JPS6172201A - Infrared transmittable element having protective polished surface - Google Patents

Abstract

PURPOSE:To protect a precision polished surface against deliquescence by the moisture in outdoor air by coating a thin film consisting of a high-polymer material on the precision polished crystal surface of an IR transmittable material constituting an IR transmittable element. CONSTITUTION:The high-polymer material having relatively weak absorption intensity in an IR wavelength region, for example, polymethyl methacrylate of the like is dissolved in an org. solvent, for example, chloroform, etc. On the other hand, the crystal of the precision polished IR transmittable material such as KBr is dipped in a soln. of an org. solvent having high purity, for example, chloroform and the residue of polishing is washed away by high-frequency ultrasonic cleaning, etc. The crystal of the IR transmittable material is then dipped in the dil. soln. of the high-polymer material and when the crystal is thereafter dried at a room temp., the extremely thin film of the high-polymer material is formed on the prescribed polished surface of the crystal. The thin film of the high-polymer material formed in such a manner shuts off thoroughly the polished surface from the moisture in the outdoor air and does not contain pinholes at all.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to infrared transmitting elements used in infrared spectrophotometer cells, high-precision optical path correctors, beam splitters, etc. This invention relates to an infrared transmitting element whose precisely polished surface is preserved from deliquescence caused by moisture in the outside air.

In a conventional infrared spectrophotometer, a large number of various infrared transmitting elements such as cells, optical path correctors, beam splitters, detectors, and sample chamber window materials are used depending on their respective purposes. Most of them need to be solid elements, and most of them are made of alkali/halide-based ionic crystals, so they are more or less deliquescent to moisture contained in the outside air.

For this reason, when it is necessary to maintain the precision polished surface of an infrared transmitting element at a high degree of fit, conventional methods have been used to maintain precision by forcibly controlling the humidity of the outside air containing the infrared transmitting element, or A method that has been used is to deposit a thin film of a crystalline material with relatively weak infrared absorption to protect it from moisture in the outside air. However, the former method necessarily requires a humidity control device, which requires time and effort to operate and adjust.
In the latter type of vapor deposition method, since it is not possible to thicken the vapor deposited film, there are generally always pinholes, and water infiltration through the pinholes due to capillary action always leads to deliquescence, although the time may be longer or shorter. There is a problem in that the accuracy of the polished surface inevitably deteriorates over time.

Therefore, an object of the present invention is to provide an infrared transmitting element that can reliably protect a precisely polished surface from deliquescence due to moisture in the outside air without using a humidity control device, and a method for manufacturing the same.

Structure of the Invention In order to achieve the above object, an infrared transmitting element according to the present invention is formed by coating a thin film of a polymeric material on the precisely polished crystal surface of an infrared transmitting material constituting the element by a solvent evaporation method. It is characterized by:

In order to achieve the above object, the infrared transmitting element according to the present invention is produced by immersing a precisely polished infrared transmitting material crystal constituting the infrared transmitting element in a highly pure organic solvent, and cleaning the precisely polished surface with high frequency ultrasonic waves. A step of immersing the infrared transmitting material crystal after cleaning in a relatively thin solution of a polymeric material having a relatively weak absorption strength in the infrared wavelength region dissolved in an organic solvent, and then immersing the infrared transmitting material crystal in It is produced by a method comprising the steps of raising the crystal in a heated container, drying at room temperature to evaporate the organic solvent, and forming a thin film of polymeric material on the polished crystal surface.

In this way, by coating the precisely polished surface of the infrared transmitting material that makes up the various infrared transmitting elements used in the infrared spectrophotometer needle with a thin film of polymer material using the solvent evaporation method, the precisely polished surface can be Although it is protected from deliquescence due to moisture in the outside air, the specific solvent evaporation method for coating thin films of polymeric materials first involves coating polymeric materials with relatively weak absorption strength in the infrared wavelength range, such as the most common For this purpose, polymethyl meth acrylate is dissolved in an organic solvent such as chloroform to prepare a dilute solution having a concentration of about 100 ppm by weight. −
First, the precision-polished crystal of an infrared transmitting material such as KBr is immersed in a solution of a highly pure organic solvent, such as chloroform, and the polishing residue and adhesion layer are thoroughly washed away by high-frequency ultrasonic cleaning or the like. Next, the infrared transmitting material crystal is immersed in a dilute solution of the above-mentioned polymeric material, then taken up into a container and dried at room temperature. As a result, the organic solvent evaporates, and a very fine layer remains on the precisely polished surface of the crystal. A thin polymer film is formed on the surface. The thin film of the polymer material obtained in this way completely blocks the polished surface from moisture in the outside air, does not contain any pinholes, and is thick enough to completely cover the polished surface. It is desirable to be as thin as possible, and a number of experimental experiences suggest that a thickness of 120.+-.30.times. is preferred.

Incidentally, during actual measurement, the infrared absorption spectrum due to the thin film of the polymer material is proportionally canceled out in the process of calculating the sample spectrum with respect to the reference signal or reference spectrum, and its influence does not appear on the measured spectrum.

Example 1 Polymethyl meth acrylate was dissolved in chloroform to obtain a solution having a molar concentration of about 1'OO ppm. An infrared transmitting crystal material made of KBr, which is a beam splitter element used in a Fourier transform infrared spectrophotometer, was immersed in a high-purity chloroform solution and subjected to high-frequency ultrasonic cleaning. After washing,
The beam splitter was immersed in a solution of the above polymethyl meth acrylate diluted in chloroform.

Then, it was taken up into a Pisces container and dried at room temperature. As a result,
A thickness of approximately 120 mm is placed on the KBr crystal plane of the beam splitter element.
A thin film of polymethyl meth acrylate of X was formed.

Example 2 As a result of a measurement experiment in which the KBr beam sgrit obtained in Example 1 was attached to more than 50 Fourier transform infrared spectrophotometers, it was found that even in the high humidity period of summer, the problem was caused by the dissolution of conventional polished surfaces. No decrease in interference wave intensity was observed.

Example 3 When a KBr crystal treated with a polymer thin film and an untreated KBr crystal were placed side by side and left in a high humidity container of 85% or more, dissolution was confirmed on the surface of the untreated KBr crystal after 6 hours, while the treated KBr crystal was No abnormality was observed on the surface of the crystal even after 36 hours had passed.

Effects of the Invention As is clear from the above explanation, according to the present invention, a thin film of a polymer material is coated on the precisely polished surface of an infrared transmitting element by a solvent evaporation method, which causes disadvantages associated with conventional humidity control methods and vapor deposition methods. It has the advantage that the polished surface can be reliably protected from deliquescence due to moisture in the outside air without being accompanied by.

Claims (3)

[Claims] (1) An infrared transmitting element with a polished surface protected, characterized in that a thin film of a polymer material is coated on the precisely polished crystal surface of an infrared transmitting material constituting the infrared transmitting element by a solvent evaporation method. (2) In the above solvent evaporation method, the precisely polished infrared transmitting material crystal that constitutes the infrared transmitting element is immersed in a highly pure organic solvent, and the precisely polished surface is cleaned with high frequency ultrasonic waves; A step in which the transparent material crystal is immersed in a relatively thin solution of a polymer material with relatively weak absorption intensity in the infrared wavelength range dissolved in an organic solvent; the infrared transparent material crystal is then lifted into a dust-free container and kept at room temperature. An infrared transmitting element according to claim 1, comprising the step of drying to evaporate the organic solvent to form a thin film of polymer material on the polished crystal surface. (3) The thin film of the polymeric material has a thickness of 120±30 Å.
The infrared transmitting element described in item 2).