JPS61201639A - Plate lens - Google Patents

Abstract

PURPOSE:To obtain the titled plate lens having excellent weather resistance and optical stability and having a large number of small-bore openings by integrally forming a lens part having an optical axis vertical to the surface of a substrate and variable refractive index distribution in the glass substrate consisting of components of specified composition. CONSTITUTION:As the essential components, 45-80%, by mol, SiO2, 8-35% alkali metal oxide, 2-20% ZnO, 0-8% B2O3, 0-7% Al2O3, 0-2% ZrO, 0-10% (CaO+BaO+MgO), etc., are melted at 1,250-1,500 deg.C, agitated, homogenized and then fed into a mold at 1,000-1,250 deg.C. The molded material is then annealed to obtain a glass plate which is used as a substrate 1. A metallic mask 4 provided with an opening 3 in circular form, etc., by a specified lens array pattern is applied on the one surface of the substrate 1. A molten salt contg. Tl ions and Ag ions is brought into contact with the surface of the mask 4, a DC voltage is impressed between both surfaces of the substrate, the ions 5 are exchanged with the monovalent ions in the glass through the opening 3 and a plate lens integrated with a lens 2 having gradient refractive indexes is obtained.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an integrally formed flat plate lens.

[Description of prior art]

Lens arrays, in which a large number of graded refractive index lenses are arranged in a plane, are used in the optical system of copying machines and semiconductor lasers. This lens has the same function as such a lens array, and can integrate a large number of extremely small lenses. A gradient refractive index lens 2 having a distribution that decreases from the optical axis toward the periphery and in an almost parapolitan shape in the optical axis direction is formed integrally with the substrate, and is a circular lens array as shown in FIG. Alternatively, there is a linear lens array as shown in FIG.

In order to manufacture the above-mentioned flat plate lens, as shown in FIG. 3 is applied with a metal masking mask provided with a predetermined lens array pattern, a molten salt containing cations such as Tl ions and Ag ions that greatly contribute to increasing the refractive index of glass is brought into contact with the mask surface, and a DC voltage is applied to both sides of the substrate. The above-mentioned ions in the molten salt are exchanged with the above-mentioned ions in the glass through the mask opening while applying an electric current or by natural diffusion, and a refractive index distribution corresponding to the concentration distribution of the ions diffused into the glass is formed in the substrate. let

For example, as a substrate glass for manufacturing a flat lens by the above-mentioned ion exchange method,
! ;3702 publication contains 5i0275.0% in mol%
+ B2O3/ 0.2%, Bad (7,7%, Na2
Glass with a composition of O9,6%* to 204(,r%)
BK-7 optical glass) is exemplified.

[Problem that the invention seeks to solve]

When a masked substrate glass is brought into contact with a molten salt as described above and a refractive index gradient lens is formed in the substrate by ion diffusion, the temperature of the molten salt is higher than g Because the immersion process is carried out over a long period of time, the substrate glass surface may be eroded by the molten salt, or substances may be generated on the glass surface due to slight compositional fluctuations in the base material glass or compositional fluctuations in the molten salt.
In some cases, there was a problem that the entire substrate glass was crystallized. When such devitrification or erosion occurs on the glass surface, ions tend to diffuse unevenly into the glass, making it impossible to obtain a lens with stable optical performance.

[Means for solving problems]

As a main component, 5io2:us-za0% (unit: mol%)
, below), alkali metal oxide (R20): Za~3
Phantom G r ZnO' 2~20 'IA + B 20
3' 0~Ir AJ 203' 0~7%, Zr
O: 0~r%, CaO+BaO+MgO: 0~10
% is used as a substrate glass for a flat lens. In addition to the above main components, S rOr P b O
t T 102 + L a 203 rSb203+
A small amount of additives such as AS20:s may be included.

Each component of the glass composition according to the present invention will be described in detail below. S102 is a component that forms the skeleton of the glass, and 75
If it is less than 0%, the durability and stability of the glass will decrease, and if it exceeds 0%, the melting temperature will rise, and the necessary amounts of other components will not be secured, making it impossible to obtain a lens with a large refractive index difference. It is necessary to set it within the range of 1 to 1 OtI, and more preferably within the range of 53 to 75%. B2O3
Adding molten glass makes it easier to melt the glass, but
If too much is added, striae may occur due to volatilization or deformation of the lens portion may occur due to ion exchange, so the content should be within the range of OS %. ZnO has a smaller effect on vitrification than other divalent modified oxides.

However, if it is less than 2%, the devitrification and durability of the glass will be poor, and if it exceeds 20%, the durability will be poor, so 2-JO
It is necessary to keep it within the range of 5% to 75%.
It is desirable to be within the range of . ZrO2 has a very large effect on improving the weather resistance of glass, but if it exceeds 2%, it tends to become insoluble, so its content ranges from 0 to 2%. AA! 203 has the same weather resistance as ZrO2,
It contributes to the improvement of molten salt resistance during ion exchange, but if it exceeds 7%, the solubility deteriorates, so it is necessary to keep it within the range of 0 to 7%. desirable.

CaO*MgO and BaO extend the range of vitrification and improve the durability of the glass, and can be contained in a total amount of 0 to 10%.

The most important glass component in the present invention is a monovalent alkali metal oxide (Rho). As mentioned above, in the method of manufacturing a flat lens using the ion exchange method, monovalent ions with relatively low electronic polarizability contained in the substrate glass and T
By partially exchanging ions with high electronic polarizability such as J ions and Ag ions, a refractive index distribution is formed in that part,
Alkali metal oxide (hereinafter abbreviated as R20) has a function as the above-mentioned exchange ion. If the R20 content is less than f%, the aperture angle (θ) of the formed lens will become small, making it impractical, and if the content exceeds 3j%, the durability of the glass will deteriorate rapidly, so the total amount of R20 is 1% to 3
It is necessary to be within a range of 5%, and a preferable range is 12^J, r%.

As for R, bi and ua are effective in increasing the maximum refractive index difference Δn of the lens, and considering the stress on the glass structure during exchange with Tl ions having a large ionic radius, Kl (38 is preferable. Therefore As for the substrate glass composition of the flat plate lens, it is desirable to contain one or more of L l m IJa and one or more of KIO3 within the above-mentioned total amount range.

As the glass composition according to the present invention, in addition to the above components, K Sr
One or more components selected from O, PbOI, TiO2t, La2O3 can be contained in a total amount of 5% or less. These components are effective in expanding the vitrification range and improving the solubility of glass, but if added in amounts exceeding the above range, ion exchange will be difficult to proceed smoothly.

Further, the glass according to the present invention may contain 5b2o3 or ASg03, which is used as a surface cleaning agent during glass melting, in a range of 0.003% or less.

〔Example〕

Silica powder, boric acid, zinc oxide, potassium carbonate, sodium carbonate, zirconium oxide, aluminum hydroxide, antimony oxide, or arsenous anhydride are used as raw materials for each composition shown in Table 1, and predetermined amounts of these raw materials are Put the mixture obtained by mixing into a platinum crucible and add 1xzo to 1soo.
1ooo-irs after melting in an electric furnace at ℃ and stirring well to make the glass homogeneous.

It was poured into a mold at °C and slowly cooled to obtain the glass shown in Table 1.

The glass plate prepared as described above is optically polished to a thickness of jm at a jQtas angle to form a substrate.A metallic titanium film is applied to one side of this substrate as a mask for preventing ion transmission, and this titanium film is subjected to ordinary 7 otolithography. A circular ion permeation opening was created using the technique. This opening diameter is as shown in Example 1.
In this case, it is approximately 1100 tt. This masked glass substrate was then coated with thallium sulfate (TA'2SO4) 6
An ion exchange treatment was performed by immersing it in a mixed molten salt of 0 mol % and 90 mol % zinc sulfate (ZnSO4). The molten salt temperature at this time is about i below the transition point of each glass in Table 1.
o″C high temperature.

Further, as a comparative example, a substrate of BK-7 optical glass, which is conventionally used as a substrate glass for flat lenses, was prepared and subjected to ion exchange treatment in the same manner as described above. During the ion exchange treatment, a DC electric field of approximately 30 V was applied between both surfaces of the substrates for Examples 11≠ and 3 of the present application and Comparative Example, and for the others, natural diffusion was performed without applying an electric field.

After the ion exchange treatment was completed, the mask on the surface was removed, and the lens diameter and numerical aperture (NA) of the refractive index gradient lens formed within the substrate were measured. The results are shown in the lower part of Table 1.

The obtained planar lenses of Examples 7 to B were all highly transparent with no devitrification or corrosion observed on the glass surface. On the other hand, in the case of the comparative example made of BK-7 glass, a slight cloudiness was produced on the glass surface due to the erosion of the molten salt.

Furthermore, as is clear from comparing the Example and Comparative Example with the same lens diameter, the flat lens using the glass according to the present invention as a substrate is sufficient even for a very small lens with a diameter of 7 m or less. A large numerical aperture can be obtained.

〔effect〕

According to the present invention, erosion of the lens substrate glass during ion exchange treatment due to contact with molten salt is almost eliminated, and at the same time, a lens with optically stable performance is obtained.
A lens with a small diameter and a large numerical aperture (NA) can be obtained.

Furthermore, it has been confirmed that it has weather resistance equivalent to or better than conventional BK-7 optical glass even when used.

[Brief explanation of drawings]

Figure 1 is a side sectional view of a flat plate lens, Figure 2 is a plan view showing an example of the lens shape of the flat lens, Figure 3 is a plan view showing other examples of lens shapes, and Figure ψ is a method for manufacturing the flat lens. It is a sectional view showing an example.

Claims (1)

[Claims] In a flat lens in which a glass substrate is integrally formed with a lens portion whose optical axis is perpendicular to the substrate surface and whose refractive index has a distribution that changes from the optical axis toward the periphery and in the optical axis direction,
The main component of the substrate glass is SiO_2:45~
80 mol%, alkali metal oxide (R_2O): 8-3
5 mol%, ZnO: 2 to 20 mol%, B_2O_3:0
~8 mol%, Al_2O_3: 0-7 mol%, ZrO_
2: 0-2 mol%, CaO+BaO+MgO: 0-10
A flat lens characterized by containing mol%.