JP4302438B2 - Method for manufacturing diffractive optical element - Google Patents

Description

【００５９】
即ち、接着層の厚さ：ＴＳとオーバコート層の厚さ：ＴＯを等しくすることにより、チッピングの大きさが１００μｍ以下（評価「○」）となることが分かった。
【００６０】
実施例２
厚さ：１．０ｍｍ、直径：φ＝１００ｍｍの円形状の原透明基板に、エポキシ系の紫外線硬化型接着剤により厚さ：４０μｍの接着層を設け、原有機材料膜として、厚さ：８０μｍの有機の高分子複屈折膜を貼り合わせ、減圧下で一体化させた後、紫外線を照射し、１００℃にて１０分間のベーキングを行ない完全に接着層を硬化させた（図３（ａ）の状態）。
【００６１】
ついで、原有機材料膜上に金属（Ａｌ）の膜による周期パターン（ピッチ：３．０μｍ）を複数個、格子配列状に形成した（図３（ｂ）の状態）。この周期パターンをマスクとして有機材料膜のドライエッチングを行ない、金属マスクを除去して有機材料膜の表面に「凹凸による回折格子」を複数個、格子配列状に形成した（図３（ｃ）、図４の状態）。「個々の回折格子を構成する凹凸」の断面形状は、図１に示すように「実質的に矩形形状」である。
【００６２】
複数の回折格子が格子配列状に形成された原有機材料膜の上に、厚さ：４０μｍのスペーサを配置し、オーバコート層となる「エポキシ系の紫外線硬化樹脂」をボッティングし、その上から厚さ：１．０ｍｍの原保護基板をのせ、適度に加圧し、凹凸格子内にオーバコート剤を充填し、厚さ：４０μｍ（回折格子の凹凸の深さを加えない厚さ）のオーバコート層を形成し、紫外線を照射後、１００℃で１０分間のベーキングを行ない完全に硬化させた（図３（ｄ）の状態）。
【００６３】
以下、ダイシング装置により、厚さ：０．２０ｍｍ、外径：６０ｍｍの「レジン系ブレード」を用い、全体を「５．０ｍｍ×５．０ｍｍサイズのチップ」に切断して分離し、回折光学素子を複数個（１２０個）作製した。この時の「ブレード摩耗量」は４０μｍであった。
【００６４】
比較例３
実施例２において、エポキシ系の紫外線硬化型接着剤による接着層の厚さを１２０μｍとし、有機材料膜（有機の高分子複屈折膜）の厚さを８０μｍとし、オーバコート層の厚さを１２０μｍとした。
【００６５】
ダイシング装置による切断は、厚さ：０．２０ｍｍ、外径：６０ｍｍの円板状の「レジン系ブレード」を用い、全体を「５．０ｍｍ×５．０ｍｍサイズのチップ」に切断して、回折光学素子を複数個（１２０個）作製した。この時のブレード摩耗量は２００μｍであった。
【００６６】
比較例４
実施例２において、エポキシ系の紫外線硬化型接着剤による接着層の厚さを１００μｍとし、オーバコート層の材料としてアクリル系の紫外線硬化樹脂を用い、オーバコート層の厚さを１００μｍとした。厚さ：０．１５ｍｍ、外径：６０ｍｍの円板状の「レジン系ブレード」を用い、全体を「５．０ｍｍ×５．０ｍｍサイズのチップ」に切断し、偏光回折素子を複数個（１２０個）作製した。この時のブレード摩耗量は５０μｍであった。
【００６７】

【００６８】
即ち、上記実施例１、２の回折光学素子は、原透明基板上に接着層を介して原有機材料膜を接着固定し、原有機材料膜の接着層と逆側の面に、凹凸による回折格子を複数個、格子配列状に形成し、形成された格子配列状の回折格子上にオーバコート層を形成し、オーバコート層に透明な原保護基板を固定して回折光学素子の格子状配列を得、ダイシング装置により複数の回折光学素子を個別的に分離する回折光学素子製造方法において、原透明基板上に原有機材料膜を接着固定する接着層の厚さ：ＴＳと、オーバコート層の厚さ：ＴＯを略等しくする回折光学素子製造方法により製造されたものである。
【００６９】
また実施例１、２の回折光学素子は、透明基板と、この透明基板上に接着層を介して接着固定され、接着層と逆側の面に、凹凸による回折格子を形成された有機材料膜と、この有機材料膜の上記回折格子を形成された側の面に設けられるオーバコート層と、このオーバコート層上に固定される透明な保護基板とを有する回折光学素子において、接着層の厚さとオーバコート層の厚さが略等しく、透明基板および／または保護基板の周面部のチッピングが１００μｍ以下である。
そして、有機材料膜が有機複屈折膜であり、オーバコート層が、有機複屈折膜の常光線に対する屈折率もしくは異常光線に対する屈折率と実質的に等しい屈折率を持つ等方性光学材料である（請求項４）。
【００７０】
実施例２では、接着層およびオーバコート層の厚さ（４０μｍ）が、原有機材料膜の厚さ（８０μｍ）よりも薄く（請求項２）、実施例１、２とも、接着層およびオーバコート層は同一材料で形成され（請求項１）、接着層およびオーバコート層は実施例１においてアクリル系、実施例２においてエポキシ系の材料により形成されている（請求項３）。
【００７１】
比較例３の回折光学素子は、チッピングの大きさという点では良好であるが素子を分離するときのブレードの磨耗が２００μｍと大きく、この方法では結局製造コストが高くなる（そのため、評価「△」としている）。比較例４の回折光学素子は、接着層の厚さ：ＴＳとオーバコート層の厚さ：ＴＯとは等しいが、チッピングは１５０μｍと大きい。これは、接着層（エポキシ系）とオーバコート層（アクリル系）の材料を同一としなかったことに起因すると考えられ、この点からして、接着層とオーバコート層とは同一材料であること（請求項１）が好ましいことが分かる。
【００７２】
なお、上記実施例１、２、比較例１、２、３、４を通じ、透明基板、保護基板の材質はＢＫ−７ガラス、有機材料膜としての高分子複屈折膜は、ポリエチレンテレフタレート（ＰＥＴ）である。また、接着層、オーバコート層に用いた紫外線硬化樹脂は何れも、アクリル系のものが前記ＴＢ３０４２、エポキシ系のものがＴＢ３１２１である。
【００７３】
【発明の実施の形態】
図５を参照して、光ピックアップ装置の実施の１形態を説明する。
光ピックアップ装置は、光源３０から放射される光を対物レンズ３７により光ディスク４０の記録面上に光スポットとして集光し、記録面により反射された戻り光束を、対物レンズ３７を介して光検出部３９へ導きつつ、光ディスク４０に対し情報の記録・再生・消去の１以上を行う光ピックアップ装置であり、光源３０と対物レンズ３７との間に回折光学素子３１が配置されている。回折光学素子３１は図１に示す如きものである。
【００７４】
図５の光ピックアップ装置では、光源３０である半導体レーザからの光が回折光学素子３１を透過する。回折光学素子３１は有機材料膜が有機複屈折膜であり「偏光ホログラム素子」として用いられる。
【００７５】
有機複屈折膜とオーバコート層とは、常光線に対する屈折率が実質的に等しく、光源側からの光は回折作用を受けることなく、そのまま回折光学素子３１を透過し、さらに１／４波長板３５を透過し、対物レンズ３７の作用により、光ディスク４０の記録面上に光スポットとして集光する。
【００７６】
記録面により反射された光は「戻り光束」となって対物レンズ３７、１／４波長板３５を透過し、偏光面が当初の方向から９０度旋回した直線偏光となり、回折光学素子３１に入射する。有機複屈折膜とオーバコート層は異常光線に対しては屈折率が異なるので、戻り光束は異常光線として回折光学素子３１による回折作用を受けて（１次回折光となり）光検出部３９へ向けて偏向される。このとき、戻り光束には回折光学素子３１により、例えば非点収差が与えられ、この光束は光検出部３９で受光され、非点収差法によるフォーカシング信号やプッシュプル法によるトラッキング信号、再生信号を発生させる。光検出部３９の出力は光記録媒体に記録された情報に対応する情報を担っているので、以後必要な処理を施すことによって画像情報、音声情報などを再生できる。
【００７７】
即ち、図５の光ピックアップ装置は、請求項４の方法で製造された回折光学素子を、光源３０側からの光束の光路と、光ディスク４０からの戻り光束の光路とを光路分離する偏光ホログラム素子３１として用いたものである。
【００７８】
図６は、光ディスクドライブ装置の実施の１形態を示す図である。
この光ディスクドライブ装置は、光ディスク４０に対し、光ピックアップ装置４１を用いて情報の記録・再生・消去の１以上を行う装置である。
【００７９】
光ディスク４０は保持部４７に保持され、「駆動手段」としてのモータＭｔで回転駆動される。セットされた光ディスク４０に対し光ピックアップ装置４１が、変位駆動手段４３により光ディスク４０の半径方向へ変位駆動されて記録・再生・消去の１以上を行う。制御手段４２は、光ピックアップ装置４１からの信号に基づく各種制御や再生信号の出力を制御するほか、装置全体の制御を行う。
【００８０】
即ち、図６の光ディスクドライブ装置は、光ディスク４０に対し、光ピックアップ装置４１を用いて情報の記録・再生・消去の１以上を行う光ディスクドライブ装置において、光ピックアップ装置として、例えば図５に示すようなものを用いたものである。
【００８１】
図５に示した光ピックアップ装置における偏光ホログラム素子３１として、実施例１、２の回折光学素子を用いることができ、この光ピックアップ装置を、図６の光ディスクドライブ装置に用いることができる。
【００８２】
有機複屈折膜に回折格子を設けた回折光学素子は、従来の「プリズムを接着したビームスプリッタ」よりも小型化が可能なので、光ピックアップ装置をコンパクトに実現でき、光ディスクドライブ装置の小型軽量化が可能である。
【００８３】
【発明の効果】
以上に説明したように、この発明によれば、新規な「回折光学素子の製造方法」を実現できる。
【００８４】
この発明の方法で製造される回折光学素子は、チッピングが小さいため機械的な保持・取り扱い（ハンドリング）を容易かつ確実に行うことができ、また、組付けの際、モニタの「回折光学素子像の輪郭部のぼやけ」が少なく、高精度の位置合わせを容易に実現でき、これを用いることにより、この発明の光ピックアップ装置や光ディスクドライブを低コストに実現できる。
【００８５】
また、この発明の回折光学素子製造方法は、上記回折光学素子を歩留まり良く低コストで製造できる。
【図面の簡単な説明】
【図１】回折光学素子の実施の１形態を説明するための図である。
【図２】回折光学素子におけるチッピングを説明するための図である。
【図３】回折光学素子の製造プロセスを説明するための図である。
【図４】原透明基板における原有機材料膜に形成された複数の回折格子の格子状配列を模式的に示す図である。
【図５】光ピックアップ装置の実施１形態を説明するための図である。
【図６】光ディスクドライブ装置の実施の１形態を説明するための図である。
【符号の説明】
１０ 透明基板
１０１ 接着層
１０２ 有機材料膜
１０３ オーバコート層
１０４ 保護基板
ＴＳ 接着層１０１の厚さ
ＴＯ オーバコート層１０３の厚さ[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a method for manufacturing a diffractive optical element.
[0002]
[Prior art]
A diffractive optical element is an “optical element that causes a desired diffraction phenomenon in light” and is widely used as an element that performs spectroscopy, light deflection, and the like.
[0003]
A variety of diffractive optical elements have been known. However, as a new diffractive optical element, an organic film or a polymer film is formed on an optically transparent substrate, and the surface of these films is formed by unevenness. Have been proposed (Patent Documents 1 to 3, etc.).
[0004]
The diffractive optical element described in the above publication is a “polarization hologram element” whose film has birefringence. For example, in an optical pickup device, “the optical path of the light beam from the light source side and the optical path of the return light beam from the optical disk are separated. Can be suitably used.
[0005]
To explain a little, the diffractive optical element used in the optical pickup device is “several millimeters square” in size, and is not manufactured separately, but several hundreds are manufactured at a time. Is done.
[0006]
That is, an adhesive layer is formed on a transparent substrate having a diameter of several tens mm to several hundreds of mm, for example, a transparent substrate having a diameter of 100 mm or 150 mm, and the same size as the substrate size is formed on the formed adhesive layer. An organic material film of a size smaller than that is placed and bonded and fixed to the substrate with an adhesive layer. As the adhesive constituting the adhesive layer, a thermosetting adhesive or a photocurable adhesive such as an ultraviolet curable adhesive can be used.
[0007]
A plurality of (usually 100 to 200) diffraction gratings are formed on the surface of the organic material film adhered to the transparent substrate. The diffraction grating is formed by forming a thin film of metal or oxide on the organic material film, patterning the film by photolithography to form an etching mask corresponding to the diffraction grating group, and performing dry etching via this mask. Can be done.
[0008]
After forming the diffraction grating, an overcoat layer is formed as necessary, and a protective transparent substrate is further placed on the overcoat layer as required to integrate the whole. Thereafter, cutting is performed using a dicing apparatus to obtain individual diffractive optical elements. The overcoat layer also has a function as an adhesive for bonding the organic material film on which the diffraction grating is formed and the protective substrate.
[0009]
By providing the overcoat layer and the protective substrate, it is possible to effectively protect the diffraction gratings in the individual diffractive optical elements, and the handling of the diffractive optical elements becomes easy.
[0010]
As described above, the diffractive optical element having the overcoat layer and the protective substrate is sandwiched between the organic material film on which the diffraction grating is formed and the adhesive layer, and the overcoat layer is transparent between the transparent substrate and the protective substrate. Although it has a structure, when individual diffractive optical elements are separated by a dicing apparatus, a “chip” called “chipping” tends to occur in a cut surface portion of a transparent substrate or a protective substrate.
[0011]
When chipping becomes large, when the diffractive optical element is assembled in an optical apparatus such as an optical pickup, mechanical holding and handling (handling) of the diffractive optical element becomes unstable, making assembly difficult. In addition, during the above assembly, the assembly position of the diffractive optical element is aligned while monitoring the assembly position with a video camera. It is difficult to ensure the accuracy of “blurring” and alignment.
[0012]
[Patent Document 1]
JP 2000-221325 A
[Patent Document 2]
JP 2000-75130 A
[Patent Document 3]
JP-A-11-174226
[0013]
[Problems to be solved by the invention]
An object of the present invention is to effectively reduce chipping in a diffractive optical element.
[0014]
[Means for Solving the Problems]
  The diffraction grating manufactured by the manufacturing method of the present invention will be described.The diffractive optical element is “a transparent substrate, an organic material film that is bonded and fixed on the transparent substrate via an adhesive layer, and has a diffractive grating formed on the surface opposite to the adhesive layer, and the diffraction of the organic material film. In the diffractive optical element having an overcoat layer provided on the surface on which the grating is formed and a transparent protective substrate fixed on the overcoat layer, the thickness of the adhesive layer and the thickness of the overcoat layer are Approximately, chipping of the peripheral part of the transparent substrate and / or protective substrate is 100 μmIt is.
[0015]
If the chipping size is 100 μm or less, there is little “blurring of the outline” of the diffractive optical element image for monitoring the assembly position when the diffractive optical element is assembled to an optical device such as an optical pickup, The alignment accuracy can be ensured and handling is not hindered.
[0016]
  the aboveThe diffractive optical element "is an isotropic optical material having an organic birefringent film as an organic material film and a refractive index substantially equal to the refractive index for ordinary light or extraordinary light of the organic birefringent film as an overcoat layer ( Use optical properties that do not depend on direction)it can.When “non-birefringent” is used as the organic material film, the overcoat layer is formed of an organic material film and “a material having a different refractive index with respect to the used wavelength”.
[0017]
  The method for producing a diffractive optical element according to the present invention is described as follows: “A raw organic material film is bonded and fixed on an original transparent substrate via an adhesive layer, and a plurality of diffraction gratings with unevenness are formed on the surface opposite to the adhesive layer of the original organic material film. Forming a grating array, forming an overcoat layer on the formed grating array diffraction grating, fixing a transparent original protective substrate to the overcoat layer, obtaining a grating array of diffractive optical elements, and dicing A diffractive optical element manufacturing method in which a plurality of diffractive optical elements are individually separated by an apparatus '', characterized by the following points:To do.
[0018]
That is, the thickness of the adhesive layer TS for adhering and fixing the original organic material film on the original transparent substrate: TS and the thickness of the overcoat layer: TO are substantially equal.
[0019]
  Then, “the adhesive layer and the overcoat layer are formed of the same material” (claim 1).
  Claim 1In the diffractive optical element manufacturing method, “the thickness of the adhesive layer and the overcoat layer should be smaller than the thickness of the original organic material film”.(Claim 2).
[0020]
  Claim 1 or 2In the described diffractive optical element manufacturing method, the adhesive layer and the overcoat layer can be formed of an “acrylic or epoxy material” (Claim 3). Examples of acrylic materials include TB3042, TB3042B, and TB3042C manufactured by ThreeBond Co., Ltd., and examples of epoxy materials include TB3121 manufactured by ThreeBond Co., Ltd.
[0021]
  Claim1-3In the method for producing a diffractive optical element according to any one of the above, “the organic birefringent film is used as the organic material film, and the overcoat layer substantially has a refractive index with respect to an ordinary ray or a refractive index with respect to an extraordinary ray. "Use isotropic optical materials with equal refractive indices (those whose optical properties do not depend on direction)"Claim 4).
[0022]
  Claim 4 aboveManufactured by the diffractive optical element manufacturing method describedThe diffractive optical element is a polarization hologram elementUsed as.
[0023]
  This polarization hologram element is used in an optical pickup device."Polarization hologram element that separates the optical path of the luminous flux from the light source and the optical path of the returning luminous flux from the optical disk"Can be used as
[0024]
  UpThe optical pickup apparatus can be used in an optical disk drive apparatus that performs one or more of recording / reproducing / erasing information on / from an optical disk..
[0025]
  To supplement a little,Method for manufacturing the diffractive optical elementIn “to obtain a lattice-like arrangement of diffractive optical elements and separate a plurality of diffractive optical elements individually by a dicing apparatus”, a transparent substrate when the grating array of diffractive optical elements is formed is used.Claim 1The “original transparent substrate portion” in the individual diffractive optical elements individually separated by the dicing apparatus isMentioned above“Transparent substrate”. Therefore, the transparent substrate and the original transparent substrate are names before and after division by cutting the same transparent substrate.
  Similarly,Claim 1The “original organic material film” and “original protective substrate” in FIG. 5 are names of the same organic material film and protective substrate before and after cutting by the dicing apparatus.
[0026]
The “original transparent substrate” has a parallel plate shape, and generally has a diameter of several tens to several hundreds of mm and a disk shape, for example, a diameter of 100 mm or 150 mm, and an orientation flat is formed as necessary. In general, the thickness is about 0.3 mm to several mm.
[0027]
As a material of such “original transparent substrate / transparent substrate”, a BK-7 glass substrate, a quartz glass substrate, a Pyrex (registered trademark) glass substrate, a crystalline glass (trade name: Neoceram) substrate, and the like are suitable. These materials are also suitable as materials for the “original protective substrate (protective substrate)”.
[0028]
  The “organic material film” can be appropriately used as long as it is transparent to the wavelength used by the diffractive optical element.
  Claim 4As the “organic birefringent film”, a polymer birefringent film in which molecular chains are oriented can be used.
[0029]
As such a “polymer birefringent film”, considering ease of handling and cost, polyethylene terephthalate (PET), polycarbonate (PC), polyvinyl alcohol (PVA), polymethyl methacrylate (PMMA), polystyrene Polymer birefringent films such as polysulfone (PSF), polyethersulfone (PES), and polyimide are preferable.
Among these, polyethylene terephthalate (PET) is preferred from the viewpoint of uniform thinning, heat resistance, and chemical resistance.
[0030]
  The “polymer birefringent film” made of a polymer film in which molecular chains are oriented is particularly preferably “a polymer film in which molecular chains are oriented by stretching” in consideration of productivity.
  “An antireflection film is formed on a transparent substrate to which an organic material film is bonded” of a diffractive optical elementbe able to.
[0031]
Here, a manufacturing process of the diffractive optical element will be briefly described with reference to FIG.
FIG. 3A shows a state in which the original organic material film 102 is adhered to the original transparent substrate 10 by the adhesive layer 101. After forming a plurality of photoresist periodic patterns on the raw organic material film 102 by photolithography, an Al film is formed thereon by a vacuum deposition method, and a mask pattern MK made of Al is formed using a lift-off method. The formed state is shown in FIG. As a material for the mask pattern MK, other metals such as Cr and Ni can be used in addition to the above Al.
[0032]
Using the mask pattern MK as a mask, dry etching is performed, and further, Al constituting the mask pattern is removed, and a plurality of diffraction gratings 11B with unevenness are formed on the original organic material film 102. 3 (c) shows a state formed in such a manner.
[0033]
In FIG. 3 (d), an overcoat layer 103 is formed on a raw organic material film 102 in which a plurality of diffraction gratings 11B are formed in a grid arrangement, and an original protective substrate 104 is further provided on the overcoat layer 103. An integrated state is shown. The material of the overcoat layer is also filled in the “concave and concave portions” in each diffraction grating 11B.
[0034]
With respect to the state of FIG. 3D, a dicing apparatus (not shown) cuts along the cut surface CS shown in FIG. 3E to separate into a large number of diffractive optical elements.
[0035]
FIG. 4 shows a grid-like arrangement of a plurality of diffraction gratings 11 </ b> B formed on the original transparent substrate 10. The cutting by the dicing apparatus is performed so as to separate the individual diffraction gratings 11B “arranged in a lattice” as shown in FIG.
[0036]
Cutting by the dicing apparatus is performed by rotating a disk-shaped blade.
“Blade” is composed of abrasive diamonds such as artificial diamonds and binders, such as resin blades sintered using phenolic resin as the binder, and metal blades fired using metal powder as the binder. It has been. Resin-based blades generally have a coarse abrasive grain size and are effective for thick “cutting objects”. The metal blade has a fine abrasive grain size, is effective in reducing chipping (chips) generated on the cut surface, and the blade has rigidity, so that high-speed dicing is possible.
[0037]
In general, the size of chipping generated when cutting with a blade is large when the blade has a “abrasive grain size” and small when “abrasive grain size is fine”. However, if the abrasive grain size is small, “clogging due to shavings of the object to be cut” occurs between the abrasive grains, and seizure or the like tends to occur.
[0038]
In cutting when separating the diffraction grating 11B, the object to be cut has a five-layer structure of the original transparent substrate 10, the adhesive layer 101, the organic material film 102, the overcoat layer 103, and the original protective substrate 104. The width is narrow and chipping control is difficult. In the case of such an object to be cut, chipping occurs because the original transparent substrate 10 at the boundary between the adhesive layer 101 and the original transparent substrate 10 and the original protective substrate 104 at the boundary between the overcoat layer 103 and the original protective substrate 104. It is.
[0039]
FIG. 2 shows a state in which chipping has occurred in these portions.
FIG. 2 shows a state in the vicinity of the “cut plane” of one diffractive optical element separated by the dicing apparatus.
[0040]
Reference numeral 10 denotes a “transparent substrate”, 101 denotes an “adhesive layer”, 102 denotes an “organic material film”, 103 denotes an “overcoat layer”, and 104 denotes a “protective substrate”. That is, the original transparent substrate, the original organic material film, and the original protective substrate are cut by cutting with the dicing apparatus, and the transparent substrate 10, the organic material film 102, and the protective substrate 104 in each diffractive optical element are formed.
[0041]
The portions indicated by the symbols TP1 and TP2 are “chipping”. The chipping TP1 is the chipping generated in the protective substrate 104 at “the boundary between the overcoat layer 103 and the protective substrate 104”, and the chipping TP2 is generated in the transparent substrate 10 at “the boundary between the transparent substrate 10 and the adhesive layer 101”. Chipping.
[0042]
Chipping generally occurs such that the cross-section becomes “wedge” as shown. Taking the case of the chipping TP2 as an example, the size of chipping will be described. For the chipping TP2, “size in the thickness direction: TV” and “size in the plane direction: TH” of the transparent substrate 10 are considered.
[0043]
At this time, the so-called “chipping size” in the present invention refers to the larger one of the above-mentioned sizes: TV and TH. The “chipping size of 100 μm or less” in the case of claim 1 means that the larger of TV and TH is 100 μm or less.
[0044]
When chipping becomes large, causes such as “peeling” at the boundary between the transparent substrate 10 and the adhesive layer 101, the boundary between the overcoat layer 103 and the protective substrate 104, and “cracking” of the transparent substrate 10 and the protective substrate 104 are caused. Therefore, the reliability of the polarization diffractive element is greatly reduced, and the handling of the diffractive optical element when it is assembled to an optical device is also caused.
[0045]
The inventors have repeated research on chipping reduction. The degree (size and frequency) of chipping depends on the relationship between the thickness of the adhesive layer and the thickness of the overcoat layer, and the thickness of the adhesive layer: TS The thickness of the overcoat layer: It was found that when the TO is substantially equal, the frequency of chipping is reduced and the size of the chipping can be reduced (100 μm or less).
[0046]
  That is, to summarize the above description with reference to FIGS. 2 to 4, the diffractive optical element manufacturing method of the present invention adheres and fixes the original organic material film 102 on the original transparent substrate 10 via the adhesive layer 101. Then, a plurality of concave and convex diffraction gratings 11B are formed in a lattice array on the surface of the original organic material film 102 opposite to the adhesive layer 101, and the overcoat layer 103 is formed on the formed diffraction array 11B. And a transparent original protective substrate 104 is fixed to the overcoat layer 103 to obtain a lattice arrangement (FIG. 4) of the diffractive optical elements 11B, and a plurality of diffractive optical elements are individually separated by a dicing apparatus (FIG. 3). (E)) In the diffractive optical element manufacturing method, the thickness: TS of the adhesive layer 101 for adhering and fixing the original organic material film 102 on the original transparent substrate 10 is substantially equal to the thickness TO of the overcoat layer 103.In addition, the adhesive layer and the overcoat layer are made of the same material.
[0047]
  Further, according to the knowledge obtained by the inventors, the thickness of the adhesive layer: TS and the thickness of the overcoat layer: TO (≈TS) can be reduced by making them thinner than the thickness of the organic material film. The positional fluctuation of the height can be reduced, and the frequency and size of chipping can be reduced.(Claim 2),Effective for eliminating chipping.
[0048]
DETAILED DESCRIPTION OF THE INVENTION
  FIG.One form of diffractive optical element manufactured by the manufacturing method of the present inventionIs schematically depicted. In order to avoid complications, the same reference numerals as those in FIGS. 2, 3, and 4 are used in FIG.
[0049]
  That is, the diffractive optical element is an organic material film in which a transparent substrate 10 and an adhesive layer 101 are bonded and fixed on the transparent substrate 10 and an uneven diffraction grating 11B is formed on the surface opposite to the adhesive layer 101. 102, an overcoat layer 103 provided on the surface of the organic material film 102 on which the diffraction grating 11B is formed, and a transparent protective substrate 104 fixed on the overcoat layer 103. The thickness of the adhesive layer: TS and the thickness of the overcoat layer: TO are substantially equal, and the chipping of the peripheral surface portion (cut surface portion) of the transparent substrate 10 and / or the protective substrate 104 is 100 μm or less.It is.FIG. 1 shows a case where there is no chipping.
[0050]
【Example】
Hereinafter, two examples and two comparative examples for each example are shown.
[0051]
Example 1
A circular original transparent substrate having a thickness of 1.0 mm and a diameter of φ = 100 mm is provided with an adhesive layer having a thickness of 100 μm using an acrylic UV curable adhesive, and a thick original organic material film is formed thereon. Length: A 100 μm organic “polymer birefringent film” is bonded together, and the adhesive layer and the polymer birefringent film are integrated under reduced pressure, followed by UV irradiation and baking at 100 ° C. for 10 minutes. The adhesive layer was completely cured (the state shown in FIG. 3A).
[0052]
Next, a plurality of periodic patterns (pitch: 3.0 μm) made of a metal (Al) film were formed on the polymer birefringent film (state shown in FIG. 3B).
After the original organic material film (polymer birefringent film) is dry-etched using the periodic pattern as a mask, the metal film mask is removed, and "diffractive gratings with irregularities" are arranged in a grid pattern on the organic polymer birefringent film (The state of FIG. 3C and FIG. 4).
[0053]
The cross-sectional shape of “unevenness constituting each diffraction grating” is “substantially rectangular” as shown in FIG.
[0054]
A spacer having a thickness of 100 μm is disposed on a raw organic material film formed by arranging a plurality of diffraction gratings in a lattice pattern, and an “acrylic UV curable resin” serving as an overcoat layer is botted. From the top: 1.0 mm thick original protective substrate (same size and same shape as the original transparent substrate) is put on and pressed appropriately, and the overcoating agent is filled in the concavo-convex grating. Thickness: 100 μm (diffractive grating An overcoat layer (thickness not adding the depth of unevenness) was formed, and after being irradiated with ultraviolet rays, it was baked at 100 ° C. for 10 minutes to be completely cured (state of FIG. 3D).
[0055]
A chip having a size of 0.15 mm and an outer diameter of 60 mm is used as a cutting target, and a dicing apparatus using a “resin-based blade” having a thickness of 0.15 mm and a chip having a size of “5.0 mm × 5.0 mm” as a whole. ”And separated into“ diffractive optical elements ”as shown in FIG. 1 to produce a plurality (120 pieces). The “blade wear amount” at this time was 50 μm.
[0056]
Comparative Example 1
In Example 1, a plurality of (120) diffractive optical elements were prepared in the same manner as in Example 1 except that the thickness of the adhesive layer made of an acrylic ultraviolet curable adhesive was 50 μm. The “blade wear amount” at this time was 45 μm.
[0057]
Comparative Example 2
In Example 1, the thickness of the adhesive layer made of an acrylic UV curable adhesive is 20 μm, the thickness of the organic material film (polymer birefringent film) is 80 μm, and the others are the same as in Example 1, and a plurality of them are used. The diffractive optical element was prepared. The “blade wear amount” at this time was 45 μm.
[0058]

[0059]
That is, it was found that by making the thickness of the adhesive layer: TS and the thickness of the overcoat layer: TO equal, the chipping size becomes 100 μm or less (evaluation “◯”).
[0060]
Example 2
A circular original transparent substrate having a thickness of 1.0 mm and a diameter of φ = 100 mm is provided with an adhesive layer having a thickness of 40 μm using an epoxy-based ultraviolet curable adhesive, and the thickness of the original organic material film is 80 μm. The organic polymer birefringent film was bonded and integrated under reduced pressure, and then irradiated with ultraviolet rays, and baked at 100 ° C. for 10 minutes to completely cure the adhesive layer (FIG. 3A). State).
[0061]
Next, a plurality of periodic patterns (pitch: 3.0 μm) made of a metal (Al) film were formed on the raw organic material film in a lattice arrangement (state shown in FIG. 3B). Using this periodic pattern as a mask, the organic material film is dry-etched, and the metal mask is removed to form a plurality of “diffractive gratings with unevenness” on the surface of the organic material film in a lattice arrangement (FIG. 3C). The state of FIG. The cross-sectional shape of “unevenness constituting each diffraction grating” is “substantially rectangular” as shown in FIG.
[0062]
On the original organic material film in which a plurality of diffraction gratings are formed in a grid arrangement, a spacer of 40 μm thickness is placed, and “epoxy UV curable resin” that becomes an overcoat layer is botted. Thickness: 1.0mm on the original protective substrate, pressurize moderately, fill the concave / convex grating with overcoat agent, and thickness: 40μm (thickness without adding the concave / convex depth of the diffraction grating) A coat layer was formed and irradiated with ultraviolet light, and then baked at 100 ° C. for 10 minutes to be completely cured (state shown in FIG. 3D).
[0063]
Thereafter, using a “resin blade” having a thickness of 0.20 mm and an outer diameter of 60 mm, the whole is cut into “5.0 mm × 5.0 mm size chips” and separated by a dicing apparatus, and a diffractive optical element A plurality of (120) were prepared. The “blade wear amount” at this time was 40 μm.
[0064]
Comparative Example 3
In Example 2, the thickness of the adhesive layer using the epoxy-based UV curable adhesive is 120 μm, the thickness of the organic material film (organic polymer birefringent film) is 80 μm, and the thickness of the overcoat layer is 120 μm. It was.
[0065]
Cutting with a dicing machine uses a disk-shaped “resin-based blade” having a thickness of 0.20 mm and an outer diameter of 60 mm, and the whole is cut into “5.0 mm × 5.0 mm size chips” and diffracted. A plurality of (120) optical elements were produced. The amount of blade wear at this time was 200 μm.
[0066]
Comparative Example 4
In Example 2, the thickness of the adhesive layer made of an epoxy UV curable adhesive was 100 μm, the acrylic UV curable resin was used as the material of the overcoat layer, and the thickness of the overcoat layer was 100 μm. Using a disk-shaped “resin-based blade” having a thickness of 0.15 mm and an outer diameter of 60 mm, the whole is cut into “5.0 mm × 5.0 mm size chips” and a plurality of polarization diffraction elements (120 Manufactured). The blade wear amount at this time was 50 μm.
[0067]

[0068]
  That is, in the diffractive optical elements of Examples 1 and 2, the original organic material film is bonded and fixed on the original transparent substrate via the adhesive layer, and the surface of the original organic material film opposite to the adhesive layer is diffracted by unevenness. A plurality of gratings are formed in a grating array, an overcoat layer is formed on the formed grating array diffraction grating, and a transparent original protective substrate is fixed to the overcoat layer to form a grating array of diffractive optical elements. In the diffractive optical element manufacturing method in which a plurality of diffractive optical elements are individually separated by a dicing apparatus, the thickness of the adhesive layer for adhering and fixing the original organic material film on the original transparent substrate: TS and the overcoat layer Thickness: diffractive optical element that makes TO substantially equalManufactured by manufacturing methodIt has been done.
[0069]
  In addition, the diffractive optical elements of Examples 1 and 2 are an organic material film in which a transparent substrate and an adhesive layer are bonded and fixed to the transparent substrate via an adhesive layer, and a diffraction grating with unevenness is formed on the surface opposite to the adhesive layer. And an overcoat layer provided on the surface of the organic material film on which the diffraction grating is formed, and a transparent protective substrate fixed on the overcoat layer. And the thickness of the overcoat layer is substantially equal, and the chipping of the peripheral surface portion of the transparent substrate and / or the protective substrate is 100 μm or less.is there.
  The organic material film is an organic birefringent film, and the overcoat layer is an isotropic optical material having a refractive index substantially equal to the refractive index of the organic birefringent film with respect to the ordinary ray or the extraordinary ray. (Claim 4).
[0070]
  In Example 2, the thickness of the adhesive layer and the overcoat layer (40 μm) is thinner than the thickness of the original organic material film (80 μm) (Claim 2In both Examples 1 and 2, the adhesive layer and the overcoat layer are formed of the same material (Claim 1), The adhesive layer and the overcoat layer are formed of an acrylic material in Example 1, and an epoxy material in Example 2 (Claim 3).
[0071]
  The diffractive optical element of Comparative Example 3 is good in terms of chipping size, but the blade wear when separating the elements is as large as 200 μm, and this method eventually increases the manufacturing cost (therefore, the evaluation “Δ”). ) In the diffractive optical element of Comparative Example 4, the thickness of the adhesive layer: TS is equal to the thickness of the overcoat layer: TO, but the chipping is as large as 150 μm. This can be attributed to the fact that the adhesive layer (epoxy) and overcoat layer (acrylic) materials were not the same. From this point, the adhesive layer and the overcoat layer must be the same material. (Claim 1) Is preferred.
[0072]
In Examples 1, 2 and Comparative Examples 1, 2, 3, and 4, the transparent substrate and the protective substrate are made of BK-7 glass, and the polymer birefringent film as the organic material film is polyethylene terephthalate (PET). It is. In addition, as for the UV curable resin used for the adhesive layer and the overcoat layer, the acrylic type is TB3042, and the epoxy type is TB3121.
[0073]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the optical pickup device will be described with reference to FIG.
The optical pickup device condenses the light emitted from the light source 30 as a light spot on the recording surface of the optical disc 40 by the objective lens 37, and returns the returned light beam reflected by the recording surface via the objective lens 37 to the light detection unit. The optical pickup device performs one or more of recording / reproducing / erasing information with respect to the optical disc 40 while being guided to 39, and the diffractive optical element 31 is disposed between the light source 30 and the objective lens 37. The diffractive optical element 31 is as shown in FIG.
[0074]
In the optical pickup device of FIG. 5, light from the semiconductor laser that is the light source 30 passes through the diffractive optical element 31. The diffractive optical element 31 is an organic birefringent film whose organic material film is used as a “polarization hologram element”.
[0075]
The organic birefringent film and the overcoat layer have substantially the same refractive index with respect to ordinary light, and the light from the light source side passes through the diffractive optical element 31 as it is without being diffracted. 35, and is condensed as a light spot on the recording surface of the optical disc 40 by the action of the objective lens 37.
[0076]
The light reflected by the recording surface becomes a “returning light beam” that passes through the objective lens 37 and the quarter-wave plate 35, becomes linearly polarized light whose polarization surface is rotated 90 degrees from the original direction, and enters the diffractive optical element 31. To do. Since the organic birefringent film and the overcoat layer have different refractive indexes with respect to extraordinary rays, the return light beam is subjected to diffracting action by the diffractive optical element 31 as extraordinary rays (becomes first-order diffracted light) toward the light detection unit 39. Deflected. At this time, for example, astigmatism is given to the return light beam by the diffractive optical element 31, and this light beam is received by the light detection unit 39, and a focusing signal by the astigmatism method, a tracking signal by the push-pull method, and a reproduction signal are obtained. generate. Since the output of the light detection unit 39 carries information corresponding to the information recorded on the optical recording medium, image information, audio information, etc. can be reproduced by performing necessary processing thereafter.
[0077]
  That is, the optical pickup device of FIG.A diffractive optical element manufactured by the method according to claim 4.The polarization hologram element 31 is used to separate the optical path of the light beam from the light source 30 side and the optical path of the return light beam from the optical disk 40.Is.
[0078]
FIG. 6 is a diagram showing an embodiment of the optical disk drive device.
This optical disk drive apparatus is an apparatus that performs one or more of recording / reproducing / erasing information with respect to the optical disk 40 by using an optical pickup device 41.
[0079]
The optical disc 40 is held by a holding unit 47 and is rotationally driven by a motor Mt as “driving means”. The optical pickup device 41 is displaced in the radial direction of the optical disc 40 by the displacement driving means 43 with respect to the set optical disc 40 to perform one or more of recording / reproducing / erasing. The control unit 42 controls various controls based on the signal from the optical pickup device 41 and the output of the reproduction signal, and also controls the entire device.
[0080]
  That is, the optical disk drive apparatus of FIG. 6 is an optical pickup apparatus that performs one or more of recording / reproducing / erasing information with respect to the optical disk 40 using the optical pickup apparatus 41.What is shown is used.
[0081]
As the polarization hologram element 31 in the optical pickup device shown in FIG. 5, the diffractive optical elements of Embodiments 1 and 2 can be used, and this optical pickup device can be used in the optical disk drive device of FIG.
[0082]
A diffractive optical element having a diffraction grating on an organic birefringent film can be made smaller than the conventional “beam splitter with a prism attached”, so that the optical pickup device can be realized in a compact manner, and the optical disk drive device can be made smaller and lighter. Is possible.
[0083]
【The invention's effect】
  As explained above, according to the present invention,New “Diffraction optical element manufacturing method”realizable.
[0084]
  Of this inventionManufactured by the methodThe diffractive optical element can be easily held and handled (handled) easily and reliably because chipping is small, and there is little “blurring of the outline of the diffractive optical element image” on the monitor during assembly. Therefore, highly accurate alignment can be easily realized, and by using this, the optical pickup device and the optical disk drive of the present invention can be realized at low cost.
[0085]
  Also, the method for producing a diffractive optical element of the present inventionIs the aboveA diffractive optical element can be manufactured at a low cost with a high yield.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining an embodiment of a diffractive optical element.
FIG. 2 is a diagram for explaining chipping in a diffractive optical element.
FIG. 3 is a diagram for explaining a manufacturing process of the diffractive optical element.
FIG. 4 is a diagram schematically showing a lattice arrangement of a plurality of diffraction gratings formed on an original organic material film on an original transparent substrate.
FIG. 5 is a diagram for explaining the first embodiment of the optical pickup device;
FIG. 6 is a diagram for explaining one embodiment of an optical disk drive device.
[Explanation of symbols]
10 Transparent substrate
101 Adhesive layer
102 Organic material film
103 Overcoat layer
104 Protective board
TS Adhesive layer 101 thickness
TO Overcoat layer 103 thickness

Claims (4)

Adhering and fixing the original organic material film on the original transparent substrate via an adhesive layer, forming a plurality of concave and convex diffraction gratings in a grid array on the surface opposite to the adhesive layer of the original organic material film An overcoat layer is formed on the diffraction grating having the grating arrangement and a transparent original protective substrate is fixed to the overcoat layer to obtain a grating arrangement of the diffractive optical elements, and the plurality of diffractive optical elements are obtained by a dicing apparatus. In a diffractive optical element manufacturing method for individually separating
  The thickness of the adhesive layer for adhering and fixing the original organic material film on the original transparent substrate: TS and the thickness of the overcoat layer: TO are substantially equal, and the adhesive layer and the overcoat layer are formed of the same material. A method for producing a diffractive optical element. In the diffractive optical element manufacturing method according to claim 1,
  A method for producing a diffractive optical element, characterized in that the thickness of the adhesive layer and the overcoat layer is made thinner than the thickness of the original organic material film. In the diffractive optical element manufacturing method according to claim 1 or 2,
A method for producing a diffractive optical element, wherein the adhesive layer and the overcoat layer are formed of an acrylic or epoxy material . In the diffractive optical element manufacturing method according to any one of claims 1 to 3,
  An organic birefringent film is used as the organic material film, and an isotropic optical material having a refractive index substantially equal to the refractive index for ordinary light or extraordinary light of the organic birefringent film is used as the overcoat layer. A method for producing a diffractive optical element.

Images