JPH06127957A - Mold for molding glass lens - Google Patents

Abstract

PURPOSE:To provide a mold for molding the glass lens which can prevent harmful reflection even if the molding surface of the glass lens is not provided with a recess of a special shape and which is effective against a lens of various shapes. CONSTITUTION:A part of the projecting part 1a of an upper mold 1 is constituted to the diameter smaller than the diameter of the projecting part 1a of a lower mold 6. A ring 4 sliding in the longitudinal direction of the upper mold 1 is inserted into the upper mold 1. This ring 4 is constituted of a Cr2O3 blank material having the coefft. of linear expansion smaller than the coefft. of linear expansion of the upper mold 1 and the lower mold 6. An annular piece 5 in contact with the non-effective diameter part of the glass lens 3A is fitted into the upper mold 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold for molding a glass lens, and more particularly to an improvement of a mold for facilitating the mold release from the lens by a mold molding method for a lens. is there.

[0002]

2. Description of the Related Art Various conventional lens forming methods are conceivable. One of them is to heat a pair of molds and a glass material to a temperature at which the glass material softens, and then to form a pair of molding materials. A mold is pressed to form a glass lens from a glass material, and then a pair of the mold and the glass lens are cooled to a temperature near or below the glass transition temperature and released from the mold, and the mold is removed from the glass lens. There is known a molding method of taking out.

However, although the above-described lens molding method does not cause much problems in molding convex lenses, it causes the following major problems in molding concave lenses.

That is, when a concave lens having a concave surface is molded, a difference in shrinkage is inevitably generated between the mold and the glass lens during cooling. It had to occur between the lens. For this reason, the glass lens inevitably adheres to the molding die, resulting in a great problem that the releasing operation becomes very difficult.

In view of the above, Japanese Patent Laid-Open No. 218932/1993 proposes a plurality of recesses for molding projections on the convex molding surface of a mold for molding the ineffective diameter portion (peripheral portion) of a glass lens. It is configured to be recessed at a depth of 0.5 μm to 0.2 mm.

In this way, due to the difference in linear expansion coefficient between the molding die and the glass lens during cooling, the projections of the glass lens closely fitted in the plurality of recesses deviate from the depressions and become out of alignment with the molding die. A gap for allowing air to flow in is formed between the glass lens and the above-mentioned problem.

[0007]

The conventional lens molding method is as described above, and a plurality of recesses are provided in the outer effective diameter portion of the convex molding surface of the molding die in order to facilitate the releasing work. Therefore, there is a drawback that the outer diameter of the lens becomes larger than necessary. Further, even if a plurality of recesses are provided in the outer portion of the effective diameter, the recesses have a drawback that they cause harmful reflection. Further, the molding method disclosed in the above publication cannot be expected to have a great effect on a hemispherical spherical lens having a small radius of curvature.

Further, in the molding method of the publication, the molding surface of the molding die is limited to the convex surface, but the glass lens is often attached to the concave molding surface. In particular,
This adhesion was very likely to occur when the coefficients of linear expansion of the mold and the glass lens were almost the same.

[0009] For example, mold material is Cr ₂ O ₃ (coefficient of linear expansion ^{7.3 × 10 - 6 / ℃)} , glass material ZnSF8 (trade name suitable for pressing; Sumita Optical Glass, linear expansion coefficient of 6 × 10 ^-6 / ° C), there is a difference in shrinkage between the mold and the glass lens during cooling.
A space with a substantially crescent-shaped cross section sealed under negative pressure had to be generated between the center of the mold and the glass lens. Therefore, the glass lens inevitably adheres to the molding die, which makes the release work extremely difficult.

The present invention has been made in view of the above, and it is possible to prevent harmful reflection without forming a specially shaped recess on the molding surface of the lens, and moreover, it is effective for lenses of any shape. It is intended to provide a mold for molding a lens.

[0011]

In order to achieve the above object in the present invention, a glass material is interposed between a pair of molds facing each other and the molds are pressed to form a glass lens from the glass material. In what is molded, one of the pair of molds is configured to have a diameter smaller than that of the other mold, and a ring that slides in the longitudinal direction of the one mold is inserted into the one mold, This ring is composed of a member having a linear expansion coefficient smaller than that of the mold, and a ring-shaped contact member for contacting the non-effective diameter portion of the glass lens is fitted into the one mold. There is.

[0012]

According to the present invention having the above structure, the coefficient of linear expansion of the ring is made smaller than that of the die or the contact member, and the ring is provided between the die and the contact member. Since the ring is interposed, the ring presses the non-effective diameter portion of the glass lens downward through the contact member during cooling, and the glass lens is easily separated from one mold or another mold due to this pressing action. Typed.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on an embodiment shown in FIGS. The glass lens molding die according to the present invention is configured such that the upper die 1 has a diameter smaller than that of the lower die 6.
The ring 4 is inserted into the upper mold 1 and the ring 4 is made of a material having a linear expansion coefficient smaller than that of the upper mold 1 and the lower mold 6, and the top 5 is fitted in the upper mold 1. There is.

As shown in FIG. 1, the above-mentioned upper die 1 is formed in a substantially convex shape in cross section, and a convex portion 1a directed in the vertical direction is formed in a cylindrical shape, and this convex portion 1a is a cylindrical body. It is fitted in the mold 2 so as to be vertically movable from above.

The convex portion 1a, which is in sliding contact with the inner peripheral surface of the barrel die 2, has a convex lower surface polished to form a smooth cavity surface 1b. Have

Further, as shown in the figure, a part of the convex portion 1a directed vertically downward is formed to have a diameter smaller than that of the lower mold 6 so as to mold only the effective diameter portion of the glass lens 3A.
The ring 4 and the top 5 are loosely inserted into the reduced-diameter convex portion 1a,
Or it is inserted.

As shown in FIG. 1, the loose ring 4 is formed in a ring shape having a diameter larger than that of the convex portion 1a having a reduced diameter in consideration of the body expansion coefficient of the upper mold 1, and the vertical direction in FIG. It has a length of 10 mm. Then, the protrusion 1a having a reduced diameter is vertically movably (slidingly) inserted through a slight gap, and is interposed between the enlarged portion of the protrusion 1a of the upper die 1 and the top 5. It is arranged.

As shown in the figure, the top 5 for sandwiching the ring 4 with the convex portion 1a of the upper die 1 is made of the same material as the upper die 1 in a ring shape, and has a reduced diameter convex portion 1a. And is overlapped with the lower surface of the ring 4 and has a function of molding the ineffective diameter portion (peripheral portion) of the glass lens 3A during pressing.

As shown in FIG. 1, the lower mold 6 is formed of the same material as the upper mold 1 into a convex shape, and a convex portion 6a directed vertically upward is formed in a cylindrical shape. Part 6
A is fitted in the body mold 2 so as to be vertically movable from below.

The convex portion 6a that is in sliding contact with the inner peripheral surface of the barrel die 2 is formed by polishing the concave upper surface into a smooth cavity surface 6b. This cavity surface 6b functions to mold the glass lens 3A from the glass bump 3. Run.

Further, the convex portion 6a directed vertically upward has a larger diameter than that of the convex portion 1a of the upper mold 1 so as to mold the non-effective diameter portion (peripheral portion) of the glass lens 3A as shown in FIG. And the top 5 of the upper mold 1 which is located directly above
And are arranged to face each other.

However, between the cavity surfaces 1b and 6b of the upper mold 1 and the lower mold 6, a substantially spherical glass cob 3 is disposed so as to intervene at the time of pressing. Is rolled and deformed.

Next, with reference to FIGS. 1 to 3, a detailed description will be given of a molding example in which the glass mold 3 is used to mold the glass lens 3A from the glass bump 3, but before that, the molding example is used. Materials and the like of the upper mold 1, the lower mold 6, the top 5, the ring 4, and the glass humps 3 will be described.

The upper mold 1 and the lower mold 6 used in this molding example are C
r ₂ O ₃ (coefficient of linear expansion 7.3 × 10 ^{- 6} / 100~30
0 ° C).

Further, Si ₃ N ₄ (linear expansion coefficient 3.1 × 1
0 ^{- 6} / 100~300 ℃) configured ring 4 running through the upper mold 1 from being in use.

[0026] Then, the frame 5 is fitted into the upper die 1, Cr ₂ O ₃ is the same material as the upper die 1 and lower die 6 (linear expansion coefficient of ^{7.3 × 10 - 6 / 100~300 ℃} ) It consists of

Further, the glass bump 3 used in this molding example.
Is composed of PBK40 (trade name; Sumita Optical Glass), its transition point (Tg) is 501 ° C., and its yield point (A
t) is 549 ° C.

In order to mold the glass lens 3A from the glass mound 3 using the molding mold, first, the glass mound 3 is set between the upper mold 1 and the lower mold 6 in nitrogen (not shown), and the glass mould 3 is set. Is heated to be softened, and the upper mold 1 and the lower mold 6 are pressed at a temperature of 580 ° C. for 5 minutes while applying a pressure of 50 Kgf / cm ³ to mold the glass lens 3A (see FIG. 1).

At the time of this molding, the upper die 1, the top 5 and the lower die 6
The glass lens 3A and the glass lens 3A are in close contact with each other as shown in FIG.

After the glass lens 3A is molded in this manner, the glass lens 3A is expanded while the pressing pressure is reduced.
Is cooled together with the upper mold 1 and the lower mold 6, and the glass lens 3A is taken out when the temperature reaches 350 ° C.

The glass lens 3A enters a solidified state when it reaches a temperature of 530 ° C. (see FIG. 2).

During the above cooling operation, the expanded ring 4 and the upper mold 1 are
And the top 5 respectively contract, but at the time of this contraction, when the contraction amount between the upper mold 1 and the top 5 exceeds a predetermined cooling temperature, the contraction amount increases as compared with the contraction amount of the ring 4, and the ring 4 and the upper mold 1 and the frame 5 respectively. There is a difference of 7.3 μm per 5 mm and 10 mm (length of ring 4).

That is, the shrinkage ratio of the ring 4 is 10 × 3.1 × 10.
^{- 6 × 180 ℃ = 5.6 ×} 10 - ³ is the relative shrinkage of the upper die 1 and frame 5 is ^{10 × 7.3 × 10 - 6 ×} 1
Since 80 ° C. = 13.1 × 10 ⁻³ , the above-mentioned 10
The difference in shrinkage per millimeter is expressed as the difference in elongation of 7.3 μm.

Note that 180 ° C. is a difference obtained by subtracting the take-out temperature (350 ° C.) of the glass lens 3A from the solidified temperature (530 ° C.) of the glass lens 3A.

However, since the ring 4 has a small coefficient of linear expansion, the amount of shrinkage is smaller than the amount of shrinkage between the upper die 1 and the top 5, and as described above, there is a difference in elongation of 7.3 μm. generate.

Therefore, the vertical direction of the ring 4 is 7.3.
The periphery of the glass lens 3A, which is the non-effective diameter portion of μm, is pressed downward through the top 5 during cooling (see FIG. 3),
With this pressing action, the glass lens 3A is easily released from the upper mold 1 and the lower mold 6.

According to the above construction, the coefficient of linear expansion of the ring 4 is made smaller than the coefficient of linear expansion of the upper die 1 and the top 5.
Is interposed between the expanded portion of the convex portion 1a of the upper mold 1 and the top 5, the ring 4 presses the ineffective diameter portion of the glass lens 3A downward through the top 5 during cooling, With this pressing action, the glass lens 3A is easily released from the upper mold 1 and the lower mold 6.

Therefore, it is not necessary to form a plurality of depressions, and it is possible to prevent the possibility of harmful reflection due to the presence of the depressions. Further, as described above, since it is not necessary to form a recess having a special shape on the molding surface, it is possible to easily release the glass lens 3A having any shape. It should be noted that these various effects can be sufficiently achieved if the difference in shrinkage is 3 μm or more.

In the above embodiment, the upper die 1 is provided with the ring 4 and the top 5.
The lower mold 6
Alternatively, the ring 4 and the top 5 may be loosely inserted or fitted. Further, even if the shapes and the locations of the rings 4 and the tops 5 are appropriately changed, the same operational effects as those of the above embodiment can be obtained.

[0040]

As described above, according to the present invention, it is possible to easily make a glass lens from one mold or another mold without impairing the surface accuracy by utilizing the difference in shrinkage between the mold and the ring during cooling. Since it can be released from the mold, it is not necessary to form a plurality of recesses, and it is possible to reliably prevent the possibility of harmful reflection due to the existence of the recesses. There is a remarkable effect that it can be implemented without doing.

The convex, concave, and
Alternatively, there is a special effect that it is possible to easily release a glass lens of any shape such as a flat surface. Further, it is possible to exert a great effect even in mass production using an autoder.

[0042]

[Brief description of drawings]

FIG. 1 is a sectional explanatory view showing an embodiment of a glass lens molding die according to the present invention.

FIG. 2 is a cross-sectional explanatory view showing a solidified state during molding in a glass lens molding die according to the present invention.

FIG. 3 is an explanatory cross-sectional view showing a released state of the glass lens molding die according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Upper mold (one mold), 1a ... Convex part, 3 ... Glass bump (glass material), 3A ... Glass lens, 4 ... Ring, 5 ... Coma (contact member), 6 ... Lower mold (other mold) .

Claims (1)

[Claims] 1. A mold for molding a glass lens, wherein a glass material is disposed between a pair of molds facing each other, and the mold is pressed to mold a glass lens from the glass material.
One of the pair of molds is configured to have a diameter smaller than that of the other mold, and a ring that slides in the longitudinal direction of the one mold is inserted into the one mold, and the ring is formed in the mold. Of a glass lens characterized by comprising a member having a linear expansion coefficient smaller than the linear expansion coefficient of No. 1, and a ring-shaped contact member for contacting the non-effective diameter portion of the glass lens is fitted into the one mold. Mold for molding.