JP2006095722A - Optical element and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of burr caused by the outflow of a resin to an outer periphery by uniformizing the thickness of a molded layer in the flattening molding on an optical surface for forming a braized type diffraction lattice. <P>SOLUTION: A stamper mold, a resin material and a photoirradiator are used to perform the replica molding of a first molding support part, which has a gap enabling the outflow of the resin material between the relief pattern surface becoming the diffraction lattice and an outer peripheral part, and a second molding support part, which can suppress the outflow of the resin in the outer peripheral part, on an optical base material using the photoirradiator so that the second molding support part is slightly higher than the first molding support part by several μm. A ring-shaped member is arranged so as to cover the first molding support part on a substrate and, especially a strong member is formed on the first molding support part by two-body constitution to impart flattening pressure. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an optical element obtained by flattening a diffractive optical surface and a method for molding the optical element.

  In general, a large pressure is applied to the surface of the optical substrate facing the molding surface from the viewpoint of preventing damage such as scratches and cracks. Similarly, in the replica molding process using the 2P method, the liquid crystal substrate technology, and the semiconductor manufacturing technology, it is rare to apply a pressure of 10 kgf or more to the substrate.

  In recent years, optical information recording media such as CDs and DVDs have become widespread. In the optical recording medium, the support base 31 and the light transmissive sheet 33 are joined by the ultraviolet curable resin layer 32. At that time, pressure is applied with a constant pressure, and the thickness of the adhesive layer is made uniform to about 30 μm or less. The technique to do is known (refer patent document 1). The aim of this technique is to suppress the occurrence of warping of the optical recording medium by making the thickness of the light transmission layer uniform, and to suppress the optical heterogeneity of the light transmission layer, particularly the increase of birefringence. . At the same time, the protrusion of the adhesive layer to the reading surface is not allowed.

  On the other hand, in the replica transfer technique in which a planarization layer is formed on the diffractive optical surface of a blazed diffractive optical element, conventionally, as shown in FIG. A pressure of as much as 300 kgf is applied, and an ultraviolet curable resin is spread and filled between the diffractive optical surface 22a and the mold 23, and then irradiated with light. Thereafter, a process of releasing the pressure applied to the substrate and releasing the mold is performed.

Patent Document 2 describes an example in which a flattened layer is formed on a diffractive optical surface on a curved surface, and a diffractive optical surface on the curved surface is further formed thereon as a diffractive optical element having a laminated structure.
JP 2001-209973 A JP 2002-107520 A

  However, in the example of the optical recording medium of Patent Document 1, the substrate is a resin, and the application pressure required to make the adhesive layer uniform is about 1 to 2 atm. At the same time, the protrusion of the adhesive layer to the reading surface is controlled. It is also easy.

  In the replica transfer technique in which a planarizing layer is formed on the diffractive optical surface of a blazed diffractive optical element, in the step of applying pressure, the center of the substrate glass 21 that is a rigid body is bent as shown in FIG. There was a problem that the planarization layer was molded in a state outside the thickness standard of the planarization layer (t1> t2> t3> t4). Due to this problem, wavefront aberration (spherical aberration) occurs optically due to film thickness unevenness between the center and the periphery, and optical performance deteriorates.

  Further, since 300 kgf of pressure for expanding the resin is required, the resin flow cannot be controlled, and there is a problem that the resin protrudes from the mold and generates burrs.

Alternatively, according to the diffractive optical element having the laminated structure of Patent Document 2, an extremely fine structure in which the air interval of the laminated structure is set to 1.5 ± ^−1.3 ₊ 1.5 μm is required. When the film thickness of the film increases, contact with the laminated diffractive optical surface occurs.

  Therefore, in view of these problems, the present invention effectively disperses the flattening pressure on the substrate glass, homogenizes the flattening layer, prevents the outflow of the resin liquid during pressure filling, and improves quality and production. It is to provide an optical element having excellent properties and a molding method thereof.

  The optical element of the invention according to claim 1 is a second molding that supports a planarizing pressure on a mold in a planarization molding in which a resin is dropped onto a diffractive optical surface, filled and cured to form a planarized surface. The support part and the first molding support part that supports the bending of the substrate on the mold inside the second molding support part are replica-molded on the substrate.

  The optical element of the invention according to claim 2 is the optical element of the invention according to claim 1, wherein the second molding support portion first comes into contact with the mold surface as the pressurization proceeds, and then the first element The molding support portion is in contact with the mold surface.

  The optical element of the invention according to claim 3 is the optical element of the invention according to claim 1 or 2, wherein the first molding support portion has a gap through which a part of the filling resin can flow out to the outer periphery. The second molding support part does not have a gap for resin outflow.

  According to a fourth aspect of the present invention, there is provided a flattening molding method for supporting a flattening pressure on a mold in a flattening molding in which a resin is dropped, filled and cured on a diffractive optical surface to form a flattened surface. The bending of the substrate is regulated by the forming support portion of the substrate and the first forming support portion that supports the bending of the substrate on the mold inside the second forming support portion.

  According to a fifth aspect of the present invention, there is provided a flattening molding method in which a resin is dropped on a diffractive optical surface, filled and cured to form a flattened surface, and a ring shape for applying a flattening pressure on a substrate The member has an outer peripheral end disposed on the first molding support portion and the second molding support portion, and the substrate does not contact the inner peripheral end of the ring-shaped member to the first molding support portion. The structure is characterized in that the two parts are made of a member stronger than other regions.

  According to the present invention, even if the substrate deformation due to the applied pressure occurs only a few μm, the thickness of the flattening layer is made uniform by the two-step configuration of the pressure support member on the replica surface, and the optical performance is achieved by the generation of spherical aberration due to uneven thickness. In the case of a diffractive optical element having a laminated structure, an optical element that reduces the original air gap between the planarizing layer and the laminated diffractive optical surface and does not cause contact between the optical surfaces, and The molding method can be provided.

  In addition, the outer peripheral portion of the pressure support member on the replica surface suppresses the outflow of resin during filling, prevents the occurrence of burrs, and thus provides an optical element that reduces yield and improves production efficiency, and a molding method therefor I can do it.

  In the embodiment of the present invention, the above configuration is applied, and in the flattening molding of the blazed diffraction grating to the diffractive optical surface, the pressure supporting member on the replica surface is generated even if the substrate deformation due to the applied pressure occurs only a few μm. The diffractive optical surface laminated with the flattening layer in the case of a diffractive optical element having a laminated structure, in which the thickness of the flattening layer is made uniform by the two-step structure of It is possible to realize an optical element and a molding method thereof that reduce the original air gap between the optical surfaces and cause no contact between optical surfaces.

  Moreover, the outer peripheral part of the pressure support member on the replica surface suppresses the outflow of resin during filling and prevents the generation of burrs, thus reducing the yield and improving the production efficiency, and an optical element and its molding method are realized. Is possible.

  Hereinafter, the present invention will be described with reference to examples.

<First embodiment>
FIG. 1 is a cross-sectional view of the configuration of the first embodiment of the present invention, FIG. 2A is a cross-sectional view showing a state before flattening in the first embodiment, and FIG. It is a composition sectional view showing change. FIG. 3 is a front view of the replica transfer surface on the substrate glass in the first embodiment of the present invention. In the figure, reference numeral 1 denotes a substrate glass that serves as a base of an optical element, 2 denotes a resin member that forms a blazed diffraction grating, 3 denotes a flattening die for transfer-molding a flattened surface, and 4 denotes a flattening pressure. A rigid member 7 is provided on the diffractive optical surface 2a, and a flattening layer for integrally molding a resin material.

  Substrate glass 1 A general glass material S-BSL7 is used as an optical glass substrate. The resin member 2 uses a photo-curing reaction type monomer resin, and is applied to the relief pattern transfer surface 2a and the flattening die 3 as shown in FIG. The first molding support portion 5 whose contact surface forms a columnar shape with a circular boss and the second molding support that forms an annular rib that is configured to be several μm higher than the first molding support portion (the h portion in FIG. 2A). The part 6 is replica-molded in advance. Here, the resin member 2 may be a thermosetting resin or a photocuring / thermosetting resin.

  The resin material used for the planarizing layer 7 is a photocurable monomer resin that is fluidized at a constant temperature of room temperature or higher. The resin material has many different characteristics such as optical properties (refractive index, transmittance) and physical properties (viscosity, curability, linear expansion). By this resin material, the flattening layer 7 is replica-molded with a uniform thickness between the diffractive optical surface 2a and the flattening die 3. As the flattening die 3, a high-precision carbide polishing die having a concave curvature shape with Newton, asphalt, and habits of 0.5 or less is used. The rigid member 4 may be a hollow double-side polished glass, but in order to finely control the amount of deflection to the substrate glass 1, the inner peripheral upper part is a cemented carbide abrasive 4a and the outer peripheral lower part is a stainless steel abrasive 4b. The two-body configuration was used.

  Next, the planarization molding method will be described in order with reference to FIGS.

  The resin forming the flattening layer 7 is held in the syringe of the dispenser while being heated at a constant temperature, and a predetermined discharge time is set, and about 30 mg of resin is dropped onto the center of the diffractive optical surface 2a. Subsequently, the flattening mold 3 is brought into light contact with the resin member 2 forming the diffraction grating. On the cemented carbide abrasive 4a of the rigid member 4, pressure sensors (not shown) are arranged in three equal parts. When the apparatus is activated, a hydraulic cylinder of a not-shown pressurizing apparatus having a compliance configuration (automatic tilt correction) gradually pressurizes, and finally applies a pressurizing force of 100 kgf / (1 pressurizing sensor) (F). When 300 kgf of pressurizing force corresponding to three pressure sensors is transmitted to the stainless steel abrasive 4b of the rigid member 4 (f1) and the substrate glass 1 receives the pressurizing force (f3), the flattening layer resin 7 is filled. As a result, the tip of the second molding support portion 6 comes into contact with the mold surface of the flattening mold 3 (f4). The substrate glass 1 begins to bend in a convex shape of only a few μm, but since the applied pressure is maintained constant, the substrate glass 1 starts to bend in a direction to correct the middle convex shape, and the substrate glass 1 eventually has a concave shape of only a few μm. At the same time, the top of the first molding support 5 comes into contact with the mold surface of the flattening mold 3 (f5). Here, the stainless steel abrasive 4b of the rigid member 4 does not directly transmit the applied pressure from the cemented carbide abrasive 4a to the substrate glass 1 and relaxes (f2), so that the substrate glass 1 is not damaged. The substrate glass 1 works to relax and advance the correction from the middle convex state, and the correction speed of the substrate glass 1 and the resin filling speed of the flattening layer 7 can be synchronized. The surplus resin flows out from the gap between the first molding support portions 5, is restrained by the second molding support portion 6, and stays in the portion 2b between the second molding support portion and the first molding support portion.

During this time, the resin of the planarizing layer 7 is filled in about 2 minutes, and the layer thicknesses t1, t2, t3, and t4 are equalized uniformly. Thereafter, the resin is cured by irradiating the substrate glass 1 side with ultraviolet energy (1 mW / cm ² × 10 sec + 10 mW / cm ² × 10 sec + 100 mW / cm ² × 100 sec) set with a predetermined profile while maintaining the pressurized state, Immediately after that, the pressure device is operated to release the pressure state. Next, the mold is released by a mold ejector, and the periphery of the flattened surface is auxiliary-cured with the irradiation energy at 1/10 second of the profile of the previous process.

  The flattened layer formed in this way makes the thickness of the flattened layer uniform by the two-step structure of the pressure support member on the replica surface even if the substrate deformation due to the applied pressure occurs only a few μm, and the generation of spherical aberration due to uneven thickness Therefore, the optical performance is not deteriorated.

  Further, since the outer peripheral portion of the pressure support member on the replica surface suppresses the outflow of the resin during filling and prevents the generation of burrs, the yield is reduced and the production efficiency is improved.

<Second embodiment>
The second embodiment of the present invention is a modification of the first embodiment shown in FIG. 4 in which the first molding support portions 15 are replica-molded so as to be arranged in a constant arc shape. Since the cross-sectional configuration and the configuration of other members are the same as those in the first embodiment, description thereof will be omitted.

  The effect of this embodiment is that the amount by which the substrate glass is bent into a concave shape can be further controlled in the pressing step described in the flattening molding method of the first embodiment. Further, compared to the first embodiment, since the number of gaps between the plurality of first molding support portions is small, it is suitable for setting of resin material (physical properties, dripping amount, etc.) that does not require much resin outflow.

It is sectional drawing which shows the structure of the 1st Example of this invention. (A) is a structure sectional view showing the state before flattening of the 1st example of the present invention, and (b) is a structure sectional view showing change of the applied pressure of the 1st example of the present invention. It is the partial plane enlarged view which replica-molded the diffraction optical surface and the 1st, 2nd shaping | molding support part of the 1st Example of this invention on the substrate glass. It is the partial plane enlarged view which replica-molded the diffraction optical surface and the 1st, 2nd shaping | molding support part of the 2nd Example of this invention on the substrate glass. It is sectional drawing which shows the structure of a prior art example. It is sectional drawing which shows the structure of an optical information recording medium.

Explanation of symbols

1, 11, 21 Substrate glass 2, 12, 22 Resin material 2a, 12a, 22a Optical surface (relief pattern)
2b, 12b Gap 3, 23 between first molding support part and second molding support part Flattening die 4 Rigid member 4a Cemented carbide abrasive 4b Stainless steel abrasive 5, 15, 25 First molding support 6 , 16 2nd shaping | molding support parts 7 and 27 Planarization layer 31 Base | substrate 32 Ultraviolet curable resin layer 33 Light transmissive sheet

Claims (5)

  In flattening molding for forming a flattened surface by dripping, filling, and curing a resin on the diffractive optical surface, the second molding support portion for supporting the flattening pressure on the mold, and the bending of the substrate is the second. An optical element obtained by replica-molding a first molding support portion, which is supported on a mold inside the molding support portion, on a substrate.   2. The optical device according to claim 1, wherein as the pressurization proceeds, the second molding support portion first contacts the mold surface, and then the first molding support portion contacts the mold surface. element.   The first molding support part has a gap through which a part of the filled resin can flow out to the outer periphery, and the second molding support part does not have a gap for resin outflow. The optical element according to claim 2.   In flattening molding for forming a flattened surface by dripping, filling, and curing a resin on the diffractive optical surface, the second molding support portion for supporting the flattening pressure on the mold, and the bending of the substrate is the second. A method for molding an optical element, comprising: controlling bending of a substrate by a first molding support portion supported on a mold inside the molding support portion.   In flattening molding in which a resin is dropped, filled and cured on the diffractive optical surface to form a flattened surface, the ring-shaped member for applying a flattening pressure on the substrate has an outer peripheral end at the first molding support portion. Arranged between the upper part and the second molding support part, the substrate non-contact part from the inner peripheral end of the ring-shaped member to the first molding support part is composed of two members that are stronger than other regions. An optical element molding method characterized by the above.

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