DIFFRACTION OPTICAL ELEMENT, MANUFACTURING METHOD HEREOF, RESIN COMPOSITION, OPTICAL INSTRUMENT

To provide a diffraction optical element laminated two types of resin layers with different optical characteristics capable of preventing phase shift of transmitted wavefront by reducing refractive index difference that occurs in the resin layer on the side away from the substrate during the manufacturing process.SOLUTION: The diffraction optical element comprises a base material, a first resin layer having a diffraction grating shape formed of concentric multiple rings, and second resin layer containing inorganic particles. In the inorganic particles, the number average particle size is 10 nm or less, and in the volume-based particle size distribution, and has a first peak in the region where the particle size is 2 nm or more and 7.9 nm or less. The inorganic particles have the second peak in the region where the particle size is larger than the first peak. The particle size distribution is adjusted so that the ratio of the maximum intensity of the second peak to the maximum intensity of the first peak is 0.3 or more and 0.8 or less.SELECTED DRAWING: Figure 2 【課題】光学特性が異なる２種類の樹脂層を積層した回折光学素子において、製造工程で基材から離れた側の樹脂層に生じる屈折率差を低減することにより、透過波面の位相ズレを抑制する。【解決手段】基材と、同心円状の複数の輪帯からなる回折格子形状を有する第１樹脂層と、無機粒子を含有する第２樹脂層とからなり、該無機粒子を、個数平均粒子径が１０ｎｍ以下に、体積基準の粒度分布において、粒子径が２ｎｍ以上７．９ｎｍ以下の領域に第１ピークを有し、第１ピークよりも粒子径が大きい領域に第２ピークを有し、第１ピークの最大強度に対する第２ピークの最大強度の比が０．３以上０．８以下である粒度分布に調整する。【選択図】図２