Abstract: Provided is a film for a wavelength conversion sheet that can suppress a change in color with time when applied to a wavelength conversion sheet. A film for a wavelength conversion sheet, comprising a primer layer and a first base material film in presented order, wherein a refractive index of the primer layer is defined as n1, a thickness of the primer layer is defined as t1, and a refractive index of the first base material film is defined as n2, and the following condition 1 or the following condition 2 is satisfied: Condition 1: n1<n2, and d1 represented by the following expression 1 represents a range of x±0.10 wherein x is an odd integer; Condition 2: n1>n2, and d1 represented by the following expression 1 represents a range of x±0.10 wherein x is an even integer; Expression 1: d1=n1×t1/112.5 nm.

Abstract: Provided is a barrier film that can suppress a change in color when applied to a wavelength conversion sheet. A barrier film for a wavelength conversion sheet that is a barrier film comprising at least one inorganic oxide layer and at least one organic coating layer on one surface of a light-transmitting base material, wherein a value of a water vapor transmission rate according to JIS K7129-2:2019 is 0.20 g/m2·day or less, and when a spectral transmittance of the barrier film is measured with a surface of a side comprising the inorganic oxide layer and the organic coating layer as a light coming-in surface, the barrier film comprises a spectral transmittance bottom at which the spectral transmittance changes from decreasing to increasing, or a spectral transmittance peak at which the spectral transmittance changes from increasing to decreasing, in the range of 450 nm±7 nm.