JPH042629A - Silver-containing phosphate glass - Google Patents

Abstract

PURPOSE:To enable use of a nitrate as an ion exchange molten salt without any coloring or devitrifying with silver colloids in a melting process by incorporating P2O5, GeO2, B2O3, Ag2O and Na2O in a specific proportion in glass. CONSTITUTION:With 10-35mol% P2O5, are mixed 10-55mol% GeO2, 5-60mol% B2O3, 3-15mol% Ag2O and 3-27mol% Na2O so as to provide (GeO2-P2O5)<=20mol% and 6mol%<=(Ag2O+Na2O+Li2O+K2O)<=30mol%. The resultant mixture is then heated and melted at 1000-1300 deg.C for 3-4hr.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a glass composition suitably used for a gradient index lens.

[Conventional technology]

It is known that transparent cylindrical bodies whose refractive index varies continuously from the central axis towards the circumferential surface, preferably decreasing parabolically, exhibit lens action.

As a method for manufacturing this refractive index gradient type glass lens, for example, Japanese Patent Publication No. 17605/1983 discloses that a glass rod containing thallium is brought into contact with a source of alkali metal ions, such as nitrate containing sodium or potassium, and the glass rod is A method is described in which thallium ions closer to the surface are replaced with more alkali metal ions to obtain the required refractive index gradient. This gradient index lens has thallium as a distribution forming component, so it has large chromatic aberrations.
Suitable for use with single wavelength light, but not suitable for use with white light.

Japanese Patent Publication No. 5G-125632 describes a method for manufacturing a gradient index lens in which a glass rod containing lithium ions is ion-exchanged in sodium nitrate. A gradient refractive index lens with a concentration distribution of lithium ions has the advantage of having smaller chromatic aberration than a lens using thallium ions, but has the disadvantage that the difference in refractive index between the center of the lens and the peripheral surface is small.

In order to compensate for the drawbacks of these two types of gradient index lenses, Japanese Patent Publication No. 100451/1983 proposes a method for manufacturing a gradient index lens having a concentration distribution of silver ions. In general, silver ions tend to turn into colloids, and in order to suppress this, the patent proposes a glass composition containing a large amount of phosphoric acid.

[Problem that the invention seeks to solve]

However, according to research conducted by the present inventors, glass containing a large amount of phosphoric acid has problems such as reacting with nitrates during ion exchange treatment and producing devitrification on the glass surface, or the glass itself dissolving into molten salt. It was confirmed that there is. Further, salts other than nitrates, such as molten salts of sulfates and halides, are highly corrosive to metals and glass, and there are many problems such as difficulty in obtaining containers suitable for holding molten salts.

The present invention provides a glass composition for a gradient refractive index lens that allows the use of vitreous salt as a molten salt for ion exchange without causing coloration or devitrification due to silver colloid during the melting process of the glass.

[Means for solving problems]

The two problems mentioned above, the formation of colloidal silver and the reaction between glass and nitrates, are both related to Pros in glass.

That is, to prevent the formation of silver colloid, it is effective to add P2O5, but on the other hand, to suppress the reaction with nitrates, P2O5 must be reduced. As a result of intensive research into these problems, the present inventors found that P2O
It has been found that the problem can be solved by substituting 5 with GeO2 or B2o3 within a certain range and adding an appropriate oxide as necessary. Specifically, the above problem is solved by using the following glass composition.

The composition range is PpOs 10-35 GeO210-55 8203 5-60 ^g203-15 Na20 3-27 in terms of mol%, and the range is Ge02-P2O5≦20 6≦Ag2O+Na2O+Li2O+[20≦30. Preferably, P2O5Is~30 Ge02 13~50 8203 10~55 Ag20 S~ 13 Na20 3~23 Li20 0~1O X200~1O Nb20s O~ 10 SrOO~10 BaOO~10^1203 0~1O Ga2030~ 15 W030~8 Ti02 is in the range of 0 to 10.

The reasons for limiting the composition in the present invention are as follows.

P2O5 is a glass-forming oxide and is highly effective in suppressing the production of silver colloid. Therefore, 10 days ago. If the composition is less than 1%, devitrification tends to occur during the glass melting process or ion exchange treatment process, and the effect of suppressing the production of silver colloids cannot be sufficiently obtained. 35 Otori 01
If the composition exceeds %, it reacts with nitrate during ion exchange and devitrification occurs on the glass surface. In addition, chemical durability also decreases. Therefore, the composition range of P2O5 is 10-35
(2)oH, preferably l5=30so1%.

GeO2 is also a glass-forming oxide that strengthens the network structure and improves the chemical durability of the glass. Therefore, G
If the content of eO2 is less than 1% (lso1%), the chemical durability will be significantly reduced and it will not be suitable for practical use.On the other hand, GeO2 has no effect of suppressing the colloidalization of silver, and
A composition containing 55 ■o1% or more of ene tends to generate silver colloid. In addition, compositions containing a large amount of GeO2 tend to devitrify, and the component that most affects the occurrence of devitrification is P2O.
It is 5. The conditions that do not cause devitrification are GeO2-P20
B≦201101%. For this reason, GeO255
(2) When o1% or more, P2O5 must be contained at 351o1% or more, which makes it easier to react with nitrates. Therefore, the composition range of GeO2 is 10 to 1%, preferably 13 to 50 1%.

Although B2O3 is inferior to P 20 s, it is effective in suppressing the generation of silver colloid. Also, it does not react with nitrates. Therefore, by replacing it with P 20 s, it is possible to suppress the reaction with nitrate while preventing the production of silver colloid. Furthermore, P2O5-GeO2-B203-R20
By introducing B2O3 into the (R20: Ag2O, Na2O, etc.) system, the vitrification range is expanded and the meltability is improved.

When the composition is less than 1% B2O35++o, the vitrification range becomes narrow, and devitrification and phase separation are likely to occur during the glass melting process and ion exchange process. If it exceeds 60 1%, the proportion of P2O5 that can be added decreases, and the effect of suppressing the production of silver colloid becomes insufficient. , weather resistance also deteriorates.

Therefore, its composition range is 5 to 60 ■o1%,
Preferably it is 10 to 55 mof.

Ag2O is a component that increases the refractive index and forms a refractive index distribution. If the composition is less than 1% by Ag2O3 mo, a sufficient refractive index difference cannot be obtained, and the advantages of a gradient index lens cannot be exhibited. If the content is 15+so1% or more, silver colloid is likely to be produced. Therefore, the range in which Ag2O can be added is 3 to 15 mo1%, preferably 5 to 13 mo1%.
■o1%.

Na2O coexists with AgaO and other alkali metal oxides to cause a mixed alkali effect, thereby increasing resistance to devitrification during the melting process and ion exchange process. To obtain this effect, it is necessary to add a small amount of Na2O (more than 3 haze oH). However, if the total amount of Ag2O and alkali metal oxide exceeds 30 o1%, the chemical durability of the glass will deteriorate. 2) The limit for the content of Na2O is 1%. Therefore, the content of Na2O is 3~27■o
H, preferably 3 to 23 1%.

Further, by adding NaeO to the glass together with Ag2O, the shape of the refractive index distribution can be controlled.

Like Na2O, Li2O, [20] is useful for improving the devitrification resistance of glass and controlling the refractive index distribution, but when its content increases, the glass becomes more likely to devitrify, so Na2O should not be added. I can't. The range in which they can be added is 0 to 10 oil.

NbzOs has the effect of preventing colloidal formation of silver and suppressing the reaction with nitrate, but 1O■. If 1H2j is added above, the meltability deteriorates, and undissolved matter and devitrification are likely to occur. Therefore, the Nb2O5 content is 0 to 1.
The amount is 0mol%, preferably 0 to 1mol%.

SrO and BaO suppress the reaction between nitrate and glass and improve devitrification resistance. However, if 1% or more of 10 haze is added, silver colloid will be more likely to be produced. Therefore, the composition range is 0-10%, preferably 0-1%.

Al2O3 and Ga2O3 are intermediate oxides that enter the network structure of the glass and strengthen the structure of the glass.

Therefore, it has effects such as improved chemical durability. However, A12's lomof! Above, Ga20a
A composition containing 1% or more of 35■o has poor melting properties and tends to be undissolved or devitrified. Therefore, its composition range is A
0 to lomo1% for l2O3, 0 to 15 for Ga21s
o1%, preferably O~7so1% in Al2O3
, 0 to 10 ■o1% for Ga2es.

WOs has the effect of suppressing the production of silver colloid and the effect of improving the corrosion resistance and devitrification resistance against nitrates. However, compositions containing 11038 mo1% or more tend to cause devitrification during the process of melting the glass. Therefore, its composition range is 0 to 8 vol., preferably 0 to 6 vol.
%.

TiO2 has the effect of suppressing the reaction between glass and nitrates, but if it is included in the glass in an amount exceeding 1% of 1O2O, silver colloids are likely to be produced and devitrification is likely to occur. Therefore, the content of TlO2 is 0 to 10%, preferably 0 to 1%. It is 1%.

〔Example〕

Example No. 1-13 and Comparative Example No. in Table 1
, 1-4 will be taken as an example to explain the specific effects of the present invention.

! Raw materials for each oxide shown in the glass composition in Table 1 include phosphorus pentoxide, germanium oxide, boron oxide, silver nitrate, sodium nitrate, lithium nitrate, potassium nitrate, niobium oxide, strontium carbonate, barium carbonate, aluminum phosphate, and oxide. Special grade reagents of gallium, tungstic acid, and titanium oxide were used.

A predetermined amount of these raw materials is thoroughly mixed in an alumina mortar,
A formulation was obtained. The formulation was made using an alumina crucible,
It was melted in an electric furnace at 0 to 1300°C for 3 to 4 hours. After stirring well and homogenizing the glass, pour it into a metal frame.
It was slowly cooled to room temperature over about a day to obtain a nearly colorless and transparent glass.

Each glass was cut into 15 x 20 x 7 mm and polished to a mirror surface to prepare a sample for ion exchange.

Each sample was subjected to ion exchange treatment using sodium nitrate under the conditions of "ion exchange temperature" and "ion exchange time" in Table 1. However, for samples in which devitrification was produced during ion exchange, such as the composition of the comparative example, the time at which devitrification was observed was recorded in the "ion exchange time" column.

The "state after treatment" refers to the state of the glass at the time the ion exchange treatment is completed. In the table, the symbol in this column is 0:
The surface condition is the same as before the ion exchange treatment, and no devitrification due to the reaction between the glass and the molten nitrate is observed.

O: The condition is the same as before the grain treatment, but there is slight clouding on the surface.

Δ: Slight evidence of reaction with nitrates is observed, and clear cloudiness is observed on the glass surface.

×: There is a clear reaction between the glass and the nitrate, and the entire glass surface becomes white and devitrified, and in severe cases, the sample does not retain its original shape.

represents.

In Table 1, "rnd" and "vd" respectively represent the refractive index and Abbe number at the d-line of the base glass.

"Δn" represents the difference in refractive index between the central portion and the peripheral surface portion of the glass obtained by ion exchange treatment.

Example 1 shows that the mole % TeP2ss 10. GeO220,
The composition is B20350, Ag2O10, and Na2O10. This composition was melted in the manner described above to obtain a colorless and transparent glass. This was ion-exchanged in molten sodium nitrate at 420'C for up to 4 days. No devitrification substances or cloudiness were observed on the glass surface of the sample after the treatment. Further, ion exchange treatment was carried out at 450'C, but almost no devitrification was observed on the glass surface after 4 days of treatment. The difference in refractive index of the glass body after the ion exchange treatment was approximately 0.062. The dispersion of the glass is also relatively small.

Examples 2.5.6 have a composition containing a large amount of P2O5.

Ion exchange treatment was performed under the same conditions as in Example 1.

Although it is slight compared to Example 1, cloudiness is observed on the glass surface. However, this does not pose a problem in practice.

Example 8.9 contains a large amount of P2O5 and
It has a composition containing a large amount of monovalent cation components such as Na20.

Although cloudiness is observed on the glass surface after ion exchange, no deformation of the glass body is observed, and there is no problem in practical use.

Ion exchange using nitrate was similarly possible in other Examples, and glass bodies with relatively large differences in refractive index could be obtained.

On the other hand, the composition of Comparative Example 1.2 is the composition described in the example of silver-containing phosphate glass (Japanese Patent Publication No. 62-100451) described in the "Prior Art" section. Glasses were obtained from these compositions in the same manner as in this example, and subjected to ion exchange treatment with sodium nitrate.

However, even though the same ion exchange temperature as in Example 1 was used, the glass surface became white and devitrified in 3 hours, and when the ion exchange treatment was continued, the devitrification progressed inside the glass, and the devitrification progressed inside the glass. It did not retain its original shape due to the dissolution of the transparent material into the molten salt.

Similarly, in Comparative Example 3.4, the entire glass surface became white and devitrified several hours after starting the ion exchange treatment, and the glass body did not retain its original shape due to the dissolution of the devitrification.

Table 1 Table 1 Continued Table 1 Continued [Effects of the Invention] According to the present invention, nitrates can be used as molten salts for ion exchange without causing coloring or devitrification due to silver colloid during the glass melting process. This made it possible to easily produce a gradient refractive index lens with a relatively large difference in refractive index.

Claims (2)

[Claims] (1) Contains P_2O_510-35 GeO_210-55 B_2O_35-60 Ag_2O3-15 Na_2O3-27 as a main component in mol%, and GeO_2-P_2O_5≦205≦Ag_2O+Na_2O+Li_2O+K_2O≦
30.A silver-containing phosphate glass characterized in that it is (2) In claim 1, P_2O_5, GeO_
2. The content of each component of B_2O_3, Ag_2O, and Na_2O in mol% is within the range of P_2O_515-30 GeO_213-50 B_2O_310-55 Ag_2O5-13 Na_2O3-23, and if necessary, Li_2O0-10 K_2O0-10 Nb_2O_ 50~ 10 SrO0-10 BaO0-10 Al_2O_30-10 Ga_2O_30-15 WO_30-8 TiO_20-10 Silver-containing phosphate glass containing the following components.