JPH0618705A - Optical element - Google Patents

Abstract

PURPOSE:To obtain an excellent antireflection property by providing a first layer of a high-refractive index material and second layer of amorphous transparent fluororesin which are respectively specified in refractive index as antireflection films. CONSTITUTION:A transparent substrate 1 has the first layer 2 of the high- refractive index material of >=1.58 refractive index and the second layer 3 of the amorphous transparent fluororesin of <=1.3 refractive index as the antireflection films thereon successively toward the air from the substrate 1 side. Namely, the fluororesin which has the refractive index (nd <=1.35) lower than the refractive index of MgF2, is soluble in an org. solvent, is amorphous and, is therefore, transparent to visible light and near IR light is used for the air side layer of the two-layered antireflection films of the optical element, by which the optical element having the excellent antireflection effect is obtd. The amorphous transparent fluororesin is soluble in the org. solvent and, therefore, the formation of the antireflection films by solvent coating, such as dip coating and spin coating, is possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element having an antireflection film such as a lens and a filter.

[0002]

2. Description of the Related Art Conventionally, an antireflection film for an optical element such as a lens which requires an antireflection effect is formed by alternately vacuum depositing a high refractive index substance such as TiO ₂ and ZrO ₂ and a low refractive index substance such as MgF _2. And a multi-layered film formed by a coating method. Especially for the layer on the air side, a material having a lower refractive index is better, and nd = 1.38.
Of MgF ₂ have been used. nd is a refractive index for light having a wavelength of 587 nm.

[0003]

However, as a substance having a lower refractive index than MgF ₂ , there is a crystalline fluororesin (eg, polytetrafluoroethylene, nd = 1.35).
Since it has poor moldability and is insoluble in (general) organic solvents, it could not be applied to thin films such as antireflection films.

Therefore, an object of the present invention is to provide an optical element having an excellent antireflection property by using a layer having a lower refractive index than the MgF ₂ layer as a layer in contact with the air of the antireflection layer of the optical element. is there.

Another object of the present invention is to provide an optical element having an antireflection film which can be formed by solution coating such as dipping coating or spin coating.

Another object of the present invention is to provide an optical element having excellent adhesion between an antireflection film and a transparent substrate.

[0007]

An optical element according to the present invention is a first layer of a high refractive index substance having a refractive index of 1.58 or more on a transparent substrate as an antireflection film from the substrate side toward the air. And a second layer of an amorphous transparent fluororesin having a refractive index of 1.35 or less.

The present invention has a lower refractive index (nd) than MgF _2.
= 1.35 or less), is soluble in an organic solvent, and
Since it is amorphous, a fluororesin that is transparent to visible light and near-infrared light is used for the air-side layer of the two-layer antireflection film of an optical element to provide an optical element having an excellent antireflection effect. Can be provided. Further, since the amorphous transparent fluororesin is soluble in an organic solvent, the antireflection film can be formed by solution coating such as dip coating and spin coating.

In the present invention, the surface of the transparent substrate made of glass or polymer resin, or the surface of the first layer made of a high refractive index material of nd = 1.58 or more, is subjected to ozone treatment by ultraviolet irradiation, corona discharge treatment, plasma. By providing a surface treatment such as treatment or providing an adhesive layer, an optical element having an antireflection film with improved adhesion can be provided.

The optical element according to the present invention is made of glass or
A first layer of a high refractive index material having a refractive index of 1.58 or more and an amorphous transparent material having a refractive index of 1.35 or less as an antireflection film on a transparent substrate of polymer resin from the substrate side toward air. It has a second layer of fluororesin.

The preferred thickness of the first layer is

[0012]

[Outside 4] Or

[0013]

[Outside 5] And the preferred thickness of the second layer is

[0014]

[Outside 6] Is. (K and L are positive odd numbers, n ₁ is the refractive index of the first layer,
d ₁ is the film thickness of the first layer, n ₂ is the refractive index of the second layer, d ₂ is the film thickness of the second layer, and λ ₁ and λ ₂ are the same or almost the same as the design wavelength from the region of 400 to 900 nm. Optical thickness n of selected)
It is an antireflection film for an optical element, which satisfies ₁ d ₁ and n ₂ d ₂ . When λ ₁ and λ ₂ are almost the same, λ ₁ = λ ₂ ± 10 nm, especially λ ₁ = λ ₂ ± 5n
m is suitable.

FIG. 1 is a cross-sectional view of an optical element having an antireflection film according to the present invention, in which a transparent substrate 1 is provided with a first layer 2 and a second layer.
The layer 3 is formed.

FIG. 2 is a cross-sectional view of an optical element of the present invention in which an adhesive layer is provided between the respective layers. The adhesive layer 4 is provided between the transparent substrate 1 and the first layer 2, and the first layer 2 and the second layer. The adhesive layer 5 is provided between the layers 3.

The first layer and the second layer are preferably formed by coating a transparent substrate with a coating material in which the layer forming material is dispersed or dissolved in an organic solvent.

The glass used for the transparent substrate of the present invention is
There are optical glass used for lenses and the like, and quartz glass used for filters and the like, and as the polymer resin, polymethylmethacrylate, polystyrene, polycarbonate, polyolefin, or a copolymer composed of two or more of these, etc. can give.

As the high refractive index material used for the first layer from the substrate side toward the air side, nd = 1.58 or more,
It is preferably higher than the refractive index of the substrate. nd is d of Na
It is a refractive index for a line (587 nm).

For example, as the inorganic substance, Ti, Ce, Z
Oxides of metals such as r, Sn, Sb and Ta are used. The film formation of these metal oxides is carried out by a dip coating method using a coating liquid comprising 1 to 100 nm metal oxide fine particles, a binder such as tetraalkoxysilane and a stabilizer for the fine particles, and an organic solvent as a dispersion medium for these. Alternatively, it is applied by a spin coating method and heated to form a film.

As the organic substance, polymer resins such as polystyrene, polycarbonate, polystyrene derivatives, polycarbonate derivatives and polymethylmethacrylate derivatives are used. As these derivatives, polystyrene, polycarbonate and polymethylmethacrylate are chemically bonded to each other. Alternatively, a polymer resin having a refractive index increased by physically containing a sulfur atom, a halogen atom, or a polycyclic aromatic is used. Films of these polymeric resins can be formed from aromatics such as toluene, esters such as isobutyl acetate, alcohols such as isopropyl alcohol, ketones such as methyl ethyl ketone, ethers such as diisopropyl ether, or mixtures thereof. A film is formed by applying a coating solution of a polymer resin dissolved in an organic solvent by a dip coating method and heating and drying.

The concentration, viscosity, etc. of the coating liquid prepared by dissolving or dispersing the metal oxide fine particles or the polymer resin used here may be appropriately changed depending on the desired film thickness, but preferably 1 to 15 cps. Those having a viscosity range of (20 ° C.) are most suitable because they cause less film unevenness due to the dip coating method or the spin coating method.

The amorphous nature of the amorphous transparent fluororesin used for forming the second layer is confirmed by the fact that a transparent film can be formed when it is formed. It can also be confirmed by the fact that crystals are not substantially observed by crystal analysis by X-ray.

Preferred amorphous transparent fluororesins soluble in organic solvents include polymers having the following repeating units of the main chain.

[0025]

[Outside 7] (However, m, m ′, n, and n ′ are positive integers), and at least one of fluorine atoms in the repeating unit is an amino group, an aldehyde group, a carboxyl group, an alcohol group, At least one selected from a silanol group, a phosphonyl group, a sulfonyl group, a cyano group, a nitro group, a vinyl group, an epoxy group, and a fluorine compound such as perfluoroalkyl, perfluoroalkyl ether, and perfluoroalkene having a functional group at the end. Will be replaced. Alternatively, the repeating unit represented by the above formula and at least one fluorine atom in the repeating unit represented by the above formula is an amino group, an aldehyde group, a carboxyl group, an alcohol group,
Substitute with at least one selected from fluorine compounds such as silanol groups, phosphonyl groups, sulfonyl groups, cyano groups, nitro groups, vinyl groups, epoxy groups and terminal functional groups such as perfluoroalkyl, perfluoroalkyl ether, and perfluoroalkene. A fluoropolymer resin composed of a copolymer with the repeating unit can be used.

The functional groups at the ends of the above-mentioned fluorine compounds include amino groups, aldehyde groups, carboxyl groups, alcohol groups, silanol groups, phosphonyl groups, sulfonyl groups, cyano groups, nitro groups, vinyl groups, epoxy groups. And so on.

The above-mentioned amorphous transparent fluororesin is an aromatic such as toluene, a ketone such as methyl ethyl ketone,
Soluble in an organic solvent such as an ester such as isobutyl acetate, an ether such as diisopropyl ether, an alcohol such as isopropyl alcohol, or a mixture thereof, or a fluorocarbon solvent such as tetradecafluorohexane or octadecafluorooctane. It is possible to In particular, the fluorocarbon solvent does not attack the high-refractive-index polymer resin of the first layer and has a high solubility of the amorphous transparent fluororesin, and the amorphous transparent fluororesin prepared by the dip coating method or the spin coating method is used. Suitable for film formation.

The concentration, viscosity, etc. of the amorphous transparent fluororesin solution will vary depending on the desired film thickness.
1 to 15 cps (2
A solution with a viscosity of 0 ° C.) is preferred.

Further, in the present invention, a transparent substrate of glass or polymer resin, and a metal oxide of a high refractive index substance, or
As the surface treatment for improving the adhesiveness applied to the first layer made of a polymer resin, ozone is generated by ultraviolet irradiation,
Surface modification techniques such as ultraviolet-ozone treatment for activating the surface with ozone, corona discharge treatment, and plasma treatment are used. In addition to this, electron beam or ion beam irradiation is also effective.

Further, between the transparent substrate of glass or polymer resin and the first layer of metal oxide of high refractive index material or polymer resin, and between the first layer and the non-refractive index non-reflecting layer. Examples of the adhesive used for the adhesive layer between the second layers made of a crystalline transparent fluororesin include N-β (aminoethyl) γ-aminopropyltrimethoxysilane and N-β (aminoethyl) γ
-Aminopropylmethyldimethoxysilane, γ-aminopropyltriethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, β- (3,4epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane , A silane coupling agent having a reactive functional group such as γ-glycidoxypropylmethyldimethoxysilane, γ- (methacryloxypropyl) trimethoxysilane, isopropyltrioctanoyl titanate, tetra (2,2-diallyloxymethyl- A titanate coupling agent such as 1-butyl) bis (ditridecyl) phosphite titanate, dicumylphenyloxyacetate titanate, diisostearoyl ethylene titanate,

[0031]

[Outside 8] Zircoaluminate coupling agent represented by, or
Methacrylate monomers such as isobutyl methacrylate, glycidyl methacrylate, polypropyl glycol methacrylate, glycerol monomethacrylate can be used.

As a preferable method for improving the adhesion between the transparent substrate and the first layer and / or between the first layer and the second layer, the first layer and / or the second layer are (1 ) Through the transparent substrate and / or the first layer and the adhesive layer, (2) the surface of the transparent substrate and / or the surface of the first layer is subjected to ultraviolet-ozone treatment, and (3)
The transparent substrate surface and / or the first layer surface is subjected to corona discharge treatment, (4) the transparent substrate surface and / or the first layer surface is subjected to plasma treatment, and (5) the transparent substrate surface and / or the first layer surface is treated. After the ultraviolet-ozone treatment, (6) through the adhesive layer, the transparent substrate surface and / or the surface of the first layer is subjected to corona discharge treatment, through the adhesive layer, or (7) the transparent substrate surface and / or the first layer. A method in which the layer surface is subjected to plasma treatment and then formed via an adhesive layer may be used.

[0033]

【Example】

(Example 1) A glass substrate (BK7, n
d = 1.517, 76 × 24 × 1 mm) to N-β (aminoethyl) γ-aminopropyltrimethoxysilane, 1
60 m after soaking in a wt% ethanol solution for 30 minutes
It was pulled up at a speed of m / min, dried at 80 ° C. for 30 minutes, washed with ethanol, and dried for silane coupling treatment. 3% by weight of polystyrene (nd = 1.592 (trade name: Stylon G8259, manufactured by Asahi Kasei Co., Ltd.) of the glass substrate subjected to the silane coupling treatment,
After immersing in a toluene solution for 2 minutes, it is pulled up at a speed of 90 mm / min, dried at 150 ° C. for 30 minutes, and then 166
A first layer having a thickness of nm was formed. The k value of the first layer is 1.
This sample was further immersed in a 1 wt% ethanol solution of γ-aminopropyltrimethoxysilane for 30 minutes, and then 60
It was pulled up at a speed of mm / min, dried at 80 ° C. for 30 minutes, and washed with ethanol. Continue to repeat this sample

[0034]

[Outside 9] (N and m are positive integers) fluororesin (nd = 1.338
(Product name: CYTOP-CTX, manufactured by Asahi Glass Co., Ltd.) was soaked in a 2% by weight octadecafluorooctane solution for 2 minutes, then pulled up at a speed of 80 mm / min, and at 150 ° C.
Drying was performed for 0 minutes to form a second layer having a thickness of 99 nm.
The L value of the second layer is 1.

The glass substrate on which this antireflection film is formed is
In the visible light region of 400 to 700 nm, a spectral characteristic of reflectance of 1.5% or less and transmittance of 98% or more was exhibited.

The results are shown in FIG.

Comparative Example A silane coupling treatment was carried out on a glass substrate in the same manner as in Example 1, and then a fluororesin layer was formed directly in the same manner as in Example 1 without forming the first layer of polystyrene. Then, an optical element was manufactured. The reflectance characteristic of this optical element is shown in FIG. As shown in FIG. 4, the reflectance in the visible light region of 400 to 700 nm showed a large value of about 1.5% to about 3.6%.

Example 2 Acrylic resin lens (polymethylmethacrylate, nd, washed with IPA)
= 1.492, diameter 27 mm, effective diameter 23 mm, convex radius of curvature 60.24, concave radius of curvature 37.67) was soaked in 3% by weight of polystyrene (trade name: Styron G8259) in isobutyl acetate solution for 20 seconds, 90 mm
It was pulled up at a speed of / min and dried at 60 ° C. for 20 minutes to form a first layer having a thickness of 166 nm. The K value of the first layer is 1. Furthermore, this sample is output 250w, oxygen flow rate 5
Plasma treatment for 10 minutes at 00 sccm and 1 Torr

[0039]

[Outside 10] (M and n are positive integers) Soaked in a 2 wt% octadecafluorooctane solution of fluororesin (trade name: Cytop CTX) for 2 minutes, then pulled up at a speed of 80 mm / min and dried at 60 ° C. for 2 hours. Then, a second layer having a thickness of 99 nm was formed. The L value of the second layer is 1.

The acrylic resin lens on which this antireflection film was formed exhibited spectral characteristics with a reflectance of 1.3% or less and a transmittance of 98% or more in the visible light region of 400 to 700 nm.

Example 3 A glass substrate that has been thoroughly washed (BK7, nd = 1.517, 76 × 24 × 1 mm)
UV irradiation and ozone treatment (25 w, 3 lights, ozone concentration 3 minutes after 230 ppm) on each side for 3 minutes, ZrO ₂ with an average particle size of 15 ± 1 nm, 3% by weight, tetraethoxysilane 9.6% by weight %, Silicon-based surfactant 1% by weight, water 1% by weight, hydrochloric acid 0.4% by weight, ethyl acetate 25% by weight, and ethanol 60% by weight, after being immersed for 2 minutes in a coating solution, the speed is 240 mm / min. It was pulled up, dried at 120 ° C. for 30 minutes, and further dried at 250 ° C. for 60 minutes to form a first layer having a thickness of 160 nm. The K value of the first layer is 1. When the refractive index of this film was measured, it was nd = 1.66. This sample was subjected to UV irradiation-ozone treatment on both sides for 3 minutes on each side, and then repeated units

[0042]

[Outside 11] (M and n are positive integers) fluororesin (nd = 1.31)
(Product name: Teflon AF1600, manufactured by DuPont) 3
After dipping in a wt% octadecafluorooctane solution for 2 minutes, it was pulled up at a rate of 60 mm / min and dried at 180 ° C. for 60 minutes to form a second layer having a thickness of 99 nm.
The L value of the second layer is 1.

The glass substrate on which this antireflection film is formed is
In the visible light region of 400 to 700 nm, a spectral characteristic of reflectance of 1.5% or less and transmittance of 98% or more was exhibited.

The results are shown in FIG.

Example 4 A sufficiently washed quartz substrate (nd = 1.458, 76 × 24 × 1 mm) was immersed in a 1% by weight ethanol solution of γ-aminopropyltriethoxysilane for 30 minutes. At a rate of 60 mm / min, dried at 80 ° C. for 30 minutes, washed with ethanol and dried for silane coupling treatment.
This silane coupling-treated quartz substrate is made of polycarbonate (nd = 1.583) (trade name: Panlite A)
D5503 (manufactured by Teijin Kasei Co., Ltd.) was dipped in a toluene solution for 2 minutes, then pulled up at a speed of 70 mm / min and dried at 150 ° C. for 30 minutes to form a first layer having a thickness of 123 nm. The K value of the first layer is 1. This quartz plate was further immersed in a 1% by weight ethanol solution of γ-aminopropyltriethoxysilane for 30 minutes, and then 60 mm /
It was pulled up at a rate of min, dried at 80 ° C. for 30 minutes, and washed with ethanol. Continue to repeat this sample

[0046]

[Outside 12] After soaking in a 2 wt% octadecafluorooctane solution of a fluororesin (trade name: Cytop CTX) of (n and m are positive integers) for 2 minutes, it is pulled up at a speed of 60 mm / min and dried at 150 ° C. for 60 minutes. Then, a second layer having a thickness of 146 nm was formed. The L value of the second layer is 1.

The quartz substrate on which this antireflection film is formed is 7
In the near infrared region of 00 to 900 nm, the reflectance is 1% or less,
It showed spectral characteristics with a transmittance of 98% or more. This result is shown in FIG.
Shown in.

[0048]

As described above, the antireflection film of the optical element according to the present invention has a large antireflection effect and good adhesion.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an optical element provided with an antireflection film of the present invention.

FIG. 2 is a sectional view of an optical element provided with an antireflection film via an adhesive layer of the present invention.

3 is a measurement diagram of reflectance of the optical element of Example 1. FIG.

FIG. 4 is a measurement diagram of reflectance of an optical element of a comparative example.

5 is a measurement diagram of reflectance of the optical element of Example 3. FIG.

6 is a measurement diagram of reflectance of the optical element of Example 4. FIG.

Claims (9)

[Claims] 1. A first layer of a high refractive index material having a refractive index of 1.58 or more and an amorphous material having a refractive index of 1.35 or less as an antireflection film on a transparent substrate from the substrate side toward air. An optical element having a second layer of transparent fluororesin. 2. The optical element according to claim 1, wherein the first layer and the second layer are formed by coating a transparent substrate with a coating material in which a layer forming material is dispersed or dissolved in an organic solvent. 3. The first layer comprises (1) a transparent substrate and an adhesive layer, (2) an ultraviolet-ozone treatment on the transparent substrate surface, and (3) a corona discharge treatment on the transparent substrate surface. 4) Plasma-treating the transparent substrate surface, (5) UV-ozone-treating the transparent substrate surface through the adhesive layer, (6) Corona discharge treating the transparent substrate surface through the adhesive layer, or (7) The optical element according to claim 1 or 2, which is formed through a bonding layer after plasma-treating the surface of the transparent substrate. 4. The second layer is (1) via the first layer and the cutting layer, (2) the surface of the first layer is subjected to ultraviolet-ozone treatment, and (3) the surface of the first layer is subjected to corona discharge treatment. Then, (4) the surface of the first layer is subjected to plasma treatment, (5) the surface of the first layer is subjected to ultraviolet-ozone treatment, and then through an adhesive layer, (6) the surface of the first layer is subjected to corona discharge treatment, and then adhered. Via the layer, or (7) after the plasma treatment of the surface of the first layer, via the adhesive layer,
The optical element according to claim 1 or 2, which is formed. 5. The first layer comprises: Or [outside 2] The second layer is [External 3] (K and L are positive odd numbers, n ₁ is the refractive index of the first layer, d ₁ is the thickness of the first layer, n ₂ is the refractive index of the second layer, d ₂ is the thickness of the second layer, λ ₁ and λ ₂ are designed wavelengths that are the same or almost the same, 400-
The optical element according to claim 1 or _2, which satisfies an optical film thickness n ₁ d ₁ and n ₂ d _{2 (} selected from a region of 900 nm). 6. The optical element according to claim 1, wherein the first layer contains metal oxide fine particles and a binder. 7. The metal oxide is Ti, Ce, Zr, Sn,
The optical element according to claim 6, which is an oxide of a metal selected from Sb and Ta. 8. The optical element according to claim 1, wherein the first layer is a polymer resin layer. 9. The optical element according to claim 8, wherein the polymer resin is selected from polystyrene, polycarbonate, polystyrene derivatives, polycarbonate derivatives, and polymethylmethacrylate derivatives.