JPH09268021A - Injection molding for glass molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a glass molded product high in dimensional accuracy and slight in internal strain without developing any sink mark, by injecting a molten glass into a mold at a specified temperature followed by cooling. SOLUTION: First, dowels 1, 2 are heated by heaters 7, 8 in a clamped state in advance, and further heated to a temperature corresponding to 10<8> -10<12> poise in the viscosity of a molten glass based on the temperature detected by a timer or a thermosensor 15 built into a heater temperature controller 16, and then the heating operation is halted. Thereafter, a glass material melted by heating with a heater mounted on the cylinder barrel 18 of an injection molding machine is filled via a sprue 10 into a cavity 9 followed by making the temperature of the dowels 1, 2 fall by passing a cooling medium through channels 3, 4, or by controlling the heaters 7, 8; and after the temperature of the mold falls to the level corresponding to <=10<13> poise in the viscosity of the glass, the molded product is drawn out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding method capable of producing a glass molded product which requires high dimensional accuracy and has a small internal strain.

[0002]

2. Description of the Related Art In recent years, optical systems have become compact and lightweight,
There is an increasing demand for the use of aspherical lenses in optical systems for cost reduction.

Conventionally, aspherical lenses have been subjected to a polishing process requiring high skill as a final finish after grinding or cutting. Therefore, mass production is impossible, and the price of the aspherical lens becomes very expensive, and it has been used only for some high-end products.

However, it has become possible to mass-produce high-precision aspherical lenses by plastic injection molding. However, an aspherical lens made of plastic has a defect that the heat resistance temperature is about 100 ° C. at the highest and the optical characteristics change due to thermal expansion, and the optical characteristics change due to moisture absorption in a high humidity environment. To do.

Therefore, in recent years, a method of press-molding glass having excellent heat resistance and weather resistance into an aspherical lens by molding has been developed.

As a method for obtaining an optical component from a glass material by press molding, there are a so-called reheat pressing method and a direct pressing method.

In the reheat press method, a glass blank having a shape close to the shape of the final molded product is once formed, and the blank is housed in a molding die apparatus and heated and pressed to form by a die member of the die apparatus. A final molded product corresponding to the shape of the cavity to be obtained is obtained.

In the above-mentioned direct pressing method, molten glass is introduced into a molding die apparatus and pressurized to directly obtain a final molded article corresponding to the shape of the cavity formed by the die member of the die apparatus.

By the way, since it is preferable that the glass blank used in the reheat press method has good shape accuracy and surface accuracy to some extent, the glass blank may be ground and polished to obtain a predetermined accuracy. However, this requires time and labor for grinding and polishing, so the above direct press method may be used for the above glass plank production.

As the direct pressing method, as described in, for example, Japanese Patent Laid-Open No. 63-248727, a pair of molding die members facing each other in the horizontal direction while allowing molten glass to flow down from a nozzle. There is a method in which the molten glass is sandwiched by using the above, and the glass is cooled and hardened in the cavity thus formed to obtain a molded product having a predetermined shape. In this method, a ring-shaped cutting member is arranged on the outer periphery of the optical surface molding surface of the molding die member on one side, and this is advanced at the same time as the die member advance or after the die member advance, and the protruding glass is cut and removed. An optical component having a desired shape is formed. According to this method, an optical component can be obtained without leaving cutting marks of the flowing molten glass on the optical surface, which is preferable.

According to the press molding as described above, it is possible to manufacture an optical component such as a lens or a reflecting mirror having an aspherical optical surface, which takes a lot of time to manufacture by the conventional traditional grinding and polishing method. When applied to manufacturing, manufacturing time can be shortened.

However, in the above-mentioned press molding, not only the viscosity of the glass needs to be strictly controlled in order to form with stable quality, but also a mechanism for cutting and removing the protruding glass is required, so that the structure of the molding die is required. It will be very complicated.

Further, the above-mentioned press molding has a drawback that sink marks are likely to occur on the glass surface in the cooling process after the start of pressing. Therefore, as disclosed in Japanese Patent Laid-Open No. 1-249630, a method has been proposed in which molten glass is injected into a cavity of a molding die and filled in a pressurized state. In this method, in the injection molding method, molten glass is injected into the mold while keeping the mold temperature constant at about 100 ° C., and a high pressure is applied to transfer the shape of the cavity wall surface inside the mold. After that, the method of cooling and solidifying and taking out is adopted.

[0014]

However, in this method, among the glass injected into the mold, the glass in contact with the cavity wall surface in the mold is instantly cooled and solidified to form a skin layer, and the upper part thereof is formed. When the molten glass is pressed under high pressure, shear stress is generated at the interface with the skin layer, which causes the strain observed due to birefringence. Also, by being instantly cooled and solidified in this way, the shape is regulated at that point,
It also occurs that the cavity shape cannot be sufficiently transferred. Furthermore, a considerably large temperature difference is generated between the glass in contact with the mold and the molten glass inside the molded product, and the glass in contact with the mold cools the inside and outside of the molded product. It does not shrink uniformly on the surface, and when the internal glass cools and solidifies in the thick part, it shrinks like pulling the glass on the outer surface, and a dent called `` sink '' occurs on the outer surface, In the worst case, cracks will occur. Even if no sink mark is generated, a density distribution is generated, which becomes the distribution of residual stress, which affects the mechanical properties of the molded product, and the optical performance of optical parts is impaired. .

Therefore, the present invention has been made in view of the above-mentioned problems, and an object thereof is an injection molding method for producing a glass molded product which does not cause sink marks, has high dimensional accuracy, and has little internal distortion. Is to provide.

[0016]

In order to solve the above-mentioned problems and to achieve the object, an injection molding method of a glass molded article according to the present invention is characterized in that a heat-melted glass has a viscosity of 10 ⁸ to 10 10. ^The glass is filled into the cavity of the mold by injecting into a mold set to a temperature corresponding to the range of ¹² poise, and then the mold temperature corresponds to the viscosity of the glass of 10 ¹³ poise. The feature is that the molded product is taken out after cooling to the temperature or lower.

Further, in the injection molding method for a glass molded article according to the present invention, the passage through which the heated and melted glass reaches the cavity in the mold is heated, and the temperature of the passage is adjusted so that the viscosity of the glass is The feature is that the temperature is set to 10 ⁵ poise or less.

When the molten glass is injected into the mold set to the temperature within the above range, the glass in contact with the mold immediately drops to near the mold temperature, and the internal temperature of the molded product still melts. It is in a high state. However, if the mold temperature is sufficiently maintained at the glass transition temperature, the temperature of the glass in the molded product will be made uniform by controlling the mold temperature by applying pressure after filling to transfer the cavity shape. Then, if the mold is cooled so that the temperature of the glass of the entire molded product becomes the glass transition temperature or less while maintaining the uniform state, the temperature inside the molded product while maintaining the initial transfer accuracy. Highly accurate molded products can be obtained without uneven shrinkage due to uneven distribution.

[0019]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

(First Embodiment) FIG. 1 shows an injection molding apparatus used in an injection molding method according to a first embodiment of the present invention. The injection molding apparatus shown in the figure melts a glass material by heating and melting it in a cylinder barrel, and injects this glass material into a cavity of a mold from a nozzle at the tip of the cylinder barrel. This injection molding is preferably performed under a non-nitrogen gas atmosphere or the like. It is performed in an oxidizing gas atmosphere.

Therefore, a molding die, a mold clamping mechanism, etc. are mounted in the molding chamber 24 having an airtight structure. The pressure injection of the molten glass is performed by a plunger driven by a hydraulic cylinder (not shown) or an in-line screw type. The glass material is heated and melted by a heater provided in the cylinder barrel, and the viscosity of the glass is, for example, 10
^4.8 Poise.

In FIG. 1, 1 is a fixed-side insert piece provided in a fixed-side mold plate 13, 2 is a movable-side insert piece provided in a movable-side mold plate 14, and a cavity 9 is formed by 1 and 2. Has been done.

Reference numerals 7 and 8 denote heaters for heating the fixed and movable inserts, respectively, and are controlled by a heater temperature controller 16 via a temperature sensor 15. The heater temperature controller also has a built-in timer, and the heaters 7 and 8 can be controlled by the timer.

Reference numerals 3 and 4 denote heating and cooling medium passages for adjusting the temperature of the fixed side and movable side inserts, respectively, which are sealed by O-rings 5 and 6 and have a medium temperature controller 17 having a built-in solenoid valve. It is controlled by. 3A, 4
A indicates a connection path between the heating-cooling medium paths 3 and 4 and the temperature controller 17. Further, the heater temperature controller 16 and the medium temperature controller 17 can also send control signals to each other to control their respective operations.

A molding operation and a molding method of the injection molding die configured as described above will be described.

The glass, which has been heated and melted in a cylinder (not shown) of an injection molding machine (not shown), is clamped by heaters 7 and 8 in a state in which it is clamped before being injected into this mold. 2 is heated. Timer or incorporated in the heater temperature controller 16, a viscosity of 560 ° C. (glass based on the temperature detected by the temperature sensor 15 10 ^9.1
When the piece is heated up to the poise (corresponding to poise), the heating by the heater is stopped, and the heated and melted glass is injected into the mold, passes through the sprue 10, and is filled in the cavity 9. After that, a medium having an appropriate temperature is caused to flow through the medium passages provided in 3 and 4, or the temperature of the pieces 1 and 2 is controlled to 50 per minute while controlling the temperatures of the pieces 1 and 2 by the heaters 7 and 8.
The temperature is lowered at a temperature of 470 ° C., and the temperature is maintained at 470 ° C. corresponding to a glass viscosity of 10 ^14.6 poise.

After that, the molded product is taken out of the mold, the mold is clamped, and the pieces 1 and 2 are heated again by the heaters 7 and 8. Note that FIG. 3 shows changes in mold temperature and glass viscosity.

Although it is possible to immediately start cooling the mold after injecting the glass into the mold, in the case of a molded product having a large wall thickness or a molded product having a high required accuracy, when the glass is charged. It is necessary to keep the mold temperature for several seconds, apply a sufficient processing pressure during that time to sufficiently transfer the shape of the cavity, and relax the internal strain of the molded product.

Next, a specific example of molding a lens by the above method will be described.

The molding conditions are as follows.

Glass material BAL62 (low softening optical glass) manufactured by OHARA Inc. Injection temperature 680 ° C Injection pressure 1000kgf / cm ² Temperature change of fixed and movable pieces (no temperature difference between both pieces) 580 ° C to -50 ° Cooling to 470 ° C at a speed of C / min. Holding time 160 seconds Lens shape External shape: Meniscus lens of both spherical surfaces with a diameter of 20 mm and a wall thickness difference of 0.79 mm. The accuracy was less than 3 Newton rings, and no sink mark was generated.

As described above, this manufacturing method can be applied to all glass manufacturing methods such as the injection molding method and the injection compression molding method, and is a useful method for manufacturing a high-precision finished product.

(Second Example) FIG. 2 is a view showing a main part of a molding die according to a second embodiment. The molding die of the second embodiment is the sprue 10 of the molding die of the first embodiment.
The heating device 23 is provided in the periphery of the above so as to be able to perform heating. Since other configurations are the same as those of the first embodiment, the same functional parts are designated by the same reference numerals and the description thereof will be omitted.

The sprue portion 10 of the molding die is heated and held at 680 ° C., which corresponds to a glass viscosity of 10 ^4.8 poise. As the heating device, a known means such as a heater or a high frequency heating device is used. The injection molding method is the same as in the first embodiment. In the second embodiment, since the glass is in a molten state in the glass flow path up to the cavity 9 until the molded product is cooled and solidified, the pressure by the injection molding machine is applied to the molded product even in the cooling stage of the molded product. You can continue to add.
Thereby, the shape of the surface of the cavity can be more accurately transferred to the molded product.

When the molded product is taken out, the sprue,
No waste materials such as runners are generated. It is also useful from the viewpoint of productivity that the heating device cools the vicinity of the gate before opening the molding die to increase the viscosity of the glass near the gate and prevent the glass from sagging.

When the viscosity of the glass in the sprue exceeds 10 ⁵ poise, the loss of the flow pressure becomes large, and it becomes difficult to apply the molding pressure to the cavity sufficiently, and the cavity shape cannot be sufficiently transferred.

The present invention can be applied to a modified or modified version of the above embodiment without departing from the spirit of the invention.

For example, in the above embodiment, the mold temperature is set to 5
The case of cooling from 80 ° C (the temperature corresponding to the glass viscosity of 10 ^9.1 poise) to 470 ° C (the temperature corresponding to the glass viscosity of 10 ^14.6 poise) has been described. If the glass is heated to a temperature corresponding to 10 ⁸ to 10 ¹² poises and cooled after the glass is injected until the viscosity of the glass becomes 10 ¹³ poises or less, substantially the same effect as that of the above embodiment is obtained. can get.

[0039]

As described above, according to the present invention,
By defining the mold temperature that most affects the precision and internal strain of the molded product, it is possible to obtain a molded product with high dimensional accuracy and low internal strain. Further, since it is performed by injection molding, post-processing for centering like press molding is unnecessary, and the manufacturing cost is low.

Further, by heating the glass flow path to the cavity, a sufficient processing pressure can be applied to the cavity, so that the cavity shape can be sufficiently transferred. Further, since no waste materials such as sprue and runner are generated, the manufacturing cost can be reduced for expensive glass.

[0041]

[Brief description of drawings]

FIG. 1 is a schematic view of an injection molding device according to a first embodiment of the present invention.

FIG. 2 is a schematic view of a molding die according to a second embodiment of the present invention.

FIG. 3 is a graph showing changes in mold temperature according to the first embodiment of the present invention.

[Explanation of symbols]

 1 fixed side insert piece 2 movable side insert piece 3,4 heating and cooling medium passage 5.6 O-ring 7,8 heater 9 cavity 10 sprue 11 fixed side mounting plate 12 movable side mounting plate 13 fixed side template 14 movable side Template 15 Temperature sensor 16 Heater temperature controller 17 Medium temperature controller 18 Cylinder barrel 19 Nozzle 20 Screw 21 Cylinder heater 22 Nozzle heater 23 Sprue heating device 24 Molding chamber

Claims (2)

[Claims] 1. The heated and melted glass is injected into a mold set to a temperature such that the viscosity of the glass corresponds to the range of 10 ⁸ to 10 ¹² poise, and the glass is injected into the cavity of the mold. An injection molding method for a glass molded product, which comprises filling and thereafter cooling the mold until the viscosity of the glass becomes equal to or lower than a temperature corresponding to 10 ¹³ poise, and then taking out the molded product. 2. The heating and melting glass in the mold heats a passage leading to the cavity, and the temperature of the passage is set to a temperature corresponding to a viscosity of the glass of 10 ⁵ poise or less. The method of injection molding a glass molded article according to claim 1, which is characterized in that.