TW201922649A - Optical glass, preform, and optical element characterized by having a smaller partial dispersion ratio ([theta]g, F) while having a refractive index (nd) and an Abbe number ([nu]d) within desired ranges - Google Patents

Abstract

The object of the present invention is to provide an optical glass, a preform, and an optical element, wherein the optical glass has a refractive index (nd) and an Abbe number ([nu]d) within desired ranges, and a smaller partial dispersion ratio ([theta]g, F) . The optical glass comprises, in mass%, 20.0% to 45.0% of a SiO2 component, 25.0% to 60.0% of an Nb2O5 component, and 0% to 5.0% of a TiO2 component, and a mass ratio (Li2O/Na2O+K2O ) between 0.40 and 1.00, and the partial dispersion ratio ([theta]g, F) to the Abbe number ([nu]d) satisfies (-0.00162*[nu]d +0.620)≤([theta]g, F)≤(-0.00162*[nu]d +0.657), wherein the temperature coefficient (40 to 60 DEG C) of the relative refractive index (589.29 nm) is within the range of +6.0×10 <SP>-6</SP> (DEG C-1) to -5.0×10<SP>-6</SP> (DEG C<SP> -1</SP>).

Description

 Optical glass, preforms, and optical components  

The present invention relates to an optical glass, a preform, and an optical component.

An optical system such as a digital camera or a camera contains more or less bleed called aberration. This aberration is classified into monochromatic aberration and chromatic aberration, particularly chromatic aberration, which largely depends on the material properties of the lens used in the optical system.

In general, a chromatic aberration is corrected by a combination of a low-dispersion convex lens and a high-dispersion concave lens. However, such a combination can only correct aberrations of the red region and the green region, and the aberration of the blue region still exists. The aberration of such a blue region that cannot be removed is called a secondary spectrum. When correcting the secondary spectrum, an optical design in which the g-line (435.835 nm) of the blue region is considered is required. At this time, a partial dispersion ratio (θ _g , F) is used as an optical characteristic index focused on optical design. In an optical system in which the low-dispersion lens and the high-dispersion lens are combined, an optical material having a large partial dispersion ratio (θ _g , F) is used by a lens having a low dispersion side, and a partial dispersion is used for a lens having a high dispersion side. For optical materials with smaller (θ _g , F), the secondary spectrum will be well corrected.

The partial dispersion ratio (θ _g , F) can be expressed by the following formula (1).

θ _g , F=(n _g -n _F )/(n _F -n _C )‧‧‧‧‧‧(1)

In the optical glass, there is a nearly linear relationship between the partial dispersion ratio (θ _g , F) indicating the partial dispersion of the short-wavelength region and the Abbe number (ν _d ). The straight line representing the relationship is represented by the partial dispersion ratio (θ _g , F) as the vertical axis and the Abbe number (ν _d ) as the horizontal axis, and the partial dispersion ratio and the Abbe number of NSL7 and PBM2 are drawn. The line connecting the two points is indicated by a straight line (refer to Fig. 1). Standard glass, which is a regular line standard, varies depending on the manufacturer of the optical glass. However, each manufacturer is almost always defined by the same inclination and intercept. (NSL7 and PBM2 are optical glasses manufactured by Ogawa Co., Ltd., the Abbe number (ν _d ) of PBM2 is 36.3, the partial dispersion ratio (θ _g , F) is 0.5828, and the Abbe number (ν _d ) of NSL7 is 60.5. The dispersion ratio (θ _g , F) is 0.5436.)

In recent years, as an optical material having a small partial dispersion ratio (θ _g , F), a glass having an Abbe number (ν _d ) of 25 or more and 40 or less is more frequently used due to the demand for optical design.

In addition, in recent years, optical components incorporated in automotive optical instruments such as car cameras, or optical components incorporated in projectors, photocopiers, laser printers, and playback devices, which generate a large amount of heat, have been used. The situation continues to increase in high temperature environments. In such a high-temperature environment, the temperature of the optical element constituting the optical system is likely to vary greatly, and the temperature often reaches 100 ° C or higher. At this time, the negative influence on the imaging characteristics of the optical system due to the temperature fluctuation is so large that it cannot be ignored. Therefore, it is desirable to constitute an optical system which is difficult to affect the imaging characteristics and the like even if temperature fluctuation occurs.

When an optical system that is difficult to affect imaging characteristics or the like due to temperature fluctuation is formed, an optical element composed of glass having a negative refractive index when the temperature rises and a temperature coefficient of a relative refractive index is increased, and when the temperature rises When the refractive index is high and the optical element composed of the glass having a positive temperature coefficient of the refractive index is used together, it is preferable to be able to correct the influence on the imaging characteristics and the like due to the temperature change.

On the other hand, in an optical material having a small partial dispersion ratio (θ _g , F), a component (for example, a Nb ₂ O ₅ component, a La ₂ O ₃ component, or the like) which is contained in order to obtain various excellent optical properties. There is a tendency that the temperature coefficient of the relative refractive index becomes large. As such an optical glass, for example, a glass composition shown in Patent Document 1 is known.

In particular, in-vehicle lenses or exchange lenses used in recent years have increased the number of scenes used in various environments. Therefore, it is required that a partial dispersion ratio (θ _g , F) is small and a temperature coefficient of relative refractive index is small. Optical glass.

[Previous Technical Literature]

[Patent Literature]

Patent Document 1: Japanese Laid-Open Patent Publication No. SHO-58-125637.

However, in the glass disclosed in Patent Document 1, since the content of the Nb ₂ O ₅ component having a small partial dispersion ratio is small and the amount of TiO ₂ is large, it is not sufficient as a lens for correcting the above secondary spectrum. Further, it cannot be said that the content of the basic metal is small and the temperature coefficient of the relative refractive index is small.

The present invention has been made in view of the above problems, and an object thereof is to obtain an optical glass having a refractive index (n _d ) and an Abbe number (ν _d ) within a desired range and a partial dispersion ratio (θ). _g , F) are small and have a relatively small temperature coefficient of relative refractive index.

In order to solve the above problems, the inventors of the present invention have focused on the results of the cumulative test and found that in the glass containing the SiO ₂ component and the Nb ₂ O ₅ component, by limiting the amount of the TiO ₂ component to 5.0% or less, it is possible to obtain The present invention has been completed in an optical glass having a high refractive index and an Abbe number (high dispersion), a low partial dispersion ratio, and a small temperature coefficient of relative refractive index within a desired range.

(1): an optical glass containing, by mass%, 20.0% to 45.0% of SiO ₂ component, 25.0% to 60.0% of Nb ₂ O ₅ component, 0% to 5.0% of TiO ₂ component, and mass ratio (Li ₂ O/ Na ₂ O+K ₂ O) is between 0.40 and 1.00, and the partial dispersion ratio (θ _g , F) and Abbe number (ν _d ) are satisfied (-0.00162×ν _d +0.620) (θ _g , F) (-0.00162 × ν _d +0.657), the relative refractive index (589.29nm) temperature coefficient (40 ° C to 60 ° C) at +6.0 × 10 ^-6 (°C ^-1 ) to -5.0 × 10 ^-6 (°C ^-1 ) within the scope.

(2) The optical glass according to (1), wherein the mass ratio (Rn ₂ O/Nb ₂ O ₅ ) is 0.50 or less, and Rn in the formula is one selected from the group consisting of Li, Na, and K. the above.

(3): The optical glass according to (1) or (2), the refractive index (n _d ) and the Abbe number (ν _d ) satisfy (-0.01×ν _d +2.03) n _d (-0.01 × ν _d + 2.13) relationship.

(4) A preform comprising the optical glass according to any one of (1) to (3).

(5): An optical element comprising the optical glass according to any one of (1) to (3).

(6): An optical instrument comprising the optical element described in (5).

According to the present invention, it is possible to obtain an optical glass having a refractive index (n _d ) and an Abbe number (ν _d ) within a desired range, a partial dispersion is relatively low, and a temperature coefficient of relative refractive index is small. .

1 is a schematic diagram showing a regular line represented by a rectangular coordinate with a partial dispersion ratio (θ _g , F) as a vertical axis and an Abbe number (ν _d ) as a horizontal axis; FIG. 2 is a partial dispersion of an embodiment of the present invention; A schematic diagram of the relationship between (θ _g , F) and Abbe number (ν _d ); FIG. 3 is a schematic diagram showing the relationship between the refractive index (n _d ) and the Abbe number (ν _d ) in the embodiment of the present invention.

The optical glass of the present invention is characterized by containing 20.0% to 45.0% of the SiO ₂ component, 25.0% to 60.0% of the Nb ₂ O ₅ component, and 0% to 5.0% of the TiO ₂ component, by mass% of the oxide conversion composition. The mass ratio (Li ₂ O/Na ₂ O+K ₂ O) is 0.40 to 1.00, and the partial dispersion ratio (θ _g , F) and the Abbe number (ν _d ) satisfy (-0.00162×ν _d +0.620). (θ _g , F) The relationship of (-0.00162 × ν _d + 0.657) has a small temperature coefficient of relative refractive index.

An optical glass containing a predetermined amount of a SiO ₂ component and a Nb ₂ O ₅ component and containing 5.0% or less of a TiO ₂ component can obtain a high refractive index, an Abbe number (high dispersion), and a low partial dispersion ratio in a desired range. glass. In particular, by keeping the content of TiO ₂ at 5.0% or less, the temperature coefficient of the relative refractive index can be lowered while keeping the partial dispersion ratio (θ _g , F) small.

Therefore, it is possible to obtain a desired high refractive index (n _d ) and low Abbe number (ν _d ), and the partial dispersion ratio (θ _g , F) is small, which is advantageous for reducing the chromatic aberration of the optical system. And an optical glass having a relatively small temperature coefficient of relative refractive index.

Hereinafter, the embodiment of the optical glass of the present invention will be described in detail, but the present invention is not limited to the following embodiments, and can be appropriately modified and implemented within the scope of the object of the present invention. In addition, the description of the part which repeats description is abbreviate|omitted suitably, and does not restrict the summary of this invention.

[Glass composition]

The composition range of each component constituting the optical glass of the present invention is as follows. In the present specification, the content of each component is expressed by mass% of the total mass of the glass in terms of oxide composition, unless otherwise specified. Here, the "oxide-converting composition" means that the oxide, the composite salt, the metal fluoride or the like used as the raw material of the glass constituent component of the present invention is decomposed into an oxide at the time of melting, and the oxidation is formed. The total mass of the material is set to 100% by mass to indicate the composition of various components contained in the glass.

<About essential ingredients, optional ingredients>

The SiO ₂ component is an essential component which promotes the stability of glass formation, lowers the liquidus temperature, and reduces undesirable devitrification (crystal formation) in the optical glass.

In particular, by setting the content of the SiO ₂ component to 20.0% or more, it is possible to obtain a glass which is excellent in devitrification resistance without greatly increasing the partial dispersion ratio. In addition, devitrification and coloring can be reduced. Therefore, the content of the SiO ₂ component is preferably 20.0% or more, preferably 23.0% or more, and more preferably 25.0% or more.

On the other hand, when the content of the SiO ₂ component is 45.0% or less, the refractive index is hard to be lowered, and a desired high refractive index can be easily obtained, and an increase in the partial dispersion ratio can be suppressed. Further, it is also possible to suppress the decrease in the meltability of the glass raw material. Therefore, the content of the SiO ₂ component is preferably 45.0% or less, preferably 43.0% or less, more preferably 41.5% or less, and most preferably 40.0% or less.

As the SiO ₂ component, SiO ₂ , K ₂ SiF ₆ , Na ₂ SiF ₆ or the like can be used as a raw material.

The Nb ₂ O ₅ component is an essential component, which can increase the refractive index, reduce the Abbe number and the partial dispersion ratio, and can improve the devitrification resistance.

In particular, by setting the content of the Nb ₂ O ₅ component to 25.0% or more, the composition is adjusted within the composition of the present invention, and the refractive index is increased until the target optical constant is reached, whereby the abnormal dispersion property can be reduced. Therefore, the content of the Nb ₂ O ₅ component is preferably 25.0% or more, preferably 30.0% or more, and more preferably 35.5% or more.

On the other hand, by setting the content of the Nb ₂ O ₅ component to 60.0% or less, the cost of the glass material can be reduced. Further, it is also possible to suppress an increase in the melting temperature at the time of glass production and to reduce devitrification caused by excessive inclusion of the Nb ₂ O ₅ component. In addition, it is also possible to improve the chemical durability of the glass. Therefore, the content of the Nb ₂ O ₅ component is preferably 60.0% or less, preferably 55.0% or less, preferably 50.0% or less, more preferably 48.0% or less.

As the Nb ₂ O ₅ component, Nb ₂ O ₅ or the like can be used as a raw material.

The TiO ₂ component is an optional component, and when the content is more than 0%, the refractive index can be increased, the Abbe number can be lowered, and the devitrification resistance can be improved. On the other hand, if the content is too large, the partial dispersion ratio becomes large.

Therefore, by setting the content of the TiO ₂ component to 5.0% or less, the coloring of the glass can be lowered, and the internal transmittance can be improved. Further, it is difficult to increase the partial dispersion ratio, and it is easy to obtain a low partial dispersion ratio which is close to the regular line, that is, expected. Therefore, the content of the TiO ₂ component is preferably 5.0% or less, more preferably 4.8% or less, still more preferably less than 4.5%.

As the TiO ₂ component, TiO ₂ or the like can be used as a raw material.

The K ₂ O component is an optional component, and when the content is more than 0%, the thermal expansion coefficient can be increased, and the temperature coefficient of the relative refractive index can be made small.

Therefore, the content of the K ₂ O component is preferably more than 0%, more preferably more than 0.3%, most preferably more than 0.5%.

On the other hand, by setting the content of the K ₂ O component to 10.0% or less, it is possible to suppress an increase in the partial dispersion ratio and to reduce devitrification. Therefore, the content of the K ₂ O component is preferably 10.0% or less, more preferably less than 8.0%, still more preferably less than 5.0%.

As the K ₂ O component, K ₂ CO ₃ , KNO ₃ , KF, KHF ₂ , K ₂ SiF ₆ or the like can be used as a raw material.

The B ₂ O ₃ component is an optional component. When the content is more than 0%, the stability of glass formation is promoted. Further, since the liquidus temperature can be lowered, the devitrification resistance can be improved and the meltability of the glass raw material can be improved. Therefore, the content of the B ₂ O ₃ component may be more preferably greater than 0%, more preferably greater than 0.3%, still more preferably greater than 0.5%.

On the other hand, when the content of the B ₂ O ₃ component is 7.0% or less, it is possible to suppress a decrease in the refractive index, and it is possible to suppress an increase in the partial dispersion ratio and to improve the chemical durability of the glass. Therefore, the content of the B ₂ O ₃ component is preferably 7.0% or less, preferably 6.0% or less, more preferably 5.0% or less.

As the B ₂ O ₃ component, H ₃ BO ₃ , Na ₂ B ₄ O ₇ , Na ₂ B ₄ O ₇ ‧10H ₂ O, BPO ₄ or the like can be used as a raw material.

The Li ₂ O component is an optional component, and when the content is more than 0%, the partial dispersion ratio can be lowered, the transmittance can be improved, the liquidus temperature can be lowered, and the meltability of the glass raw material can be improved. Therefore, the content of the Li ₂ O component is preferably more than 0%, more preferably more than 1.0%, and still more preferably more than 3.0%.

On the other hand, by setting the content of the Li ₂ O component to 15.0% or less, it is possible to suppress a decrease in the refractive index and to reduce devitrification due to excessive inclusion thereof.

Therefore, the content of the Li ₂ O component is preferably 15.0% or less, preferably 10.0% or less, and more preferably less than 7.0%.

As the Li ₂ O component, Li ₂ CO ₃ , LiNO ₃ , LiF or the like can be used as a raw material.

The Na ₂ O component is an optional component, and when the content is more than 0%, the partial dispersion ratio can be lowered, the thermal expansion coefficient is increased, and the temperature coefficient of the relative refractive index is made small. Therefore, the content of the Na ₂ O component may be more preferably greater than 0%, more preferably greater than 1.0%, still more preferably greater than 3.0%.

On the other hand, by setting the content of the Na ₂ O component to 15.0% or less, it is possible to suppress a decrease in the refractive index and to reduce devitrification caused by excessive inclusion thereof.

Therefore, the content of the Na ₂ O component is preferably 15.0% or less, preferably 10.0% or less, more preferably less than 8.0%.

As the Na ₂ O component, Na ₂ CO ₃ , NaNO ₃ , NaF, Na ₂ SiF ₆ or the like can be used as a raw material.

The Rn ₂ O component (wherein Rn is one or more selected from the group consisting of Li, Na, and K) is an arbitrary component, and when the sum (mass sum) of the contents is more than 0%, the relative refractive index temperature can be obtained. The coefficient becomes smaller. Therefore, the sum of the Rn ₂ O components is preferably greater than 0%, preferably greater than 3.0%, preferably greater than 5.0%, and more preferably greater than 8.0%.

On the other hand, it is possible to strengthen the glass by setting the sum (mass sum) of the content of the Rn ₂ O component (wherein Rn is one or more selected from the group consisting of Li, Na, and K) to 20.0% or less. The viscosity in the mold improves the formability. Therefore, 20.0% or less is preferable, preferably 19.0% or less, and more preferably 18.0% or less.

The ZrO ₂ component is an optional component, and when the content is more than 0%, the refractive index and Abbe number of the glass can be increased, the partial dispersion ratio can be lowered, and the devitrification resistance can be improved. In addition, it also reduces devitrification and coloration. Therefore, the content of the ZrO ₂ component is preferably more than 0%, preferably more than 1.0%, and more preferably more than 3.0%.

On the other hand, by setting the content of the ZrO ₂ component to 15.0% or less, devitrification can be reduced, and a homogeneous glass can be easily obtained. Therefore, the upper limit of the content of the ZrO ₂ component is preferably 15.0% or less, preferably 10.0% or less, and more preferably 8.0% or less.

As the ZrO ₂ component, ZrO ₂ , ZrF ₄ or the like can be used as a raw material.

The MgO component is an optional component, and when the content is more than 0%, the melting temperature of the glass can be lowered.

On the other hand, by setting the content of the MgO component to 10.0% or less, it is possible to reduce the devitrification while suppressing the decrease in the refractive index. Therefore, the content of the MgO component is preferably 10.0% or less, more preferably less than 5.0%, still more preferably less than 3.0%.

As the MgO component, MgO, MgCO ₃ , MgF ₂ or the like can be used as a raw material.

When the CaO component is an optional component, when the content is more than 0%, the Abbe number and devitrification can be reduced while reducing the cost of the glass material, and the meltability of the glass raw material can be improved.

On the other hand, by setting the content of the CaO component to 10.0% or less, it is possible to suppress a decrease in the refractive index, an increase in the Abbe number, and an increase in the partial dispersion ratio, and it is possible to reduce devitrification. Therefore, the content of the CaO component is preferably 10.0% or less, more preferably less than 7.0%, still more preferably less than 5.0%.

As the CaO component, CaCO ₃ , CaF ₂ or the like can be used as a raw material.

The SrO component is an optional component, and when the content is more than 0%, the refractive index can be increased and the devitrification resistance can be improved.

In particular, by setting the content of the SrO component to 10.0% or less, deterioration in chemical durability can be suppressed. Therefore, the content of the SrO component is preferably 10.0% or less, preferably less than 8.0%, more preferably less than 6.0%, still more preferably less than 5.0%.

As the SrO component, Sr(NO ₃ ) ₂ , SrF ₂ or the like can be used as a raw material.

The BaO component is an optional component, and when the content is more than 0%, the refractive index and the devitrification resistance can be improved, and the thermal expansion coefficient can be increased to lower the temperature coefficient of the relative refractive index.

In particular, by setting the content of the BaO component to 5.0% or less, it is possible to suppress a decrease in the refractive index, an increase in the Abbe number, and an increase in the partial dispersion ratio, and it is possible to reduce devitrification. Therefore, the content of the BaO component is preferably 5.0% or less, more preferably less than 4.0%, still more preferably less than 3.0%, still more preferably less than 1.0%.

As the BaO component, BaCO ₃ , Ba(NO ₃ ) ₂ or the like can be used as a raw material.

The ZnO component is an optional component, and when the content is more than 0%, the glass is inexpensive, the devitrification resistance can be improved, and the glass transition temperature can be lowered. Therefore, the content of the ZnO component may preferably be more than 0%, preferably more than 0.1%, more preferably more than 0.3%.

On the other hand, by setting the content of the ZnO component to 10.0% or less, devitrification and coloring can be reduced. Therefore, the content of the ZnO component is preferably 10.0% or less, preferably 8.0% or less, and more preferably 6.0% or less.

The La ₂ O ₃ component, the Gd ₂ O ₃ component, the Y ₂ O ₃ component, and the Yb ₂ O ₃ component are optional components, and when the content of at least one component is more than 0%, the refractive index can be increased and the partial dispersion ratio can be made small.

In particular, by setting the content of each of the La ₂ O ₃ component, the Gd ₂ O ₃ component, the Y ₂ O ₃ component, and the Yb ₂ O ₃ component to 10.0% or less, it is possible to suppress an increase in the Abbe number and reduce devitrification. And reduce material costs. Therefore, the content of each of the La ₂ O ₃ component, the Gd ₂ O ₃ component, the Y ₂ O ₃ component, and the Yb ₂ O ₃ component is preferably 10.0% or less, more preferably 7.0% or less, still more preferably less than 5.0%.

La ₂ O ₃ component, Gd ₂ O ₃ component, Y ₂ O ₃ component, and Yb ₂ O ₃ component can be La ₂ O ₃ or La(NO ₃ ) ₃ ‧ XH ₂ O (X is an arbitrary integer), Y ₂ O ₃ , YF ₃ , Gd ₂ O ₃ , GdF ₃ , Yb ₂ O ₃ or the like is used as a raw material.

The Ta ₂ O ₅ component is an optional component, and when the content is more than 0%, the refractive index can be increased, the Abbe number and the partial dispersion ratio can be lowered, and the devitrification resistance can be improved.

On the other hand, by setting the content of the Ta ₂ O ₅ component to 10.0% or less, the amount of the Ta ₂ O ₅ component which is a rare mineral resource can be reduced, and the glass is more easily melted at a low temperature, so that the production of the glass can be reduced. cost. Further, by this, it is possible to reduce the devitrification of the glass due to the excessive content of the Ta ₂ O ₅ component. Therefore, the content of the Ta ₂ O ₅ component is preferably 10.0% or less, more preferably less than 5.0%, still more preferably less than 3.0%, still more preferably less than 1.0%. In particular, from the viewpoint of reducing the material cost of the glass, the Ta ₂ O ₅ component may not be contained.

As the Ta ₂ O ₅ component, Ta ₂ O ₅ or the like can be used as a raw material.

The WO ₃ component is an optional component, and when the content is more than 0%, the refractive index can be lowered to reduce the Abbe number, the devitrification resistance can be improved, and the meltability of the glass raw material can be improved.

On the other hand, by setting the content of the WO ₃ component to 10.0% or less, it is possible to make it difficult to increase the partial dispersion ratio of the glass, and to lower the color of the glass to improve the internal transmittance. Therefore, the content of the WO ₃ component is preferably 10.0% or less, more preferably less than 5.0%, still more preferably less than 3.0%, still more preferably less than 1.0%.

As the WO ₃ component, WO ₃ or the like can be used as a raw material.

The P ₂ O ₅ component is an optional component, and when the content is more than 0%, the stability of the glass can be improved.

On the other hand, by setting the content of the P ₂ O ₅ component to 10.0% or less, devitrification due to excessive content of the P ₂ O ₅ component can be reduced. Therefore, the content of the P ₂ O ₅ component is preferably 10.0% or less, more preferably less than 5.0%, still more preferably less than 3.0%.

As the P ₂ O ₅ component, Al(PO ₃ ) ₃ , Ca(PO ₃ ) ₂ , Ba(PO ₃ ) ₂ , BPO ₄ , H ₃ PO ₄ or the like can be used as a raw material.

The GeO ₂ component is an optional component, and when the content is more than 0%, the refractive index can be increased and devitrification can be reduced.

On the other hand, by setting the content of the GeO ₂ component to 10.0% or less, the amount of the expensive GeO ₂ component used can be reduced, so that the material cost of the glass can be reduced. Therefore, the content of the GeO ₂ component is preferably 10.0% or less, more preferably less than 5.0%, still more preferably less than 3.0%.

As the GeO ₂ component, GeO ₂ or the like can be used as a raw material.

The Al ₂ O ₃ component and the Ga ₂ O ₃ component are optional components, and when the content of at least one of the components is more than 0%, the refractive index can be increased and the devitrification resistance can be improved.

On the other hand, by setting the content of the Al ₂ O ₃ component and the Ga ₂ O ₃ component to 10.0% or less, it is possible to reduce devitrification caused by excessive inclusion of the Al ₂ O ₃ component or the Ga ₂ O ₃ component. Therefore, the content of each of the Al ₂ O ₃ component and the Ga ₂ O ₃ component is preferably 10.0% or less, more preferably less than 5.0%, still more preferably less than 3.0%.

As the Al ₂ O ₃ component and the Ga ₂ O ₃ component, Al ₂ O ₃ , Al(OH) ₃ , AlF ₃ , Ga ₂ O ₃ , Ga(OH) ₃ or the like can be used as a raw material.

The Bi ₂ O ₃ component is an optional component, and when the content is more than 0%, the refractive index can be lowered to reduce the Abbe number, and the glass transition temperature can be lowered.

On the other hand, by setting the content of the Bi ₂ O ₃ component to 10.0% or less, it is possible to make it difficult to increase the partial dispersion ratio, and it is possible to reduce the color of the glass and increase the internal transmittance. Therefore, the content of the Bi ₂ O ₃ component is preferably 10.0% or less, more preferably less than 5.0%, still more preferably less than 3.0%, still more preferably less than 1.0%.

As the Bi ₂ O ₃ component, Bi ₂ O ₃ or the like can be used as a raw material.

The TeO ₂ component is an optional component, and when the content is more than 0%, the refractive index can be increased, the partial dispersion ratio can be lowered, and the glass transition temperature can be lowered.

On the other hand, by setting the content of the TeO ₂ component to 5.0% or less, the color of the glass can be lowered to increase the internal transmittance. In addition, by reducing the costly use of the TeO ₂ component, it is possible to obtain a glass having a low material cost. Therefore, the content of the TeO ₂ component is preferably 5.0% or less, more preferably less than 3.0%, still more preferably less than 1.0%.

As the TeO ₂ component, TeO ₂ or the like can be used as a raw material.

The SnO ₂ component is an optional component, and when the content is more than 0%, the glass after melting can be made clear (foaming), and the visible light transmittance of the glass can be improved.

On the other hand, when the content of the SnO ₂ component is 1.0% or less, coloring of the glass or devitrification of the glass due to reduction of the molten glass can be prevented from occurring. Further, since the alloying between the SnO ₂ component and the melting device (particularly a noble metal such as Pt) is reduced, it is desirable to extend the life of the melting device. Therefore, the content of the SnO ₂ component is preferably 1.0% or less, more preferably less than 0.5%, still more preferably less than 0.1%.

As the SnO ₂ component, SnO, SnO ₂ , SnF ₂ , SnF ₄ or the like can be used as a raw material.

The Sb ₂ O ₃ component is an optional component in the optical glass of the present invention, and when the content is more than 0%, the defoaming of the glass is promoted to make the glass clear. When the content of the Sb ₂ O ₃ component is 1.0% or less, it is difficult to cause excessive bubbles in the glass during melting, and it is difficult to alloy the Sb ₂ O ₃ component with a melting device (particularly, a noble metal such as Pt). Therefore, the content of the Sb ₂ O ₃ component is preferably 1.0%, preferably 0.8%, more preferably 0.6%.

As the Sb ₂ O ₃ component, Sb ₂ O ₃ , Sb ₂ O ₅ , Na ₂ H ₂ Sb ₂ O ₇ ‧5H ₂ O or the like can be used as a raw material.

Further, the component which makes the glass clear and defoamed is not limited to the SnO ₂ component or the Sb ₂ O ₃ component described above, and a clarifier, an antifoaming agent or a combination thereof which is conventionally known in the field of glass production can be used.

The mass ratio of Li ₂ O to Na ₂ O and K ₂ O is preferably 1.38 or less. Thereby, deterioration of devitrification property can be suppressed. Therefore, the mass ratio of Li ₂ O/(Na ₂ O+K ₂ O) is preferably 1.38 or less, preferably 1.00 or less, preferably 0.95 or less, more preferably 0.90 or less.

On the other hand, when the mass ratio Li ₂ O/(Na ₂ O+K ₂ O) is 0.40 or more, a glass having a relatively small partial dispersion can be obtained. Therefore, it is preferably 0.40 or more, more preferably 0.45 or more, still more preferably 0.50 or more.

The ratio of TiO ₂ to Li ₂ O is preferably 1.42 or less. Thereby, the devitrification of the glass can be reduced. Therefore, the mass ratio of TiO ₂ /Li ₂ O system is preferably 1.00 or less, preferably 0.95 or less, more preferably 0.90 or less.

On the other hand, when the mass ratio TiO ₂ /Li ₂ O is more than 0, the transmittance can be prevented from being deteriorated, and the partial dispersion ratio can be made small. Therefore, it is preferably more than 0, preferably 0.20 or more, preferably 0.25 or more, more preferably 0.30 or more.

The Rn ₂ O component (wherein Rn is one or more selected from the group consisting of Li, Na, and K) and Nb ₂ O ₅ are preferably 0.50 or less. Thereby, the desired refractive index can be obtained, and the partial dispersion ratio becomes small. Therefore, the mass ratio Rn ₂ O/Nb ₂ O ₅ is preferably 0.50 or less, preferably 0.48 or less, or preferably 0.45 or less.

On the other hand, by setting the mass ratio Rn ₂ O/Nb ₂ O ₅ to 0.10 or more, the temperature coefficient of the relative refractive index can be lowered. Therefore, it is preferably 0.10 or more, more preferably 0.20 or more, still more preferably 0.25 or more.

The ratio of SiO ₂ to Nb ₂ O ₅ is preferably 0.50 or more. Thereby, the partial dispersion ratio can be made small, and the stability of the glass becomes good. Therefore, the lower limit is preferably 0.50 or more, more preferably 0.55 or more, still more preferably 0.60 or more.

On the other hand, the ratio of SiO ₂ to Nb ₂ O ₅ is preferably 1.00 or less. Therefore, the upper limit is preferably 1.00 or less, preferably 0.95 or less, more preferably 0.90 or less. Thereby, a high refractive index can be obtained and the expected Abbe number is obtained.

The total of TiO ₂ , Nb ₂ O ₅ and ZrO ₂ is preferably 35.0% or more. Thereby, the partial dispersion ratio becomes small, and the refractive index and the Abbe number are the expected values. Therefore, the mass and (TiO ₂ + Nb ₂ O ₅ + ZrO ₂ ) are preferably 35.0% or more, preferably 38.0% or more, preferably 40.0% or more, and more preferably 45.0% or more.

On the other hand, the mass and (TiO ₂ + Nb ₂ O ₅ + ZrO ₂ ) are preferably 70.0% or less. Thereby, deterioration of devitrification property can be suppressed, and transmittance can be further improved. 70.0% or less is preferably, preferably less than 65.0%, more preferably less than 60.0%, still more preferably less than 58.0%.

The ratio of ZrO ₂ to Nb ₂ O ₅ is preferably 0.01 or more. Thereby, the partial dispersion ratio becomes small, and the high refractive index is obtained while the devitrification is better. Therefore, the mass ratio of ZrO ₂ /Nb ₂ O ₅ is preferably 0.01 or more, preferably 0.05 or more, more preferably more than 0.10.

On the other hand, the mass ratio of ZrO ₂ /Nb ₂ O ₅ is preferably 0.25 or less. Thereby, the stability of the glass is better, and the increase in the Abbe number can be suppressed. 0.25 or less is preferable, preferably 0.22 or less, preferably 0.20 or less, more preferably 0.15 or less.

The ratio of the Na ₂ O component to the Rn ₂ O component (wherein Rn is one or more selected from the group consisting of Li, Na, and K) is preferably 0.25 or more. Thereby, the temperature coefficient of the relative refractive index becomes small. Therefore, the mass ratio of Na ₂ O/Rn ₂ O is preferably 0.25 or more, preferably 0.27 or more, and more preferably 0.30 or more.

On the other hand, the mass ratio of Na ₂ O/Rn ₂ O is preferably 0.65 or less. Thereby, devitrification and a decrease in refractive index by reheat forming can be suppressed. It is preferably 0.65 or less, preferably 0.63 or less, more preferably 0.60 or less.

When the sum (mass sum) of the content of the RO component (where R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba) is more than 0%, the desired refractive index and dispersion can be adjusted. Therefore, the content of the RO component is preferably more than 0%, preferably more than 0.5%, more preferably more than 1.5%.

On the other hand, the sum of the RO component contents is preferably less than 9.0%. Thereby, it is possible to suppress a decrease in the refractive index of the glass and a decrease in the devitrification resistance due to excessive inclusion of the RO component. Therefore, the mass of the RO component is preferably less than 9.0%, preferably less than 7.0%, preferably 6.5% or less, more preferably 6.0% or less.

The content (mass sum) of the Ln ₂ O ₃ component (wherein Ln is one or more selected from the group consisting of La, Gd, Y, and Yb) is preferably less than 5.0%. Thereby, it is possible to suppress a decrease in the refractive index of the glass and a decrease in the devitrification resistance due to an excessive content of the Ln ₂ O ₃ component. Therefore, the mass of the Ln ₂ O ₃ component is preferably less than 5.0%, preferably 4.5% or less, more preferably 4.0% or less.

<About ingredients that should not be included>

Next, the components which should not be contained in the optical glass of the present invention and the components which are not suitable for inclusion will be described.

Other components may be added as needed within the range not impairing the characteristics of the glass of the present invention. However, in addition to Ti, Zr, Nb, W, La, Gd, Y, Yb, and Lu, various transition metal components such as V, Cr, Mn, Fe, Co, Ni, Cu, Ag, and Mo are individually or When it is contained in a composite form, even if it is contained in a small amount, the glass is colored, and the light of a specific wavelength in the visible range is absorbed. Therefore, in particular, in an optical glass using a wavelength in the visible range, it is preferable. It is not included in nature.

Further, a lead compound such as PbO or an arsenic compound such as As ₂ O ₃ is a component having a high environmental load, and is preferably substantially not contained, that is, it is not contained at all except for inevitable mixing.

Furthermore, the components of Th, Cd, Tl, Os, Be, and Se have been regarded as harmful chemical substances in recent years, and there is a tendency to avoid use, not only in the manufacturing steps of glass, but also in the processing steps and after the productization. All measures must be taken in response to environmental measures until disposal. Therefore, from the viewpoint of attaching importance to environmental influences, it is preferred that substantially no such components are contained.

[Production method]

The optical glass of the present invention can be produced, for example, in the following manner. That is, the raw materials are uniformly mixed in a predetermined content range, and the prepared mixture is put into a platinum crucible, a quartz crucible or an aluminoxane to be initially melted, and then the crucible, platinum crucible, In a platinum alloy crucible or crucible, it is melted in a temperature range of 1000 ° C to 1400 ° C for 3 hours to 5 hours, stirred to homogenize and defoamed, and then cooled to a temperature of 900 ° C to 1200 ° C, and finally The stage is stirred to remove the texture, and then cast into a mold and slowly cooled to make it.

<physical property>

The optical glass of the present invention has an Abbe number of a high refractive index and a predetermined range.

The lower limit of the refractive index (n _d ) of the optical glass of the present invention is preferably 1.70 or more, more preferably 1.72 or more, still more preferably 1.75 or more. The upper limit of the refractive index is preferably 1.90 or less, preferably 1.88 or less, preferably 1.85 or less, more preferably 1.83 or less.

The lower limit of the Abbe's number (ν _d ) of the optical glass of the present invention is preferably 25.0, more preferably 25.5, still more preferably 26.0. On the other hand, the upper limit of the Abbe number (ν _d ) of the optical glass of the present invention is preferably 35.0, more preferably 34.0, still more preferably 33.0.

Since the optical glass of the present invention has such a refractive index and an Abbe number, it can exert an effect on optical design, and in particular, it is desirable to achieve a high degree of imaging characteristics and the like, and it is also possible to reduce the size of the optical system. The freedom of optical design.

Here, the optical glass of the present invention has a refractive index (n _d ) and an Abbe number (ν _d ) to satisfy (-0.01×ν _d +2.03). n _d The relationship between (-0.01 × ν _d + 2.13) is better. The glass having a composition specific to the present invention satisfies this relationship with a refractive index (n _d ) and an Abbe number (ν _d ), and a stable glass can be obtained.

Therefore, the optical glass of the present invention has a refractive index (n _d ) and an Abbe number (ν _d ) to satisfy n _d The relationship of (-0.01×ν _d +2.03) is better, preferably satisfying n _d (-0.01 × ν _d +2.05) relationship.

On the other hand, the optical glass of the present invention has a refractive index (n _d ) and an Abbe number (ν _d ) to satisfy n _d (-0.01 × ν _d + 2.13) is preferable, preferably satisfies n _d The relationship between (-0.01×ν _d +2.10).

The optical glass of the present invention has a lower partial dispersion ratio (θ _g , F).

More specifically, the partial dispersion ratio (θ _g , F) and the Abbe number (ν _d ) of the optical glass of the present invention are satisfied to satisfy (-0.00162 × ν _d + 0.620) (θ _g , F) The relationship between (-0.00162 × ν _d + 0.657) is preferred.

Therefore, the optical glass system of the present invention has a partial dispersion ratio (θ _g , F) and an Abbe number (ν _d ) to satisfy (θ _g , F). The relationship of (-0.00162 × ν _d + 0.620) is preferred, preferably (θ _g , F) The relationship between (-0.00162 × ν _d + 0.630).

On the other hand, the optical glass system of the present invention has a partial dispersion ratio (θ _g , F) and an Abbe number (ν _d ) to satisfy θ _g , F . The relationship of (-0.00162 × ν _d + 0.657) is better, preferably θ _g , F The relationship between (-0.00162 × ν _d + 0.650).

Thereby, an optical glass having a low partial dispersion ratio (θ _g , F) can be obtained, and the optical element formed by the optical glass can function to reduce chromatic aberration of the optical system.

In addition, especially in the region where the Abbe number (ν _d ) is small, the partial dispersion ratio (θ _g , F) of the glass is generally higher than that of the regular line, and the horizontal axis is the Abbe number (ν _{d ).} When the vertical axis is the partial dispersion ratio (θ _g , F), the relationship between the partial dispersion ratio (θ _g , F) and the Abbe number (ν _d ) of the general glass is shown by a curve larger than the inclination of the regular line. . The relationship between the partial dispersion ratio (θ _g , F) and the Abbe number (ν _d ) shows that the relationship is defined by a straight line larger than the inclination of the regular line, and a partial dispersion ratio (θ _g can be obtained. , F) Glass smaller than ordinary glass.

Further, the optical glass of the present invention has a low temperature coefficient of relative refractive index (dn/dT).

More specifically, the temperature coefficient of the relative refractive index of the optical glass of the present invention is preferably +6.0×10 ^-6 ° C ^-1 , preferably +5.5×10 ^-6 ° C ^-1 , more preferably + 5.0 × 10 ^-6 ° C ^-1 , and the upper limit value or the value lower than the upper limit value (negative value side) may be taken.

On the other hand, the temperature coefficient of the relative refractive index of the optical glass of the present invention has a lower limit of -5.0 × 10 ^-6 ° C ^-1 , preferably -1.0 × 10 ^-6 ° C ^-1 , more preferably -0.5. ×10 ^-6 °C ^-1 , and the lower limit value or the value higher than the lower limit value (positive value side) can be taken.

Among them, in a glass having a refractive index (n _d ) of 1.70 or more and an Abbe number (ν _d ) of 25 or more and 35 or less, a glass having a relatively low temperature coefficient of relative refractive index is rare, so that the temperature is due to temperature. There are many choices for correcting the situation such as image defocusing caused by the change, and the correction can be completed more easily. Therefore, by setting the temperature coefficient of the relative refractive index to the above range, it is possible to contribute to correction of image defocusing or the like due to temperature change.

The temperature coefficient of the relative refractive index of the optical glass of the present invention means the temperature coefficient of the refractive index (589.29 nm) in the air at the same temperature as the optical glass, and the temperature is changed every 1 ° C by changing the temperature from 40 ° C to 60 ° C. The corresponding amount of change (°C ^-1 ) is expressed.

The optical glass of the present invention preferably has an average linear thermal expansion coefficient α of 80 (10 ^-7 ° C ^-1 ) or more at 100 ° C to 300 ° C. That is, the lower limit of the average linear thermal expansion coefficient α of the optical glass of the present invention at 100 ° C to 300 ° C is preferably 80 (10 ^-7 ° C ^-1 ) or more, preferably 85 (10 ^-7 ° C ^-1 ) or more. It is preferably 90 (10 ^-7 ° C ^-1 ) or more.

In general, in the case of glass processing, when the average linear thermal expansion coefficient α is large, cracking easily occurs, and therefore the average linear thermal expansion coefficient α is desirably small. On the other hand, in terms of bonding with a combination of a glass material having a relatively low temperature coefficient of relative refractive index and a large average linear thermal expansion coefficient α, it is desirable that the value of the average linear thermal expansion coefficient α is the same as that of the glass material or similar.

Among them, in a glass having a refractive index (n _d ) of 1.70 or more and an Abbe number (ν _d ) of 25 or more and 35 or less, a glass material having a large average linear thermal expansion coefficient α is small, and a low refractive index and a low dispersion are included. When the glass materials are used in combination, the average linear thermal expansion coefficient α as shown in the present invention is more useful.

The optical glass of the present invention desirably has a small specific gravity. More specifically, the optical glass of the present invention preferably has a specific gravity of 5.00 (g/cm ³ ) or less. Thereby, the quality of the optical element and the optical instrument using the optical element can be reduced, and the weight of the optical instrument can be reduced.

Therefore, the upper limit of the specific gravity of the optical glass of the present invention is preferably 5.00, more preferably 4.70, still more preferably 4.50. Further, the specific gravity of the optical glass of the present invention is generally 2.80 or more, more specifically 2.90 or more, and more specifically 3.00 or more.

The specific gravity of the optical glass of the present invention is measured in accordance with the Japanese Optical Glass Industry Association Standard JOGIS05-1975 "Method for Measuring Specific Gravity of Optical Glass".

[Preforms and optical components]

A glass molded body can be produced from the produced optical glass by a method of press molding such as re-compression molding or precision press molding. In other words, a preform for press molding can be produced from optical glass, and the preform can be subjected to reheat forming, followed by polishing to prepare a glass molded body, or preformed by polishing. The body is subjected to precision press forming to produce a glass molded body or the like. Further, the method of producing the glass molded body is not limited to the above methods.

The glass molded body produced as above can be applied to various optical elements, and its use is particularly suitable for optical elements such as lenses or iridium. Thereby, the transmitted light due to the chromatic aberration can be alleviated for the transmitted light of the optical system provided with the optical element. Therefore, when the optical element is used for a viewing window, the object to be photographed can be more accurately expressed, and when the optical element is used for a projector, the desired mapping can be projected with higher sharpness.

[Examples]

The compositions of the examples (No. 1 to No. 12) and comparative examples of the present invention, and the refractive index (n _d ), the Abbe number (ν _d ), the partial dispersion ratio (θ _g , F), and the relative refractive index The results of temperature coefficient (dn/dT), average linear thermal expansion coefficient (100-300 ° C), and specific gravity are shown in Tables 1 to 2. Further, the following examples are for illustrative purposes only, and the invention is not limited to the embodiments.

In the glass of the examples and comparative examples of the present invention, the raw materials of the respective components are high-purity raw materials selected for general optical glass such as oxides, hydroxides, carbonates, nitrates, fluorides, and metaphosphoric acid compounds. Further, these raw materials were weighed so as to have a composition ratio of each of the examples and the comparative examples shown in the table, and uniformly mixed, and then charged into a quartz crucible (a platinum crucible or an alumina crucible may be used depending on the meltability of the glass). In accordance with the melting difficulty of the glass composition, the electric furnace is melted in a temperature range of 1100 ° C to 1400 ° C for 0.5 to 5 hours, then transferred to a platinum crucible, stirred to homogenize and defoamed, and then cooled. After the temperature is from 1000 ° C to 1200 ° C, it is stirred again to make it uniform, and then cast into a mold and slowly cooled to obtain a glass.

The refractive index (n _d ), the Abbe number (ν _d ), and the partial dispersion ratio (θ _g , F) of the glasses of the examples and the comparative examples were measured in accordance with the Japan Optical Glass Industry Association standard JOGIS01-2003.

The temperature coefficient (dn/dT) of the relative refractive index of the glass of the examples and the comparative examples is the interference in the method described in the Japanese Optical Glass Industry Association Standard JOGIS18-2008 "Method for Measuring the Temperature Coefficient of the Refractive Index of Optical Glass". The value of the temperature coefficient of the relative refractive index of the light having a wavelength of 589.29 nm at 40 ° C to 60 ° C was measured.

In addition, the average linear thermal expansion coefficient (100-300 ° C) of the glass of the Example and the comparative example was measured by the Japan Optical Glass Industry Association standard JOGIS08-2003 "Measurement method of thermal expansion of optical glass" by measuring temperature and elongation of a sample. The thermal expansion curve obtained by the relationship of the ratio is obtained.

The glass specific gravity of the examples and the comparative examples was measured in accordance with the Japanese Optical Glass Industry Association Standard JOGIS05-1975 "Method for Measuring Specific Gravity of Optical Glass".

The optical glass-based refractive index (n _d ) of the embodiment of the present invention is 1.70 or more, more specifically 1.72 or more, and the refractive index (n _d ) is 1.90 or less, and more specifically 1.88 or less, which is expected In the range.

Further, the optical glass of the embodiment of the present invention has an Abbe number (ν _d ) of 25 or more, more specifically 26 or more, and the Abbe number (ν _d ) is 35 or less, and all of them are within a desired range.

As shown in the above tables, the optical glass system partial dispersion ratio (θ _g , F) and the Abbe number (ν _d ) of the embodiment of the present invention satisfy (-0.00162 × ν _d + 0.620). (θ _g , F) The relationship of (-0.00162 × ν _d +0.657), in more detail (-0.00162 × ν _d +0.630) (θ _g , F) The relationship between (-0.00162 × ν _d + 0.650). That is, regarding the relationship between the partial dispersion ratio (θ _g , F) of the glass of the embodiment of the present invention and the Abbe number (ν _d ), the result is shown in Fig. 2 .

On the other hand, the optical glass system of the comparative example was not satisfied (-0.00162 × ν _d + 0.620) (θ _g , F) The relationship between (-0.00162 × ν _d + 0.657).

Moreover, the optical glass system of the embodiment of the present invention satisfies (-0.01×ν _d +2.03) between the refractive index (n _d ) and the Abbe number (ν _d ). n _d (-0.01 × ν _d + 2.13) relationship, in more detail (-0.01 × ν _d +2.05) n _d The relationship between (-0.01×ν _d +2.10). That is, regarding the relationship between the refractive index (n _d ) and the Abbe number (ν _d ) of the glass of the embodiment of the present application, the results are shown in FIG.

As shown in the table, the temperature coefficient of the relative refractive index of the optical glass of the examples is in the range of +6.0×10 ^-6 (°C ^-1 ) to -0.5×10 ^-6 (°C ^-1 ), which is desirable. Within the scope.

Further, the optical glass of the present invention has an average linear thermal expansion coefficient α of 80 (10 ^-7 ° C ^-1 ) or more at 100 ° C to 300 ° C.

Further, the optical glass of the embodiment of the present invention has a specific gravity of 5.00 or less. Therefore, it is clear that the optical glass of the embodiment of the present invention has a small specific gravity.

Further, the glass brick is formed using the optical glass of the embodiment of the present invention, and the glass brick is ground and polished to be processed into a lens and a serpentine shape. As a result, it can be stably processed into various lenses and shapes of the crucible.

The present invention has been described in detail above with reference to the embodiments of the present invention, which is intended to be Many modifications can be made to the invention.

Claims (6)

An optical glass containing, by mass%, 20.0% to 45.0% of SiO ₂ component; 25.0% to 60.0% of Nb ₂ O ₅ component; 0% to 5.0% of TiO ₂ component; and mass ratio (Li ₂ O/Na ₂ O+K ₂ O) is between 0.40 and 1.00; the partial dispersion ratio (θ _g , F) and the Abbe number ν _d are satisfied (-0.00162×ν _d +0.620) (θ _g , F) (-0.00162 × ν _d + 0.657), the relative refractive index (589.29 nm) temperature coefficient (40 ° C to 60 ° C) in the range of +6.0 × 10 ^-6 to -5.0 × 10 ^-6 (°C ^-1 ) Inside. The optical glass according to claim 1, wherein the mass ratio (Rn ₂ O/Nb ₂ O ₅ ) is 0.50 or less, and Rn in the formula is one or more selected from the group consisting of Li, Na, and K. The optical glass according to claim 1 or 2, wherein the refractive index n _d and the Abbe number ν _d satisfy (-0.01×ν _d +2.03) n _d (-0.01 × ν _d + 2.13) relationship.  A preform comprising the optical glass as recited in claim 1 or 2.    An optical element comprising the optical glass as recited in claim 1 or 2.    An optical instrument comprising the optical element as recited in claim 5.