KR100695647B1 - Process for producing preform for optical element-molding, optical element and process for producing same - Google Patents

Abstract

In the manufacturing method of the preform for optical element shaping | molding which isolate | separates a fixed mass of molten glass lump from the molten glass which flows out from the outlet of an outflow pipe, applies a wind pressure to the glass lump, and forms it into a glass preform while raising it, The downward direction of an outflow pipe The step of receiving and supporting the tip of the molten glass flow by the molten glass support disposed on the substrate, removing the support by the molten glass support and separating the molten glass mass from the tip of the molten glass flow in a closed space filled with dry gas. It is an optical element formed by precision press molding the manufacturing method of the preform for optical element shaping | molding, etc. which are performed by this method and the preform produced by the said method.

Description

Method for manufacturing preform for optical element molding, optical element and method for manufacturing same {PROCESS FOR PRODUCING PREFORM FOR OPTICAL ELEMENT-MOLDING, OPTICAL ELEMENT AND PROCESS FOR PRODUCING SAME}

1 is a manufacturing process chart showing an example of a method of manufacturing a preform for molding an optical element of the present invention.

It is explanatory drawing which shows the other example of the shape of the partition member which receives a molten glass flow.

3 is a manufacturing process chart showing another example of the manufacturing method of the preform for molding an optical element of the present invention.

4 is a manufacturing process diagram showing still another example of the manufacturing method of the preform for molding an optical element of the present invention.

Explanation of symbols on the main parts of the drawings

1: forming mold 2: outflow pipe

3a: partition member 4: molten glass

4a: molten glass chunk 5: glass cover

6: dry gas atmosphere 7: water channel

8: teflon skirt 9: injured gas

The present invention relates to a manufacturing method of an optical element molding preform, an optical element, and a manufacturing method thereof. More specifically, the present invention relates to a method for efficiently producing a high quality glass preform for optical element molding, an optical element obtained by precision press molding these preforms, and a method for producing the same.

In various optical systems including an imaging optical system, a lens made of low dispersion glass is required. Fluorine is generally introduced into such a low dispersion optical glass for the purpose of reducing the dispersion.

In recent years, with the miniaturization, high pixel size, and high performance of digital still cameras and digital video cameras, there is an increasing demand for lenses including aspherical lenses made of low dispersion glass. In order to meet this demand, the method of grinding and polishing the shape of optical functional surfaces such as the lens surface cannot be completed in time, and the glass called preform is heated and softened and pressed in a press-forming mold, and the optical function A method for mass production under high productivity is effective by a precision press molding method (also called a mold optics molding method) for molding a surface (see, for example, Japanese Patent No. 3153871).

When a lens made of a low dispersion glass containing fluorine is made by the precision press molding method, a glass molded body called a preform is first made. The preform is required to have the same mass as that of the intended precision press-formed product, and to be free from defects such as devitrification, stria, and scratches on the inside and the surface.

The following two methods are considered for the preparation of the preform. One is a method of shaping a glass block, cutting out parts without defects such as stria, and chamfering or optically polishing the surface to form a preform. In this method, since the surface of each one of the preforms is optically polished, it takes a lot of time and effort, and hence the cost is increased. Moreover, there also exists a problem that the mass of glass must also be strictly controlled with progress of grinding and polishing.

Another method is a method of separating a molten glass mass having the same mass as the target preform from the molten glass and molding the molten glass mass into a preform in the process of cooling the molten glass mass, which is called a hot forming method. In the hot forming method, since the preform can be made directly from the molten glass, productivity can be improved. Moreover, molten glass lump can be isolate | separated with high mass precision by dropping a molten glass from an outflow nozzle, or supporting the front-end | tip of the molten glass falling down from an outflow nozzle, and removing the said support at predetermined timing. .

In addition, in order to prevent the glass lump surface from touching the other objects as much as possible during molding, the preform having a very smooth surface can be made by forming the glass in a floating state by applying wind pressure.

Although the hot forming method is very excellent as a manufacturing method of the preform in this way, it has been difficult to apply it to glass containing high volatile components, such as fluorine.

For example, the glass having high demand for ultra low dispersion characteristics is obtained by containing fluorine in the glass structure, but in the glass at a very high temperature in a molten state, the fluorine component near the surface is reduced by volatilization, so that The quality is significantly degraded. For this reason, while it is a method which can manufacture a preform with high productivity, it is a fact that it is not practical to make glass with high high temperature reactivity, such as a fluorine-containing glass, by the hot forming method into a preform.

Although there is a difference in the mechanism of volatilization, there is a problem of volatilization even when hot preforming the preform using glass containing a bivolatile component such as boron.

Under these circumstances, a first object of the present invention is to provide a method for efficiently manufacturing a high quality glass preform for optical element molding, and a second object is an optical element obtained by precision press molding the preform, and its It is to provide a manufacturing method.

Disclosure of the Invention

MEANS TO SOLVE THE PROBLEM This inventor earnestly researched about the possibility of hot forming of the preform for optical element shaping | molding using the glass which shows high reactivity and volatility in a molten state, such as a fluorine-containing glass and a boron-containing glass. In this process, the preform was hot-molded from the phosphate glass, and the surface thereof was examined in detail. When the preform, which was considered to be well formed at first glance, was observed under a microscope, it was observed that fine irregularities were continuous in the shape of scales.

Moreover, when this preform was precisely press-molded and the lens was produced, the surface of the lens caused blur (scattering), which was unsuitable for the optical element.

After the molding, fine irregularities were eliminated in the lens, but since the fine irregularities on the surface of the preform consisted of a layer having a shaken refractive index, it was found that the lens remained as scattered after the molding.

The fine unevenness of the surface of the preform is considered to occur because fluorine in the glass at high temperature is volatilized from the molten glass surface during cooling. High-reaction components such as fluorine contained in the molten glass react with moisture in the atmosphere to form HF and release from the glass surface, so that the composition of the glass surface is changed, resulting in a deteriorated layer on the glass surface, When the highly reactive component of deviates from the glass, fine scale irregularities and refractive indexes, as described above, may cause a layer shaken in a scale shape. Therefore, in order to prevent surface deterioration and unevenness, the glass immediately after the outflow should not be in contact with the atmosphere containing abundant moisture as much as possible, and furthermore, as an airtight space for the purpose of suppressing volatilization, to increase the internal pressure of the atmosphere. It is preferable.

In addition, even if the evaporation of the volatile component in the glass is prevented, if the glass is molded in a state of being in contact with the mold, traces of contact with the mold remain on the preform surface.

Therefore, in order to hot-form highly reactive glass at high temperature, such as fluorine-containing glass, and to make a high quality preform,

(i) Glass at high temperatures should be handled in an enclosed space filled with a dry atmosphere.

(ii) In the case of a relatively large mass in which the glass is hard to naturally cool, the spilled molten glass is brought into contact with an object which takes heat away from the glass, cooled, and then started to be formed into a preform. The shaping of the preform is carried out while applying the wind pressure to the glass in order to avoid contact with other objects as much as possible.

(iii) In the case of a relatively small mass of molten glass dripping from the outlet pipe, the molten glass mass is cooled down to a temperature at which the volatile component does not evaporate in the course of dripping the molten glass mass, and then the preform molding is started while rising by applying a wind pressure. Can be.

(iv) When floating gas for floating molding is injected into the outlet of the outflow pipe, the outlet is blocked from the floating gas because it causes the mass change of the preform, stria, devitrification and the like.

(v) It is preferable to restrict the movement path to a vertical direction from separation from molten glass to the start of floating so that a molten glass mass may not be bent.

As a result of consideration as mentioned above, it discovered that the preform for optical element shaping | molding of the optical glass which does not have the fine unevenness | corrugation on the surface, and is also excellent in internal quality can be stably produced.

This invention is completed according to this knowledge.

That is, the present invention,

(1) In the manufacturing method of the optical element shaping preform which isolate | separates a fixed mass of molten glass lump from the molten glass which flows out from the outlet of an outflow pipe, applies a wind pressure to the glass lump, and forms it into a glass preform, making it float.

The process of receiving and supporting the front end of a molten glass flow by the molten glass support body arrange | positioned under an outflow pipe, removing the support by the said molten glass support body, and separating the said molten glass mass from the front end of a molten glass flow as a dry gas. Method for producing a preform for forming an optical element, characterized in that carried out in a closed space filled

(2) A method for producing an optical element shaping preform, in which a molten glass drop is dropped from an outflow pipe, received into a mold for ejecting gas, and formed into a glass preform while being raised by applying wind pressure by the gas.

The dropping of the molten glass droplets is carried out in a sealed space filled with dry gas, and a shielding body is formed to cross the dropping path of the molten glass droplets to shield the outflow pipe from the gas ejected from the mold, and further melt A method of manufacturing a preform for forming an optical element, wherein the shield is removed from the dropping path in synchronization with dropping of glass;

(3) A method for producing an optical element shaping preform, in which a molten glass drop is dropped from an outflow pipe, received into a mold for ejecting a gas, and formed into a glass preform while being raised by applying wind pressure by the gas.

The dropping of the molten glass droplets is carried out in a closed space filled with dry gas, and a shielding body is formed to cross the dropping path of the molten glass droplets to shield the outflow pipe from the gas ejected from the mold. A method for manufacturing a preform for forming an optical element, comprising: dropping molten glass droplets on a shield, and removing the shield from the dropping path in synchronization with the dropping of the molten glass droplets;

(4) The method for producing an optical element molding preform according to any one of (1) to (3), wherein the gas for applying wind pressure is a dry gas;

(5) Optical element molding which separates a certain mass of molten glass mass from the molten glass which flows out from the outlet of the outflow pipe, receives it into a molding frame which ejects a gas for applying wind pressure to the glass mass, and floats it into a glass preform. In the manufacturing method of the preform for

A cover having an opening that can be opened and closed vertically downward of the outlet, covering the space including the outlet, closing the opening when the opening is closed, and supplying a dry gas into the space to close the opening. A method of manufacturing a preform for forming an optical element, wherein the glass mass is separated into a molten glass furnace, and the glass mass is transferred to a molding mold which opens the opening to eject a dry gas disposed in proximity to the opening.

(6) The method for producing an optical element molding preform according to any one of (1) to (5), wherein the preform made of glass containing fluorine is molded;

(7) The manufacturing method of the optical element shaping preform as described in any one of said (1)-(6) which shape | molds the preform which consists of glass containing Bi,

(8) Optical element molding which separates a certain mass of molten glass mass from the molten glass which flows out from the outlet of the outflow pipe, receives it into a molding frame which blows out the gas for applying wind pressure to the glass mass, and forms a glass preform while floating. In the manufacturing method of the preform for

A gas ejected from the mold is a dry gas, and the glass is a fluorine-containing glass;

(9) An optical element, which is formed by heating and precision-preforming an optical element molding preform manufactured by the method according to any one of (1) to (8).

(10) A method for manufacturing an optical element, wherein the preform for molding an optical element manufactured by the method according to any one of (1) to (8) is heated, and precision press molding using a press molding die. ,

(11) In the method for manufacturing an optical element according to (10), the optical element forming preform is introduced into a press forming mold, and the preform and the press forming mold are heated together to precisely press mold the optical element. Manufacturing method, and

(12) The optical element according to the above (10), wherein the preform for forming the optical element and the press forming mold are heated separately, and then the preform is introduced into the press forming mold to precise press molding. It is to provide a manufacturing method.

According to the manufacturing method of the optical element shaping | molding preform of this invention, even the molten glass containing the component which has bivolatile and high reactivity, such as fluorine-containing glass, can manufacture the preform of high quality and high mass precision directly.

Moreover, according to the preform for optical element shaping | molding of this invention, it is possible to provide the optical element made from glass of high quality on both a surface and an inside by precision press molding.

Further, according to the optical element of the present invention, it is possible to provide an optical element made of fluoric acid glass having excellent surface and internal quality, which does not require grinding or polishing at all for shape processing of the optical functional surface.

Further, according to the method for manufacturing the optical element of the present invention, it is possible to provide a method for producing an optical element made of fluorinated glass having excellent surface and internal quality, which does not require grinding or polishing at all for the shape processing of the optical functional surface.

Best Mode for Carrying Out the Invention

First, the manufacturing method of the preform for optical element shaping | molding is demonstrated in detail.

[Manufacturing method of preform for molding optical element]

In the present invention, the precision press molding refers to a press molding method in which an optical functional surface having an optical function of refracting, reflecting, diffraction, or transmitting light is formed by press molding, and in general, mold optics It is called molding or mold press molding. In this precision press molding, the shape of an optical functional surface (for example, a lens surface such as an aspherical surface of an aspherical lens, a surface in which diffraction gratings are formed with fine irregularities, etc.) is determined by press molding. Therefore, the optical functional surface is ground by grinding or polishing. Need not be machined to design shape. Moreover, in the precision press molding, the glass molded object adjusted similarly to the mass of a press molded article is heated, and it presses with a press molding frame at the temperature which can deform | transform by pressurization. Although this glass molded object is called the preform for optical element shaping | molding, it may just be called a preform hereafter.

As described above, only the preform having high mass precision and good internal quality and surface condition without striae, devitrification, scratches, cracks, or the like is used.

(About a preform manufacturing method 1)

The 1st method of the manufacturing method of a preform (henceforth a preform manufacturing method 1) isolate | separates a fixed mass of molten glass mass from the molten glass which flows out from the outlet of an outflow pipe, applies a wind pressure to the glass mass, and is made of glass, making it float In the manufacturing method of the preform for optical element shaping | molding to a preform, the molten-glass support is supported by the molten-glass support body arrange | positioned below an outflow pipe, removes the support by the said molten-glass support body, and melts a glass flow. The step of separating the molten glass lump at the tip of is characterized in that it is carried out in a sealed space filled with dry gas.

Highly reactive components such as fluorine contained in the molten glass react with moisture in the atmosphere to form HF and release from the glass surface, resulting in a change in the composition of the glass surface, resulting in a deteriorated layer on the surface, or a highly reactive component. When separated from this glass, fine scale irregularities as described above may be generated. For this reason, in the preform manufacturing method 1, the glass immediately after outflow is handled in the sealed space filled with dry gas.

As a manufacturing method of a dry gas, the method of passing water in a desiccant, for example, removing the water in a gas, or evaporating a liquefied gas is mentioned. As an example of a liquefied gas, liquid nitrogen and a liquid carbon dioxide gas can be shown as a preferable example. In addition, liquid carbonic acid gas liquefies carbonic acid gas under high pressure.

As dry gas, it is preferable that water content is 400 ppm or less, and it is more preferable that it is 380 ppm or less. There is no restriction | limiting in particular in the minimum of the moisture content of dry gas, Although it is ideally 0 ppm, the moisture content of the dry gas which can be obtained in large quantities is 100 ppm or more. Moreover, it is also preferable to use the gas whose dew point is -30 degrees C or less as dry gas. Although there is no restriction | limiting in particular in the minimum of dew point of dry gas, The minimum of the dew point of the gas which can be obtained in large quantities is about -80 degreeC. Moreover, high pressure gas can also be used as dry gas. For example, when using a high pressure helium gas and a high pressure argon gas, what is necessary is just to specify the grade whose dew point is -60 degreeC, and the ultra high purity grade (dew point -80 degreeC). Therefore, gas can also be used as a dry gas from these high pressure gas. However, since the dew point may rise depending on the storage condition of a container, it is preferable to use the gas from the high pressure gas container fully managed. In addition, even if the water content or dew point does not fall within the above range, a gas filled with a desiccant such as synthetic zeolite may be used as the drying gas.

Examples of the gas include nitrogen gas, inert gas (for example, argon gas, helium gas, etc.), carbon dioxide gas or a gas containing the gas, and a mixture of any one of the above gases and oxygen, such as a mixed gas of nitrogen and oxygen. Gas, air, etc. can be illustrated.

In the manufacturing method 1 of a preform, a clarified and homogenized molten glass is prepared, and molten glass is continuously dropped at the constant outflow velocity from the outflow pipe, such as a temperature-controlled platinum alloy agent. And it receives and supports the front-end | tip of the molten-glass flow which flows down from the upper surface of the molten-glass support body waiting below the outflow pipe. That is, the said support is performed in the state which the front-end | tip of a molten glass flow and a molten glass support body contacted.

The molten glass support body is composed of a plurality of dividing members, and each dividing member has a function of being spaced apart or in close contact with each other. When receiving the front end of a molten glass flow, each division member is closely contacted with each other, and the front end of a molten glass flow is supported by the boundary part of a division member. In this state, the support and the front end of the molten glass flow directly contact each other. Thus, even if the glass has a low viscosity at the time of outflow, the viscosity of the front end of the molten glass flow is increased and does not penetrate between the partition members. Moreover, since the viscosity of a molten glass lump rises by the contact with a partition member, it becomes possible to effectively prevent the bending of the glass which is easy to generate | occur | produce when moving a molten glass lump to the shaping | molding die demonstrated below. In addition, volatilization of volatile components such as fluorine may be reduced from the surface due to the increase in viscosity (decrease in temperature) of the molten glass mass. It is preferable to cool a partition member, in order to prevent fusion with a molten glass, and to make it easy to acquire the said effect. As a cooling method, the method of water-cooling a partition member, the method of air-cooling a partition member, the method of raising the emissivity by making the partition member surface black, the combination of the said methods, etc. can be illustrated. When the partition member is cooled by water or air cooled, a flow path may be formed inside the partition member, and cooling water or cooling gas may flow therein. Moreover, as a molten glass support body, heat resistant metal, carbon, ceramics, etc. can be illustrated. Among them, heat resistant stainless steel is preferred in consideration of heat resistance and thermal conductivity.

After receiving and supporting the tip of the molten glass flow, the support by the molten glass support body is removed at a timing at which a predetermined amount of the molten glass mass is obtained, and the molten glass mass is separated. As a specific method of removing the support by a molten glass support body, there exists a method of falling a molten glass support body, and the method of moving a molten glass support body in a horizontal direction.

In the method of dropping a molten glass support body, it is preferable to drop a molten glass support body perpendicularly downward. When the molten glass support is lowered vertically downward, a necking is formed between the front end of the molten glass flow and the outflow pipe side, and the necking becomes larger as the lowering continues, and the front end is separated, so that a predetermined amount of molten glass agglomerates on the molten glass support. Is obtained.

When descending a molten glass support body, what is necessary is just to select the distance and speed | rate of the fall | disconnection in which a glass flow is cut naturally.

In order to make the amount of molten glass mass constant, the position of receiving the tip of the molten glass flow and the falling conditions of the molten glass support are made constant, and the period of the falling is made constant.

In the method of moving a molten glass support body horizontally, it is preferable to move a molten glass support body horizontally instantaneously. In this method, separation of a glass gob and falling of the glass gob shown below can be performed simultaneously.

Also in this method, in order to make the quantity of a molten glass mass constant, the position which receives the tip of a molten glass flow, and the period of descent are also made constant.

Next, the division members are separated from each other, and the molten glass mass is dropped vertically between the separation members that are separated from each other. Before the separation of the molten glass flow is completed, the division member may be separated to drop the molten glass mass. Further, as described above, the glass member may be cut by opening the partition member at regular time intervals without lowering the partition member, and the molten glass lump may be formed by combining the drop of the partition member and the spacing of the partition member at constant time intervals. You may separate.

Although the number of the partition members may be any number, it is preferable to comprise a molten glass support body with two partition members from a viewpoint of ensuring the said series of operation reliably and easily. In that case, it is preferable to make a boundary of a partition member in a state in which the partition member is in close contact is a straight line for bringing both members into close contact. In addition, the upper surfaces of the two dividing members are planar, and the two upper surfaces are symmetrical with respect to an imaginary plane passing through the boundary between the two dividing members at an angle of 90 degrees to 180 degrees. It is preferable. In addition, in the state where the partition members are in close contact with each other, a concave section for collecting molten glass may be formed on the joining surface of the partition member, and a cover having a hole in the center may be provided to increase the sealing property in the container when the partition member is opened. You may mount on a partition member. By using such a molten glass support body, the front-end | tip of a molten glass flow can be stably supported, and when molten glass is separated, a molten glass lump can fall vertically downward.

In addition, before the dropping, the molten glass support may be lowered vertically at a speed smaller than the flow rate of the molten glass flow. By such an operation, the tip of the outflow pipe can be buried in the molten glass pool to prevent occurrence of striae.

A mold is waiting below a molten glass support body, and the falling molten glass mass is received. The molten glass flows out from the outflow pipe and follows the path along the vertical direction all the time until it falls to the mold. For this reason, the horizontal direction component of the external force which acts on a molten glass flow and a molten glass lump can be minimized, and defects, such as a bending in a glass molded object, can be prevented.

The gas outlet is formed in the bottom part of the mold which receives a molten glass lump, and shape | molds it into a glass molded object, from which the upward wind pressure is applied to the glass on a mold (collecting molten glass lump and glass molded body collectively), and to raise it. The gas is blown out and molded while floating the glass. In addition, when the gas (hereinafter referred to as floating gas) is injected into the outflow pipe, the temperature of the pipe or falling molten glass flow is lowered or the flow of the molten glass flow is unstable, so that after the molten glass mass is dropped, It is desirable to close the floating gas in close contact with the splitting members immediately.

Moreover, it is preferable to use dry gas also as a floating gas. In that case, it is preferable to use the gas of the same kind as the dry gas which fills the said airtight space.

In addition, the gas ejection opening may be one in which a plurality of pores are selectively opened, the recess of the molding die may be formed of a porous material, and gas may be ejected from the entire recess, or one of the pores may be used. The method of ejecting gas from a plurality of selectively opened pores and the method of ejecting gas from the porous whole surface have a rotationally symmetric axis with one rotationally symmetric axis because upward wind pressure is applied to the molten glass mass over a wide range. It is suitable for the case where glass is shape | molded to the rotating body in which the outline in the cross section containing this becomes convex outward. Moreover, it is preferable to arrange | position a some pore so that it may become symmetrical with respect to the center of a recessed part in the recessed part of a shaping | molding die.

Moreover, it can shape | mold while rotating glass in the recessed part of a shaping | molding die by forming one pore in the center of the recessed part of a shaping | molding die, and blowing a gas. This method is suitable for molding a spherical glass molded body.

As a material of a molding die, heat resistant metals, such as stainless steel, carbon etc. can be used. In addition, although the molten glass lump transferred to the shaping | molding die is made lower temperature than the outflow, it is still high temperature and there exists a possibility of fusion | melting. Therefore, it is preferable to control the temperature of a shaping | molding die to 300 degrees C or less, and to prevent fusion reliably. In order to prevent fusion, it is preferable to form a film such as a carbon film such as diamond on the surface of the mold.

When supporting the molten glass mass with the molten glass support, direct contact of the support with the glass mass is preferred to promote cooling of the glass mass. In that case, in order to prevent fusion | melting, it is preferable to form a film | membrane, such as a carbon film, such as a diamond, in the surface which contacts the molten glass of a molten glass support body, and the surface which contacts the molten glass lump of a shaping | molding die. Moreover, it is preferable to mirror-finished the said surface. When the molten glass support is separated and the molten glass lump is dropped, when the fusion of the glass occurs on the divided member surface or the slippage of the molten glass is poor, the horizontal component of the external force acting on the molten glass lump becomes large and the glass molded body The risk of defects, such as bending, increases. Therefore, it is particularly preferable to coat carbon, such as diamond, on the partition member surface, to cool the partition member, and to polish the partition member surface for the purpose of preventing fusion and improving slippage.

In addition, in order to prevent the bending of glass more reliably, it is preferable to drop a molten glass lump to the center of a shaping | molding die, The said means becomes a point.

In order to receive the molten glass lump which isolate | separates and falls one by one, a some shaping | molding die is conveyed sequentially below the molten glass support body. Specifically, a plurality of forming molds may be arranged on the turntable at equal intervals so that the empty forming mold waits when the molten glass lump falls. In this way, a molten glass lump is distributed to the plurality of molding dies to form a glass molded body.

The molded glass molded body is cooled on a mold to a temperature not deformed by external force, and then taken out and slow cooled.

Here, FIG. 1 is a manufacturing process drawing which shows an example of the preform manufacturing method 1, and in order to perform the process of isolate | separating the said molten glass mass in the closed space filled with dry gas, as shown in FIG. The space formed by the front-end | tip and the molten-glass support body 3a (dividing member in a figure) is filled with dry gas. Although all the molding dies 1 for forming the preform are put in a sealed container and filled with the drying gas therein, the method is preferable even if the drying gas is poured into the space for forming the glass of the molding die 1. have. In order to make the said sealed space minimum, it covers with the cover 5 (glass cover in drawing) so that the front-end | tip of the outflow pipe 2 and the part which mounts the molten glass lump 4a of the molten glass support body 3a are mounted. A sealed space is formed by the cover 5 and the molten glass support 3a in a state where the divided members constituting the molten glass support 3a are in close contact with each other. When the inside of this sealed space is filled with the dry gas 6, since the separation of the molten glass mass 4a is performed in the state which the said partition member 3a was in close contact with each other, the temperature of glass is high and its reactivity with outdoor air is high. Separation process of the molten glass lump of can be performed in a closed space filled with a dry gas.

FIG. 2: is explanatory drawing which shows the other example of the shape of the division member which receives a molten glass flow, In FIG. 2, the molten glass support body 3b is comprised by two division members, and the surface which receives the molten glass 4 is inclined I'm making it. And at the timing which can isolate | separate predetermined amount of molten glass lumps 4a, without separating the division member 3b, it isolate | separates mutually and releases support of a molten glass lower end part, and isolate | separates molten glass lump 4a. Then, it falls naturally in the center of the shaping | molding die 1.

As said cover 5, a transparent container, for example, a glass container is preferable. By making the cover 5 transparent, the outflow state can be observed from the outside. In addition, in FIG. 1 and FIG. 2, in order to improve the sealing property in the glass cover 5, between the glass cover 5 and the partition members 3a, 3b with the skirt 8 comprised from elastic material, such as Teflon, The gap is not formed between the glass cover 5 and the partition members 3a and 3b even when the partition members are dropped or spaced apart from each other. In this way, by reducing the gap, the internal pressure in the cover can be made higher than the external air pressure, and the atmosphere is difficult to enter the cover.

Moreover, the molten glass may get wet at the outer periphery of the tip of an outflow pipe. In this case, in order to suppress the wet, it is preferable that the wetted glass is also included in the sealed space.

Next, the temperature of the dry gas supplied in the sealed space is demonstrated. When supplying dry gas to the position away from an outflow pipe, or when a heat resistant cover is attached to an outflow pipe, the temperature of dry gas may be about room temperature without a restriction | limiting in particular. In the case of supplying the gas in the vicinity of the outflow pipe, in order to prevent volatile matter from adhering to the pipe, it is preferable to set the temperature of the gas to be equal to or higher than the softening temperature of the glass to be molded, and more preferably to the outflow glass temperature. .

As shown in FIG. 1, after the partition member which comprises the molten glass support body 3a is separated, the molten glass mass 4a falls vertically downward, and introduce | transduced into the center of the shaping | molding die 1, and the said partition member immediately Close to each other. Therefore, the space covered by the cover 5 is also excluded except when the molten glass lump is dropped even in a structure in which the tip of the outflow pipe 2 and the upper portion of the molten glass support 3a are sealed using the cover 5. It can be kept closed. In addition, since the dry gas flows out from inside the cover even when the partition member is separated, the floating gas 9 hardly flows into the space covered by the cover 5. In addition, even if the floating gas flows in, the gas is also a dry gas, so that the inside of the sealed space can be filled with the dry gas.

As mentioned above, according to the preform manufacturing method 1, since the molten glass immediately after the outflow which has high reactivity with air is handled in the closed space filled with dry gas, the preform which is smooth in a surface and does not have a defect can be shape | molded. In addition, the molten glass lump is brought into direct contact with the molten glass support in the sealed space to take away the heat of the glass, and the glass surface to a temperature range where high reactivity components such as fluorine and the like are not easily volatilized before being introduced into the mold. Can be cooled. Therefore, the glass which melt | dissolved in the state in which the whole surface was solidified was formed, and it is possible to manufacture a smooth preform even if seen microscopically, without the microscopic unevenness of scale shape.

Moreover, it can shape | mold while rotating glass in the recessed part of a shaping | molding die by forming one pore in the center of the recessed part of a shaping | molding die, and blowing a gas. This method is suitable for molding a spherical glass molded body.

Moreover, the preform manufacturing method 1 is suitable when manufacturing a comparatively large mass of preform. The preferable range of the preform mass is 200 mg to 10 g. In addition, the mass precision is preferably within ± 2%, more preferably within ± 1%.

(About preform manufacturing method 2)

The second method (hereinafter referred to as preform manufacturing method 2) of the manufacturing method of the preform is formed into a glass preform while dropping molten glass droplets from the outflow pipe, receiving the gas into a molding mold and applying a wind pressure with the gas to float. In the method of manufacturing a preform for forming an optical element, the dropping of the molten glass droplets is carried out in a closed space filled with dry gas, and a shielding body is formed so as to cross the dropping path of the molten glass droplets so that the outflow pipe is discharged. The shield is shielded from the gas blown out from the mold, and the shield is removed from the dropping path in synchronization with the dropping of the molten glass droplets.

Also in the preform manufacturing method 2, the same dry gas as the manufacturing method 1 is used for the same reason as the preform manufacturing method 1.

The removal of the shield from the dripping path in synchronization with the dripping of the molten glass droplets does not mean that the dripping of the molten glass droplets and the removal of the shield from the dripping path are performed simultaneously. Means to set the timing to remove it. By the difference of the timing which removes the shielding body with respect to the timing of this dropping, it is a preferable aspect of the preform manufacturing method 2 as a 1st aspect which simultaneously performs the removal of a shield from the dropping path of a molten glass droplet, and the dropping path of a molten glass droplet. And 2nd aspect which removes a shield from the dripping path | route of a molten glass droplet after dropping the said glass droplet on a shield.

It is a manufacturing process drawing which shows an example of the 1st form of the preform manufacturing method 2.

Also in the 1st aspect of the preform manufacturing method 2, as shown in FIG. 3, the clarified and homogenized molten glass was prepared, and the molten glass 4 was carried out at the constant outflow velocity from the outflow pipe 2, such as a temperature-controlled platinum alloy agent. Spill. And molten glass droplets are dripped at the shaping | molding part in which the gas outlet of the shaping | molding die 1 which waits below the outflow pipe 2 is formed. A plurality of molding dies 1 are prepared, and when the molten glass droplets 4b are received at a position (called a dropping position) that receives molten glass drops below the outflow pipe 2, they are taken out from the dropping position, and an empty molding die is dropped. Is returned to the location. In this way, a plurality of molding dies are sequentially conveyed to the dropping position, and the molten glass droplets 4b are sequentially received. The molten glass droplets on the mold are subjected to upward wind pressure by a gas (floating gas) 9 blowing upward from the gas outlet, and are formed into a glass molded body while floating. The solidified glass molded body is taken out from the mold and returned to the dropping position again.

In this way, a plurality of forming molds are circulated and used, but since floating gas is ejected from the gas ejection port, when the forming mold is in the dropping position, the floating gas is injected into the outflow pipe, making the outflow condition and the dropping condition unstable.

Here, the meaning that the outflow condition becomes unstable will be described in detail. When the floating gas is injected at the tip of the outflow pipe, the outflow pipe tip is cooled by the gas, so that the temperature of the outflow pipe is changed, and the outflow amount of the glass is changed. However, the dropping weight does not fluctuate largely when the fluctuation range of the outflow amount of glass is small (the reason is mentioned later). On the other hand, when the temperature of the outflow pipe tip decreases, crystals of the molten glass may precipitate at the outflow port, and in this case, the dropping weight may be large, or a stria may occur in the glass molded body. Since the above-mentioned glass composition is generally easy to crystallize in the outflow temperature range, the temperature drop at the tip of the outflow pipe is a big problem.

Next, the meaning of the unstable loading condition will be described in detail. The weight of the droplet is determined by the outer diameter (D) of the outlet, the surface tension (γ) of the glass, and the gravitational acceleration (g) (Equation 1). Strictly, the higher the glass flow rate, the heavier the drop weight, but when the change in flow rate is small, the drop weight does not become a variation factor, so the influence can be ignored. In addition, since gamma depends on temperature, when temperature fluctuation is large, it causes a drop of the droplet weight. Although g is constant on the earth, when the floating gas is injected to the tip of the droplet, g is a force for lifting the droplet, so that g is affected in the same manner as g becomes smaller. In short, when the floating gas is injected from below the droplet, the droplet weight becomes heavy. However, since the flow of the floating gas is disturbed and the force for lifting the droplets is not constant, the dropping weight is more likely to fluctuate than when the floating gas is blocked.

Droplet weight = π Dγ / g. (One)

In this invention, in order to prevent the floating gas 9 from being injected into the outflow pipe 2, as shown in FIG. 3, the shield or support body 3c is divided between the outflow pipe 2 and the shaping | molding die 1; Member) to shield the outflow pipe 2 from the floating gas 9 and form a closed space including the outflow pipe tip with the cover 5 and the shield 3c. In order to fill the dry gas in the sealed space, a constant flow rate of dry gas 6 is flowed into the cover. By controlling the flow rate of dry gas uniformly, the temperature fluctuation of the outflow pipe tip part can be made small. In addition, in order to make the shielding sufficient, the shield 3c is arranged to cross the dropping path of the molten glass droplets so as to remove the shield 3c from the dropping path in synchronization with the dropping. Specifically, the shielding body 3c is composed of a plurality of dividing members, the dividing members are brought into close contact with each other to shield the outflow pipe 2 from the gas 9 which is ejected, and the drop of the molten glass droplets 4b is dropped. The partition members are spaced apart from each other in synchronism with each other, and the shield 3c is disposed so that the molten glass drops 4b fall between the separated partition members. Alternatively, the shielding body is used as a support, receives and supports the dropped glass drops, and after cooling to some extent, separates the partition members as the support, and arranges the support so that the molten glass drops between the separated partition members. In order to reliably and easily perform the above operation, it is preferable that the shield is constituted by two division members.

By shielding the outflow pipe from the floating gas in this way, the outflow condition of the molten glass and the dropping condition of the molten glass droplet can be stabilized, and the mass precision of the glass molded body can be improved. Moreover, as said mass precision, it is desirable to set it as the range within +/- 1% of the target mass.

The 2nd aspect of the preform manufacturing method 2 is the same as that of the 1st aspect of the said preform manufacturing method 2 that the molten glass droplet is dripped from an outflow pipe, and it is a manufacturing method of the preform shape | molded while receiving with the shaping | molding mold which blows out a gas.

It is a manufacturing process drawing which shows an example of the 2nd aspect of the preform manufacturing method 2.

As shown in FIG. 4, the gas 9 which forms the support body 3b (partitioning member in drawing), and blows out the outflow pipe 2 from the said shaping | molding die 1 so that it may cross the dripping path | route of the molten glass droplet 4b. ) And the molten glass droplets 4b dropping vertically downward by receiving the dropped molten glass droplets 4b directly from the support body 3b and then removing the support body 3b. 1) Received and molded. The said support body 3b also has the function of directly receiving the molten glass droplet 4b dripped together with the function of the shielding body in the 1st form of the preform manufacturing method 2. As shown in FIG. Moreover, in the method shown in FIG. 4, the surface which receives the molten glass droplet of the support body 3b is inclined, and the molten glass droplet 4b is settled stably in the position which contact | adhered two division members. By doing in this way, the molten glass droplet 4b is made to fall naturally in the desired position of the shaping | molding die 1, Preferably, the center of a shaping | molding die.

3 and 4, a skirt of an elastic material such as Teflon may be provided between the glass cover 5 and the partition members 3c and 3b without a gap to further improve the sealing property in the cover.

Moreover, what is necessary is just to make the structure, shape, material, and cooling method of the said support body the same as the preform manufacturing method 1.

In the first aspect of the preform manufacturing method 2, it is preferable to drop the molten glass droplets from the outflow pipe in the molding portion in which the gas outlet of the molding die is formed. In the second aspect, the support is provided in the molding portion in which the gas outlet of the molding die is formed. It is preferable to dripped the molten glass droplets which were received.

The second aspect has the following advantages. When glass with extremely low viscosity at the bottom of the oil is inserted directly into a mold exhaling gas, even if it is inserted in the center of the mold, breakage or foam may occur. In particular, in the case of molding a spherical preform, it is necessary to rotate the molten glass at a high speed in the molding die, so that there is a possibility that breakage or foam occurs. Therefore, before spheroidizing with a shaping | molding die, it is necessary to increase the viscosity of a molten glass even a little. In this method, molten glass is hold | maintained on a support body before inserting into a shaping | molding die, and a molten glass is cooled by drawing heat of molten glass from a contact surface. By doing in this way, the breakaway from the glass of the high volatile matter, such as fluorine, and highly reactive component can also be reduced, while preventing a crease and foaming. The cooling means can be considered in addition to that, but there is a risk of cooling the outlet, for example, in a method of blowing gas. Moreover, the method of supporting and cooling a molten glass in a non-contact state with the gas blown out from a porous material using the support body which consists of a porous material can also be considered. However, in addition to the risk of cooling the outlet with gas, the cooling speed is small in the non-contact state, so the dropping interval must be delayed, resulting in a problem of lowering the productivity. That is, a 2nd aspect is suitable from the reason that the viscosity of a molten glass can be reliably increased in a short time, and there is no possibility of cooling an outlet.

In addition, as mentioned above, when drop-inserting a molten glass to a shaping | molding die, it is preferable to make it fall as slow as possible in the center of a shaping | molding, ie, natural fall. In order to realize such a condition, the support body is composed of a plurality of dividing members, the dividing members are brought into close contact with each other to receive the molten glass at the close contact portion, the dividing members are separated from each other, and the molten glass drops fall between the separated dividing members. Use a method to make it work. By doing in this way, the fall distance of a molten glass droplet can be made small, and a molten glass droplet can fall naturally, and can fall naturally below directly without giving an impact to a molten glass droplet. Moreover, the same thing as the molten glass support body used by the preform manufacturing method 1 can be used for a support body.

In the second aspect, the partition member constituting the support is made of a heat resistant metal material, carbon, ceramics, or the like and processed into a thin plate shape. The contact portion with the molten glass is cooled by flowing water or a gas therein to prevent fusion with the glass. In order to control the cooling rate, it is also effective to control the water temperature. Moreover, the division member is inclined toward the contact part so that the position of the molten glass lump dropped, and the support position of the molten glass is made low. The surface does not have to be flat, but may be curved. Moreover, you may form a recessed part in contact with molten glass.

Moreover, in order to reduce the horizontal force applied to the molten glass at the time of separation | separation of a division member, it is preferable to make the surface which supports a molten glass as a grinding | polishing surface, and to coat with fusion prevention and low friction characteristics.

What is necessary is just to be a thing similar to the preform manufacturing method 1 as a conveying system of the film | membrane formed in the material of a shaping | molding die, a shaping | molding surface, and a shaping | molding die.

The said method is suitable also for shaping | molding of glass in which mass precision and quality fall easily by the fluctuation | variation of the outflow conditions of molten glass, and the dropping conditions of molten glass droplets.

Here, in order to perform the process of dripping the said molten glass in the sealed space filled with dry gas, you may put all the front end of the outflow pipe, the shielding body, and the shaping | molding die which shape | molds a preform in a sealed container, and may fill it with the dry gas. Or to cover the space including the tip of the outlet pipe with a cover, and to form an opening in the lower part of the cover so as not to hinder the falling of the molten glass droplets, in order to minimize the space required as described above. Prevent. Except when the molten glass drops into the mold, the space including the tip of the outflow pipe is closed by the cover and the shield. A molten glass is dripped in this sealed space by filling dry gas.

Moreover, it is preferable to use a transparent container as a cover, and it is good to use a glass container. In this way, the leaked state can be observed from the outside.

In this way, it can handle in dry gas atmosphere until a molten glass droplet is sent to a shaping | molding die.

Moreover, what is necessary is just to make the said dry gas the same as the dry gas of the preform manufacturing method 1. Moreover, it is preferable to use said dry gas also for floating gas.

As mentioned above, according to the preform manufacturing method 2, since the molten glass immediately after the outflow is handled in the airtight space filled with dry gas, the surface is smooth and the preform without a defect can be shape | molded.

In addition, since the amount of heat of the molten glass droplets of about the dropping weight is small compared with the amount of heat of the molten glass mass obtained by the preform manufacturing method 1, it is advantageous to the temperature range where the volatile components such as fluorine are difficult to volatilize before introducing into the mold. The surface can be cooled. However, since the cooling of the glass is further promoted by the second form in which the molten glass droplets are brought into direct contact with the shielding body, volatilization of the volatile component can be further reduced. As mentioned above, according to the preform manufacturing method 2, the glass in which the whole surface melt | dissolved was formed by solidification, and it can produce a smooth preform even if it sees microscopically without the microscopic unevenness of scale shape.

Also in the dry gas of the preform manufacturing method 2, the dry gas of the preform manufacturing method 1 can be used.

The preform manufacturing method 2 is suitable for the case of manufacturing the preform of a comparatively small mass. The preferable range of preform mass is 5-600 mg.

In addition, in any of the preform manufacturing methods 1 and 2, when it dropped to a shaping | molding die, a molten glass mass (droplet) is high temperature, although not immediately after the outflow. And since the floating gas is injected only in the lower surface of glass, it is preferable to shape | mold the surrounding atmosphere of a shaping | molding die as said dry gas atmosphere. Although a simpler method, the method of blowing any one of the above gases onto the upper surface of the glass on the mold is effective.

Both preform manufacturing methods 1 and 2 are suitable for molding glass with low outflow viscosity, which is liable to bend, and have high-quality preforms having high mass precision from molten glass having a viscosity of about 0.5 to 50 dPa · s. It may also be molded.

In the glass with a low outflow viscosity as mentioned above, when shape | molding a spherical preform, a molten glass mass (drops) is inserted into the shaping | molding die which has a funnel-shaped hole like FIG. 1, and spheroidization is performed. When the molten glass mass (drops) can be inserted in the center of the mold at the time of inserting the molten glass mass (drops), the molten glass mass is supported and landed on the sprayed gas stream, so that the risk of breaking the molten glass and causing bubbles or stria is reduced. .

However, when the molten glass mass (drop) falls in the state of contacting the inlet of the funnel-shaped hole or the wall, the molten glass mass (drop) may increase due to frictional resistance or instantaneous fusion of the wall and glass. In such a case, it becomes easy to generate | occur | produce a glass, foaming, and a stria by landing. Such a problem is a problem peculiar to the glass having a low viscosity at the time of oil and oil, and is rarely a problem in a glass having a viscosity of 50 dPa · s or more.

Therefore, the molding die is arrange | positioned directly under the outflow pipe, and the bending and the generation | occurrence | production of foam | bubble at the time of inserting a molten glass mass (droplet) in a mold are prevented. However, when the floating gas from the forming mold reaches the outlet of the outflow pipe, problems such as mass variation of the preform and deterioration of the glass occur, so that the gas for floating the glass is formed by the molten glass support in Preform Manufacturing Method 1, In the preform manufacturing method 2, it cuts off by a shielding body and prevents it from reaching an outflow pipe. In the preform manufacturing method 2, it is preferable that the shield used only for the purpose of shielding the floating gas should be thin plate shape, and to make the fall distance of a molten glass droplet as small as possible. As the material of the shielding plate, in consideration of the case where the molten glass is in contact, a heat resistant metal material or the like may be used.

Moreover, in order to shield and remove at high speed in synchronization with dripping, it is preferable to set it as the dividing member with few moving distances.

(About a preform manufacturing method 3)

The third method (hereinafter referred to as preform manufacturing method 3) of the method for producing a preform is formed into a glass preform while dropping molten glass droplets from an outflow pipe, receiving a gas into a molding mold and applying wind pressure with the gas to float. In the method of manufacturing a preform for forming an optical element, the dropping of the molten glass droplets is carried out in a closed space filled with dry gas, and a shielding body is formed so as to cross the dropping path of the molten glass droplets so that the outflow pipe is discharged. It shields from the gas blown out from a shaping | molding die, and also adds molten glass droplets on the said shield, and removes the said shield from the said dripping path | synchronous in synchronization with dripping of molten glass droplets.

The preform manufacturing method 3 is the same as that of the preform manufacturing method 2 except having made dripping molten glass droplets on a shielding body as a prerequisite, and as a preferable form of the preform manufacturing method 3, it is the same as that demonstrated by the 2nd form of the said preform manufacturing method 2 Form.

(About a preform manufacturing method 4)

The fourth method of the manufacturing method of the preform (hereinafter referred to as preform manufacturing method 4) separates a certain mass of molten glass mass from the molten glass flowing out of the outlet of the outlet pipe, and blows off a gas for applying wind pressure to the glass mass. In the manufacturing method of an optical element molding preform which is received by a molding mold and molded into a glass preform while floating, a cover having an opening that can be opened and closed vertically downward of the outlet is covered with a space including the outlet and the opening is closed. When the space is sealed, the drying gas is supplied into the space, the molten glass lump is separated in the state where the opening is closed, and the opening is opened to form a mold for ejecting the dry gas disposed close to the opening. The glass mass is transferred and molded.

As dry gas, the thing similar to the thing of the preform manufacturing method 1 or 2 can be used.

Since the preform manufacturing method 4 can move a molten glass mass from a sealed space to a shaping | molding mold in the state which adjoined the opening part of a sealed space, and a shaping | molding die, the glass of high temperature can be handled in dry gas atmosphere for a long time, and it is highly reactive at high temperature. A favorable preform can also be shape | molded also with the glass which shows.

From the viewpoint of preventing the occurrence of defects such as bending by minimizing the falling distance of the molten glass lump, the opening is opened after bringing the opening into close contact with the upper end of the mold, and the molten glass lump is dropped into the mold. It is preferable.

Moreover, it is preferable to make a molten glass lump free fall in a perpendicular direction from the point which prevents bending, and to fall to the center of the shaping | molding part of a shaping | molding die.

In order to produce the high quality preform more stably, the method which combined the preform manufacturing methods 1 and 4, or the method which combined the preform manufacturing methods 2 and 4 is more preferable.

As a suitable glass for producing the preform of the present invention, fluorine-containing glass, phosphate glass, boron-containing glass, boron and fluorine-containing glass, Bi-containing glass, Bi and fluorine-containing glass, Bi-containing phosphate glass, Bi and boron-containing Glass, Bi, boron, fluorine containing glass, etc. can be illustrated.

In this invention, it is preferable to introduce Bi into a glass component from the point which reduces the wettability of the molten glass with respect to the outflow pipe tip outer periphery, and improves the high temperature stability of glass.

It is thought that the said wet glass stays in a pipe outer periphery for a comparatively long time, and volatile and high reactivity components, such as fluorine and a boron, detach | deviate and deteriorate in the meantime. When the glass deteriorated in this way enters into a molten glass mass or a molten glass droplet, a heterogeneous portion is formed in the preform and becomes a defect. Therefore, it is desired to reduce the wetness as much as possible.

By introducing Bi, the surface tension of the molten glass is increased, and not only the reduction of the wetness, but also the stria reduction and the surface of the preform smoothly microscopically can be produced efficiently. Moreover, in order to reduce the said wetness, use of the gold-containing platinum alloy outflow pipe is preferable.

In addition, it is preferable to perform dissolution of fluorine-containing glass (for example, fluorophosphate glass) in a dry gas atmosphere. It may also be dissolved in the dry gas atmosphere. In this way, the preform which consists of fluorophosphate glass in which the refractive index nd exists in the range of 1.4-1.65 and Abbe number (vd) is 65-97 can be manufactured.

(About a preform manufacturing method 5)

The fifth method (hereinafter referred to as preform manufacturing method 5) of the method for producing a preform separates a certain mass of molten glass mass from the molten glass flowing out from the outlet of the outlet pipe, and applies a gas for applying wind pressure to the glass mass. In the manufacturing method of the optical element shaping | molding preform which receives by the shaping | molding mold which blows out and shape | molds and forms it into a glass preform, the gas blown out from the said shaping | molding die is dry gas, and the said glass is fluorine-containing glass, It is characterized by the above-mentioned.

The said dry gas is the same as the gas used as a floating gas by the preform manufacturing methods 1-4. In addition, the method of melting the molten glass, the outflow method, the method of separating the molten glass mass, the method of transferring the separated glass mass to the mold, and the method of molding the glass mass on the mold are also used in each of the methods of the preform manufacturing methods 1-4. It can be adopted. In this way, the preform which consists of high quality fluorine-containing glass can be shape | molded. The said method is suitable for shaping | molding the preform which consists of fluorophosphate glass in which refractive index (nd) exists in the range of 1.4-1.65, and Abbe number (vd) is 65-97.

All of the preform manufacturing methods 1-5 are suitable for manufacture of each preform demonstrated below.

Next, the preform manufactured by the method of this invention is demonstrated.

[Preform]

The 1st preform manufactured by the method of this invention is a preform produced by the manufacturing method of this invention, The 2nd preform consists of fluorophosphate glass containing Bi, and the glass which melt | dissolved in the whole surface is solidified It is a preform, characterized in that formed.

In the preform of the present invention, the entire surface is formed by the solidification of the glass in the molten state, and there are no minute scratches or invisible scratches such as polishing traces. Moreover, since there is no minute unevenness | corrugation, it is a microscopically smooth surface. By such a preform, the surface of the precision press-molded product, in particular, the surface of the optical functional surface can be made a good surface without microscopic unintended unevenness, and the light scattering in the optical functional surface and the performance deterioration as an optical element can be prevented. . Moreover, as a preform manufactured by the method of this invention, it is preferable that the whole surface is a free surface.

Next, a preferable shape of the preform will be described. In the case of precision press molding, the preform is preferably isotropically enlarged, and the optical element, which is the main use of the precision press molding, has a rotationally symmetrical axis in that the main shape of the lens shape, which is particularly in demand, has a rotational symmetry axis. A shape having a rotational symmetry axis is preferable. As a shape having one rotationally symmetrical axis, preferable ones are as follows.

In the cross section including the axis of symmetry, a straight line which forms a point on the outline of the preform and the center of the preform, and a tangent tangent to the outline at the point on the outline is considered. And it is a preferable shape that angle (theta) which a said straight line and a tangent make changes as follows. That is, θ is 90 ° at the intersection of the rotational symmetry axis and the contour, and as the point on the contour moves from this intersection, θ increases monotonically, then shifts to monotonic decrease, and monotonously decreases even after 90 ° again. Then, the process shifts to forging increase and returns to 90 ° from the other side of the intersection of the rotational symmetry axis and the contour. In this case, since the preform is a rotating body, θ becomes 90 ° again at the intersection of the starting point while exhibiting the same behavior as the above behavior. In addition, in the case where θ is taken as the complementary angle of θ, the forging increase and the decrease in forging are shown.

By such a shape, the atmosphere gas is filled between the preform and the press forming mold at the time of precision press molding, so that the risk of a gas trap that becomes poor in molding can be reduced. In addition, in order to further reduce the risk of such a gas trap, what is necessary is just to shape | mold so that the radius of curvature of the surface of a preform may become smaller than the radius of curvature of a press molding die shaping surface.

Next, the case where the preform manufactured by the method of this invention consists of fluorophosphate glass is demonstrated. Taking advantage of the fact that the optical glass is a phosphate glass, the optical glass preferably has a low dispersion characteristic having an Abbe number (υd) of 65 or more, and particularly has a refractive index (nd) of 1.4 to 1.65 and an Abbe number (υd) of 65 to 97. It is preferable.

Next, the preferable composition of optical glass is demonstrated.

(Preferred composition I)

The first preferred phosphate glass is one containing Bi ions as the cationic component. Bi ion introduction improves the high temperature stability of the glass and has the effect of reducing the wetness to the outflow pipe. In addition, the surface tension is increased by the introduction of Bi, and not only the reduction of the wetness, but also the stria reduction and the surface of the microscopically smooth preform can be produced efficiently. The amount of Bi introduced is 0.2 to ₂₀ mol% in BiF ₃ and more than 0 mol% and 10 mol% or less in Bi ₂ O ₃ .

(Preferred composition II)

The second preferred phosphate glass is P ⁵⁺ , Al ³⁺ , Ba ²⁺ , Ca ²⁺ , Sr ²⁺ as an essential cationic component, and Mg ²⁺ , Zn ²⁺ , Li ⁺ , Na ⁺ as an optional cationic component. , K ⁺ , Si ⁴⁺ , B ³⁺ , La ³⁺ , Gd ³⁺ , Y ³⁺ , W ⁶⁺ , Nb ⁵⁺ , Bi ³⁺ , O ^2- , F ⁻ as an essential anion component Cl as the anion component ^- a non-phosphate glass containing ^-, Br. Specifically, in mol%, Al (PO ₃ ) ₃ 0-15%, Ba (PO ₃ ) ₂ 1-25%, AlF ₃ 2-45%, YF ₃ 0-15%, LaF ₃ 0-10 _{%, GdF 3 0~10%, MgF} 2 0~20%, CaF 2 2~45%, SrF 2 2~45%, BaF 2 0~20%, ZnF 2 0~30%, LiF 0~10%, NaF 0-15%, KF 0-15%, SiO ₂ 0-5%, B ₂ O ₃ 0-5%, Li ₂ O 0-5%, Na ₂ O 0-5%, K ₂ O 0-5 %, MgO 0-5%, CaO 0-5%, SrO 0-5%, BaO 0-5%, ZnO 0-5%, Y ₂ O ₃ 0-5%, Al ₂ O ₃ 0-5%, 0 to 5% of Gd ₂ O _3, 0 to 5% of Nb ₂ O _{5, and} 0 to 5% of WO ₃ .

The reason for limiting the composition range of each component is as follows.

Al (PO ₃ ) ₃ is a component constituting the mesh structure of glass and is the most important component to increase the weather resistance of glass. However, if the content exceeds 15%, the thermal stability of the glass is lowered and the liquidus temperature is also the optical characteristic ( Since dispersion | distribution increases, there is a possibility that it will deteriorate significantly, and the introduction amount shall be 15% or less. More preferably, it is 0.5 to 12% of range.

Ba (PO ₃ ) ₂ is a component constituting the mesh structure of the glass, and is an indispensable component for improving the weather resistance of the glass. If the content is less than 1%, the weather resistance of the glass remarkably decreases, and the stability also deteriorates. On the other hand the introduction of in excess of 25%, in addition to decrease of the optical hangsu (Abbe number) of the glass, weather resistance is deteriorated by the increase in the P ₂ O _5. Therefore, the introduction amount is made into 1 to 25%. More preferably, it is 2 to 20% of range.

AlF ₃ is a component that stably and low-disperses the glass, but if the content exceeds 45%, the glass stability is significantly lowered, solubility worsens, while the target optical properties are not obtained at less than 2%. The amount of introduction is in the range of 2 to 45%. More preferably, it is 4 to 40% of range.

YF ₃ , GdF ₃ and LaF ₃ have high effect of improving the devitrification resistance by addition of small amount, but when the amount of YF ₃ , GdF ₃ and LaF ₃ introduced exceeds 15%, 10% and 10%, respectively, the glass is unstable Since it becomes fixed and it becomes easy to devitrify, the introduction amount is suppressed to 15%, 10%, and 10% or less, respectively. More preferably, the content of YF ₃ is 12% or less, the content of GdF ₃ is 8% or less, and the content of LaF ₃ is 7% or less.

When MgF ₂ is introduced in excess of 20%, the crystallization tendency of the glass increases and the glass becomes unstable. Therefore, the amount of the MgF ₂ is made 0 to 20%. Since a small amount of MgF ₂ introduction contributes to improving the stability of the glass and greatly contributes to low dispersion of the glass, it is preferable to introduce more than 0%, more preferably 1 to 18%.

CaF ₂ and SrF ₂ are indispensable components for maintaining glass devitrification resistance and low dispersion. In particular, CaF ₂ plays a role of reinforcing the glass structure in combination with AlF _3, and is a component which is absolutely indispensable for the stabilization of the glass. However, when the amount of CaF ₂ and SrF ₂ introduced is less than 2%, the stability of the glass is deteriorated, and it is difficult to obtain a desired optical constant. If the amount is more than 45%, the glass may be unstable. Therefore, the introduction amount is made into 2 to 45% of range. More preferably in the range of _{CaF 2 5~40%, SrF 2 3~35} %.

Although ZnF ₂ is a component to be introduced in order to increase the stability and weather resistance of the glass, when the amount of introduction exceeds 20%, the glass becomes unstable on the contrary, so the amount of introduction is made 0 to 20%. A more preferable introduction amount is 1 to 16% of range.

BaF ₂ is a component which is very useful for improving the stability of the glass and improving the refractive index. However, when more than 30% is introduced, BaF ₂ increases the crystallization tendency and becomes difficult to dissolve, so the introduction amount is made 0 to 30%. More preferable introduction amount is 2 to 25% of range.

LiF, NaF, and KF have the effect of improving the devitrification resistance and dispersibility of the glass by the addition of a small amount, but the introduction of LiF, NaF, and KF deteriorates the stability of the glass rapidly and deteriorates the durability. The amount of introduction is suppressed to 10%, 15% and 15% or less, respectively. More preferably, they are 0-5%, 0-10%, and 0-10%, respectively.

SiO ₂ , B ₂ O ₃ , Li ₂ O, Na ₂ O, K ₂ O, MgO, CaO, SrO, BaO, ZnO, Y ₂ O ₃ , Al ₂ O ₃ , Gd ₂ O ₃ , Nb ₂ O ₅ , WO ₃ is an optional component and has an effect of improving the stability, weather resistance, and durability of the glass by introducing a small amount of the above component, but the amount of the introduction may be deteriorated or the dispersibility may be deteriorated. Are each 5% or less. More preferably, it is 4% or less.

In addition, small amounts of compounds such as Cl and Br can be introduced for the purpose of adjusting bubbles and optical constant number.

Moreover, the preferable glass composition II containing Bi can also be made combining the preferable glass composition II and the preferable glass composition I.

In addition, as water resistance of the fluorophosphate glass which comprises a preform, it is preferable that it is less than 0.25 in a feeling of mass (%) in the water resistance test by the Japan Optical Glass Industry Association standard.

In addition, as fluorophosphate glass which comprises a preform, it is hold | maintained for 1 week in the constant temperature and humidity chamber filled with the clean air of temperature 65 degreeC and 90% of a relative humidity in the state which double-sided optically polished, and the scattered light at the time of transmitting white light to the said polishing surface It is desirable to have weather resistance such that the intensity ratio of the transmitted light is 8.0 or less.

In addition, fluorophosphate glass having a glass transition temperature (Tg) of 500 ° C or less is preferable from the viewpoint of precision press formability.

Moreover, it is preferable that the wavelength which becomes 80% of glass internal transmittances (thickness 10mm conversion) which does not contain reflection on a glass surface and scattering loss exists in the range of 300-370 nm.

Moreover, when introducing an absorbent into glass and providing a filter function, you may introduce a coloring component into glass. For example, by introducing an appropriate amount of Cu ions, near infrared absorption characteristics can be imparted, and an optical element having a near infrared absorption function can also be obtained by precise press molding.

The preform obtained by shaping | molding and slow cooling from a molten glass is wash | cleaned and dried as needed. Moreover, you may form the film | membrane which has a lubrication effect in the preform surface so that a mold release effect and glass may become easy to spread on the surface of a press molding die. Such a film is preferably formed over the entire preform surface. Examples of the film include a carbon containing film and a self-organizing film. As a carbon containing film, a vapor deposition carbon film, the carbon film formed by CVD, etc. can be illustrated.

Next, the optical element of this invention is demonstrated.

Optical element

The optical element of the present invention is an optical element produced by heating a preform produced by the production method of the present invention and precisely press molding it. Examples of such optical elements include lenses, prisms, prism with lenses, diffraction gratings, polygon mirrors, and the like. Examples of the lens include spherical lenses, aspherical lenses, micro lenses, pickup lenses, collimator lenses, lens arrays, and the like.

By using the preform with high mass precision, the element whose whole surface of the optical element is a surface formed by precision press molding can also be obtained. By forming the whole optical element surface by precision press molding, there is no need to perform shape processing on the precision press molded product by machining, such as grinding and polishing. The non-optical functional surface (called the lens peripheral portion) around the optical functional surface of the lens may be used when the lens is fixed to the holder. In order to use this lens peripheral portion as a reference for positioning when fixing the holder, the relative positional relationship and angle of the optical axis of the lens and the lens peripheral portion need to be precisely formed in a predetermined relation. By simultaneously molding the optical functional surface and the lens peripheral portion by precision press molding, it is possible to impart the function of the positioning reference of the lens to the lens simultaneously with the press molding.

In addition, when forming the whole surface of an optical element by precision press molding, it is preferable that the mass precision of the preform for optical element shaping | molding to be used shall be within +/- 1% of a target value.

When the optical element is made of phosphate glass, it is possible to provide an optical element of low dispersion or ultra low dispersion. In addition, since fluorophosphate glass has high UV transmittance, it is suitable for lenses (spherical lenses, aspherical lenses, micro lenses, pickup lenses, collimator lenses, lens arrays, etc.), prisms, and prism lenses for optically controlling ultraviolet rays. .

Moreover, the optical element which has a light absorption function can also be obtained by using the preform which introduce | transduced the coloring agent as mentioned above. As such an element, an optical element having a near infrared absorption function added with Cu ions, for example, the above-described various optical elements may be provided.

In addition, on the surface of the optical element, an optical multilayer film such as an antireflection film, a partial reflection film, a high reflection film, or a single layer film may be formed.

[Method of Manufacturing Optical Device]

The manufacturing method of the optical element of this invention is characterized by heating the preform produced by the manufacturing method of this invention, and performing precision press molding using a press molding die.

By this method, a high quality optical element can be produced without defects such as uneven microscopic unevenness, alteration, stria, and devitrification in the optical function surface. It is especially suitable for the manufacture of optical elements made of phosphate glass.

The 1st method (it is called manufacturing method 1 of an optical element) of the manufacturing method of an optical element is a method of introduce | transducing a preform into a press molding mold, heating the said preform and a press molding mold together, and performing a precision press molding.

A second method of manufacturing a method of manufacturing an optical element (called a manufacturing method 2 of an optical element) is a method of precise press molding by heating the preform and the press forming mold separately, and then introducing the preform into the press forming mold.

In the manufacturing method 1 of an optical element, it is preferable to make temperature of the press molding die and the temperature of a preform into the temperature which the glass which comprises a preform shows the viscosity of 10 <^8> -10 <^12> dPa * s. Moreover, it is preferable to take out from a press molding mold after the said glass cools to the temperature which shows the viscosity of 10 ¹² dPa * s or more, and press-forms after cooling to the temperature which shows the viscosity of 10 ¹⁴ dPa * s or more. It is more preferable to take out from a mold | die, and it is still more preferable to take out from a press molding mold after cooling to the temperature which shows a viscosity of 10 ¹⁶ dPa * s or more.

In the manufacturing method 1 of an optical element, it is preferable to introduce the preform preheated at higher temperature than the temperature of a press molding die, and to perform precise press molding. In this method, it is preferable to mold-release after press molding after the viscosity of the glass which comprises a preform becomes 10 ¹² dPa * s or more.

In addition, it is preferable to preheat the preform and injury, and more preferably preheated to a temperature above the glass showing a viscosity of 10 ^5.5 ~10 ⁹ dPa · s. In addition, it is preferable to start cooling of the glass simultaneously with the start of the press or during the press.

In the preheating of the preform, the preheating temperature is preferably set to a temperature at which the glass exhibits a viscosity of 10 ⁹ dPa · s or less, and more preferably a temperature showing a viscosity of 10 ^5.5 to 10 ⁹ dPa · s. Moreover, it is preferable to make the temperature of a press molding die into the temperature at which the said glass shows 10 <^9> -10 <^12> dPa * s.

In the production method 2 of the optical elements, after heating the preform for introducing a press forming die, it is preferable to heat the temperature of the preform, at a temperature of glass for forming the preform showing a viscosity of less than 10 ⁹ dPa · s, 10 ^5.5 is more preferable to heat to a temperature at which the viscosity of ~10 ⁹ dPa · s, and 10 ^5.5 it is more preferable to heat to a temperature at which the viscosity of dPa · s or more and less than 10 ⁹ dPa · s. Moreover, it is preferable to heat, heating the said preform.

Moreover, although the temperature of a press molding die is adjusted to the temperature lower than the heating temperature of the said preform, what is necessary is just to aim at the temperature which the said glass shows the viscosity of 10 <^9> -10 <^12> dPa * s.

Moreover, it is preferable to start cooling of a glass simultaneously with starting a press or in the middle of a press, and after press molding, it is preferable to release, after cooling the glass to 10 ¹² dPa * s or more.

In any of the above methods, using a mold material made of SiC, cemented carbide, heat-resistant metal, or the like, a press-molded mold in which a release film such as a carbon film or a noble metal film is formed on a molding surface, if necessary, can be used. Press molding can be performed in an atmosphere such as a mixed gas of hydrogen or an inert gas. In the press-molded optical element, the above-described film may be formed after slow cooling.

As described above, according to the manufacturing method of the optical element of the present invention, since a high quality preform is used, a good optical element can be produced without surface defects and internal defects.

In addition, since the mass precision of the preform is high, an optical element can be made without performing machining on surfaces other than the optical functional surface.

Example

Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.

In addition, the physical property of glass was measured as follows.

(1) refractive index (nd) and Abbe's number (υd)

It measured about the optical glass obtained by cooling at the temperature-fall rate of 30 degreeC per hour.

(2) Glass transition temperature (Tg) and yield point (Ts)

It measured at the temperature increase rate of 4 degree-C / min using the thermomechanical analyzer.

Example 1

The molten glass obtained by heat-melting the glass raw material which combined the predetermined amount of batch, degassing | defoaming clarification, and stirring homogenization is continuously dripping from the temperature-controlled platinum alloy nozzle at a constant outflow rate. The extraction amount of glass at this time was 9.5 kg / day. Moreover, the composition and the characteristic of the glass obtained from the said molten glass are as showing in Table 1.

The subsequent molten glass flow is molded into the preform by the apparatus shown in FIGS. 1 and 2.

The molten glass support body used in the present embodiment is constituted by two flat plate-shaped dividing members, and the surface receiving the front end of the molten glass flow is mirror-finished, so as to form one plane in a state where the dividing members are in close contact with each other. It is. In addition, in order to control the outlet and the support in a dry atmosphere (dry air), it mounted as shown in Figs. 1 and 2 the SiO ₂ glass cover, and controls a dry atmosphere (dry air) by sending the glass melt into the forming die . Moreover, in order to prevent fusion with a molten glass, the water channel is formed in the inside of a molten glass support body, and cooling water flows and is cooled by water. The temperature of the support was controlled by controlling the amount and water temperature of water cooling. In addition, carbon such as diamond was coated on the surface of the molten glass support.

First, as shown in FIG. 1, a molten glass support body is raised in the state which contact | adhered to a partition member, and it moves to 4 mm below from the surface which receives the tip of a molten glass flow, and an outflow pipe outlet, and stops. In this state, the surface receiving the tip of the molten glass flow is maintained in a horizontal state (the state in which the receiving surface faces vertically upward). Subsequently, the falling end is supported at the boundary of the two dividing members in close contact with the tip of the molten glass flow. The size of the molten glass supported on the molten glass support becomes large with time. When there is much quantity of molten glass, a pipe tip may be buried in molten glass, and a stria may generate | occur | produce. Therefore, in order to maintain the distance of a molten glass and an outflow nozzle, you may lower the said support body in a perpendicular direction at low speed. If a molten glass having a desired mass is accumulated on the support, the support is dropped vertically downward in a state in which the support member is in close contact with the support member, and the glass flow is cut off by the surface tension of the glass, and Obtain a molten glass chunk. Moreover, what is necessary is just to make the fall distance of the said support body the distance which can cut | disconnect the molten glass flow. Subsequently, the division members were separated from each other, and the molten glass mass was dropped vertically between the two division members. The molten glass lumps that have fallen are dropped into a mold which is waiting under the support, and are molded into a preform while floating by a gas (dry air) blown out from the bottom of the mold.

After the molten glass lump is dropped from the molten glass support, the divided members are immediately returned to the state in which they are in close contact with each other. By this operation, the support blocks the gas, thereby preventing the gas from being injected into the outflow pipe. The support is then raised again to receive the tip of the molten glass flow.

The glass molded body cooled and solidified with time on the mold is sucked out, taken out from the mold, and transferred to the pellet for slow cooling. In this way, the preform of a predetermined | prescribed mass is manufactured one by one from the molten glass which flows out continuously.

In addition, as shown in FIG. 2, by separating a partition member from each other, the molten glass mass of predetermined mass is isolate | separated without using a cutting blade, it falls naturally in the center of a shaping | molding die, and the predetermined | prescribed mass of preform is carried out from the molten glass continuously discharged. It also carried out a method of manufacturing in order. A taper is attached to the dividing member, and the opening angle of the state in which the dividing member is brought into close contact is 150 °. By attaching this taper, the position which receives a molten glass became more stable, and the precision of the fall position of a molten glass lump improved.

In this way, the preform preparation cycle was set to 3.2 second, the 350 +/- 3 mg spherical glass molded object which consists of optical glass was produced, and it was set as the preform which consists of fluorophosphate glass.

No defects such as cracks or other scratches, striae, kinks or devitrification were observed in the preform.

Moreover, when the preform surface was expanded and observed with the optical microscope, the whole surface was a smooth surface.

Also, in order to separate the glass flow with one split member, the separation accuracy of the glass flow is much improved than in the case of separating the glass flow with a plurality of molds, and the temperature of the outflow pipe tip is increased by the gas injected from the molds. Since it did not fluctuate, the mass precision was also high in the range of ± 1% of the target value as described above.

Example 2

The molten glass similar to Example 1 obtained by heating and melting the combined glass raw material, degassing, clarifying, and stirring homogenization is continuously dropped from the temperature-controlled platinum alloy pipe at a constant outflow rate. The extraction amount of glass at this time was 8 kg / day.

The flowing molten glass flow is molded into a preform for press molding by the apparatus shown in FIG.

The shielding body used in the present embodiment is constituted by two flat plate-shaped partition members. The splitting members are in close contact with each other to shield the tip of the outlet pipe from the flow of gas or air from below, but the splitting members are spaced apart from each other in accordance with the timing at which the molten glass drops drop from the tip of the outlet pipe. Through it, molten glass drops fall into the mold. As soon as molten glass droplets pass between the partition members, the partition members are brought into close contact with each other to shield the outflow pipe from the floating gas described later.

Moreover, it can also shape | mold in preform for press molding by the apparatus shown in FIG.

The support body used in FIG. 4 is comprised by the two divided members in which the surface which receives a molten glass droplet is inclined. The splitting members are in close contact with each other, shielding the tip of the outlet pipe from the flow of gas from below, and after the molten glass drops are dropped onto the support from the tip of the outlet pipe, the glass molten droplets are cooled to some extent, and then divided. The members are spaced apart from each other, and the molten glass droplets fall into the mold by passing through the spaced apart partition members. As soon as the molten glass droplets pass between the partition members, the partition members are brought into close contact with each other to shield the outflow pipe from the gas.

The molten glass drops dropped on the mold are molded into a glass molded body in a spherical shape while being floated while being rotated by the floating gas (dry air). Subsequently, the cooled and solidified glass molded body is sucked out, taken out of the mold, and transferred to a pellet for slow cooling. Thus, the molten glass which flows out continuously is dripped in dry air atmosphere, and the glass molded object of a predetermined mass is manufactured one by one.

In this way, a 350 ± 1.4 mg spherical preform made of phosphate glass was produced.

No defects such as cracks, other scratches, stria, and devitrification were observed in the preform. In addition, the weight accuracy was as high as falling within ± 1% of the target value as described above.

In addition, when the surface of the preform was enlarged by an optical microscope, fine irregularities were not seen, and the surface was smooth. The entire surface was a free surface.

In addition, the amount of water in the dry atmosphere and the amount of water in the floating gas at the time of flowing out the molten glass in Examples 1 and 2 and obtaining a molten glass mass or a molten glass mass were 380 ppm or less.

In addition, the glass outflow atmosphere may be a nitrogen gas having a water content of 380 ppm or less, the flotation gas may be the dry nitrogen gas, or dry argon having a dew point of -30 ° C. or less may be used as the glass outflow atmosphere or the flotation gas. Good results can be obtained.

Example 3

After the molten glass droplets were dropped on the shielding body, a preform was produced in the same manner as in Example 2 except that the partition members constituting the shielding body were separated.

The two flat plate-shaped dividing members constituting the shielding body are brought into close contact with each other to shield the tip of the outflow pipe from the flow of gas or air from below, and the molten glass droplets are dripped from the outflow pipe to the closely-contacted portions of the dividing member. Positioning was carried out so that molten glass was dripped from the front-end | tip of an outflow pipe in the sealed space filled with dry gas.

After the molten glass droplets were cooled to some extent by bringing the molten glass droplets into contact with the partition members in close contact with each other, the partition members were separated from each other, and the molten glass droplets dropped through the spaced apart partition members into the mold.

The space | interval of a partition member was performed after dripping molten glass droplets, and the fixed time required for cooling a molten glass droplet on a partition member passed. In this sense, it can be said that the timing of removing the shielding body is determined by the dropping timing of the molten glass droplets, and the partition member is removed from the dropping path in synchronization with the dropping of the molten glass droplets.

Immediately when the molten glass droplets pass through the splitting members, the splitting members are brought into close contact with each other to shield the outflow pipe from the floating gas (dry air), and a spherical preform is sequentially produced as in Example 2. It was.

In this way, the 350 + 1.4 mg spherical glass molded object which consists of glass similar to the optical glass in the said Example 2 was produced, and it was set as the preform for optical element shaping | molding.

No defects such as cracks, other scratches, stria, and devitrification were observed in the preform for optical element molding. As described above, the mass accuracy was also high within ± 1% of the target value.

In the present embodiment, the amount of water in the dry atmosphere and the amount of water in the floating gas when the molten glass was flowed out to obtain the molten glass droplets were 380 ppm or less.

In the present embodiment, the shielding body is composed of two partitioning members that are closely spaced from each other, but may be composed of three or more partitioning members that are tightly spaced apart from each other, and is further provided below the shielding body composed of two partitioning members that receive molten glass drops from the outlet pipe. When a separate shield is formed in the upper portion and the divided member provided above is separated, the lower shield may be removed from the dropping path.

In addition, the glass outflow atmosphere may be a nitrogen gas having a water content of 380 ppm or less, the flotation gas may be the dry nitrogen gas, or dry argon having a dew point of -30 ° C or less may be used as the glass outflow atmosphere or the flotation gas, and in these cases, You can get the result.

Example 4

After washing and drying the preform made of the fluorophosphate glass molded in Examples 1 to 3, precision press molding was performed to produce an aspherical lens. In the above press molding, the atmosphere was made into a nitrogen atmosphere by using a press molding mold in which a carbon film was formed on the surface of a SiC mold material. The press molding was performed by heating the preform to a temperature of 600 ° C. or lower and pressing it at a pressure of 10 MPa for 60 seconds. After press molding, the aspherical lens was taken out from the press molding mold and cooled slowly. The obtained lens was in a good state both inside and the surface. In addition, even when the lens surface is magnified, fine irregularities were not observed. The lens did not need to be subjected to the center removal processing, and the lens could be used as a positioning reference when fixing the lens peripheral portion formed by the precision press molding to the holder. An antireflection film may be formed on the surface thus obtained.

In addition, in the said precision press molding, a preform may be introduce | transduced into a press molding die, and a preform and a press molding die may be heated simultaneously, and the heated press molding die may be thrown in and pressed into the preheated press molding die.

This embodiment relates to a method for producing an aspherical lens, but can also be applied to the production of other optical elements such as prisms and diffraction gratings.

Comparative example

The molten glass from which the glass of the composition similar to Examples 1-3 was obtained was dripped from the outflow pipe in air | atmosphere, it was introduce | transduced into the shaping | molding mold which injects the floating gas waiting under the outflow pipe, and it shape | molded to the spherical preform, making it float. . The preform was slowly cooled and then magnified by an optical microscope, and fine irregularities in the shape of scales were observed throughout the surface.

Subsequently, when this preform was press-molded exactly like Example 4, the fine unevenness | corrugation was observed in the obtained lens surface. In addition, because the floating gas is injected into the outflow pipe, the mass precision of the preform deteriorates.

Moreover, the molten glass from which the glass of the composition similar to Examples 1-3 is obtained flows out from an outflow pipe in air | atmosphere, and receives the front-end | tip into the shaping | molding die which blows off floating gas, and by predetermined distance at the timing which glass of predetermined mass is obtained. The mold was lowered to obtain a molten glass mass on the mold. The molten glass cake was floated and molded into a spherical preform. The preform was slowly cooled and then magnified with an optical microscope, and fine irregularities in the shape of scales were observed throughout the surface.

Subsequently, when this preform was press-molded exactly like Example 4, the fine unevenness | corrugation was observed in the obtained lens surface.

According to the manufacturing method of the preform of this invention, the high quality glass preform for optical element shaping | molding can be manufactured efficiently. By precise press molding of this preform, various optical elements that do not need to be subjected to shape processing by machining such as grinding and polishing can be produced.

Claims (12)

In the manufacturing method of the preform for optical element shaping | molding which isolate | separates a fixed mass of molten glass lump from the molten glass which flows out from the outlet of an outflow pipe, applies a wind pressure to the glass lump, and forms it into a glass preform while making it float. The process of receiving and supporting the front end of a molten glass flow by the molten glass support body arrange | positioned under an outflow pipe, removing the support by the said molten glass support body, and separating the said molten glass mass from the front end of a molten glass flow as a dry gas. A method for producing an optical element molding preform, which is carried out in a sealed space filled. In the manufacturing method of the optical element shaping preform dropping the molten glass droplets from the outflow pipe, received into a mold for ejecting the gas, and formed into a glass preform while applying the wind pressure by the gas to rise. The dropping of the molten glass droplets is carried out in a sealed space filled with dry gas, and a shielding body is formed to cross the dropping path of the molten glass droplets to shield the outflow pipe from the gas ejected from the mold, and further melt And a method of removing the shield from the dropping path in synchronization with the dropping of glass droplets. In the manufacturing method of the optical element shaping preform dropping the molten glass droplets from the outflow pipe, received into a mold for ejecting the gas, and formed into a glass preform while applying the wind pressure by the gas to rise. The dropping of the molten glass droplets is carried out in a closed space filled with dry gas, and a shielding body is formed to cross the dropping path of the molten glass droplets to shield the outflow pipe from the gas ejected from the mold. A molten glass drop is dropped on the shield, and the shield is removed from the dropping path in synchronization with the drop of the molten glass drop.  The manufacturing method of the preform for optical element shaping | molding of any one of Claims 1-3 whose gas for applying wind pressure is a dry gas.  A preform for forming an optical element which separates a certain mass of molten glass mass from a molten glass flowing out of an outlet of an outflow pipe, receives a mold for ejecting a gas for applying wind pressure to the glass mass, and forms a glass preform while floating. In the manufacturing method, A cover having an opening that can be opened and closed vertically downward of the outlet, covering the space including the outlet, closing the opening when the opening is closed, and supplying a dry gas into the space to close the opening. And dissolving the molten glass agglomerates and transferring the glass agglomerates to a molding mold which opens the openings and ejects the dry gas disposed in close proximity to the openings. The manufacturing method of the optical element shaping preform as described in any one of Claims 1, 2, 3, and 5 which shape | molds the preform which consists of glass containing fluorine. The manufacturing method of the preform for optical element shaping | molding of any one of Claims 1, 2, 3, and 5 which shape | molds the preform which consists of glass containing Bi. A preform for forming an optical element which separates a certain mass of molten glass mass from a molten glass flowing out of an outlet of an outflow pipe, receives a mold for ejecting a gas for applying wind pressure to the glass mass, and forms a glass preform while floating. In the manufacturing method, The gas blown out from the said molding die is a dry gas, and the said glass is fluorine-containing glass, The manufacturing method of the preform for optical element formation characterized by the above-mentioned. delete Claim 1, 2, 3, 5 and 8 to heat the preform for forming the optical element produced by the method according to any one of claims, and to press-preform using a press molding mold Method for manufacturing an optical device characterized in that. The method for manufacturing an optical element according to claim 10, wherein the preform for optical element molding is introduced into a press molding mold, and the preform and the press molding mold are heated together to perform precision press molding. The method for manufacturing an optical element according to claim 10, wherein the preform for forming the optical element and the press forming mold are heated separately, and then the preform is introduced into the press forming mold to precise press molding.

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