JP2009066827A - Molding method of optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To mold an optical element to which the fine pattern of a mold is transferred with high precision. <P>SOLUTION: First, a dummy substrate 11 to which a photocurable resin 12 is dripped, is pressed to a mold 10 with a fine pattern, and the resin 12 is pressed wide and then, is cured in such a state that the resin layer, the mold and the dummy substrate 11 remain not released. Thus the dummy substrate is removed. After that, an optically patterned part 2a of the resin layer 2 of the optical element, is molded by shining light and thereby, curing the resin. Following these procedures, a substrate 1 to which an uncured resin 13 is dripped, is pressed to the surface of the optically patterned part, and pressure is applied to elongate the resin 13. Further, the resin is cured by light irradiation and the resin layer 2 with the optically patterned part 2a and a base part 2b, and the substrate 1 are released in one piece from the mold 10. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for molding a composite optical element having a resin layer to which a fine shape of a mold is transferred.

  2. Description of the Related Art Conventionally, a so-called replica molding technique is known in which a resin layer made of a photocurable resin or the like is molded on a glass substrate with a mold (mold). In the replica molding technique, first, a photo-curing resin is dropped on a molding surface having a desired optical shape, and then spread on the substrate. Next, when the desired shape is obtained, light is irradiated to cure the photocurable resin, and the mold is released. In this way, high transfer molding is possible, and a highly accurate optical element can be molded.

  However, as a problem in replica molding, there is a sink that is a shape deformation of the transfer surface due to curing shrinkage during resin curing. As a conventional technique for avoiding this sink, as disclosed in Patent Document 1, the mold shape outside the optically effective part is devised, and an uncured resin is supplied to the optically effective part. A method of generating is known. Patent Documents 2, 3, and 4 disclose a method of obtaining a highly accurate molded product by generating a sink on the opposite side to the mold forming surface, that is, the non-molded surface, by dividing a desired shape into multiple layers. Has been.

JP 2002-96338 A JP 2005-1319 A JP-A-6-254868 JP 2005-144717 A

  In the molding method described in Patent Document 1, as the resin fluidity is lost, the effect of avoiding sink marks is reduced, which is not a radical solution. In Patent Documents 2 and 3, the resin application method is squeezing or a uniform application method. When the mold has a spherical shape, it is difficult to control the uniform layer thickness.

  In Patent Document 4, when the resin is photocured, only the resin layer on the substrate side subjected to the water repellent treatment is peeled off and then the substrate is removed. However, the resin layer in contact with the substrate is a completely free surface. In the case of a thin layer having a base layer thickness of 10 μm or less, peeling occurs also on the mold side of the resin layer. For this reason, a high level transfer cannot be obtained.

  Particularly, in the case of the diffractive optical element, the thickness of the base portion and the grating height of the optical shape portion are approximately the same, or the case where the base layer thickness is smaller, that is, the thickness ratio is large.

  An object of the present invention is to provide an optical element molding method capable of molding a composite optical element having a large thickness ratio, such as a diffractive optical element, with high accuracy.

  In order to solve the above-described problems, an optical element molding method of the present invention is a mold having a fine shape for transferring to the resin layer in the optical element molding method including a resin layer having an optical shape portion. A first step of pressing the dummy substrate to which the uncured resin is adhered, forming the first layer including the optical shape portion of the resin layer, and removing the dummy substrate; and the first layer of the resin layer A second step of resin-curing the eye, and a third step of pressing the substrate on which the uncured resin is adhered to the first layer of the resin layer to form the second layer of the resin layer and curing the resin And a fourth step of integrally releasing the first and second layers of the resin layer and the substrate from the mold.

  By removing the dummy substrate and curing the first layer having the optical shape portion with resin, the occurrence of sink marks in the optical shape portion on the side in contact with the mold is suppressed. As a result, a composite optical element having a large thickness ratio, such as a diffractive optical element having a base layer thickness that is approximately equal to or less than the grating height of the optical shape portion, can be formed without causing shape deformation on the mold transfer surface. It becomes possible to mold with accuracy.

  The best mode for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 shows a composite optical element molded by the optical element molding method according to an embodiment. This optical element includes, on a substrate (glass substrate) 1, a resin layer 2 having an optical shape portion 2a which is a diffraction grating portion made of resin and having a maximum thickness Ha, and a base portion 2b having a base layer thickness Hb. Yes.

  FIG. 2 is a diagram showing each step of the optical element molding method in the present embodiment.

  First, as shown to Fig.2 (a), the metal mold | die 10 which reversed the desired fine shape is produced with a precision cutting machine. At this time, a bank is formed on the outer periphery of the mold outside the optically effective portion.

  Next, as shown in FIG. 2B, an appropriate amount of a photo-curing resin 12 that is an uncured resin is dropped onto the center of the water repellent surface of the dummy substrate 11 and attached to the dummy substrate 11. Next, as shown in FIG. 2C, the dummy substrate 11 is brought into contact so that the centers of the mold 10 and the dummy substrate 11 are aligned, and pressed while preventing bubbles from entering the photocurable resin 12, Resin 12 is stretched over the entire mold surface.

  After the resin 12 has been spread, light other than ultraviolet rays is irradiated with a load applied. As a result, sink marks due to curing shrinkage are concentrated on one surface of the resin 12, and the first layer including the optical shape portion 2a of the resin layer 2 is formed. Thereafter, the dummy substrate 11 is removed.

  Next, as shown in FIGS. 2D and 2E, light is irradiated with the top surface of the first layer made of the resin 12 exposed. First, light is irradiated in an oxygen-containing atmosphere, and curing of the surface in contact with the mold is advanced by utilizing the curing inhibition by oxygen of the photocurable resin 12. Moreover, it is carried out in order to make it easy to generate sink marks on the upper surface not in contact with the mold by inhibiting the hardening of the upper surface in contact with the air. After sufficiently generating sink marks, light is irradiated in an oxygen-free atmosphere or in vacuum in order to cure the entire first layer including the optical shape portion 2a.

  Next, as shown in FIG. 2 (f), an appropriate amount of a photocurable resin 13, which is the same uncured resin as described above, is dropped onto the coupling treatment surface of the substrate 1 and attached to the substrate 1. Next, the optical shape portion 2a and the substrate 1 are brought into contact with each other so that the centers of the optical shape portion 2a and the substrate 1 are aligned, and the substrate 1 is pressurized and stretched over the entire surface while preventing bubbles from entering the resin 13 as shown in FIG. Thus, a second layer of the resin layer 2 is formed, and the resin is cured by irradiating light to form the base portion 2b of the resin layer 2. Thereafter, the mold 10 is released to obtain a molded product shown in FIG.

  Note that the dummy substrate 11 used in the first step needs to be lower than the adhesion force of the mold 10 in advance to facilitate removal from the resin 12, and it is desirable to perform water repellent treatment or the like. In addition, a fluororesin sheet may be sandwiched.

  In the first step, it is desirable to cure slowly in order to suppress rapid resin curing and to suppress uneven curing in the layer thickness direction.

  Further, in the first step, when an optical element having a large thickness ratio is molded, even if only the dummy substrate 11 is peeled off, the thickness ratio is large, so that the resin is peeled off on the mold side. Optical elements may not be obtained.

  Therefore, the following is performed so that the resin peeling does not occur on either the mold side or the dummy substrate side.

  First, in order to suppress rapid resin curing in the first step, irradiate light in a long wavelength region (for example, only in the visible light region) with little light absorption of the resin, or irradiate light with low illuminance. . Second, in the first step, as shown in FIG. 2C, the dummy substrate 11 is irradiated with light while applying a load.

  It is desirable that the light irradiation in the second step is first performed in an oxygen-containing atmosphere utilizing the effect of inhibiting resin curing by oxygen. The reason is that the resin 12 in contact with the mold 10 is further cured, and the curing on the free surface side that is not in contact with the mold 10 is delayed.

  Thereby, sink marks due to curing shrinkage are formed on the free surface side of the resin 12. Thereafter, when sufficient sink marks are generated in the resin 12, it is desirable to perform light irradiation in an oxygen-free atmosphere or a vacuum in which oxygen is removed in order to uniformly cure the whole.

  A diffractive optical element having a diffraction grating shape with a base layer thickness of 5 μm and a grating height of 12 μm was formed on a substrate glass (substrate) having a diameter of 60 mm by the procedure shown in FIG.

  First, as shown in FIG. 2 (a), a mold having a desired shape inverted was prepared with a precision cutting machine. At this time, a 3 μm bank is made on the outer periphery of the mold, which is outside the optically effective portion.

  Next, two substrate glasses are prepared, and one substrate is a dummy substrate, so that a water repellent treatment is performed, and the other substrate glass is subjected to a coupling treatment. At this time, a fluorine-based water repellent treatment agent was applied to the entire glass surface of the dummy substrate, and dried at 100 ° C. for 1 hour. In addition, a silane coupling agent was applied to the entire glass surface of the substrate glass serving as a substrate, and dried by heating at 100 ° C. for 1 hour.

  As a first step, as shown in FIGS. 2B and 2C, an appropriate amount of a photocurable resin was dropped onto the center of the water repellent surface of the prepared dummy substrate. Next, the dummy substrate was inverted and brought into contact so that the mold and the center of the dummy substrate 11 were aligned, and the dummy substrate was pressed and stretched over the entire surface of the mold while preventing bubbles from entering the resin. As a result, the base layer thickness is approximately 3 μm. At this time, the applied load was 700N. After the resin was spread out, the light excluding ultraviolet rays was irradiated using a 400 nm sharp cut filter while applying a load. The irradiation conditions at this time are 8.4 mW (405 nm) and 515 seconds.

  The above irradiation conditions are conditions for slowly curing the first layer of the resin layer so as not to cause sink marks due to curing shrinkage on both sides of the resin. Thereafter, the dummy substrate is removed. As a result, no resin peeling occurs on either the mold side or the dummy substrate side.

  As the second step, as shown in FIGS. 2D and 2E, with the top surface of the first layer of the resin layer exposed, light is first emitted at 13 mW (405 nm) as the first irradiation. After irradiation for 330 seconds, irradiation was performed at 18 mW (365 nm) for 26 minutes and 21 seconds. Next, as the second irradiation, while performing nitrogen purge, irradiation was performed at 12 mW (405 nm) for 4 minutes and 18 seconds, and then irradiation was performed at 16.5 mW (365 nm) for 11 minutes and 20 seconds. The first irradiation utilizes the curing inhibition of the photocurable resin by oxygen, promotes the curing of the surface in contact with the mold, and inhibits the curing of the upper surface in contact with air, thereby bringing the sink into contact with the mold. It was done to make it easier to occur on the upper surface. Further, the second irradiation was performed in order to cure the entire resin after sufficiently generating sink marks.

  As a 3rd process, as shown in FIG.2 (f) and (g), a suitable quantity of the same photocurable resin as a 1st process is dripped at the coupling process surface of the substrate glass used as the board | substrate of an optical element, and a substrate glass Was reversed so that the optical shape portion and the center of the substrate glass were in contact with each other. Then, the substrate glass was pressed and stretched over the entire surface while preventing bubbles from entering the resin. Thus, when the second layer of the resin layer is formed, the total base layer thickness is approximately 5 μm. At this time, the applied load is 700N. After spreading the resin, with the load applied, light was irradiated at 1.5 mW (365 nm) for 280 seconds, then irradiated at 9 mW (365 nm) for 34 minutes 53 seconds to cure the resin, and the first layer and the substrate Glue.

  After irradiation, as a fourth step, the resin layer composed of the first layer and the second layer and the substrate are released as a unit.

  The diffractive optical element thus obtained was evaluated by a non-contact three-dimensional surface shape measuring instrument New View 5000 (manufactured by zygo). The transfer rate of the grating height of the diffractive optical element in this example was 99.9%, indicating a very good transferability.

Comparative example

  As a comparative example, a diffractive optical element was molded using a diffraction grating mold having a grating height of 12 μm by the method according to the conventional example shown in FIG.

  First, as shown in FIG. 3A, a mold 110 in which a desired shape was inverted was created with a precision cutting machine. At this time, there is no bank for controlling the thickness of the base layer outside the optically effective portion, and a diffractive optical element shape having a desired layer thickness is formed with a metal spacer.

  This time, the base layer thickness was set in four ways: 1.2 μm, 5 μm, 12 μm, and 15 μm.

  Next, a silane coupling agent was applied to the entire glass surface on the substrate 101, and dried at 100 ° C. for 1 hour.

  An appropriate amount of the same photocurable resin 112 as in the above example was dropped on the coupling surface of the substrate 101. Next, as shown in FIG. 3B, the substrate 101 is turned over so that the mold 110 and the center of the substrate 101 are in contact with each other, and the substrate 101 is pressed so that bubbles do not enter the resin 112. The resin layer 102 was formed by stretching. Thereafter, as shown in FIG. 3C, ultraviolet light was irradiated at 1.5 mW (365 nm) for 280 seconds, and the resin peeling between the mold 110 and the resin layer 102 was observed after the irradiation.

  As a result, peeling was observed when the base layer thickness was 1.2 μm, 5 μm, and 12 μm, and no peeling was observed when the base layer thickness was 15 μm.

  Therefore, a diffractive optical element having a thickness ratio, that is, a ratio of a so-called base layer thickness and a maximum thickness (grating height) of the optical shape portion of 0.1 or more and 1 or less should be formed without using the present invention. Proved difficult.

It is a schematic diagram which shows the structure of the optical element shape | molded by the shaping | molding method of the optical element by one Embodiment. It is a figure which shows the procedure which shape | molds an optical element with the shaping | molding method of the optical element by one Embodiment. It is a figure which shows the procedure which shape | molds an optical element with the conventional shaping | molding method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Resin layer 2a Optical shape part 2b Base part

Claims (7)

In a method for molding an optical element including a resin layer having an optical shape part,
A dummy substrate having an uncured resin attached is pressed against a mold having a fine shape for transferring to the resin layer, and the first layer including the optical shape portion of the resin layer is molded, and the dummy substrate A first step of removing
A second step of resin curing the first layer of the resin layer;
A third step of pressing the substrate on which the uncured resin is adhered to the first layer of the resin layer, molding the second layer of the resin layer, and curing the resin;
And a fourth step of integrally releasing the first and second layers of the resin layer and the substrate from the mold.   The method for molding an optical element according to claim 1, wherein the uncured resin in the first step and the third step is a photocurable resin.   The method for molding an optical element according to claim 2, wherein the second step includes a step of irradiating light to the first layer of the resin layer in an oxygen-containing atmosphere.   The method for molding an optical element according to claim 2, wherein the second step includes a step of irradiating light to the first layer of the resin layer in an oxygen-free atmosphere or in a vacuum.   5. The method of molding an optical element according to claim 2, wherein, in the third step, light is applied to the second layer of the resin layer while pressurizing the substrate.   The method for molding an optical element according to claim 1, wherein a ratio between a base layer thickness of the resin layer and a maximum thickness of the optical shape portion is 0.1 or more and 1 or less. .   An optical element comprising a resin layer molded by the method for molding an optical element according to claim 1.

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