JP2006220816A - Method of manufacturing optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing an optical element by which a shrink mark that causes separation from a mold upon the curing due to that a resin thickness is large can be prevented and the degradation of an optical performance due to birefringence in the resin can be prevented. <P>SOLUTION: The method of manufacturing an integrated composite type optical element by molding and curing a light energy curable resin on a glass substrate by using a mold comprises: a process of dropping a first resin onto the mold; a process of uniformizing the first resin into a desired shape such as flat surface and spherical surface; a process of curing the first resin into a longitudinal elastic modulus of ≥100 MPa and ≤1,500 MPa; a process of dropping a second resin onto the first resin; a process of bringing a glass substrate into liquid contact with the second resin; a process of curing the second resin; and a process of separating the resin from the mold. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a lens having an aspherical surface and an element having a fine shape (unevenness) on the surface, such as a diffraction grating, a Fresnel lens, and an optical disk substrate.

Optical element manufacturing methods include glass grinding, polishing and precision molding using molds, thermoplastic resin injection molding and press molding, etc.
It is properly used depending on the required accuracy. For example, an imaging lens used in a camera or the like is manufactured by grinding and polishing glass, which is economically advantageous and has little performance deterioration with respect to temperature and humidity fluctuations as a spherical lens. Is manufactured by precision molding of glass using a mold. A lens used for a finder in a camera is not required to have an excellent imaging performance, and is manufactured by injection molding of a resin from the viewpoint of cost.

  In addition, in the case of an aspheric lens having a diameter of 30 mm or more or an optical element having a fine uneven shape on the surface, a thin layer of light energy curable resin is formed on a glass substrate and cured to obtain a required surface shape. The forming method is used. A large aspherical lens has poor shape accuracy in precision molding of glass, and if an attempt is made to ensure accuracy, the molding time becomes longer and the cost becomes higher. Optical elements with fine irregularities cannot be manufactured with glass because the irregularities are destroyed during mold release, and it is essential to manufacture with resin, but if the entire element is made of resin, the performance degradation due to environmental changes is large and the resin part is thin. The effect is reduced by the above method.

  As a method for producing this light energy curable resin, there are, for example, Patent Documents 1 and 2.

  In Patent Document 1, the first resin is applied to the entire surface of the mold, and the second resin is leveled with a pressure roll through a thin base film, and the second resin is laminated, followed by curing and release. A method of manufacturing a lens sheet having a Fresnel shape and the like that does not involve bubbles is proposed.

  Also, in Patent Document 2, when the first resin is filled on the mold and cured, the second resin is filled, and after the base material is placed and cured, the thickness deviation of the resin layer is large. A manufacturing method of an aspherical lens or the like free from transfer defects such as sink marks and distortions has been proposed.

Japanese Patent No. 2608440 Japanese Patent No. 2849299

  In the molding of a light energy curable resin, as described in Patent Document 2, a shape having a large resin thickness difference, a microlens lens in FIG. 7A, a diffraction grating in FIG. The difference between H1 and thickness H2) is that the resin partially peels off from the mold during curing, as shown in FIGS. 7B and 8B, 31a and 32a, resulting in poor shape. In order to prevent this, in Patent Document 2, the first resin is filled on the mold and cured, and then the second resin is filled and cured to prevent peeling from the mold during curing. In this case, there is a difference in cure shrinkage between the first resin and the second resin (the first resin is irradiated with ultraviolet rays twice), and the birefringence is caused by the residual stress in the resin, which affects the optical performance. give. In particular, if the surface shape of the first resin on the open side is poor, the optical performance is greatly reduced.

  Further, when the adhesive force between the mold and the resin and the adhesive force between the resin and the glass substrate are large at the time of mold release, there is a problem that peeling occurs at the interface between the first resin and the second resin.

  Furthermore, it is necessary to laminate a plurality of types of resins in order to separate the functions as resins used for optical elements. For example, when using a resin with low light transmittance, the thickness of the resin of the functional part is minimized, and the remaining part is made of resin with high transmittance.

  Accordingly, the first object of the present invention is to prevent the sinking from peeling off from the mold at the time of curing due to the large difference in thickness of the resin, and to prevent the optical performance from being deteriorated due to the birefringence in the resin. The object is to provide a method for manufacturing an element.

  A second object of the present invention is to provide an optical element manufacturing method capable of improving the adhesion at the interface in order to prevent peeling at the resin interface at the time of mold release.

  Furthermore, the third object of the present invention is to provide a method for manufacturing an optical element in which a plurality of types of resins having separated functions are laminated.

  In order to achieve the above object, the invention described in claim 1 is the first method for producing a composite optical element in which a light energy curable resin is molded and cured using a mold on a glass substrate. A step of dripping a resin on a mold, a step of smoothing the first resin into a required shape such as a flat surface, a spherical surface, a step of curing the first resin to a longitudinal elastic modulus of 100 MPa to 1500 MPa, a second A step of dropping a resin on the first resin, a step of contacting a glass substrate on the second resin, a step of curing the second resin, and a step of peeling the resin from the mold After that, an optical element is manufactured.

  According to a second aspect of the present invention, in the first aspect of the invention, the first resin is an anaerobic resin, and the first resin is cured in an oxygen-containing atmosphere.

  According to a third aspect of the invention, in the first aspect of the invention, the first and second resins are different.

  According to the first aspect of the present invention, it is possible to prevent shape defects such as sink marks during resin curing, and it is possible to prevent a decrease in optical performance due to birefringence due to residual stress.

  According to the second aspect of the present invention, it is possible to prevent adhesion between the resins by improving the adhesion between the laminated resins at the time of release.

  According to invention of Claim 3, the optical element which isolate | separated the function of resin can be manufactured.

  As an embodiment of the invention according to the present application, as a method of manufacturing a composite optical element in which a light energy curable resin is integrated with a glass substrate, a mold corresponding to the functional surface of the molded resin surface is prepared, A required amount of light energy curable resin is dropped on the top, and the resin is leveled into a shape corresponding to the shape of the glass substrate on which the resin is integrated.

  When the resin contact surface of the glass substrate to be integrated is a flat surface, it is leveled to a spherical surface when it is a spherical surface. The light energy curable resin is cured by applying light energy to a state where the longitudinal elastic modulus of the resin is 100 MPa or more and 1500 MPa or less. At this time, this resin is desirably an anaerobic resin, that is, a resin that does not proceed in the presence of oxygen, and is cured in an uncured state by curing in an atmosphere in which oxygen is present.

  Then, after dropping a required amount of the same resin on the first resin cured to have a longitudinal elastic modulus of 100 MPa or more and 1500 MPa or less, the glass substrate is in contact with the second resin to obtain a required refractive index. The first resin and the second resin are cured by applying light energy through the glass substrate. Then, the first resin and the second resin integrated on the glass substrate having a functional surface on the surface are obtained by peeling the first resin from the mold.

  FIG. 1 is a schematic view of a production method according to the present invention. In FIG. 1, 1 is an energy curable resin before curing, 2 is a mold for forming a functional surface of the resin surface, and 3 is a dropped resin. This is a spatula-shaped member for leveling the surface of the mold, and moves on the mold by a mechanism (not shown). 4 is ultraviolet light, 5 is a first resin cured to a longitudinal elastic modulus of 500 MPa, 6 is a light energy curable resin of the same material as the energy curable resin 1, 7 is a glass substrate, 8 is ultraviolet light, and 9 is a resin from the mold. It is lifted up by a mechanism (not shown) with an ejector for peeling off. Reference numerals 10 and 11 denote cured first and second resins, and reference numeral 12 denotes a composite optical element in which the resin and the glass substrate are integrated.

  First, a required amount of a liquid light energy curable resin is dropped on the mold 2 (FIG. 1A). On the surface of the mold 2, a fine sawtooth shape having a height of 10 μm and a pitch of 900 μm to 20000 μm is formed concentrically. This resin is flattened using a spatula 3, and the thickness of the resin is 11 μm by moving on the outer periphery abutting portion 2 a of the mold that is 1 μm higher than the top of the saw blade. (FIG. 1B).

Resin 1 is cured by irradiating the resin 1 leveled to a flat surface with ultraviolet rays having a wavelength of 360 μm and an intensity of ² mW / cm ² for 25 seconds. In this state, the resin 1 is cured to a longitudinal elastic modulus of 500 Mpa (FIG. 1 (c)). A required amount of the second resin 6 made of the same material as that of the resin 1 is dropped on this (FIG. 1D). On top of this, the glass substrate 7 having a flat resin contact surface 7a contacts the liquid. The glass substrate hits the outer peripheral abutting portion 2b of the mold which is 4 μm higher than the top of the saw blade, and the thickness of the second resin 6 on the saw blade is 3 μm (FIG. 1 (e)). In this state, the first resin 1 and the second resin 6 are cured by irradiating the glass substrate 7 with ultraviolet rays 8 having a wavelength of 360 μm and an intensity of 50 mW / cm ² for 240 seconds (FIG. 1F).

  Thereafter, the ejector 9 is brought into contact with the outer peripheral portion 7b of the glass substrate and lifted up, whereby the cured resin 10 is peeled off from the mold 2, and the cured first and second resins 10, 11 and the glass substrate 7 are integrated. Thus obtained composite optical element 12 is obtained.

  The obtained element has no sink marks or the like on the surface of the resin 10 forming the portion on the sawtooth, and the shape accuracy is good, and the refractive index nd of the cured second resin 11 is 1.6358, the resin The refractive index nd of the resin 10 irradiated with ultraviolet rays 50 mJ more than 11 is 1.6358, which is almost the same value, and the refractive index difference between the resins 11 and 10 is within the measurement error, so that the optical performance as a diffractive optical element is sufficient. The specification was met.

<Comparative Example 1>
As Comparative Example 1, as shown in FIG. 2, the resin was not divided into two layers and cured, and the first resin curing step of Example 1 was omitted. That is, a required amount of resin 13 (the sum of the first resin and the second resin amount in Example 1 above) is dropped on the mold 2 (FIG. 2A), and the flat glass substrate 7 is wetted. (FIG. 2 (b)), first, ultraviolet rays having a wavelength of 360 nm with an intensity of ² mW / cm ² are irradiated for 25 seconds through a glass substrate, and then ultraviolet rays with 50 mW / cm ² are irradiated for 240 seconds (FIG. 2 (c)). Then, the resin was peeled from the mold (FIG. 2D) to obtain a composite optical element 14 integrated with the glass substrate. However, the resin surface of this element has sink marks on the slopes of the sawtooth portion, and it was not in a state where it can be used as an optical element.

<Comparative example 2>
As Comparative Example 2, the first resin was cured by irradiating ultraviolet rays having a wavelength of 360 μm with an intensity of ² mW / cm ² for 10 seconds with respect to the manufacturing method of Example 1 to cure the first resin. Was produced by the same method except that the longitudinal elastic modulus was less than 100 MPa. On the resin surface of this element, sink marks were generated on the slopes of the sawtooth portion. When the irradiation time was 20 seconds, the longitudinal elastic modulus of the first resin was 100 MPa, and no sink marks were generated.

<Comparative Example 3>
As a comparative example 3, the first resin is cured by irradiating ultraviolet rays having a wavelength of 360 μm with an intensity of ² mW / cm ² for 150 seconds with respect to the manufacturing method of the first embodiment, thereby curing the resin 1. It was produced in the same manner except that the longitudinal elastic modulus of the was 2000 MPa. Although there was no sink in this element, residual stress was generated in the resin due to the difference in the amount of cure shrinkage, resulting in a decrease in optical performance due to birefringence. When the irradiation time was set to 100 sec, the longitudinal elastic modulus was 1500 MPa, the difference in curing shrinkage was small, and birefringence did not occur.

  FIG. 3 is a schematic view showing a manufacturing method of Example 2, and is a manufacturing method of a microlens as shown in FIG. 3 in FIG. 3 is an energy curable resin before curing, 16 is a mold for molding the curved surface of the microlens, 17 is a spatula-shaped member for leveling the dropped resin on a plane, To move. 18 is an ultraviolet ray, 19 is a first resin cured to a longitudinal elastic modulus of 500 MPa, 20 is a light energy curable resin made of the same material as the energy curable resin 15, 21 is a glass substrate, 22 is an ultraviolet ray, and 23 is a resin from the mold. It is lifted up by a mechanism (not shown) with an ejector for peeling off. Reference numerals 24 and 25 denote cured first and second resins. Reference numeral 26 denotes a composite optical element in which the resin and the glass substrate are integrated.

  A required amount of a liquid light energy curable resin is dropped on the mold 16 (FIG. 3A). The mold 16 has a large number of recesses with a curvature radius of 120 μm and a depth of 180 μm on the surface, and FIG. 3 shows a part thereof. This resin is flattened using a spatula 17, and the spatula is moved over the mold in a state where it hits the outer peripheral abutting part 16b of the mold 16 which is 30 μm higher than the flat part 16a of the mold 16. The thickness of the flat portion 15a is equalized to 30 μm (FIG. 3B).

The resin 15 is cured by irradiating the resin 15 leveled to a flat surface with ultraviolet rays having a wavelength of 360 μm and an intensity of ² mW / cm ² for 25 seconds. In this state, the resin 19 is cured to have a longitudinal elastic modulus of 500 Mpa (FIG. 3C). A required amount of a second resin made of the same material as that of the resin 15 is dropped on this (FIG. 3D). A glass substrate 21 having a flat resin contact surface 21a contacts the liquid. The glass substrate hits the outer peripheral abutting portion 16c of the mold which is 50 μm higher than the mold flat portion 16a, and the thickness of the second resin 20 is 20 μm (FIG. 3E). In this state, the first resin 15 and the second resin 20 are cured by irradiating the glass substrate 21 with ultraviolet rays 22 having a wavelength of 360 μm and an intensity of 50 mW / cm ² for 240 seconds (FIG. 3F).

Thereafter, the cured resin 24 is peeled off from the mold 16 by lifting the ejector 23 against the outer peripheral portion 21b of the glass substrate and lifting it up.
A composite optical element 26 in which the second resins 24 and 25 and the glass substrate 21 are integrated is obtained.

  The obtained element was free from sink marks or the like on the convex portion 26a of the microlens, had good shape accuracy, and the refractive index nd of the cured resin 25 was 1.6358, which was irradiated with ultraviolet rays 50 mJ more than the resin 25. The refractive index nd of the resin 24 was 1.6358, which is almost the same value, and the difference in refractive index between the resins 24 and 25 was within the measurement error, and the optical performance as the imaging microlens sufficiently satisfied the specifications.

<Comparative example 4>
As Comparative Example 4, as shown in FIG. 5, the resin was not divided into two layers and cured, and the first resin curing step of Example 2 was omitted. That is, a required amount of resin 27 (the sum of the first resin and the second resin amount in Example 2 above) is dropped onto the mold 16 (FIG. 5A), and the flat glass substrate 21 is wetted. (FIG. 5 (b)), the glass substrate is first irradiated with ultraviolet light having a wavelength of 360 nm of ² mW / cm ² for 25 seconds, and then irradiated with ultraviolet light of 50 mW / cm ² for 240 seconds (FIG. 5 (c)). Then, the resin was peeled from the mold (FIG. 5D) to obtain a composite optical element 28 integrated with the glass substrate. However, sink marks are generated in the curvature portion 28a of this element, and it cannot be used as an optical element.

<Comparative Example 5>
As a comparative example 5, the resin 15 is cured by irradiating the first resin with ultraviolet rays having a wavelength of 360 μm and an intensity of ² mW / cm ² for 10 seconds as compared with the manufacturing method of the second embodiment. Was produced by the same method except that the longitudinal elastic modulus was less than 100 MPa. On the resin surface of this element, sink marks were generated on the slopes of the sawtooth portion. When the irradiation time was 20 seconds, the longitudinal elastic modulus of the first resin was 100 MPa, and no sink marks were generated.

<Comparative Example 6>
As Comparative Example 6, the resin 15 was cured by irradiating the first resin with ultraviolet light having a wavelength of 360 μm and an intensity of ² mW / cm ² for 150 seconds as compared with the manufacturing method of Example 2 to obtain the first resin. It was produced in the same manner except that the longitudinal elastic modulus of the was 2000 MPa. Although there was no sink in this element, residual stress was generated in the resin due to the difference in the amount of cure shrinkage, resulting in a decrease in optical performance due to birefringence. When the irradiation time was set to 100 sec, the longitudinal elastic modulus was 1500 MPa, the difference in curing shrinkage was small, and birefringence did not occur.

<Comparative Example 7>
As Comparative Example 7, as shown in FIG. 6 with respect to Example 2, the first resin was dropped and then molded without being even on a flat surface. That is, after dripping a required amount of resin onto the mold 16 (FIG. 6A), the first resin was cured as it was (FIG. 6B). At this time, the cured resin 29 had a convex surface with a surface height of about 30 μm. Thereafter, the second resin is dropped (FIG. 6 (c)), and the flat glass substrate 21 is wetted (FIG. 6 (d)), and then the intensity at a wavelength of 360 nm is initially ² mW / cm ² over the glass substrate. The composite type optical element integrated with the glass substrate by irradiating the ultraviolet ray of 100 sec and then irradiating the ultraviolet ray of 50 mW / cm ² for 240 sec (FIG. 6E) and peeling the resin from the mold (FIG. 6F). 30 was obtained.

  In this element, there was no sink in the curvature portion, but birefringence corresponding to the shape of the first layer was generated in the resin, and required optical characteristics could not be obtained. This is because the shape of the interface between the first resin and the second resin is a flat surface in the second embodiment, but is a curved surface in the comparative example 7, and is cured and contracted between the first resin and the second resin. Residual stress due to the difference in amount was generated non-uniformly, and the optical performance was affected although the amount of birefringence was small. Furthermore, when the same method was repeated 5 times, the shape of the convex portion of the first resin was not stable, and the optical performance was not stable accordingly.

  From the above, the first resin is leveled into a required shape, and after the surface is free and the longitudinal elastic modulus of the resin is cured to 100 MPa or more and 1500 MPa or less, the second resin is dropped and cured through the glass substrate, By releasing the mold, there is no sink on the surface, and it is possible to prevent a decrease in optical performance due to a difference in the cured state between the first resin and the second resin.

  When the composite optical element was molded 100 times by the method of Example 1, when the resin was peeled from the mold in 5 of them, the first resin and the second resin were not peeled off at the interface between the mold and the resin. It peeled at the interface and the second resin remained in the mold.

  As Example 3, when the resin material was changed to an anaerobic resin and the first resin was cured in the atmosphere 100 times in the same manner as in Example 1, it was molded 100 times. There was no peeling at the interface between the first resin and the second resin, and a molded product with good shape accuracy free from sink marks could be obtained.

  In order to improve the diffraction efficiency of the diffractive optical element as Example 4, it was molded using resins having different optical constants. Since the resin used here has a low light transmittance, this material is used as the first resin, and a resin having a high light transmittance is used as the second resin, which is molded in the same manner as in Example 1. Although the sawtooth-shaped portion had no sink marks and the shape accuracy was good, the required optical performance could not be obtained. This is because the refractive index is different between the first resin and the second resin, and light is refracted at this interface. Therefore, optical design was performed in consideration of this amount of refraction, and molding was performed using a mold in which the height, pitch, and radius of curvature of the saw blade were changed, and the obtained optical element satisfied the required optical performance.

<Comparative Example 8>
As Comparative Example 8, it was molded in a non-spherical shape with respect to Example 1 described above. Although there was no sink or the like, the shape accuracy was good. However, as described in Comparative Example 7, as a matter of course, the surface shape of the first resin is not stable, and the amount of refraction of light due to this changes. The required optical characteristics could not be obtained due to the birefringence corresponding to the shape of the resin.

  From the above, the first resin is leveled into a required shape, and after the surface is free and the longitudinal elastic modulus of the resin is cured to 100 MPa or more and 1500 MPa or less, the second resin is dropped and cured through the glass substrate, By releasing the mold, it is possible to prevent the optical performance from being deteriorated due to the surface sink, and different resins can be used for the first resin and the second resin. Manufacture is possible.

It is the schematic which shows the shaping | molding process in Example 1 of this invention. 6 is a schematic view showing a molding process of Comparative Example 1. FIG. It is the schematic which shows the shaping | molding process in Example 2 of this invention. It is a figure which shows the element shape | molded in Example 2 of this invention. 10 is a schematic view showing a molding process of Comparative Example 4. FIG. 10 is a schematic view showing a molding process of Comparative Example 7. FIG. It is sectional drawing of the microlens suitable for the manufacturing method of this invention. It is sectional drawing of the diffraction grating suitable for the manufacturing method of this invention.

Explanation of symbols

1,6,13,15,20,27,29 Light energy curable resin resin 2,16 type 3,17 spatula 4,8,18,22,28 UV light 5,10,11,19,24,25 cured Resin 7,21 Glass substrate 9,23 Ejector 12,14,26,28,30 Molded composite optical element

Claims (3)

In the manufacturing method of a composite optical element in which a light energy curable resin is molded and cured using a mold on a glass substrate, and integrated,
A step of dripping the first resin onto a mold, a step of making the first resin into a required shape such as a flat surface, a spherical surface, a step of curing the first resin to a longitudinal elastic modulus of 100 MPa to 1500 MPa, Dropping the second resin onto the first resin; contacting the glass substrate on the second resin; curing the second resin; and removing the resin from the mold An optical element manufacturing method comprising the steps of:   The method of manufacturing an optical element according to claim 1, wherein the first resin is an anaerobic resin, and the first resin is cured in an oxygen-containing atmosphere.   The method for manufacturing an optical element according to claim 1, wherein the first and second resins are different.

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