JPH08175847A - Method for selective etching glass and production of channel plate - Google Patents

Abstract

PURPOSE: To provide a method for etching an element of glass selectively and at a relatively high speed in a glass composite material comprising glass having two kinds of different compositions such as a channel plate precursor. CONSTITUTION: A glass composite material comprising glass A having <=30mol% content of meshes modifying oxide and glass B having >=45mol% content of meshes modifying oxide is immersed in an aqueous solution of an acid to provide a method for preferentially etch glass B. The aqueous solution of the acid contains at least one ion selected from the group consisting of a metal ion constituting the meshes modifying oxide, a metal ion constituting an intermediate oxide and a borate ion.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for selectively etching one glass of a glass composite consisting of two different glass compositions. Further, the present invention relates to a method of manufacturing a channel plate using this etching method. More specifically, it relates to a method for producing a channel plate, which comprises selectively eluting the core glass with an acid from a channel plate precursor composed of a core glass and a clad glass. As the channel plate, for example,
Micro channel plate for secondary electron multiplier (MC
P), and the method of the present invention is a useful method in its production.

[0002]

2. Description of the Related Art For producing an MCP by forming a bundle of clad glass fibers from a core glass which is easily soluble in an acid solution and a clad glass which is insoluble, it is disclosed in US Pat. No. 4,629,486. It is described in JP-A-4-228449 and the like. The MCP is a thin wafer having a structure in which tubes having an inner diameter on the order of microns are arranged in parallel and bundled, and amplifies secondary electrons. This plate is used for X-ray, ion or electron amplification. They are an important part of various electronic devices including night-vision cameras, photomultiplier tubes, streak cameras. The principles of manufacture and operation of microchannel plates are well documented in numerous documents and patents. The manufacturing process which is often used at present is JP-A-4-3.
Details are described in US Pat. No. 3,174,1 (US Pat. No. 4,629,486) and US Pat. No. 4,112,170. The former relates to alkaline lead silicate clad glass and the latter relates to barium borosilicate core glass.

According to the methods described therein, a rod of acid-acceptable core glass is inserted into a tube of clad glass having relatively good acid resistance, fused, and then stretched. These are bundled to form a composite bundle, which is fusion-sealed. The bundle is then stretched, cut to length, re-bundled and further stretched. By bundling these and fusion-sealing, a composite is obtained in which a continuous matrix of clad glass covers a large number of independent acid-labile core glasses. Next, the processed composite having a predetermined thickness is immersed in an aqueous solution of hydrochloric acid or nitric acid of about 1N to remove the core glass. This leaves a cladding glass structure with channels corresponding to the size of the core. The inner diameter of the channel can be about 10 microns. The perforated plate thus produced is then heated in a hydrogen-containing atmosphere to form a surface layer of reduced lead metal on the inner walls of the channels. The conventional MCP is manufactured as described above.

[0004]

Lead silicate glass has been often used as a cladding glass for MCP, but these glasses have low secondary electron emission ratio stability and effective life. There are problems such as short. On the other hand, there is V ₂ O ₅ —P ₂ O ₅ based electron conductive glass (see US Pat. No. 3,910,796) as a glass that may replace the lead reduced glass. This glass also has a large secondary electron emission ratio, and the stability of secondary electron emission is extremely superior to that of the conventional lead silicate glass. However, the etching rate of such vanadium phosphate glass with hydrochloric acid or nitric acid aqueous solution is orders of magnitude higher than that of conventional lead silicate glass, and the thermal characteristics are also different from those of lead silicate glass. Therefore, in the production of MCP using the above vanadium phosphate-based glass, when barium borosilicate-based glass was conventionally used as the core glass, although there are glasses having thermal characteristics that are suitable for etching, Due to the low velocity, it is difficult to manufacture MCPs with a sufficiently large channel length / inner diameter ratio.

The inventors of the present invention found a patent application for a core glass composition having a sufficient etching rate ratio for such a vanadium phosphate clad glass (Japanese Patent Application No. 6-88328). However, if the previously reported soluble core glass can be used as it is, the range of selection in terms of thermal properties and the like will be greatly expanded. For example, in U.S. Pat. No. 4,112,170, 38-64% BaO on a mole percent,
0-17% CaO, 0-3% MgO, 8-45% B 2 O
₃ , 6-34% SiO ₂ (however, the total amount of B ₂ O ₃ + SiO ₂ is 32-51%), 0-12% Al ₂ O ₃ , 0-
7% ZrO ₂ , 0-10% TiO ₂ , 0-3.5% Na
A barium borosilicate-based soluble core glass having a composition of ₂ O, 0-4% ZnO is described.

The thermal characteristics of these glasses are compatible with those of the above vanadium phosphate-based clad glass, but the etching rate with hydrochloric acid or nitric acid aqueous solution is 0.42 to 19
Too small in the range of mg · cm ⁻² · min ⁻¹ .

Therefore, it is an object of the present invention to provide a method for selectively etching one glass from a glass composite consisting of two different glass compositions such as a channel plate precursor at a relatively high rate. To do.

Still another object of the present invention is to utilize the above etching method to selectively etch the core glass from the channel plate precursor at a relatively high speed,
It is to provide a method of manufacturing a channel plate.

In addition, an object of the present invention is to manufacture a channel plate using etching that can reduce the etching rate of the vanadium phosphate-based clad glass without impairing the large etching rate of the barium borosilicate-based core glass. To provide a method.

[0010]

In order to increase the ratio of etching rates of two kinds of glass having different compositions, the present inventor has conducted various test studies. As a result, for example, a channel plate precursor, which is an assembly of a large number of double structures composed of a core glass easily soluble in an acid solution as an etching solution and an insoluble clad glass, is included in the clad glass. The present invention has been completed by finding that the above object can be achieved by previously adding the same component as the above-mentioned component or a component equivalent thereto to the acid solution.

In the present invention, the content of the network modifying oxide is 30.
A method of preferentially etching the glass B by immersing a glass composite composed of a glass A having a content of mol% or less and a glass B having a content of a network modifying oxide of 45 mol% or more in an aqueous acid solution. At least one selected from the group consisting of metal ions that form a network-modifying oxide, metal ions that form an intermediate oxide, and borate ions in the aqueous acid solution.
The present invention relates to the above-mentioned method (hereinafter referred to as the etching method of the present invention) characterized by containing a species of ions.

Furthermore, the present invention provides a channel plate precursor comprising a clad glass having a content of the network modifying oxide of 30 mol% or less and a core glass having a content of the network modifying oxide of 45 mol% or more. A method for producing a channel plate, which comprises immersing in an aqueous solution to preferentially etch the core glass, and heat treating the precursor having the obtained channel to form a surface layer on the inner wall of the channel, The above-mentioned production method, wherein the aqueous acid solution contains at least one ion selected from the group consisting of metal ions forming a network-modifying oxide, metal ions forming an intermediate oxide, and borate ions (channel plate Manufacturing method).

The etching method of the present invention will be described below. In the etching method of the present invention, a glass composite comprising a glass A having a content of a network modifying oxide of 30 mol% or less and a glass B having a content of a network modifying oxide of 45 mol% or more is added to an acid aqueous solution. The glass B is immersed and preferentially etched.

In the present invention, the oxides constituting the glass are classified into a network modifying oxide, a network forming oxide and an intermediate oxide. This classification is KHSun., Journal of America
n Ceramics Society, vol.30, p277 (1947). That is, the dissociation energy required to completely disassociate 1 mol of oxide MO _{y / x} is E _D (kca
l), where the oxygen coordination number of the M atom is n, the strength ε of the MO single bond is represented by the following formula. _{ε = E D / n (kcal} / mol) and, epsilon is a network-forming oxide of an oxide of more than 80 kcal / mol, epsilon is the network modifier oxide an oxide of less than 60 kcal / mol, epsilon is 60 kcal / mol or more 80k
Oxides less than cal / mol are classified as intermediate oxides.

The glass A having a content of the network modifying oxide of 30 mol% or less contains 70 mol% or more of the network forming oxide and / or the intermediate oxide. Further, the glass B having a content of the network modifying oxide of 45 mol% or more contains 55 mol% or less of the network forming oxide and / or the intermediate oxide. The glass A preferably has a content of the network modifying oxide of 20 mol% or less, and the glass B preferably has a content of the network modifying oxide of 50 mol% or more.

Examples of the network modifying oxides include alkali metal oxides, alkaline earth metal oxides, zinc oxide, lanthanum oxide, yttrium oxide and the like. Examples of the intermediate oxide include aluminum oxide,
Zirconium oxide, titanium oxide, lead oxide, iron oxide,
Tungsten oxide etc. can be mentioned. Examples of the network modifying oxide include silicon dioxide, boron oxide, diphosphorus pentoxide, vanadium pentoxide, arsenic oxide, antimony oxide, bismuth oxide and the like.

The glass A is expressed in mol%, SiO ₂ : 0 to 60% P ₂ O ₅ : 0 to 75% MgO: 0 to 30% CaO: 0 to 30% BaO: 0 to 30% ZnO: 0~30% MgO + CaO + SrO + BaO + ZnO: 0~30% PbO: 0~20% V 2 O 5: 0~50% WO 3: 0~50% Fe 2 O 3: 0~30% Bi 2 O 3: 0~ A glass having a composition of 10% Al ₂ O ₃ : 0 to 10% can be mentioned.

The glass B is expressed in mol%, SiO ₂ : 10 to 42% B ₂ O ₃ : 10 to 50% P ₂ O ₅ : 0 to 40% K ₂ O: 0 to 5% MgO : 0~6% CaO: 0~25% SrO : 0~30% BaO: 20~48% ZnO: 0~10% La 2 O 3: 0~10% Y 2 O 3: 0~10% Al 2 O ₃ : 0-9% ZrO ₂ : 0-5% TiO ₂ : 0-10% SiO ₂ + B ₂ O ₃ + P ₂ O ₅ : 40-60% K ₂ O + MgO + CaO + SrO + BaO + ZnO + L
₂ O ₃ : 40 to 60% Y ₂ O ₃ + Al ₂ O ₃ + ZrO ₂ + TiO ₂ : 0 to 10
% Of glass.

In the etching method of the present invention, there is no limitation on the shape, structure, size, etc. of the glass composite body consisting of the glasses A and B. For example, it can be the channel plate precursor described below. The acid contained in the acid aqueous solution used for etching is also not particularly limited. However, considering the etching rate, workability, etc., it is appropriate to use an inorganic acid such as hydrochloric acid, nitric acid, or sulfuric acid. Also,
The concentration of these acids and the temperature of the acid aqueous solution are not particularly limited and can be appropriately determined in consideration of the etching rate and the like. However, practically, the range is 0.1 to 12 mol / l for hydrochloric acid, 0.1 to 16 mol / l for nitric acid, and 0.1 to 18 mol / l for sulfuric acid.

A feature of the present invention is that the aqueous acid solution contains at least one ion selected from the group consisting of a metal ion forming a network-modifying oxide, a metal ion forming an intermediate oxide, and a borate ion. Is. Examples of metal ions constituting the network-modified oxide include alkali metal ions, alkaline earth metal ions, zinc ions, lanthanum ions, yttrium ions, and the like. In addition, examples of the metal ions forming the intermediate oxide include aluminum ions, zirconium ions, lead ions, titanium ions, iron ions, and tungsten ions. In the etching method of the present invention,
Preferably, the aqueous acid solution is selected from the group consisting of metal ions forming the network-modifying oxide contained in the glass A forming the glass complex to be etched, metal ions forming the intermediate oxide, and borate ions. At least 1
Contains seed ions.

One or more of these ions are added to the aqueous acid solution. The concentrations of these ions in the acid aqueous solution can be appropriately determined in consideration of the type of ions, the etching rate, and the like. For example, it is in the range of 0.05 mol / liter to 1 mol / liter. Further, these ions can be added to the aqueous acid solution as acid salts (inorganic acid salts, organic acid salts) and halides (for example, chlorides). However, in the case of borate ion, boric acid or a boric acid compound can be used.

In the present invention, the glass B constituting the glass composite can be preferentially etched by immersing the glass composite in the acid aqueous solution. The immersion time can be appropriately determined in consideration of the degree of etching and the like.

Next, a method for manufacturing the channel plate of the present invention will be described. In the method for manufacturing a channel plate of the present invention, first, the channel glass precursor composed of the clad glass and the core glass is immersed in an aqueous acid solution to preferentially etch the core glass. Here, the clad glass is a glass having a content of the network modifying oxide of 30 mol% or less, and can be a glass having the composition exemplified in the glass A. Further, the core glass is a glass having a content of the network modifying oxide of 45 mol% or more, and the glass having the composition illustrated in the above-mentioned glass B can be used. More preferably, the clad glass is a glass having a content of the network modifying oxide of 30 mol% or less, and the core glass is a glass having a content of the network modifying oxide of 50 mol% or more.

The composition of the clad glass can be the same as the composition of the glass A described above. Particularly, preferred glass as a cladding glass, and displayed in a _{mole%, P 2 O 5: 30~75} % V 2 O 5: 10~45% WO 3: 0~45% Fe 2 O 3: 0~25% _{WO 3 + Fe 2 O 3:} 15~45% BaO: 0~15% PbO: 0~15% SiO 2: can be exemplified 0-15% vanadium phosphate type glass having the composition.

Further, as another glass preferable as the clad glass, it is expressed in mol%, P ₂ O ₅ : 40 to 50% V ₂ O ₅ : 15 to 30% WO ₃ : 10 to 25% BaO: 10 to 15 % SiO _2: mention may also be made 0-10% vanadium phosphate type glass having the composition.

On the other hand, the composition of the core glass is the same as the above glass A.
The composition shown in can be mentioned. Examples of preferable glass as the core glass include the glass described in US Pat. No. 4,112,170. This glass is then displayed in mol%, BaO: 38~64% CaO: 0~17% MgO: 0~3% B 2 O 3: 8~45% SiO 2: 6~34% ( however, B _{2 O 3 + SiO 2: 32~51%} ) Al 2 O 3: 0~12% ZrO 2: 0~7% TiO 2: 0~10% Na 2 O: from 0~4%: 0~3.5% ZnO It is a barium borosilicate glass having the following composition.

The channel plate precursor of the present invention is
For example, it may be that described in US Pat. No. 4,112,170. This channel plate precursor is manufactured as follows. A core glass rod is inserted into a tube of clad glass, fused and then stretched, and then bundled to form a bundle of composites, which are fused and sealed. The bundle is then stretched, cut to length, re-bundled and further stretched. By bundling these and fusion-sealing, a channel plate precursor which is a composite in which a continuous matrix of clad glass covers a large number of independent core glasses is obtained.

The shape, structure, dimensions, etc. of the channel plate precursor used in the manufacturing method of the present invention are not particularly limited. The channel plate precursor can be obtained by immersing it in an aqueous acid solution to preferentially etch the core glass to remove the core glass portion, thereby obtaining a channel plate. The type and amount of the acid contained in the acid aqueous solution for etching used here are the same as those in the etching method of the present invention. Furthermore, the above-mentioned aqueous acid solution contains at least one ion selected from the group consisting of metal ions forming the network-modifying oxide, metal ions forming the intermediate oxide, and borate ions, and in particular, treatment It is preferable to include the ions that form the cladding glass that forms the target channel plate precursor.

The mechanism by which the erosion of the cladding glass of the channel plate precursor is suppressed and the core glass is selectively eroded will be outlined below. This mechanism is also common to the mechanism in the previous etching method. In the process of erosion of the glass used as the channel plate precursor by the acid solution, the following reactions occur first. (M−O ⁻ ) nR ^{n +} (glass) + nH ⁺ (solution) → (M
-OH) n (glass) R ^{n +} represents a metal ion modifying the network structure of the glass, such as an alkali metal ion or an alkaline earth metal ion, which undergoes ion exchange with a proton in the solution, thereby The metal ions are eluted, and only the skeleton structure of glass mainly composed of the network-forming oxide (M in the formula is an element constituting the network-forming oxide) remains on the glass surface. This surface layer serves as a protective film that hinders erosion, and as the thickness increases, the elution rate of the ions of the alkali metal and the like decreases. Next, the eluted metal ions act on the cross-linking structure of the glass-forming oxide forming the skeleton structure of the glass surface layer, and break the bond at that portion. This reduces the degree of polymerization of the glass-forming oxide and facilitates its dissolution in the acid solution.

On the other hand, the basic technical idea of the present invention is that in the ion exchange reaction that occurs in the initial stage of the erosion process, the same or equivalent metal ion eluted in the solution is previously added to the solution. In addition, the equilibrium of the ion exchange reaction is tilted to the left to make this ion exchange reaction less likely to occur, thereby reducing the etching rate of the cladding glass and the like.

On the other hand, the mechanism of acid erosion of the easily soluble acid core glass used for manufacturing the channel plate is different from the acid erosion mechanism of the clad glass. The acid-soluble core glass contains less than about 60 mol% of glass-forming oxides such as SiO ₂ and B ₂ O ₃ and 40 mol% or more of network structure modifying oxides. In such a glass, not only the metal ions that modify the glass skeleton are eluted, but all the glass that is in contact with the acid solution is dissolved in the liquid, and a protective film that prevents erosion is formed on the glass surface. Not formed at all. Therefore, in the easily soluble acid core glass, even if the same component as the component contained in the glass or a component equivalent thereto is added to the acid solution in advance, the effect of buffering the etching is not observed.

As described above, a channel plate can be obtained by using the selective etching method of the present invention. If desired, this channel plate is heat-treated to form a surface layer on the inner wall of the channel. You can also

[0033]

EXAMPLES The present invention will be further described below with reference to examples.

Example 1 Barium chloride, barium nitrate, barium acetate, strontium chloride, calcium chloride, magnesium chloride, lead nitrate, zinc chloride, sodium vanadate, in 1N hydrochloric acid,
Boron oxide and sodium metaphosphate are dissolved, and each of barium ion, strontium ion, calcium ion, magnesium ion, lead ion, zinc ion, vanadate ion, borate ion, and phosphate ion is dissolved in 0-0.
The etching liquid contained at a concentration of 2 mol / liter was adjusted. Using this etchant, 20V ₂ O ₅ -15
_{WO 3 -15BaO-45P 2 O 5} -5 SiO 2 (m
By etching the glass A made of ol%) at 30 ° C. for 6 hours, the etching rate was reduced as compared with the case of etching with 1N hydrochloric acid in which the additive was not dissolved. Table 1 shows the relationship between the etching rate thus obtained and the concentration of the salt dissolved in the etching solution.

The etching rate was determined as follows. A glass sample having 6 sides polished to 10 × 10 × 10 mm was washed with alcohol, dried and then weighed. Soak the glass sample in the etching solution,
After etching under the above conditions, the sample was taken out of the solution, washed again, dried, and weighed, and the etching rate was calculated using the following formula. ER = 2 (W1-W2) / t (S1 + S2) where ER is the etching rate, W1 and W2 are the weights of the sample before and after etching, t is the etching time, and S1 and S2 are the surface areas of the sample before and after etching, respectively. Is.

[0036]

[Table 1]

Example 2 Barium chloride and barium nitrate were dissolved in 1N nitric acid,
An etching solution containing barium ions at a concentration of 0 to 0.2 mol / liter was prepared. Using this etching solution, 20V ₂ O ₅ -15WO ₃ -15BaO-45P
₂ O ₅ -5SiO ₂ 3 Glass A comprising (mol%)
By performing the etching at 0 ° C. for 6 hours, the etching rate was reduced as compared with the case of etching the glass with 1N nitric acid that did not dissolve the glass. Table 2 shows the relationship between the etching rate thus obtained and the concentration of barium salt dissolved in the etching solution.

[0038]

[Table 2]

Example 3 Barium chloride was dissolved in 1N hydrochloric acid to prepare an etching solution containing barium ions at a concentration of 0 to 0.2 mol / liter. Using this etching solution, 20Si
_{O 2 -32B 2 O 3 16CaO-} 16SrO-16Ba
By etching the glass B made of O (mol%) at 30 ° C. for 0.5 hour, the etching rate was hardly changed as compared with the case of etching the glass with 1N hydrochloric acid in which the glass was not dissolved. Table 3 shows the relationship between the etching rate thus obtained and the concentration of barium chloride dissolved in the etching solution.

[0040]

[Table 3]

Example 4 20SiO ₂ -32B ₂ O ₃ -16CaO-16SrO
−16BaO (mol%) core glass and 20V
₂ O ₅ -15WO ₃ -15BaO-45P ₂ O ₅ -5S
The ratio of the etching rates when 0 to 0.15 mol / liter barium chloride was added to 1N hydrochloric acid of the cladding glass made of iO ₂ (mol%) was obtained. The results are shown in Figure 1.
Shown in As shown in FIG. 1, the ratio increased as the amount of barium chloride added increased.

Example 5 20SiO ₂ -32B ₂ O ₃ -16C used in Example 4
aO-16SrO-16BaO core glass consisting (mol%) and _{20V 2 O 5 -15WO 3 -15BaO-} 4
A channel plate precursor was produced by the method described in US Pat. No. 4,112,170 using a clad glass made of 5P ₂ O ₅ -5SiO ₂ (mol%).

The structure and dimensions of the channel plate precursor are as follows. The inner diameter of the channels (channel diameter) is 25 microns, the distance between the centers of the channels (channel pitch) is 32 microns, and the plate thickness is 1.25 mm. The above channel plate precursor was immersed in an aqueous solution in which 0.1 mol / liter barium chloride was dissolved in 1N hydrochloric acid at 30 ° C. for 25 minutes to dissolve and remove the core glass portion to prepare a channel plate. The channel plate obtained above had an electron multiplication factor of about 10 ⁴ at an applied voltage of 1 kV.

[0044]

INDUSTRIAL APPLICABILITY The etching method of the present invention is generally applicable to glass. For example, by applying it to vanadium phosphate-based clad glass and barium borosilicate-based core glass used in MCP, the etching rate of the clad glass is reduced. On the other hand, since the etching rate of the core glass is hardly changed, the ratio of the two etching rates can be increased to several times to several tens of times. Therefore, according to the method of the present invention, it is also possible to manufacture an MCP having a high multiplication gain and a sufficiently large channel length / inner diameter ratio.

[Brief description of drawings]

FIG. 1 shows the concentration of barium chloride dissolved in 1N hydrochloric acid and 20SiO ₂ -32B ₂ O ₃ 16CaO-16SrO.
−16BaO (mol%) core glass and 20V
₂ O ₅ -15WO ₃ -15BaO-45P ₂ O ₅ -5
It is a graph showing the relationship between the ratio of the etching rate of the cladding glass consisting of SiO ₂ (mol%).

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H01J 43/24

Claims (13)

[Claims] 1. A glass composite comprising a glass A having a content of a network modifying oxide of 30 mol% or less and a glass B having a content of a network modifying oxide of 45 mol% or more is immersed in an aqueous acid solution. A method of preferentially etching the glass B, wherein the acid aqueous solution is a metal ion forming a network-modifying oxide,
The above method, which comprises at least one ion selected from the group consisting of a metal ion and a borate ion constituting an intermediate oxide. 2. The aqueous acid solution contains at least one ion selected from the group consisting of a metal ion forming a network-modifying oxide contained in glass A, a metal ion forming an intermediate oxide, and a borate ion. The method according to item 1. 3. The metal ion constituting the network-modified oxide is an ion selected from the group consisting of an alkali metal ion, an alkaline earth metal ion, a zinc ion, a lanthanum ion and yttrium, and a metal constituting an intermediate oxide. The ion is an ion selected from the group consisting of aluminum ion, zirconium ion, titanium ion, lead ion, iron ion and tungsten ion.
Or the method described in 3. 4. The method according to claim 1, wherein the aqueous acid solution contains one or more of hydrochloric acid, nitric acid and sulfuric acid. 5. A clad glass having a content of the network modifying oxide of 30 mol% or less and a content of the network modifying oxide of 4 or less.
A method for manufacturing a channel plate, comprising a step of preferentially etching the core glass by immersing a channel plate precursor composed of 5 mol% or more of the core glass in an acid aqueous solution, wherein the acid aqueous solution is a network-modified oxide. Metal ions that compose things,
The above-mentioned manufacturing method, which comprises at least one ion selected from the group consisting of metal ions and borate ions constituting the intermediate oxide. 6. The aqueous acid solution contains at least one ion selected from the group consisting of metal ions forming a network-modifying oxide contained in the clad glass, metal ions forming an intermediate oxide, and borate ions. Item 5. The method according to Item 5. 7. The metal ion constituting the network-modified oxide is an ion selected from the group consisting of alkali metal ions, alkaline earth metal ions, zinc ions, lanthanum ions and yttrium, and the metal constituting the intermediate oxide. 6. The ion is an ion selected from the group consisting of aluminum ion, zirconium ion, titanium ion, lead ion, iron ion and tungsten ion.
Or the manufacturing method according to 6. 8. The production method according to claim 5, wherein the aqueous acid solution contains one or more of hydrochloric acid, nitric acid and sulfuric acid. 9. Clad glass expressed in mol% SiO ₂ : 0 to 60% P ₂ O ₅ : 0 to 75% MgO: 0 to 30% CaO: 0 to 30% BaO: 0 to 30% ZnO: 0~30% MgO + CaO + SrO + BaO + ZnO: 0~30% PbO: 0~20% V 2 O 5: 0~50% WO 3: 0~50% Fe 2 O 3: 0~30% Bi 2 O 3: 0~10% al ₂ O _3: the method according to any one of claims 5-8 consisting of 0-10% of the composition. 10. Clad glass expressed in mol% P ₂ O ₅ : 30 to 75% V ₂ O ₅ : 10 to 45% WO ₃ : 0 to 45% Fe ₂ O ₃ : 0 to 25% WO _{3 + Fe 2 O 3: 15~45%} BaO: 0~15% PbO: 0~15% SiO 2: any of claims 5 to 8 0 to 15% of the vanadium phosphate glass having the composition The manufacturing method described in. 11. The clad glass is expressed in mol%, P ₂ O ₅ : 40 to 50% V ₂ O ₅ : 15 to 30% WO ₃ : 10 to 25% BaO: 10 to 15% SiO ₂ : 0. The manufacturing method according to any one of claims 5 to 8, which is a vanadium phosphate-based glass having a composition of -10%. 12. The core glass is expressed in mol%. SiO ₂ : 10 to 42% B ₂ O ₃ : 10 to 50% P ₂ O ₅ : 0 to 40% K ₂ O: 0 to 5% MgO: 0 ~6% CaO: 0~25% SrO: 0~30% BaO: 20~48% ZnO: 0~10% La 2 O 3: 0~10% Y 2 O 3: 0~10% Al 2 O 3: _{0~9% ZrO 2: 0~5% TiO} 2: 0~10% SiO 2 + B 2 O 3 + P 2 O 5: 40~60% K 2 O + MgO + CaO + SrO + BaO + ZnO + L
₂ O ₃ : 40 to 60% Y ₂ O ₃ + Al ₂ O ₃ + ZrO ₂ + TiO ₂ : 0 to 10
The manufacturing method according to any one of claims 5 to 11, which has a composition of 5%. 13. The core glass is expressed in mol% BaO: 38 to 64% CaO: 0 to 17% MgO: 0 to 3% B ₂ O ₃ : 8 to 45% SiO ₂ : 6 to 34% (however, _{, B 2 O 3 + SiO 2} : 32~51%) Al 2 O 3: 0~12% ZrO 2: 0~7% TiO 2: 0~10% Na 2 O: 0~3.5% ZnO: 0~ The manufacturing method according to any one of claims 5 to 11, which is a barium borosilicate glass having a composition of 4%.