JPH02157130A - Lens forming mold and lens formed by this mold - Google Patents

Abstract

PURPOSE:To prevent the cracking, etc., of the press-formed lens in the cooling stage by providing an escape part of specified shape for a surplus glass material on the periphery of a cavity forming an optical nonfunctional surface. CONSTITUTION:The forming mold consists of an upper mold 2, a lower mold 3, and a barrel mold 4 on an annulus ring, and the forming surfaces 2a and 3a of the upper mold 2 and lower mold 3 are specularly finished in the specified shapes corresponding to the functional surface of an optical lens to be formed. The escape part 5 is formed on the inner periphery of the upper end of the barrel mold 4. The depth of the groove of the escape part 5 is progressively decreased from the inner peripheral side toward the outer peripheral side. The glass formed in the escape part functions as the nonfunctional surface of an optical lens. When the optical lens is formed using the forming mold, the upper mold 2 is raised, softened glass material is placed on the lower mold 3, then the upper mold 2 is lowered, and the upper mold 2 is pressed for a time necessary to transfer the shapes of the forming surfaces 2a and 3a to the glass material 14. The whole mold is then cooled as such, the upper mold 2 is raised, and the glass formed product 6 is taken out.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention (j, lens molding by breath molding II, I
Regarding I and the lens molded by this mold, 1, more specifically, the lens molding mold and the lens molded by this J-ri do not cause defects such as cracks in the molded lens during the cooling process after press molding. Regarding lenses.

(Prior art) In recent years, high precision has been achieved, which eliminates the need for post-processing such as grinding and polishing, by housing a glass material in a molding nozzle 4 that achieves a predetermined surface accuracy and press-molding it. Methods for forming optical elements have been developed.

This type of molding method will be explained using FIGS. 3 and 4. Figure 3 shows the state in which the softened glass material is accommodated in the mold and press molded, and Figure 4 shows the state in which the softened glass material is housed in the mold.
For molding shown in the figure! A cross-sectional view of a glass molded product formed by jQ is shown.

For molding shown in the figure 1. F9 consists of an upper mold 1 (3), an upper mold I7, and a working mold 18, and each of the molding fabrics 16a, 7a of the upper mold 16 and upper mold I7 is mirror-finished with high precision. The softened glass material 14 is supplied to the upper mold 171 of this molding mold 17, and then the first mold 16 is lowered and pressed with the pressure rod 15.Then, the stiffness suppressed state is maintained on the molding surface. 16a, I7a is held for a sufficient time to transfer the surface shape to the glass material 14, and then the mold body is cooled as it is, and then the 1-mold 16 is upper bound to form the glass molded product 1.
Take out 4a.

By the way, the glass material supplied for such breath molding! Since there is some variation in the amount of n, in order to obtain a glass molded product with a constant weight, a relief part 13 is provided on the inner periphery of the upper end of the mold 18 to release the excess glass material 19, and the press molding is performed within this relief part. The weight of the glass molded product is adjusted by extruding the surplus glass material 19 that is generated at the time. Incidentally, the surplus portion of the outer periphery of the glass molded product constitutes a functional surface that does not need to function optically, and can be used, for example, as a holder for an optical lens.

(Problem to be Solved by the Invention) The molded lens formed in this way has a molding surface 162
It has an optically functional surface 14F) formed by suppressing transfer of materials 1 and 17a, and an optically functional surface 9a formed by surplus glass material 19 on its outer periphery. However, 11. The molded product has functional aspects 14) and J1.
A crack 20 may appear at the boundary 202 with the functional surface 192.

As for the cause of this, the present inventor "9" found that during cooling after press molding, a force that tries to shrink the glass material body in the housing 1 (inner glass body 1) toward the center is exerted, but the excess that is extruded into the relief part 1: The glass material 19 cannot follow the shrinkage of the glass material between the first mold 16 and the upper mold 17, and as a result, tensile stress concentrates on the boundary portion 20 where the stress is the weakest, causing a local fracture field in that portion. There was one thing I could think of.

Such a phenomenon is particularly noticeable in the case of a lens shape in which the thickness of the surplus glass material increases from the inner circumferential side to the outer circumferential side, and may also occur in the case where the thickness of the lens is A.

(First Step to Solve the Problems) The problems mentioned above are as follows: 1. The lower mold for press-molding a glass material in the present invention; ' I (II, or 1) 1. In a mold consisting of a mold and a working mold, 1) 11
A relief portion for the surplus of the glass material is provided on the outer circumferential portion of the groove forming an optically non-functional surface, and in this relief portion, there is provided a gap between the IL1 and the lower mold 111f or between the upper mold 11iI and the [1; 1. A mold for molding a lens, characterized by having a shape in which the gap between 11 and 11 including the body mold described in 1.1 gradually decreases, and 1.
j'l i! (g) A lens characterized in that the thickness of the optically non-functional surface formed by molding the surplus portion of the glass element H by the relief part of the molding mold gradually decreases from the inner circumferential side to the outer circumferential side. resolved.

(Function) - In the mold for molding the lens of the present invention, such as uL, the relief part from which the excess glass material is extruded during pressing is the outer periphery of the cavity between 1., 41; 17 and the lower mold. The part formed by this relief part functions as the J+441 function 1n1 of the lens.Therefore, the relief part of -11 is set as -5, If, between the mold and the -14 mold. By creating a shape in which the gap gradually decreases at the bottom of the lens, the j′μ distance formed by this relief part gradually decreases from the inner circumference to the outer circumference, and the glass material is easily follows the concentration #ii in the central part of the functional surface and the boundary between the functional surface and the 11- functional surface. There will be no cracks in the parts.

(Embodiment 'J) Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a cross section of a lens molded piece +31 according to the present invention (see FIG. 11), and FIG. 2 shows an optical lens molded using the mold shown in FIG. 1.

The molds shown in FIG. 1 are 1 mold 2 and 1. 'IF:
3 and an annular body J1!4, each of the molding surfaces 2a, 3; Visit 1
has been done.

Further, a relief portion 5 is formed on the inner periphery of the upper end portion of the 1Ili11' entry 94. The relief portion 5 is shaped such that the groove depth gradually decreases from the inner circumferential side toward the outer circumferential side. Is the glass formed in this relief part a light'? Acts as a non-functional surface of the lens.

To press mold an optical lens using this mold, first mold the upper mold 2, place the softened glass material in the lower mold 3-4, and then press the mold 2 into the lower mold 3-4. The shape of 2a and 3a before molding is the glass material 14.
After pressing the mold for a sufficient period of time to transfer the image to
Take 1] 4. In this way, a small glass molded article 6 as shown in FIG. 2 is obtained.

G, J: Tuna The mold for molding in this example is an optical lens 6.
1. The depth of the groove of the relief part 5 forming the innocent function 61) is shaped so as to gradually decrease from the inner side +r+i to the outer surface, and moreover, from the relief part 5 to 4+, IJ.

: Since the shape is smooth from 3a before molding in step 3, when the glass in the mold as a whole contracts toward the center as it cools after press molding, the movement of the glass during this contraction is not hindered. , it is possible to easily follow the shrinkage of the glass between 2a and 3a before molding, create an IH7 lens without stress concentration at the boundary part 62], and without cracks in that part.

In addition, the mold for molding the saiki is -1-4 (su, 1.'If
;! Although it is composed of a mold and a mold, it is also possible to use a mold that has the function of a mold for the mold and form a relief part as shown in (1). , the effect will not change no matter how much effort you put into it.

More specific embodiments of the present invention will be described below.

1-For molding shown in Example (11J), 1.
, Curvature of 2a before molding of Ijli2 ゛I' diameter 17: 3
1.5mm, lower mold 3 molding ITI! 3. The radius of curvature R of a is 19.5 mm, the outer diameter of the do J~92 is 20 mm, and the edge of the mold 4-1 when the The width between the innermost circumference 5a of the relief part 5 and the mold 2 is 1.2 mm, the width with the outermost circumference 5b of the relief part 5 is 1'', and the width with the mold 2 is Omm. Using s r;' s as, this diameter is 8 mm
A spherical material of
Heat to 40 °C and add 1 part of I-be (1 part of 2 to 50
After applying a pressure of 0 Kg and pressing for 3 minutes, the mold was left as it was to cool the entire mold, thus obtaining the desired optical lens 6.

i-? No cracks were observed at the boundary 6a between the functional surface and the non-functional surface of the optical lens obtained, and the properties of the functional surface were also good.

By the way, 1. The innermost part of the relief part 5 of the mold 4 when the upper mold 2 of the molding mold contacts the upper end of the body 5
The width with the upper mold 2 at a is 1.2 mm, and the width with the upper mold 2 at the outermost periphery 5b of the relief part 5 is 1.3 mm.
When press molding was carried out under the conditions stated in ``-'',
Cracks were generated at the boundary portion 6a of the obtained optical lens.

Here, in the mold shown in FIG. 1, the diameter between the outermost circumference of the relief part is F), the diameter between the innermost circumference of the relief part is D', and the Iz mold 2 is in contact with one end of the mold 4. In this case, the width of the innermost peripheral part 5a of the relief part 5 is ``1'', the width of the outermost peripheral part 5b of the relief part 5 is ``■'', and the radius of curvature of the optical functional surface of the second type 2 is 31.
．． 5mm, and the radius of curvature of the optical functional surface of lower mold 3 is 19.5m.
For this molding as m! , F: i-C Result of crack occurrence when press molding was performed on the glass material shown in the above example (distinguished by whether there is a crack or not)
are listed in Table 1.

In addition, in this table, the reduction rate indicated by * is -11"
-1"NiniL/tar(+) -1)")/2, the number 41'j, that is, the non-functional surface 6 of the lens 6 [
) is the rate at which the lens thickness gradually decreases from the inner circumferential side to the outer circumferential side.

(Effects of the Invention) As explained above, according to the lens mold of the present invention, when the glass material shrinks during cooling after pressing, the excess portion of the glass material that is molded at the relief part is removed. Because it contracts and moves smoothly, stress concentration does not occur at the boundary between the functional and non-functional surfaces.

Furthermore, the lens obtained using such a mold has no defects such as cracks at the boundary between the functional surface and the non-functional surface, and can be used as an optical lens with good surface precision.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of the lens molding mold of the present invention, Fig. 2 is a molded lens molded into the mold shown in Fig. 1, and Fig. 3 is a molded lens softened by a press molding device. FIG. 4 shows a cross-sectional view of a molded lens molded by the molding apparatus shown in FIG. 3. I 2...- to mold 3...lower mold 4...mold 5...relief part 5a...innermost peripheral part 5 of the relief part b...outermost peripheral part 6 of the relief part ...Molded lens 6a...boundary part

Claims (2)

[Claims] (1) In an upper mold and a lower mold for housing and press-molding a glass material, or in a mold consisting of an upper mold, a lower mold, and a body mold, the excess relief portion of the glass material is used as an optically non-functional surface. Molding of a lens, characterized in that the gap between the upper die and the lower die or the gap between the upper die and the lower die including the body die in the relief part is gradually decreased. Usage type. (2) The thickness of the optically non-functional surface formed by molding the surplus portion of the glass material by the relief portion of the mold described in claim 1 has a shape in which the thickness gradually decreases from the inner circumferential side to the outer circumferential side. A lens characterized by: