JPH08208246A - Glass press mold - Google Patents

Abstract

PURPOSE: To provide a glass press mold capable of producing a pressed-glass lens having excellent surface precision with suppressed generation of sink marks and without remaining gas pool. CONSTITUTION: A pair of forming molds composed of an upper mold 1 and a lower mold 2 have spherical or non-spherical surfaces of Ra and Rb, respectively, and have a forming effective diameter of DED in the shapes of forming surface. Further, they have respectively plain parts 1a and 2a at the outer peripheries of the spherical or the non-spherical parts having the forming effective diameter of DED and the plain parts 1a and 2a have a width of T. DED and T satisfy the following equation : D=DED+2×T where D is the diameter of the edging circles of the upper and the lower molds 1, 2. Further, letting the thickness of the edge of a formed article be (t), the equation T>(t) is satisfied in the molds 1, 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glass press molding die used for obtaining an optical element by press molding a heated glass material with a pair of upper and lower molding dies.

[0002]

2. Description of the Related Art Conventionally, glass press molding dies for press-molding a glass material to obtain an optical element are disclosed in, for example, JP-A-60-171233, JP-A-3-131537 and JP-A-5-201735. There is a described invention. The invention described in JP-A-60-171233 is
When a glass lens is molded by press molding, in order to eliminate the volume variation of the molded product due to the volume variation of the glass material, a space in which a surplus of the raw material glass can flow out is provided outside the molded product forming portion of the molding die.

In the invention described in Japanese Patent Laid-Open No. 3-131537, in the step of forming a convex lens or a convex meniscus lens, gas is left between the mold and the surface of the molded product while the glass material is being pressed, so that a dent is formed. In order to prevent the generation, a gas vent is provided in the molding die. Furthermore, the invention described in Japanese Patent Laid-Open No. 5-201735 has the same purpose as the invention described in Japanese Patent Laid-Open No. 3-131537, and a space is provided outside the optical function surface to save gas so that the gas does not remain on the optical function surface. It is what makes me.

[0004]

However, the above-mentioned respective prior arts have the following problems. That is, in molding a lens having a deep curvature, the flow amount of glass due to deformation increases, and so-called vignetting occurs in which the entire molding effective diameter of the mold shape cannot be transferred unless it is sufficiently softened by heating and pressed. . In addition, when the material is sufficiently softened by heating, the temperature of the entire material glass becomes considerably high, but a large temperature difference occurs when the material is cooled and solidified after the completion of pressing, and cooling shrinkage or so-called sink occurs to deteriorate surface accuracy. Let Furthermore, when considering convex lens molding with a deep curvature, a gas is sandwiched between the molding die and the material glass during pressing, and the gas eventually remains on the surface of the molded product to leave a recess, a so-called gas. May cause accumulation.

If the above three items are not satisfied at the same time,
Although the function of the glass press lens as an optical element cannot be satisfied, it may be extremely difficult depending on the product shape. For example, in order to prevent vignetting, the glass material may be sufficiently softened by heating and press-molded. However, if excessive heat is applied to the raw material glass for that reason, the temperature change of the raw material glass in the molding step becomes large, which causes sink marks due to heat shrinkage.

Alternatively, if attention is paid only to a gas pool, a technique for removing it is disclosed in Japanese Patent Laid-Open No. 3-131537.
Japanese Patent Publication discloses a method of providing a gas vent in a molding die. However, in this method, in addition to generating protrusions within the effective diameter of the molded product, surplus glass flows into the gas vent portion to cause clogging, and there is a problem that the effect does not continue when continuously molding. It is left.

It is an object of the present invention to achieve flow by maintaining the pressure inside the lens during molding at a high pressure so that sink marks,
An object of the present invention is to provide a glass press molding die that can perform glass press lens molding without vignetting and gas accumulation.

It is an object of claims 2 and 3 to provide a glass press molding die that can perform molding without generating a gas pool inside the effective diameter of the molded product.

[0009]

According to the invention of claim 1, a glass press molding die is characterized in that it has a flat surface portion having a width larger than a wall thickness dimension of at least an outermost periphery of an effective diameter of a molded product, outside the effective diameter of the molding. Is.

A second aspect of the present invention is the glass press molding die according to the first aspect, characterized in that a circumferential groove is formed between the effective diameter of the molded product and the flat surface portion.

According to a third aspect of the present invention, a circumferential groove is formed between the effective diameter of the molded product and the flat surface portion, and an auxiliary groove is formed from the groove to the outer peripheral portion of the molding surface. The glass press mold according to claim 1.

[0012]

The operation of claim 1 regulates the flow of excess glass caused by the molding pressure in the flat surface portion provided on the outer periphery of the molding effective diameter portion of the molding die, and maintains the internal pressure during molding of the molded product at a high pressure. .

According to the functions of claims 2 and 3, the gas remaining between the molding die and the raw material glass which cannot be extruded at the time of pressing is evacuated to the outside of the effective diameter of the molded product.

[0014]

Embodiment 1 FIGS. 1 to 4 show this embodiment, FIG. 1 is a sectional view showing a molding state, FIG. 2 is a sectional view of a carrying tray, and FIGS. 3 and 4 are graphs. The forming die including the upper die 1 and the lower die 2 has a spherical surface or an aspherical surface of Ra and Rb, respectively, as a forming surface shape, and the effective forming diameter is DED. In addition, a flat surface portion 1 is formed on the outer periphery of the molding effective diameter DED
a and 2a are formed and the width thereof is T. When the tip diameter of each of the upper and lower molds 1 and 2 is D, D = DED + 2 × T. When the edge thickness of the molded product is t, T> t
The upper and lower molds 1 and 2 are formed so that From the actual results, T
Is preferably about 1.5t <T <2t. As an example, showing the respective dimensions of the upper and lower molds 1 and 2 used in this embodiment,
DED = φ2.6 mm and T = 1.2 mm (= 1.7t).

In the forming process itself of this embodiment, the heat-softened raw material glass 3a is placed in a conveying tray 4 and conveyed between the upper and lower molds 1 and 2 (see FIG. 2).
This is a general one in which a molded lens 3 is obtained by molding by pressing a (see FIG. 1). However, in order to achieve the above object, the molding pressing force is higher than usual and is preferably at least 500 N or more. In addition, the pressing speed of the molding die is preferably set to a high speed, at least 200 mm / sec or more, in order to allow sufficient flow.

In this embodiment, since the flat portions 1a and 2a provided outside the effective molding diameter are made wider than the edge thickness of the molded product, the molding flow is regulated to some extent. Molding while maintaining high pressure,
The pressure will be increased as the molding progresses. Further, since the flow is regulated by the flat portions 1a and 2a but the structure is not a closed structure, the gas inside the molded product cannot be discharged.

FIG. 3 is a graph showing the surface accuracy of a conventional glass press lens molded product. This conventional example uses a molding part sealing structure as a means for keeping the internal pressure high in order to prevent sink marks, and although molding conditions are almost the same as this example, sufficient flow cannot be obtained. Therefore, a gas pool finally remained in the inner and outer peripheries of the effective diameter, resulting in poor surface accuracy (PV value, 0.688 μm).

FIG. 4 is a graph showing the surface accuracy of the glass press lens molded product of this embodiment. In contrast to the conventional example, this embodiment does not use a closed structure, but maintains the high internal pressure while regulating the flow by the flat surface, so that there is no sink due to cooling contraction or vignetting or gas accumulation due to poor flow, and an effective diameter. Very good surface accuracy (PV
Value, 0.149 μm) was obtained.

[0019]

Second Embodiment FIGS. 5 to 10 are sectional views showing the present embodiment. Reference numeral 11 denotes an upper mold, and a molding surface of the upper mold 11 has a flat surface portion 11 which is wider than the molded product effective diameter portion 11b and the molded product edge thickness.
a is formed, and further the molded product effective diameter portion 11b and the flat surface portion 1 are formed.
A groove 11c is formed at the boundary with 1a. Similarly, on the molding surface of the lower die 12, a molded product effective diameter portion 12b and a flat surface portion 12a wider than the molded product edge thickness are formed, and further, a groove 12c is formed at the boundary between the molded product effective diameter portion 12b and the flat surface portion 12a. Are formed.

As an operation of this embodiment, the flow state of the glass during molding will be described below with reference to FIGS. The material glass 3a is heated and softened, and is conveyed between the upper and lower molds 11 and 12 in a state of being housed in the conveying tray 14. Since the raw material glass 3a has been softened by heating to sufficiently perform molding transfer, the entire raw material glass 3a has risen above the softening point temperature and is apt to hang downward (see FIG. 5). Next, the upper and lower molds 11 and 12 are brought close to each other, and the material glass 3a is pressed to start molding (see FIG. 6).

As the molding progresses, the mold shape transfer of the material glass 3a progresses. Although the whole surface transfer of the lower mold 12 is completed first because the material glass 3a hangs downward, the transfer of the upper mold 11 is delayed by that much, and the gas reservoir 15 remains inside (see FIG. 7). Further, as the pressing is further advanced, the gas reservoir 15 is pushed out from the center of the molded product effective diameter portion 11b to the peripheral portion (see FIG. 8) and enters into the groove 11c provided on the molding surface of the upper die 11 (FIG. 9). reference). as a result,
By the pressing force, the volume of the gas reservoir 15 is reduced, and it can be pushed out of the effective diameter of the molding, and the inside of the effective diameter portion 11b of the molded product can be made a good product (see FIG. 10).

According to the present embodiment, since the groove is provided between the molding effective diameter portion and the flat surface portion outside the effective diameter, the minute gas reservoir completely enters the groove and impairs the effective diameter. It is possible to reduce the volume of a slightly large gas pool due to the internal pressure. Therefore, even if the gas reservoir cannot be completely discharged to the outside of the molded product, it can be expelled from the effective diameter portion at least. Further, due to this effect, the molding pressure may be particularly low as compared with the case of Embodiment 1, and the load on the molding apparatus can be reduced.

Furthermore, there is an advantage in that the groove can be simply formed in the die processing, and that the coaxiality can be secured easily by performing it simultaneously with the processing of the molding surface. Moreover, since it is a groove, excess glass does not flow unilaterally during molding to cause clogging, and there is no risk in continuous molding. In addition, since the internal pressure during molding can be increased, the residual gas can move and flow into the voids at high speed.

[0024]

Third Embodiment FIGS. 11 and 12 show the present embodiment, FIG. 11 is a perspective view, and FIG. 12 is a sectional view. In this embodiment, the grooves 11c and 12 of the upper and lower molds 11 and 12 in the first embodiment are
It is different in that it is configured by providing a plurality of auxiliary grooves 11d and 12d communicating with the outer peripheral portion to c, and other configurations are composed of the same components, and the same components are designated by the same reference numerals and the description of the configuration is omitted. To do.

The operation of this embodiment is the same as the operation of the second embodiment described above with reference to FIGS. Then, there is no volume reduction due to the compression of the gas pool in FIG. 10, and the gas causing the gas pool reaches the grooves 11c and 12c,
It is discharged from the outer peripheral portion by the auxiliary grooves 11d and 12d.

According to this embodiment, in the case of a molded product in which the gas pool cannot be sufficiently removed, for example, the molding machine cannot obtain a high pressure or a high pressing speed, and the effects of the first and second embodiments cannot be sufficiently obtained. In this case, since the gas pool can be forcibly removed, the molding pressing force and the molding pressing speed can be relaxed, and the applicable range of the molding machine that can be used can be expanded.

[0027]

In the glass press lens molding, the internal pressure of the lens being molded can be maintained at a high pressure, the occurrence of sink marks can be suppressed, and the flow itself can be completely blocked. I do not leave a gas pool,
As a result, a glass press lens having good surface accuracy can be manufactured.

The effects of claims 2 and 3 are that even if the gas pool is not completely pushed out of the molded product, good surface accuracy as the molded product can be secured, and the molding conditions can be relaxed.
The same effect as can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a first embodiment.

FIG. 2 is a cross-sectional view showing a first embodiment.

FIG. 3 is a graph showing Example 1.

FIG. 4 is a graph showing Example 1.

FIG. 5 is a cross-sectional view showing a second embodiment.

FIG. 6 is a cross-sectional view showing a second embodiment.

FIG. 7 is a cross-sectional view showing a second embodiment.

FIG. 8 is a cross-sectional view showing a second embodiment.

FIG. 9 is a cross-sectional view showing a second embodiment.

FIG. 10 is a cross-sectional view showing a second embodiment.

FIG. 11 is a perspective view showing a third embodiment.

FIG. 12 is a cross-sectional view showing a third embodiment.

[Explanation of symbols]

 1 Upper mold 2 Lower mold 3 Molded lens 4 Transport tray

Claims (3)

[Claims] 1. A glass press molding die having a flat surface portion having a width larger than at least a thickness dimension of an outermost periphery of an effective diameter of a molded product, outside the effective diameter of the molding. 2. The glass press molding die according to claim 1, wherein a circumferential groove is formed between the effective diameter of the molded product and the flat surface portion. 3. A circular groove is formed between the effective diameter of the molded product and the flat surface portion, and an auxiliary groove is formed from the groove to the outer peripheral portion of the molding surface. Glass press mold.