JPH05254862A - Production of resin-bonded aspherical lens - Google Patents

Abstract

PURPOSE:To obtain an aspherical lens having high precision at a low cost while preventing the intrusion of bubbles by forming a resin layer on a surface of a prescribed part and cutting and polishing the resin layer of the obtained intermediate product. CONSTITUTION:A resin curable by cross-linking such as epoxy resin or a thermoplastic resin such as polystyrene is formed e.g. by press-forming on a surface of a glass part constituting the main body of the lens and having spherical or planar shape having a curvature close to that of the desired aspherical face to obtain an intermediate product having an integrated resin layer. The resin layer of the intermediate is cut with a computer-controlled ultra-high precision cutting machine and the cut surface is polished to obtain the objective resin- bonded aspherical lens 'composed of a glass member constituting the main part of the lens and a resin layer having aspherical surface'. The lens consists of a glass member 1, a resin layer 2 and an intermediate resin layer 2b (the resin layer before cutting) and having desired aspherical face on the surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a "resin-bonded aspherical lens comprising a glass member as a main body and a resin layer having an aspherical surface".

[0002]

2. Description of the Related Art As lenses used in optical products such as cameras and microscopes, glass lenses are mainly used. A glass lens is a step of forming a glass block (called a lens blank) by press molding from glass in a molten state, and a step of manufacturing a rough surface lens having a desired curvature by grinding the lens blank with a grinding machine. It is manufactured through a process of removing a tool mark and a crack layer at the time of grinding by polishing a rough surface lens.

By the way, the lens includes an aspherical lens, and the surface shape of this lens is aspherical. This aspherical lens is important because it has excellent performance that cannot be obtained with a spherical lens. However, since aspherical lenses are not spherical surfaces, if one attempts to manufacture them from glass lens blanks, the lens blanks must be manufactured one by one with an ultra-precision grinding machine (NC processing machine) under computer control. I don't get. Therefore, there is a drawback that the manufacturing cost is considerably higher than that of the spherical lens.

Therefore, a method of producing an aspherical lens by a method such as press molding, injection molding, or casting, which uses resin instead of glass, has been put into practical use. This method has a feature that the manufacturing cost is lower than that of an aspherical lens because a mold can be manufactured once and a large number of lenses can be duplicated and mass-produced by using the mold. However, the resin lens has a fatal defect that its optical performance greatly changes due to changes in temperature and humidity, and the use of this resin lens has been limited to those in which such changes do not significantly affect the performance of the product.

In order to solve this drawback, resin-bonded aspherical lenses as shown in FIGS. 2 and 3 have been developed. This is composed of a glass lens (a kind of “glass member” in the present invention) and a “resin layer having an aspherical surface” integrally formed with the glass lens. The glass lens is mainly used, and the resin layer is thin (for example, the thickness is 5 to 100 μm). The main glass lens has a spherical surface (see FIG. 3: JP-A-60-56544) or a rough aspherical surface (see FIG. 4: JP-A-63-157103). Such a resin-bonded aspherical lens is manufactured, for example, by a manufacturing method including the following first to sixth steps. Figure 5
Please refer to. First step: step of horizontally placing the mold (3) having a desired aspherical surface; second step: step of dropping a predetermined amount of the radiation curable resin liquid (2a) on the central part of the mold (3); 3 step: step of placing the glass lens (1) having a spherical surface or a rough aspherical surface on the mold (3); 4th step: the distance between the glass lens (1) and the mold (3) approaches a predetermined value. Step 5: Step 5: Step of curing resin solution (2a) sandwiched between glass lens (1) and mold (3) by irradiating it with radiation (for example, ultraviolet rays); Step 6: A step of peeling the aspherical resin layer (2) obtained by curing from the interface with the mold (3) together with the glass lens (1); in this case, the resin liquid (2a) is an ultraviolet curable resin.
The method of molding such a resin layer (2) corresponds to “cast molding” in terms of classification. A method of producing a resin-bonded aspherical lens by injection molding using a thermoplastic resin instead of the resin liquid has also been developed. For example, JP-A-60-205401,
See JP-A-61-203401 and JP-A-3-133611. In injection molding, a thermoplastic resin is heated and fluidized (plasticized) in a cylinder of an injection molding machine. Then, the fluidized resin is injected into the cavity 5 of the mold 3 (where the glass lens 1 is previously arranged) as shown in FIG. 2 to fill the cavity. Then, when cooled, the resin
The resin layer (2) is formed by solidifying and losing fluidity. At this time, the resin layer (2) is integrated with the glass lens (1), and the integrated one is a resin-bonded aspherical lens.

In any case, the production of the resin-bonded aspherical lens involves the curing or solidification of the resin liquid or the fluidized resin when forming the resin layer. Since the resin-bonded aspherical lens is mainly a glass lens (a kind of glass member in the present invention), it is resistant to changes in temperature and humidity. But,
When the resin layer is formed by curing or solidification, it is inevitably contracted. Therefore, the shape accuracy of the aspherical surface is likely to be reduced. Therefore, it is necessary to make the resin layer as thin as possible and have a uniform thickness as a whole.

[0007]

Therefore, in the conventional manufacturing method, since the resin layer must be thinned, bubbles (bubbles) easily enter into the resin layer in the method using the resin liquid as the first material. In the method of using a thermoplastic resin as a raw material, since the viscosity of the plasticized resin is still high, the resin does not flow into the narrow cavity, and the shape accuracy of the resin layer is low. Had. In addition, since it is necessary to make the resin layer have a uniform thickness as a whole, when making a lens having a large amount of aspherical surface, it is necessary to make the glass lens a certain amount of aspherical surface (called rough aspherical surface). There is a third problem that the manufacturing cost becomes high. The object of the present invention is to solve these problems.

[0008]

Therefore, according to the present invention, firstly, an intermediate body comprising a glass member as a main body having a spherical or planar shape and a resin layer integrally molded on the surface thereof is prepared. “A main glass member and a resin layer having an aspherical surface” comprising a first step and a second step of cutting and polishing the resin layer to create a desired aspherical surface. A method (claim 1) for producing a "resin-bonded aspherical lens" is provided.

Secondly, the present invention provides a method (claim 2) according to claim 1, wherein the glass member is a glass lens having a spherical surface.

[0010]

The intermediate used in the present invention comprises a glass member as a main body and a resin layer integrally formed on the surface of the glass member.
The resin layer may be present on only one side or both sides of the glass member. Further, the resin layer may wrap the entire glass member. The resin layer may have ribs or support portions that protrude outward from the side surface of the glass member. The glass member has a flat surface, preferably a spherical surface. in this case,
The spherical surface is particularly preferably a spherical surface having a curvature close to that of the desired aspherical surface.
The resin layer must be thicker than the final desired resin layer. However, in the final lens, a thick resin layer is easily affected by changes in temperature and humidity, so a thinner resin layer is preferable. Therefore, in order to reduce the cutting amount, it is preferable that the resin layer of the intermediate body is thin. The resin layer does not have to have the same refractive index as that of the glass member, but preferably has the same refractive index. The surface shape of the resin layer of the intermediate body is not particularly limited, but is preferably a spherical surface having a curvature close to a desired aspherical surface. That requires less cutting.

As the resin, epoxy resin, unsaturated polyester, polyurethane, cross-linking curable resin such as CR-39, or polycarbonate, polysulfone, polyarylate, elastomer, ionomer, fluororesin, amorphous polyolefin, polystyrene, acrylic resin. , And thermoplastic resins such as modified acrylic resin.

The method for producing the intermediate is basically the method disclosed in JP-A-60-56544, which uses a conventional resin liquid as a raw material, and JP-A-60-205401 and 61, which uses a thermoplastic resin as a raw material. −20
Methods such as 3401 and JP-A-3-133611 may be used. Of course, other than these, press molding using a thermoplastic resin as a raw material may be used. In order to improve the adhesive strength with the resin layer, it is preferable that the glass member is previously subjected to silane coupling treatment before the production of the intermediate.

The second step of the present invention is a step of creating a desired aspherical surface on the surface by cutting and polishing the resin layer of the intermediate. Cutting can be easily performed by using an ultra-precision cutting machine (NC processing machine) controlled by a computer. In this respect, it is similar to the method of manufacturing a glass aspherical lens in which a glass lens blank is ground by a grinding machine and polished. However, since the resin layer has lower hardness than glass and does not generate a crack layer, polishing after cutting is easy. That is, the tool marks due to cutting can be easily removed by polishing. On the other hand, glass is difficult to polish after grinding. It is difficult and time-consuming to remove tool marks and crack layers due to grinding by polishing. Further, although the cutting machine is super-precision, it has a simple structure and is inexpensive as compared with the grinding machine. Therefore, even if the whole aspherical lens is considered, the manufacturing cost is lower when the resin-bonded aspherical lens is manufactured by the method of the present invention than when the whole is made of glass.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

[0015]

EXAMPLE FIG. 1 is a schematic vertical sectional view of a resin-bonded aspherical lens manufactured in this example. The two-dot broken line (imaginary line) shows the outermost shape of the resin layer (2b) of the intermediate body. Step 1a: Prepare a cavity core (3) as shown in FIG. 2 and set it in an injection molding machine. The cavity core (3) is composed of two molds, a movable mold and a fixed mold, and a cavity (5) is formed between them. The surface of the fixed mold on the side of the cavity (5) forms a spherical surface close to a desired aspherical surface. The cavity core (3) is surrounded by the mother die (6), and the resin supply passage (7) is formed through the mother die (6). The inlet of the resin supply passage (7) is joined to the outlet of the cylinder (8) of the injection molding machine, and the outlet of the resin supply passage (7) is open to the cavity (5).

A glass lens (1), which is a kind of glass member, is placed in the cavity (5). Glass lens (1)
Is a meniscus lens with an outer diameter of φ15 to φ40 mm,
The center thickness is 3 to 10 mm. The glass lens (1) has a first surface on which the resin layer (2b) is formed and a second surface on which the resin layer (2b) is not formed. The first surface has been subjected to a silane coupling treatment in advance in order to improve the adhesive force with the resin layer (2b). As a silane coupling agent, for example, trade name KBM5
03 (manufactured by Shin-Etsu Chemical Co., Ltd.) is diluted with a 2 wt% ethanol solution and used. The second surface has a shape accuracy within the tolerance of the product design (for example, 0.5 μm) and surface roughness (for example, 10 nm).
Have. On the other hand, those on the first surface may have a shape accuracy outside the allowable value (for example, 5 μm).

Step 1b: An injection molding machine is filled with an acrylic resin (trade name: Acrypet VH, manufactured by Mitsubishi Rayon Co., Ltd.), and the resin is heated to 200 ° C. to 280 ° C. for plasticization. The plasticized resin is injected into the cavity (5) from the cylinder (8) via the resin supply passage (7). 10 to 60 seconds after injection, the plasticized resin naturally cools and solidifies. When solidified, the resin adheres to the glass lens (1) to form a resin layer (2b). The thickness of the resin layer (2b) is 1 to 3 mm here. Since the intermediate body is manufactured in this way, the mother die (6) and the cavity core (3) are opened, and the intermediate body is taken out. The time from injection to ejection is about 60 to 120 seconds. Thus, the first step is completed.

Step 2a: An NC cutting machine is prepared and the intermediate body manufactured in the previous step is set. With this processing machine, the resin layer (2b) is cut into a desired aspherical shape. Cutting is completed in about 60 to 180 seconds per piece. Step 2b: Prepare a polishing machine for plastics, set the cut intermediate on it, and perform polishing. By removing the "tool marks due to cutting" remaining on the surface of the resin layer with this polishing machine, the desired aspherical resin layer (2) is formed. Polishing is completed in about 3 to 5 minutes per piece. In this way, the second step is completed and the lens shown in FIG. 1 is manufactured.

[0019]

According to the present invention, since the resin layer of the intermediate can be made thick, it is difficult for bubbles (air bubbles) to enter the resin layer in the method using the resin liquid as the raw material and the resin liquid as the raw material. Since the intermediate body having the thick resin layer is once formed and then the aspherical surface is formed by cutting and polishing, the aspherical surface has high shape accuracy. That is, no matter how thick the resin layer is, it is not necessary to be concerned about the deterioration of the shape accuracy due to the contraction during solidification or curing. Even when manufacturing a lens with a large amount of aspherical surface, a spherical glass lens can be used as a glass member,
Manufacturing costs are low. Since the resin layer has a lower hardness than glass, it is possible to inexpensively create an aspherical surface by grinding and polishing.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view of a resin-bonded aspherical lens manufactured in an example of the present invention.

FIG. 2 is a schematic view showing a side surface of a cavity core or the like and a vertical cross section with a part thereof cut away.

FIG. 3 is a schematic vertical sectional view of a conventional resin-bonded aspherical lens.

FIG. 4 is a schematic vertical sectional view of another conventional resin-bonded aspherical lens.

FIG. 5 is a schematic view showing a vertical cross section of a glass member, a mold and the like in each step of a conventional manufacturing method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glass member (or glass lens which is one of them) 2 Resin layer 2a Resin liquid before curing 2b Intermediate resin layer (resin layer before grinding) 3 Cavity core (mold in the explanation of conventional method) 4 Ultraviolet 5 Cavity 6 Mother mold 7 Resin supply path 8 Cylinder of injection molding machine

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Claims (2)

[Claims] 1. A first step of preparing an intermediate body comprising a glass member as a main body having a spherical or planar shape and a resin layer integrally molded on the surface thereof, and cutting and polishing the resin layer. Thus, a method for producing a "resin-bonded aspherical lens composed of a glass member as a main body and a resin layer having an aspherical surface", which comprises the second step of creating a desired aspherical surface. 2. The method according to claim 1, wherein the glass member is a glass lens having a spherical surface.