JPS59188601A - Plastic lens - Google Patents

Abstract

PURPOSE:To attach accurately a lens to a lens-barrel by making a part of the flange of the lens to which a gate is bonded thinner and narrower than the other part to prevent deformation during the cutting of the gate and the annealing of the lens and to improve the out-of-roundness of the outside of the lens and the parallelism of the surfaces of the flange. CONSTITUTION:A flange 2 around a lens part 1 consists of a thin part 5 to which a gate 3' is bonded and the other part. The thin part 5 of the flange 2 is made narrower than the other part by a width A and thinner than it by a thickness 2B. Thus, bulging deformation during the cutting of the gate 3' and deformation due to residual stress during the annealing of the lens are prevented, and the out-of-roundness of the outside of the lens and the parallelism of the surface of the flange are improved, so the lens can be accurately attached to a lens- barrel.

Description

[Detailed description of the invention] [Field of application of the invention] The present invention can be carried out by injection molding, injection compression molding, etc.

A brim formed around the outer periphery of the lens.

The gate is bonded to a plastic lens.

Wow, especially regarding the shape of the brim.

[Background of the invention]

In recent years, plastic lenses have come to be used instead of glass lenses as constituent lenses in optical equipment such as lenses for video cameras. The plastic lens is made of polymethyl methacrylate-1.
They are made from thermoplastic plastics such as polystyrene and polystyrene, and are made by injection molding or injection compression molding. This improves productivity compared to glass lenses, making it possible to reduce the cost and weight of lenses.

However, on the other hand, since the plastic material is heated during molding, the generation of residual stress cannot be avoided, and in addition, it is impossible to avoid the generation of residual stress during molding.

To form a lens, clear the lens barrel.

The outer circularity of the lens should be adjusted to minimize the irradiance.

It is necessary to increase it.

When plastic lenses are injection molded, the area where internal stress occurs is positive.

This is near the gate that is integrally coupled to the tick lens.

For this reason, a large amount of residual stress exists near the gate, and when a molded plastic lens is annealed, this residual stress causes deformation in the vicinity of the -gate.

Therefore, in order to eliminate the influence of such residual stress, a collar 2 is provided on the outer periphery of the lens portion 1, as shown in FIG. According to conventional plastic lenses, there is a lot of residual stress in the part where the collar 2 and the gate 6' are joined, but the residual stress in the lens part 1 is extremely small. Therefore, annealing treatment is required.
However, almost no deformation occurs in the lens portion 1. - However, when cutting the gate 3' from a molded plastic lens, the plastic.

The lens was heated to prevent it from cracking.

A tool such as nippers is used, but for this purpose,
As shown in FIG. 6, the cut portion 4 swells and deforms due to heat, and a portion protrudes by α in the width direction and by 6 in the thickness direction from the other portions of the collar 2. will occur.In addition, as shown in Fig. 2.

1 is a plan view of the plastic lens after the gate is cut, and FIG. 3 is a sectional view taken along the dashed line x-, z' in FIG. It's marked 4.

Furthermore, a molded plastic lens has a lot of residual stress near the gate.

When the annealing process is performed, the portion of the collar 2 near the gate is deformed, and the collar portion of this portion of the collar 2 changes.

In this way, changes in the thickness of the edges and edges of the flange near the gate and the curvature of the gate cut portion will impair the flange and, therefore, the roundness of the outer diameter of the plastic lens.
It takes a plastic lens.

A plastic screw when attaching the lens to a lens barrel, etc.

This caused the lenses to become eccentric or fall over.

[Purpose of the invention]

It is an object of the present invention to eliminate the drawbacks of the above-mentioned prior art (i.e., to prevent residual stress in the vicinity of the gate of the collar provided on the outer periphery of the cavity lens portion and the influence of deformation due to gate cutting, thereby improving the roundness of the outer circumference of the lens. - To provide a plastic lens that has significantly improved parallelism on its surface and can be attached to a lens barrel with high precision.

[The Ark of Sophistication]

In order to achieve this object, the present invention makes the part of the collar near the gate joint part thinner than other parts of the collar, in response to the bulging deformation after gate cutting and the deformation due to residual stress during annealing. It is characterized by its narrow width.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

Figure 4 shows a plastic lens invented by He.

A plan view showing one embodiment, FIG. 5 is a dot-dash line x in FIG. 4.
” It is a cross-sectional view along the x line, and 5 is a thin portion.

The parts corresponding to Figure 1 are given the same reference numerals.

In Figures 4 and 5, the lens part 1 is made up of a thin part 5, to which the flange 2 and the gate 3 are connected, and other parts (the outer periphery of the rim is high). The thickness is set to a constant value with high accuracy, and the two surfaces in the thickness direction maintain high parallelism.

On the other hand, the thin part 5 of the collar 2 is narrower by A than the width of other parts of the collar 2 other than the thin part 5, and is thinner by 2B than the thickness thereof. This is A', B is 100
The value is more than μm, and this is the bulging deformation a when the gate is cut, as shown in Figures 2 and 3.
, b are respectively 5o to 1oofim, and there is no other way to prevent deformation due to residual stress during annealing treatment other than removing the residual stress.

That is, considering the bulging deformation of the gate 3 when it is cut and the deformation due to residual stress, the gate 6 is attached at least 10 cltm inward from the outer periphery of the collar 2.

3' is attached to the brim part of the thin wall part 5.

It is made 200μm or more thinner than the other parts of 2.

be.

As mentioned earlier, residual stress is caused by gate 3' (Figure 4).
The degree of residual stress due to photoelasticity is measured, and depending on the spread of the residual stress, part or all of the thin wall portion 4 is quickly cut with a tool heated to around 200°C.

Fig. 6 is a plan view showing the plastic lens after the gate has been cut in this way, and Fig. 7 is a dotted chain line x in Fig. 6.
4 is a sectional view taken along the line -x, where 4 is a bulge, and parts corresponding to those in FIG. 4 are given the same reference numerals.

In FIG. 6, a bulge 4 is formed in the thin part 5 due to the gate cutting of the thin part 5, but since the deformation in the radial direction of the lens is less than 100 μm, the bulge 4 protrudes from the surface including the outer peripheral surface of the collar 2. There is nothing to do, and the bulge 4
The thickness of the brim 2.

Since the deformation in the direction is less than 200 μm, there is no protrusion from the surface including the surface of the collar 20.

In this way, the plastic lens after cutting the gate 3 has no undesirable protrusions or protrusions, and since a heated tool is used to switch the gate 3, the thin part 5 is Since it is heated, almost all residual stress in the thin portion 5 is removed, and almost no annealing deformation occurs even after annealing. Therefore, it is possible to obtain a high-precision plastic lens that can be incorporated into a lens barrel with minimal clearance without eccentricity or tilting.

〔Effect of the invention〕

As explained above, according to the present invention, the outer diameter roundness and the edge of the brim can be improved without being affected by bulge deformation when cutting gouts or deformation due to residual stress during annealing. The thickness can be maintained with high precision, and a plastic lens with excellent functionality can be provided without the drawbacks of the prior art described above.

[Brief explanation of drawings]

Figure 1 shows an example of a conventional plastic lens. The plan view shown in Fig. 2 is the plastic layer shown in Fig. 1. 3 is a sectional view taken along the dashed line χ-r' in FIG. 2; FIG. 4 is a plan view showing an embodiment of the plastic lens according to the present invention; Figure 5 is a sectional view taken along the dashed-dotted line x-x... in Figure 4, Figure 6 is a sectional view of the plastic lens in Figure 4 after the gate is cut, and Figure 7 is a point taken in Figure 1. It is a sectional view along the individual lines x- and r'. 1... Lens portion 2... Brim 3... Gate 4... Swelling part 5... Thin wall part Fig. 7, Fig. 4, Fig. 6 Figure 2, Figure 7, procedural amendment (voluntary) 1, 587, 4]?lft correction person 1, pa 1, = Ray furnace patent applicant r + r 5, 5 :, r)
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A column for a brief explanation of the drawings in the specification. that's all

Claims (1)

[Claims] In a plastic lens obtained by injection molding, injection compression molding, etc., a buckle is provided on the outer periphery of the lens part, and a gate is coupled to the collar, and the collar is
．． It consists of a thin and narrow first part connected to the gate and a thick and wide second part excluding the first part, which bulges and deforms when the gate is cut and is heated. The first part deformed during processing is the 20th part.
A glass lens characterized in that it is configured to be able to prevent protrusion from a surface including the surface of a portion.