CN109082632B

CN109082632B - Infrared low-refractive-index mixed coating material and preparation method thereof

Info

Publication number: CN109082632B
Application number: CN201810945365.XA
Authority: CN
Inventors: 谢平; 李斌; 于天燕; 刘定权
Original assignee: Shanghai Institute of Technical Physics of CAS
Current assignee: Shanghai Institute of Technical Physics of CAS
Priority date: 2018-08-20
Filing date: 2018-08-20
Publication date: 2021-01-01
Anticipated expiration: 2038-08-20
Also published as: CN109082632A

Abstract

The invention discloses an infrared low-refractive-index mixed coating material and a preparation method thereof, wherein the material is prepared by mixing praseodymium fluoride and barium fluoride, and the molar component ratio of the two materials is as follows: 70-80 parts of praseodymium fluoride and 30-20 parts of barium fluoride. The material has small refractive index and no radioactivity, and the prepared thin-layer spectral performance is superior, particularly the film stress is superior to that of the conventional low-refractive-index coating material.

Description

Infrared low-refractive-index mixed coating material and preparation method thereof

Technical Field

The invention relates to the field of optical thin film materials, in particular to an infrared low-refractive-index material and a preparation method thereof.

Background

According to the design theory of the antireflection film, the lowest refractive index value which can be achieved by the film material at the air interface determines the performance of the whole optical system. Therefore, in designing an antireflection film, in order to achieve the highest transmittance and the widest transmission range, a material having the lowest refractive index is always desirable as the outermost film layer material.

The lowest index of refraction ir-coating material currently available for practical use is thorium fluoride (ThF 4). However, due to the radioactivity of thorium element, the cleaning work after evaporating thorium-containing compound and radioactive treatment greatly limit the use of thorium-containing compound in infrared broad spectrum antireflection.

At present, in the application of infrared broad spectrum antireflection, the infrared low-refractive-index coating materials for replacing thorium fluoride are mainly yttrium fluoride (YF3) and praseodymium fluoride (PrF 3). However, they cannot be used directly as the outermost layer of an antireflection film system because of their high film stress and low reliability. It is usually necessary to plate a film layer with a higher refractive index (such as zinc selenide and diamond) as a protective layer on the outermost layer of the antireflection film system, so as to reduce the antireflection effect.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides an infrared low-refractive-index mixed coating material.

The material is formed by mixing praseodymium fluoride and barium fluoride, the refractive index is 1.35, and the molar composition ratio of the two materials is as follows: 70-80 parts of praseodymium fluoride and 30-20 parts of barium fluoride, and the shape of the mixed coating material is a cylinder.

The components of the mixed coating material do not contain radioactivity, the refractive index is equivalent to that of the infrared low-refractive-index coating material mainly used at present, and the spectral performance is superior to that of other infrared low-refractive-index coating materials (figure 1). The thickness of a single-layer film plated by the material can reach 2um, while the thickness of a fluoride material which is conventionally used can only reach 1 um.

The material is mainly characterized in that the stress of a film layer is small, the stress of a single-layer film with the same thickness is smaller than that of other infrared low-refractive-index materials (figure 2).

The thickness of a single-layer film prepared from the material can reach 2um, and the film is not demoulded after being torn by an adhesive tape after being subjected to a 1-week water soaking experiment.

The material has excellent evaporation performance, is plated by adopting an electron beam evaporation method, has small beam requirement and stable evaporation rate.

The preparation process of the mixed material is simple, firstly, the mixed powder material is cold-pressed into a cylinder under a press with the pressure of 40MPa, and then the cylinder is placed into a sintering furnace for high-temperature sintering at the sintering temperature of 900 ℃ for 180 minutes.

Drawings

FIG. 1 is a diagram showing the comparison of the optical properties of the infrared low-refractive-index mixed coating material of the present invention and other conventional low-refractive-index coating materials, wherein 20,25, and 30 respectively represent the percentage content of barium fluoride in the mixed coating material. The thickness of the film of the material is 2um, and the thickness of the films of other three materials is 1 um.

FIG. 2 is a graph comparing film stress of the infrared low-refractive-index hybrid coating material of the present invention with other conventional low-refractive-index coating materials.

Detailed Description

The present invention is further illustrated by the following examples, which should not be construed as limiting the scope of the invention.

Example 1:

praseodymium fluoride and barium fluoride are added according to the molar percentage of 80%: mixing 20 percent of the raw materials, and performing cold press molding, high-temperature sintering and other processes to obtain the cylindrical material. The single-layer film with the thickness of 2um is plated by an electron beam evaporation method, the spectral performance of the single-layer film is shown in figure 1, and the stress of the film layer is 77.06 MPa.

Example 2:

praseodymium fluoride and barium fluoride are added according to the molar percentage of 75%: mixing the raw materials by 25 percent, and obtaining the cylindrical material after cold press molding, high-temperature sintering and other technological processes. A single-layer film with the thickness of 2um is plated by an electron beam evaporation method, the spectral performance of the single-layer film is shown in figure 1, and the stress of the film layer is 63.61 MPa.

Example 3:

praseodymium fluoride and barium fluoride are added according to the molar percentage of 70%: mixing 30 percent of the raw materials, and obtaining the cylindrical material after cold press molding, high-temperature sintering and other technological processes. A single-layer film with the thickness of 2um is plated by an electron beam evaporation method, the spectral performance of the single-layer film is shown in figure 1, and the stress of the film layer is 49.17 MPa.

Claims

1. An infrared low-refractive-index mixed coating material is characterized in that:

the mixed coating material is formed by mixing praseodymium fluoride and barium fluoride, wherein the molar percentage of the praseodymium fluoride to the barium fluoride is (70-75%) to (30-25%);

the preparation process of the mixed coating material comprises cold press molding and high temperature sintering;

the cold pressing pressure of the mixed coating material during cold pressing molding is 40 MPa; the sintering temperature in the high-temperature sintering is 900 ℃, and the time is 180 minutes;

the infrared low-refractive-index mixed coating material is coated by adopting an electron beam evaporation method;

the refractive index of the infrared low-refractive-index mixed coating material is 1.35, and the thickness of a single-layer film coated by the material can reach 2 um.

2. The infrared low refractive index hybrid coating material of claim 1, wherein the hybrid coating material is in the shape of a cylinder.