KR101389584B1 - A group of glass preforms and processes for the production of a group of glass preforms and optical elements - Google Patents

Abstract

Even when the average mass of the preforms constituting the preform group to be obtained is small, there is provided a glass preform group for precision press molding with a small variation in volume between the preforms and a small mass tolerance.

It is a glass preform group which consists of several glass preforms provided for precision press molding, The ratio of the mass tolerance of the glass preform with respect to the average mass (M _AV ) of the glass preform is less than +/- 0.5 [%] X M _AV . It is a glass preform group characterized by the above-mentioned.

Preform Group, Average Mass, Mass Tolerance, Volume Variation, Glass Preform

Description

A method of manufacturing a preform group made of glass, a preform group made of glass, and a method of manufacturing an optical element {A GROUP OF GLASS PREFORMS AND PROCESSES FOR THE PRODUCTION OF A GROUP OF GLASS PREFORMS AND OPTICAL ELEMENTS}

TECHNICAL FIELD This invention relates to the manufacturing method of the glass preform group, the glass preform group, and the manufacturing method of an optical element.

As a technique for producing glass optical elements such as aspherical lenses with high precision, a precision press molding method is known. This method, also called a mold optics molding method, uses a press molding die having a precisely processed molding surface to press-form the heated glass preform, to shape the entire optical element, and to precisely glass the molding surface. Is transferred to the optical functional surface (see Patent Document 1, for example).

Moreover, the glass preform used for manufacturing the said optical element, for example, flows out molten glass, isolate | separates the molten glass mass of desired mass, and shape | molds to a preform in the process of cooling this glass mass. It can produce by (for example, refer patent document 2).

[Patent Document 1] Japanese Patent Application Laid-Open No. 10-316448

[Patent Document 2] Japanese Patent Application Laid-Open No. 2002-121032

In recent years, the demand of the small apparatus which incorporates an imaging device, such as a mobile telephone with a camera, is increasing. The imaging optical system incorporated in such an imaging device is constituted by a very small lens, and in order to precisely positionally fix each lens, each lens preferably has a positioning reference plane. For example, as the positioning reference plane for precisely determining the distance between the lenses, a flat portion provided on the outer periphery of the lens plane can be used, and the lens side surface can be used as the positioning reference plane for aligning the optical axes of the lenses. In the precision press molding method, by transferring the molding surface of the mold to the glass, not only the optical functional surface but also the positional relationship and angle between the surfaces to be formed can be precisely defined, so that the optical functional surface and the positioning reference plane are collectively formed. can do.

By utilizing the characteristics of precision press molding as described above, an ultra-compact optical element can be efficiently produced. On the other hand, if the volume of the preform is not precisely managed, the following problems arise.

First, when the volume of the preform is larger than the volume of the space formed in the state in which the press forming mold having the upper mold, the lower mold, and the trunk mold is closed, the upper mold and the trunk thread are formed between the molds constituting the press mold. In addition, it is protruded between the lower mold and the body mold, and becomes a molding burr, which damages the sliding mobility of the mold and causes the production to stop, or the press molding die. On the other hand, when the volume of the preform is smaller than the volume of the space formed in the state of closing the press-molding die, the filling of the glass into the space is insufficient, so that the surface precision of the optical functional surface is lowered or the glass positioning reference plane is to be used. The glass does not reach the part to be made, and the positioning reference plane is not formed.

Therefore, in order to collectively form the optical function surface and the positioning reference plane, it is expected to use a preform having high volume accuracy, that is, high mass accuracy.

As described above, as a method for producing a glass preform with high productivity, there is a method of flowing molten glass out of a nozzle, separating a molten glass mass of a desired mass, and molding the glass mass into a preform while the glass mass is cooled. When the preform is produced using this method, the optical element can be mass-produced based on very high productivity, starting from melting of the glass. However, in the conventional production method of glass preforms, there is a slight variation in the volume of the preforms, and it is not always possible to satisfy the volume accuracy, that is, the mass precision, for use in the above-mentioned precision press molding. This problem was particularly noticeable when producing lightweight preforms.

The present invention relates to a glass preform group for precision press molding in which the volume variation between the respective preforms is controlled to the maximum, and a method for producing the preform group based on very high productivity from molten glass. Another object is to provide a method for producing an optical element from a preform constituting the preform group obtained by the above method.

In order to improve the mass precision of the preform, the present inventors have repeatedly studied, and have come to obtain the following knowledge.

(a) The mass of the molten glass product of the preform base material obtained by dropping the molten glass from the outlet of the nozzle generally has a downward acceleration acting on the glass falling vertically to the nozzle outlet, the outer diameter of the nozzle lower end portion, and the molten glass. Although it is determined by the surface tension and the like, when the ratio of the mass tolerance to the target preform mass is made small, it is not possible to suppress the fluctuation of the mass only by keeping the various conditions constant.

(b) The variation of the mass is considered to be due to the fact that the molten glass leaks to the outlet of the nozzle upon dropping of the molten glass drop, and that the amount of the molten glass drop slightly changes depending on the amount of the rising amount.

(c) When the nozzle is observed in detail, the tip is slightly vibrated, but this slight vibration causes variation in the amount of dripping of the molten glass.

(d) In addition, the wettability of the nozzle outer circumferential surface with respect to the glass is slightly changed by temperature change and humidity change in the nozzle outlet atmosphere, and this slight change causes variation in the amount of dripping of the molten glass.

Based on these findings, the present inventors reviewed again and found that the molten glass flowing out was sequentially dropped at a constant flow rate and molded from the outlet having controlled dust temperature and / or atmosphere temperature and humidity, thereby forming a volume between the respective preforms. The glass preform group by which the fluctuation | variation of the glass is controlled as much as possible is found, and this invention is completed based on this knowledge.

That is, the present invention,

(1) a glass preform group consisting of a plurality of glass preforms to be used for precision press molding,

A glass preform group, wherein the ratio of the mass tolerance of the glass preform to the average mass (M _AV ) of the glass preform is within ± 0.5 [%] × M _AV ,

(2) The glass preform group according to the above (1), wherein the entire surface is made of a spherical glass preform formed by solidifying glass in a molten state;

(3) It is a manufacturing method of the glass preform group which consists of several glass preforms used for precision press molding,

The molten glass which flows out at a fixed flow volume is dripped sequentially from the outlet which controlled dust temperature and / or atmosphere temperature and humidity, and shape | molded, The manufacturing method of the glass preform group characterized by the above-mentioned.

(4) The manufacturing method of the glass preform group as described in said (3) which performs the shaping | molding after the said molten glass dropping by applying a wind pressure to the obtained molten glass drop, and making it float,

(5) Precision press-molding by heating the glass preform group which comprises the glass preform group as described in said (1) or (2), or the glass preform group obtained by the method as described in said (3) or (4) A method for producing an optical element, and

(6) Precision press molding is performed by transferring each molding surface of the press molding mold which has an upper mold | type, a lower mold | type, and a trunk shape to glass,

The surface formed by transferring the forming surface of the upper mold and the surface formed by transferring the forming surface of the body mold and / or the surface formed by transferring the forming surface of the lower mold and the surface formed by transferring the molding surface of the lower mold. It is providing the manufacturing method of the optical element as described in said (5) which makes this precision press molding using this edge | corner as a free surface.

According to the present invention, a glass preform group for precision press molding in which the volume variation between each preform is controlled to the maximum, a method for producing the preform group from molten glass on the basis of very high productivity, the preform group or the method The method of manufacturing an optical element from the preform which comprises the obtained preform group can be provided.

[Preform group made of glass]

First, the glass preform group of this invention is demonstrated.

The glass preform group of this invention is a glass preform group which consists of several glass preforms provided for precision press molding, and the ratio of the mass tolerance of glass preforms to the average mass (M _AV ) of glass preforms is ± It is characterized by being within 0.5 [%] x M _AV .

In the present invention, the glass preform group means a collection of a plurality of glass preforms which are made of glass of the same kind and which are provided in precision press molding having both a shape and a mass. In addition, in this invention, the preform group made from glass does not necessarily need to consist only of the preform lot manufactured collectively in the same apparatus in the same apparatus, and may be comprised by the some preform lot. For example, about the preform group which consists of 1000 preforms, you may think that it consists of ten lots which consist of 100 preforms, and you may think that it consists of 100 lots which consist of ten preforms.

As for the number of the preforms which comprise a preform group, 1000 or more are preferable, 2000 or more are more preferable, 5000 or more are more preferable. What is necessary is just to determine the upper limit of number by the required number of optical elements.

M _AV means the malleable average of the glass preforms constituting the preform group. For example, when the glass preform is a preform for a micro lens used in an imaging device of a mobile telephone or the like, M _AV is 1 mg to 200 Mg, preferably 5 to 200 mg, more preferably about 8 to 160 mg.

The glass preform group of the present invention, the ratio of the mass tolerance of the glass preform for the _AV ± M is less than 0.5 [%] × M _AV.

The ratio of the mass tolerance of the glass preform to the average mass M _AV of the glass preform is preferably within ± 0.4 [%] × M _AV , more preferably within ± 0.38 [%] × M _AV . .

When the number of preforms constituting the preform group is 500 or more, the ratio of the average mass (M _AV ) of the preform and the mass tolerance of the preform to the M _AV is sufficient to be verified by 500 preforms arbitrarily extracted from the preform group.

As described above, small optical elements and the like embedded in mobile devices such as mobile phones are expected to be formed by forming the optical functional surface and the positioning reference plane by thorough press molding of the preform so as to enable accurate alignment and assembly. The preforms constituting the preform group provided for the above-mentioned precision press molding are required to be lightweight and have a small mass tolerance. By the way, in the case where the average mass of the preform (M _AV) is large, the average weight of the is relatively easy, but the preform to inhibit decrease the rate of mass tolerance of the preform [mass tolerance / mean mass (M _AV)] for the M _AV ( If M _AV) is small, since even slight weight variations of, M ratio [mass tolerance / mean mass (M _AV)] of a mass tolerance of the preform for the _AV is larger, conventional, light weight, and the preforms having high weight accuracy It was difficult to provide a preform group. On the other hand, in the glass preform group of the present invention, since the ratio of the mass tolerance of the glass preform to the average mass (M _AV ) of the glass preform is within ± 0.5 [%] × M _AV , even when it is super light, The preform group which consists of the preform with precision can be provided.

It is preferable that the glass preform group of this invention consists of the spherical glass preform which the whole surface formed by solidifying the glass of a molten state.

By making the whole surface of a preform into the surface which solidified the glass of molten state, the whole surface can be made into a free surface and the latent flaw of a surface can be eliminated. As a result, each obtained preform can improve weather resistance more than an abrasive preform. If the weather resistance is not high enough, the deterioration layer, which is a burnt part, may be exposed on the surface of the preform. If the deterioration layer is removed, the mass of the preform decreases slightly, thereby degrading the mass precision. According to this state, since the whole surface of a preform is formed by solidifying the glass of a molten state, the latent flaw of a surface can be eliminated and the said problem can be eliminated.

If the shape of the preform is spherical, if the glass being used is the same type, the diameter also increases and decreases with the increase and decrease of the preform mass, and the mass and diameter of each preform correspond one-to-one. Therefore, if the variation of the diameter of the preform is managed, the mass precision of the preform can be managed. When the preform is precisely press molded to obtain a small optical element, when the spherical preform is used, if the lower mold face is concave, the preform can be stably disposed at the center of the face.

The glass preform group of this invention can be manufactured suitably by the manufacturing method of the glass preform group of this invention demonstrated below.

[Manufacturing method of preform group made of glass]

Next, the manufacturing method of the glass preform group of this invention is demonstrated.

The manufacturing method of the glass preform group of this invention is a manufacturing method of the glass preform group which consists of several glass preforms provided for precision press molding, It is dustproof and / or atmosphere of the molten glass which flows out at a fixed flow volume. It is characterized by dropping in sequence from the outlet which controlled temperature and humidity, and shape | molding.

EMBODIMENT OF THE INVENTION Hereinafter, the preferable form in the manufacturing method of the glass preform group of this invention is demonstrated based on drawing.

As shown in FIG. 1, in order to produce a preform group, the molten glass obtained by heating, melting, clarifying, and homogenizing a glass raw material is guide | induced to the nozzle 2 provided in the lower end of the pipe 1. As shown in FIG. The molten glass flows out from the outlet formed at the lower end of the nozzle 2, but controls the temperature of the pipe 1 and the nozzle 2 so that the glass outflow amount per unit time is constant.

The molten glass discharged from the outlet port is vertically lowered to the lower end of the nozzle 2 by the surface tension. The molten glass falls from the lower end of the nozzle 2 when the downward force acting on the glass that falls vertically lower than the force to stop the molten glass at the lower end of the nozzle 2. Here, since the outflow amount of glass per unit time is made constant, the fall of the molten glass occurs at a constant cycle. The total mass of the falling molten glass product is obtained by multiplying the cycle by the amount of glass outflow per unit time expressed in mass.

In this way, the mass of the molten glass product is determined by the balance of the force at which the molten glass stops at the lower end of the nozzle 2 and the downward force acting on the glass which vertically descends, but as described above, the nozzle is observed in detail. When the outlet portion of the tip is slightly vibrated, the slight vibration causes fluctuations in the amount of dripping of the molten glass. For this reason, it is possible to make the mass tolerance between preforms small by performing a dustproof measure and dripping to the nozzle 2.

Specifically, as shown in FIG. 2, the glass melting apparatus 10 including the container which connects to the nozzle 2 through the pipe 1, and accumulates molten glass is mounted on the dustproof table 11, The pipe 1 and the nozzle 2 are suspended from the container. In this way, the vibration from the dried material can be prevented from being transmitted to the nozzle 2 through the glass melting apparatus 10 and the pipe 1, and the vibration of the nozzle 2 can be suppressed. Alternatively, an anti-vibration mechanism may be provided between the structure supporting the glass melting apparatus and the dried product to block the propagation of vibration.

The glass melting apparatus 10 may have a means for heating molten glass in the container, a means for warming the container, a stirring means for homogenizing the molten glass in the container, and the pipe 1 may be, for example. You may have the electrode for energization heating, the heat retention means for heat-retaining a pipe, etc.

In the method of this invention, molten glass is dripped sequentially by controlling the temperature and humidity of an outlet atmosphere with or without the said dustproof measure.

As described above, the wettability of the nozzle outer circumferential surface with respect to the glass is slightly changed in accordance with the temperature change and the humidity change in the nozzle outlet atmosphere, and since this slight change causes variation in the amount of dripping of the molten glass, the nozzle 2 By controlling the temperature and humidity of the atmosphere in the vicinity of the outlet of the ()), it becomes possible to reduce the mass tolerance between the preforms.

Specifically, as shown in FIG. 2, a booth (heat chamber) 12 is provided below the glass melting apparatus 10, and a pipe connected to the glass melting apparatus 10 in the booth 12 ( 1) and the nozzle 2 are accommodated, and the shaping | molding die 13 mentioned later is provided in this booth 12. As shown in FIG. In the continuous production of preforms using a plurality of shaping dies, a plurality of shaping dies, a turntable for loading them, and a driving device for indexing and rotating the turntables are provided in the booth 12, and the dropping and melting of the molten glass are carried out. The molding from to the preform is performed in the booth.

And the temperature and humidity in this booth are kept constant in a required state by the temperature control apparatus and humidity control apparatus (henceforth a temperature humidity regulator) which are not shown in figure. By this operation, the temperature and humidity of the atmosphere around the outlet of the nozzle 2 are controlled. The temperature and humidity regulator has sensors of temperature and humidity, and feeds back the results detected by the sensor to maintain the atmosphere in the booth 12 at the set temperature and the set humidity. For example, when drying in winter, humidification is performed so as not to have excessive low humidity, or in a humid state such as rainy season, so as not to have excessive high humidity. The temperature is also controlled so that the temperature in the booth 12 does not deviate from the set temperature with respect to the fluctuation of the outside air temperature. In this way, the amount of leakage of the glass to the outer periphery of the nozzle 2 can be controlled to be constant, whereby the mass tolerance between the obtained preforms can be reduced.

In the method of the present invention, the dropping of the molten glass refers to the nozzle outlet and the molten glass after the lump of molten glass falls from the nozzle outlet and the tip of the molten glass flow reaches the bottom surface of the mold receiving the molten glass. The thread-shaped portions formed between the ends of the flow are broken, and dropping and separation are included.

Then, as the method of separating the molten glass product after the tip of the molten glass flow reaches the bottom face of the shaping die, as shown in Fig. 1, the vertical lowering to the lower end (near the outlet port) of the nozzle 2 is performed. It is preferable to perform the said dropping in the state which covered the circumference | surroundings of the molten glass with the cover 5 in order to keep the mass of a molten glass enemy constant. It is preferable that the cover 5 is a hollow cylindrical shape, and it is installed so that the fall path of a molten glass enemy may not be blocked as shown in FIG. And in order to weaken the upward airflow by the convection which arises at the front-end | tip of a nozzle, it is preferable to block the upper part of the cover 5. By this structure, the position where a molten glass breaks | stains can be stabilized, and the mass variation of a glass product can be made smaller.

However, the main factor in determining the short and long (長短) of the threaded part is the content of SiO ₂ in the glass, the content of SiO ₂ increases, (e. G., More than 20% by weight) is a threaded portion long, SiO ₂ When content of becomes small (for example, 20 mass% or less), a thread part becomes short. In the glass forming the long filamentous portion having a high content of SiO ₂ , the filamentous portion is likely to be broken by the impact when the tip of the molten glass flow reaches the bottom face of the mold. Dropping efficiency is improved.

Therefore, it is preferable to make the distance of the shaping | molding surface which receives the molten glass which fell, and the distance of a nozzle tip constant, and to perform dripping of molten glass in a fixed period. With such a configuration, the timing of impact generation when the length of the threaded portion and the tip of the molten glass flow reaches the shaping bottom of the mold can be stabilized for each drop, and the mass variation of the glass product can be reduced.

If the cover 5 covers the periphery of the lower end (outlet) of the nozzle 2, it does not necessarily need to cover the whole dripping path | route of the molten glass enemy, and the length of the cover 5 is from the lower end (outlet) of the nozzle 2 from the end. It is preferable to set it as the length which covers the part corresponding to 1/5-4/5 of the distance to the shaping | molding bottom of a shaping | molding die, and 3 / of the distance from the lower end (outlet) of the nozzle 2 to the shaping bottom of a shaping | molding die It is more preferable to set it as the length which covers the part corresponded to 10-7 / 10.

When the cover 5 has a hollow cylindrical shape, if its diameter is too large, the workability is lowered, and the atmosphere in the cover 5 is difficult to stabilize. If the cover 5 is too small, the molten glass that flows out is applied to the surface of the cover 5. It may adhere or may contact with the nozzle 2, the pipe 1, etc. In addition, as will be described later, when wind pressure is applied to the molten glass vertically descending at the lower end of the nozzle 2 to prompt the drop, if the aperture is too small, it becomes difficult to create a stable air flow around the nozzle. The diameter of the cover 5 is appropriately set in consideration of the above point so that the mass tolerance becomes small.

The cover 5 has a function of slowing down the cooling speed of the molten glass which is vertically lowered to the lower end of the nozzle 2. In other words, the molten glass vertically lowered by the cover 5 is kept warm, and the rate of increase in viscosity of the glass is slowed down, the viscosity of the threaded portion is maintained in a range suitable for separation, and the viscosity of the glass is also suitable for spheroidization of the glass. You can do

In addition, it is preferable that the cover 5 is made of an insulator, and as shown in FIG. 1, the high frequency coil 6 is arranged around the cover to flow a high frequency current, and the nozzle is subjected to high frequency induction heating. By this structure, the nozzle 5 made of platinum or a platinum alloy can be inductively heated without induction heating of the cover 5, and the temperature of the nozzle 2 is maintained so that the desired flow rate is maintained without losing the transparency of the glass. Can be controlled.

It is preferable to provide the gas flow path forming cover 3 at the lower end of the pipe 1 and the outer periphery of the nozzle 2 as shown in FIG. By providing the gas flow path forming cover 3, the gas flow path 4 can be formed in the space between the pipe 1 and the nozzle 2 and the gas flow path forming cover 3. An opening 3-1 is formed at the lower end of the gas flow path forming cover 3, and the tip of the nozzle 2 is protruded from the opening. The gas flow path forming cover 3 and the gas flow path forming cover openings 3-1 are preferably arranged coaxially around the central axis of the nozzle 2, respectively. In addition, it is preferable that the gas discharged from the gas opening forming cover opening 3-1 flows evenly around the central axis.

The dropping of the molten glass occurs when the gravity of the molten glass acts on the molten glass which is vertically lowered than the force to stop at the lower end of the nozzle. We cannot lose and cannot drop lighter glass enemy. On the other hand, when the gas is continuously ejected downward at a constant flow rate downward from the gas flow path forming cover opening 3-1 by the above method, the molten glass that is vertically lowered receives a downward force due to the wind pressure caused by the gas. As a result, a lighter glass enemy can be obtained. When the gas flow rate is controlled by the mass flow controller or the like so that the gas flow rate is constant, the mass of the glass product can be stabilized.

It is preferable to perform shaping | molding after the said molten glass dropping, adding a wind pressure to the obtained molten glass red, and making it float.

Below the nozzle, the shaping | molding die 13 which has a recess cross section as shown in FIG. 3 is carried in, and receives the glass drop 14 dropping at a predetermined period from a nozzle in the said recess, and rolls or slips in a recess. It introduce | transduces so that it may introduce | transduce, and it shape | molds in the spherical shape, moving up and down the glass enemy 14 in a recess with the gas which blows upward from the gas ejection opening formed in the recess bottom part, and obtains a preform. Mass production of a preform prepares several shaping | molding dies 13, and carries in shaping | molding die under a nozzle one by one, receives the glass red 14, and takes out the shaping | molding die 13 which received the glass red 14 from the nozzle down. And it is preferable to carry out by the method of carrying in the empty shaping | molding die 13 below a nozzle. While the shaping | molding die 13 moves, shaping | molding the glass red 14 to a preform in a recessed part, cooling to the temperature range which a preform does not deform | transform, and taking out a preform from the shaping | molding die 13, an empty shaping | molding die It is carried in under the nozzle again. By sequentially performing such a step for each of a plurality of molding dies, it is possible to mass produce a preform and obtain a preform group.

As described above, according to the method of the present invention, it is possible to suppress the fluctuation of the nozzle outlet port and the glass leakage amount, which is the cause of the mass variation of the preform, and to produce a preform group having a small mass tolerance between the preforms. .

[Method for Manufacturing Optical Element]

Next, the manufacturing method of the optical element of this invention is demonstrated.

The manufacturing method of the optical element of this invention heats the preform which comprises the glass preform group of this invention, or the glass preform group obtained by the manufacturing method of the glass preform group of this invention, and performs precision press molding, It is characterized by the above-mentioned. It is.

Precise press molding is a method of heating and pressing preforms using a press molding die including an upper die, a lower die, and a body die to transfer and form the shape of the press forming die into a glass accurately. The production method of each mold such as the upper mold, the lower mold, the trunk mold, and the like, the material thereof, the release film formed on the upper mold and the mold of the lower mold, the method of forming the mold, and the kind of the atmosphere for performing the precision press molding are known. do.

As an example of the precision press molding method, as shown in FIG. 4, the spherical preform 19 is disposed in the center of the molding surface of the concave lower mold 16 inserted into the barrel mold 15, and the lower mold 16 is provided. The upper die 17 is inserted into the barrel die 15 so that the molded face faces the molded face of the die. In this state, the preform 19 and the press-molding die (body mold 15, lower mold 16, upper mold 17) are heated together, and the temperature of the glass constituting the preform 19 is, for example, When it rises to the temperature which shows the viscosity of 10 <^6> dPa * s, the push rod 18 is dropped and the preform 19 is pressurized by the upper mold | type 17 and the lower mold | type 16. FIG. The pressurized preform 19 can be spread out in a space (called a cavity) surrounded by the upper mold 17, the lower mold 16, and the body mold 15. In this way, the glass preform 19 is pressed and the glass is filled in the sealed space formed in the state which closed the press-molding die.

The angle formed by the relative position of each forming surface of the upper mold | type 17, the lower mold | type 16, and the trunk | drum 15 in a mold closed state, and a surface normal line is formed precisely beforehand. When the above molding is performed using such a press-molding die, the optical functional surface and the positioning reference plane can be formed with high precision positional relationship and angle to each other.

In the case of forming the lens as an example, the center portion of the image forming surface is a portion for transferring molding the lens surface, which is the optical functional surface of the lens, and the peripheral portion of the image forming surface is a portion for transferring the flange-shaped flat portion to a ring shape. do. Similarly with respect to the lower mold-forming surface, the center of the molding surface is a portion for transferring the lens surface, and the peripheral portion of the molding surface is a portion for transferring the flange-shaped flat portion to a ring shape. By the end of the press molding, the upper and lower dies are kept facing each other and the central axes of the upper and lower dies are kept accurate.

The inner surface of the cylindrical through hole is transferred to the glass by filling the glass into the sealed space formed in the state in which the press-molding die is closed. By forming the angle between the central axis of the cylindrical through hole and the inner surface of the through hole precisely, and maintaining the central axis of the through hole and the vertical center axis precisely until the end of press molding, for example, as shown in FIG. As described above, two lens surfaces 20 and 21, two flanged flat portions 22 and 23 and an inner surface of the body shape are formed by transferring the edges (sides of the flanged flat portions 22 and 23) 24 It is possible to precisely form a lens having a) and at the same time to accurately form the relative position of each of the parts or the angle formed by each surface.

The optical element obtained by the method of this invention has a positioning reference plane other than an optical function surface. For example, the positioning reference planes of the lenses serve as reference planes for precisely matching the reference planes for determining the distance between the lenses and the optical axes of the lenses, and by contacting these reference planes with the holder, each lens can be accurately aligned. In the above example, one of the flange-like flat portions 22 and 23 is used as the first positioning reference plane, and the reference plane is brought into contact with the holder, whereby the distance between the lenses can be accurately positioned. It is preferable to apply the pressure for maintaining the said contact state to the other flange type flat surface, and to maintain the fixed state to the holder of a lens. In addition, the edge 24 is used as a reference surface for accurately matching the optical axis of the lens with the second positioning reference plane.

In the optical element, at least two or more surfaces, specifically, two or three positioning reference planes are preferably formed by precision press molding. Preferably, the positioning reference planes of the two or three surfaces are formed to be non-parallel to each other. When the optical elements are positioned using two reference planes which are not parallel to each other in this way, the positioning and direction of the optical elements in the optical system can be accurately determined. An optical element having rotational symmetry such as a lens only needs to have two positioning reference planes. In the case of an optical element without rotational symmetry such as a prism, by forming three positioning reference planes, the positioning in the optical system and the direction at the position can be accurately determined.

The upper and lower mold faces are provided with a release film for the purpose of improving the release property of the glass.However, it is difficult to install a mold release film with a uniform thickness on the inner surface of the barrel (the upper face and the inner face of the through hole into which the lower mold is inserted). Usually, no release film is provided on the molding surface to be transferred. Therefore, in order to prevent the glass from being fused to the inner surface of the cylindrical body during press molding, it is preferable to make the area of the edge 24 small in a range where the glass does not break, and to minimize the contact area between the glass and the cylindrical body. Do. By the way, when precisely press-molding a lens with a thin edge thickness (distance between the flanged flat portions 22 and 23), the glass can be filled from the portion that becomes the lens surface, and gradually widen in the body direction, but at this time Since the volume of the space between the upper mold face and the lower mold face for transferring the two flanged flat portions 22 and 23 is small, if the amount of glass constituting the preform is small, the glass is empty from the space. If it pulls out and a shaping | molding burr arises and the quantity of the said glass is small, even if it is few, the glass will not reach a sleeve-type even if it presses, and the edge used as a positioning reference surface will not be formed. That is, in the preform for molding the optical element, only a very small amount is allowed in the overall mass, but in the method of the present invention, the mass of the preform obtained with respect to the mass of the desired lens is precisely determined. Therefore, even when the edge thickness is thin, the inner surface of the body can be transferred to form an edge which functions as a positioning reference plane, so that a forming burr is generated and does not stop the mass production process of the optical element.

In the method of the present invention, the surface formed by transferring the forming surface of the upper mold and the surface formed by transferring the corner forming surface and / or the forming surface of the lower mold and the surface forming the lower mold and the body forming It is preferable to precisely press-mold a glass preform using the corner formed by the surface formed by transferring the surface as a free surface.

As described above, if the edge and the flange-like flat portion are formed precisely, there is no risk of disturbing the positioning function. For example, in the lens shown in Fig. 5, the edge 25 or the edge 26 is sharp. If this is done, the edge may be broken when being inserted into the holder, or the edge may shave the holder, which may cause oscillation. When dust adheres to the light-receiving surface of the imaging element, the image quality is greatly reduced. Therefore, it is preferable to prevent such troubles and to form an optical element having an edge formed of a free surface. Further, by making the corners a free surface, even when a slight mass tolerance occurs between the preforms, the corner portion plays a role of volume adjustment, thereby making it possible to avoid the occurrence of problems such as occurrence of molded burrs and insufficient filling of glass. do.

In the optical element thus produced, an optical multilayer film such as an antireflection film may be formed as necessary.

<Examples>

Hereinafter, although an Example demonstrates this invention further in detail, this invention does not limit anything by these examples.

Example 1 (Preparation Example of Preform Group Made of Glass)

First, the glass raw material was weighed and combined, and it fully stirred, and introduce | transduced into a melting container, heating, melt | melting, clarification, and stirring so that the optical glass which has an optical glass with desired optical characteristic and glass transition temperature was prepared, and homogeneous molten glass was prepared. The glass is to a _{B 2 O 3, SiO 2,} BaO, and containing Li ₂ O, the refractive index (nd) of 1.58313, an Abbe number (υd) is 59.46.

Using the apparatus shown in Fig. 1, 3000 pieces of glass preforms having a target mass of 100 mg were produced from the molten glass.

Here, the glass melting apparatus containing a melting container is mounted on the dustproof stand. The dustproof zone is provided with an opening through which the pipe 1 for flowing the glass flows, and has a structure in which the pipe 1 is suspended from the container through the opening, and molten glass flows out at the lower end of the pipe 1. The nozzle 2 is attached. The structure prevents the vibration from the dry matter in which these facilities were installed by the dustproof stand, and prevents it from being transmitted to the nozzle 2.

Molding dies are arranged below the nozzles 2, and the lower end portion of the pipe 1, the nozzles 2 and the molding dies have an internal atmosphere having a temperature of 25 ° C. and a relative humidity of 10 to 95% by air conditioners. Lies in a controlled booth. The above structure makes it possible to control the temperature and humidity near the molten glass outlet formed at the lower end of the nozzle 2 to constantly control the wettability of the molten glass on the nozzle outer peripheral surface.

Through the pipe 1 connected to the melting vessel bottom part, the molten glass flows out from the nozzle 2 attached to the lower end of the pipe 1 at a fixed flow rate. The nozzle 2, the pipe 1, and the melting vessel are each temperature controlled so that the glass does not lose transparency and the desired flow rate is obtained.

On the lower end of the pipe 1 and the outer periphery of the nozzle 2, a gas flow path forming cover 3 is formed, as shown in FIG. 1, and the pipe 1 and the nozzle 2 and the gas flow path forming cover ( The gas flow path 4 is formed in the space between 3). An opening 3-1 is formed at the lower end of the gas flow path forming cover 3, and the tip of the nozzle 2 is projected from the opening. It is preferable that the nozzle 2, the gas flow path forming cover 3, and the gas flow path forming cover openings 3-1 be symmetrically disposed coaxially around the central axis of the nozzle 2, respectively. It is also preferable that the gas discharged from the gas flow path forming cover opening 3-1 flows evenly around the central axis.

In this embodiment, the inner diameter of the pipe 1, the inner and outer diameters of the nozzle 2, and the temperature of the pipe 1 and the nozzle 2 are adjusted so that the molten glass descending at the lower end of the nozzle 2 falls at regular intervals. It adjusts and the outflow amount of glass is controlled. The molten glass flowing out from the outlet of the nozzle 2 descends vertically at the lower end of the nozzle. However, the gas continuously ejected downward from the gas flow path forming cover opening 3-1 is sprayed on the vertically molten glass. The downward wind pressure is applied, and a lighter glass enemy can be obtained. When the gas flow rate is controlled by the mass flow controller or the like so that the gas flow rate is constant, the mass of the glass product can be stabilized.

As shown in Fig. 1, a cover 5 is attached to the periphery of the nozzle 2 and the cover for forming the gas flow path. The cover 5 covers a part corresponding to 1/3 to 1/2 of the distance from the lower end (outlet) of the nozzle 2 to the bottom of the receiving die of the molding die described later, and the upper part of the cover 5 It is blocked. However, the downward direction which does not block the dripping path | route of a molten glass is open | released. The cover 5 reduces the disturbance caused by the external atmosphere, for example, the rising air flow around the nozzle, thereby creating a stable atmosphere in the cover 5, and the gas opening forming cover opening 3-1. The gas ejected from the gas can also be stabilized and flow downward.

The high frequency induction coil 6 is disposed outside the cover 5, a high frequency current flows, and the nozzle 2 is subjected to high frequency induction heating. The cover 5 is preferably made of a heat resistant insulator in advance so as not to be inductively heated, but quartz glass or the like is suitable as the insulator. When the cover 5 is made of a transparent heat resistant insulator, the inside of the cover 5 can be observed from the outside.

The falling molten glass is received in a mold for waiting under the nozzle. In order to stabilize the mass of the glass enemy, the mold is waited so that the distance between the bottom of the molten glass of the shaping mold and the bottom of the nozzle is constant, the bottom of the falling molten glass is received, and the molten glass reaches the bottom of the shaping glass. The glass is detached in the threaded portion by the impact when it is made. 3 shows a vertical sectional view of the mold. The molten glass product 14 is received by the receiving surface 13-1 of the shaping | molding die 13. Since the receiving surface 13-1 is inclined in the bottom direction of the recess 13-2 formed on the upper surface of the shaping die 13, the molten glass enemy 14 is recessed from the receiving surface 13-1. -2) slide into (roll in);

As shown in Fig. 3, the cross section of the recess 13-2 has a shape spreading from the bottom to the trumpet shape, and at the bottom of the recess 13-2, there is one gas outlet for ejecting gas upwards. Formed. The molten glass enemy 14 introduced into the recess 13-2 descends while rolling the recess inner wall toward the bottom of the recess, but decreases as the inner diameter of the recess decreases. The lower the pressure, the stronger the wind pressure. As a result, the glass drop 14 rises in the recess 13-2. However, if the glass drop 14 rises, the upward wind pressure is weakened, and thus the glass drop 14 falls along the inner wall of the recess again. In this manner, the glass enemy 14 repeatedly performs the movement of descending while moving up and down the inside of the recess in a short time. Since the direction in which the molten glass enemy rolls the concave inner wall is random, the glass enemy 14 cools while spheroidizing during the above motion, and is formed into a spherical preform. When the preform is cooled to a temperature at which the preform is not deformed, the preform in the recess 13-2 is taken out and cooled to room temperature at a speed at which the glass does not break.

By repeating the above steps using a plurality of molding dies, an equivalent mass spherical preform can be mass produced. In this way, the preform group which consists of 3000 spherical preforms made from spherical optical glasses whose average mass (M _AV ) is 100.16 mg and whose ratio of mass tolerance is within ± 0.21 [%] x M _AV was obtained. In addition, the ratio of the said average mass ( _MAV ) and a mass tolerance is the value which was taken out and calculated | required 500 pieces from the obtained several preform.

Example 2 (Preparation Example of Preform Group Made of Glass)

Example 1 except that optical glass containing B ₂ O ₃ , SiO ₂ , La ₂ O ₃ , ZnO, CaO, Li ₂ O, and having an index of refraction (nd) of 1.69350 and Abbe number (υd) of 53.20 was used. Similarly, the preform group was produced and the preform group which consists of 3000 spherical optical glass preforms whose average mass (M _AV ) is 99.88 mg and whose ratio of mass tolerance is within ± 0.27 [%] x M _AV was obtained. .

In addition, the ratio of the said average mass ( _MAV ) and a mass tolerance is the value which was taken out and calculated | required 500 pieces from the obtained several preform.

Example 3 (Preparation Example of Preform Group Made of Glass)

Except for using optical glass containing P ₂ O ₅ , Nb ₂ O ₅ , TiO ₂ , BaO, Li ₂ O, and having a refractive index (nd) of 1.82114 and an Abbe number (υd) of 24.06, as in Example 1 The preform group was produced and the preform group which consists of 3000 spherical preforms made from spherical optical glasses whose average mass (M _AV ) is 99.81 mg, and the ratio of mass tolerance is within ± 0.31 [%] x M _AV was obtained.

In addition, the ratio of the said average mass ( _MAV ) and a mass tolerance is the value which was taken out and calculated | required 500 pieces from the obtained several preform.

Example 4 (Preparation Example of Preform Group Made of Glass)

Except not controlling the temperature and humidity of the lower end (outlet) of the nozzle 2, the preform group was produced like Example 1 thru | or 3, and the average mass M _AV is 100.25 mg, and the ratio of mass tolerance Plural preform groups consisting of 3000 spherical preforms made of spherical optical glass within ± 0.43 [%] × M _AV were obtained.

In addition, the ratio of the said average mass ( _MAV ) and a mass tolerance is the value which extracted 500 pieces from each of the obtained several preform group, and calculated | required it.

Example 5 (Preparation Example of Preform Group Made of Glass)

Except not providing a dustproof stand, preform groups were produced in the same manner as in Examples 1 to 3, and all had an average mass (M _AV ) of 100.38 mg, and the ratio of the mass tolerance was within ± 0.47 [%] × M _AV . And the several preform group which consists of 3000 spherical preforms made from spherical optical glasses.

In addition, the ratio of the said average mass ( _MAV ) and a mass tolerance is the value which extracted 500 pieces from each of the obtained several preform group, and calculated | required it.

Comparative Example 1 (Preparation Example of Preform Group Made of Glass)

The preform group was produced in the same manner as in Examples 1 to 3 except that the temperature and humidity of the lower end (outlet) of the nozzle 2 were not controlled and the dustproof stand was not provided, and the average mass M _AV was 100.74. Mg, and a plurality of preform groups consisting of 3000 spherical preforms made of spherical optical glasses having a ratio of mass tolerance within ± 0.79 [%] × M _AV were obtained.

In addition, the ratio of the said average mass ( _MAV ) and a mass tolerance is the value calculated | required and extracted 500 pieces from each obtained preform group, respectively.

Example 6 (Example of Manufacturing Optical Element)

Using each preform group obtained in Examples 1 to 5, a small aspherical lens having a cross-sectional shape shown in FIG. 5 was produced by precision press molding, respectively. In either case, the lens was also intact and had sufficient optical performance as the lens. The edges 24 and the flanged flat portion 22 of each lens are formed by transferring the molding surface of the press molding type, and the corners 25 at which the edge 24 and the flanged flat portion 22 cross each other have a rounded shape. Free surface was taken. No occurrence of molded burrs was observed in each lens.

These aspherical lenses function as lenses constituting the imaging optical system of the imaging device incorporated in the mobile telephone. The lens obtained in this way and a lens having an edge and a flange-like flat portion as a positioning reference plane produced in exactly the same manner except for the shape are built in the lens holder, and the respective positioning reference planes are fixed in contact with the holder. It could be arranged exactly in the holder.

By contrasting Examples 1 to 5 and Comparative Example 1, even when the average mass of the preforms constituting the preform group obtained by dust-proofing the outlet of the molten glass and / or controlling the atmosphere temperature and humidity is as small as about 100 mg, It turns out that the mass tolerance between preforms can be made small. In addition, it can be seen from Example 6 that the optical elements with high precision can be produced in good productivity from the respective preform groups.

According to the present invention, a glass preform group for precision press molding in which the variation in volume between each preform is controlled to the maximum, a method for producing the preform group from molten glass on the basis of very high productivity, the preform group or the above method The method of manufacturing an optical element from the preform which comprises the obtained preform group can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic diagram for demonstrating the manufacturing method of the glass preform group of this invention.

2 is a schematic view for explaining a method for producing a glass preform group of the present invention.

3 is a schematic view for explaining an example of a molding die used for producing a glass preform group of the present invention.

4 is a schematic view for explaining a method for manufacturing an optical element of the present invention.

5 is a schematic diagram for explaining an example of an optical element obtained by the method of the present invention.

<Explanation of symbols for the main parts of the drawings>

1: pipe

2: nozzle

3: cover for forming gas flow path

3-1: opening

4: gas flow path

5: cover

6: high frequency induction coil

10: melting apparatus

11: dustproof stand

12: constant temperature room

13: molding

13-1: When received

13-2: recess

14: molten glass red

15: main body

16: lower model

17: Pictograph

18: push rod

19: glass preform

20, 21: lens surface

22, 23: flanged flat part

24: edge

25, 26: corner

Claims (6)

It is a manufacturing method of the glass preform group which consists of several glass preforms used for precision press molding, A glass melting apparatus including a container for accumulating molten glass is mounted on a dustproof table, and a dustproof mechanism is installed in a structure supporting the glass melting apparatus by a structure in which a pipe and a nozzle which discharge the molten glass from the container are suspended. While dust-proofing the outlet of the molten glass by doing it, The molten glass flowing out from the nozzle at a constant flow rate is dripped sequentially from the outlet under a outlet atmosphere in which the temperature is controlled and controlled at a constant humidity corresponding to a humidity within a range of 10 to 95% relative humidity at 25 ° C. by doing, A method for producing a glass preform group, wherein a glass preform group having a ratio of the mass tolerance of the glass preform to the average mass M _AV of the glass preform is within ± 0.5 [%] x M _AV is produced. The manufacturing method of the glass preform group of Claim 1 which performs the shaping | molding after the said molten glass dropping while making it float by applying a wind pressure to the obtained molten glass drop. The glass preform which comprises the glass preform group obtained by the method of Claim 1 or 2 is heated, and precision press molding is carried out, The manufacturing method of the optical element characterized by the above-mentioned. The method of claim 3, wherein the precision press molding is performed by transferring each molding surface of the press molding mold having the upper mold, the lower mold, and the body mold to the glass. The edge formed by the surface formed by transferring the upper surface of the mold and the surface formed by transferring the body of the body, and the surface formed by transferring the body of the lower mold and the surface formed by transferring the surface of the body A method of manufacturing an optical element for precise press molding with at least one of the edges as a free surface. delete delete

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