JPH0971439A - Aspheric optical element and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an aspheric optical element reduced in shape change with time, due to ambient temperature and humidity, of the aspherically shaped resin layer by sandwiching a photocurable resin in between a mold having shape inverted to a desired aspheric surface and an optical preformed material with similar shape to the above-mentioned shape followed by irradiating the resin with light and then further irradiating the resin with second light of higher energy. SOLUTION: As shown in the figure, the upper surface of a mold 3 represents a recessed aspheric surface 3a inverted to an aspheric surface 24.8mm in central radius of curvature. A polystyrene-based photocurable resin (nD=1.59) 2a is dripped onto the surface 3a, and an optical preformed material 1 as a glass lens consisting of SK2 (nD=1.607) is then placed on the resin. The interval between the lens 1 and the mold 3 is kept at a specified distance. The resin layer is then cured by being irradiated, through the glass lens 1, with ultraviolet light consisting mainly of g-rays (436nm) emitted from a high-pressure mercury lamp as a light source at a illuminance of 27mW/cm<2> for 2min followed by 2nd ultraviolet light of higher energy (310nm or so) at an illuminance of 20mW/cm<2> for 10min.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a camera, a copying machine,
The present invention relates to a lens element having an aspherical shape used in a laser printer or the like, and particularly to a resin-bonded aspherical lens formed by bonding an aspherical shaped layer made of a photocurable resin on a lens base material.

[0002]

2. Description of the Related Art Conventionally, in various optical devices, an optical element having an aspherical surface has been actively used in order to achieve high performance, small size, light weight, and low cost of optical elements such as lenses and reflecting mirrors.

As a method for producing such an aspherical optical element at low cost, a resin-bonded aspherical lens (hereinafter referred to as a hybrid lens) in which an aspherical layer made of a photocurable resin is bonded to the surface of a spherical glass lens. There is. As a conventional technique of this system, one disclosed in Japanese Patent Laid-Open No. 60-56544 (hereinafter referred to as Prior Art 1) or one disclosed in Japanese Patent Laid-Open No. 6-298886 (hereinafter referred to as Prior Art 2). There is).

In these hybrid lenses, in order to prevent the aspherical layer made of a resin material from changing its material under the influence of environmental temperature, humidity, etc.
Then, the second photocurable resin having higher weather resistance is coated on the aspherical surface layer, and in the prior art 2, an attempt is made to improve the weather resistance of the photocurable resin material itself forming the aspherical surface layer. Has been.

[0005]

In the above-mentioned prior art 1, it is said that the shape change due to the shrinkage due to the resin curing at the time of forming the aspherical shape layer is reduced and the weather resistance is also improved, however, no heating is required. As can be seen from the description that vacuum deposition is performed, heat resistance has not been improved. For this reason, when the antireflection film is formed on the aspherical resin layer, heating cannot be performed, so that moisture absorption cannot be removed and adhesion is decreased, or the film density is decreased, resulting in a dense film. However, there is a problem that the antireflection effect is lowered without being formed.

Further, in the above-mentioned prior art 2, the heat resistance is improved and the wear resistance for reducing the generation of scratches and cracks is improved, but it is affected by the temperature and humidity of the environment. The shape stability of the aspherical resin layer over time cannot be said to be sufficient, and the change in the aspherical shape of about 0.8 to 1.8 μm still occurs. The value of this shape change is by no means negligible. If the aspherical shape of the aspherical resin layer changes to the above value, for example, an increase in field curvature and an increase in coma will occur, resulting in an image formation of the lens. There is a problem that the performance fluctuates.

The present invention has been made in order to solve the above-mentioned problems of the prior art, and does not significantly increase the manufacturing cost, does not use a special resin material that is difficult to obtain, and does not use a hybrid lens. It is an object of the present invention to provide an aspherical optical element which improves the weather resistance of the aspherical resin layer, and particularly improves the heat resistance and shape stability of a hybrid lens, and a method for manufacturing the same.

[0008]

In order to achieve the above-mentioned object, a method for manufacturing an aspherical optical element according to the present invention comprises a mold having a shape that is the inverse of a desired aspherical surface, and a shape that approximates the desired aspherical surface. A photocurable resin is sandwiched between the optical base material and the optical base material having a predetermined distance between the mold and the optical base material, and light irradiation is performed to obtain a desired optical base material surface. In the method for manufacturing an aspherical optical element in which an aspherical resin layer is cured and formed, the photocurable resin is irradiated with second irradiation light having higher energy than the irradiation light after the light irradiation. .

Alternatively, in the method of manufacturing an aspherical optical element, the second irradiation light is not transmitted through the optical base material, but is irradiated from the aspherical spherical resin layer side. . Alternatively, in the method for manufacturing an aspherical optical element, the second light irradiation is performed under reduced pressure. Alternatively, in the method for manufacturing an aspherical optical element, the second light irradiation is performed simultaneously with heating the photocurable resin. Alternatively, the aspherical optical element according to the present invention is characterized in that the aspherical resin layer is coated with an antireflection layer.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. First Example FIGS. 1 to 4 are schematic views showing the steps of a first example of the method for manufacturing an aspherical optical element according to the present invention. In the first embodiment, the optical base material 1 is SK2 (nD = 1.607).
Is a convex meniscus lens having a spherical surface with a diameter of 28 mm and a concave surface (R1) of 36.8 m.
m, convex surface (R2) 25.4 mm, center thickness 4.15 mm
And In FIG. 1, the center radius of curvature 2 is on the upper surface of the mold 3.
A concave aspherical surface 3a is formed by inverting the 4.8 mm aspherical surface, and a photocurable resin (nD = 1.59) 2a based on polystyrene resin is dropped on the concave aspherical surface 3a.

Next, as shown in FIG. 2, the glass lens 1 is lowered from above the photocurable resin 2a to keep the distance between the glass lens 1 and the mold 3 at a constant distance. At this time, the photocurable resin 2a spreads between the glass lens 1 and the mold 3 to form the convex aspherical surface layer 2 that follows the concave aspherical surface 3a of the mold. Resin center thickness at this time is 0.3
It was set to 6 mm. Then, in order to cure the aspherical layer 2, the g-line (43
Ultraviolet rays 4 whose main component is 6 nanometers) was irradiated through the glass lens 1 at an illuminance of 27 mW / square cm for 2 minutes.

Subsequently, in order to improve the heat resistance and shape stability of the aspherical resin layer 2 according to the present invention, as shown in FIG. 3, the ultraviolet rays 4 (436 nm) are used.
The second ultraviolet ray 5 having a shorter wavelength and a higher energy of about 310 nm is irradiated at a illuminance of 20 mW / square cm for 10 minutes. In addition to ultraviolet rays with a wavelength of around 310 nanometers, wavelengths from 200 nanometers to 3
It is effective with ultraviolet rays up to 70 nm, and low-pressure mercury lamps, metal halide lamps, xenon mercury lamps, etc. are suitable as light sources.

Next, as shown in FIG. 4, the hybrid lens 10 in which the aspherical resin layer 2 is bonded to the surface of the glass lens 1 is removed from the mold 3. In the hybrid lens 10 thus produced, the resin layer 2 cured by the first ultraviolet ray 4 is first exposed to the second ultraviolet ray 5 having higher energy, whereby the curing reaction is further promoted. Thus, it is possible to form a resin having a high hardness, which cannot be obtained only by irradiating the first ultraviolet ray 4. As a result, in the hybrid lens 10 according to the present invention, the heat resistance of the aspherical resin layer 2 is improved, and the aspherical resin layer 2 is improved.
The change in shape over time due to the influence of the temperature and humidity of the environment can be reduced to a level that is practically negligible. Further, the method for manufacturing an aspherical optical element according to the present invention,
It can be applied to photocurable resins in general.

Second Embodiment In the present invention, a hybrid lens having an aspherical resin layer having improved heat resistance and shape stability is manufactured even if a glass lens having a large absorption of short wavelength ultraviolet rays is used as an optical base material. can do. 5 to 8 are schematic views showing the steps of the second embodiment of the method of manufacturing an aspherical optical element according to the present invention. In the second embodiment, the glass material of the glass lens 11 has a higher refractive index than the glass lens 1 in the first embodiment, but BaF12 having a high degree of absorption of short wavelength ultraviolet rays.
(ND = 1.639), and the photo-curable resin 12a also has a higher refractive index than that of the first embodiment (nD = 1.63).
Is used. The process up to FIG. 6 of this embodiment is the same as that of the first embodiment, and the aspherical layer 12 made of a photo-curable resin is cured by the irradiation of the first ultraviolet ray 4 (g line 436 nm).

Next, referring to FIG. 7, the hybrid lens 20 in which the aspherical resin layer 12 is bonded to the surface of the glass lens 11 is removed from the mold 3. Then, in FIG. 8, from the resin layer 12 side of the hybrid lens 20,
A second ultraviolet ray 5 having a wavelength shorter than that of the first ultraviolet ray 4 and having a high energy of about 310 nm is irradiated.
In this embodiment, even if a glass lens such as BaF12 having a very small transmittance of ultraviolet rays having a wavelength of about 310 nm is selected as the optical base material, the aspherical resin layer 12 formed on the surface thereof has high heat resistance. The shape can be highly stabilized. This can reduce restrictions on the materials used for the optical base material of the hybrid lens.

Third Embodiment FIG. 9 shows a third method of manufacturing an aspherical optical element according to the present invention.
It is a schematic diagram which shows a part of process of an Example. In this embodiment, after performing the same steps up to FIG. 7 of the second embodiment, the hybrid lens 20 in which the aspherical resin layer 12 cured by the first ultraviolet ray 4 is bonded to the glass lens 11 is made of quartz. Placed in a vacuum chamber 7 having a window 6,
It was evacuated by a vacuum pump and the pressure was reduced to about 1 Pa. Then, while maintaining the depressurized state, the second ultraviolet ray 5 having a wavelength shorter than the first ultraviolet ray 4 and having a higher energy of about 310 nm is passed through the quartz window 6 and the aspherical layer made of a photocurable resin. Irradiated 12. Then, the inside of the decompression chamber 7 is returned to atmospheric pressure, and the hybrid lens 20 is taken out. In the present invention, since the second light irradiation is performed under reduced pressure, the gas generated from the aspherical resin layer 12 can be efficiently removed during the curing reaction by the second light irradiation, and the aspherical resin layer The high heat resistance and the high stability of the shape of No. 12 can be further promoted as compared with the case of carrying out in the air. In addition, the present embodiment also has an effect of reducing variation in the effect of the second light irradiation due to the influence of moisture in the atmosphere.

Fourth Embodiment FIGS. 10 to 12 are schematic views showing a part of the steps of a fourth embodiment of the method of manufacturing an aspherical optical element according to the present invention. In this embodiment, in the first to third embodiments,
Aspherical layer 2 made of a photocurable resin with the second ultraviolet ray 4
When further curing, the infrared ray 8 is used to heat the aspherical layer 2 to about 90 degrees Celsius. In FIG. 10, reference numerals are the same as those in the first embodiment, but the same applies to the second and third embodiments, and therefore the illustration is omitted. FIGS. 10, 11 and 12 correspond to the steps of FIGS. 3, 8 and 9 of the previous embodiment, respectively. In this embodiment,
Since the aspherical resin layer is heated during the curing reaction by the second light irradiation, the curing reaction of the resin layer is accelerated and accelerated by heating. This makes it possible to further improve the heat resistance and the shape of the resin layer. In this embodiment, heating by infrared irradiation is shown as the heating means, but a heater may be incorporated in the lens holding jig to perform heating by heat conduction.

Fifth Example FIG. 13 is a schematic sectional view of an example of the aspherical optical element according to the present invention. The hybrid lens 10 or 20 produced by the method according to each of the above claims 1, 2, 3, and 4.
Shows that the heat resistance of the aspherical resin layer 2 or 12 is dramatically improved as compared with the conventional one. For example, in the photocurable resin based on the polystyrene resin of the first embodiment, the heat distortion temperature is about 100 degrees Celsius. The degree of irradiation was improved to about 200 degrees Celsius by the second light irradiation. As a result, the hybrid lens 10 produced by the method of the present invention
Alternatively, in No. 20, sufficient heating can be performed when the antireflection layer is formed by the vapor deposition method, the sputtering method, or the like.
FIG. 13 shows that the antireflection layer 3 is heated while being heated in this manner.
0 was formed on the aspherical resin layer 2 or 12. As a result, even in a hybrid lens in which heating could not be performed and an effective antireflection layer could not be provided due to the poor heat resistance of the aspherical resin layer in the related art, the present invention provides an effective antireflection layer. Can be attached.

[0019]

As described above, in the method of manufacturing an aspherical optical element according to the present invention, after the photo-effect resin forming the aspherical shape layer is cured by the first light irradiation, the first
By the second light irradiation having energy higher than that of the irradiation light, the curing reaction of the resin layer is further promoted, and the resin layer having high hardness which cannot be obtained only by the first light irradiation can be easily obtained. As a result, it is possible to reduce the shape change of the aspherical resin layer with time due to the ambient temperature and humidity, which is a problem of the hybrid lens, to a practically negligible level. Further, in the method for manufacturing an aspherical optical element according to the present invention, since the second irradiation light is irradiated from the side of the photocurable resin forming the aspherical shape layer without passing through the optical base material, Even an optical base material having a high degree of absorption of the second irradiation light can be used, and the degree of freedom in selecting a material used for the hybrid lens optical base material can be increased. Further, since the absorption of the second irradiation light by the optical base material can be avoided, it is possible to eliminate the risk of damage to the optical base material by the second irradiation light.

Further, in the method for manufacturing an aspherical optical element according to the present invention, since the second light irradiation is carried out under reduced pressure, the gas containing water generated from the aspherical resin layer is removed. It is possible to further accelerate the curing of the resin layer than in the atmosphere, and to further improve the heat resistance and the shape stability. In addition, it is possible to reduce the variation in curing due to the second light irradiation due to the influence of atmospheric moisture. Further, in the method for manufacturing an aspherical optical element according to the present invention,
Since the aspherical resin layer is simultaneously heated at the time of the light irradiation, the curing reaction of the resin layer can be further promoted, and the heat resistance and the shape of the resin layer can be further stabilized.

In the aspherical optical element according to the present invention,
It is possible to provide a hybrid lens in which the aspherical resin layer has high heat resistance, can be heated when the antireflection layer is formed, and has a close adhesion and a precise antireflection layer. For this reason, it is possible to reduce the surface reflectance of the hybrid lens, which has been difficult to attach an antireflection layer in the past, and prevent ghost, fret, etc., and improve the performance of the product at low cost. Is big.

[Brief description of drawings]

FIG. 1 is a first method of manufacturing an aspherical optical element according to the present invention.
It is a schematic diagram which shows the process of an Example.

FIG. 2 is a schematic diagram of a step following FIG.

FIG. 3 is a schematic diagram of a process following the process of FIG.

FIG. 4 is a schematic diagram of a process following the process of FIG.

FIG. 5 is a second method of manufacturing an aspherical optical element according to the present invention.
It is a schematic diagram which shows the process of an Example.

FIG. 6 is a schematic view of a step following the step of FIG.

FIG. 7 is a schematic diagram of a process following the process of FIG.

FIG. 8 is a schematic diagram of a process following the process of FIG.

FIG. 9 is a third method of manufacturing an aspherical optical element according to the present invention.
It is a schematic diagram which shows a part of process of an Example.

FIG. 10 is a schematic view showing a part of the process of the fourth example of the method for manufacturing an aspherical optical element according to the present invention.

FIG. 11 is a schematic view showing a part of the process of the fourth example of the method of manufacturing an aspherical optical element according to the present invention.

FIG. 12 is a schematic view showing a part of the process of the fourth example of the method for manufacturing an aspherical optical element according to the present invention.

FIG. 13 is a schematic sectional view of an example of the aspherical optical element according to the present invention.

[Explanation of symbols]

 1 Optical Base Material 2a Photocurable Resin 3 Mold 3a Concave Aspherical Surface 4 Ultraviolet Ray 5 Second Ultraviolet Ray 10 Hybrid Lens

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Claims (5)

[Claims] 1. A photocurable resin is sandwiched between a mold having a shape that is the reverse of a desired aspherical surface and an optical base material having a shape that approximates the desired aspherical surface, and the mold and the optical element. By keeping the distance between the base materials at a predetermined distance and irradiating with light,
In the method of manufacturing an aspherical optical element in which a desired aspherical resin layer is formed by curing on the surface of the optical base material, after the light irradiation, a second irradiation light having higher energy than the irradiation light is irradiated with the photocurable resin. A method for manufacturing an aspherical optical element, which comprises irradiating the surface of the aspherical optical element. 2. The method for manufacturing an aspherical optical element according to claim 1, wherein the second irradiation light is not transmitted through the optical base material, but is irradiated from the aspherical spherical resin layer side. A method of manufacturing a characteristic aspherical optical element. 3. The method for manufacturing an aspherical optical element according to claim 2, wherein the second light irradiation is performed under reduced pressure. 4. The method for manufacturing an aspherical optical element according to claim 1, 2, or 3, wherein the second light irradiation is performed simultaneously with heating of the photocurable resin. Optical element manufacturing method. 5. The antireflection layer is coated on the aspherical resin layer.
The aspherical optical element described.