Optical filter and imaging device

Abstract

This optical filter comprises a first dielectric multilayer film, a near-infrared ray absorbing glass substrate, a second dielectric multilayer film, a resin film, and a third dielectric multilayer film in this order. The plate thickness of the near-infrared ray absorbing glass substrate is 0.12 mm or less. If the thickness of the first dielectric multilayer film is denoted by L1, the thickness of the second dielectric multilayer film is denoted by L2, and the thickness of the third dielectric multilayer film is denoted by L3, the absolute value of a value represented by [(L2 + L3) - L1] is 3,000 nm or less. On an end surface of the near-infrared ray absorbing glass substrate, observed are: a cracking region that extends in a direction stretching along the main surface of the near-infrared ray absorbing glass substrate and has a Ra of 0.5-1.5 μm; and a pair of mirror surface layers between which is held the cracking region and which have an Ra of less than 0.5 μm. The width W of the cracking region in the plate thickness direction of the near-infrared ray absorbing glass substrate is 20-40% of the plate thickness T of the near-infrared ray absorbing glass substrate.

Claims

1. The apparatus comprises a first dielectric multilayer film, a near-infrared absorbing glass substrate, a second dielectric multilayer film, a resin film, and a third dielectric multilayer film in this order, wherein the thickness of the near-infrared absorbing glass substrate is 0.12 mm or less, and when the thickness of the first dielectric multilayer film is L1, the thickness of the second dielectric multilayer film is L2, and the thickness of the third dielectric multilayer film is L3, the absolute value of the value expressed as [(L2 + L3) - L1] is 3000 nm or less, and a crack region extending in the direction along the main surface of the near-infrared absorbing glass substrate and a pair of mirror-finished layers sandwiching the crack region are observed on the end face of the near-infrared absorbing glass substrate, the surface roughness Ra of the crack region on the end face is 0.5 to 1.5 μm, and the surface roughness Ra of the mirror-finished layers on the end face is less than 0.5 μm. An optical filter in which the width W in the thickness direction of the near-infrared absorbing glass substrate with respect to the crack region is 20 to 40% of the thickness T of the near-infrared absorbing glass substrate.

2. The optical filter according to claim 1, wherein the thickness of the first dielectric multilayer film is 5500 nm or less.

3. The optical filter according to claim 1, wherein when P is the distance from the main surface of the near-infrared absorbing glass substrate on the side where the resin film is provided to the center of the width W in the thickness direction of the crack region, and T is the thickness of the near-infrared absorbing glass substrate, the ratio of the distance P to the thickness T (P / T) is 0.4 to 0.

6.

4. The optical filter according to claim 1, wherein a hackle is observed in the mirror-finish layer, extending from the crack region toward one main surface side or the other main surface side of the near-infrared absorbing glass substrate, and the length of the hackle is defined as the distance between a line segment L1 passing through one end of the hackle and parallel to the main surface of the near-infrared absorbing glass substrate and a line segment L2 passing through the other end of the hackle and parallel to the main surface of the near-infrared absorbing glass substrate, and the length of the hackle is 30 μm or less.

5. The fracture toughness of the near-infrared absorbing glass substrate is 0.50 MPa·m １／２ The optical filter according to claim 1, which is as follows:

6. The thermal expansion coefficient of the near-infrared absorbing glass substrate is 120 × 10 －７ The optical filter according to claim 1, wherein the K is greater than or equal to / K.

7. The optical filter according to claim 1, wherein the near-infrared absorbing glass substrate is phthalic acid glass.

8. The fluorphosphate glass, expressed in mass%, contains P ５＋ : 30 to 70% by mass, Al ３＋ : 0 to 20% by mass, Li ＋ : 0 to 20% by mass, K ＋ : 0 to 20% by mass, Mg ２＋ : 0 to 10% by mass, Ca ２＋ : 0 to 20% by mass, Sr ２＋ : 0 to 30% by mass, Ba ２＋ : 0 to 40% by mass, Cu ２＋ : 1 to 20% by mass, ΣR ＋ : 0.1 to 30% by mass (R ＋ is at least one component selected from the group consisting of Li ＋ and K ＋ ) ΣR ２＋ : 10 to 45% by mass (R ２＋ is at least one component selected from the group consisting of Mg ２＋ , Ca ２＋ , Sr<000002D>, and Ba ２＋ ) and contains 5 to 70% by mass of F － by external division. The optical filter according to claim 7.

9. The optical filter according to claim 1, which satisfies the following spectral characteristics (i) to (iii) when the first dielectric multilayer film side is the incident direction side. (i) When the average transmittance for wavelengths of 450-600 nm in the spectral transmittance curve at an incident angle of 0 degrees is T[450-600(0deg)AVE], and the average transmittance for wavelengths of 450-600 nm in the spectral transmittance curve at an incident angle of 35 degrees is T[450-600(35deg)AVE], the absolute value of the difference between T[450-600(0deg)AVE] and T[450-600(35deg)AVE] is 5% or less. (ii) In the spectral transmittance curve at an incident angle of 0 degrees, the wavelength IR30(0deg) at which the transmittance is 30% is in the range of 600-700 nm, and in the spectral transmittance curve at an incident angle of 35 degrees, the wavelength IR30(35deg) at which the transmittance is 30% is in the range of 600-700 nm. (iii) The absolute value of the difference between IR30 (0 deg) and IR30 (35 deg) is 10 nm or less. (iii) In the spectral transmittance curve at an incident angle of 0 degrees, the average transmittance T [750 - 1000 (0 deg) AVE] for wavelengths of 750 to 1000 nm is 1% or less.

10. An imaging apparatus having an optical filter according to any one of claims 1 to 9.

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