CN110967781A - Optical element for terahertz wave and method for manufacturing same - Google Patents

Optical element for terahertz wave and method for manufacturing same Download PDF

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CN110967781A
CN110967781A CN201910903036.3A CN201910903036A CN110967781A CN 110967781 A CN110967781 A CN 110967781A CN 201910903036 A CN201910903036 A CN 201910903036A CN 110967781 A CN110967781 A CN 110967781A
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antireflection film
adhesive layer
olefin polymer
layer
optical member
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CN110967781B (en
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河田阳一
高桥宏典
池田吉纪
添田淳史
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Hamamatsu Photonics KK
Teijin Ltd
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Hamamatsu Photonics KK
Teijin Ltd
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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
    • G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
    • G02B1/11—Anti-reflection coatings
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
    • G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
    • G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
    • G02B1/11—Anti-reflection coatings
    • G02B1/111—Anti-reflection coatings using layers comprising organic materials
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
    • G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
    • G02B1/11—Anti-reflection coatings
    • G02B1/113—Anti-reflection coatings using inorganic layer materials only
    • G02B1/115—Multilayers

Abstract

The present invention provides an optical element for terahertz waves, which includes: an optical component having a silicon surface; an antireflection film having an organic resin containing a cyclic olefin polymer as a main component and inorganic particles dispersed in the organic resin; and an adhesive layer which is positioned between the optical member and the antireflection film in the thickness direction of the antireflection film and bonds the silicon surface of the optical member and the antireflection film. The adhesive layer contains a thermally modified olefin polymer.

Description

Optical element for terahertz wave and method for manufacturing same
Technical Field
The present invention relates to an optical element for terahertz waves and a method for manufacturing the same.
Background
In recent years, in order to realize nondestructive and noncontact inspection techniques using an electromagnetic wave (terahertz wave) in the terahertz band, an optical element (for example, a lens, a polarizing plate, or the like) usable in the terahertz band has been developed. Non-patent documents (Gongjie Xu, et al, "0.1-20 THz ultra-wideband perfect absorber material realized by multilayer structure (0.1-20THz ultra-wideband absorber via a flat multi-layer structure)", "optical Express 24,23177(2016)) disclose complete absorbers (absorbers) of terahertz waves. The above non-patent document discloses a form in which an antireflection film having a refractive index adjusted by titanium oxide fine particles or hollow polystyrene spheres is provided on a highly doped silicon substrate. From the viewpoint of making the antireflection film adhere well to the silicon substrate, an epoxy polymer is used as a main component of the antireflection film.
Epoxy polymers exhibit the property of absorbing terahertz waves. Therefore, when the antireflection film disclosed in the above-mentioned non-patent document is applied to an optical element that is intended to transmit terahertz waves, a problem may occur.
Disclosure of Invention
An optical element for terahertz waves according to an aspect of the present invention includes: an optical component having a silicon surface; an antireflection film having an organic resin containing a cyclic olefin polymer as a main component and inorganic particles dispersed in the organic resin; and an adhesive layer that is positioned between the optical component and the antireflection film in the thickness direction of the antireflection film and bonds the silicon surface of the optical component and the antireflection film, wherein the adhesive layer contains a thermally modified olefin polymer.
According to the optical element for terahertz waves, the organic resin contained in the antireflection film contains the cyclic olefin polymer as a main component. The antireflection film exhibits better permeability to terahertz waves than when an organic resin containing an epoxy polymer as a main component is used. On the other hand, cyclic olefin polymers tend to have lower adhesion to silicon than epoxy polymers. Therefore, when an antireflection film having an organic resin containing a cyclic olefin polymer as a main component is formed only on a silicon surface, there is a possibility that the antireflection film cannot be formed satisfactorily. In contrast, according to the optical device for terahertz waves, the antireflection film and the silicon surface of the optical member are bonded to each other via the adhesive layer containing the olefin polymer after thermal modification. The olefin polymer after thermal modification can maintain the permeability to terahertz waves and can improve the adhesion to silicon. By using such an adhesive layer containing the thermally modified olefin polymer, the anti-reflection film can be favorably fixed to the silicon surface while suppressing absorption of terahertz waves by the adhesive layer. Therefore, it is possible to provide a terahertz wave optical element having an antireflection film exhibiting good transmittance for terahertz waves with high reliability.
An optical element for terahertz waves according to another aspect of the present invention includes: an optical member; an antireflection film having an organic resin containing a cyclic olefin polymer as a main component and inorganic particles dispersed in the organic resin; and an adhesive layer which is positioned between the optical member and the antireflection film in the thickness direction of the antireflection film and bonds the surface of the optical member and the antireflection film, wherein the adhesive layer contains a thermally modified olefin polymer.
According to the optical element for terahertz waves, the organic resin contained in the antireflection film contains the cyclic olefin polymer as a main component. The antireflection film exhibits better permeability to terahertz waves than when an organic resin containing an epoxy polymer as a main component is used. On the other hand, when an antireflection film having an organic resin containing a cyclic olefin polymer as a main component is formed on an optical member, unlike the case of using an antireflection film having an organic resin containing an epoxy polymer as a main component, depending on the material constituting the surface of the optical member, there is a possibility that the antireflection film cannot be formed satisfactorily on the surface. In contrast, according to the optical element for terahertz waves described above, the antireflection film and the surface of the optical member are bonded to each other via the adhesive layer containing the olefin polymer after thermal modification. The thermally modified olefin-based polymer tends to have the following properties: that is, it exhibits not only good adhesion to organic resins such as olefin polymers but also good adhesion to materials to which olefin polymers that have not been thermally modified are difficult to adhere. In addition, the olefin polymer after thermal modification has good permeability to terahertz waves. By using such an adhesive layer containing the olefin polymer after thermal modification, the anti-reflection film can be favorably fixed to the surface of the optical member while suppressing absorption of terahertz waves by the adhesive layer. Therefore, it is possible to provide a terahertz wave optical element having an antireflection film exhibiting good transmittance for terahertz waves with high reliability.
It can also be: the volume ratio of the inorganic particles per unit volume of the antireflection film is higher as it approaches the optical member in the thickness direction. In this case, the refractive index of the antireflection film can be made closer to silicon as the optical member is closer to the optical member in the thickness direction. Therefore, reflection of terahertz waves on the silicon surface can be suppressed.
It can also be: the antireflection film has a plurality of layers laminated with each other in the thickness direction, each of the plurality of layers containing an organic resin containing a cyclic olefin polymer as a main component and inorganic particles dispersed in the organic resin, and the proportion of the volume of the inorganic particles in each unit volume of the layer is higher as the layer is closer to the optical member in the thickness direction. In this case, the refractive index of the antireflection film can be made closer to silicon as the film is closer to the optical member in the thickness direction, and thus reflection of terahertz waves on the silicon surface can be suppressed. Further, the refractive index of the antireflection film in the thickness direction can be changed easily and reliably in a stepwise manner.
The antireflection film may have: the optical element for terahertz waves further includes a bubble-containing layer that is located on the second surface and contains a plurality of bubbles. In this case, the reflection of the terahertz wave on the second surface of the antireflection film can be favorably suppressed by the bubble-containing layer. The surface of the bubble-containing layer may have a concavo-convex shape. In this case, the reflection of the terahertz wave on the surface of the bubble-containing layer can be suppressed well.
The antireflection film may have: the optical member includes a first surface facing the optical member in a thickness direction, and a second surface located on an opposite side of the first surface, and the second surface has a concave-convex shape. In this case, reflection of terahertz waves on the second surface of the antireflection film can be suppressed.
The thickness of the adhesive layer may be 1nm or more and 100 μm or less. In this case, the antireflection film can be favorably fixed to the silicon surface via the adhesive layer, and the absorption of terahertz waves by the adhesive layer can be favorably suppressed.
The inorganic particles may also be silicon particles, titanium oxide particles, or diamond particles. In this case, the refractive index of the antireflection film can be adjusted by the inorganic particles while suppressing absorption of terahertz waves by the antireflection film.
In still another aspect of the present invention, a method for manufacturing an optical element for terahertz waves includes: preparing an optical member having a silicon surface; forming an adhesive layer containing an olefin polymer on a silicon surface of an optical member; a step of thermally modifying the olefin polymer contained in the adhesive layer by heating and bringing the adhesive layer into close contact with the silicon surface; and a step of bonding an antireflection film having an organic resin containing a cyclic olefin polymer as a main component and inorganic particles dispersed in the organic resin to the optical member via an adhesive layer containing the thermally modified olefin polymer.
The cyclic olefin polymer exhibits better permeability to terahertz waves than the epoxy polymer, but tends to have poor adhesion to silicon. Therefore, when only an antireflection film having an organic resin containing a cyclic olefin polymer as a main component is formed on a silicon surface, there is a possibility that the antireflection film cannot be formed satisfactorily. In contrast, according to the above production method, after the adhesive layer containing the olefin polymer thermally modified by heating is brought into close contact with the silicon surface of the optical member, the antireflection film is bonded to the optical member via the adhesive layer. The olefin polymer after thermal modification can maintain the permeability to terahertz waves and can improve the adhesion to silicon. By using such an adhesive layer containing the thermally modified olefin polymer, the anti-reflection film can be favorably fixed to the silicon surface while suppressing absorption of terahertz waves by the adhesive layer. Therefore, an optical element for terahertz waves having an antireflection film exhibiting good permeability to terahertz waves can be manufactured with high reliability.
In still another aspect of the present invention, a method for manufacturing an optical element for terahertz waves includes: a step of preparing an optical component; forming an adhesive layer containing an olefin polymer on a surface of an optical member; a step of thermally modifying the olefin polymer contained in the adhesive layer by heating and bringing the adhesive layer into close contact with the surface; and a step of bonding an antireflection film having an organic resin containing a main component of a cyclic olefin polymer and inorganic particles dispersed in the organic resin to the optical member via an adhesive layer containing the thermally modified olefin polymer.
The cyclic olefin polymer exhibits better permeability to terahertz waves than the epoxy polymer. On the other hand, when an antireflection film having an organic resin containing a cyclic olefin polymer as a main component is formed on an optical member, unlike the case of using an antireflection film having an organic resin containing an epoxy polymer as a main component, depending on the material constituting the surface of the optical member, there is a possibility that the antireflection film cannot be formed satisfactorily on the surface. In contrast, according to the above production method, after the adhesive layer containing the olefin polymer thermally modified by heating is brought into close contact with the surface of the optical member, the antireflection film is bonded to the optical member via the adhesive layer. The thermally modified olefin-based polymer tends to have the following properties: that is, the adhesive composition exhibits good adhesion not only to an organic resin such as an olefin polymer but also to a material which is not easily adhered to an olefin polymer which has not been thermally modified. In addition, the olefin polymer after thermal modification has good permeability to terahertz waves. By using such an adhesive layer containing the olefin polymer after thermal modification, the anti-reflection film can be favorably fixed to the surface of the optical member while suppressing absorption of terahertz waves by the adhesive layer. Therefore, an optical element for terahertz waves having an antireflection film exhibiting good permeability to terahertz waves can be manufactured with high reliability.
Drawings
Fig. 1 is a schematic cross-sectional view showing an optical element according to an embodiment.
Fig. 2 is a flowchart for explaining a method of manufacturing an optical element according to the embodiment.
Fig. 3 is a schematic cross-sectional view showing an optical element according to a first modification.
Fig. 4A is a schematic cross-sectional view showing an optical element according to a second modification.
Fig. 4B is a diagram showing an example of the surface of the optical element according to the second modification.
Fig. 5 is a schematic cross-sectional view showing an optical element according to a third modification.
Fig. 6 is a schematic cross-sectional view showing an optical element according to a fourth modification.
Fig. 7 is a schematic cross-sectional view showing an optical element according to a fifth modification.
Detailed Description
Hereinafter, preferred embodiments of one aspect of the present invention will be described in detail with reference to the accompanying drawings. In the following description, the same elements or elements having the same function are denoted by the same reference numerals, and redundant description thereof will be omitted.
Fig. 1 is a schematic sectional view showing an optical element according to the present embodiment. The optical element 1 shown in fig. 1 is an electromagnetic wave (hereinafter, simply referred to as "terahertz wave") element (optical element for terahertz wave) usable in the terahertz wave band. The optical element 1 is, for example, a lens, a polarizing plate, a beam splitter, an absorber, various sensors, and the like. The optical element 1 includes: the optical member 2, the antireflection film 3 positioned on the optical member 2, and the adhesive layer 4 positioned between the optical member 2 and the antireflection film 3 in the thickness direction T of the antireflection film 3. The terahertz wave of the present embodiment is, for example, an electromagnetic wave or light having a frequency of 0.1THz or more and 10THz or less.
The optical component 2 is a member that receives the terahertz waves transmitted through the antireflection film 3, and has a main body 11 and a main surface 12 located on the antireflection film 3 side in the thickness direction T. The main body 11 may be a member that transmits terahertz waves, or may be a member that converts terahertz waves into electrical signals. In the case where the optical component 2 is a sensor that detects a received terahertz wave, the main body portion 11 may be provided with, for example, a sensor portion that receives a terahertz wave, an amplification circuit that amplifies an electric signal output from the sensor portion, various wiring lines, and the like. The main body 11 may be provided with terminals for connecting the sensor unit and the like to an external device. The principal surface 12 is an incident surface of the terahertz wave in the optical component 2. When the sensor portion and the like are provided in the main body 11, a part of the main surface 12 may be constituted by the sensor portion, various wirings, and the like, for example.
In the present embodiment, the main body portion 11 is a member through which terahertz waves are transmitted. Specifically, the main body 11 is a single crystal silicon substrate exhibiting excellent permeability to terahertz waves, and the main surface 12 is one surface (silicon surface) of the silicon substrate. At least a portion of the silicon substrate may be doped with impurities. The silicon surface is, for example, a surface in which at least a part of the main surface 12 is made of silicon. Therefore, the silicon surface of the present embodiment may include a metal surface, a compound semiconductor surface, a carbon material surface, a metal oxide surface, a metal nitride surface, and the like, which function as a part of wiring and the like, instead of being formed of only silicon.
The antireflection film 3 is a single-layer film that prevents or suppresses reflection of terahertz waves on the surface of the optical member 2. The antireflection film 3 has: a first surface 3a facing the optical member 2 in the thickness direction T, and a second surface 3b located on the opposite side of the first surface 3 a. In the present embodiment, the second surface 3b corresponds to the outermost surface of the optical element 1. The thickness of the antireflection film 3 is, for example, 4 μm or more and 400 μm or less. In the present embodiment, the refractive index of the antireflection film 3 is equal to or higher than the refractive index of air (equal to or higher than 1) and equal to or lower than the refractive index of silicon (equal to or lower than about 3.4). The antireflection film 3 has: an organic resin 31 in the form of a layer, and inorganic particles 32 contained in the organic resin 31. The ratio of the organic resin 31 and the inorganic particles 32 in the antireflection film 3 is not particularly limited. For example, the organic resin 31 may occupy a larger or smaller volume per unit volume of the antireflection film 3 than the inorganic particles 32.
The organic resin 31 is a resin composed of only a cyclic olefin polymer, or a resin having a cyclic olefin polymer as a main component. In the present embodiment, the organic resin 31 is a resin mainly composed of a cyclic olefin polymer, and may contain a high molecular weight organic compound, a low molecular weight organic compound, and the like other than the cyclic olefin polymer. For example, the organic resin 31 may contain a crosslinking agent, a polymerization initiator, and the like. The organic resin 31 may contain an inorganic substance other than the inorganic particles 32. The "main component of the organic resin 31" in the present embodiment corresponds to the substance contained in the organic resin 31 in the largest amount. For example, it may be: the organic resin 31 accounts for 50 mass% or more, 60 mass% or more, or 70 mass% or more of the organic resin 31 and corresponds to the main component of the organic resin 31.
The cyclic olefin polymer is a polymer having a cyclic olefin moiety in the main chain, and is a substance that is transparent to terahertz waves. In the present embodiment, a substance that is permeable to terahertz waves corresponds to a substance having a lower absorption performance of terahertz waves than epoxy polymers (for example, 3, 4-epoxycyclohexylmethyl-3, 4-epoxycyclohexane carboxylate). Alternatively, the substance that is permeable to terahertz waves may have a terahertz wave absorption capacity of 10% or less of that of 3, 4-epoxycyclohexylmethyl-3, 4-epoxycyclohexanecarboxylate.
Examples of the cyclic olefin polymer include: ring-opening polymers of cycloolefin monomers, addition polymers of cycloolefin monomers, copolymers of cycloolefin monomers and alkenes, and the like. Examples of the cyclic olefin polymer include various polystyrenes. The cycloolefin monomer is a compound having a ring structure formed of carbon atoms and having a carbon-carbon double bond in the ring structure. Examples of the cycloolefin monomer include: bicyclic compounds such as 2-norbornene and norbornadiene; tricyclics such as dicyclopentadiene and dihydrodicyclopentadiene; tetracyclic compounds such as tetracyclododecene, ethylenetetracyclododecene and phenyltetracyclododecene; pentacyclic compounds such as tricyclopentadiene; norbornene monomers, which are monomers containing a norbornene ring, such as heptacycl bodies such as tetracyclopentadiene. The cycloolefin monomer may be a monocyclic cycloolefin such as cyclobutene, cyclopentene, cyclooctene, cyclododecene, 1, 5-cyclooctadiene, or the like. The cycloolefin monomer may have a substituent within a range that does not inhibit the action and effect of the organic resin 31. The substituent includes, for example, oxygen, nitrogen, and the like.
The cyclic olefin polymer may be, for example, ZEONEX (registered trademark) series or ZEONOR (registered trademark) series manufactured by ZEON corporation, japan, Sumitomo Bakelite co., Ltd, SUMILITE (registered trademark) series manufactured by JSR corporation, ateon (registered trademark) series, APEL (registered trademark) series manufactured by mitsui chemical corporation, TOPAS (registered trademark) series manufactured by Ticona corporation, or OPTOREZ series manufactured by hitachi chemical corporation.
The inorganic particles 32 are used to adjust the refractive index of the antireflection film 3, and are dispersed in the organic resin 31. The inorganic particles 32 contain, for example, a substance that is transparent to terahertz waves and has a higher refractive index than the organic resin 31. The inorganic particles 32 may be, for example, silicon particles, titanium oxide particles, diamond particles, or the like. The silicon particles may also be high resistance silicon particles. The high-resistance silicon particles are, for example, those having a size of 1X 103Silicon particles having a resistance value of not less than Ω · cm. The average particle diameter of the inorganic particles 32 is, for example, 5nm or more and 3000nm or less. The upper limit of the average particle diameter of the inorganic particles 32 may be 200nm, or may beIs 20 nm. The lower limit of the average particle diameter of the inorganic particles 32 may be 200nm or 20 nm. The average particle diameter of the inorganic particles 32 is measured by, for example, a laser diffraction scattering method, a dynamic light scattering method, a photon correlation spectroscopy method, or the like.
The refractive index of the antireflection film 3 can be arbitrarily set by adjusting the concentration of the inorganic particles 32 dispersed in the organic resin 31. The inorganic particles 32 may be uniformly dispersed or may be non-uniformly dispersed in the antireflection film 3. In the present embodiment, the inorganic particles 32 are unevenly dispersed in the antireflection film 3. Specifically, the volume ratio of the inorganic particles 32 per unit volume of the antireflection film 3 is higher as approaching the optical member 2 in the thickness direction T. Therefore, the closer to the optical member 2 in the thickness direction T, the greater the content of the inorganic particles 32 per unit volume of the antireflection film 3. The volume ratio of the inorganic particles 32 per unit volume of the antireflection film 3 is, for example, greater than 0%, 50% or less, 60% or less, or 70% or less. The refractive index of the antireflection film 3 is larger as it approaches the optical member 2 in the thickness direction T. In the present embodiment, the refractive index of the antireflection film 3 is closer to the refractive index of silicon as it is closer to the optical member 2 in the thickness direction T. The refractive index of the antireflection film 3 may be continuously changed in the thickness direction T or may be changed stepwise. From the viewpoint of preventing the reflection of the terahertz wave inside the antireflection film 3, the refractive index of the antireflection film 3 may also continuously change in the thickness direction T. For example, by leaving the organic resin 31 in which the inorganic particles 32 are dispersed, without curing, it is possible to realize a non-uniform distribution state (non-uniform dispersion state) of the inorganic particles 32 in the antireflection film 3.
The refractive index of the antireflection film 3 is derived by, for example, effective medium approximation. For example, the dielectric constant of a predetermined portion of the antireflection film 3 is ∈layerLet the dielectric constant of the inorganic particles 32 be εaThe dielectric constant of the organic resin 31 is epsilonbThe volume ratio (volume percentage) of the inorganic particles 32 in the volume of the predetermined portion is fa. In this case, [ mathematical formula 1] below]The relationship shown holds. In addition, the refractive index is n and the dielectric constant isIn the case of ε, n2The relationship holds true for epsilon. Therefore, ε is derived by using the following formulalayerThe refractive index of a predetermined portion of the antireflection film 3 can be calculated. The effective medium approximation is a method of obtaining the optical constants of an effective homogeneous film by analyzing the film by replacing the roughness of the film surface and the interface, or the inhomogeneity and discontinuity of the film with the effective homogeneous film.
[ mathematical formula 1]
Figure BDA0002212419840000081
The adhesive layer 4 is a layer for bonding the main surface 12 of the optical member 2 and the antireflection film 3. The adhesive layer 4 exhibits adhesion to both the cyclic olefin polymer and silicon. The thickness of the adhesive layer 4 is, for example, 1nm or more and 100 μm or less. The thickness of the adhesive layer 4 may be 5nm or more or 10nm or more. The thickness of the adhesive layer 4 may be 30 μm or less, 10 μm or less, 1000nm or less, 500nm or less, or 100nm or less. The thickness of the adhesive layer 4 is 1nm or more, whereby the antireflection film 3 can be favorably fixed to the main surface 12. When the thickness of the adhesive layer 4 is 100 μm or less, the terahertz wave can be favorably suppressed from being absorbed by the adhesive layer 4. The adhesive layer 4 contains an olefin polymer thermally modified by the main surface 12 of the optical member 2.
The olefin polymer is a polymer obtained by polymerizing a monomer containing an olefin as a main component, and for example, a polymer obtained by polymerizing a monomer containing a monomer portion derived from an olefin in an amount of 50 mass% or more, 60 mass% or more, 70 mass% or more, 80 mass% or more, 90 mass% or more, or 95 mass% or more corresponds to an olefin polymer, and examples of the olefin polymer include polyethylene, polypropylene, polybutene, polymethylpentene and the like, and therefore, a polyethylene film, a polypropylene film and the like can be used as the adhesive layer 4, and the olefin polymer can be a copolymer, and for example, a copolymer of α -olefin such as a propylene-ethylene copolymer, a propylene-butene copolymer and the like, a styrene-butadiene-styrene block copolymer, a styrene-hexadiene-styrene copolymer, a styrene-pentadiene-styrene copolymer, or an ethylene-propylene-diene copolymer (RPDM) can be used as the olefin polymer, and in this case, the olefin polymer can be a cycloolefin polymer selected from among organic resins 31, and a heat-modified olefin polymer, and an antireflection film comprising a cycloolefin polymer in which the adhesive layer is not modified from 3.
The olefin-based polymer after thermal modification is an olefin-based polymer modified by heating, and exhibits better adhesion to silicon than the olefin-based polymer before modification by heating. This is presumably because the functional group (e.g., a hydrophilic group such as a hydroxyl group) on the silicon surface and the olefin-based polymer after thermal modification are bonded to each other. Namely, it is assumed that: this bonding enhances the adhesion of the silicon to the thermally modified olefin-based polymer. The olefin-based polymer after thermal modification may have at least one of a chemical structure, a number average molecular weight, and a weight average molecular weight different from that of the olefin-based polymer before modification by heating.
The heating temperature for thermally modifying the olefin-based polymer is, for example, 160 ℃ or more, 180 ℃ or more, 200 ℃ or more, or 240 ℃ or more. The heating temperature is, for example, 500 ℃ or lower, 400 ℃ or lower, 360 ℃ or lower, 320 ℃ or lower, or 280 ℃ or lower. When the heating temperature is too low, the above-mentioned bond may not be sufficiently formed. On the other hand, when the heating temperature is too high, the olefin-based polymer is likely to be thermally decomposed. From the viewpoint of reliably preventing these problems, the heating temperature may be, for example, 200 ℃ to 360 ℃, or 240 ℃ to 320 ℃. The heating is performed in an oxygen-containing atmosphere such as an air atmosphere. The heating is performed using a heating source such as an oven, a hot plate, infrared rays, flame, laser, or flash lamp. The period of heating required for thermally modifying the olefin-based polymer is not particularly limited, and is, for example, 1 minute to 10 minutes. This period may be 2 minutes.
The degree of thermal modification of the olefin polymer contained in the adhesive layer 4 can be adjusted by the heating temperature, the oxygen concentration during heating, and the like. For example, in order to increase the degree of thermal modification of the olefin-based polymer, the heating temperature of the adhesive layer 4 is increased, and/or the oxygen concentration during heating is increased. Conversely, in order to reduce the degree of thermal modification of the olefin-based polymer, the heating temperature of the adhesive layer 4 is lowered, and/or the oxygen concentration during heating is lowered.
The degree of thermal modification of the olefin-based polymer contained in the adhesive layer 4 can be evaluated, for example, by using the oxygen content of the thermally modified olefin-based polymer constituting the adhesive layer 4. As a specific example, the degree of thermal modification of the olefin-based polymer contained in the adhesive layer 4 can be evaluated by calculating the ratio of the number of oxygen atoms contained in the adhesive layer 4 to the total of the number of oxygen atoms and the number of carbon atoms contained in the adhesive layer 4 (the number of oxygen atoms/(the number of oxygen atoms + the number of carbon atoms) × 100 (%)). From this evaluation, it can be considered that: the larger the above ratio is, the larger the degree of thermal modification of the olefin-based polymer becomes. For example, when the above ratio is 0.3% or more, 0.5% or more, 1.0% or more, 2.0% or more, or 5.0% or more, and is 50% or less, 30% or less, 20% or less, 10% or less, or 8% or less, it is particularly suitable as an index indicating the degree of thermal modification of the olefin-based polymer. Here, as a method of evaluating the content of the oxygen atom and the carbon atom in the adhesive layer 4, for example, X-ray photoelectron spectroscopy (XPS) is exemplified. As the XPS device, for example, "K-Alpha (seimer fisher technologies)", can be used.
The degree of thermal modification of the olefin-based polymer contained in the adhesive layer 4 can be evaluated by, for example, the infrared absorption spectrum of the thermally modified olefin-based polymer constituting the adhesive layer 4. As a specific example, the degree of thermal modification of the olefin-based polymer contained in the adhesive layer 4 can be evaluated by calculating the ratio of the integrated value of the absorption peak of C ═ O stretching vibration in the adhesive layer 4 to the integrated value of the absorption peak of C-H stretching vibration in the adhesive layer 4 (integrated value of the absorption peak of C ═ O stretching vibration/integrated value of the absorption peak of C-H stretching vibration (dimensionless number)). From this evaluation, it can be considered that: the larger the above ratio is, the larger the degree of thermal modification of the olefin-based polymer becomes. For example, when the above ratio is 0.01 or more, 0.02 or more, 0.05 or more, 0.1 or more, 0.15 or more, or 0.20 or more, and 20 or less, 10 or less, or 5 or less, it is particularly suitable as an index indicating the degree of thermal modification of the olefin-based polymer. The infrared absorption spectrum of the adhesive layer 4 can be measured, for example, by using "Nicolet 6700 (seimer feishell scientific corporation)" which is a fourier transform infrared spectrometer.
Next, an example of a method for manufacturing the optical element 1 according to the present embodiment will be described with reference to fig. 2. Fig. 2 is a flowchart for explaining the method of manufacturing the optical element according to the present embodiment.
First, the optical component 2 having the main surface 12 is prepared (step S1). In step S1, for example, the optical component 2 made of a processed or unprocessed silicon substrate is prepared. The main surface 12 may be subjected to surface treatment such as ozone treatment or ultraviolet treatment in order to add a hydrophilic group such as a hydroxyl group to the main surface 12.
Next, the adhesive layer 4 containing the thermally modified olefin polymer is formed on the main surface 12 of the optical member 2 (step S2). In step S2, for example, first, the adhesive layer 4 containing the olefin polymer is formed on the main surface 12. Next, the olefin polymer contained in the adhesive layer 4 is thermally modified by heating, thereby forming the adhesive layer 4. For example, the olefin polymer is thermally modified by holding the optical member 2 provided with the adhesive layer 4 on a hot plate heated to a predetermined temperature. This forms the adhesive layer 4 in good close contact with the main surface 12.
The adhesive layer 4 containing the olefin polymer before thermal modification is formed by, for example, various coating methods. In the case of performing the coating method, first, a solution in which an olefin polymer is dissolved in a solvent (for example, toluene, chloroform, or the like) is prepared. Next, the solution is coated on the main surface 12. Next, the coated solution was dried. In this drying, conditions such as temperature, heating time, pressure, and atmosphere for removing the solvent are appropriately set. For example, the solution is dried by holding the optical member 2 on a hot plate heated to a predetermined temperature under an air atmosphere and normal pressure. Specifically, the optical member 2 is held on a hot plate heated to 140 ℃ or lower for a predetermined period of time. The predetermined period is not particularly limited, and is, for example, at most 10 minutes. Examples of the coating method include: spin coating, roll coating, spray coating, die coating, spread coating, dip coating, brush coating, blade coating, roll coating, curtain coating, and the like.
The adhesive layer 4 containing the olefin polymer before thermal modification may be formed by a thermal compression bonding method (for example, a thermal compression method, a fusion bonding method, a powder coating method, or the like). In the case of performing the thermocompression bonding method, for example, an object such as a bulk solid, a powder, or a thin film is placed on the main surface 12 of the optical member 2, and then the object is heated and pressurized. This melts or welds the object on the main surface 12.
Next, the antireflection film 3 is formed on the adhesive layer 4, and the antireflection film 3 is bonded to the main surface 12 of the optical member 2 via the adhesive layer 4 (step S3). In step S3, the antireflection film 3 is formed on the adhesive layer 4 by, for example, the above coating method, the above thermocompression bonding method, or the like. For example, when the above coating method is used, first, a solution containing the inorganic particles 32 and the organic resin 31 is applied to the adhesive layer 4. Then, the solution is dried using a heat source such as a hot plate. Thereby, the antireflection film 3 containing the organic resin 31 in which the inorganic particles 32 are dispersed is formed. For example, when the thermal compression bonding method is employed, the antireflection film 3 formed in advance is stuck to the adhesive layer 4.
According to the optical element 1 for terahertz waves formed by the above-described manufacturing method of the present embodiment, the antireflection film 3 has the organic resin 31 containing the cyclic olefin polymer as a main component, and the cyclic olefin polymer exhibits better transmittance for terahertz waves than the epoxy polymer. The antireflection film 3 exhibits better transmittance for terahertz waves than the case of using an organic resin containing an epoxy polymer as a main component. On the other hand, cyclic olefin polymers tend to have lower adhesion to silicon than epoxy polymers. Therefore, when the antireflection film 3 having the organic resin 31 mainly composed of the cyclic olefin polymer is formed only on the silicon surface, there is a possibility that the antireflection film 3 is not formed satisfactorily. In contrast, according to the optical element 1 of the present embodiment, the antireflection film 3 and the main surface 12, which is the silicon surface of the optical member 2, are bonded to each other through the adhesive layer 4 containing the thermally modified olefin polymer. The olefin polymer after thermal modification can maintain the permeability to terahertz waves and can improve the adhesion to silicon. By using the adhesive layer 4 containing the olefin polymer after thermal modification, the anti-reflection film 3 can be favorably fixed to the silicon surface while suppressing absorption of terahertz waves by the adhesive layer 4. Therefore, according to the present embodiment, the optical element 1 having the antireflection film 3 exhibiting good transmittance for terahertz waves can be manufactured with high reliability.
In the present embodiment, the volume ratio of the inorganic particles 32 per unit volume of the antireflection film 3 is higher as approaching the optical member 2 in the thickness direction T. Therefore, the refractive index of the antireflection film 3 can be set higher as the optical member 2 is closer in the thickness direction T, and thus reflection of the terahertz wave on the main surface 12 can be suppressed well.
In the present embodiment, the thickness of the adhesive layer 4 is 1nm or more and 100 μm or less. Therefore, the antireflection film 3 can be favorably fixed to the main surface 12 via the adhesive layer 4, and the absorption of terahertz waves by the adhesive layer 4 can be favorably suppressed.
In the present embodiment, the inorganic particles 32 may be silicon particles, titanium oxide particles, or diamond particles. In this case, the refractive index of the antireflection film 3 can be adjusted by the inorganic particles 32 while suppressing absorption of terahertz waves by the antireflection film 3.
Next, various modifications of the present embodiment will be described with reference to fig. 3 to 7. In the description of each modification, redundant description with the present embodiment is omitted, and only the portion different from the present embodiment is described. That is, the description of the present embodiment can be appropriately used in various modifications as long as the technical feasibility is achieved.
(first modification)
Fig. 3 is a schematic cross-sectional view showing an optical element according to a first modification. The optical element 1A shown in fig. 3 includes, in addition to the optical member 2, the antireflection film 3, and the adhesive layer 4, a bubble-containing layer 5, and the bubble-containing layer 5 is located on the second surface 3B of the antireflection film 3 and contains a plurality of bubbles B. Similarly to the antireflection film 3, the cell-containing layer 5 is also a layered organic resin containing a cyclic olefin polymer as a main component, and has voids due to the cells B. The void ratio of the bubble-containing layer 5 is, for example, more than 0% and less than 100%. A part of the bubbles B in the bubble-containing layer 5 may be integrated. The refractive index of the bubble-containing layer 5 is equal to or higher than the refractive index of air (equal to or higher than 1) and equal to or lower than the refractive index of the antireflection film 3. The bubbles B are bubbles of air dispersed in the bubble-containing layer 5. The average diameter of the bubbles B is set to, for example, 100nm or more and 3000nm or less, and therefore the bubbles B of the first modification can be referred to as so-called "nanobubbles". The bubbles B are formed by blowing gas into the organic resin, for example. The bubbles B may be uniformly dispersed or may be non-uniformly dispersed in the bubble-containing layer 5. The bubble-containing layer 5 may contain particles corresponding to the inorganic particles 32. When the bubble-containing layer 5 contains the particles, the ratio of the volume of the inorganic particles per unit volume of the bubble-containing layer 5 is lower than the ratio of the volume of the inorganic particles 32 per unit volume of the antireflection film 3.
In the first modification described above, the same operational effects as those of the present embodiment can be achieved. In addition, since the air bubbles B are bubbles of air, the air bubbles B can be regarded as nanoparticles exhibiting the same refractive index as air. Therefore, the refractive index of the bubble-containing layer 5 can be easily made lower than the refractive index of the second surface 3b of the antireflection film 3. Therefore, in the first modification, by providing the optical element 1A with the bubble-containing layer 5, reflection of the terahertz wave on the second surface 3b of the antireflection film 3 can be suppressed satisfactorily.
In the first modification, the bubbles B may be unevenly dispersed in the bubble-containing layer 5. Specifically, the proportion of the volume of the bubbles B per unit volume of the bubble-containing layer 5 is lower as it approaches the second surface 3B in the thickness direction T. Therefore, the refractive index of the bubble-containing layer 5 becomes smaller as it is farther from the second surface 3b in the thickness direction T. This makes it possible to bring the refractive index of the surface of the bubble-containing layer 5 close to the effective refractive index of air, and to favorably suppress reflection of terahertz waves on the surface of the bubble-containing layer 5. The refractive index of the bubble-containing layer 5 may be continuously changed in the thickness direction T or may be changed stepwise. From the viewpoint of preventing reflection of the terahertz wave inside the bubble-containing layer 5, the refractive index of the bubble-containing layer 5 may also continuously change in the thickness direction T. When the refractive index of the bubble-containing layer 5 changes stepwise, the bubble-containing layer 5 may have a plurality of layers stacked on each other in the thickness direction T. In this case, the proportion of the volume of the bubbles B per unit volume of the layer among the layers is lower as the layer approaches the antireflection film 3 in the thickness direction T.
(second modification)
Fig. 4A is a schematic cross-sectional view showing an optical element according to a second modification, and fig. 4B is a view showing an example of a surface of the optical element according to the second modification. The second surface 3B of the antireflection film 3A of the optical element 1B shown in fig. 4A and 4B has a concave-convex shape. In the second modification, when the second surface 3b is rougher than the first surface 3a, the second surface 3b may be regarded as having a concave-convex shape. Alternatively, when the second surface 3b is subjected to a step for providing unevenness (for example, nanoimprinting, etching, or the like), the second surface 3b may be regarded as having unevenness. Specifically, the antireflection film 3A is provided with a plurality of convex portions 33 that are continuous along the surface direction of the second surface 3 b. Each convex portion 33 has a substantially quadrangular pyramid shape. The cross section of each convex portion 33 including the apex is triangular. Each convex portion 33 is formed by, for example, nanoimprinting or the like.
In the second modification described above, the same operational effects as those of the present embodiment can be achieved. In addition, since the second surface 3b of the antireflection film 3A has a so-called "moth-eye structure", reflection of terahertz waves by the second surface 3b can be suppressed satisfactorily.
(third modification)
Fig. 5 is a schematic cross-sectional view showing an optical element according to a third modification. The antireflection film 3B of the optical element 1C shown in FIG. 5 has layers 51 to 55 laminated on each other in the thickness direction T. In the third modification, the layer 51 is closest to the optical component 2 in the thickness direction T, and the layer 55 is farthest from the optical component 2 in the thickness direction T. The layers 51 to 55 each have: an organic resin containing a cyclic olefin polymer as a main component, and inorganic particles 32 dispersed in the organic resin. That is, the layers 51 to 55 contain the organic resin 31 and the inorganic particles 32 in a layer shape, respectively.
In each of the layers 51 to 55, the volume ratio of the inorganic particles 32 per unit volume of the layer is higher as the layer is closer to the optical member 2 in the thickness direction T. Therefore, the content of the inorganic particles 32 in the layer 51 is the largest, and the content of the inorganic particles 32 in the layer 55 is the smallest. In other words, the refractive index is higher as the layer closer to the optical member 2 in the thickness direction T is. The smaller the difference in refractive index between adjacent layers, the better. As the difference in refractive index between adjacent layers is smaller, reflection of the terahertz wave at the interface between adjacent layers can be suppressed, and the terahertz wave can be transmitted through the inside of the antireflection film 3B more favorably. The thicknesses of the layers 51-55 may be the same or different. Alternatively, some of the layers 51-55 may have a different thickness from other layers. The antireflection film 3B is formed, for example, as follows: that is, after the layers 51 to 55 in which the content of the inorganic particles 32 is adjusted are formed, the layers 51 to 55 are sequentially stacked. Alternatively, the antireflection film 3B may be formed by sequentially applying the resins constituting the layers 51 to 55 on the adhesive layer 4.
In the third modification described above, the same operational effects as those of the present embodiment can be achieved. In addition, the volume ratio of the inorganic particles 32 can be set for each layer 51 to 55. Therefore, the refractive index of the antireflection film 3C in the thickness direction T can be easily and reliably changed stepwise.
(fourth modification)
Fig. 6 is a schematic cross-sectional view showing an optical element according to a fourth modification. The optical element 1D shown in fig. 6 is an example in which the bubble-containing layer 5 shown in the first modification is added to the optical element 1C shown in the third modification. In this fourth modification, the operational effects of the first modification and the third modification can be achieved in combination.
(fifth modification)
Fig. 7 is a schematic cross-sectional view showing an optical element according to a fifth modification. The second surface 3b of the antireflection film 3C of the optical element 1E shown in fig. 7 has a concave-convex shape as in the second modification. Therefore, the layer 55A included in the antireflection film 3C and farthest from the optical member 2 in the thickness direction T has a plurality of convex portions 56 continuing in the plane direction of the second surface 3 b. Each of the projections 56 has a substantially quadrangular pyramid shape. The cross section of each projection 56 including the apex is triangular. Each convex portion 56 is formed by, for example, nanoimprinting or the like.
In the fifth modification described above, the same operational effects as those of the third modification can be achieved. Further, since the second surface 3b of the antireflection film 3C has a so-called "moth-eye structure", the same operational effects as those of the second modification can be simultaneously achieved.
One aspect of the present invention is described in detail above based on the above embodiment and the above modified examples. However, the present invention is not limited to the above embodiment and the above modified examples. The aspect of the invention may be modified within a range not departing from the gist thereof. In addition, the above embodiment and the above modification can be appropriately combined. For example, the first and second modified examples may be combined to form the surface of the bubble-containing layer into a concavo-convex shape. In this case, the reflection of the terahertz wave on the surface of the bubble-containing layer can be suppressed well.
For example, in the above embodiment and the first and second modifications, the inorganic particles are unevenly dispersed in the antireflection film, but the present invention is not limited to this. The inorganic particles may also be uniformly dispersed within the anti-reflective film. In this case, the antireflection film functions as a single-layer antireflection coating film. Here, the refractive index of the antireflection film is set to nflatThe thickness of the antireflection film is d, and the wavelength indicating the maximum transmittance is λ. In this case, the following [ equation 2]]The relationship shown holds. Furthermore, [ mathematical formula 2]]M in (1) is an integer. The optical component is a silicon substrate, and the refractive index is nsiIt is assumed that the anti-reflection film does not absorb the terahertz wave of the above wavelength. Under the assumption that [ equation 3] below is satisfied]In the case of (2), the antireflection film can exhibit a transmittance of 100% for terahertz waves of the above wavelength. Therefore, when the inorganic particles are uniformly dispersed in the antireflection film, the following [ equation 3] may be satisfied]The content of the inorganic particles is adjusted.
[ mathematical formula 2]
Figure BDA0002212419840000161
[ mathematical formula 3]
Figure BDA0002212419840000162
In the above embodiment and the above modification, the adhesive layer has a single-layer structure, but is not limited thereto. The adhesive layer may have a multilayer structure. For example, the adhesive layer has: a first layer containing a thermally modified olefin polymer, and a second layer formed on the first layer. The second layer is a layer exhibiting good adhesion to the first layer and the antireflection film, and contains a thermally modified olefin polymer. Thus, the second layer has less adhesion to silicon than the first layer. On the other hand, the second layer has greater adhesiveness to the antireflection film than the first layer. Since the second layer exhibits the above-mentioned adhesiveness, the degree of thermal modification of the olefin-based polymer contained in the second layer is smaller than that of the olefin-based polymer contained in the first layer. The degree of thermal modification is adjusted by heating temperature, time, ambient atmosphere, and the like. For example, the first layer is heated to a temperature of 240 ℃ or higher and 320 ℃ or lower, and the second layer is heated to a temperature of 160 ℃ or higher and less than 240 ℃ or higher and 500 ℃ or lower. The adhesive layer may have a third layer in addition to the first layer and the second layer. In this case, the adhesion to silicon is the first layer to be the largest. On the other hand, the adhesion to the antireflection film is the largest of the third layer. For example, the first layer is heated to a temperature of 280 ℃ to 320 ℃, the second layer is heated to a temperature of 220 ℃ to less than 280 ℃, and the third layer is heated to a temperature of 160 ℃ to less than 220 ℃, or more than 320 ℃ to less than 500 ℃. In the case where the adhesive layer includes the first layer and the second layer, the antireflection film may be in contact with both the first layer and the second layer. In the case where the adhesive layer includes the first layer, the second layer, and the third layer, the antireflection film may be in contact with all of the first layer, the second layer, and the third layer, or may be in contact with the second layer and the third layer.
When the adhesive layer has a multilayer structure, the degree of thermal modification of the olefin-based polymer contained in each adhesive layer can be evaluated by the above-described oxygen content ratio, infrared absorption spectrum, and the like. For example, in the case of evaluation based on the oxygen content, the difference between the degree of thermal modification of the olefin-based polymer contained in the first layer and the degree of thermal modification of the olefin-based polymer contained in the second layer is represented by the difference between the ratio of the number of oxygen atoms in the first layer to the total of the number of oxygen atoms and the number of carbon atoms contained in the first layer and the ratio of the number of oxygen atoms in the second layer to the total of the number of oxygen atoms and the number of carbon atoms contained in the second layer. The difference is, for example, 0.1% or more, 0.2% or more, 0.3% or more, 0.4% or more, 0.5% or more, 0.8% or more, 1.0% or more, 2.0% or more, or 3.0% or more. The difference is, for example, 10.0% or less, 7.0% or less, 5.0% or less, 3.0% or less, 2.0% or less, 1.0% or less, 0.5% or less, 0.3% or less, or 0.1% or less. The difference may be 0.1% or more and 10.0% or less.
Alternatively, in the case of evaluation based on infrared absorption spectroscopy, the difference between the degree of thermal reforming of the olefin-based polymer contained in the first layer and the degree of thermal reforming of the olefin-based polymer contained in the second layer is represented by the difference between the ratio of the integrated value of the absorption peak of the C ═ O stretching vibration of the first layer to the integrated value of the absorption peak of the C-H stretching vibration and the ratio of the integrated value of the absorption peak of the C ═ O stretching vibration of the second layer to the integrated value of the absorption peak of the C-H stretching vibration. The difference is, for example, 0.1 or more, 0.2 or more, 0.3 or more, 0.4 or more, 0.5 or more, 0.8 or more, 1.0 or more, 2.0 or more, or 3.0 or more. The difference may be, for example, 10.0 or less, 7.0 or less, 5.0 or less, 3.0 or less, 2.0 or less, 1.0 or less, 0.5 or less, 0.3 or less, or 0.1 or less. The difference may be 0.1 to 20.0.
In the second modification and the fourth modification, each of the convex portions has a substantially quadrangular pyramid shape, but the present invention is not limited thereto. For example, each convex portion may have a polygonal pyramid shape or a conical shape. Further, each convex portion may be formed in a hemispherical shape or a polygonal prism shape. Therefore, each convex portion may have a polygonal cross section, an elliptical cross section, or a semicircular cross section. The plurality of projections are continuous along the surface direction of the second surface, but not limited thereto. Adjacent projections may be spaced apart from each other. That is, the second surface may have both a region provided with the convex portion and a flat region not provided with the convex portion. Each projection may also have a top surface. That is, each convex portion may have a truncated cone shape or a truncated pyramid shape.
In the third to fifth modifications, the antireflection film has five layers, but is not limited thereto. The antireflection film may have two or more layers. Likewise, there is no limitation on the number of layers included in the bubble-containing layer.
In the above embodiment and the above modification, the silicon substrate is not limited to a silicon wafer, and may be an SOI substrate or the like. When an SOI substrate or the like is used, the following may be used: the main body is a silicon substrate, and the main surface is a surface of a silicon layer provided on the silicon substrate with an insulating layer interposed therebetween. That is, the main surface of the optical member may be a surface of a component different from the component of the main body.
In the above embodiment and the above modification, the main body of the optical component is a single crystal silicon substrate, and the surface of the optical component is a silicon surface, but the present invention is not limited thereto. For example, the body may be germanium, diamond, zinc telluride (ZnTe), or lithium niobate (LiNbO)3) DAST (4- (4-dimethylaminostyryl) methylpyridine p-toluenesulfonate (4-dimethyllamino-N-methyl-4-stilbazolium tosylate), and the like. In this case, the surface of the optical member may be not a silicon surface but a germanium surface, a diamond surface, or the like. That is, the surface of the optical member is not limited to the silicon surface, and may be a surface made of another inorganic substance, a surface made of an organic substance, or a mixed surface of an inorganic substance and an organic substance. Even in this case, the same operational effects as those of the above embodiment and the above modification can be achieved by using the adhesive layer containing the olefin-based polymer after thermal modification.
In the above embodiment and the above modification, the antireflection film is directly bonded to the adhesive layer containing the thermally modified olefin polymer, but the invention is not limited thereto. For example, it may be: an organic layer containing a polymer that has not been thermally modified is provided between an adhesive layer containing an olefin polymer that has been thermally modified and an antireflection film, and the antireflection film is bonded to the adhesive layer via the organic layer. The organic layer may be a part of an antireflection film, for example. The non-thermally modified polymer is, for example, an olefin-based polymer.
Examples
The present invention will be described in further detail with reference to the following examples, but the present invention is not limited to these examples.
(example 1)
First, a solution was obtained by mixing and stirring 7 mass% of a cycloolefin polymer (manufactured by JSR corporation, ARTON (registered trademark)) and 93 mass% of chloroform at room temperature. Next, the above solution was spin-coated on a silicon substrate. In this spin coating, the silicon substrate on which the solution was dropped was rotated at a rotation speed of 2000rpm for 20 seconds. Next, the silicon substrate coated with the above solution was held on a heating plate heated to 120 ℃. Thereby, the solution was dried, and an adhesive layer (first adhesive layer) containing an olefin polymer was formed on the surface of the silicon substrate. Next, the substrate on which the adhesive layer was formed was held on a hot plate heated to 280 ℃ for 1 minute. Thereby, a silicon substrate provided with the thermally modified adhesive layer was obtained. The thickness of the adhesive layer was 23 nm.
Next, the solution was spin-coated on the thermally modified adhesive layer. In this spin coating, the silicon substrate on which the solution was dropped was rotated at a rotation speed of 2000rpm for 20 seconds. Next, the silicon substrate coated with the above solution on the adhesive layer was held on a hot plate heated to 140 ℃ for 10 minutes. Thereby, the solution was dried, and an organic resin layer containing an olefin polymer was formed on the adhesive layer. The thickness of the organic resin layer was 23 nm.
(example 2)
Unlike example 1, the adhesive layer had a two-layer structure. Specifically, after the first adhesive layer is formed, the solution is spin-coated. In this spin coating, the silicon substrate on which the solution was dropped was rotated at a rotation speed of 2000rpm for 20 seconds. Next, the silicon substrate coated with the above solution on the first adhesive layer was held on a hot plate heated to 120 ℃. The solution is dried, and a second adhesive layer containing an olefin polymer is formed on the first adhesive layer. Next, the substrate on which the second adhesive layer was formed was held on a heating plate heated to 200 ℃ for 1 minute. Thereby, a silicon substrate provided with the thermally modified first and second adhesive layers was obtained. The thickness of the second adhesive layer was 23 nm. In example 2, the organic resin layer was formed on the second adhesive layer.
(example 3)
Unlike examples 1 and 2, the adhesive layer had a three-layer structure. Specifically, first, the first adhesive layer and the second adhesive layer are formed. In example 3, the first and second adhesive layers were formed at different temperatures from those in example 2. Specifically, in example 3, the temperature at which the first adhesive layer was thermally modified was set to 300 ℃ and the temperature at which the second adhesive layer was thermally modified was set to 280 ℃. Next, the above solution was spin coated. In this spin coating, the silicon substrate on which the solution was dropped was rotated at a rotation speed of 2000rpm for 20 seconds. Next, the silicon substrate coated with the above solution on the second adhesive layer was held on a hot plate heated to 120 ℃. Thereby, the solution is dried, and a third adhesive layer containing an olefin polymer is formed on the second adhesive layer. Next, the substrate on which the third adhesive layer was formed was held on a heating plate heated to 200 ℃ for 1 minute. Thereby, a silicon substrate provided with the thermally modified first to third adhesive layers was obtained. The thickness of the third adhesive layer was 23 nm. In example 3, the organic resin layer was formed on the third adhesive layer.
(example 4)
Unlike examples 1 to 3, a film formed in advance was used as an adhesive layer. Specifically, first, a polyethylene film having a thickness of 30 μm was disposed on a silicon substrate. Next, the silicon substrate was heated at 120 ℃ for 1 minute. Thus, a silicon substrate provided with a first adhesive layer containing an olefin polymer was obtained. Next, the silicon substrate was held on a heating plate heated to 280 ℃ for 1 minute. Thereby, a silicon substrate provided with the thermally modified first adhesive layer was obtained. Next, a polyethylene film having a thickness of 30 μm was disposed on the thermally modified first adhesive layer. Next, the silicon substrate was heated at 120 ℃ for 1 minute. Thereby, a second adhesive layer containing the olefin polymer is formed on the thermally modified first adhesive layer. Next, the silicon substrate was held on a heating plate heated to 200 ℃ for 2 minutes. Thereby, a silicon substrate provided with the thermally modified first and second adhesive layers was obtained.
Next, a polyethylene film having a thickness of 30 μm was disposed on the thermally modified second adhesive layer. Next, the silicon substrate was heated at 120 ℃ for 1 minute. Then, the silicon substrate was heated at 140 ℃ for 10 minutes. Thereby, an organic resin layer containing an olefin polymer is formed on the second adhesive layer.
Comparative example 1
Unlike examples 1 to 3, the organic resin layer containing the olefin polymer was formed on the silicon substrate using the above solution without forming the first adhesive layer and the second adhesive layer. The organic resin layer is in direct contact with the surface of the silicon substrate.
Comparative example 2
Unlike example 4, the polyethylene film was disposed on the silicon substrate without forming the first adhesive layer and the second adhesive layer. Then, the silicon substrate was heated at 120 ℃ for 1 minute, and thereafter, at 140 ℃ for 10 minutes. Thus, an organic resin layer containing an olefin polymer was formed in direct contact with a silicon substrate, as in comparative example 1.
(Cross-cut test)
The organic layer (each adhesive layer and organic resin layer) formed on the silicon substrate was provided with cuts reaching the silicon substrate at 1mm intervals using a cutter. After 6 slits were formed, 6 slits orthogonal to the slits were formed in the organic layer. Thus, lattice-shaped slits are provided in the organic layer. Next, Scotch (registered trademark) · repair tape 810 (manufactured by 3M corporation, 24mm wide, 50M long) was attached to the surface of the organic layer, and the tape was rubbed with a finger on the organic layer. The tape was then peeled off. The thus-applied and peeled areas of the tape were observed with a microscope.
The evaluation results of the cross-cut test were classified as follows.
A: the edges of the cuts were completely smooth and no flaking of the grid was observed.
B: peeling occurred in a part of the organic layer, but the affected part of the cross cut portion was less than 35%.
C: peeling occurred on the entire surface of the organic layer, and the affected part of the cross cut portion was 35% or more.
The evaluation results of the cross-cut test in examples 1 and 4 were B, and the evaluation results in examples 2 and 3 were a. On the other hand, comparative examples 1 and 2 showed C as the evaluation result. From these results, it is understood that the bonding between the silicon substrate and the organic resin layer containing the olefin polymer becomes strong by providing the thermally modified adhesive layer.
(reference examples 1 to 6)
In the same manner as in example 1, a silicon substrate provided with a thermally modified adhesive layer was formed. In reference examples 1 to 6, solutions obtained by mixing and stirring 20 mass% of a cycloolefin polymer (manufactured by JSR corporation, ARTON (registered trademark)) and 80 mass% of chloroform at room temperature were used. In reference examples 1 to 6, the silicon substrate coated with the solution was held on a hot plate set at different temperatures for 1 minute. The temperatures of the heating plates of reference examples 1 to 6 are shown in Table 1 below.
(elemental analysis by XPS)
For each of reference examples 2 to 5, the ratio of the number of oxygen atoms contained in the adhesive layer to the total of the number of oxygen atoms and the number of carbon atoms contained in the adhesive layer (the number of oxygen atoms/(the number of oxygen atoms + the number of carbon atoms) × 100 (%)) was determined using "K-Alpha" (seimer femtoli technologies). The results of these evaluations are shown in table 1 below.
(measurement of Infrared absorption Spectroscopy)
The infrared absorption spectrum of the adhesive layer was measured for each of reference examples 1 to 6 using "Nicolet 6700" (seimer feishell scientific). Then, the length of 1732cm was determined－1The integral value of the absorption peak of C ═ O stretching vibration expressed by the formula is 2947cm－1The ratio of the integral value of the absorption peak of C-H stretching vibration (C ═ the integral value of the absorption peak of O stretching vibration/the integral value (dimensionless number) of the absorption peak of C-H stretching vibration) is shown. The results of these evaluations are shown in table 1 below.
[ Table 1]
Figure BDA0002212419840000221
As shown in table 1, the lower the temperature of the hot plate, the smaller the proportion of the number of oxygen atoms contained in the adhesive layer to the total of the number of oxygen atoms and the number of carbon atoms contained in the adhesive layer. Further, the lower the temperature of the heater plate, the smaller the ratio of the integral value of the absorption peak of the C ═ O stretching vibration to the integral value of the absorption peak of the C — H stretching vibration. From these results, it can be seen that: the ratio of the number of oxygen atoms contained in the adhesive layer to the total of the number of oxygen atoms and the number of carbon atoms contained in the adhesive layer, and the ratio of the integrated value of the absorption peak of C ═ O stretching vibration to the integrated value of the absorption peak of C — H stretching vibration can be used as indices of the degree of thermal modification of the olefin-based polymer contained in the adhesive layer.

Claims (11)

1. An optical element for terahertz waves, wherein,
the disclosed device is provided with:
an optical component having a silicon surface;
an antireflection film having an organic resin containing a cyclic olefin polymer as a main component and inorganic particles dispersed in the organic resin; and
an adhesive layer that is positioned between the optical member and the antireflection film in a thickness direction of the antireflection film and bonds the silicon surface of the optical member and the antireflection film,
the adhesive layer contains a thermally modified olefin polymer.
2. An optical element for terahertz waves, wherein,
the disclosed device is provided with:
an optical member;
an antireflection film having an organic resin containing a cyclic olefin polymer as a main component and inorganic particles dispersed in the organic resin; and
an adhesive layer which is located between the optical member and the antireflection film in a thickness direction of the antireflection film and bonds a surface of the optical member and the antireflection film,
the adhesive layer contains a thermally modified olefin polymer.
3. The optical element for terahertz waves according to claim 1 or 2, wherein,
the proportion of the volume of the inorganic particles per unit volume of the antireflection film is higher as the inorganic particles are closer to the optical member in the thickness direction.
4. The optical element for terahertz waves according to claim 3, wherein,
the antireflection film has a plurality of layers laminated on each other in the thickness direction,
the layers each contain the organic resin containing the cyclic olefin polymer as a main component and the inorganic particles dispersed in the organic resin,
the proportion of the volume occupied by the inorganic particles per unit volume of the layer is higher as the layer is closer to the optical member in the thickness direction.
5. The optical element for terahertz waves according to any one of claims 1 to 4, wherein,
the antireflection film has: a first surface opposing the optical member in the thickness direction, and a second surface located on an opposite side of the first surface,
the optical element for terahertz waves further includes a bubble-containing layer that is located on the second surface and contains a plurality of bubbles.
6. The optical element for terahertz waves according to claim 5, wherein,
the surface of the bubble-containing layer is in a concave-convex shape.
7. The optical element for terahertz waves according to any one of claims 1 to 4, wherein,
the antireflection film has: a first surface opposing the optical member in the thickness direction, and a second surface located on an opposite side of the first surface,
the second surface is in a concave-convex shape.
8. The optical element for terahertz waves according to any one of claims 1 to 7, wherein,
the thickness of the adhesive layer is 1nm to 100 [ mu ] m.
9. The optical element for terahertz waves according to any one of claims 1 to 8, wherein,
the inorganic particles are silicon particles, titanium oxide particles, or diamond particles.
10. A method for manufacturing an optical element for terahertz waves,
the method comprises the following steps:
preparing an optical member having a silicon surface;
forming an adhesive layer containing an olefin polymer on the silicon surface of the optical member;
thermally modifying the olefin polymer contained in the adhesive layer by heating, and bringing the adhesive layer into close contact with the silicon surface; and
and a step of bonding an antireflection film having an organic resin containing a cyclic olefin polymer as a main component and inorganic particles dispersed in the organic resin to the optical member via the adhesive layer containing the thermally modified olefin polymer.
11. A method for manufacturing an optical element for terahertz waves,
the method comprises the following steps:
a step of preparing an optical component;
forming an adhesive layer containing an olefin polymer on a surface of the optical member;
a step of thermally modifying the olefin polymer contained in the adhesive layer by heating and bringing the adhesive layer into close contact with the surface; and
and a step of bonding an antireflection film having an organic resin containing a main component of a cyclic olefin polymer and inorganic particles dispersed in the organic resin to the optical member via the adhesive layer containing the thermally modified olefin polymer.
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CN1502048A (en) * 2001-04-10 2004-06-02 富士胶片株式会社 Antireflection film, polarizing plate, and apparatus for displaying an image
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CN104813199A (en) * 2012-11-30 2015-07-29 佳能株式会社 Optical member and method for manufacturing the same
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CN1502048A (en) * 2001-04-10 2004-06-02 富士胶片株式会社 Antireflection film, polarizing plate, and apparatus for displaying an image
US20080239486A1 (en) * 2007-03-08 2008-10-02 Shinya Kato Antireflection laminate, polarizing plate and image display device
CN102712832A (en) * 2010-01-08 2012-10-03 阿尔卑斯电气株式会社 TAC base for cycloolefin polymer bonding, TAC bonding member, and liquid crystal display device
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