KR101929884B1 - Method for polishing polycrystalline zinc sulfide - Google Patents

Abstract

The present invention relates to a polycrystalline zinc sulfide polishing method. An opaque film formed on the surface of zinc sulfide grown CVD for the purpose of use based on optical material processing is removed, and thus zinc sulfide permeability can be efficiently raised. A zinc sulfide sample grown by CVD is mounted on the table of the polishing machine, slurry concentration and a table rotation speed are set in three stages, and polishing shaft pressure is set in two stages. Then, with respect to each configuration, the zinc sulfide sample is polished until the surface roughness of the zinc sulfide sample reaches lambda/2 or less. The slurry concentration, the polishing shaft pressure, and the table rotation speed applied during the polishing process with the shortest measurement time until the measured surface roughness of the zinc sulfide sample reaches lambda/2 or less are set as standard processing conditions of the zinc sulfide sample.

Description

[0001] The present invention relates to a method for polishing polycrystalline zinc sulfide,

The present invention relates to a method of polishing an optical base material surface, and more particularly, to a method for polishing a surface of an optical base material, in which an opaque film formed on the surface of zinc sulfide grown by a CVD method is removed, The present invention relates to a polishing method of zinc.

In general, zinc sulfide (ZnS) has been used in the manufacture of IR windows.

An infrared window made of zinc sulphide was initially prepared by hot compression. The infrared window fabrication by the hot pressing method is a method of preparing an optical element made of polycrystalline by putting zinc sulfide powder in a mold and then performing a vacuum treatment and heating the zinc sulfide to a high temperature of 1420-1770 ((for example, 1550 다음) , Pressure of 20,000-40,000 psi is applied by hydraulic press for 5-35 minutes while maintaining high pressure.

However, since the initial zinc sulfide described above is difficult to produce at a certain level or more, there is an increased demand for large-sized zinc sulfide base materials having better optical characteristics. As a result, a chemical vapor deposition (CVD) method has been developed for manufacturing a polycrystalline infrared window. The CVD method is a method in which vaporized zinc is reacted with hydrogen sulfide at a high temperature to deposit and grow zinc sulfide on a substrate made of graphite.

Zinc sulphide grown by the CVD method forms an opaque film on the surface. Due to the characteristics of an infrared window which must have proper strength and transparency without hindering the optical properties, the opaque film formed on the surface of zinc sulfide grown by the CVD method A polishing process for removing the polishing pad is indispensably required.

Since conventional polishing processes are focused on silicon wafers or quartz, polishing conditions suitable for the physical properties of zinc sulfide are required to polish zinc sulfide having completely different physical properties.

One of the polishing methods of zinc sulfide is called "Kuramoto Yanji". The Kuramoto soft polishing method is a polishing method using a 'Kuramoto polishing machine'. Since it is a non-quantitative polishing method in which the polishing quality is determined by the operator's long experience and know-how, there is an inefficient problem that the work can not be standardized.

Therefore, it is urgent to provide a standardized zinc sulphide polishing method by quantitatively deriving the most efficient conditions for polishing zinc sulphide and applying it to polishing.

KR 10-1995-0029212 A (1995.11.22) US 3,131,025 B1 (1964.04.28) US 3,131,238 B1 (1964.04.28) US 3,131,026 B1 (1964.04.28) US 3,454,685 B1 (July 19, 1969) US 4,366,141 B1 (Dec. 28, 1982) KR 10-2014-0148467A (2014.12.31)

Accordingly, the present inventor has focused on solving the limitations and problems of the conventional zinc sulfide polishing method by comprehensively taking into consideration the above-mentioned matters, and by deriving the most efficient conditions for polishing the zinc sulfide and quantitatively applying it, As a result, the inventors of the present invention have invented the present invention as a result of intensive efforts to develop a new polishing method capable of standardizing the polishing method.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a polycrystalline zinc sulfide polishing method capable of quantitatively deriving optimum conditions for a pressure, a surface rotation speed, and a slurry concentration required for zinc sulfide polishing, and standardizing the same.

Herein, the technical object and object to be solved by the present invention are not limited to the technical object and purpose mentioned above, and another technical object and purpose not mentioned can be understood by those skilled in the art from the following description.

According to another aspect of the present invention, there is provided a polycrystalline zinc sulfide polishing method comprising the steps of: mounting a zinc sulfide specimen grown by a CVD method on a surface of a polishing machine; setting a slurry concentration and a surface rotation speed in three steps, The concentration was set to 100 g / L for the first stage, 200 g / L for the second stage and 400 g / L for the third stage, and the first, second and third stages were set to 50RPM, 100RPM and 150RPM, A first process of setting the polishing shaft pressure to two stages, setting the first and second stages to 0 MPa and 0.3 MPa, respectively, and setting the polishing shaft pressure to two stages; The surface roughness of the zinc sulfide specimen was periodically measured under the pressure of the first stage polishing slurry and the surface roughness was measured at the surface roughness measuring wavelength? A second step of polishing the zinc sulfide specimen while sequentially changing the speed from the first step to the third step; The surface roughness of the zinc sulfide specimen is periodically measured under the second-stage polishing shaft pressure until the surface roughness becomes less than? / 2 A third step of polishing the zinc sulfide specimen while sequentially changing the rotational speed of the surface of the specimen from the first step to the third step; A fourth step of changing the concentration of the first step slurry to a second step slurry concentration to supply the slurry, and repeating the second step and the third step; A fifth step of changing the second slurry concentration to a third slurry concentration to supply the slurry, and repeating the second and third steps; The slurry concentration, the polishing axis pressure, and the surface rotation speed, which are applied in the measured polishing process, are measured in the shortest time until the surface roughness of the zinc sulfide specimen measured in the second to fifth steps becomes? / 2 or less, And a sixth step of setting standard working conditions of the zinc sulfide specimen.

At this time, in the polycrystalline zinc sulfide polishing method according to the present invention, the surface roughness of the zinc sulfide specimen is preferably measured every 20 minutes.

delete

In the polycrystalline zinc sulfide polishing method according to the present invention, when the surface roughness of the zinc sulfide specimen is less than? / 2 and the polishing time is shorter than the measured time, the slurry applied in each polishing step It is preferable to set the slurry concentration with the lowest concentration, the polishing axis pressure, and the surface rotation speed as standard processing conditions for the zinc sulfide specimen.

As described above, the present invention has the effect of standardizing the polycrystalline zinc sulfide grown by the CVD process through quantitative indices.

Accordingly, the present invention has the effect of achieving the necessary polishing quality without depending on the experience of the skilled person, and has the effect of greatly improving the polishing efficiency of zinc sulfide.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of a polishing machine for explaining a polycrystalline zinc sulfide polishing method according to the present invention;
FIGS. 2 to 4 are graphs showing the relationship between surface roughness and polishing time using a quantitative index required for standardization of the polycrystalline zinc sulfide polishing method according to the present invention. FIG.

Hereinafter, embodiments of a polycrystalline zinc sulfide polishing method according to the present invention will be described in detail with reference to the drawings. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS The same features of the Figures represent the same reference symbols wherever possible. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. , ≪ / RTI > equivalents, and alternatives. In the following description of the present invention, detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

Hereinafter, the attached drawings are exaggerated or simplified in order to facilitate understanding and clarification of the structure and operation of the technology, and it is to be understood that each component does not exactly coincide with the actual size.

The terms first, second, etc. may be used to describe various components, but the components are not limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It is to be understood that the same terms as those defined in the commonly used terms are defined in consideration of the functions of the present invention and are to be construed in accordance with the technical idea of the present invention and the meaning commonly understood or commonly recognized in the technical field And is not to be construed as an ideal or overly formal sense unless expressly defined to the contrary.

The present invention relates to a method and apparatus for transmitting light in an infrared spectrum, for example, a 0.7-1.0 m near-infrared band in the 0.7-14 mu m wavelength range, a 3-5 mu m medium wavelength infrared band (MWIR) and a 8-14 mu m long wavelength infrared band (LWIR) To a polycrystalline zinc sulphide polishing method quantitatively adapted to the specific properties of polycrystalline zinc sulphide used as a material for infrared windows, dome and lenses depending on the characteristics thereof.

First, the polycrystalline zinc sulfide polishing method according to the present invention quantitatively derives optimum conditions (surface rotation speed, pressure, slurry concentration) for minimizing the polishing time and effectively lowering the surface roughness in the polishing of zinc sulfide, The abrasive effect is verified.

FIG. 1 is a schematic view of a polishing machine for explaining a polycrystalline zinc sulfide polishing method according to the present invention. In FIG. 1, a nozzle 160 (not shown) is attached to a polishing pad 130 mounted on a base plate 110 rotated by a first rotating means 120 And the surface of the zinc sulfide specimen 101 mounted on the lower surface of the specimen is moved to a polishing pad (not shown) by the second rotating means 140 while being moved in a predetermined pressure and pattern by the rotating and polishing shaft 150 while the slurry is supplied through the polishing pad 130 to grind and polish.

As a main factor for determining the polishing quality of the zinc sulfide specimen 101, the quantitative indexes that can be changed during polishing are the table rotation speed R, the polishing shaft pressure P, and the slurry concentration C, Were selected as polishing conditions and the change of surface roughness was observed over time.

The specimen (101) of zinc sulfide was 6T in Ø30, and the slurry was RHODAX 1.0CR manufactured by Universal Photonics, which was composed of 99.99% alumina, and the polishing pad was made of a polyester material.

In the polishing test, a slurry was supplied to the polishing pad using a Kuramoto polishing machine, and the zinc sulfide specimen was brought into close contact with the polishing pad to perform polishing.

(1) Slurry concentration (C)

The concentration of the alumina slurry (<0.5 μm) used for polishing the zinc sulfide specimen 101 was divided into three levels of 100 g / L, 200 g / L and 400 g / L, and polishing was carried out at respective concentrations.

(2) Platen rotational speed (R)

The polishing speed of the polishing pad, which is the rotating speed of the polishing pad in contact with the zinc sulfide specimen, was divided into three steps of 50RPM, 100RPM and 150RPM.

(3) Polishing axis pressure (P)

The polishing pressure was divided into two steps of 0 MPa and 0.3 MPa between the zinc sulfide specimen and the polishing pad.

For the total of 18 polishing conditions in which the above three abrasive quantitative indexes were combined, the optimum condition was derived by measuring the time of surface roughness down to? / 2 in 20-minute increments. The results are shown in the graph of FIG. 1 .

A total of 18 polishing conditions are shown in Table 1 below.

As shown in Table 1, the test range is selected on the basis of the polishing conditions of general infrared window materials for a total of 18 conditions and the remaining conditions, and the surface of zinc sulfide is reduced to a surface roughness of? / 2 The time was measured in units of 20 minutes to find the optimum condition. The results are shown in the following Table 2 and FIG. 2 to FIG. 4. FIG. 2 to FIG. 4 are graphs showing the relationship between surface roughness and polishing time to which a quantitative index necessary for standardization of the polycrystalline zinc sulfide polishing method according to the present invention is applied. In the following test, when the surface roughness value was measured to be 0.5 (? / 2) or less, subsequent polishing was not performed.

Therefore, in the polycrystalline zinc sulfide polishing method according to the present invention, it was confirmed that the polishing rate was improved as the slurry concentration was 200 g / L and the pressure was 0.3 MPa and the rotating speed of the table was higher. However, when the polishing rate was over 150 RPM, The most excellent polishing results were obtained in the 12th condition of Table 1 in consideration of the working efficiency. In the condition 12 of Table 1 above, the surface roughness value reached the? / 2 level at the third measurement time (80 minutes).

At this time, condition 15 showed similar tendency to condition 12, but condition 12, which used less slurry, was judged to be more efficient.

As described above, the polycrystalline zinc sulfide polishing method according to the present invention can quantitatively determine the optimum conditions for the pressure, the surface rotation speed, and the slurry concentration required for zinc sulfide polishing to standardize the most efficient conditions for zinc sulfide polishing have.

Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. Therefore, the scope of the present invention should not be limited by the described embodiments, but should be determined by the scope of the appended claims and equivalents thereof.

101: Zinc sulphide specimen 110: Plate
120: first rotating means 130: polishing pad
140: second rotating means 150: polishing shaft
160: Nozzle R: Platen rotational speed
P: Polishing axis pressure C: Slurry concentration

Claims (4)

A zinc sulfide specimen grown by a CVD method was mounted on a surface plate of a polishing machine, and the slurry concentration and the surface rotation speed were set to three stages and the polishing axis pressure was set to two stages. The slurry concentration was 100 g / L, 200 g / L for the second step and 400 g / L for the third step, and the first, second and third steps are set to 50 RPM, 100 RPM and 150 RPM, respectively, A first step of setting the first and second stages to 0 MPa and 0.3 MPa, respectively;
The surface roughness of the zinc sulfide specimen was periodically measured under the pressure of the first stage polishing shaft and the surface roughness was measured at the surface roughness measurement wavelength (?) / 2 or less A second step of polishing the zinc sulfide specimen while sequentially changing the speed from the first step to the third step;
The surface roughness of the zinc sulfide specimen is periodically measured under the second-stage polishing shaft pressure until the surface roughness becomes less than? / 2 A third step of polishing the zinc sulfide specimen while sequentially changing the rotational speed of the surface of the specimen from the first step to the third step;
A fourth step of changing the concentration of the first step slurry to a second step slurry concentration to supply the slurry, and repeating the second step and the third step;
A fifth step of changing the second slurry concentration to a third slurry concentration to supply the slurry, and repeating the second and third steps;
The slurry concentration, the polishing axis pressure, and the surface rotation speed, which are applied in the measured polishing process, are measured in the shortest time until the surface roughness of the zinc sulfide specimen measured in the second to fifth steps becomes? / 2 or less, And a sixth step of setting a standard processing condition of the zinc sulfide specimen.
The method according to claim 1, wherein the surface roughness of the zinc sulfide specimen,
Wherein the polishing is carried out every 20 minutes.
delete The method according to claim 1,
When the surface roughness of the zinc sulfide specimen is less than lambda / 2, the measured slurry concentration has the lowest slurry concentration applied in each polishing process, the polishing rate and the rotational speed Is set as a standard processing condition of the zinc sulfide specimen.

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