JP2004279558A

JP2004279558A - Method for manufacturing fine optical element

Info

Publication number: JP2004279558A
Application number: JP2003068312A
Authority: JP
Inventors: Tetsuji Yano; 哲司矢野; Shuichi Shibata; 修一柴田
Original assignee: Rikogaku Shinkokai
Current assignee: Rikogaku Shinkokai
Priority date: 2003-03-13
Filing date: 2003-03-13
Publication date: 2004-10-07

Abstract

<P>PROBLEM TO BE SOLVED: To easily manufacture with excellent shape reproducibility a fine optical element having a shape formed by combination of part of a spherical surface of several to hundreds of μm and a surface transferred from a substrate, e.g. a plane. <P>SOLUTION: A glass or plastic fine optical element having a shape including part of a spherical surface and a surface transferred from a substrate is obtained by placing a liquid drop formed by heating glass or plastic powder for forming an optical element, on the substrate and then cooling it. As the optical element, a lens is exemplified. Preferably, the liquid drop is formed by heating the powder until its viscosity decreases below 108 Pa.s. The shape including part of the spherical surface and the surface transferred from the substrate, e.g. a plane is preferably hyperhemispheric. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、微小光学素子の作製方法に関する。さらに詳しくは、本発明は、数μｍから数百μｍまでの大きさを有し球面の一部と基板より転写された表面、たとえば平面、との組合わせによる形状を有するレンズ等の微小光学素子の作製方法に関するものである。
【０００２】
【従来の技術】
ガラスを液滴化する方法には、ガス燃料あるいは液体燃料を燃焼させたフレーム（火炎）中にガラス微粉を投入することによって空中にて液滴化し、それらを捕集する方法がある。この場合、球形とすることが可能なサイズに限界がある。数μｍといった微小なものを投入すると、火炎によって生成する気流によって吹き飛ばされ、火炎中にガラス微粉を導入することが難しい。そのため、現在作製することができるガラス球（ビーズ）は数百μｍから数ｍｍである。また、この方法では一部を平面とするガラス、たとえば球の一部分を平面的に切り取った形状である超半球ガラスを作成することは原理的に不可能である。
【０００３】
球面と平面とを併せ持つ微小レンズ等の微小光学素子の作製方法としては、上記のような手法を用いて作製された球状のガラスを固定し、その一部を研磨によって平坦化する方法があり、工業的にも生産に用いられている。しかし、この方法で作製可能なガラス素子は、大きさとして１ｍｍ程度のものが下限であり、数μｍあるいは数十μｍサイズの場合には、研磨に用いられる研磨剤のサイズと同等となるため、技術的には不可能である。
【０００４】
一方、プラスチック微小光学素子については、ノズルにより液滴状に原料を噴霧し固化させる方法があるが、それに平面形状を付与するためにはガラスと同様に研摩する方法が必要であり、その大きさの下限についてはガラスと同様な技術的困難さがある。
【０００５】
以上のように、これまでの超半球に代表され球面の一部と平面とによって構成される形状を有する微小光学素子は、大きさ数百μ以上の直径を有する球状ガラス等を研磨して一部を平面とすることによって作製されている。これらは、作製可能な光学素子の大きさの下限が大きいことに加え、所望の形状の素子を得るのに複数の工程を経なければならない。
【０００６】
【発明が解決しようとする課題】
本発明は、現状では作製することが難しい数〜数百μｍのサイズを有する球面の一部と基板より転写された表面、たとえば平面、との組合わせによる形状を有する微小光学素子を容易に、形状再現性良好に作製し得る方法を提供するものである。
【０００７】
【課題を解決するための手段】
本発明の要旨は、光学素子を形成するためのガラスもしくはプラスチック粉末を加熱して形成される液滴を基板上に載置し、ついで冷却することにより、球面の一部と基板より転写された表面とを含む形状を有するガラスもしくはプラスチック微小光学素子を得ることを特徴とする微小光学素子の作製方法にある。
【０００８】
【発明の実施の形態】
本発明の微小光学素子の作製方法においては、光学素子を形成するためのガラスもしくはプラスチック粉末を加熱して形成される液滴を基板上に載置し、ついで冷却することにより、球面の一部と基板より転写された表面とを含む形状を有するガラスもしくはプラスチック微小光学素子を得ることができる。このような液滴を得る態様としては、（１）ガラスもしくはプラスチック粉末を基板上に載置し、該粉末を加熱して液滴を形成させる方法、（２）ガラスもしくはプラスチック粉末を加熱して部分的に液滴が形成されたガラスもしくはプラスチック粉末を基板上に移置して戴置し、該粉末を加熱して全面的に液滴を形成させる方法、または（３）ガラスもしくはプラスチック粉末を加熱して形成された液滴を基板上に移置して戴置する方法が挙げられる。このうち、（２）もしくは（３）、特に（３）、の態様においては、液滴を移動させて基板上に移置するという工学的な操作（たとえば、形状のコントロールに影響しない態様で、基板への移動中に加熱しながら液滴を形成させる）が要求されるのに対し、（１）の態様が最も簡易に液滴を得ることができるので好適である。
【０００９】
光学素子としてはレンズ、微小光源等が挙げられる。上記の粉末の粒径は、好適には１μｍ〜１ｍｍであり、粉砕、篩分けにより粒度調整されるのが好ましい。本発明において用いられるガラスもしくはプラスチック粉末は熱溶融し、光学素子になりうるものであれば特に制限されず、目的により適宜選択されうる。好適には、これらのガラスもしくはプラスチックは、紫外域から赤外域までの間の波長範囲において光学的透明性を示す波長域を有するものが選択される。
【００１０】
たとえば、ガラスとしてはクラウン系、フリント系、バリウム系、ランタン系リン酸塩系もしくはフッ素含有系の光学ガラス、またはカルコゲンガラスもしくはテルライトガラス等から選ばれる。
【００１１】
プラスチックとしては、ポリメタクリル酸メチル（ＰＭＭＡ）、ポリカーボネート、ポリスチレン、ポリ４−メチルペンテン−１、ポリ塩化ビニル、ポリ酢酸ビニルもしくはポリフェニル酢酸ビニル等から選ばれる。
【００１２】
ガラスもしくはプラスチック粉末を載置する基板としては、加熱により形成される液滴との間に反応による化学的結合を形成せず、適切な濡れ性を保持しうるものが望ましく、好適にはガラスとの反応不活性の観点から炭素質基板が挙げられる。さらに具体的には、グラファイトもしくはガラス質カーボン基板、または炭素化合物（たとえば高分子化合物または炭化ケイ素等の無機化合物）基板上にグラファイトもしくはガラス質カーボンの炭素質膜を形成させた基板等が挙げられる。
【００１３】
この基板の中心線平均粗さは、素子に形成される平面の性状（平坦性等）の観点から１〜１００ｎｍであるのが好ましい。
【００１４】
基板上に載置された該粉末は、好適には粘性が１０^８Ｐａ．ｓ以下の流動性を有する温度まで加熱され、液滴を形成され、ついで冷却することにより球面の一部と平面とを含み、球面部分の曲率半径が２〜７００μｍである形状を有する微小光学素子、たとえば径が２〜７００μｍ程度である超半球レンズが得られる。
【００１５】
加熱手段はとくに限定されず、たとえば電気炉、二酸化炭素レーザー加熱等が好適に使用され得る。
【００１６】
本発明における球面の一部と基板より転写された表面とを含む形状は、目的に応じて作製条件を適宜選定することにより選定しうる。基板より転写された表面は、基板表面を選ぶことにより任意の形状とすることができるが、通常は平面であり、球の部分の比率も自由に選定することができる。
【００１７】
たとえば超半球形状の素子を作製する場合、たとえば適当な大きさのガラス粉を、表面粗さが制御された炭素質よりなる基板上において、ガラスが溶けて液滴を形成できる温度に昇温・保持し、ガラス液滴に作用する表面張力の関係を利用して超半球状とし、その後冷却することによって得られる。基板の表面粗さや処理条件を変えることによって、半球度を制御することができる。
【００１８】
以上のように、本発明においては、質量および／または体積を整えたガラスもしくはプラスチック粉末を用いることにより、１回の処理操作でたとえば超半球形状まで一度に加工することができ、かつ、基板の平坦さをコントロールするもので、所望の半球度を有するレンズを作成することが可能である。
【００１９】
ガラス等の融液の表面張力を利用し、研磨工程を経ないため、光学波長以下のナノメートルレベルで充分に滑らかな自由表面を付与できる。超半球レンズは、屈折率、用いる波長に応じて所望の半球度を付与しなければならないが、ガラス等の組成を変えることで屈折率を変えることができ、また炭素質基板の表面粗さをナノメートルオーダーで変化させることで、所望の半球度に制御して作製することができる（粗いと半球部分の比率が大きくなる）。また、作製できる大きさ（直径）の下限が研磨などでは作製することが不可能な数μｍまで下げることができる。
【００２０】
本発明において得られる超半球等の微小光学素子は、たとえば光ファイバー、発光ダイオード、レーザー発振の分野において用いられているマイクロレンズとして、さらにはたとえば波長限界以下の大きさの超解像観察を可能にする固形液浸レンズ（ＳｏｌｉｄＩｍｍｅｒｓｉｏｎＬｅｎｓ（ＳＩＬ））として利用しうる。たとえば、この固形液浸レンズとして用いると、軽量化、さらに光記録媒体における高密度化、光学顕微鏡における高分解能化、等を実現しうる。
【００２１】
【実施例】
以下に、実施例によりさらに本発明を詳細に説明するが、本発明はこれらの態様に限定されるものではない。
実施例１
２０Ｎａ_２Ｏ−１０ＣａＯ−７０ＳｉＯ_２（ｍｏｌ％）（Ｔｇ：５１５℃）の組成を有し、種々の粒径（３〜５０μｍ）を有するソーダ石灰ガラス粉末を中心線平均粗さ４〜５ｎｍに鏡面研磨したガラス質カーボンの炭素質基板上、ならびに中心線平均粗さ１０〜５０ｎｍとしたガラス質カーボンの炭素質基板上、に載せ、窒素／水素（５：１）混合ガス雰囲気下で８００℃、３０分間、熱処理した後、放冷した。得られた超半球ガラス試料を、光学顕微鏡または電子顕微鏡にて観察し、超半球ガラスと炭素質基板との接触角を測定して超半球度を評価した。図１はガラスと炭素質基板との接触角を模式的に示す。
【００２２】
得られた超半球状ガラスの粒径と接触角の関係を図２に示す。作製できた超半球の大きさは、もっとも小さいもので直径約５μｍであり、直径約４０μｍの超半球ガラスも作製できた。同じ平面粗さを有する基板を用いた場合、粒径によって接触角は系統的に変化した。また、平面粗さの異なる基板を用いると接触角が変化した。直径２５μｍの場合、接触角を約１０度変化させることができた。これにより、基板の表面粗さを変えることにより、同じガラスでも異なる接触角、すなわち超半球度を有するガラスを作製できることが分かった。
【００２３】
【発明の効果】
本発明によれば、現状では作製することが難しい数〜数百μｍのサイズを有する球面の一部と基板より転写された表面、たとえば平面、との組合わせによる形状を有する微小光学素子を容易に、形状再現性良好に作製し得る。
【図面の簡単な説明】
【図１】図１は超半球ガラスと炭素質基板との接触角を模式的に示す。
【図２】実施例１において得られた超半球状ガラスの粒径と接触角の関係を示す。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a micro optical element. More specifically, the present invention relates to a micro-optical element such as a lens having a size from several μm to several hundred μm and having a shape formed by a combination of a part of a spherical surface and a surface transferred from a substrate, for example, a plane. The method relates to a method for producing the same.
[0002]
[Prior art]
As a method of forming glass into droplets, there is a method in which glass fine powder is put into a flame (flame) in which gaseous fuel or liquid fuel is burned to form droplets in the air, and these are collected. In this case, there is a limit to the size that can be made spherical. When a minute thing such as several μm is thrown in, it is blown off by an air current generated by the flame, and it is difficult to introduce glass fine powder into the flame. Therefore, glass spheres (beads) that can be manufactured at present are several hundred μm to several mm. Further, in this method, it is in principle impossible to produce glass having a partly flat surface, for example, a super-hemispherical glass in which a part of a sphere is cut out in a plane.
[0003]
As a manufacturing method of a micro optical element such as a micro lens having both a spherical surface and a flat surface, there is a method of fixing a spherical glass manufactured using the above-described method and flattening a part of the glass by polishing. It is also used industrially for production. However, the lower limit of the glass element that can be manufactured by this method is about 1 mm in size, and when the size is several μm or several tens μm, the size is equal to the size of the abrasive used for polishing. Technically impossible.
[0004]
On the other hand, for plastic micro optical elements, there is a method of spraying and solidifying the raw material in the form of droplets using a nozzle, but in order to give it a planar shape, a method of polishing like glass is necessary, and its size is large. The lower limit has the same technical difficulty as glass.
[0005]
As described above, a micro-optical element having a shape constituted by a part of a spherical surface and a plane represented by a conventional super-hemisphere, is obtained by polishing spherical glass or the like having a diameter of several hundred μ or more. It is produced by making the part flat. These require a large number of steps to obtain an element having a desired shape in addition to a large lower limit of the size of an optical element that can be manufactured.
[0006]
[Problems to be solved by the invention]
The present invention can easily produce a micro-optical element having a shape formed by a combination of a part of a spherical surface having a size of several to several hundred μm, which is difficult to produce at present, and a surface transferred from a substrate, for example, a plane. An object of the present invention is to provide a method that can be manufactured with good shape reproducibility.
[0007]
[Means for Solving the Problems]
The gist of the present invention is that a droplet formed by heating glass or plastic powder for forming an optical element is placed on a substrate, and then cooled, so that a part of the spherical surface and the substrate are transferred from the substrate. A glass or plastic micro optical element having a shape including a surface is obtained.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
In the method for manufacturing a micro optical element of the present invention, a droplet formed by heating glass or plastic powder for forming an optical element is placed on a substrate, and then cooled to form a part of a spherical surface. A glass or plastic micro-optical element having a shape including the surface and the surface transferred from the substrate can be obtained. As a mode for obtaining such a droplet, (1) a method of placing a glass or plastic powder on a substrate and heating the powder to form a droplet, and (2) a method of heating the glass or plastic powder. A method in which glass or plastic powder in which droplets are partially formed is transferred onto a substrate and placed thereon, and the powder is heated to form droplets entirely, or (3) glass or plastic powder is formed. There is a method in which a droplet formed by heating is transferred to and placed on a substrate. Among them, in the mode (2) or (3), particularly the mode (3), an engineering operation of moving a droplet and transferring it onto a substrate (for example, in a mode that does not affect shape control, (A method of forming droplets while heating while moving to the substrate) is required, whereas the mode (1) is preferable because droplets can be obtained most easily.
[0009]
Examples of the optical element include a lens and a minute light source. The particle size of the above powder is preferably 1 μm to 1 mm, and is preferably adjusted by pulverization and sieving. The glass or plastic powder used in the present invention is not particularly limited as long as it can be melted by heat and can become an optical element, and can be appropriately selected depending on the purpose. Preferably, these glasses or plastics are selected to have a wavelength range exhibiting optical transparency in a wavelength range between the ultraviolet region and the infrared region.
[0010]
For example, the glass is selected from crown-based, flint-based, barium-based, lanthanum-based phosphate-based or fluorine-containing optical glass, chalcogen glass, tellurite glass, and the like.
[0011]
The plastic is selected from polymethyl methacrylate (PMMA), polycarbonate, polystyrene, poly-4-methylpentene-1, polyvinyl chloride, polyvinyl acetate, polyphenyl vinyl acetate, and the like.
[0012]
As the substrate on which the glass or plastic powder is placed, a substrate that does not form a chemical bond due to a reaction with droplets formed by heating and that can maintain appropriate wettability is desirable. From the viewpoint of reaction inertness, a carbonaceous substrate can be mentioned. More specifically, a graphite or vitreous carbon substrate, or a substrate in which a carbonaceous film of graphite or vitreous carbon is formed on a carbon compound (for example, a high molecular compound or an inorganic compound such as silicon carbide) substrate, and the like can be given. .
[0013]
The center line average roughness of this substrate is preferably from 1 to 100 nm from the viewpoint of the properties (flatness and the like) of a plane formed on the element.
[0014]
Powder placed on the substrate is preferably viscous 10 8 ^Pa. a micro optical element having a shape including a part of a spherical surface and a flat surface by being cooled to a temperature having a fluidity of not more than s, and then cooling, wherein the radius of curvature of the spherical portion is 2 to 700 μm. For example, a super hemispherical lens having a diameter of about 2 to 700 μm is obtained.
[0015]
The heating means is not particularly limited, and for example, an electric furnace, carbon dioxide laser heating, or the like can be suitably used.
[0016]
The shape including a part of the spherical surface and the surface transferred from the substrate in the present invention can be selected by appropriately selecting the manufacturing conditions according to the purpose. The surface transferred from the substrate can be formed into an arbitrary shape by selecting the surface of the substrate. However, the surface is usually flat, and the ratio of the spherical portion can be freely selected.
[0017]
For example, when fabricating a super hemispherical element, for example, a glass powder of an appropriate size is heated to a temperature at which glass can be melted to form droplets on a substrate made of carbonaceous material having a controlled surface roughness. It is obtained by holding, making it into a super hemisphere using the relationship of surface tension acting on the glass droplet, and then cooling it. The hemisphericity can be controlled by changing the surface roughness of the substrate and the processing conditions.
[0018]
As described above, in the present invention, by using glass or plastic powder of which the mass and / or volume is adjusted, it is possible to process to a super-hemispherical shape at one time by one processing operation, By controlling the flatness, it is possible to produce a lens having a desired hemisphericity.
[0019]
Since the polishing step is not performed by utilizing the surface tension of the melt such as glass, a sufficiently smooth free surface can be provided at the nanometer level below the optical wavelength. The super-hemispherical lens must provide a desired hemisphericity according to the refractive index and the wavelength used, but the refractive index can be changed by changing the composition of glass or the like, and the surface roughness of the carbonaceous substrate can be reduced. By changing it in the order of nanometers, it is possible to control and produce a desired hemispherical degree (roughness and hemispherical portion ratio increase). Further, the lower limit of the size (diameter) that can be manufactured can be reduced to several μm, which cannot be manufactured by polishing or the like.
[0020]
The micro optical element such as a super hemisphere obtained in the present invention can be used as, for example, an optical fiber, a light emitting diode, or a micro lens used in the field of laser oscillation, and further, for example, enables super resolution observation of a size smaller than a wavelength limit. As a solid immersion lens (Solid Immersion Lens (SIL)). For example, when this solid immersion lens is used, weight reduction, higher density in an optical recording medium, higher resolution in an optical microscope, and the like can be realized.
[0021]
【Example】
Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these embodiments.
Example 1
A soda-lime glass powder having a composition of 20Na ₂ O-10CaO-70SiO ₂ (mol%) (Tg: 515 ° C.) and various particle sizes (3 to 50 μm) is mirror-finished to a center line average roughness of 4 to 5 nm. Placed on a polished vitreous carbon carbonaceous substrate and a vitreous carbon carbonaceous substrate having a center line average roughness of 10 to 50 nm, at 800 ° C. in a nitrogen / hydrogen (5: 1) mixed gas atmosphere, After heat treatment for 30 minutes, it was allowed to cool. The obtained super hemispheric glass sample was observed with an optical microscope or an electron microscope, and the contact angle between the super hemispheric glass and the carbonaceous substrate was measured to evaluate the super hemispheric degree. FIG. 1 schematically shows a contact angle between glass and a carbonaceous substrate.
[0022]
FIG. 2 shows the relationship between the particle size and the contact angle of the obtained super hemispherical glass. The size of the super hemisphere that could be produced was the smallest, about 5 μm in diameter, and a super hemisphere glass with a diameter of about 40 μm could also be produced. When substrates having the same plane roughness were used, the contact angle varied systematically with the particle size. Further, when substrates having different plane roughness were used, the contact angle changed. When the diameter was 25 μm, the contact angle could be changed by about 10 degrees. Thus, it was found that by changing the surface roughness of the substrate, glass having different contact angles, that is, super-hemisphericity, can be produced even with the same glass.
[0023]
【The invention's effect】
According to the present invention, a micro optical element having a shape formed by a combination of a part of a spherical surface having a size of several to several hundred μm, which is difficult to manufacture at present, and a surface transferred from a substrate, for example, a flat surface, can be easily manufactured. In addition, it can be manufactured with good shape reproducibility.
[Brief description of the drawings]
FIG. 1 schematically shows a contact angle between a super-hemispherical glass and a carbonaceous substrate.
FIG. 2 shows the relationship between the particle size and the contact angle of the super hemispherical glass obtained in Example 1.

Claims

A droplet formed by heating glass or plastic powder for forming an optical element is placed on a substrate, and then cooled to form a shape including a part of a spherical surface and a surface transferred from the substrate. A method for producing a micro-optical element, comprising obtaining a glass or plastic micro-optical element.

2. The method according to claim 1, wherein a glass or plastic powder is placed on a substrate, and the powder is heated to form droplets.

2. A method according to claim 1, wherein the glass or plastic powder on which the droplets are partially formed by heating the glass or plastic powder is transferred onto a substrate, and the powder is heated to form droplets over the entire surface. A manufacturing method of the micro optical element according to the above.

2. The method according to claim 1, wherein the droplet formed by heating the glass or plastic powder is transferred to and placed on a substrate.

2. The method according to claim 1, wherein the optical element is a lens.

The method according to claim 1, wherein the particle size of the powder is 1 μm to 1 mm.

The viscosity of the powder is 10 ⁸ Pa. The method according to claim 1, wherein the droplets are formed by heating to a temperature not higher than s.

2. The method according to claim 1, wherein the surface transferred from the substrate is a flat surface.

9. The method according to claim 8, wherein the shape including a part of the spherical surface and the plane is a super hemisphere.

The method according to any one of claims 1 to 9, wherein the glass or plastic has a wavelength range showing optical transparency in a wavelength range from the ultraviolet range to the infrared range.

2. The method according to claim 1, wherein the glass is selected from crown-based, flint-based, barium-based, lanthanum-based phosphate-based or fluorine-containing optical glass, or chalcogen glass or tellurite glass.

2. The method according to claim 1, wherein the plastic is selected from polymethyl methacrylate, polycarbonate, polystyrene, poly-4-methylpentene-1, polyvinyl chloride, polyvinyl acetate and polyphenylvinyl acetate.

The method according to claim 1, wherein the substrate is a carbonaceous substrate.

2. The method according to claim 1, wherein the substrate has a center line average roughness of 1 to 100 nm.

2. The method according to claim 1, wherein the radius of curvature of the spherical portion is 2 to 700 [mu] m.