JPH11322349A - Molding of glass product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for molding a glass molded product simply by directly carrying out the press molding and fabrication of a glass product such as an optical element having a highly accurate shape and a high surface accuracy from a molten glass gob in a molten and softened state without using after processing such as grinding or polishing at all. SOLUTION: A molten glass gob is kept at a prescribed temperature for a required time in a temperature region for determining the shape of a glass product so as to provide a temperature difference between the interior and the surface of the glass within 5 deg.C and an applied pressure is increased just before completing the maintenance of the temperature to make the surface of the molten glass gob follow the shape of the molding and transferring surface. The applied pressure is then reduced to simultaneously start the cooling and the resultant shape obtained at the holding temperature is kept in a method for molding a glass molded product comprising press molding the molten glass gob through a gas jetting from the molding and transferring surface of a porous forming mold while maintaining the molten glass gob and the forming mold in a noncontact state, then cooling the press molded glass gob and providing the glass product.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for obtaining high precision optical glass elements such as lenses used in cameras and video cameras, and other glass products by press forming mainly in hot working. And a method for molding the same.

[0002]

2. Description of the Related Art Hitherto, optical glass products such as lenses have been cut out from a molten glass block into a shape close to the final shape, or directly pressed from a molten glass into a shape close to the final shape. The material was obtained by grinding and polishing.

In recent years, instead of the method of processing glass products by grinding and polishing, a method of heating and softening a molding material having no surface defects and directly press-molding the same using a molding die has attracted attention. .

Usually, in this type of molding, a molding material in a heated and softened state is pressed using a molding die member composed of a barrel die and an upper and lower die that slides in the barrel die, and the mold member is pressed. A method has been used in which a functional surface corresponding to a molding surface is transferred to the molding material, then cooled, and the glass product is removed from the mold member.

In Japanese Patent Publication Nos. 48-22977, JP-A-59-19554 and JP-B-54-39846, a porous material is used as a mold material, or ultrasonic vibration is used. Discloses a technique for forming a gas film on the surface of a mold, holding the molding die and the softened glass lump as a molding material in a non-contact state through the film, and performing press molding of a lens or the like in that state. Have been.

[0006]

However, in the conventional grinding / polishing method, after a glass block is cut out, a step of grinding the glass block into a shape similar to a final product,
In order to remove many defects near the surface layer of the pressed glass material, it is necessary to perform a grinding process to largely remove the outer periphery of the glass material (molded glass lump), and then to the final product shape. A step of polishing the surface of the glass material by fine grinding and polishing was required.

[0007] In this grinding and polishing, usually, at least 0.
It is necessary to grind and remove to a depth of 5 mm or more, and final removal and processing of about 50 μm by fine grinding and about 10 μm by polishing are required. Therefore, many steps are required until the product is completed, it takes time, and a large amount of glass sludge is generated due to cutting and grinding for forming a shape, and a great deal of labor is required for the processing for environmental protection. .

[0008] Even in the conventional method of press-molding using the above-described mold, the same problem as described above may occur in some cases in order to obtain a molding material without surface defects. Since the heated mold and the molding material come into direct contact with each other, fusion occurs between the molding material and the mold, or the glass and the molding material come into contact with the molding material glass and the molding die. This may cause deterioration of the mold such as reaction and wear of the mold surface. Furthermore, when a precision glass product such as a lens is directly molded from a high-temperature molten glass, these problems become remarkable, and it becomes substantially difficult to employ such a molding method.

In order to avoid the above-mentioned problems, in the inventions described in Japanese Patent Publication No. 48-22977 and Japanese Patent Application Laid-Open No. 59-19554, a molding die is not brought into contact with glass as a molding material. A molding technique has been proposed. It is ideal to mold the glass while keeping the glass and the mold in a non-contact state, and it has an effect on the surface state of the molded article, such as prevention of fusion, but it has a softened state. If only a high temperature molding material is molded and cooled, a temperature distribution occurs inside the molded product during cooling, and heat shrinkage during cooling does not occur evenly, and shrinkage is relatively high Because it concentrates on the part, after cooling, the part deforms into a concave state, a phenomenon called so-called sink occurs.
There is a problem that the shape of the final molded product is largely different from the original shape of the final product.

[0010] Similarly, in the molding method described in Japanese Patent Publication No. 54-39846, the molten glass is received in a receiving mold (lower mold) in a non-contact state, and the molten glass lump is brought into contact with a solid surface. The molten glass ingot is cooled to a temperature at which the molten glass ingot can be formed without any damage to the surface, and is brought into contact with a solid surface (mold transfer surface) of the mold so as to be refined. Press-formed the molten glass lump, at that time, in order to avoid the above-mentioned sink, after cooling,
The shape of the plunger for forming the plane of the glass block by contact molding so as to have a substantially flat shape is corrected not to a simple plane but to a conical shape.

However, as described in the embodiment, in this conventional technique, a step such as polishing is required after press molding, and the molten glass lump is placed in a lower mold having an open upper surface. After the glass is solidified to some extent, in order to press-mold, there is a restriction that only one side of the glass material having a shape close to a plane can be subjected to press molding, and further, the temperature and temperature of the supplied molten glass mass If the temperature distribution or the temperature distribution of the molded product due to cooling is not uniform, the amount and location of sink marks will not be constant, and it will be very difficult to produce a highly accurate product.

The present invention has been made based on the above circumstances, and a first object of the present invention is to provide an optical element having a high-precision shape and surface precision directly from a molten glass mass in a molten softened state. An object of the present invention is to provide a method for forming a glass molded product obtained by subjecting the glass product to a pressure molding process without using any post-processing such as grinding and polishing.

A second object of the present invention is to form a glass product such as an optical element having a high-precision shape and surface accuracy from a molten glass lump in a molten softened state by grinding to remove sludge. In particular, the amount of removal of the surface generated by the grinding can be reduced by the conventional one without causing a large amount.
It is an object of the present invention to provide a method for forming a glass product which can be set to / 10 or less.

[0014]

Means for Solving the Problems (Essential part of the invention) For this reason, in the present invention, the molten glass block and the molding die are brought into non-contact with each other via a gas ejected from the molding transfer surface of the porous molding die. The molten glass ingot is pressure-formed while being held in the state described above, and then cooled, and in a method of forming a glass molded product to obtain a glass product, the temperature inside the glass is determined in a temperature range that determines the shape of the glass product. The temperature is maintained at a predetermined temperature for a required time so that the temperature difference between the surface and the surface is within 5 ° C. Immediately before the completion of the temperature holding, the pressing force is increased, and the surface of the molten glass block is formed into the shape of the molding transfer surface. And then
The cooling is started at the same time as the pressing force is reduced, and the shape obtained at the holding temperature is maintained.

[0015] In the present invention, the molten glass lump is pressurized while maintaining the molten glass lump and the molding die in a non-contact state through a gas ejected from the molding transfer surface of the porous molding die. In a method for molding a glass molded product, which is molded and then cooled to obtain a glass product, the temperature difference between the inside and the surface of the glass is within 5 ° C. in a temperature range that determines the shape of the glass product. , Required time, while holding at a predetermined temperature, just before the completion of the temperature holding, increasing the pressing force, so that the surface of the molten glass block follows the shape of the molding transfer surface,
Thereafter, cooling is started at the same time as the pressing force is reduced, the shape obtained at the holding temperature is maintained, and the surface layer of the glass material thus obtained is removed by fine grinding / polishing to remove the glass product. It is characterized by obtaining.

This makes it possible to suppress the occurrence of sink marks so that the shape of the glass molded article after the completion of cooling is always constant. Even if sink marks occur, the amount and position of the occurrence of sink marks can be accurately determined. In accordance with the reproducibility, a finished product can be obtained with minimum precision grinding and polishing.

In this case, the temperature of the molten glass ingot in the above step is adjusted by the temperature of the gas ejected from the molding transfer surface of the molding die. In particular, in the temperature holding step, the temperature of the ejected gas is set to an arbitrary value. The temperature of the molten glass lump is set to a desired temperature by raising and lowering the temperature, and the holding temperature at that time is 10 ⁶ to 10 ¹⁰ dPa in terms of the viscosity of the glass to be formed.
A temperature corresponding to s is preferred as an embodiment of the present invention.

(Parts Attached to the Invention) The parts accompanying the essential parts of the invention will be described below. In the present invention, the melt-softened glass lump is supplied to a porous mold including at least a pair of upper and lower molds that determine the shape of the glass product, the mold is closed halfway, and the glass is shaped into a shape close to the final shape. When molding is used, the viscosity of the molten glass lump supplied to the molding die is preferably in the range of 10 to 10 ⁵ dPa · s. This is because the molding of the molten glass mass supplied to the molding die at this time is not forced to be deformed by the pressing force, but rather, the molding die is brought close to a very soft fluid glass and the molding is performed. This is because the shape of the molding transfer surface of the mold can be imitated via the gas film formed by the gas ejected from the transfer surface.

Incidentally, if the molten glass lump is hard here, when the molten glass is supplied onto a forming die (lower die), the glass lump does not deform due to the pressure of the gas film, but breaks through the gas film and directly. Contact with the molding transfer surface of the mold. Also, when the molten glass lump is to be shaped according to the shape of the molding transfer surface of the molding die, the molten glass lump must be able to be greatly deformed, but the shape of the molten glass lump matches the shape of the molding transfer surface of the molding die. Because the gas film is easily deformed when it is not deformed, the above-mentioned gas film is easily broken, and the molten glass lump comes into contact with the mold, which causes harmful defects on the glass molded article later. There is also a fear that it will. Therefore, for that purpose, it is necessary to supply molten glass with the above-mentioned viscosity.

Further, when supplying a required amount of molten glass lump from a molten glass stream flowing out of a melting furnace onto a mold,
When the viscosity is 10 ³ dPa · s or less, the required amount of molten glass ingot can be easily obtained by utilizing the surface tension of the molten glass ingot without using a cutting means such as a cutting blade for separation from the glass flow. Separated and supplied. In this case, as described above, when the molten glass having an excessively high fluidity is directly supplied to the molding die, the molten glass lump passes through the gas film and directly contacts the molding transfer surface of the molding die. For this reason, it is necessary to adjust the surface of the very surface layer, which first comes into contact with the molten glass forming mold, to be slightly harder than the inside by cooling it to a required viscosity in advance. Is necessary to prevent the molten glass lump from contacting the mold.

At this point, it is desirable that the thickness of the molded article in the middle of molding is about 1 to 5% larger than the thickness of the finally obtained molded article. This is for keeping the deformation allowance in the subsequent steps, and is performed subsequently.
Any amount can be used as long as it can correct the deformation caused by the shrinkage of the glass with respect to the mold, which is generated when the predetermined temperature state is maintained. In addition, since the final deformation action in the step performed immediately after the holding of the temperature state is performed on the hard glass, it is preferable that the deformation amount is as small as possible. % Is the most preferable, and it is necessary to suppress the maximum to about 5%. If the thickness at this point is too large, it cannot be deformed to the desired final thickness, or excessive force is applied to the gas film, and And the mold come into contact with each other, resulting in a defect in the molded product.

The porous mold used here has a difference in the thermal expansion difference of the glass at the temperature at the time of maintaining the predetermined temperature state during the molding and the temperature at the time of the actual use of the glass product. In consideration of factors such as the difference in the coefficient of thermal expansion between the glass and the mold, it is desirable that the shape of the mold be corrected in advance so that it matches the final desired shape of the glass product. By doing so, a more accurate glass product can be obtained. Further, as the porous material used for the mold, the maximum pore diameter of the porous material is 20 μm or less, preferably 10 μm or less, and the porosity is 10 to 3 μm.
At 5%, the material is desirably a ceramic such as alumina, silicon nitride, silicon carbide or the like, which has oxidation resistance, or porous carbon. Further, the molding transfer surface is formed through a film made of gas ejected from a molding die. In order to transfer a good shape to a glass product, it is desirable that the glass product is processed into a smooth mirror-like surface without protrusion. In addition, since the gas to be ejected from the mold and to form a thin gas film on the glass and the molding transfer surface of the mold needs to be ejected at a high temperature, it is necessary to prevent not only oxidation of the mold material but also Also, from the viewpoint of preventing oxidation including constituent materials around the mold, it is desirable that the gas is a non-oxidizing gas.

As described above, the temperature of the glass that has been formed halfway while holding the forming die in a state where a slight pressing margin is left is determined not only by the temperature difference between the inside and outside of the glass but also by the temperature. This is to make the temperature distribution and the density distribution of the entire glass uniform. That is, in the steps up to this point, the density difference due to the difference in the amount of thermal expansion and contraction caused by the temperature difference generated inside the glass is eliminated by maintaining the above-mentioned predetermined temperature state,
This is to obtain a glass product having an approximate shape without a temperature distribution and a density distribution.

At this time, the range of the variation in the temperature distribution of the glass must be kept within 5 ° C. regardless of the size of the glass. It is a temperature corresponding to 10 ⁶ to 10 ¹⁰ dPa · s in viscosity. By the way, if the variation range of the temperature distribution is too wide, the above-mentioned density distribution is not sufficiently eliminated, and if the temperature distribution is cooled while the variation is large, the generation amount of the sink is large, and the location of occurrence is limited. It is no longer possible to cope with the correction, and finally a glass product with high accuracy cannot be obtained. For this reason, this range has a shape accuracy, that is, an error from a desired shape of several tens μm,
Alternatively, when accuracy at the Newton's ring level is required, the above range is a limit. The narrower this range is, the higher the accuracy of the obtained product is.

Further, the final temperature at this time, in other words, the pressure at which the pressing force is increased immediately before the completion of the temperature holding, the mold is closed, and the temperature at which the glass is imitated to the shape of the molding transfer surface of the mold is transferred. If it is too high, it may be deformed by a very small force due to the weight of the glass lump or the blowing of blowing gas during cooling, or the amount of cooling shrinkage due to the temperature gradient generated inside the glass before cooling and solidification Due to the difference, the flow of the glass occurs, causing sink marks or the like, so that accuracy cannot be maintained. For these reasons, in order to obtain the above accuracy, the upper limit of this temperature is limited to a temperature corresponding to 10 ⁶ dPa · s in the viscosity of the glass to be formed, and higher accuracy is required. In some cases, this temperature needs to be lowered.

Conversely, if the temperature is lowered too much, the glass becomes too hard and cannot follow the shape of the molding transfer surface of the mold in order to obtain the final thickness. In particular, in this molding method, since the molding is performed via the gas film, the glass is molded in an approximate shape of the molding transfer surface of the molding die in advance, and the pressing force is uniformly applied to the whole. Also, if the deformation pressure is too high for the deformation capacity (= viscosity) of the glass, the gas film will break easily,
The glass comes into contact with the mold, leaving harmful defects in the molded product. For this reason, it is usually necessary that the temperature at this time be equal to or higher than the temperature corresponding to 10 ⁹ dPa · s in terms of the viscosity of the glass to be formed. ^The temperature corresponding to ¹⁰ dPa · s is the limit.

The most effective way of eliminating the variation in the temperature distribution of the glass and adjusting it to the final temperature is to directly adjust the temperature of the gas ejected from the molding transfer surface of the molding die. This is because only the gas ejected from the molding transfer surface of the molding die substantially touches the glass lump, and no matter how much the temperature of the molding die or the atmosphere around the molding die is controlled, the molding transfer surface In order for the temperature of the gas flowing out and constantly flowing to be in equilibrium with the temperature of its mold and atmosphere,
This is because it takes time and it is difficult to perform fine and quick temperature control. However, before the temperature-controlled gas is ejected from the molding injection surface of the mold and hits the surface of the glass block,
In order to maintain the temperature, it is necessary in some cases to supplementarily control the temperature of the mold and the temperature of the atmosphere.

In addition, in the method of adjusting the temperature at this time, in consideration of the fact that a temperature gradient always occurs inside the object when the object is heated and cooled from the outside, the temperature peaks and valleys due to the temperature gradient inside the glass are taken into consideration. After cooling the outside and then cooling the inside, the next step is to bring the outside closer to the inner temperature (increase the gas temperature) and cool the outside further. As described above, a method is used in which the gas temperature is gradually lowered while swinging up and down, and the temperature is controlled and maintained at a desired temperature. In this case, the thickness, size, and temperature difference to the desired temperature of the product, the width of the gas temperature, the time, the number of times, etc. are adjusted, so that the temperature range within the variation width of the temperature distribution described above is there.

In this way, the variation in the temperature distribution inside the glass is within 5 ° C., and the viscosity of the glass is 10 ⁶
When the temperature is equivalent to 〜１０10 ¹⁰ dPa · s,
The molding die that has left the pushing margin is closed, and the glass block is copied in a non-contact state to the shape of the molding transfer surface of the molding die.At this time, the closing speed is set according to the viscosity of the glass, The flow rate and pressure of the gas need to be increased so that the membrane withstands its viscosity and closing speed, and the glass and the mold can be kept in a non-contact state, and the temperature of the gas does not change. Need to be maintained.
In this state, the molded glass lump is instantaneously relieved even if distortion accompanying molding occurs, so that both the temperature and the density are uniform.

Next, the mold is closed, the glass block follows the molding transfer surface of the mold, and when the flow of the glass stops, the pressure applied to the mold is reduced or released, and at the same time, cooling is performed. To start. This cooling needs to be performed quickly and uniformly so as to maintain the shape of the glass product following the shape of the mold. To do so, lower the temperature of the gas ejected from the mold, and make sure that the gas hits the molded article evenly without opening the mold, and that the molded article does not deform due to the cooling gas pressure. , The pressure and flow rate of the gas to be ejected must be reduced.

The glass product thus cooled is:
If the flow of the glass due to the variation in the temperature distribution does not occur during cooling, there is no occurrence of sink marks and a very accurate glass can be obtained. In particular, according to the method of the present invention, before the start of cooling, the temperature and density of the glass are almost constant, and the starting temperature of the cooling is a temperature corresponding to 10 ⁶ to 10 ¹⁰ dPa · s in viscosity of the glass, Further, since the glass lump and the molding transfer surface of the molding die are not in contact with each other and the glass lump is not restrained by the molding die during cooling, a hardness of 10 ⁸ dPa · s or more is maintained in this range. When it is cooled within a few tens of seconds, if it is quickly cooled, almost no flow inside the glass occurs, and when the hardness is lower than that, the amount of generation of sink marks is extremely small by cooling similarly. Also, the amount and location of the generation are substantially constant. For this reason, if the demand for accuracy is not severe, there is not much problem, and even when accuracy is required, it can be adequately dealt with by slightly correcting the shape of the molding transfer surface of the mold from the molding result, and ultimately It is possible to obtain very accurate glass products.

Further, the glass product thus obtained is further reheated in a non-oxidizing atmosphere or the like, and is subjected to contact press molding using a high-precision molding die to form an aspherical lens. Of course, it is also possible to easily obtain a high-precision optical element at a low cost.

Further, as already pointed out in the second invention, the steps for molding a precision element such as an optical element are as follows.
When a glass product such as an optical element is molded directly from a molten glass lump using a porous molding die, a gas is blown from the porous die, and the molten glass and the molding transfer surface of the molding die are non-contact. While maintaining the contact state, closing the mold, and performing pressure molding, before the glass block to be molded completely conforms to the shape of the molding transfer surface of the mold, the glass is once deformed by pressing. Is stopped, whereupon the glass block is cooled, and the temperature is once held so that the temperature difference inside the glass is within 5 ° C. in the temperature range that determines the shape of the product, and immediately before the completion of the temperature holding. By increasing the pressing force, closing the mold, imitating the glass lump to the shape of the molding transfer surface, then, while reducing the pressing force, simultaneously starting cooling and maintaining the shape obtained at the holding temperature, Obtain a molded glass lump (molded product)
The surface layer of the obtained glass material is further finely ground and / or
Alternatively, it is removed by polishing to obtain a final glass product. In addition, the thickness of the surface layer of the glass material removed by such precision grinding or polishing may be substantially 50 μm or less by the above-described press molding method, and as a result, the generation of glass sludge is extremely small. Become.

In such a forming method, the structure up to obtaining the glass material is the same as that of the first invention. However, by further permitting polishing, it becomes possible to obtain a more accurate shape. Also, when the thickness of the product is too thick and the shape is difficult to come out, or the temperature-viscosity characteristic curve stands,
It has a high temperature dependence of viscosity, and is effective for molding glass, for which it is difficult to control viscosity by temperature.

As described above, in this molding method, a highly accurate molded product can be obtained by the press molding according to the first invention. However, conventional processing such as grinding for sharply shaving glass is not required, and the object can be sufficiently achieved only by fine polishing to the extent that the surface is polished. In this polishing, for example, in the case of a lens-shaped glass product having a diameter of about 20 mm and a thickness of about 3 mm, a processing allowance of 10 μm or less is sufficient, and a polishing time of several tens of seconds is sufficient. The polishing allowance of 50 μm or less is sufficient for a large thickness and a large diameter. Conversely, according to the pressing method of the present invention, the formed glass block (fine polishing) The shape of the previous glass product) does not cause an error of 50 μm or more from a desired design value.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a schematic diagram of a molding apparatus used in the present invention.
Is a lower mold unit, 2 is an upper mold unit, and upper and lower mold units 1 and 2 are each a lower mold 11 which is a lower mold.
And an upper die 21 as an upper surface forming die, and a lower die holder 12 and an upper die holder 22 for holding them.
The holders 12 and 22 have pressure chambers 12a for supplying and distributing the fluid to the lower mold 11 and the upper mold 21 in a balanced manner.
22a are provided respectively, and the heater 1
3 and 23 and a temperature measuring means (not shown) are embedded so that the temperature of the fluid ejected from the molding transfer surfaces 11a and 21a of the lower mold 11 and the upper mold 12 can be finally finely adjusted. Has become.

The molding transfer surfaces 11a and 21a each have a transfer function for determining the shape of an optically functional surface of a glass product to be molded, for example, a glass optical element such as a lens. A drive unit (not shown) is attached to each of the lower die unit 1 and the upper die unit 2, and the lower die unit 1 and the upper die unit 2
However, each can be moved independently. Further, connection pipes 14 and 24 for supplying N ₂ gas are connected to the holders 12 and 22 as shown in the figure, and are controlled to an arbitrary pressure and flow rate by a flow rate pressure regulator (not shown). the N ₂ gas, by the same controller (not shown), and N ₂ gas heater 16, 26 are individually controlled, via the flexible tube 15, 25 having heat resistance, pressure chambers 12a, to 22a The temperature, pressure and flow rate of the N ₂ gas ejected from the molding transfer surfaces 11a and 21a can be arbitrarily controlled.

FIG. 2 to FIG. 4 are process explanatory diagrams when the molten glass in a molten and softened state is supplied to a forming die from a supply nozzle, and the supplied molten glass is cut and separated from the supply nozzle. Reference numeral 101 in FIG. 2 denotes a supply nozzle of the molten glass 102 in a molten and softened state, and reference numeral 103a in FIG. 3 denotes a molten glass mass before cutting supplied onto the molding transfer surface 11a of the lower mold 11, and , Code 103b
Represents a constriction created between the molten glass 102 for cutting and the molten glass lump 103a before cutting, and the reference numeral 104 in FIG. 4 represents the molten glass lump obtained on the molding transfer surface 11a.

[0039]

Embodiment (First Embodiment) Next, a process of forming a glass product using the above-described forming apparatus will be specifically described with reference to the drawings. The glass products molded here are:
Φ15m used for video camera as shown in FIG.
m is a convex meniscus spherical lens, the curvature of the optically effective surface is R = 30 mm and R = 20 mm, the center thickness is 2 mm, and the glass material has a temperature of 1200.
10 ^1.6 dPa · s at ℃, 10 ^2.9 at 890 ° C.
dPa · s, 10 ⁵ dPa · s at 720 ° C., 610
10 ^7.55 dPa · s at ℃, 10 ¹³ d at 498 ° C
Optical glass having a viscosity characteristic showing a viscosity of Pa · s was used.

The molding transfer surface 11a of the lower mold 11 and the molding transfer surface 21a of the upper mold 21 are positioned between the molding transfer surface and the glass block so that the lens at room temperature after molding has the above-mentioned lens shape. Assuming that the thickness of the gas film finally becomes 5 μm, it is further processed into a shape using the corrected numerical value in consideration of the thermal expansion of the glass and the mold, and the surface (mold transfer) Surface) is the surface excluding the hollow of the porous hole,
It is processed to a mirror surface state of Rmax 0.3 micron or less. As a material of the lower mold 11 and the upper mold 21, a porous alumina-based ceramic having a porosity of 30% and a maximum hole diameter of 8 μm is used. Nitrogen gas is used to prevent oxidation of the mold 12.

Next, the lower mold 1 prepared as described above is prepared.
1. Attach the upper mold 21 to the molding device shown in FIG.
4 to 4 to obtain a molten glass lump. Hereinafter, this process will be specifically described with reference to FIGS. First, in a glass melting furnace (not shown), a glass material is melted, defoamed, and homogenized to prepare a homogeneous molten glass 102 in a softened state. The supply nozzle 101 was set at a temperature of 1200 ° C., the molten glass 102 was allowed to flow out, and the lower mold unit 1 was taken just below the supply nozzle 101, and as shown in FIG. After receiving a predetermined volume of molten glass on the molding transfer surface 11a, as shown in FIG. 3, the lower mold unit 1 is slightly lowered downward as shown by the arrow A, and the molten glass 102 and the molten glass lump 103a before cutting are formed. During this time, a crack 103b is generated, and waits until the crack 103b is cut by its own weight and surface tension. As a result, as shown in FIG. 4, a molten glass lump 104 in a softened state was obtained.

By temporarily stopping the lower mold unit 1 in the step of cutting the molten glass 102 as described above, the portion of the crack 103b is less likely to be cooled, and it is possible to cut naturally by its own weight and surface tension. Because of this, the glass material solidifies into a thread at the cutting part and remains,
Alternatively, no trace of breakage is usually left by a cutting blade used for cutting glass. Therefore, no harmful defects occur on the surface of the molten glass lump 104.

When the molten glass is received on the molding transfer surface 11a, the temperature of the jetted N ₂ gas at this time is 500 ° C., which is the temperature near the glass transition point, and immediately thereafter, it is 600 ° C.
° C, the temperature of the heaters 16 and 13 is adjusted, and the flow rate of the N ₂ gas
It was controlled to be 20 liters per minute until immediately before receiving 1a, and then 5 liters per minute thereafter. By doing so, before the molten glass 102 reaches the molding transfer surface 11a, its tip is slightly solidified, the fluidity is reduced, and the flow rate of the jetted N ₂ gas is increased.
The molten glass block 104 was obtained without the tip of the molten glass 102 coming into contact with the molding transfer surface 11a at all, and in addition to using the above-described cutting method, without any defect on the surface.

Next, the process of moving the lower mold unit 1 directly below the upper mold unit 2 and forming the molten glass lump 104 using the lower mold unit 1 will be specifically described with reference to FIGS. FIG. 5 is a diagram showing a state immediately before forming the molten glass lump 104 using the lower mold unit 1 and the upper mold unit 2.
At this time, the viscosity of the glass is determined by the molding transfer surface 11a of the lower mold 11.
The viscosity of the vicinity of the bottom surface which in receiving it has is 10 ⁵ ~ ^6.5 dPa ·
s and other portions were 10 ³ to 10 ⁵ dPa · s.

Next, in the lower mold unit 1 and the upper mold unit 2, the temperature of the N ₂ gas ejected from the molding transfer surface of each mold is adjusted to 10 ^6.5 dPa · s by the viscosity of the molten glass block 104.
The temperature was controlled so as to be 650 ° C., and the state as shown in FIG. 6 was obtained. At this time, the distance between the lower mold unit 1 and the upper mold unit 2 was controlled such that the thickness of the center of the glass half-molded product 105 was 2.04 mm in the cold state. In addition, the above-mentioned semi-molded article 105, the lower mold 11, the upper mold 21
The flow rate and the pressure were adjusted so that the gas film thickness in the period between was about 50 μm. In this state, the temperature of the N ₂ gas is set at 610 ° C. ( ^107.55 dPa · s in ^{terms of} glass viscosity).
The temperature near the center of the semi-molded article 105 is 630
C. (at the glass viscosity of 10 ^7.0 dPa · s), the temperature of the N ₂ gas was kept at 620 ° C. (at the glass viscosity of ^10.7.26 dPa · s) for 15 seconds. By doing so, the temperature of the semi-molded article 105 becomes 620 ° C. ± 2.5 ° C.
Thus, the strain and density distribution due to the heat history up to now have been completely eliminated.

Next, while maintaining this temperature state, FIG.
As shown in the figure, the center thickness of the glass molded product 106 is 2 m
m, and the molding transfer surfaces 11a, 21a and the glass molding 1
The lower mold unit 1 and the upper mold unit 2 are gradually approached while adjusting the flow rate and pressure of the N ₂ gas so that the thickness of the N ₂ gas film during the period 06 is about 5 μm.
And the upper mold 21 are closed, the shapes of the molding transfer surfaces 11a and 21a are transferred to the semi-molded product 105, and a glass molded product (lens)
106 was obtained.

This closed state is maintained for 5 seconds, and when the movement of the glass inside the glass molded article 106 is completely stopped,
At the same time when the tightening force on the lower mold unit 1 and the upper mold unit 2 is released, the pressure of the N ₂ gas is reduced, and the temperature is set to reach room temperature in 15 seconds, and rapid cooling is performed. Was. After the start of cooling, when the viscosity near the surface of the glass molded product reaches 10 ¹² dPa · s (at a temperature of about 510 ° C.), the lower mold 1 and the upper mold 2 are opened, and the molding transfer surface 1 of the lower mold 11 is opened.
1a, the glass molded product 106 was taken out from the lower mold unit 1 in a state where the N ₂ gas was jetted.

In this way, the accuracy was measured when the glass molded article 106 was completely at room temperature, but the accuracy was measured. It could be confirmed that the function as sufficient as can be achieved.

(Second Embodiment) Next, using the same apparatus and material as in the first embodiment, one side as shown in FIG.
A biconvex glass spherical lens for a compact camera having 0 mm, R = 30 mm on the other surface, a center thickness of the lens of 4 mm, and a diameter of 14 mm was formed. Here, similarly to the first embodiment, the molding transfer surface 11 of the lower mold 11 is formed.
a and the molding transfer surface 21a of the upper die 21 are processed into a shape in consideration of a number of corrections, and then, are further actually formed, and a minute correction for final sink is performed based on the shape data. Thus, a shape that can be molded without any problem was determined.

The surface condition of the molding transfer surfaces 11a and 21a was finished to have a smooth mirror surface with no protrusion, as in the first embodiment, to give a final shape. Here, as a material of the lower mold 11 and the upper mold 21, a porosity of 25 is used.
% And a porous alumina having a maximum hole diameter of 6 μm was used, and N ₂ gas was used as the gas to be ejected, as in the first embodiment.

Next, the lower mold 1 prepared as described above is prepared.
1. Attach the upper mold 21 to the molding device shown in FIG.
The molten glass lump 104 was obtained in exactly the same manner as in the example of FIG. Next, the lower mold unit 1 is moved directly below the upper mold unit 2, and the viscosity near the lower surface of the molten glass lump 104 received on the molding transfer surface 11 a of the lower mold 11 is 10 ⁵ to ⁷ dPa ·
s, while the viscosity of the other parts is 10 ³ to ⁶ dPa · s, the flow rate of the N ₂ gas ejected from the molding transfer surfaces 11a and 21a is 5 liters per minute and 10 liters per minute, The viscosity was set to be 650 ° C. corresponding to 10 ^6.5 dPa · s, the center thickness of the semi-molded product 105 was 4.05 mm, and the molding transfer surfaces 11 a and 2
The lower mold 11 and the upper mold 21 were closed while controlling the pressure and flow rate of the N ₂ gas until the film thickness of the N ₂ gas between the first mold 1a and the _second mold 1 became about 30 μm.

Then, the temperature of the jetted N ₂ gas is set to 565 ° C.
(The viscosity of the glass was set to about 10 ^9.2 dPa · s). When the temperature at the center of the molten glass block 105 became 575 ° C. (about ^108.8 dPa · s with the viscosity of glass), the cooling was stopped once. , The gas temperature was reset to 570 ° C.
The temperature was kept for 2 seconds so that the temperature of the molten glass block 105 became 570 ° C. ± 3 ° C. (the viscosity of the glass was about 10 ⁹ dPa · s).

Next, as in the first embodiment, while maintaining this temperature state, the thickness of the center of the molded product 106 is reduced to 4 mm.
mm, and the lower mold unit 1 and the upper mold unit while adjusting the flow rate and pressure of the N ₂ gas so that the thickness of the N ₂ gas film between it and the molding transfer surfaces 11a and 21a is about 5 μm. 2 operates slowly at a low speed, and the lower mold 11 and the upper mold 2
1 and the molding transfer surfaces 11a and 21a are
5, and as a result, a molded product (lens) 106 was obtained.

This closed state is maintained for 10 seconds, and the molded article 1
When the movement of the glass inside 06 completely stopped, the tightening force on the lower mold unit 1 and the upper mold unit 2 was released, and at the same time, the pressure of N ₂ gas was reduced.
At 0 seconds, the temperature was cooled to reach room temperature. After the start of cooling, when the viscosity near the surface of the lens becomes 10 ^12.5 dPa · s (at a temperature of about 500 ° C.), the lower mold 11 and the upper mold 21 are opened, and N is transferred from the molding transfer surface 11 a of the lower mold 11. _The molded product 106 was taken out from the lower mold unit 1 while the _two gases were jetted.

The precision of the molded product was measured in the same manner as in the first embodiment. However, both the ass and habits were within about 1.0 Newton's ring. Could be obtained.

(Third Embodiment) Next, using the molding apparatus and materials used in the first embodiment, as shown in FIG. 10, the diameter is 10 mm, the curvature of the convex surface is R = 20 mm, and R = 20 mm. 30
A convex lens having a thickness of 2.5 mm and a central portion having a thickness of 2.5 mm was formed. Here, as in the first embodiment, the molding transfer surface 11a of the lower mold 11 and the molding transfer surface 21
a was processed into a shape in consideration of various corrections, and the surface state of each molding transfer surface was finished to a smooth mirror surface state as in the first embodiment, thereby obtaining a final shape. As a material of the lower mold 11 and the upper mold 21, porous silicon nitride having a porosity of 10% and a maximum hole diameter of 20 μm is used, and the gas to be ejected is N as in the first embodiment. _Two gases were used.

Then, the lower mold 1 prepared as described above is prepared.
1. Attach the upper mold 21 to the molding device shown in FIG.
The molten glass lump 104 was obtained in exactly the same manner as in the example of FIG. Next, the lower mold unit 1 is moved directly below the upper mold unit 2, and the viscosity near the lower surface of the molten glass lump 104 received on the molding transfer surface 11 a of the lower mold 11 becomes 10 ⁵ to ⁷ dPa ·
s, while the viscosity of other parts is 10 ³ to ⁶ dPa · s, the flow rate of N ₂ gas ejected from the molding transfer surfaces 11a and 21a is 5 liters and 10 liters per minute, and the set temperature is the viscosity of glass. 650 ° C equivalent to 10 ^6.5 dPa · s
While controlling the pressure and flow rate of the N ₂ gas until the center thickness of the semi-molded product 105 becomes 2.55 mm and the film thickness of the N ₂ gas between the semi-molded product 105 and the molding transfer surfaces 11a and 21a becomes about 50 μm. The lower mold 11 and the upper mold 21 were closed.

Then, the temperature of the jetted N ₂ gas is set to 580 ° C.
(Viscosity of glass is about ^108.2 dPa · s), and when the temperature of the center of the semi-molded article 105 reaches 600 ° C. (about ^107.8 dPa · s in viscosity of glass), cooling is stopped once. , The temperature of N ₂ gas is reset to 590 ° C.
After holding for half a second, the semi-molded article 105 was adjusted to 590 ° C. ± 2 ° C. (about 10 ⁸ dPa · s in terms of glass viscosity).

Next, in the same manner as in the first embodiment, while maintaining this temperature state, the center thickness of the above-mentioned molded product 106 is 2.5 mm, and the molded product 106 and the molding transfer surfaces 11a, 21a
So that the thickness of the N ₂ gas film between them is about 5 μm.
The lower mold unit 1 and the upper mold unit 2 are operated at a low speed while adjusting the flow rate and pressure of the N ₂ gas, and the lower mold 1 and the upper mold 2 are operated.
Is closed, and the shape of the molding transfer surfaces 11a and 21a is
The molded product (molded lens) 106 was obtained.

This closed state is maintained for 5 seconds, and the molded product 10
When the movement of the glass inside 6 has completely stopped, the lower mold 1
At the same time, the clamping force on the upper mold 2 was released, the pressure of the N ₂ gas was reduced, and rapid cooling was performed so that the set temperature reached room temperature in 10 seconds. After the start of cooling, when the viscosity near the surface of the lens becomes 10 ¹² dPa · s (about 510 ° C. in temperature), the lower mold 11 and the upper mold 21 are opened, and N _{2 is} transferred from the molding transfer surface 11 a of the lower mold 11. With the gas still erupting,
The molded product 106 was taken out from the lower mold unit 1.

Thereafter, the precision of the molded product was measured in the same manner as in the first embodiment, but in all cases, the ass fit within about 1.5 Newton rings and the habit within 1.0 Newton rings. The same good results as in Example 1 were obtained.

(Fourth Embodiment) Next, using the same apparatus and material as in the first embodiment, one side has an R as shown in FIG.
= 35 mm, the other surface was R = 60 mm, the center thickness of the lens was 5 mm, the diameter was 23 mm, and a biconvex glass spherical lens for compact cameras was molded. Here, similarly to the first embodiment, the molding transfer surface 11a of the lower mold 11 and the molding transfer surface 21a of the upper mold 21 are processed into shapes taking into account various corrections, and then the molding is further performed. Based on the shape data, a slight correction was made for the final sink mark to determine the shape.

Also, the surface condition of the molding transfer surfaces 11a and 21a was finished to have a smooth mirror surface with no protrusion as in the case of the first embodiment, and the final shape was obtained. In addition, lower mold 1
1. As the material of the upper mold 21, porous carbon having a porosity of 25% and a maximum hole diameter of 6 μm is used, and N ₂ gas is used as a gas to be ejected as in the first embodiment. Was.

Next, the lower mold 1 prepared as described above is prepared.
1. Attach the upper mold 21 to the molding device shown in FIG.
A molten glass lump 104 was obtained in exactly the same manner as in the example.
Then, the lower mold unit 1 is moved directly below the upper mold unit 2, and the viscosity near the lower surface of the molten glass lump 104 received on the molding transfer surface 11 a of the lower mold 11 is 10 ⁵ to ⁷ dPa · s,
Within the viscosity of the other portion is 10 ³ ~ ⁶ dPa · s, the molding transfer surface 11a, min 2 liters the flow rate of N ₂ gas ejected from 21a and 5 liters, 10 set temperature viscosity of the glass ^7.7 605 ° C. equivalent to dPa · s, the center thickness of the semi-molded product 105 is 5.06 mm, and the film thickness of N ₂ gas between the semi-molded product 105 and the molding transfer surfaces 11a and 21a is about 30 μm. Up to the pressure of N ₂ gas
The lower mold 11 and the upper mold 21 were closed while controlling the flow rate.

Then, the temperature of the jetted N ₂ gas is set to 590 ° C.
(Viscosity of glass: about ^108.2 dPa · s), and when the temperature at the center of the semi-molded article 105 reaches 600 ° C. (viscosity of glass: about ^107.8 dPa · s), once cooled, Stop and reset the temperature of N ₂ gas to 595 ° C.
The temperature was held for 0 second so that the temperature of the semi-molded article 105 became 595 ° C. ± 3 ° C. (about 10 ⁸ dPa · s in terms of glass viscosity).

Next, similarly to the first embodiment, while maintaining the temperature state, the thickness of the center of the molded product 106 is 4.01 m.
m, so that the thickness of the N ₂ gas film between the molded product 106 and the molding transfer surfaces 11a and 21a is about 3 μm.
₂ While adjusting the gas flow rate and pressure,
And the upper mold unit 2 are gradually operated at a low speed, the lower mold 11 and the upper mold 21 are closed, the shapes of the molding transfer surfaces 11a and 21a are transferred to the semi-molded product 105, and a molded product (lens) 106 is obtained. Was.

This closed state is maintained for 10 seconds, and the molded article 1
When the movement of the glass inside 06 has completely stopped, the tightening force on the lower mold unit 1 and the upper mold unit 2 is released, and at the same time, the pressure of the N ₂ gas is reduced, and the set temperature is further reduced to 2 mm.
Cooling was performed to reach room temperature in 0 seconds. After cooling starts,
When the viscosity near the lens surface becomes 10 ¹² dPa · s (about 510 ° C. in temperature), the lower mold 11 and the upper mold 21 are opened,
The molded product 106 was taken out of the lower mold unit 1 while the N ₂ gas was being blown out from the molding transfer surface 11 a of the lower mold 11.

Then, the precision of the molded product was measured in the same manner as in the first embodiment. However, since the surface had some undulations, which seemed to be caused by sink marks, using a polishing plate and an abrasive, Correction polishing was performed. The polishing amount at this time is a maximum of 8 μm, and the shape accuracy of the polished surface is as
Both habits were within 0.5 Newton rings.

(Fifth Embodiment) Next, using the same apparatus and material as in the first embodiment, a concave surface as shown in FIG.
0 mm, convex surface R = 60 mm, lens center thickness 3 m
m, a concave meniscus lens having an edge thickness of 5.5 mm and a diameter of φ30 mm used for a compact camera or the like was formed.

In the same manner as in the first embodiment, the molding
The imaging surface 11a and the molding transfer surface 21a of the upper mold 21 are
It is processed into a shape that considers positive, and the surface condition of each
As in the first embodiment, a smooth mirror surface without protrusions
Finished and finished shape. The lower mold 11 and the upper mold 2
Material 1 has a porosity of 25% and a maximum hole diameter of 6
μm porous carbon.
As in the embodiment of _TwoGas was used. By the way, this
Using the lower mold 11 and the upper mold 21 prepared as described above,
A molten glass lump 104 is obtained through exactly the same steps as in the embodiment.
Was.

Next, the lower mold unit 1 is moved directly below the upper mold unit 2, and the viscosity near the lower surface of the molten glass lump 104 received on the molding transfer surface 11 a of the lower mold 11 becomes 10 ^5.5 to ^6.5.
dPa · s, viscosity of other parts is 10 ³ to ^5.6 dPa
S, the flow rate of the N ₂ gas ejected from the molding transfer surfaces 11a and 21a is 3 liters and 8 liters per minute, and the set temperature is equivalent to 10 ⁷ dPa · s in terms of glass viscosity.
Cooled so as to be 30 ° C., the center thickness of the semi-molded article 105 is 3.1 mm, which the molding transfer surface 11a, until a thickness of approximately 50μm of N ₂ gas between 21a, the N ₂ gas The lower mold 11 and the upper mold 21 were closed while controlling the pressure and the flow rate.

[0072] Then, upon reaching a temperature of the center portion of the semi-molded article 105 is 640 ° C. (about a viscosity of the glass 10 ^{6. 7} dPa · s), once the cooling is the temperature of the newly N ₂ gas 5
Reset the temperature to 35 ° C and hold it for about 25 seconds.
05 at 535 ° C. ± 4 ° C. (approximately 10 ^6.8 dP
a · s).

Next, as in the first embodiment, the temperature
While maintaining the state, the thickness of the center of the molded product 106 is 5.0
1 mm, and between this and the molding transfer surfaces 11a, 21a
N _TwoN is adjusted so that the thickness of the gas film is about 5 μm._TwoMoth
While adjusting the flow rate and pressure of the
The mold unit 2 is gradually operated at a low speed, and the lower mold 11 and the upper mold 2 are operated.
1 is closed, and the shapes of the molding transfer surfaces 11a and 21a are semi-molded.
This was transferred to a product 105 to obtain a molded product (lens) 106.

This closed state is held for 15 seconds, and the molded article 1
When the movement of the glass inside 06 has completely stopped, the tightening force on the lower mold unit 1 and the upper mold unit 2 is released, and at the same time, the pressure of the N ₂ gas is reduced, and the predetermined temperature is further reduced by 2 mm.
Cooling was performed to reach room temperature in 5 seconds. After cooling starts,
When the viscosity near the surface of the lens became 10 ¹² dPa · s (about 510 ° C. in temperature), the lower mold 11 and the upper mold 21 were opened, and N ₂ gas was ejected from the molding transfer surface 11 a of the lower mold 11. The molded article 106 was taken out from the lower mold unit 1 in the state as it was.

Thus, the precision of the molded product was measured in the same manner as in the fourth embodiment. However, since fine undulations occurred in the outer peripheral portion of the lens, fine grinding and polishing were further performed. At this time, the removal amount of the surface layer by fine grinding is 40 at a maximum.
μm, and in the subsequent polishing, the ass fit in one Newton ring and the habit fits in 0.5 Newton rings or less,
A lens comparable to ordinary grinding and polishing could be obtained with the amount of sludge generated reduced by 90% or more.

[0076]

As described above, according to the present invention,
By removing factors that hinder the shape, such as sink marks caused by heat shrinkage of the glass, it is possible to obtain very accurate glass products directly from the molten glass, and furthermore, to obtain highly accurate glass products. In this case, it is possible to extremely reduce waste such as grinding and polishing debris generated by processing methods such as grinding and polishing, and to provide a large amount of glass products such as optical element lenses at low cost. can do.

[Brief description of the drawings]

FIG. 1 is a schematic view of a molding apparatus used in the present invention.

FIG. 2 is an explanatory diagram of a method for cutting a molten glass lump used in the present invention.

FIG. 3 is an explanatory diagram of a method for cutting a molten glass lump used in the present invention.

FIG. 4 is an explanatory view of a method for cutting a molten glass lump used in the present invention.

FIG. 5 is an explanatory view of a method for forming a molten glass lump according to the present invention.

FIG. 6 is an explanatory diagram of a method for forming a molten glass lump according to the present invention.

FIG. 7 is an explanatory view of a method for forming a molten glass lump according to the present invention.

FIG. 8 is a view of a glass product used in the first embodiment of the present invention.

FIG. 9 is a view of a glass product used in a second embodiment of the present invention.

FIG. 10 is a view of a glass product used in a third embodiment of the present invention.

FIG. 11 is a view of a glass product used in a fourth embodiment of the present invention.

FIG. 12 is a view of a glass product used in a fifth embodiment of the present invention.

[Explanation of symbols]

Reference Signs List 1 lower die unit 2 upper die unit 11 lower die 12 upper die 16, 26 N ₂ gas heater 101 molten glass supply nozzle 102 molten glass 104 molten glass lump 105 semi-molded glass product 106 glass molded product

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroyuki Kubo 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc.

Claims (5)

[Claims] 1. A pressure forming of the molten glass block while maintaining the molten glass block and the mold in a non-contact state via a gas ejected from a molding transfer surface of a porous mold, and In a method of forming a glass molded product, which is then cooled to obtain a glass product, the time required for the temperature difference between the inside and the surface of the glass to be within 5 ° C. in a temperature range that determines the shape of the glass product; While maintaining the predetermined temperature, immediately before the completion of the temperature holding, increasing the pressing force to make the surface of the molten glass block conform to the shape of the molding transfer surface, and then, after reducing the pressing force, simultaneously start cooling, A method for forming a glass product, wherein a shape obtained at a holding temperature is maintained. 2. The method for forming a glass product according to claim 1, wherein the temperature is maintained by adjusting a temperature of a gas ejected from a forming die. 3. The temperature range which determines the shape of the glass molded product is 10 ⁶ to ¹⁰ 10 based on the viscosity of the glass to be pressure-formed.
The method for forming a glass product according to claim 1, wherein the temperature is in a range corresponding to dPa · s. 4. A pressure molding of the molten glass mass while maintaining the molten glass mass and the molding die in a non-contact state through a gas ejected from a molding transfer surface of a porous molding die; In a method for forming a glass molded product, which is then cooled to obtain a glass product, the time required for the temperature difference between the inside and the surface of the glass to be within 5 ° C. in a temperature range that determines the shape of the glass product; While maintaining the predetermined temperature, immediately before the completion of the temperature holding, increase the pressing force to make the surface of the molten glass lump conform to the shape of the molding transfer surface, and then reduce the pressing force and simultaneously start cooling, A method for forming a glass product, wherein the shape obtained at the holding temperature is maintained, and the surface layer of the glass material thus obtained is removed by precision grinding and polishing to obtain a glass product. 5. The method according to claim 4, wherein the thickness of the surface layer of the glass material to be removed is 50 μm or less.