JP2002241144A - Low melting point and high refractive index tellurite glass and optical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a high refractive index tellurite glass not substantially containing a lead component, producible at a low temperature, having a low extinction coefficient to visible light and formable at a low temperature, and to provide an optical element using the tellurite glass. SOLUTION: The low melting point and high refractive index tellurite glass has a refractive index of >=1.8 and <1 mol% PbO content and is nearly colorless and transparent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to tellurite glass having a high refractive index of at least 1.8 and being almost colorless and transparent, and optical elements such as lenses, mirrors, cells, prisms and fibers for optical equipment. .

[0002]

2. Description of the Related Art Glass having a high refractive index is one of indispensable materials for a material of an optical element. Tellurite glass using a tellurium component is known as one of these glasses having a high refractive index used for an optical element. Examples of these tellurite glasses having a high refractive index include, for example, TeO ₂ -P described in British Patent No. 736073.
glasses such as bO system and TeO ₂ -PbO-B ₂ O ₃ system is known. However, these glasses contain PbO to provide a high refractive index, and have a drawback that lead, which is a toxic substance, is eluted from the glass. Also, tellurite glass containing no PbO, for example,
JP-B-51-17571, JP-A-62-3042
Nos. 4 and 5 in the publications TeO ₂ -WO ₃ -P ₂ O ₅ and TeO _{2, respectively.}
-BaO-K ₂ O-based glass are described, are known, these are glass to use an acousto-optic device was not intended as a high refractive index characteristic. Further, high refractive index glasses other than tellurite glass are also known. For example, JP-A-58-069739, JP-A-60-046948, JP-A-60-13184.
Although described in a number of documents such as Japanese Patent Publication No. 5, these high-refractive-index glasses are made of Nb ₂ O ₅ , La in order to increase the refractive index.
_Since the glass contains a large amount of ₂ O ₃ , Ta ₂ O _3, etc., the glass is colored yellow and has a shortcoming that the transmittance of short-wavelength light is poor. In addition, the production of these glasses requires high temperatures, the resulting glass has a high softening point, and when the glass is formed by a metal mold, the mold is extremely consumed.

[0003] The inventors of the present invention have conducted various tests and found that Nb ₂ O ₅ , La ₂ O ₃ , Ta ₂ O _3, etc., which do not contain lead at all and have a property of increasing the refractive index. Even without using a large amount of components, by using TeO ₂ as a main component,
It has been found that a nearly colorless and transparent glass having a high refractive index of 1.8 or more can be obtained. That is, the harmful component P
Although it does not contain bO and has the property of increasing the refractive index, it has a coloring property and a high melting point component, while suppressing the content of Nb ₂ O ₅ to be low. I succeeded in getting it. La ₂ O ₃ , Ta
_It is not necessary to contain ₂ O ₃ or the like.

[0004] Laser light is used in high-density optical recording, and an optical system is used to increase the recording density by using a lens or a mirror to focus the laser light as small as possible. In recent years, as these optical systems, a solid immersion lens (SIL: Solid Immersion Lens) utilizing a near field effect has been developed.
s) and solid immersion mirrors (SIM: Solid Immers)
An optical element called an “ion mirror” has been proposed. Here, the solid immersion lens refers to a lens in which the condensing optical system is a refraction system, and the solid immersion mirror refers to a lens in which a condensing optical system uses a reflection system. The optical disk that is the recording medium is rotating, and the optical element that reads and writes is lifted by the flow of air generated by the rotation, and the optical element and the optical disk are mechanically separated from each other to form an air layer. If the distance from the optical element is less than the wavelength of the light from the light source, the near-field effect works, the existence of an air layer is ignored, and a situation where the optical element is integrated is created. If a small focal point is set inside, reading and writing of the optical disk can be equivalently performed. The shorter the wavelength of the laser beam used, the higher the density of recording and reading can be performed, but the wavelength of the laser beam used is naturally limited. When the near-field effect is used, if the refractive index of the optical element is n, it is equivalent to using laser light having a wavelength of 1 / n of the wavelength of the laser light, and high-density recording can be read and written. As a material for the optical element, it is preferable to use a material having a high refractive index.

[0005]

SUMMARY OF THE INVENTION Accordingly, a first object of the present invention is to provide a high refractive index which contains substantially no lead component, can be manufactured at a low temperature, and has a low extinction coefficient for visible light. It is an object of the present invention to provide a tellurite glass. A second object of the present invention is to provide a high refractive index tellurite glass that can be stably manufactured. A third object of the present invention is to provide a high refractive index tellurite glass that can be formed at a low temperature. A fourth object of the present invention is to
An object of the present invention is to provide an optical element using a high-refractive-index tellurite glass that does not substantially contain a lead component, can be manufactured at a low temperature, and has a low absorption coefficient with respect to visible light.

[0006]

The objects of the present invention are as follows: (1) It has a refractive index of 1.8 or more, a PbO content of less than 1 mol%, and is almost colorless and transparent. Low melting point high refractive index tellurite glass. (Tellite glass of the present invention) (2) A tellurite glass containing TeO ₂ and Nb ₂ O ₅ as main components, and 80 to 95 mol% of TeO ₂ ,
The nb ₂ O ₅ comprises 1 to 20 mol%, and, tellurite glass, characterized in that does not contain a substantial lead component. (TeO ₂ —Nb ₂ O ₅ -based tellurite glass) (3) Tellurite glass containing TeO ₂ , B ₂ O ₃ and Al ₂ O ₃ as main components, wherein TeO ₂ is 60 to 95 m
ol%, 1 to 20 mol% of B ₂ O ₃ , and 1 to 2 of Al ₂ O ₃
A tellurite glass containing 0 mol% and substantially no lead component. (TeO ₂ -B ₂
O ₄ —Al ₂ O ₃ -based tellurite glass) (4) Tellurite glass containing TeO ₂ , GeO ₂ and B ₂ O ₃ as main components, wherein TeO ₂ is 60 to 95 mol.
l%, the GeO ₂ 1 to 20 mol%, the B ₂ O ₃ 1 to 20
A tellurite glass, which contains mol% and substantially does not contain a lead component. (TeO ₂ -Ge
O ₂ -B ₂ O ₃ system tellurite glass) (5) TeO _2, BaO and P ₂ O ₅ A tellurite glass as a main component, 60～95Mo the TeO ₂
l%, 1~20mol% of BaO, 1~20m the P ₂ O ₅
% tellurite glass and substantially no lead component. (TeO ₂ -BaO
-P ₂ O ₅ based tellurite glass) (6) TeO _2, the GeO _2, BaO and P ₂ O ₅ A tellurite glass as a main component, 60 to the TeO ₂
95 mol%, 1-20 mol% of GeO ₂ , 1-5 mol% of BaO, 1-5 mol% of P ₂ O ₅ , and
A tellurite glass substantially free of a lead component. _{(TeO 2 -GeO 2 -BaO-P} 2 O 5 system tellurite glass) (7) above (1) an optical element, characterized in that the tellurite glass is used according to any one of the - (6) .
(Optical element of the present invention) (8) The optical element according to the above (7), wherein the near-field effect is used. (Optical element using near-field effect of the present invention) (9) Solid immersion mirror (Solid Immersion)
(8) The optical element according to the above (8), wherein (Solid immersion mirror of the present invention) (10) Pseudo solid immersion mirror (Pseudo Solid)
(8) The optical element according to the above (8), wherein the optical element is an immersion mirror. (Pseudo solid immersion mirror of the present invention) (11) Solid immersion lens
(8) The optical element as described in (8) above. (Solid immersion lens of the present invention) (12) Pseudo Solid immersion lens (Pseudo Solid)
(8) The optical element as described in (8) above. (Pseudo solid immersion lens of the present invention).

Hereinafter, the present invention will be described in detail. In the present invention, tellurite glass refers to glass using TeO ₂ as a glass-forming oxide. TeO ₂ is used as a component for increasing the refractive index. However, if it exceeds 95 mol%, it becomes unstable in devitrification resistance, and it becomes difficult to obtain glass. If it is less than 60 mol%, the refractive index will be lower than 1.8. In the tellurite glass of the present invention, the PbO content is less than 1 mol%.
In the tellurite glass of the present invention, substantially colorless and transparent means having a transmittance of 80% or more in the entire visible light region. More preferably, it has a transmittance of 85% or more. During the production of the tellurite glass of the present invention, the melting point is preferably at most 1000 ° C, more preferably at most 800 ° C. In secondary processing such as press molding, the softening point is preferably as low as possible, and is preferably 600 ° C or lower, more preferably 400 ° C or lower.

Specific examples of the tellurite glass of the present invention include the above-mentioned TeO ₂ —Nb ₂ O ₅ based tellurite glass, Te
_{O 2 -B 2 O 3 -Al 2} O 3 system tellurite glass, TeO ₂ -
GeO ₂ -B ₂ O ₃ system tellurite glass, TeO ₂ -BaO
-P ₂ O ₅ based tellurite glass, TeO ₂ -GeO ₂ -Ba
O-P ₂ O ₅ system tellurite glass can be exemplified.
In these tellurite glasses, it is preferable that the lead component is not contained, but may be contained as long as the toxicity of the lead component is not a problem. This means that it contains substantially no lead component, and the content of the lead component is
PbO is preferably less than 1 mol%. Further, it is preferable not to add a lead component.

The above TeO_Two-Nb_TwoO_FiveSystem tellurite gala
, TeO_TwoIs a glass-forming oxide and is refracted
Although it is an essential component as a component for increasing the rate, 95
If it exceeds mol%, the devitrification resistance becomes unstable,
It is difficult to obtain. In this system, 80mol%
If it is less than 1, the refractive index will be lower than 1.8. Also, Nb
_TwoO_FiveIs an essential component. If it is less than 1 mol%, devitrification resistance
It becomes unstable, making it difficult to obtain glass. Also,
If it exceeds 40 mol%, vitrification becomes similarly difficult.
But Nb_TwoO_FiveIs a component that colors glass yellow.
To obtain almost colorless transparent glass without coloring yellow
Needs to be 20 mol% or less. Also, N
b_TwoO_FiveIs La_TwoO_ThreeAnd Ta_TwoO_ThreeUnlike in glass
TeO even if not present in quantity_TwoStable gas with two components
You can get a lath. TeO_Two-Nb_TwoO_FiveTerla
Light glass is TeO_TwoAnd Nb_TwoO_FiveConsists only of
But preferably TeO_TwoAnd Nb_TwoO_FiveThe main constituent
As long as the effects of the present invention are not impaired.
And may contain less than 20 mol% of other components.
No.

The above TeO_Two-B_TwoO_Three-Al_TwoO_ThreeTerla
In the glass, TeO_TwoIs a glass-forming oxide
Is an essential component for increasing the refractive index.
However, if it exceeds 95 mol%, the devitrification resistance becomes unstable,
It is difficult to obtain glass. In addition, 60 mol%
If it is full, the refractive index will be lower than 1.8. Also, B_TwoO_Three
And Al_TwoO_ThreeAre essential components, each of which is less than 1 mol%
If it is full, the devitrification resistance will be unstable, making it difficult to obtain glass.
It will be difficult. Further, when it exceeds 20 mol%, the refractive index becomes 1.
It falls below 8. TeO_Two-B_TwoO_Three-Al_TwoO_ThreeSystem
Lulite glass is TeO_Two, B_TwoO_ThreeAnd Al _TwoO_Threeonly
, But preferably TeO_Two, B_TwoO_Threeas well as
Al_TwoO_ThreeAs the main component, and the effect of the present invention
Other components less than 20 mol%, as long as
Minutes.

The above TeO_Two-GeO_Two-B_TwoO_ThreeKei
In glass, TeO_TwoIs a glass-forming oxide
Is an essential component for increasing the refractive index.
However, if it exceeds 95 mol%, the devitrification resistance becomes unstable,
It is difficult to obtain glass. In addition, 60 mol%
If it is full, the refractive index will be lower than 1.8. In addition, GeO
_TwoAnd B_TwoO_ThreeAre essential components, each of which is less than 1 mol%
If it is full, the devitrification resistance will be unstable, making it difficult to obtain glass.
It will be difficult. In addition, GeO_TwoExceeds 20 mol%, G
eO_TwoBecomes difficult to melt, and the glass
It becomes difficult to melt below. Also, B_TwoO_ThreeIs 20m
If it exceeds ol%, the refractive index will be lower than 1.8. T
eO_Two-GeO_Two-B_TwoO_ThreeSystem glass is TeO_Two, GeO_Two
And B_TwoO_ThreeAlthough it is preferable to be composed only of TeO,
_Two, GeO_TwoAnd B_TwoO_ThreeShould be the main component,
20 mol% as long as the effects of the present invention are not impaired.
Less than other components.

In the above-mentioned TeO ₂ —BaO—P ₂ O ₅ system tellurite glass, TeO ₂ is a glass-forming oxide and is an essential component for increasing the refractive index. The devitrification becomes unstable,
It is difficult to obtain glass. If it is less than 60 mol%, the refractive index will be lower than 1.8. In addition, BaO
And P ₂ O ₅ are essential components, and if each is less than 1 mol%, the devitrification resistance becomes unstable, and it becomes difficult to obtain glass. When BaO exceeds 20 mol%, BaO
O becomes difficult to melt, and it becomes difficult to melt at 1000 ° C. or less during glass production. In addition, 20 mol of P ₂ O ₅
%, The refractive index is lower than 1.8. TeO
₂ -BaO-P ₂ O ₅ system tellurite glass, TeO _2, B
Although it is preferable to be composed only of aO and P ₂ O ₅ ,
It is sufficient that eO ₂ , BaO and P ₂ O ₅ are the main constituent components, and as long as the effects of the present invention are not impaired, 20 mo
It may contain less than 1% of other components.

The above TeO_Two-GeO_Two-BaO-P_TwoO_Fivesystem
In tellurite glass, TeO _TwoIs glass-forming oxidation
And an essential component to increase the refractive index
However, if it exceeds 95 mol%, the devitrification resistance becomes unstable.
And it becomes difficult to obtain glass. Also, 60mo
If it is less than 1%, the refractive index will be lower than 1.8. Also,
GeO_TwoAnd BaO and P_TwoO_FiveIs an essential ingredient,
If it is less than 1 mol%, the devitrification resistance becomes unstable and the glass
It is difficult to obtain. In addition, GeO_TwoIs 20 mol%
Exceeds GeO_TwoIs difficult to melt,
It is difficult to melt at 1000 ° C. or lower. Also, B
aO and P_TwoO_FiveExceeds 5 mol% for the same reason.
It becomes difficult to obtain a lath. TeO_Two-GeO_Two-Ba
OP_TwoO_FiveSeries tellurite glass is TeO_Two, GeO_Two,
BaO and P_TwoO_FiveAlthough it is preferable to consist of only
TeO_Two, GeO_Two, BaO and P_TwoO_FiveIs the main component
As long as the effects of the present invention are not impaired.
And may contain less than 20 mol% of other components.

The tellurite glass of the present invention has a high refractive index and can form optical elements such as lenses for optical equipment, mirrors, cells, prisms, and fibers.
Further, the tellurite glass of the present invention has a low softening point and can be easily obtained by molding or other molding.

Next, an optical element using a near-field effect of the present invention will be described. The tellurite glass of the present invention has high transmittance of short-wavelength light and has a high refractive index, and an optical element using the near-field effect formed using the same has excellent performance. Further, the tellurite glass of the present invention has a low softening point and can be easily obtained by molding or other molding. The optical element using the near-field effect of the present invention can be used in an optical system for performing high-density reading and writing using laser light. The optical element using near-field effect using the tellurite glass of the present invention, which has a high refractive index and excellent transparency, can read and write high-density recording. Laser light is used for reading and writing optical recording, and in order to read and write at high density, an optical system for turning the laser light to a focusing point as small as possible by a lens or a mirror is used. By using the optical element using the near-field effect of the present invention for these optical systems, reading and writing can be performed at high density. As a typical example of the optical element using the near-field effect,
A solid immersion mirror (SIM: Solid Immersion Mirr) in which a reflection system is used as an optical system for condensing light.
or), a solid immersion lens (S
IL: Solid Immersion Lens, which is a solid immersion mirror of the present invention.
ion Mirror (SIM), solid immersion lens (So
lid Immersion Lens (SIL) refers to these. Similarly, a pseudo solid immersion mirror (Pseudo SIM: Pse
udo Solid Immersion Mirro
r) and pseudo solid immersion lenses (Pseudo SIL: Ps
eudo Solid Immersion Len
s), and the pseudo solid immersion mirror (Pseudo) of the present invention.
Solid Immersion Mirror)
(Pseudo SIM) or pseudo solid immersion lens (Pseudo SIM)
udo Solid Immersion Lens)
(Pseudo SIL) means these.

A solid immersion mirror (SIM) and a solid immersion lens (SIL) of the present invention will be described below with reference to the drawings. Figure 1
FIG. 1 illustrates a solid immersion mirror (SIM) of the present invention. In FIG.
2 is a first optical surface of tellurite glass 1, 3 is a second optical surface of tellurite glass 1, 4 is a plane mirror, 5 is a third optical surface of tellurite glass 1, 6 is a focal point, and 7 is an optical recording disk. Show. The first optical surface 2 forms a concave surface, and the third optical surface 5 is a concave mirror. The plane mirror 4 is formed on the outer periphery of the second optical surface 3 excluding the portion connecting the focal point 6 at the center. The SIM is mounted on a flying head, and the distance between the second optical surface 3 and the optical recording disk 7 is determined by the balance between the dynamic pressure generated by the rotation of the optical recording disk 7 and the force of the presser spring. It is stably held at a distance of １ ／ or less of the wavelength. The laser light, which is a light source, enters the first optical surface 2, diverges because it is a concave surface, follows a path indicated by an arrow, is reflected by a plane mirror 4 and turned back, and then condensed by a third optical surface 5 that is a concave mirror. Then, the focus is focused on the focus 6. A near field is generated at the focal point 6 by a near-field effect, and optical energy is directly transmitted to the optical recording disk 7 without being affected by an air layer between the second optical surface 3 and the optical recording disk 7.

FIG. 2 illustrates a solid immersion lens (SIL) system using the solid immersion lens (SIL) of the present invention. In FIG.
Denotes a hemispherical solid immersion lens, 13 denotes a hemispherical surface of the hemispherical solid immersion lens 12, 14 denotes a lower plane of the hemispherical solid immersion lens 12, 15 denotes a focal point, and 16 denotes an optical recording disk. Solid immersion lens (SI
The L) system includes a double-sided aspherical condenser lens 11 and a hemispherical solid immersion lens 12. The solid immersion lens (SIL) of the present invention
The system is mounted on a flying head, and the distance between the lower plane 14 of the hemispherical solid immersion lens 12 and the optical recording disk 16 is determined by the light source by the balance between the dynamic pressure generated by the rotation of the optical recording disk 16 and the force of the holding spring. It is stably held at a distance of 1/4 or less of the wavelength of a certain laser beam. Laser light as a light source is a double-sided aspherical condensing lens 11
, Is condensed, passes through the path indicated by the arrow, and is incident at right angles from the hemispherical surface 13 of the hemispherical solid immersion lens 12 to the contact surface of the hemispherical surface 13 and is condensed at the focal point 15. At the focal point 15, a near field is generated due to the near-field effect, and the lower surface 14 of the hemispheric solid immersion lens 12 and the optical recording disk 16
The light energy is transmitted directly without being affected by the air layer between the light source and the light source.

In FIG. 1, the size (ψ) of the converging point at the focal point 6, the refractive index (n) of the optical material constituting the SIM, the opening angle (θ) of the light beam when converging, and the wavelength used ( The relationship of λ) is given by ψ∝λ / NA =
Since λ / nsin θ, the size of the focal point (ψ) is
Even when laser light of the same wavelength is used and the aperture angle is the same, it is 1 when focused in air (n = 1).
/ N. At the focal point 6, a near-field is generated by the near-field effect, and the optical recording disk 7, which is at a very short distance of 1/4 or less of the wavelength, is brought into proximity by the near-field effect without passing through the air existing therebetween. Since the energy of the field reaches, the air layer existing between the focal point 6 and the optical recording disk 7 has no influence on the arrival of the energy. Therefore, if the near-field effect is used, reading / writing is performed on the optical recording disk 7 at a converging point having a size of 1 / n, and as a result, the recording area can be reduced to 1 / n ^2. The recording capacity of the recording disk 7 can be improved by n ² times. As described above, when the SIM is used, even if the ray paths have the same geometric open angle (θ),
The larger the refractive index (n) of the optical material used for the SIM, the higher the recording capacity. The shorter the wavelength (λ) of the light source light, the higher the recording capacity can be improved. However, the wavelength in the SIM is 1 / n of the wavelength of the light source used (n: the refractive index of the optical material used in the SIM). Therefore, a material having a high refractive index is advantageous from this point as well. In addition, in order to use a light source having a short wavelength, it is advantageous that the transmittance at a short wavelength is higher in terms of securing the amount of light. The tellurite glass of the present invention has a high refractive index and a low yellowish color, so that the transmittance of short wavelengths such as blue is high. Although the dispersion is large, there is almost no focal point shift or aberration change with respect to the wavelength change due to the normal incidence or reflection optical system, so that the large dispersion does not pose a problem when used for SIL or SIM. Dispersion is one characteristic of an optical material, and is one characteristic when designing an optical element.

The hemispheric solid immersion lens 12 in FIG. 2 focuses on the hemisphere spherical center of the hemispheric solid immersion lens 12 (SIL), but focuses below the SIL spherical center as shown in FIG. A connection method (super SIL method) can also be used. 3, reference numeral 21 denotes a solid immersion lens, 22 denotes an upper spherical surface of the solid immersion lens 21, 23 denotes a lower plane of the solid immersion lens 21, 24 denotes a focal point, and 25 denotes an optical recording disk. In FIG. 3, light condensed by a condensing lens (not shown) is incident on the upper spherical surface 22 of the solid immersion lens 21 along a path indicated by an arrow, and condensed on a focal point 24 of a lower flat surface 23. At the focal point 24, a near field is generated by a near field effect,
Optical energy is directly transmitted to the optical recording disk 25 without being affected by the air layer between the lower flat surface 23 of the solid immersion lens 21 and the optical recording disk 25. As shown in FIG. 3, when the super-SIL system in which focused below the spherical center of the SIL, the minute light is refracted, compared with the case of FIG. 2 without refraction, opening angle of the light beam to the theta ₀ theta Figure 2
Can spot diameter than when using a hemispherical solid immersion lens 12 further to 1 / n as shown in, as a result, since the equivalently used wavelength it has become a lambda / n ^2, increasing the recording density Can be. The light beam incident on the solid immersion lens 21 generates a spherical aberration when refracted. However, by using a condensing lens having a spherical aberration in the opposite direction so as to cancel the amount of the generated aberration, the focus can be reduced. 24 can be reduced. This effect is important for SIM and SIL
Irrespective of the type or shape of the optical element, the same effect can be obtained in an optical element using the near-field effect. The opening angle of the luminous flux is
Since the conventional high refractive index glass and the tellurite glass of the present invention are almost the same, there is no difference in the size or inclination angle of the optical surface, and the aspherical optical surface of the mold for molding SIM or SIL. The difficulty of making the shape is not much different from the case of using conventional high refractive index glass, and from the point of shape,
It can be said that the near field optical element using either material has almost the same ease of fabrication.

Next, a pseudo solid immersion mirror (Pseudo SIM) and a pseudo solid immersion lens (Pseudo SIL) of the present invention will be described with reference to the drawings. Pseudo solid immersion mirror (Pseudo SIM) and pseudo solid immersion lens (Pseudo SIM)
Pseudo SIL) is an optical element in which coupling by a near-field effect is performed at a place other than the focal point. FIG. 4 shows a pseudo solid immersion mirror (Pseudo SI) of the present invention.
In the figure, 31 is the tellurite glass of the present invention, 32 is the first optical surface of the tellurite glass 31, 33 is the second optical surface of the tellurite glass 31, 34 is a plane mirror, 35 is the third of tellurite glass 31
An optical surface, 36 is a focal point, 37 is an optical recording disk, 38 is a transparent cover layer of the optical recording disk 37, 39 is a substrate of the optical recording disk 37, and 40 is a recording surface of the optical recording disk 37. The first optical surface 32 forms a concave surface, and the third optical surface 35 is a concave mirror. Further, the plane mirror 34 is formed on the outer periphery of a portion for near-field coupling at the center of the second optical surface 33. Pseudo SIM has a first optical surface 32,
It is composed of the tellurite glass 31 of the present invention having a second optical surface 33 and a third optical surface 35. Pseudo
The SIM is attached to the flying head, and the distance between the second optical surface 33 and the surface of the transparent cover layer 38 of the optical recording disk 37 is determined by the balance between the dynamic pressure generated by the rotation of the optical recording disk 37 and the force of the holding spring. Is stably held at a distance of 1/4 or less of the wavelength of the laser light. The laser light, which is a light source, enters the first optical surface 32, diverges because it is a concave surface, follows a path indicated by an arrow, is reflected by the plane mirror 34 of the second optical surface 33, and is turned back. The light is collected by the optical surface 35. The condensed light enters the transparent cover layer 38 and is recorded on the recording surface 40.
Focus on focal point 36 of. There is an air layer between the second optical surface 33 and the transparent cover layer 38. A near field is generated between the second optical surface 33 and the near-field effect, and light energy is transmitted without being affected by the air layer.

FIG. 5 shows a pseudo solid immersion lens (Ps) of the present invention.
pseudo solid immersion lens (Pse
FIG. 5 illustrates a double-sided aspherical condensing lens, 42 a pseudo solid immersion lens, 43 a spherical surface of a pseudo solid immersion lens 42, and 44 a pseudo solid immersion. A lower plane of the lens 42, 45 is a focal point, 46 is an optical recording disk, 47 is a transparent cover layer of the optical recording disk 46, 48 is a substrate of the optical recording disk 46, and 49 is a recording surface of the optical recording disk 46. Pseudo solid immersion lens (Ps
The Sudo (Eudo SIL) system includes a double-sided aspherical condenser lens 41 and a pseudo solid immersion lens 42. Ps of the present invention
The Eudo SIL system is mounted on a flying head, and the distance between the lower flat surface 44 of the pseudo solid immersion lens 42 and the optical recording disk 46 is determined by the balance between the dynamic pressure generated by the rotation of the optical recording disk 46 and the force of the holding spring. , And is stably held at a distance of １ ／ or less of the wavelength of the laser light as the light source. Laser light, which is a light source, enters the double-sided aspherical condenser lens 41, is condensed, and follows the path indicated by the arrow at right angles from the spherical surface 43 of the pseudo solid immersion lens 42 to the contact surface of the spherical surface 43. Light emitted from the lower plane 44 enters the transparent cover layer 47 and is focused on the focal point 45 of the recording surface 49. Lower plane 44 and transparent cover layer 4
7, there is an air layer, between which a near field is generated by the near-field effect, and light energy is transmitted without being affected by the air layer. The pseudo solid immersion lens 42 in FIG.
In FIG. 3, the laser beam is incident on the spherical surface 43 at right angles to the tangent surface, and no refraction occurs on the spherical surface 43.
In the same manner as in the super SIL method shown in FIG. Since the light is refracted, the opening angle (θ) of the light flux is increased as compared with the case of FIG. 5 in which the light is not refracted, so that the same effect as the super SIL method shown in FIG. 3 can be obtained.

FIG. 6 illustrates a pseudo solid immersion lens (super pseudo solid immersion lens) in the above-mentioned system (super pseudo solid immersion lens system).
51 is a pseudo solid immersion lens, 52 is a pseudo solid immersion lens 51
The upper spherical surface of 53, the lower plane of the pseudo solid immersion lens 51,
54 is a focal point, 55 is an optical recording disk, 56 is a transparent cover layer of the optical recording disk 55, and 57 is an optical recording disk 55
Reference numeral 58 denotes a recording surface of the optical recording disk 55. In FIG. 6, light condensed by a condensing lens (not shown) is refracted from the upper spherical surface 52 of the pseudo solid immersion lens 51 and follows the path indicated by the arrow. Lower plane 5
3 is incident on the transparent cover layer 56, and the recording surface 5
Focus on the focal point 54 of 8. Although there is an air layer between the lower plane 53 and the transparent cover layer 56, a near field is generated between them by a near-field effect, and light energy is transmitted without being affected by the air layer. The solid immersion mirror (SI
M) and the solid immersion lens (SIL), the simulated solid immersion mirror (Pseudo SIM) and the simulated solid immersion lens (Pseudo SIL) of the present invention can be easily manufactured using a conventional high refractive index glass. There is no big difference from the case where it was, and it can be said that the ease of making is almost the same.

[0023]

The present invention will be described below in more detail with reference to examples, but the present invention is not limited to these examples. Example 1 The components were weighed and mixed so as to have the composition shown in Table 1, placed in a gold crucible with a lid, and melted at a melting temperature shown in Table 1 for 1 hour. Pour the glass melt into a stainless steel mold.
No. 50 × 5 mm thick tellurite glass sample No.
1-10 were obtained. The obtained glass was transferred into a lehr and kept at a glass transition temperature (Tg) shown in Table 1 for 30 minutes.
The furnace was gradually cooled. The mirror was polished to a thickness of 3 mm, and the spectral transmittance was measured. Further, the film was polished into a prism shape, and the refractive index (nd) was measured by the minimum deflection angle method. Further, the melting temperature (MT) and glass transition temperature (Tg) of the obtained glass were measured. Table 1 shows the obtained results.

[0024]

[Table 1] As is clear from Table 1, the tellurite glasses of the present invention all have a melting temperature (MT) of 1000 ° C. or less,
It had a low glass transition temperature (Tg). In addition, each glass sample was almost colorless and transparent, and had a refractive index (nd).
Was 1.8 or more. The refractive index and Abbe number of these glasses can be controlled by changing the composition.

Example 2 Using the tellurite glass (sample No. 2) of the present invention and E-FDS1 which is a conventional general high refractive index optical glass, a SIM shown in FIG. 1 having the same opening angle was manufactured. . Glass transition temperature of the used glass, light wavelength 650 nm and 450
Table 2 shows the internal transmittance, the refractive index, and the dispersion in nm. In addition, the diameter of the focused spot was determined. Table 2 shows the obtained results. Table 2 shows the recording capacity ratio of the SIM using the tellurite glass of the present invention and E-FDS1 which is a general high refractive index optical glass.

[0026]

[Table 2] SIM using E-FDS1 is 650 nm, which is currently mainstream.
Can be used when the light source wavelength is used, but the transmittance is low for the blue light source wavelength (405 nm) used for optical recording applications such as next-generation DVDs, and the CNR of the optical recording disk signal is inferior. Absent. On the contrary,
INDUSTRIAL APPLICABILITY The tellurite glass of the present invention is colorless and transparent in the visible light region, has no color, can secure a transmittance of 81% even with a blue light source, and can be used for optical recording applications such as next-generation DVDs. Since the tellurite glass of the present invention can use a light source with a shorter wavelength in addition to having a high refractive index, the focused spot diameter is reduced to about 83% of that of the conventional high refractive index optical glass. Can be smaller. Therefore, since the recording capacity is inversely proportional to the square of the focused spot diameter, it can be improved by about 50% as compared with the case where the conventional high refractive index optical glass is used. In the above description, the NA (nsinθ) of the SIM using the tellurite glass of the present invention is 1.5.

Embodiment 3 In the solid immersion lens (SIL) system shown in FIG. 2, the double-sided aspherical condenser lens 11 has a light source wavelength of 650 nm and an NA of 0.6.
It was manufactured by molding an optical glass equivalent to SK12 by a glass molding method.
At this time, the focusing spot diameter of the single-sided aspherical focusing lens 11 was 605 nm. This is combined with a hemispheric solid immersion lens 12 formed by molding and polishing the tellurite glass (sample No. 3) of the present invention, and the condensing spot diameter is set to SNOP (scanning near-field optical stylus). As a result, the diameter of the focused spot was 335 nm.

Example 4 Using the tellurite glass of the present invention (sample No. 2) and E-FDS1 which is a conventional high refractive index optical glass, a super SIL having the same opening angle as shown in FIG. 3 was produced. The refractive index of the used general high refractive index optical glass at a light wavelength of 650 nm and the 450 of the tellurite glass of the present invention used.
Table 3 shows the refractive index in nm. In addition, the focused spot diameter of the obtained super SIL was determined. Table 3 shows the obtained results. Table 3 shows the recording capacity ratio of the tellurite glass of the present invention and the super SIL using E-FDS1 which is a general high refractive index optical glass.
The conventional high refractive index glass used a light source having a wavelength of 650 nm because of low blue light transmittance, and the tellurite glass of the present invention used a light source having a wavelength of 405 nm because of high blue light transmittance.

[0029]

[Table 3] Since the recording density ratio is inversely proportional to the square of the spot diameter ratio, n
^As can be seen from Table 3, the tellurite glass of the present invention has a recording density five times or more that of the conventional high refractive index glass.

Example 5 The focal plane of the super SIL of Example 4 was polished and removed by 0.1 mm to produce a pseudo solid immersion lens shown in FIG. The pseudo solid immersion lens has a thickness of 0.1 mm formed of tellurite glass (sample No. 2) formed on the recording surface 58 of the optical recording disk 55 on the lower flat surface 53 of the pseudo solid immersion lens.
When the transparent cover layer 56 is coupled to the near-field, the light is focused on the recording surface 58. A disk surface made of tellurite glass (sample No. 2) having a thickness of 0.1 mm is coupled to the lower flat surface 53 of the pseudo solid immersion lens by near-field, and the condensed spot diameter on the back surface is set to the above-mentioned SNOP.
(Scanning near-field optical stylus)
It was 0.45 μm, which was almost a theoretical value. In the quasi-solid immersion lens, since near-field coupling is performed not at the focal point but at a location where the light beam spreads to a diameter of about 0.15 mm, even if there is dust or scratches on the optical recording disk, it is not affected. Hateful. Also, since a cover layer having a thickness of 0.1 mm can be used which is 1000 times or more thicker than a surface recording method in which the cover layer must be extremely thin,
Since the material constituting the recording surface does not directly come into contact with oxygen or water vapor, it is not oxidized and has excellent environmental resistance and reliability. Therefore, in the optical recording system using the pseudo solid immersion lens, there is no need to seal the optical recording disk to shield it from the air, and a removable optical recording system can be easily provided. These effects can be obtained from the embodiment 5 described above.
It is not limited to the pseudo solid immersion lens of FIG.
Such a pseudo near-field optical element in which coupling by the near-field effect is performed at a position other than the focus such as SIM or SIL described above is similarly obtained, and has a high refractive index and a short wavelength transmittance. Since the numerical aperture NA is increased, the recording density can be improved.

The tellurite glass of the present invention has a Tg of 400 ° C. or less, which is 150 times smaller than that of the conventional high refractive index optical glass.
Because it is lower than ℃, molding by glass molding technology is also more suitable than conventional high refractive index optical glass, and the heat resistance life of the molding die was 10,000 shots with the conventional high refractive index optical glass, Since the temperature can be increased to 34,000 shots or more, and the molding temperature can be lowered, the heating and cooling time is shortened, and the molding cycle is reduced to 5 times when the conventional high refractive index optical glass is used. Since it can be significantly shortened from minutes to less than two minutes, the production efficiency of near-field optical elements such as SIM and SIL, which are high-precision and high-NA optical elements with high molding difficulty, can be significantly increased.

[0032]

The telluride glass of the present invention has a high refractive index of 1.8 or more, is almost colorless and transparent, and is extremely useful as an optical glass for optical equipment such as lenses, mirrors, cells, prisms, and fibers. It is. Further, it can be dissolved at a low temperature of 1000 ° C. or less, and can be easily manufactured and molded. Further, the solid immersion mirror, the pseudo solid immersion mirror, the solid immersion lens, and the pseudo solid immersion lens of the present invention can use a light source of a short wavelength and can read and write at high density.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a solid immersion mirror (SIM) of the present invention.

FIG. 2 is an explanatory diagram of a solid immersion lens (SIL) system using the solid immersion lens (SIL) of the present invention.

FIG. 3 is a solid immersion lens (S
It is an explanatory view of an IL) system.

FIG. 4 shows a pseudo solid immersion mirror (Pseudo S) of the present invention.
FIG.

FIG. 5 is a pseudo solid immersion lens (Pseudo S) of the present invention.
Pseudo SI (Pseudo SI)
It is explanatory drawing of L) system.

FIG. 6 shows a super quasi-solid immersion lens (Pseu) of the present invention.
do SIL) pseudo immersion lens (Pseudo)
It is explanatory drawing of a (SIL) system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tellurite glass of the present invention 6 Focus 7 Optical recording disk 11 Double-sided aspherical condensing lens 12 Hemispheric solid immersion lens 15 Focus 16 Optical recording disk 21 Solid immersion lens 24 Focus 25 Optical recording disk 31 Tellurite glass of the present invention 32 1 optical surface 33 second optical surface 34 plane mirror 35 third optical surface 36 focal point 37 optical recording disk 38 transparent cover layer 40 recording surface 41 double-sided aspheric condenser lens 42 pseudo solid immersion lens 43 spherical surface 44 lower plane 45 focal point 46 Optical recording disk 47 Transparent cover layer 49 Recording surface 51 Pseudo solid immersion lens 52 Upper spherical surface 53 Lower plane 54 Focus 55 Optical recording disk 56 Transparent cover layer 58 Recording surface

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Nobuhito Takeshima 380 Toyo, Kashiwa-shi, Chiba Prefecture Okamoto Glass Co., Ltd. (72) Inventor Yoshi Yokota 380 Toyo, Kashiwa-shi, Chiba Prefecture 380 Okamoto Glass Co., Ltd. (72) Inventor Arai Atsushi 380 Toyoji Kashiwa-shi, Chiba Prefecture Okamoto Glass Co., Ltd. FB01 FC01 FD01 FD02 FD03 FD04 FE01 FF01 FG01 FG02 FG03 FG04 FH01 FJ01 FK01 FL01 GA01 GB01 GC01 GD06 GD07 GD08 GE01 HH01 HH03 HH05 HH07 HH09 HH11 HH13 HH15 HH07 KK01 JJ01 KK01 JJ01 KK01 JJ01

Claims (12)

[Claims] 2. The method according to claim 1, wherein the refractive index is 1.8 or more and Pb
Low melting point high refractive index tellurite glass having an O content of less than 1 mol% and being substantially colorless and transparent. 2. A tellurite glass containing TeO ₂ and Nb ₂ O ₅ as main components, wherein TeO ₂ is 80 to 95 m.
ol%, the Nb ₂ O ₅ comprises 1 to 20 mol%, and, tellurite glass, characterized in that does not contain a substantial lead component. _3. A tellurite glass containing TeO ₂ , B ₂ O ₃ and Al ₂ O ₃ as main components, wherein TeO ₂ is 60%.
~95mol%, B ₂ O ₃ to 1~20mol%, Al ₂ O ₃
Is a tellurite glass, containing 1 to 20 mol% and substantially no lead component. 4. A tellurite glass containing TeO ₂ , GeO ₂ and B ₂ O ₃ as main components, wherein TeO ₂ is 60 to
95 mol%, the GeO ₂ 1 to 20 mol%, the B ₂ O ₃ comprises 1 to 20 mol%, and, tellurite glass, characterized in that does not contain a substantial lead component. _5. A tellurite glass containing TeO ₂ , BaO and P ₂ O ₅ as main components, wherein TeO ₂ is 60 to 50%.
95 mol%, 1 to 20 mol% of BaO, 1 of P ₂ O ₅
A tellurite glass containing -20 mol% and substantially no lead component. 6. A tellurite glass containing TeO ₂ , GeO ₂ , BaO and P ₂ O ₅ as main constituents, wherein TeO ₂
From 60 to 95 mol%, GeO ₂ from 1 to 20 mol%,
1 to 5 mol% of BaO, and P ₂ O ₅ comprises 1 to 5 mol%, and, tellurite glass, characterized in that does not contain a substantial lead component. 7. An optical element comprising the tellurite glass according to claim 1. 8. The optical element according to claim 7, wherein a near-field effect is used. 9. The optical element according to claim 8, wherein the optical element is a solid immersion mirror. 10. The optical element according to claim 8, wherein the optical element is a pseudo solid immersion mirror. 11. The optical element according to claim 8, wherein the optical element is a solid immersion lens. 12. The optical element according to claim 8, wherein the optical element is a pseudo solid immersion lens.