JPH02234103A - Resin cemented type aspherical lens - Google Patents

Abstract

PURPOSE:To form a thin resin molding layer in a desired aspherical surface shape directly on the surface of a glass lens which forms a principal part by setting the thickness of the center part of a 1st resin molding layer less than that of a 2nd resin molding layer. CONSTITUTION:The 1st layer 1 and 2nd layer 3 are formed on the R2 surface (close to a desired aspherical surface) of the glass lens 1, which is ground to, for example, a 2mm center thickness so that the concave surface has 20mm curvature and the R2 surface (convex surface) has 70mm curvature. Then the 1st layer 2 formed on the R2 surface side of the glass lens 1 is 10mum thick at the center part and 200mum thick at the peripheral part. The 2nd layer 3 formed on the 1st layer 2 has nearly uniform thickness on the whole and is 30mum thick at both the center and peripheral part. Namely, the 2nd layer 3 is 1/3 time as thick as the 1st layer 2 at the center part. Consequently, the shape error of the surfaces can be made small and the overall thickness can be reduced, so the shape error of the surfaces is prevented from increasing.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a resin-bonded aspherical surface formed by directly molding a thin resin molded layer having a desired aspherical shape on the surface of a glass lens that constitutes the main part. Regarding lenses.

[Conventional technology]

Lenses used in optical products such as cameras and microscopes are
Glass lenses are mainly used.

Glass lenses have the desired curvature, surface error, and surface roughness by machining a glass block (called a lens blank) press-formed from molten glass through processes such as rough grinding, fine grinding, and polishing. manufactures lenses.

On the other hand, methods have also been put into practical use in which resin lenses are manufactured using methods such as press molding, injection molding, and casting, using resin instead of glass. With this method, once a mold is made, it can be used to mass-produce a large number of lenses.
It is characterized by low manufacturing cost.

However, resin lenses have a fatal drawback in that their optical performance fluctuates greatly due to temperature changes, so they are not used in precision lenses.

On the other hand, there are lenses called aspherical lenses, which are highly used because they have excellent performance that cannot be obtained with spherical lenses.

Since this aspherical lens is not a spherical surface, if it were to be manufactured from glass, it would have to be manufactured one by one by processing lens blanks with a grinding machine. Therefore, the manufacturing cost is considerably higher than that of a spherical lens.

Therefore, a spherical lens made of glass, which is the main part, is manufactured in advance, and a molten resin, heptanomer, or curable resin is sandwiched between this lens and a "mold having a surface that is inverted from the desired aspheric surface." A resin-bonded aspherical lens has been proposed in which a thin resin molded layer having a desired aspherical surface is molded and bonded on the spot by solidifying, polymerizing, or curing the resin.

For example, the invention disclosed in Japanese Patent Application Laid-Open No. 60-56544 is one of them. In this invention (hereinafter referred to as prior art), the resin molding layer is formed by forming a relatively thick first resin molding layer (hereinafter referred to as the first layer) directly on the glass lens surface, and It is composed of two layers: (1) a second resin molded layer (hereinafter abbreviated as "second layer") having a relatively thin desired aspherical shape;

The reason for this is that it is currently impossible to obtain an ideal resin that has low shrinkage strain during curing, high weather resistance, and high hardness; It is still possible to obtain resin (2) and resin (2) with high weather resistance and high hardness. The advantage of using ideal resins is to use a large amount of the former (1) resin for the first layer, which is the inner layer, to form a thick layer. This is because we want to achieve this.

By the way, in the prior art lens, the first layer is formed thicker than the second layer, and therefore the thickness at the center is also thicker than the first layer.
The thickness of the layer is thicker than the second layer (see Figure 2).

However, it is desirable that the thickness of the resin molding layer be as thin as possible for the following reasons: (1) the amount of distortion during curing is large, and (2) hardness, temperature-resistant optical properties, and durability are inferior to glass.

In particular, when trying to reduce costs by using only one type of resin, it is inevitable that (1) a resin with low shrinkage distortion during curing and (2) a resin with high weather resistance and high hardness. In the end, such a resin has a shrinkage upon curing that is lower than that of the prior art.
be larger than that of the layer. When using such resin,
In particular, shape errors become large.

Generally, the surface shape of an aspherical lens deviates from the spherical surface more toward the periphery, so in a resin-bonded aspherical lens,
The resin molding layer is thicker at the periphery and thinner at the center.

Therefore, if an attempt is made to make the entire resin molded layer thinner, the central portion will inevitably become even thinner (for example, 40 μm or less). Therefore, according to the prior art, the second layer, which is thinner than the first layer, must be formed extremely thin, for example to a thickness of IO μm or less.

[Problem to be solved by the invention]

However, experiments have shown that there is a limit to how thin the film can be made due to moldability issues. The moldability problem is the next problem that occurs when resin is dropped onto a glass lens or a mold and the distance between the glass lens and the mold is narrowed.

(1) Since the amount of resin is small, it takes time to spread throughout the gap between the glass lens and the mold, so the pressure to push the glass lens or mold from one side to the other is increased, causing the glass lens to deform and shape. The error will become large.

(2) The thickness of the second layer with a uniform thickness is 20 μm or less, especially I
If the thickness is less than 0 μm, bubbles will easily enter the resin, and it will also be difficult to remove the bubbles that have entered.

[Means to solve the problem]

Therefore, as a result of intensive research, the inventors first found that
The second layer has a substantially uniform thickness and is relatively thick (e.g. 20 μm).
If molded (as described above), problem (2) above will be solved.Secondly, in that case, the first layer must be molded extremely thin, but even if it is extremely thin, it will only be in the center. Since the thickness of the peripheral part is at least 50 to 200 μm, the amount of resin is large, so the above problem (1) can be solved.Moreover, even if the shape error of the first layer is large, It has been found that since the second layer is formed, there is no problem, and based on these findings, the present invention has been accomplished.

Therefore, the present invention provides: - A glass lens (1) having an R2 surface made of an aspherical or spherical surface that approximates a desired aspherical surface; In a resin-bonded aspherical lens consisting of a thin first layer (2), and a second layer (3) molded directly thereon, the second layer has a substantially uniform thickness and has a desired aspherical shape. , provides a lens characterized in that the thickness of the first layer (2) at the center is thinner than that of the second layer (3).

[Effect]

The R2 surface on which the resin layer of the glass lens, which forms the main part, is placed is,
It may be an aspherical surface or a spherical surface that approximates the desired aspherical surface. The reason why an aspherical surface may be used is that although it is made of glass, the manufacturing cost will not be so high if the processing accuracy can be rougher than desired.

The manufacturing method of such an aspherical or spherical glass lens is as follows:
This is already known and can be easily manufactured using commercially available lens grinding machines, lens polishing machines, etc.

In order to manufacture the lens of the present invention, for example, in the first step, molten resin, monomer, or curable resin is sandwiched between the glass lens and "a mold having a surface opposite to the desired aspheric surface." , and then solidify, polymerize or harden it to form a first layer with a relatively thin center part,
In the second step, the obtained semi-finished product is again sandwiched between the first layer and "a mold having a surface opposite to the desired aspherical surface", and then the molten resin, monomer or curable resin is sandwiched, and then By solidifying, polymerizing, or hardening it, a second layer having a relatively thick central portion and a substantially uniform thickness may be formed.

The thickness of the first layer is generally preferably 0 to 30 μm at the center, and the thickness of the second layer is generally 20 to 50 μm, particularly 25 to 30 μm.
35 μm is preferred. The total thickness of the first and second layers is 30
~50 μm is preferred.

There are mainly two ways to provide the first and second layers with a predetermined thickness: (1) A glass lens (or semi-finished product) and a mold are fixed in advance at a predetermined interval, and the gap between the two is fixed. (2) Place a predetermined amount of resin on one side of the glass lens (or semi-finished product) or mold, and then place the resin on the other side to prevent the resin from escaping. There are methods of pressing (press molding, etc.).

It is preferable to subject the glass lens to silane coupling treatment in advance, since this increases the adhesion with the first layer.

Examples of resins used include thermoplastic resins such as polymethyl methacrylate (acrylic resin), thermoplastic polyester, polyvinyl chloride, polystyrene, and polycarbonate, and monomers used include methyl methacrylate, ethyl methacrylate, methyl acrylate, and ethyl. Acrylates, acrylates such as butylacrylate-1, acrylic acid, ethylenically unsaturated monomers such as styrene, butadiene, divinylbenzene, etc. Curing resins used include epoxy resins, unsaturated polyesters, polyurethanes, ultraviolet curable resins, etc. Examples include thermosetting resins.

The resins in the first layer and the second layer may be of the same type or different types, but it is preferable that the resins have the same or similar physical properties such as refractive index, dispersion coefficient, and coefficient of thermal expansion. This is because if the refractive index and dispersion coefficient differ, optical performance will deteriorate due to refraction or reflection of light at the interface between the first layer and the second layer, and also, if the coefficient of thermal expansion differs, it will take a long time. When used, it seems to peel off at the interface.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

〔Example〕

FIG. 1 is a partial cross-sectional view of the resin-bonded aspherical lens (concave lens) of this example. Two layers 3 are formed in sequence.

The glass lens 1 has an outer diameter of 30 mm, a center thickness of 2 a+m, an Rl surface (concave surface) with a curvature of 20 mm, an R2 surface (convex surface) with a curvature of 70 mm, and both surfaces are polished.

The first layer 2 formed on the R2 surface (convex surface) side of the glass lens 1 has a thickness of 10 μm at the center and a thickness of 2 μm at the periphery.
00 μm.

The second layer 3 molded on the first layer 2 has a substantially uniform thickness throughout, with the thickness at both the center and the periphery being 30 μI.

In other words, when comparing the thickness at the center, the second eyebrow 3 is the same as the first eyebrow.
It is 1/3 thinner than layer 2.

Next, the manufacturing process of this resin-bonded aspherical lens will be explained.

First, a glass lens 1 having the above-described shape is prepared, and its R2 surface is subjected to silane coupling treatment.

This lens 1 is centered in advance.

Separately, a mold 4 is prepared which has an inner surface that is inverted from the desired aspherical surface and whose shape error is 0.1 μm or less, which is smaller than the desired value.

This mold 4 is centered in advance.

First step: As shown in FIG. 2, a mold 4 is dropped into a cylindrical jig 5.

2nd step: Apply the product name Aronix UV on top of the mold.
Drop 30 mg of ultraviolet curable resin m such as 3700 or Aronix 3033HV (manufactured by Toagosei Kagaku Co., Ltd.).

Third step: The glass lens 1 is dropped into the cylindrical jig 5 with the R2 side facing down, and the resin m is sandwiched between the two by pressing the glass lens 1 against the resin m.

Fourth step: The first layer 2 is formed directly on the lens 1 on the spot by irradiating ultraviolet rays through the glass lens 1 to harden the resin m.

This allows the first layer 2 to have a shape error of 3 μm or less.

Fifth step: The obtained semi-finished product is taken out from the jig 5 and released from the mold 4.

Sixth step: The mold 4 released in the previous step is dropped into the same jig 5 again.

Seventh step: 18 mg of the same resin m as used in the second step is poured onto the mold 4.

8th step: The semi-finished product released from the mold in the 5th step is dropped into a cylindrical jig 5 with the first layer 2 facing down, and the semi-finished product is placed in a resin m
By pressing the resin m between the two.

Ninth step: The second layer 3 is formed directly on the first layer 2 on the spot by curing the resin m by irradiating ultraviolet rays through the semi-finished product.

In this way, the lens of this example (with a shape error of 0.3 μm or less) was obtained.

In addition, for the silane coupling treatment of the glass lens 1,
For example, the product name KBM503 (manufactured by Shin-Etsu Chemical Co., Ltd.) may be used after being diluted with a 2 wt % ethanol solution.

Further, in order to improve the peelability between the mold 4 and the resin molded layer, it is preferable to perform a surface treatment such as nickel plating on the surface of the mold.

〔Effect of the invention〕

As described above, according to the present invention, if the thickness of the first layer is made thinner than the second layer in the center part, which is thinner than the peripheral part, even if the overall thickness is made thinner, the thickness of the second layer becomes thinner than the second layer. It is possible to ensure a relatively large thickness (nearly uniform thickness), and as a result, ■ it is possible to reduce surface shape errors; Further, even if the ambient temperature increases, the shape error is prevented from deteriorating.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram showing a cross section of a resin-bonded aspherical lens according to an embodiment of the present invention. FIG. 2 is a conceptual diagram showing a cross section of a resin-bonded aspherical lens according to a conventional example. FIG. 3 is an explanatory diagram showing intermediate steps in manufacturing the lens of the example. *All are deformed and do not represent accurate dimensional ratios. [Explanation of symbols of main parts] -1.-Glass lens 2-...--1st resin molded layer (first layer) m-
111...Resin 3 before curing ゛゜゜゛...゜Second resin molded layer (second layer) 4.
・・・・−・・Mold (an example of a mold) 5−・−・−Jig

Claims (1)

[Claims] A glass lens (1) having an R2 surface made of an aspherical or spherical surface that approximates a desired aspherical surface, and a glass lens (1) having a thick peripheral part and a thin central part formed directly on the R2 surface. A resin-bonded aspherical lens consisting of a first resin molded layer (2) and a second resin molded layer (3) molded directly thereon, having a substantially uniform thickness and a desired aspherical shape. In, the first resin molded layer (2)
A lens characterized in that the thickness at the center of the second resin molded layer (3) is thinner than that of the second resin molded layer (3).