JP2018072419A - Magnetic glass lens - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic glass lens that can achieve both of a high magnetization rate and a high light transmittance at a use wavelength.SOLUTION: A magnetic glass lens contains TbOof more than 40 mol% in terms of oxide, where, the ratio of Tbcontent to the total Tb content is 55 mol% or more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a magnetic glass lens suitable for an autofocus lens of a camera.

  Digital cameras, camera-equipped mobile phones, and the like have a drive device for changing the focal length of the camera, that is, moving the autofocus lens to a predetermined position in order to enable close-up shooting, normal shooting, and distant shooting. Is provided. Conventionally, such a lens driving device has been provided with a lens holder for fixing the lens and a spring for moving the lens holder.

  However, since the drive device as described above requires a lens holder and a spring, it cannot meet the recent demands for downsizing of digital cameras, camera-equipped mobile phones, and the like. Therefore, a method has been proposed in which the lens itself is moved by a magnet by using a magnetic glass lens (see Patent Document 1).

JP 2004-29668 A

  In order to sufficiently move the magnetic glass lens by the magnet, an improvement in magnetic susceptibility is required. Although the above magnetic glass lens shows a certain degree of magnetic susceptibility, in recent years, since the miniaturization of digital cameras and camera-equipped mobile phone types has progressed further, even a small magnet can be moved sufficiently. Further improvement in magnetic susceptibility is required. In order to increase the magnetic susceptibility, it is effective to increase the Tb content in the magnetic glass lens. In that case, however, the light transmittance at the used wavelength (for example, 400 to 1100 nm) tends to decrease, and the digital camera There is a problem that the light extraction efficiency of a mobile phone with a camera is inferior.

  In view of the above, an object of the present invention is to provide a magnetic glass lens capable of achieving both a high magnetic susceptibility and a high light transmittance at a used wavelength.

The magnetic glass lens of the present invention contains more than 40% of Tb ₂ O ₃ in terms of mol% of oxide, and the ratio of Tb ³⁺ to the total Tb is 55% or more in mol%. .

The magnetic glass lens of the present invention can achieve a high magnetic susceptibility by containing a large amount of Tb ₂ O ₃ as described above. By the way, the magnetic glass containing Tb exists in a state where Tb is mainly Tb ³⁺ and Tb ⁴⁺ . Here, Tb ³⁺ has a relatively small light absorption in the wavelength range of 400 to 1100 nm, whereas Tb ⁴⁺ has a wide light absorption in the wavelength range of 400 to 1100 nm, which causes a decrease in light transmittance. In the magnetic glass lens of the present invention, since the ratio of Tb ^{3+ to} the total Tb is large as described above, light absorption in the wavelength range of 400 to 1100 nm due to Tb ⁴⁺ is small, and the light transmittance is excellent.

  The magnetic glass lens of the present invention preferably has a light transmittance of 60% or more at an optical path length of 1 mm at a wavelength of 633 nm.

The magnetic glass lens of the present invention preferably further contains, in mol%, SiO ₂ 0 to 50%, B ₂ O ₃ 0 to 50%, and Al ₂ O ₃ 0 to 50%.

  According to the present invention, it is possible to provide a magnetic glass lens capable of achieving both a high magnetic susceptibility and a high light transmittance at a used wavelength.

It is typical sectional drawing which shows one Embodiment of the apparatus for manufacturing precursor glass.

The magnetic glass lens of the present invention contains more than 40% of Tb ₂ O ₃ in terms of mol% of oxide, and is preferably 45% or more, 48% or more, 49% or more, particularly 50% or more. Thus, by increasing the content of Tb ₂ O ₃ , a good magnetic susceptibility (for example, 1 × 10 ⁻³ emu / mol or more, further 2 × 10 ⁻² emu / mol or more at room temperature) can be obtained. It becomes easy to obtain. In addition, although Tb which exists in glass exists in a trivalent or tetravalent state, all of these are represented as Tb ₂ O _{3 in the} present invention.

In the magnetic glass lens of the present invention, the ratio of Tb ^{3+ to} the total Tb is 55% or more in mol%, and is 60% or more, 70% or more, 80% or more, 90% or more, particularly 95% or more. preferable. If the ratio of Tb ^{3+ to} the total Tb is too small, the light transmittance at a wavelength of 400 to 1100 nm tends to decrease.

The magnetic glass lens of the present invention can contain the following components in addition to Tb ₂ O ₃ . In the following description of the content of each component, “%” means “mol%” unless otherwise specified.

SiO ₂ becomes a glass skeleton and is a component that widens the vitrification range. However, since it does not contribute to the improvement of the magnetic susceptibility, it is difficult to obtain a sufficient magnetic susceptibility if the content is too large. Therefore, the content of SiO ₂ is preferably 0 to 50%, particularly 1 to 35%.

B ₂ O ₃ becomes a glass skeleton and is a component that widens the vitrification range. However, since B ₂ O ₃ does not contribute to the improvement of the magnetic susceptibility, it is difficult to obtain a sufficient magnetic susceptibility if its content is too large. Therefore, the content of B ₂ O ₃ is preferably 0 to 50%, particularly 1 to 40%.

Al ₂ O ₃ is a component that enhances glass forming ability. However, since Al ₂ O ₃ does not contribute to the improvement of the magnetic susceptibility, it is difficult to obtain a sufficient magnetic susceptibility if the content is too large. Therefore, the content of Al ₂ O ₃ is preferably 0 to 50%, particularly preferably 0 to 30%.

La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ and Yb ₂ O ₃ have the effect of stabilizing vitrification. However, when there is too much the content, it will become difficult to vitrify on the contrary. Therefore, the contents of La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ and Yb ₂ O ₃ are each preferably 10% or less, particularly preferably 5% or less.

Dy ₂ O ₃ , Eu ₂ O ₃ and Ce ₂ O ₃ stabilize vitrification and contribute to the improvement of magnetic susceptibility. However, when there is too much the content, it will become difficult to vitrify on the contrary. Also, the glass is colored. Therefore, the contents of Dy ₂ O ₃ , Eu ₂ O ₃ and Ce ₂ O ₃ are each preferably 15% or less, particularly preferably 10% or less. In addition, although Dy, Eu, and Ce existing in the glass exist in a trivalent or tetravalent state, in the present invention, these are all represented as Dy ₂ O ₃ , Eu ₂ O ₃ , and Ce ₂ O ₃ , respectively.

  MgO, CaO, SrO, and BaO have effects of stabilizing vitrification and improving chemical durability. However, since it does not contribute to the improvement of the magnetic susceptibility, it is difficult to obtain a sufficient magnetic susceptibility if the content is excessive. Therefore, the content of these components is preferably 0 to 10%, particularly 0 to 5%.

GeO ₂ is a component that enhances glass forming ability. However, since GeO ₂ does not contribute to the improvement of the magnetic susceptibility, it is difficult to obtain a sufficient magnetic susceptibility if its content is too large. Therefore, the content of GeO ₂ is preferably 0 to 15%, 0 to 10%, particularly preferably 0 to 9%.

P ₂ O ₅ is a component that enhances glass forming ability. However, if the content is too large, devitrification tends to occur, and chemical durability tends to decrease. Moreover, since P ₂ O ₅ does not contribute to the improvement of the magnetic susceptibility, it is difficult to obtain a sufficient magnetic susceptibility if the content is too large. Therefore, the content of P ₂ O ₅ is preferably 0 to 7%, particularly preferably 0 to 5%.

Ga ₂ O ₃ has the effect of increasing the glass forming ability and expanding the vitrification range. However, when there is too much the content, it will become easy to devitrify. Moreover, since Ga ₂ O ₃ does not contribute to the improvement of the magnetic susceptibility, it is difficult to obtain a sufficient magnetic susceptibility if its content is too large. Therefore, the Ga ₂ O ₃ content is preferably 0 to 6%, particularly preferably 0 to 5%.

Fluorine has the effect of increasing the glass forming ability and expanding the vitrification range. However, if its content is too large, it may volatilize during melting and cause composition fluctuations, or it may adversely affect vitrification. Therefore, the content of fluorine _{(F 2} equivalent) 0-10%, 0-7%, particularly preferably 0 to 5%.

Sb ₂ O ₃ can be added as a reducing agent. However, the content is preferably 0.1% or less in order to avoid coloring or in consideration of environmental load.

  The magnetic glass lens of the present invention exhibits good light transmittance in the wavelength range of 400 to 1100 nm. Specifically, the transmittance at an optical path length of 1 mm at a wavelength of 633 nm is preferably 60% or more, 65% or more, 70% or more, 75% or more, and particularly preferably 80% or more. Further, the transmittance at an optical path length of 1 mm at a wavelength of 532 nm is preferably 30% or more, 50% or more, 60% or more, 70% or more, and particularly preferably 80% or more. Furthermore, the transmittance at an optical path length of 1 mm at a wavelength of 1064 nm is preferably 60% or more, 70% or more, 75% or more, and particularly preferably 80% or more.

  The magnetic glass lens of the present invention preferably has a refractive index (nd) of 1.75 or more, 1.80 or more, 1.83 or more, particularly 1.85 or more. If the refractive index is too low, the focal length increases, making it difficult to reduce the size of digital cameras, camera-equipped mobile phone models, and the like.

  Next, the manufacturing method of the magnetic glass lens of this invention is demonstrated. The magnetic glass lens of the present invention includes, for example, a step of obtaining a precursor glass by melting a glass raw material and cooling and solidifying the obtained molten glass, and heat-treating the precursor glass in an inert atmosphere or a reducing atmosphere. It can be manufactured by a step of obtaining a preform and a step of heat-molding a glass preform.

The precursor glass may be produced by a normal melting method using a melting vessel. However, when the Tb ₂ O ₃ content is particularly high, vitrification is difficult with this method, and thus the precursor glass is produced by a containerless floating method. It is preferable to do. FIG. 1 is a schematic cross-sectional view showing an example of a production apparatus for producing precursor glass by a containerless floating method. Hereinafter, the manufacturing method of precursor glass is demonstrated, referring FIG.

The precursor glass manufacturing apparatus 1 includes a mold 10. The mold 10 also serves as a melting container. The molding die 10 has a molding surface 10a and a plurality of gas ejection holes 10b opened in the molding surface 10a. The gas ejection hole 10b is connected to a gas supply mechanism 11 such as a gas cylinder. Gas is supplied from the gas supply mechanism 11 to the molding surface 10a via the gas ejection hole 10b. The type of gas is not particularly limited, inert gas such as nitrogen, argon, helium, carbon dioxide; reducing gas such as carbon monoxide and hydrogen; oxidizing gas such as oxygen and air, alone or in combination Can be used in combination. Among them, it is preferable to use an inert gas in order to increase the ratio of Tb ^{3+ in} the total Tb and from the viewpoint of safety.

  When manufacturing precursor glass using the manufacturing apparatus 1, first, the glass raw material lump 12 is arrange | positioned on the shaping | molding surface 10a. As the glass raw material block 12, for example, a raw material powder integrated by press molding or the like, a sintered body obtained by integrating raw material powder by press molding or the like, and a composition equivalent to the target glass composition are used. For example, an aggregate of crystals.

Next, the glass raw material block 12 is floated on the molding surface 10a by ejecting gas from the gas ejection holes 10b. That is, the glass raw material block 12 is held in a state where it is not in contact with the molding surface 10a. In this state, the glass material block 12 is irradiated with laser light from the laser light irradiation device 13. In the state where the glass raw material mass 12 is in contact with the molding surface 10a, the laser light irradiation device 13 irradiates the glass raw material material 12 with laser light, and then the glass raw material material 12 is melted or simultaneously with the completion of the melting, The glass raw material block 12 may be floated on the molding surface 10a. In this way, the glass raw material mass 12 is heated and melted to be vitrified to obtain molten glass. The gas flow rate may be appropriately set depending on, for example, the mass and volume of the glass raw material lump 12, the shape size of the gas ejection hole 10b, etc., for example, 0.5 to 30 L / min, 5 to 25 L / min, particularly 10 to 10. 20 L / min is preferable. If the gas flow rate is too small, it tends to be difficult to float the glass raw material block 12. On the other hand, if the gas flow rate is too high, the floating state of the glass raw material block 12 becomes unstable, and problems such as contact with the molding surface 10a and popping out of the molding surface 10a are likely to occur. When an inert gas or a reducing gas is used, the glass raw material lump 12 becomes less likely to be oxidized or more easily reduced as the gas flow rate is increased, so that the ratio of Tb ^{3+ in} the total Tb can be increased. In addition to the method of irradiating with laser light, the method of heating and melting may be radiant heating.

  Then, precursor glass can be obtained by cooling molten glass. In the step of heating and melting the glass raw material lump 12 and the step of cooling until the temperature of the molten glass and further the precursor glass becomes at least the softening point or less, at least gas ejection is continued, It is preferable to suppress contact between the molten glass, and further, the precursor glass and the molding surface 10a.

Furthermore, a glass preform is obtained by heat-treating the obtained precursor glass in an inert atmosphere or a reducing atmosphere. Examples of the inert gas used include nitrogen, argon, helium, and carbon dioxide, and examples of the reducing gas include carbon monoxide and hydrogen. Note that the reducing atmosphere is preferably an atmosphere using a mixed gas of a reducing gas and an inert gas in consideration of safety. From the viewpoint of effectively increasing the ratio of Tb ^{3+ in} the total Tb, a reducing atmosphere is preferable, and from the viewpoint of safety, a mixed gas atmosphere of hydrogen and an inert gas is particularly preferable.

The heat treatment temperature is preferably (glass transition point−50 ° C.) or more, particularly (glass transition point−30 ° C.) or more of the precursor glass. When the heat treatment temperature is too low, it is difficult to obtain the effect of increasing the ratio of Tb ^{3+ in} the total Tb. On the other hand, if the heat treatment temperature is too high, devitrification is likely to occur, so (glass transition point + 100 ° C.) or less, (glass transition point + 80 ° C.) or less, (glass transition point + 50 ° C.) or less, particularly (glass transition point + 30 ° C.). It is preferable that

The heat treatment time is preferably 0.5 hours or longer, particularly 1 hour or longer. If the heat treatment time is too short, it is difficult to obtain the effect of increasing the ratio of Tb ^{3+ in} the total Tb. On the other hand, the upper limit of the heat treatment time is not particularly limited, but if it is too long, further effects cannot be obtained, leading to energy loss. Therefore, it is preferably 100 hours or less, 50 hours or less, particularly 10 hours.

Subsequently, the glass preform is put into a precision-worked mold, and pressure molding is performed while heating until a softened state is obtained, thereby transferring the surface shape of the mold (mold press molding). The atmosphere during pressure molding is preferably an inert atmosphere or a reducing atmosphere. Examples of the inert gas used include nitrogen, argon, helium, and carbon dioxide, and examples of the reducing gas include carbon monoxide and hydrogen. Note that the reducing atmosphere is preferably an atmosphere using a mixed gas of a reducing gas and an inert gas in consideration of safety. From the viewpoint of effectively increasing the ratio of Tb ^{3+ in} the total Tb, a reducing atmosphere is preferable, and from the viewpoint of safety, a mixed gas atmosphere of hydrogen and an inert gas is particularly preferable. In this way, a magnetic glass lens can be obtained. A magnetic glass lens may be produced by subjecting the glass preform to machining such as cutting or polishing.

  EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to these Examples.

Table 1 shows examples and comparative examples of the present invention.

First, the raw material prepared so that it might become the glass composition shown in Table 1 was press-molded, and the glass raw material lump was produced by sintering at 1000-1400 degreeC for 6 hours. Next, the glass raw material lump was coarsely pulverized in a mortar to obtain small pieces of 0.05 to 1.0 g. Precursor glass (diameter: about 1 to 8 mm) was produced by a containerless floating method using an apparatus according to FIG. 1 using the obtained pieces of glass raw material lump. The type and flow rate of the gas for suspending the glass raw material lump were as shown in Table 1, and a 100 W CO ₂ laser oscillator was used as the heat source.

The obtained precursor glass was heat-treated at the atmosphere and temperature shown in Table 1 for 3 hours to obtain a glass preform, and then the glass preform was molded and press-molded to obtain a magnetic glass lens. In Table _"H 2 / _{N 2"} are by _volume%, H 2 _4%, indicating a mixed gas atmosphere of N 2 96%.

For the obtained magnetic glass lens, the ratio of Tb ^{3+ to} the total Tb, light transmittance, magnetic susceptibility, and refractive index were measured as follows.

  The light transmittance was measured using a spectrophotometer (UV-3100 manufactured by Shimadzu Corporation). Specifically, the obtained magnetic glass lens was polished so as to have a thickness of 1 mm, and from the light transmittance curve obtained by measuring the transmittance at a wavelength of 300 to 1400 nm, at each wavelength described in the table. The light transmittance was read. The light transmittance is an external transmittance including reflection.

The ratio of Tb ^{3+ to} the total Tb was measured using an X-ray photoelectron spectrometer (XPS). Specifically, for the obtained magnetic glass lens, the ratio of Tb ³⁺ to the total Tb was calculated from the peak intensity ratio of each Tb ion measured using an X-ray photoelectron spectrometer.

  The magnetic susceptibility was measured using a SQUID magnetometer (Magnet Property Measurement System manufactured by Quantum Design) under the conditions of a measurement temperature of 300K and an applied magnetic field of -1T to 1T.

  The refractive index is indicated by a measured value with respect to d-line (587.6 nm) of a helium lamp.

As is apparent from Table 1, No. 1 as an example. In the magnetic glass lenses 1 to 6, the ratio of Tb ^{3+ to} the total Tb was as high as 65% or more, and the light transmittance at each wavelength was excellent. Moreover, the magnetic susceptibility was also good. On the other hand, No. which is a comparative example. In the magnetic glass lens of No. 7, the ratio of Tb ^{3+ to} the total Tb was as low as 54%, and the light transmittance at each wavelength was inferior to that of the magnetic glass lens of the example.

1: Precursor glass manufacturing apparatus 10: Mold 10a: Molding surface 10b: Gas ejection hole 11: Gas supply mechanism 12: Glass raw material block 13: Laser beam irradiation apparatus

Claims (3)

A magnetic glass lens characterized by containing more than 40% of Tb ₂ O ₃ in terms of oxide of mol%, and the ratio of Tb ³⁺ to the total Tb is 55% or more in mol%.   2. The magnetic glass lens according to claim 1, wherein a light transmittance at an optical path length of 1 mm at a wavelength of 633 nm is 60% or more. Furthermore, in _{mol%, SiO 2 0~50%, B} 2 O 3 0~50%, magnetic glass lens according to claim 1 or 2, characterized in that it contains _Al 2 O 3 _0~50%.