2, CeO 2, La 2 O 3, ZnO, SnO 2, In 2 A material selected from the group consisting of O ₃ , ZnS, a mixture of In ₂ O ₃ and SnO _2, a mixture of ZnO and Al ₂ O _3, a mixture of ZnO and Ga ₂ O _{3, and} a mixture of TiO ₂ and La ₂ O ₃ A membrane consisting of
An antireflection film, wherein the ultra-low refractive index film is a nanoporous film or a nanoparticle film made of a material selected from the group consisting of MgF ₂ , SiO ₂ , Al ₂ O ₃ and a fluororesin.   6. The antireflection film according to claim 1, wherein the refractive index of the first layer is lower than the refractive index of the substrate.   An optical component comprising the antireflection film according to claim 1.

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