KR102559225B1 - Glass bulk joining method for enlarging glass bulk - Google Patents

Abstract

The present invention relates to a bonding method for increasing the size of a glass optical material, and more particularly, to bonding two or more glass bulks such as glass ingots without micro-bubble remaining on the bonding surface. It relates to a bonding method.
According to the present invention, there is provided a glass bulk bonding method capable of increasing the size of high-purity synthetic quartz glass by preventing micro-bubbles from remaining on the bonding surfaces of a plurality of glass bulks to be bonded.

Description

Glass bulk joining method for enlarging glass bulk}

The present invention relates to a bonding method for increasing the size of a glass optical material, and more particularly, to bonding two or more glass bulks such as glass ingots without micro-bubble remaining on the bonding surface. It relates to a bonding method.

The enlargement of glass optical materials is one of the very important issues in industrialization. In the case of natural quartz glass, a method is generally used in which a large glass bulk is completed through a rapid cooling process after melting natural quartz powder in a crucible in a high-temperature electric furnace. In the case of direct deposition among the methods for manufacturing synthetic quartz glass, a compound (SiCl ₄ ) containing Si is hydrolyzed in a H ₂ /O ₂ (or CH ₄ ) flame in one or more burners to form SiO ₂ glass particles, which are then deposited in the lower collector in a heated state. It becomes. In the case of this deposition method, although it is a suitable method for producing a large glass bulk, it has a disadvantage in that it is very difficult to control remaining micro-bubbles. On the other hand, there is an additional sintering process after soot deposition, so soot deposition methods such as VAD (vapor axial deposition) method, in which OH concentration control and micro-bubble control are relatively easy, have limitations in growing large ingots. In addition, an additional molding process must be performed in order to manufacture a glass bulk after being made into a cylindrical shape.

It is a method of completing the glass bulk through a sintering process after depositing a soot of glass particles. As the soot grows in the deposition process, the load increases, and there are many technical difficulties in making the size large by increasing the size in a space that cannot support the weight. Therefore, attempts have been made to make large bulks by bonding multiple glass bulks in various ways. However, after surface machining of the joint surface, additional processing is performed by methods such as polishing and chemical etching, and then the two surfaces are brought into contact and joined using a torch using a high-temperature melting furnace or fuel gas. The contact surface is fused by viscous flow as the viscosity is lowered by high temperature. However, depending on the degree of face processing, there are many micro-bubbles or inclusions remaining on the interface after bonding, so it is very difficult to secure a consistent glass bulk.

JPJP4315093 B2

The present invention has been devised to solve this problem, and an object of the present invention is to provide a glass bulk bonding method that enables large-sized high-purity synthetic quartz glass by preventing micro-bubbles from remaining on the bonding surfaces of a plurality of glass bulks to be bonded.

In order to achieve the above object, the glass bulk bonding method for enlarging the glass optical material according to the present invention includes (a) melting the surfaces to be bonded (hereinafter referred to as 'joint surfaces') of each of the plurality of glass bulks to be bonded, so that each bonding surface is formed as a molten surface having a surface roughness value of 0.8 nm or less; 및, (b) 각 용융면을 접합시켜 확대된 유리를 형성하는 단계를 포함하고, 상기 단계(a)의 용융면의 형성은, 상기 각 접합면 위에 유리 파우더(glass powder)를 올린 후 각 접합면을 용융시킴으로써 이루어지며, 상기 각 접합면의 용융은, 각 접합면을 토치(torch)로 용융시키거나, 또는 각 접합면을 고온 용융로(furnace) 상태에 노출시킴으로써 이루어지고, 상기 단계(b)의 각 용융면의 접합은, 토치(torch)에 의한 가열에 의해 수행되거나, 또는 고온 용융로(furnace) 상태에서 이루어지며, 상기 각 용융면의 접합이 고온 용융로 상태에서 이루어지는 경우, 상기 고온 용융로의 공정온도는 1800℃ 이상이 유지되고, 상기 공정온도에서 30분 이상을 유지시키고, 이에 의해 점성유체(viscous flow)에 의한 융착이 일어나도록 하여 미세버블이 남지 않도록 하며, 상기 단계(b) 이후, (c) 접합이 완료된 유리에 대하여 잔류 응력을 해소하기 위하여, 800℃ 이상 1100℃ 미만에서 3시간 이상 열처리 공정을 진행하는 단계를 더 포함하며, 상기 단계(b)의 접합에 의해 확대된 유리는, 3방향으로 맥리(striae)를 가지고 있지 않으며 굴절률 균질성이 최대 5x10 ^-6 이하이다.

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The glass enlarged by bonding in step (b) has a birefringence value of 5 nm/nm or less measured at 633 nm, transmittance of 90% or more at a wavelength of 193 nm, bubble-free in the deep ultra violet (DUV) transmittance region, OH concentration in the glass of 0.5 ppm or more and 300 ppm or less, and an ArF eximer laser energy density per pulse of 20 mJ/cm² at an oscillation frequency of 200 Hz. It may have a property that the decrease in transmittance to ArF eximer laser light when irradiated with 2X10 ⁶ pulses is 0.5% or more and 2% or less per 1cm of optical path.

According to another aspect of the present invention, the glass formed by the above bonding method is enlarged.

The glass expanded and formed by the bonding method may not have striae in three directions and have a refractive index homogeneity of up to 5x10 ^-6 or less.

The glass formed by the above bonding method has a birefringence value of 5 nm/nm or less measured at 633 nm, transmittance of 90% or more at a wavelength of 193 nm, is bubble-free in the deep ultra violet (DUV) transmission region, and has an OH concentration of 0.5 ppm or more and 300 ppm or less in the glass. 0 ⁶ It may have the property that the decrease in transmittance to the ArF eximer laser light when irradiated with pulses is 0.5% or more and 2% or less per 1cm of optical path.

According to the present invention, there is an effect of providing a glass bulk bonding method capable of increasing the size of high-purity synthetic quartz glass by preventing micro-bubbles from remaining on the bonding surfaces of a plurality of glass bulks to be bonded.

1 is a schematic diagram showing a bonding process of a plurality of glass bulks using a combustion torch according to the present invention.
2 is a schematic diagram showing a state in which bonding of molten surfaces is completed by the bonding process of FIG. 1;
Figure 3 is a graph showing the transmittance of samples taken from each portion (A, B, C) of the bonded glass bulk of Figure 2;
Figure 4 is a graph showing the FT-IR measurement results of samples taken from each part (A, B, C) of the bonded glass bulk of Figure 2;
Figure 5 is a graph showing the results of measuring the birefringence (stress induced birefringence) of samples taken from each portion (A, B, C) of the bonded glass bulk of Figure 2;

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms or words used in this specification and claims should not be construed as limited to ordinary or dictionary meanings, and the inventors should appropriately define the concept of terms in order to best explain their invention. It should be interpreted as meanings and concepts consistent with the technical idea of the present invention based on the principle that it can be defined. Therefore, since the embodiments described in this specification and the configurations shown in the drawings are only one of the most preferred embodiments of the present invention and do not represent all of the technical spirit of the present invention, it is to be understood that there may be various equivalents and modifications that can replace them at the time of application.

1 is a schematic diagram showing a bonding process of a plurality of glass bulks using a combustion torch according to the present invention, and FIG. 2 is a schematic diagram showing a state in which bonding of molten surfaces is completed by the bonding process of FIG. 1.

FIG. 1 is an example of a glass bulk form in which each surface to be joined of two glass rods 110 and 120 is first melted using a high-temperature torch 10 to form a molten surface having a surface roughness of 0.8 nm or less, and then a process of melting and attaching the two molten surfaces 111 and 121 using a high-temperature heat source.

After processing each of the glass bulks 110 and 120 by a mechanical or chemical method, in order to solve the problem of remaining micro-bubbles on the bonding surface, the cut surface is first melted with a torch (O ₂ -H ₂ , H ₂ -CH ₄ , plasma, etc.), and the surface roughness value is reduced. molten surface of 0.8 nm or less, which is the level of surface roughness. Thereafter, heating is performed using a high-temperature torch (O ₂ -H ₂ , O ₂ -CH ₄ , or a heat source such as plasma) to directly fuse the fusion surfaces of the two glass bulks.

In addition, by bringing the molten surfaces of the two glass bulks into contact in a high-temperature furnace, fusion by viscous flow occurs, resulting in micro-bubbles. A bubble-free fusion result can be obtained. The embodiment of FIG. 1 describes a case in which two quartz glass rods are joined by the above-described method using a combustion torch 10 .

That is, FIG. 1 shows a method of bonding two glass bulks 110 and 120 such as glass ingots so that the bonding surface is free of micro-bubbles. In this case, the number of glass bulks to be bonded is not limited to two, and more than one glass bulk can be bonded. At this time, as described above, the plurality of bonding surfaces to be joined must have molten surfaces (two in the case of FIG. 1, 111 and 121) having a surface roughness of 0.8 nm or less, and as a heat source for bonding the plurality of molten surfaces, in the case of direct heating method, flame fuel gas such as H ₂ -O ₂ , O ₂ -CH ₄ and a plasma torch can be used. .

Alternatively, even when proceeding in a high-temperature furnace, the roughness of the surfaces to be joined must be maintained at 0.8 nm or less, and the process is performed by supplying vacuum or process gas (Nitrogen, Helium, Argon, etc.), and the process temperature must be maintained at least 1800 ° C. In addition, the processing time is maintained at a high temperature for at least 30 minutes to increase the size of glass for optical parts by bonding a plurality of glass bulks in a micro bubble-free state on the bonding surface.

In forming the molten surface of the glass to be joined, glass powder (d ₅₀ >5um or more) is placed on the surface to be joined, and then exposed to a combustion torch or high temperature furnace (>1800 ° C) to form a molten surface.

The bonded glass undergoes a heat treatment process to relieve residual stress. The temperature is carried out at 800 ℃ or more and less than 1100 ℃, and the heat treatment time is prepared through a process that proceeds for at least 3 hours or more.

The quartz glass whose size is enlarged by bonding as described above does not have striae in three directions and has a refractive index homogeneity of 5x10 ^-6 or less at most.

In addition, the quartz glass whose size is enlarged by bonding as described above has a birefringence value of 5 nm/nm or less measured at 633 nm, a transmittance of 90% or more at a wavelength of 193 nm, and is bubble-free in the DUV (deep ultra violet) transmittance region. When 2X10 ⁶ pulses are irradiated, the decrease in transmittance to ArF eximer laser light is 0.5% or more and 2% or less per 1cm of optical path.

FIG. 3 is a graph showing the transmittance of samples taken from each portion (A, B, C) of the bonded glass bulk of FIG. 2 .

This is the transmittance measurement result of samples (each 10mm each) taken from each part (A, B, C) to check whether the bonding surface has been completely bonded in a bubble-free state. It can be confirmed that the transmittance of the samples taken from the three sites is perfectly matched, which shows that the bonded surface is in a bubble-free state and has very high optical homogeneity.

FIG. 4 is a graph showing FT-IR measurement results of samples taken from each portion (A, B, C) of the bonded glass bulk of FIG. 2 .

That is, as an evaluation to confirm the difference in physical properties due to bonding of the samples taken from each part (A, B, C), it is the FT-IR measurement result. It shows that the absorption wavelength according to the wavenumber matches perfectly except for the OH absorption wavelength. The OH absorption peak of the sample taken from the bonding surface was higher than that of the other two parts, and the difference value was less than 5 ppm. These results show that homogeneity in physical properties that does not significantly affect physical properties can be maintained even if the proposed method is bonded.

FIG. 5 is a graph showing the results of measuring stress induced birefringence of samples taken from each portion (A, B, C) of the bonded glass bulk of FIG. 2 .

In FIG. 5, the birefringence value of sample B is almost similar to the rest of the values in the center, but the residual stress on the surface shows higher tensile stress than samples A and C that are not heated.

10: Combustion torch
110,120: glass bulk
111, 121: melting plane of each glass bulk
130: surface where two glass bulks are bonded

Claims (11)

As a bonding method of glass bulk for the enlargement of glass optical materials,
(a) melting the surfaces to be bonded (hereinafter referred to as 'bonding surfaces') of each of the plurality of glass bulks to be bonded, so that each bonding surface is formed into a molten surface having a surface roughness value of 0.8 nm or less; and,
(b) forming an enlarged glass by bonding each melting surface
including,
The formation of the molten surface in step (a),
It is made by melting each bonding surface after placing glass powder on each bonding surface,
Melting of each joint surface,
Melting each joint surface with a torch, or
Each bonding surface is exposed to high temperature furnace conditions
is done by
The bonding of each melting surface in step (b),
carried out by heating with a torch, or
It is made in a high temperature melting furnace state,
When the bonding of each melting surface is made in a high-temperature melting furnace state,
The process temperature of the high-temperature melting furnace is maintained at 1800 ° C or higher,
Maintaining at least 30 minutes at the process temperature,
This allows fusion by viscous flow to occur so that no microbubbles remain,
After step (b),
(c) performing a heat treatment process at 800 ° C or more and less than 1100 ° C for 3 hours or more in order to relieve residual stress on the glass that has been bonded
Including more,
The glass enlarged by the bonding in step (b),
It has no striae in three directions and has a refractive index homogeneity of up to 5x10 ^-6 or less,
Glass bulk bonding method for large-sized glass optical materials.
delete delete delete delete delete delete The method of claim 1,
The glass enlarged by the bonding in step (b),
The birefringence value measured at 633nm is less than 5nm/nm, the transmittance is over 90% at a wavelength of 193nm, it is bubble-free in the DUV (deep ultra violete) transmission range, the OH concentration in the glass is between 0.5ppm and less than 300ppm, and the ArF eximer laser is irradiated with 2X10 ⁶ pulses at an energy density per pulse of 20mJ/cm² and an oscillation frequency of 200Hz. It has the property that the decrease in transmittance for eximer laser light is 0.5% or more and 2% or less per 1cm of optical path.
Glass bulk bonding method for large-sized glass optical material, characterized in that. Glass enlarged and formed by the bonding method of claim 1. The method of claim 9,
Having no striae in three directions and having a refractive index homogeneity of up to 5x10 ^-6 or less
Characterized in that, the glass formed by the expansion of the bonding method of claim 1. The method of claim 9,
The birefringence value measured at 633nm is less than 5nm/nm, the transmittance is over 90% at a wavelength of 193nm, it is bubble-free in the DUV (deep ultra violete) transmission range, the OH concentration in the glass is between 0.5ppm and less than 300ppm, and the ArF eximer laser is irradiated with 2X10 ⁶ pulses at an energy density per pulse of 20mJ/cm² and an oscillation frequency of 200Hz. It has the property that the decrease in transmittance for eximer laser light is 0.5% or more and 2% or less per 1cm of optical path.
Characterized in that, the glass formed by the expansion of the bonding method of claim 1.