1377372 九、發明說明： 【發明所屬之技術領域】 本發明涉及一種在基板的一面形成光學膜時將對基板 產生作用的光學膜的應力緩和而使光學膜形成後的面平面 5 化的光學元件、緩和膜應力而使基板的表面平面化的光學 膜平面化方法及上述的光學元件的製造方法。 【先前技術】 液BB投影機或光讀取器等光學裝置由各種光學元件構 ,10成，光學元件通常在玻璃材料等透明基板的一面形成有光 學膜。作爲光學膜，有介電單層膜或介電多層膜、金屬膜 等各種光學膜，但是，這些光學膜因具有内部應力（膜應 力）所以在透過蒸鍍法等形成在透明基板之後，由於膜應 力而使透明基板整體發生變形。其結果，光學膜的性能劣 15 化或損失。 4卞不的九学裝置對小型化的要求極高，因此， 要求透明基板的板厚度的薄φ 又幻，寻型化。攻樣，相應的由膜應力 :與透明基板的影響就變得顯著。因此，有必要：不僅⑴ 滿足板厚度的薄型化的要求、 的變形進行修正。以並且⑴對透明基板的形狀 作爲同時滿足上述^ 如在透明基板的形成H (2)的要求的方法，有例 學膜的膜廡予膜的相反面，形成用於修正光 的方法。該方法在專利前幸丨的膜（作爲修正用薄膜） 〃破么開，在光學元件的非光學 20 功能面（背面）形成具有内部應力的薄膜，利用薄膜的内 部應力（膜應力）的作用使光學元件產生變形’由此對光 學元件的光學功能的形狀進行修正。即，在基板的二面形 成了光學膜的相反面、形成修正膜應力的作用的薄膜來 謀求元件整體形狀的修正》 【專利前案1】專利公開2005-19485號公報。 【發明内容】 然而，在專利前案1中，有必要在基板（非光學功能面） 形成基板形狀修正用薄膜，但通常，爲了獲得所希望的薄 膜就需要精密的控制。另一方面，基板需要設爲薄型，而 對於薄的基板而言’光學膜的膜應力所引起的變形程度 大，但同時修正用薄膜的膜應力也強力地起作用。這樣進 行的話’爲了對光學膜的膜應力正確且高精度地進行修 正’薄膜的形成精度就必須極精密地進行控制，由此是極 爲困難的。 而且，修正用薄膜，基本只發揮修正基板形狀的功能， 不發揮其他光學性功能。這樣的薄膜，由於從光學性功能 面考慮爲不必要的要素，因此成爲剩餘成本。而且，由於 =4膜的形成比較費時間，由此當該步驟費時間時就導致生 産效率下降的問題。進一步而言，由於本來不需要的修正 用薄膜形成於薄型的基板，因此，在抗應力性方面也存在 問題。 於是’在本發明中，其目的在於，修正用薄膜不用形 成而透過緩和光學膜的膜應力來謀求光學膜的平面化。 1377372 爲了達成以上目的’本發明的技術方案1的光學元件， 其中’在基板的表面和背面使面粗度具有差別，在上述表 面或上述背面中的粗度細的面形成光學膜，緩和上述光學 膜的應力。 5 在基板特別薄型的情況下，當在基板的表面和背面之 間使面粗度有差別時’具有産生向基板的粗面方向凸出的 歪曲的效應（所謂泰曼效應）^另一方面，在光學膜存在 產生向基板的成膜面方向凸出的歪曲的膜應力。因此，在 粗度細的面形成光學膜的情況下，由於膜應力的作用所引 10 起的歪曲方向和上述的泰曼效應所引起的歪曲方向成爲相 互逆反的凸方向的關係’因此，相互的應力可互相抵消。 若這樣進行的話，能夠將基板整體的形狀進行修正，從而 將光學膜平面化》 在此，光學膜若在誤差容許範圍内，則也可不被完全 15 地平面化。即’雖然在毛面（摺面）被形成的情況下光學 膜的膜應力被抵消並提高平面化的程度，但若在發揮光學 性功能的誤差容許範圍内’則也可不被完全地平面化，也 可以爲微小弯曲的狀態。 本發明的技術方案2的光學元件，是技術方案丨所述的 20 光學元件，其中，上述粗度細的面透過鏡面研磨完成爲成 膜面，與該成膜面相反的面形成爲毛面。 透過進行鏡面研磨來形成成膜面而將相反面形成爲毛 面’可以使面的粗度具有差別。在此，毛面的形成是指利 用粒度粗的研磨劑對基板的一面進行打磨，毛面是指進行 7 1377372 了毛面开/成的面作爲進行毛面形成的方法（毛面的形成 方法）也能夠適用：使用了其他研削劑的研削處理或由將 研磨劑喷在基板表面的喷砂或由鑽石進行的切削'砂紙、 刷洗（Pushing)等各種方法。換言之，毛面的形成是指在 5基板表面形成微小的傷痕即形成微小的凹凸，是指在面上 形成毛面。 另一方面，鏡面研磨是將基板表面完成爲鏡面（去除 基板表面上的凹凸），可以適用所謂研磨處理（1邛 ® treatment )或壓光處理（burnishing treatment )、拋光 10 (P〇lishing treatment)處理等方法。在上述的毛面形成中 使用研磨劑的情況爲毛面研磨，但是，毛面研磨和鏡面研 磨使用研磨這—相同用語。然而，毛面研磨是在基板表面 形成微小凹凸的方法，鏡面研磨是消除基板表面的微小凹 凸的方法，在這-；$·面，二者在用途和功能上都相反。 15 形成毛面之前的面（被磨面（被摺面））雖然沒有必 要預先完成鏡面，但被磨面也好，形成光學膜的面（被成 φ 膜面）也好，在以平面狀態爲基準來控制彎曲量這一點上， 作爲較佳將被磨面與被成膜面同樣地完成鏡面。即，較佳 預先使彎曲量的基準一致。 20 而且，基本上基板的形狀爲平板狀，但也可以爲平板 狀以外的形狀。從毛面抵消光學膜的膜應力來看，若被磨 • 面和被成膜面平行，則不僅適用於四角形的平板狀，也可 以適用於圓形、三角形等任意板狀的基板。在此，成膜面 爲了發揮規定的光學性功能必須提高平面化的程度，但由 8 於相反面的毛面基本不發揮光學性功能，因此，其形狀可 以任意設置。從而，在抵消光學膜的膜應力且將光學膜平 面化的前提下，毛面即使不是平面也可以爲多少變異的異 形。 ' 本發明的技術方案3的光學元件，是技術方案2所述的 光學元件，其中，上述毛面用使上述光學膜平面化的粒度 進行打磨。若形成被磨面則可以緩和膜應力，但透過用最 適宜的粒度形成毛面’可以使光學膜接近平面化。毛面形 成時的粒度’若粗則應力的作用大，若細則應力的作用小。 因此，若選擇與光學膜的膜應力對應的最適宜的粒度，則 可以接近平面化。 本發明的技術方案4的光學元件，是技術方案！至3中任 一項所述的光學元件，其中，上述光學膜是對規定波長域 的光進行反射的反射多層膜。基本上，由於毛面爲沒有光 學性使用的面，因此，在各種光學元件中，最能適用於本 發明的光學元件爲反射鏡。 作爲反射鏡起作用時，不是介電多層膜也可以是基於 金屬膜的反射多層膜。然而，金屬膜雖然使所有的波長域 的光反射，但由於光吸收率高，因此反射效率有些下降。 從而’從抑制光量損失觀點來看較佳適用基於介電多層膜 的反射多層膜《金屬膜可以是單層膜，但基於介電多層膜 的反射多層膜’爲了在所希望的波長域獲得極高的反射 率，就需要較多的膜層數。若這樣，由於對基板的膜應力 變強，因此，在基於介電多層膜的反射多層膜的情況，起 1377372 到特別有利的效果β 而且’在毛面可以使用於其他用途的情況下，也可以 作爲反射鏡以外的光學元件適用本發明。由於在毛面形成 有微小凹凸’因此’透過使光透過毛面，可以利用光的散 5 射來謀求光分佈的均一化。而且，也可以作爲利用散射光 對光的強度進行測定的、例如APC ( Auto Power Control) 使用。在此種情況下，可以不將光學膜形成爲反射多層膜 而形成爲例如具有使規定條件的光透過的透過特性的膜而 • 適用。 10 本發明的技術方案5的光學膜平面化方法，其中，包 括：鏡面研磨步驟’對基板的至少一面進行鏡面研磨；毛 面形成步驟，透過對鏡面研磨的一面的相反面進行打磨來 形成毛面；光學膜形成步驟，在上述毛面形成步驟後進行， 在上述鏡面研磨後的一面形成光學膜，透過由上述毛面緩 15 和上述光學膜對上述基板的應力，使上述光學膜平面化。 本發明的技術方案6的光學膜平面化方法，其中，包 % 括.鏡面研磨步驟，對基板的至少一面進行鏡面研磨；光 學膜形成步驟，在鏡面研磨後的一面形成光學膜；毛面形 成步驟，在上述光學膜形成步驟之後進行，透過對上述形 20 成有光學膜的面的相反面進行打磨來形成毛面，透過由上 述毛面緩和上述光學膜對上述基板的應力，使上述光學膜 ' 平面化。 ”技術方案5的光學膜平面化方法和技術方案6的光學膜 平面化方法，在透過形成毛面而抵消光學膜的膜應力並謀 10 1377372 求光學膜的平面化這一方面是一致的，但是在技術方案5的 光學膜平面化方法中，毛面的形成步驟比光學膜形成步驟 先進行（先打磨），技術方案6的光學膜平面化方法中，毛 面的形成步驟比光學膜形成步驟後進行（後打磨），這一 5 方面上是不同的。 在先打磨的情況下，用與預先形成光學膜時的基板的 彎曲量對應的粒度形成被磨面。即，預計基於膜應力的基 板的彎曲量，並將該量份由毛面的形成所引起的應力事先 進行緩和。此時，由於可以用均一的粒度事先形成毛面， 10 因此，適合於大量生産。 另一方面，在後打磨的情況下’在基板形成光學膜時， 基板透過光學膜的應力而向光學膜侧的凸方向弯曲。而 且，根據基板的彎曲狀態’可以形成用於事後一起進行補 正的毛面。因此，可以根據各自的基板的彎曲程度，精細 15 地謀求光學膜的平面化。 在此，在先打磨的情況下當形成毛面時，在後打磨的 情況下當形成光學膜時，基板透過基於泰曼效應的應力或 光學膜的膜應力而彎曲。此時，在基板沒有固定的狀態下， 透過基於泰曼效應的應力和光學膜的膜應力使基板向一方 2〇 向彎曲。因此，使用粘接劑等，預先使基板固定於維持平 面狀態的固定夾具等，強制性地使基板維持平面狀態。透 過光學膜的形成或毛面的形成在該狀態下進行，就可以正 破地進行。 而且’本發明的技術方案7的光學膜平面化方法，是技 11 術方案5或6所述的光學膜平面化方法，其中，在形成上述 =面時，用使上述基板平面化的粒度進行打磨。若用最適 宜的粒度形成毛面，則可以使光學膜接近平面。 本發明的技術方案8的光學膜平面化方法，是如技術方 案7所述的光學臈平面化方法，其中，還包括··微調整步驟， 其透過用比在上述毛面形成步驟中形成毛面的粒度更粗的 粒度或更細的粒度對上述毛面進行打磨，進行使上述成膜 面更靠近平面的微調整。 在形成毛面後再次對毛面進行打磨的情況下，當用比 形成毛面時的粒度更粗的粒度進行研磨時，緩和膜應力的 應力起作用，當用細粒度進行研磨時，用於對基於泰曼效 應的應力進行緩和的應力起作用。即，當用較粗的粒度再 次研磨毛面時，使向毛面方向凸出的歪曲的應力起作用， 當用較細的粒度再次研磨毛面時，使向成膜面方向凸出的 正曲的應力起作用。因此’在後打磨的情況下當向成膜面 的方向凸出的歪曲依然發生時’以較粗的粒度再次研磨毛 面’使基於泰曼效應的應力起作用來謀求光學膜的平面化。 另一方面’在由毛面的形成所引起的應力超出膜應力 而產生向粗面（成膜面的相反面）凸出的歪曲時，以較細 的粒度再次研磨毛面’減輕由毛面的形成所引起的應力， 謀求光學膜的平面化。在由毛面的形成所引起的應力不足 或過剩地起作用時，在形成毛面之後，透過再次用粗粒度 或細粒度研磨毛面，可以進行細緻的微調整的補正，可以 謀求光學膜的平面化。即，所謂在毛面形成後用粗粒度或 1377372 細粒度研磨毛面，就是對應力的過度和不足份進行微調整 且進行補正。 而且’本發明的技術方案9至12的光學元件的製造方 法，其中，使用上述的光學膜平面化方法，製造上述的光 5 學元件。 作爲基板的材料，主要以透明性的玻璃材料爲物件， 但也可以使用透明性的塑膠材料。而且’作爲反射鏡使用 時，由於基板内部沒有光透過，因此，也可以使用非透明 性的材料。 10 作爲光學膜，可以使用由多層介電膜構成的介電多層 膜、由單層的介電膜構成的介電單層膜、金屬膜等。其中， 介電多層臈待別是膜層數多的介電多層膜其膜應力變強， 因此，本發明對於這樣的介電多層膜尤其奏效。 作爲在基板形成光學膜的方法，可以使用真空蒸鍍 15 法、離子鍍法、離子輔助法、濺射法、CVD (化學氣相沈 積法）、喷鍍、打磨等各種手法。 將本發明的光學元件作爲反射鏡使用時，作爲將該光 學元件作爲構成部件的光學裝置，可以使用例如光學讀取 器或液晶投影機（投射型顯示裝置）等。 20 本發明透過在形成有光學膜的面的相反面形成毛面， 由毛面的形成所引起的應力將光學膜的膜應力抵消，即便 特別的修正用薄膜不形成’也可以謀求光學膜的平面化。 尤其’當基板薄時，具有膜應力變強的傾向，使光學膜歪 曲得大’但是，由於即使膜應力變強而透過在相反面形成[Technical Field] The present invention relates to an optical element in which the stress of the optical film which acts on the substrate is relaxed when the optical film is formed on one surface of the substrate, and the plane of the surface after the formation of the optical film is reduced. An optical film planarization method for relaxing a film stress to planarize a surface of a substrate, and a method for producing the optical element described above. [Prior Art] An optical device such as a liquid BB projector or an optical reader is composed of a plurality of optical elements, and an optical element is usually formed on one surface of a transparent substrate such as a glass material. The optical film includes various optical films such as a dielectric single layer film, a dielectric multilayer film, and a metal film. However, since these optical films have internal stress (film stress), they are formed on a transparent substrate by a vapor deposition method or the like, The film stress causes deformation of the entire transparent substrate. As a result, the performance of the optical film is inferior or lost. The ninth device of the 卞 卞 对 对 对 对 对 对 对 对 对 九 九 九 九 九 九 九 九 九 九 九 九 九 九 九 九 九 九 九The sample is correspondingly affected by the film stress: the effect with the transparent substrate becomes significant. Therefore, it is necessary to correct not only (1) the requirement for the thickness reduction of the plate thickness but also the deformation. Further, (1) The shape of the transparent substrate is a method for simultaneously satisfying the above-described requirements for forming H(2) on the transparent substrate, and a method for correcting light is formed on the opposite side of the film of the film. This method breaks through the patented film (as a film for correction) and forms a film with internal stress on the non-optical 20 functional surface (back surface) of the optical element, utilizing the internal stress (membrane stress) of the film. The optical element is deformed' thereby correcting the shape of the optical function of the optical element. In other words, a film having a function of correcting the film stress is formed on the opposite surface of the optical film on the opposite side of the substrate, and the entire shape of the element is corrected. [Patent Preamble 1] Patent Publication No. 2005-19485. SUMMARY OF THE INVENTION However, in Patent PRIOR ART 1, it is necessary to form a substrate shape correcting film on a substrate (non-optical functional surface). However, in general, precise control is required in order to obtain a desired film. On the other hand, the substrate needs to be thin, and the degree of deformation caused by the film stress of the optical film is large for a thin substrate, but the film stress of the film for correction also strongly acts. In this case, it is extremely difficult to accurately and accurately control the film stress of the optical film to accurately correct the film formation accuracy. Further, the film for correction basically functions only to correct the shape of the substrate, and does not exhibit other optical functions. Such a film is an unnecessary factor from the viewpoint of optical function, and therefore has a residual cost. Moreover, since the formation of the =4 film is relatively time consuming, the problem of a decrease in productivity is caused when this step takes time. Further, since the film for correction which is not originally required is formed on a thin substrate, there is a problem in terms of stress resistance. Thus, in the present invention, it is an object of the invention to reduce the film thickness of the optical film by the film for correction without forming it, thereby achieving planarization of the optical film. 1377372 In order to achieve the above object, the optical element according to the first aspect of the present invention, wherein the surface roughness is different between the surface and the back surface of the substrate, and an optical film is formed on the surface of the surface or the back surface having a small thickness, thereby alleviating the above. The stress of the optical film. 5 In the case where the substrate is particularly thin, when there is a difference in the surface roughness between the surface and the back surface of the substrate, 'there is an effect of causing distortion that is convex toward the rough surface of the substrate (so-called Taiman effect). There is a distorted film stress that is generated in the optical film to protrude toward the film formation surface of the substrate. Therefore, in the case where an optical film is formed on a thin surface, the warp direction caused by the action of the film stress and the warping direction caused by the above-mentioned Teman effect become a relationship of mutually opposite convex directions. The stresses can cancel each other out. By doing so, the shape of the entire substrate can be corrected to planarize the optical film. Here, if the optical film is within the tolerance of the error, it may not be completely planarized. That is, although the film stress of the optical film is canceled and the degree of planarization is increased when the matte surface (folded surface) is formed, it may not be completely planarized if it is within the tolerance of the optical function. It can also be in a slightly curved state. The optical element according to claim 2 is the 20th optical element according to the aspect of the invention, wherein the thin surface is formed into a film formation surface by mirror polishing, and a surface opposite to the film formation surface is formed into a matte surface. . By forming a film formation surface by mirror polishing and forming the opposite surface as a matte side, the thickness of the surface can be made different. Here, the formation of the matte surface means that one side of the substrate is polished by a coarse-grained abrasive, and the matte side refers to a method of performing a rough surface on the surface of 7 1377372 as a method of forming a matte surface (formation method of a matte surface) It is also applicable to various methods such as a grinding treatment using another grinding agent, or sandblasting by a polishing agent or a cutting by a diamond, sanding, and brushing. In other words, the formation of the matte surface means that minute flaws are formed on the surface of the substrate, i.e., minute irregularities are formed, and a matte surface is formed on the surface. On the other hand, mirror polishing is to complete the surface of the substrate as a mirror surface (removing the unevenness on the surface of the substrate), and it can be applied to a so-called "1" treatment or a burnishing treatment or a polishing treatment. Processing and other methods. In the case where the above-mentioned matte formation is used, the case of using an abrasive is a matte finish, but the matte finish and the mirror grind use the same term. However, matte grinding is a method of forming minute irregularities on the surface of the substrate, and mirror polishing is a method of eliminating minute concavities and convexities on the surface of the substrate, in which the two are opposite in use and function. 15 The surface before the formation of the matte surface (the surface to be grounded (folded surface)) Although it is not necessary to complete the mirror surface in advance, the surface to be polished is also good, and the surface on which the optical film is formed (formed as the φ film surface) is also in a planar state. In order to control the amount of bending for the reference, it is preferable to complete the mirror surface in the same manner as the film formation surface. That is, it is preferable to match the criteria of the amount of bending in advance. Further, the shape of the substrate is basically a flat plate shape, but may be a shape other than a flat plate shape. From the viewpoint of the film stress of the matte surface offset optical film, if the surface to be polished is parallel to the film formation surface, it is applicable not only to a square plate shape but also to any plate-shaped substrate such as a circular shape or a triangular shape. Here, the film formation surface must be flattened in order to exhibit a predetermined optical function. However, since the matte surface of the opposite surface does not substantially exhibit an optical function, the shape can be arbitrarily set. Therefore, under the premise of canceling the film stress of the optical film and planarizing the optical film, the embossed shape can be somewhat variated even if it is not a flat surface. The optical element according to claim 3 is the optical element according to claim 2, wherein the matte surface is polished with a particle size that planarizes the optical film. If the surface to be polished is formed, the film stress can be alleviated, but by forming the matte surface with the optimum particle size, the optical film can be made planar. When the matte surface is formed, the particle size is large, and if the thickness is large, the effect of the stress is large, and if the effect of the rule stress is small. Therefore, if the optimum particle size corresponding to the film stress of the optical film is selected, the planarization can be approached. The optical component of the fourth aspect of the present invention is a technical solution! The optical element according to any one of the preceding claims, wherein the optical film is a reflective multilayer film that reflects light in a predetermined wavelength range. Basically, since the matte side is a surface that is not optically used, among the various optical elements, the optical element most suitable for use in the present invention is a mirror. When acting as a mirror, it is not a dielectric multilayer film or a reflective film based on a metal film. However, although the metal film reflects light in all wavelength ranges, the reflection efficiency is somewhat lowered due to the high light absorption rate. Therefore, it is preferable to apply a reflective multilayer film based on a dielectric multilayer film from the viewpoint of suppressing the amount of light loss, "the metal film may be a single layer film, but a reflective multilayer film based on a dielectric multilayer film" in order to obtain a pole in a desired wavelength domain. High reflectivity requires more layers. In this case, since the film stress on the substrate becomes strong, in the case of the reflective multilayer film based on the dielectric multilayer film, from 1373372 to the particularly advantageous effect β and in the case where the matte side can be used for other purposes, The invention can be applied as an optical element other than a mirror. Since fine irregularities are formed on the rough surface, the light is transmitted through the matte surface, and the light distribution can be uniformized by the scattering of light. Further, it can also be used as, for example, APC (Auto Power Control) for measuring the intensity of light by using scattered light. In this case, the optical film may be formed into a film having a transmission characteristic of transmitting light of a predetermined condition without forming the reflective multilayer film. The optical film planarization method according to claim 5 of the present invention, comprising: a mirror polishing step 'mirror polishing at least one surface of the substrate; and a matte surface forming step of grinding the opposite surface of the mirror-polished surface to form a hair The optical film forming step is performed after the matte surface forming step, and an optical film is formed on one surface after the mirror polishing, and the optical film is flattened by the stress of the matte surface 15 and the optical film on the substrate. . An optical film planarization method according to a sixth aspect of the present invention, wherein the package comprises: a mirror polishing step of mirror-finishing at least one surface of the substrate; and an optical film forming step of forming an optical film on the mirror-polished surface; the matte surface is formed The step of performing the optical film forming step, grinding the opposite surface of the surface on which the optical film is formed, and forming a matte surface, and transmitting the stress on the substrate by the optical surface by the matte surface to cause the optical The membrane is 'planarized. The optical film planarization method according to claim 5 and the optical film planarization method according to claim 6 are the same in that the film stress of the optical film is offset by the formation of the matte surface, and the planarization of the optical film is performed in accordance with 10 1377372. However, in the optical film planarization method of the fifth aspect, the step of forming the matte surface is performed earlier than the step of forming the optical film (first grinding), and in the method of planarizing the optical film of the sixth aspect, the step of forming the matte surface is formed more than the optical film. After the step (post-grinding), the five aspects are different. In the case of the first grinding, the surface to be polished is formed by the particle size corresponding to the amount of bending of the substrate when the optical film is formed in advance. The amount of bending of the substrate, and the stress caused by the formation of the matte surface is previously relieved. At this time, since the matte surface can be formed in advance with a uniform particle size, 10 is therefore suitable for mass production. In the case of post-grinding, when the optical film is formed on the substrate, the substrate passes through the stress of the optical film and is bent toward the convex direction of the optical film side. Moreover, according to the bending of the substrate The state ' can form a matte surface for correcting together afterwards. Therefore, it is possible to finely flatten the optical film in accordance with the degree of bending of the respective substrates. Here, in the case of forming a matte surface in the case of sanding first, In the case of post-grinding, when the optical film is formed, the substrate is bent by the stress based on the Taiman effect or the film stress of the optical film. At this time, the stress and the optical film based on the Taiman effect are transmitted without the substrate being fixed. The film stress causes the substrate to be bent in one direction. Therefore, the substrate is fixed to a fixing jig or the like in a plane maintaining state by using an adhesive or the like, and the substrate is forcibly maintained in a planar state. The formation of the optical film or the matte surface is transmitted. The formation of the optical film planarization method according to the seventh aspect of the present invention, wherein the optical film planarization method according to the seventh aspect of the present invention, is carried out in this state. When the above-mentioned surface is formed, it is ground by a particle size which planarizes the substrate. When the matte surface is formed with an optimum particle size, the optical film can be brought close to a plane. The optical film planarization method according to claim 8 is the optical 臈 planarization method according to claim 7, further comprising: a micro-adjusting step of forming a matte surface by using the matte forming step The coarser particle size or finer particle size is used to polish the matte surface, and the fine adjustment of the film forming surface closer to the plane is performed. In the case where the matte surface is polished again after the matte surface is formed, when the ratio is used, When the grain size is coarser when the surface is roughened, the stress that moderates the stress of the film acts, and when it is ground with a fine particle size, it acts to relieve the stress based on the stress of the Taiman effect. When the coarse particle size is ground again, the tortuous stress which is convex toward the matte surface acts, and when the matte surface is reground with a finer particle size, the positive bending stress which is convex toward the film formation surface acts. Therefore, 'in the case of post-grinding, when the distortion that protrudes in the direction of the film-forming surface still occurs, 'grinding the matte surface at a coarser grain size', the stress based on the Taiman effect acts to seek optics. Planarization. On the other hand, when the stress caused by the formation of the matte surface exceeds the film stress and the warp is convex toward the rough surface (opposite side of the film formation surface), the matte surface is reground at a finer particle size. The stress caused by the formation of the optical film is flattened. When the stress caused by the formation of the matte surface is insufficient or excessively applied, after the matte surface is formed, the rough surface is finely ground or finely ground again, and fine adjustment can be performed, and the optical film can be obtained. Planarization. That is, after the matte surface is formed, the matte surface is ground with a coarse particle size or a fine particle size of 1,377,372, which is to finely adjust and correct the excessive and insufficient stress. Further, in the method of producing an optical element according to any one of claims 9 to 12 of the present invention, the above optical element element is produced by using the above-described optical film planarization method. As the material of the substrate, a transparent glass material is mainly used as the material, but a transparent plastic material can also be used. Further, when used as a mirror, since no light is transmitted through the inside of the substrate, a non-transparent material can also be used. (10) As the optical film, a dielectric multilayer film composed of a multilayer dielectric film, a dielectric single layer film composed of a single-layer dielectric film, a metal film, or the like can be used. Among them, the dielectric multilayer is a dielectric multilayer film having a large number of layers, and the film stress is enhanced. Therefore, the present invention is particularly effective for such a dielectric multilayer film. As a method of forming an optical film on a substrate, various methods such as a vacuum deposition method, an ion plating method, an ion assist method, a sputtering method, a CVD (Chemical Vapor Deposition Method), a sputtering method, and a polishing method can be used. When the optical element of the present invention is used as a mirror, an optical reader, a liquid crystal projector (projection type display device), or the like can be used as the optical device having the optical element as a constituent member. In the present invention, by forming a matte surface on the opposite surface of the surface on which the optical film is formed, the stress caused by the formation of the matte surface cancels the film stress of the optical film, and the optical film can be obtained even if the special correction film is not formed. Planarization. In particular, when the substrate is thin, the film stress tends to become strong, and the optical film is made to be large. However, since the film stress becomes strong, the transmission is formed on the opposite side.
13 1377372 毛面也可以謀求光學膜的平面化，因此，在這種情況下尤 其奏效。 【實施方式】 5 以下，參照圖式對本發明的實施方式進行說明。在此， 對作爲光學元件使光反射的反射鏡進行說明。圖1中，反射 鏡1主要由玻璃板等平板狀的透明基板1〇構成❶在透明基板 10的一面（被成膜面10S)形成有反射多層膜12作爲光學 膜。被成膜面10S從保證反射多層膜12的光學精度的觀點來 10 看，就必要嚴格地維持平面性。因此，將被成膜面10S預先 進行鏡面研磨。而且，透明基板10的被成膜面10S的相反面 爲毛面13»在此，其是透過粒度粗的研磨劑進行毛面形成 而製成的》 由於反射多層膜12具有内部應力（膜應力），所以， 15 當透明基板10上形成有反射多層膜12時，沿凸方向（向反 射多層膜12側凸出的方向）彎曲的力作用於透明基板1〇 » 然而，在形成有反射多層膜12之面的相反面（被磨面i〇r)， 形成有毛面13。 在用研磨劑打磨薄型透明基板10的一面（被磨面10R) 20 的情況下，透明基板10要向凸方向（向毛面13側凸出的方 向：與在透明基板10形成有反射多層膜12時要脊曲的方向 相反的方向）灣曲。該彎曲的應力被稱爲泰曼（T wyman ) 效應。尤其，當透明基板10薄時，要彎曲的應力（毛面的 形成應力）變大。反射鏡1由於隨著小型化的要求而成爲極 25 度薄型的光學元件’因此’使用透明基板10的板厚度也極 14 1377372 薄的》若這樣’膜應力和毛面的形成應力爲相互相反方向 的應力，因此，可以二者的應力能夠抵消。 在此’最終目的在於將反射多層膜12平面化，不是將 透明基板10整體的形狀形成爲原來的形狀。從而，與反射 5 多層膜12不同’毛面13的形狀爲多少歪曲的形狀也可。另 外’由於反射多層膜12形成在被成膜面i〇s上，因此，只要 反射多層膜12被平面化，被成膜面i〇S也就被平面化。13 1377372 The matte surface can also be used to planarize the optical film, so it is especially effective in this case. [Embodiment] 5 Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Here, a mirror that reflects light as an optical element will be described. In Fig. 1, the mirror 1 is mainly composed of a flat transparent substrate 1 such as a glass plate, and a reflective multilayer film 12 is formed on one surface (film formation surface 10S) of the transparent substrate 10 as an optical film. From the viewpoint of ensuring the optical precision of the reflective multilayer film 12 from the film formation surface 10S, it is necessary to strictly maintain the planarity. Therefore, the film formation surface 10S is mirror-polished in advance. Further, the opposite surface of the film-forming surface 10S of the transparent substrate 10 is a matte surface 13»here, which is formed by the rough surface formation of a coarse-grained abrasive." Since the reflective multilayer film 12 has internal stress (film stress) Therefore, when the reflective multilayer film 12 is formed on the transparent substrate 10, a force which is bent in the convex direction (a direction which is convex toward the reflective multilayer film 12 side) acts on the transparent substrate 1 然而» However, a reflective multilayer is formed. On the opposite side of the surface of the film 12 (the surface to be polished i〇r), a matte surface 13 is formed. In the case where one surface (surface to be polished 10R) 20 of the thin transparent substrate 10 is polished with an abrasive, the transparent substrate 10 is to be convex (the direction protruding toward the matte side 13 side: and the reflective multilayer film is formed on the transparent substrate 10) At 12 o'clock, the direction of the ridge is opposite to the direction) Bay song. This bending stress is called the T wyman effect. In particular, when the transparent substrate 10 is thin, the stress to be bent (forming stress of the matte surface) becomes large. Since the mirror 1 becomes an extremely thin optical element of 25 degrees as required for miniaturization, the thickness of the plate using the transparent substrate 10 is also extremely thin, and the thickness of the film is as thin as 14 1377372. The stress in the direction, therefore, can be offset by the stress of both. Here, the final object is to planarize the reflective multilayer film 12, and the entire shape of the transparent substrate 10 is not formed into the original shape. Therefore, unlike the reflection 5 multilayer film 12, the shape of the matte surface 13 may be a somewhat curved shape. Further, since the reflective multilayer film 12 is formed on the film formation surface i 〇 s, the film formation surface i 〇 S is planarized as long as the reflective multilayer film 12 is planarized.
被磨面10R透過預先進行與被成膜面10S同樣的鏡面 研磨’使被磨面10R和被成膜面l〇S平行。由於反射多層膜 10 12的膜應力的彎曲量以平面爲基準，因此，透過被磨面1〇R 也以平面爲基準’使二者的基準一致。由此，可以容易地 測定彎曲量。 接著，對膜應力進行說明。膜應力除形成於透明基板 10的反射多層膜12的膜的厚度、膜的層數、材料等膜自身 15 的要因外還隨著透明基板10的材料、板厚度等變化。在此， 對透明基板10的板厚度爲[1.5 mm]、並且透過真空蒸鍍法將 反射多層膜12形成於透明基板10的情況進行說明。例如， 反射多層膜12爲二波長對應（CD的波長域的光（波長78 〇nm 附近的光）、DVD的波長域的光（波長65〇nm附近的光）、 20 大容量光碟的光（波長405nm附近的光）三個波長域的光反 射率增高的反射多層膜）的情況，與二波長對應（CD及DVD 的波長域的光反射率增高的反射多層膜）的情況或一波長 對應（CD的波長域的光反射率增高的反射多層膜）的情況 相比，具有膜應力變強的傾向。 15 1377372 另一方面，透過形成毛面使作用於透明基板ίο的應力 (基於泰曼效應的應力）在使用研磨劑時隨著研磨劑的粒 度而不同。在此，作爲研磨劑的粒度的一例，使用粒徑7um、 粒徑16um、粒徑23um這三種。因爲研磨劑的粒度變得越粗 5 (粒徑變得越大）而由毛面的形成所引起的應力就越強， 所以，用粒徑23um進行研磨時作用的應力最強；因爲粒度 變得越細（粒徑變得越小）而由毛面的形成所引起的應力 就越弱，所以’用粒徑7Um進行研磨時作用的應力最弱。 因此’在用與反射多層膜12作用於透明基板1〇的膜應 10 力匹配的粒度形成毛面的情況下，由於二者的應力爲要向 相互相反的方向彎曲的應力’因此’應力可以相互完全地 抵消。而且’即使在使用與膜應力不匹配的粒度的情況下， 就算不能將膜應力完全抵消，也發揮著膜應力的緩和功 能。由此’只要在形成毛面之後反射多層膜12的平面化程 15 度在誤差容許範圍内，就可以使用任意的粒度。 接著，利用圖2的圖表，說明透明基板1〇的板厚度、研 磨劑的粒度、毛面形成後的反射多層膜12的平面化程度的 關係。該圖是表示將反射多層膜12形成在透明基板1〇後以 不同粒度形成毛面時的反射多層膜12的平面化程度的圖 20表。該圖中，用中心變位（μιη)表示平面化程度，圖中的 橫轴表示板厚度，縱軸表示中心變位。 另外’中心變位爲〇μηι時’反射多層膜12理想地爲平 面狀態，中心變位元值越離開〇μΓη，反射多層膜12的彎曲 量變得越大。在值爲正的情況和爲負的情況下彎曲方向相 16 1377372 反》而且，作爲反射多層膜I2,形成爲氡化鈦和二氧化矽 的大約30層左右的相互層疊的多層膜，膜厚爲大約35nm左 右。 圖中所示的圖表中的通常狀態爲完全沒有形成毛面的 5 情況。即’表示純粹基於膜應力的彎曲量。此時，在板厚 度爲1.5mm時，中心變位爲3μπι，在板厚度爲lmm時，中心 變位大約爲7 · 5 μιη。從而，板厚度越薄，透明基板1〇就隨著 反射多層膜12的膜應力而彎曲得越大。 接著’在用粒徑7μπι的研磨劑形成毛面13的情況下， 10 如圖中所示，在板厚度爲1.5mm時，中心變位大約爲丨μιη ; 在板厚度爲1 mm時，中心變位大約爲3μιη。從而，由於可以 緩和反射多層膜12的膜應力，因此，與未形成毛面13的情 況相比，可以將被成膜面10S的彎曲量減小。即，可以謀求 平面化。 15 另一方面’在用粒徑16μηι的研磨劑形成毛面13的情況 下’在板厚度爲1.5mm時’中心變位大約爲〇.7μηι。從而， 用粒度粗的研磨劑形成毛面13,可進一步使被成膜面i〇s平 面化。 在用粒徑23μιη的研磨劑形成毛面13的情況下，在板厚 20 度爲lmm時，中心變位大約爲-0.5μπι。另一方面，在將板 厚度極度變薄到0.3mm左右時，膜應力比由毛面的形成所引 起的應力更強，因此，中心變位大約爲·2μπι。而且，如從 該圖得知，當使用粒徑23μιη的研磨劑在板厚度爲〇.7mm左 右的透明基板10形成毛面時，由於毛面13的應力和膜應力 17 1377372 正好匹配，因此，可以將反射多層膜12完全平面化。 如上所述，透過在反射鏡1的一面（被成膜面l〇S)形 成反射多層膜12而在相反面（被磨面10R)形成毛面13,使 膜應力緩和，就可以將反射多層膜12平面化。在此，按照 5 將反射多層膜12的形成和毛面13的形成中哪一方先進行， 膜應力的緩和量就不同。 首先，關於先形成毛面13之後再進行反射多層膜12的 形成的情況進行說明。如圖3所示，首先，如該圖（a)所 示’對透明基板10的兩面進行鏡面研磨，將被成膜面l〇s及 10 被磨面1 or的兩面形成爲平面狀態（鏡面研磨步驟）。然後， 如該圖（b) ’透過打磨被磨面i〇r而形成毛面13(毛面的 形成步驟）。在此時，根據上述的泰曼效應，透明基板 向毛面13側彎曲。最後，如該圖（c )所示，透過將作爲光 學膜的反射多層膜12形成在透明基板1〇 (光學膜形成步 15 驟）’使反射多層膜12的膜應力和由毛面的形成所引起的 應力匹配，而被成膜面l〇S被平面化，反射多層膜12被平面 化° 採用該方法時’需要預先掌握將反射多層膜12形成在 透明基板10所引起的彎曲量❶透過預測膜應力而相應使透 20 明基板10沿相反方向彎曲，在形成反射多層膜12時謀求平 面化。此時，由於可以均一地對透明基板1〇使用一定粒度 的研磨劑來進行毛面的形成，由於可以預先對多數透明基 板10以一定粒度進行毛面的形成後形成反射多層膜12來製 造反射鏡，因此，適合於大量生産。 18 接著’關於先形成反射多層膜12然後形成毛面13的方 法進行說明。此時也最初對透明基板10的兩面進行鏡面研 磨（鏡面研磨步驟）。然後，如圖3(d)所示，在被成膜 面ios形成作爲光學膜的反射多層膜12 (光學膜形成步 驟）’如該圖（e)所示，在被磨面10R形成毛面13 (毛南 的形成步驟）^此時，由反射多層膜12的形成所引起的膜 應力的作用可透過事後形成毛面13來謀求緩和。這樣進行 的話’即便在隨著固體而膜應力的彎曲量不同的情況下， 由於可以用與實際彎曲量匹配的粒度形成毛面13，因此， 10 可以用細微的精度實現平面化。 如圖4所示，與沒有形成毛面13的情況相比（沒有毛 面在先打磨（先形成毛面13後形成反射多層啤12的方 法）的情況下’可以使中心變位接近〇μιη，從而提高平面 化精度。然而’後打磨（先形成反射多層膜12後形成毛面 15 13的方法），與先打磨相比，可以使中心變位更接近〇，最 能提高平面化精度。即’是採用先打磨還是採用後打磨， 可以根據是重視大量生産還是重視平面化精度來適當選 擇。 而且’無論是採用先打磨的方法還是採用後打磨的方 20 法，透過用比形成毛面13時的粗度更粗的粒度的研磨劑或 更細的粒度的研磨劑再次打磨毛面13,可以謀求反射多層 膜12的平面化◊在形成毛面π後用較粗的粒度的研磨劑再 次對毛面13進扞打磨的情況下，基於上述泰曼效應的應力 起作用，與反射多層膜12的膜應力相反方向的應力起作 19 1377372 用。另一方面，在形成毛面13後用較細的粒度的研磨劑再 次對毛面13進行打磨的情況下，基於上述泰曼效應的應力 減輕’與反射多層膜12的膜應力相同方向的應力起作用。 即’在先打磨的前提下形成反射多層膜12時、在後打 5 磨的前提下形成毛面13時、在反射多層膜12的膜應力還佔 優勢的情況下’用較粗的粒度再次對毛面13進行打磨；在 基於泰曼效應的應力比反射多層膜12的膜應力更佔優勢的 情況下，用較細的粒度再次對毛面13進行打磨，由此，可 以進行平面化的微調整（微調整步驟）。透過進行該微調 10 整步驟’可以謀求反射多層膜12的平面化。該微調整步驟， 是在用由毛面13的形成所引起的應力緩和反射多層膜12的 膜應力時，若發生過度或不足就對該過度或不足量進行調 整的步驟。 如以上說明’透過在形成有光學膜的被成膜面的相反 15面形成毛面，即使被成膜面因光學膜的膜應力而彎曲，也 可以由毛面的形成所引起的應力緩和並謀求光學膜的平面 化0 【圓式簡單說明】 圖1是光學元件的外觀圖。 圖2是表不板厚度、粒度、中心變位元的關係的圖表。 圖3是表示在毛面的形成步驟先進行的情況下、以及光 學膜形成步驟先進行的情況下的各自#製造纟驟流程的 圖0 20 1377372 圖4是表示先打磨、後打磨所引起的中心變位關係的其 他圖表。 【主要元件符號說明】 被磨面10R 毛面13 反射鏡1 透明基板10 被成膜面10S 反射多層膜12The surface to be polished 10R is mirror-polished in the same manner as in the film formation surface 10S in advance, so that the surface to be polished 10R and the film formation surface 10S are parallel. Since the amount of bending of the film stress of the reflective multilayer film 10 12 is based on the plane, the reference to the ground is based on the surface of the surface to be polished. Thereby, the amount of bending can be easily measured. Next, the film stress will be described. The film stress varies depending on the thickness of the film of the reflective multilayer film 12 of the transparent substrate 10, the number of layers of the film, the material itself such as the material, and the thickness of the transparent substrate 10, the thickness of the sheet, and the like. Here, a case where the thickness of the transparent substrate 10 is [1.5 mm] and the reflective multilayer film 12 is formed on the transparent substrate 10 by a vacuum deposition method will be described. For example, the reflective multilayer film 12 has two wavelengths (light in the wavelength range of CD (light near the wavelength of 78 〇 nm), light in the wavelength range of the DVD (light in the vicinity of the wavelength of 65 〇 nm), and light in the 20 large-capacity optical disc ( In the case of a light having a wavelength near 405 nm) a reflective multilayer film having an increased light reflectance in three wavelength domains, a case corresponding to two wavelengths (a reflective multilayer film having an increased light reflectance in a wavelength range of CD and DVD) or a single wavelength The film stress tends to be stronger than in the case of a reflective multilayer film in which the light reflectance in the wavelength region of the CD is increased. 15 1377372 On the other hand, the stress acting on the transparent substrate (the stress based on the Taiman effect) by the formation of the matte surface differs depending on the particle size of the abrasive when the abrasive is used. Here, as an example of the particle size of the polishing agent, three types of particle diameters: 7 μm, 16 μm in particle diameter, and 23 μm in particle diameter are used. The coarser the particle size of the abrasive becomes 5 (the larger the particle size becomes), the stronger the stress caused by the formation of the matte surface is. Therefore, the stress acting on the grinding with the particle size of 23 μm is the strongest; The finer (the smaller the particle size becomes), the weaker the stress caused by the formation of the matte surface, so the stress acting when grinding with a particle size of 7 Um is the weakest. Therefore, in the case where the film which is applied to the transparent substrate 1 with the reflective multilayer film 12 is formed to have a mating particle size of 10 forces, the stresses of the two are to be bent in mutually opposite directions, so the stress can be Completely offset each other. Further, even when a particle size which does not match the film stress is used, even if the film stress cannot be completely canceled, the film stress relaxation function is exerted. Thus, any particle size can be used as long as the planarization process of the reflective multilayer film 12 after forming the matte surface is within the error tolerance. Next, the relationship between the thickness of the transparent substrate 1〇, the particle size of the polishing agent, and the degree of planarization of the reflective multilayer film 12 after the matte surface formation will be described using the graph of Fig. 2 . This figure is a table showing the degree of planarization of the reflective multilayer film 12 when the reflective multilayer film 12 is formed on the transparent substrate 1 and the matte surface is formed with different particle sizes. In the figure, the degree of planarization is represented by a central displacement (μιη), in which the horizontal axis represents the thickness of the plate and the vertical axis represents the central displacement. Further, when the center displacement is 〇μηι, the reflective multilayer film 12 is desirably in a flat state, and the more the center displacement value is removed from 〇μΓη, the larger the amount of bending of the reflective multilayer film 12 becomes. In the case where the value is positive and the case where the value is negative, the direction of the phase is 16 1377372. Further, as the reflective multilayer film I2, a multilayer film of about 30 layers of titanium telluride and ceria is formed, and the film thickness is formed. It is about 35 nm or so. The normal state in the graph shown in the figure is the case where no matte surface is formed at all. That is, ' indicates the amount of bending based solely on the film stress. At this time, when the plate thickness is 1.5 mm, the center displacement is 3 μm, and when the plate thickness is 1 mm, the center displacement is about 7 · 5 μm. Therefore, the thinner the plate thickness, the larger the transparent substrate 1〇 bends with the film stress of the reflective multilayer film 12. Next, in the case where the matte surface 13 is formed with an abrasive having a particle diameter of 7 μm, 10, as shown in the figure, when the thickness of the sheet is 1.5 mm, the center displacement is approximately 丨μιη; at a sheet thickness of 1 mm, the center The displacement is approximately 3 μm. Therefore, since the film stress of the reflective multilayer film 12 can be alleviated, the amount of warpage of the film formation surface 10S can be reduced as compared with the case where the matte surface 13 is not formed. That is, it is possible to achieve planarization. On the other hand, in the case where the matte surface 13 is formed with an abrasive having a particle diameter of 16 μm, the center displacement is about 〇.7 μη when the thickness of the sheet is 1.5 mm. Therefore, the matte surface 13 is formed by using a coarse-grained abrasive, and the film-forming surface i〇s can be further planarized. In the case where the matte surface 13 is formed with an abrasive having a particle diameter of 23 μm, the center displacement is about -0.5 μm when the sheet thickness is 20 mm. On the other hand, when the thickness of the sheet is extremely thinned to about 0.3 mm, the film stress is stronger than the stress caused by the formation of the matte surface, and therefore, the center displacement is about 2 μm. Further, as is apparent from the figure, when a matte surface of a transparent substrate 10 having a sheet thickness of about 7.7 mm is formed using an abrasive having a particle diameter of 23 μm, since the stress of the matte surface 13 and the film stress 17 1377372 are exactly matched, The reflective multilayer film 12 can be completely planarized. As described above, by forming the reflective multilayer film 12 on one surface (the film formation surface 10S) of the mirror 1 and forming the matte surface 13 on the opposite surface (the surface to be polished 10R), the film stress is relaxed, and the reflection multilayer can be performed. The film 12 is planarized. Here, which of the formation of the reflective multilayer film 12 and the formation of the matte surface 13 is performed first in accordance with 5, the amount of relaxation of the film stress is different. First, a case where the formation of the reflective multilayer film 12 is performed after the formation of the matte surface 13 will be described. As shown in Fig. 3, first, as shown in Fig. 3(a), both surfaces of the transparent substrate 10 are mirror-polished, and both surfaces of the film-forming surface 10s and 10 are formed into a planar state (mirror surface). Grinding step). Then, as shown in Fig. 2(b)', the matte surface 13 is formed by grinding the surface i〇r (the step of forming the matte surface). At this time, the transparent substrate is bent toward the matte side 13 in accordance with the above-described Taiman effect. Finally, as shown in the figure (c), by forming the reflective multilayer film 12 as an optical film on the transparent substrate 1 (optical film formation step 15), the film stress of the reflective multilayer film 12 and the formation of the matte surface are caused. The resulting stress is matched, and the film formation surface 10S is planarized, and the reflective multilayer film 12 is planarized. When the method is employed, it is necessary to grasp in advance the amount of warpage caused by the formation of the reflective multilayer film 12 on the transparent substrate 10. By predicting the film stress, the transparent substrate 10 is bent in the opposite direction, and planarization is achieved when the reflective multilayer film 12 is formed. In this case, since the rough surface of the transparent substrate 1 can be uniformly formed by using an abrasive having a certain particle size, the reflective multilayer film 12 can be formed by forming a rough surface of a plurality of transparent substrates 10 with a predetermined particle size in advance to produce a reflection. The mirror is therefore suitable for mass production. 18 Next, a description will be given of a method of forming the reflective multilayer film 12 first and then forming the matte surface 13. At this time, both surfaces of the transparent substrate 10 are first subjected to mirror polishing (mirror polishing step). Then, as shown in FIG. 3(d), a reflective multilayer film 12 as an optical film is formed on the film formation surface ios (optical film formation step). As shown in the figure (e), a matte surface is formed on the surface 10R to be polished. 13 (Step of Forming Maonan) ^ At this time, the effect of the film stress caused by the formation of the reflective multilayer film 12 can be alleviated by forming the matte surface 13 afterwards. In this case, even when the amount of bending of the film stress differs depending on the solid, since the matte surface 13 can be formed with the particle size matching the actual amount of bending, 10 can be planarized with fine precision. As shown in Fig. 4, compared with the case where the matte surface 13 is not formed (in the case where the matte surface is first ground (the method of forming the reflected multi-layer beer 12 after forming the matte surface 13 first), the center can be displaced close to 〇μιη. Therefore, the planarization accuracy is improved. However, 'post-grinding (the method of forming the rough surface 15 13 after forming the reflective multilayer film 12) can make the center displacement closer to the crucible than the first grinding, and the planarization precision can be improved most. That is to say, whether it is to use first grinding or post-grinding, it can be appropriately selected according to whether it is to pay attention to mass production or to pay attention to planarization precision. Moreover, 'whether using the first grinding method or the post-grinding method, the matte surface is formed by the ratio. At 13 o'clock, the coarser particle size abrasive or the finer particle size abrasive re-polishs the matte surface 13, and the planarization of the reflective multilayer film 12 can be achieved. After forming the matte surface π, a coarser particle size abrasive is used. In the case where the matte surface 13 is again rubbed, the stress based on the above-mentioned Taiman effect acts, and the stress in the opposite direction to the film stress of the reflective multilayer film 12 is used for 19 1377372. When the matte surface 13 is again polished with a fine particle size abrasive after the formation of the matte surface 13, the stress relief based on the above-mentioned Teman effect acts on the stress in the same direction as the film stress of the reflective multilayer film 12. 'When the reflective multilayer film 12 is formed under the pre-grinding, when the matte surface 13 is formed on the premise of 5 rubbing, and the film stress of the reflective multilayer film 12 is still dominant, 'with coarser grain size again The matte surface 13 is ground; in the case where the stress based on the Taiman effect is more dominant than the film stress of the reflective multilayer film 12, the matte surface 13 is again polished with a finer particle size, whereby the planarized micro can be performed. Adjustment (fine adjustment step). The planarization of the reflective multilayer film 12 can be achieved by performing the fine adjustment 10 steps. This fine adjustment step is a film for mitigating the reflective multilayer film 12 by the stress caused by the formation of the matte surface 13. In the case of stress, if excessive or insufficient occurs, the excessive or insufficient amount is adjusted. As described above, 'through the opposite 15 faces of the film formation surface on which the optical film is formed, a matte surface is formed, even if it is formed The surface is bent by the film stress of the optical film, and the stress caused by the formation of the matte surface can be relaxed and the planarization of the optical film can be achieved. [Circular Simple Description] Fig. 1 is an external view of the optical element. Fig. 3 is a graph showing the relationship between the thickness of the plate, the particle size, and the center displacement. Fig. 3 is a view showing the flow of the respective # manufacturing steps in the case where the matte surface forming step is performed first and the optical film forming step is performed first. 20 1377372 Fig. 4 is another graph showing the relationship between the center displacement caused by the first grinding and the rear grinding. [Description of the main components] Surface 10R Matte 13 Mirror 1 Transparent substrate 10 Film-forming surface 10S Reflected multilayer film 12
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