JP2007309964A - Complex optical element and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a complex optical element having excellent mass productivity and excellent reliability by preventing the peel-off of a joint surface of various kinds of materials to each other. <P>SOLUTION: A second optical part 20 is joined to an optically functional surface 11 of a first optical part 10 and a third optical part 30 is joined to an optically functional surface 22 of the second optical part 20 using the first to the third optical parts 10, 20 and 30 respectively having linear thermal expansion coefficient α1, α2 and α3 satisfying α3≥α2≥α1. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a composite optical element and a manufacturing method thereof.

  Conventionally, a composite optical element formed by joining different kinds of materials (for example, glass and resin) with a thermoplastic adhesive is known (for example, see Patent Document 1).

According to such a composite optical element, for example, a relief pattern (diffraction surface) is formed on the optical functional surface of a resin that is easy to create a fine shape, while a portion requiring mechanical strength and resistance to environmental changes is made of glass. This makes it possible to improve the degree of freedom of optical design and realize a highly functional optical system.
JP 54-73859 A

  However, when glass and resin are bonded by press molding, internal stress is generated on the bonding surface between the glass and the resin due to volume shrinkage caused by the curing of the resin, and the resin is peeled off at the bonding surface due to a decrease in shape accuracy. There may be various adverse effects.

  This invention is made | formed in view of this point, The place made into the objective is to prevent the peeling in the joint surface of dissimilar materials, and to provide the composite optical element excellent in reliability.

  That is, the composite optical element of the present invention is bonded to the first optical unit, the second optical unit bonded to the optical functional surface of the first optical unit, and the optical functional surface of the second optical unit. A linear optical expansion coefficient α1 of the first optical unit, a linear thermal expansion coefficient α2 of the second optical unit, and a linear thermal expansion coefficient α3 of the third optical unit are α3 ≧ α2 ≧ It is characterized by being set to satisfy the condition of α1.

  In this specification, the linear thermal expansion coefficients α1, α2, and α3 are values measured under temperature conditions of 100 ° C. to 300 ° C.

  Further, the method for manufacturing a composite optical element of the present invention includes a procedure for preparing first to third optical units having linear thermal expansion coefficients α1, α2, and α3 satisfying a condition that α3 ≧ α2 ≧ α1, The second optical unit is bonded to the optical functional surface of the optical unit by press molding, and the third optical unit is bonded to the optical functional surface of the second optical unit by press molding. It is what.

  As described above, according to the present invention, it is possible to provide a composite optical element that is excellent in reliability by preventing peeling at a joint surface between different materials.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or its application.

  FIG. 1 is a cross-sectional view showing a configuration of a composite optical element according to an embodiment of the present invention. As shown in FIG. 1, the composite optical element 1 includes a first optical unit 10, a second optical unit 20, and a third optical unit 30.

  The first optical unit 10 is composed of a biconvex lens having a convex aspherical optical function surface (lens surface) 11 and an optical function surface (lens surface) 14. Each of these optical function surfaces 11 and 14 is formed of a refractive surface having only a refractive action.

  Further, an edge plane 15 that protrudes outward in the lens circumferential direction from the optical function surface 11 is provided at the peripheral edge of the first optical unit 10.

  The second optical unit 20 is constituted by a meniscus lens joined to the first optical unit 10 on the optical functional surface 11. The optical functional surface 21 on the first optical unit 10 side in the second optical unit 20 is formed with a smooth surface corresponding to the optical functional surface 11. Similarly, the optical functional surface 22 facing the optical functional surface 21 is formed of a refractive surface having only a refractive action.

  The third optical unit 30 is constituted by a meniscus lens joined to the second optical unit 20 on the optical functional surface 22. The optical functional surface 31 on the second optical unit 20 side in the third optical unit 30 is formed of a refractive surface corresponding to the optical functional surface 22.

  On the other hand, the optical functional surface 32 facing the optical functional surface 31 includes a smooth surface portion 33 provided at the center portion and the outer peripheral portion, and an uneven surface portion 34 provided so as to be adjacent to the smooth surface portion 33. Specifically, the concavo-convex surface portion 34 is configured by a diffractive surface having a sawtooth cross section.

  In the present specification, “uneven surface” refers to a surface in which a plurality of concave and convex portions are arranged periodically or aperiodically. Further, on the uneven surface, the boundary between the concave portion and the convex portion may not be a ridge line, and may be a rounded shape such as a chamfered shape.

  In the present embodiment, since the optical functional surface 32 of the third optical unit 30 is constituted by the smooth surface portion 33 and the uneven surface portion 34 as described above, the optical functional surface in the central region where the smooth surface portion 33 is provided. The optical power of 32 and the optical power of the optical functional surface 32 in the peripheral region where the uneven surface portion 34 is provided can be made different. Thus, for example, by focusing light of a certain wavelength using the central region and condensing light of a different wavelength using the peripheral region, the lights having different wavelengths are focused at the same focal length. can do.

  Here, the 1st thru | or 3rd optical parts 10, 20, and 30 are comprised with the material from which a linear thermal expansion coefficient differs, respectively. In the present invention, when the linear thermal expansion coefficient α1 of the first optical unit, the linear thermal expansion coefficient α2 of the second optical unit, and the linear thermal expansion coefficient α3 of the third optical unit, the condition of α3 ≧ α2 ≧ α1 is satisfied. It is set to meet.

  Specifically, the first optical unit 10 is made of a glass material or a resin material with emphasis on hygroscopicity, heat resistance, etc. rather than fine moldability.

  The second optical unit 20 absorbs the difference in linear thermal expansion that occurs between the first optical unit 10 and the third optical unit 30, and functions to increase peeling and the element reliability after molding. It bears and is composed of a glass material or a resin material.

  Since the third optical unit 30 forms a fine diffractive structure, the third optical unit 30 is preferably made of a resin material with an emphasis on formability. For example, a cycloolefin polymer material (registered trademark ZEONEX manufactured by Nippon Zeon Co., Ltd.) can be used.

  For example, when the third optical unit 30 is directly bonded on the first optical unit 10, the linear thermal expansion coefficients α 1 and α 3 are greatly different between the optical units 10 and 30. In addition, a large distortion may occur between the first optical unit 10 and the third optical unit 30.

  Further, when the temperature rises or falls when the composite optical element 1 is used, distortion occurs between the first optical unit 10 and the third optical unit 30, and the third optical unit 30 becomes the first optical unit. There is a risk of peeling from 10.

  When the third optical unit 30 is a thermoplastic resin and the composite optical element 1 is produced by pressing with the first optical unit 10, the manufactured composite optical element 1 has a large strain. In addition to the remaining optical uniformity, the third optical unit 30 may be peeled off from the first optical unit 10 due to residual strain.

  On the other hand, in the present embodiment, the linear thermal expansion coefficient α1 of the first optical unit 10 and the linear thermal expansion of the third optical unit 30 are between the first optical unit 10 and the third optical unit 30. A second optical unit 20 having a linear thermal expansion coefficient α2 between the coefficient α3 is provided. For this reason, the difference between the optical parts joined to each other is small. Therefore, the problems such as peeling of the third optical unit 30 and remaining strain are effectively suppressed as described above.

  As described above, according to the composite optical element 1 according to the present embodiment, it is possible to suppress peeling at the joint surface between different materials. In addition, the degree of freedom in optical design is not only greatly expanded, but also mass productivity is improved, so that it is possible to supply inexpensive optical elements, so that it can be expected to be applied to various fields such as lenses, mirrors, and prisms. .

  Note that each of the first optical unit 10, the second optical unit 20, and the third optical unit 30 is preferably made of a material having a refractive index with respect to d-line of 1.5 or more. Thus, NA can be enlarged by comprising with a high refractive material whose refractive index is 1.5 or more.

  Further, by configuring with a material having a light transmittance of 90% or more at a light wavelength of 400 nm or more, for example, the application range to a BD (registered trademark) apparatus having a wavelength of 405 nm of laser light to be used can be expanded. it can. In addition, the measured value of light transmittance is a value when it carries out with respect to the sample of thickness 10mm by which both surfaces were mirror-polished.

  Next, a method for manufacturing the composite optical element 1 according to the present embodiment will be described with reference to FIGS. In addition, here, the manufacturing method of the composite optical element 1 comprised by the 1st optical part 10 which consists of glass substantially, and the 2nd and 3rd optical parts 20 and 30 which consist of thermosetting resin substantially. Will be described as an example.

  First, the first optical unit 10 is manufactured. Specifically, the first optical unit 10 is manufactured using a pair of molds (lower mold 41 and upper mold 45) shown in FIG. The lower mold 41 has a concave molding surface 42 corresponding to the shape of the optical functional surface 11 of the first optical unit 10 on the top surface. On the other hand, the upper mold 45 is constituted by a columnar body having a molding surface 46 facing the lower mold 41 as a top surface. The molding surface 46 is formed in a concave shape corresponding to the shape of the optical function surface 14.

  Then, using these lower mold 41 and upper mold 45, the glass preform 40 processed into a ball shape or a shape and dimension approximately similar to the first optical unit 10 is heated and pressed (heat pressed). Specifically, the glass preform 40 is disposed between the lower mold 41 and the upper mold 45.

  Next, the glass preform 40 is heated to near the softening temperature to be softened, and the upper mold 45 is displaced relative to the lower mold 41 in the direction of the lower mold 41 to lower the softened glass preform 40. The first optical unit 10 is obtained by pressing with the molding surface 42 of the mold 41 and the molding surface 46 of the upper mold 45 (see FIG. 2B). Then, the first optical unit 10 is completed by cooling to a predetermined temperature (for example, glass transition temperature -150 ° C. to room temperature).

  Next, as shown in FIG. 3A, a softened state is formed on the molding surface 52 using a molding die 51 having a concave molding surface 52 corresponding to the shape of the optical functional surface 22 of the second optical unit 20. The thermosetting resin 50 is disposed. Then, the thermosetting resin 50 is pressed using the molding die 51 and the pressing die 55. Specifically, the first optical part 10 molded earlier is pressed with the pressing die 55, and the thermosetting resin 50 disposed on the molding surface 52 of the molding die 51 is moved to a predetermined position with the optical function surface 11. The thermosetting resin 50 is cured by pressing and applying heat to the thermosetting resin 50 in this state.

  In this step, since the thermosetting resin 50 in a softened state before applying heat is very soft compared to the first optical unit 10, the thermosetting resin 50 is used as the optical functional surface of the first optical unit 10. Even if pressed with 11, the shape of the optical functional surface 11 does not change substantially. Further, the thermosetting resin 50 flows in accordance with the shape of the optical function surface 11, and the shape of the optical function surface 11 is suitably transferred. Thereby, the 2nd optical part 20 is joined to the optical function surface 11 of the 1st optical part 10 (refer FIG.3 (b)).

  Next, as shown in FIG. 4A, the heat in a softened state on the molding surface 62 using a molding die 61 having a molding surface 62 corresponding to the shape of the optical function surface 32 of the third optical unit 30. A cured resin 60 is disposed. Here, the molding surface 62 includes a smooth molding surface portion 63 for molding the smooth surface portion 33 of the third optical unit 30 and a concave / convex molding surface portion 64 for molding the concave / convex surface portion 34.

  Then, the thermosetting resin 60 is pressed using the molding die 61 and the pressing die 65. Specifically, the first optical unit 10 and the second optical unit 20 molded earlier are pressed with the pressing mold 65, and the thermosetting resin 60 disposed on the molding surface 62 of the molding mold 61 is changed to the second one. The thermosetting resin 60 is cured by pressing the optical function surface 22 of the optical unit 20 to a predetermined position and applying heat to the thermosetting resin 60 in this state.

  In this way, the first optical unit 10, the second optical unit 20 joined to the first optical unit 10 on the optical functional surface 11, and the second optical unit 20 on the optical functional surface 22. It is possible to obtain a composite optical element 1 including the third optical unit 30 bonded to the substrate (see FIG. 4B).

  In general, glass has a higher softening temperature and higher hardness than resin, so that, for example, as described here, the first optical unit 10 is substantially made of glass, and the second optical unit 10 When the part 20 is substantially made of a resin (for example, a thermoplastic resin or an energy curable resin), the glass first optical part 10 molded into a desired shape as described above is softened as a mold. By pressing and curing the resin in a state and bonding it, it can be molded easily and with high shape accuracy. The same applies to the molding of the third optical unit 30.

  In addition, when an energy curable resin such as an ultraviolet curable resin or an electron beam curable resin is used as the material of the second and third optical units 20 and 30, the curing process can be performed in a short time, so that productivity can be improved. it can. On the other hand, when a thermosetting resin is used as the material of the second and third optical units 20 and 30, the composite optical system can be easily and inexpensively by heating without requiring a large apparatus for irradiating ultraviolet rays or electron beams. Element 1 can be obtained.

  In the present embodiment, the example in which the smooth surface portion 33 is configured by an aspheric surface and the uneven surface portion 34 is configured by a diffractive surface having a sawtooth cross section has been described, but in the present invention, the smooth surface portion 33 is, for example, It may be a flat surface, a spherical surface, a cylindrical surface, an elliptical surface, a toric surface, or the like. The uneven surface portion 34 is, for example, a diffraction surface having a rectangular cross section or a sinusoidal cross section, a lens array surface composed of a plurality of convex or concave lens surfaces, a phase step surface, or an antireflection structure (for example, suppressing reflection). A light reflection preventing surface on which a plurality of cone-shaped projections or cone-shaped recesses arranged at a pitch equal to or less than the wavelength of the light is formed.

  Further, the second and third optical units 20 and 30 are not limited to those formed by press molding. For example, the second and third optical units 20 and 30 are formed on the optical functional surfaces 11 and 22 by a coating method such as a spin coating method or a squeezing method. You may form by making it harden | cure after apply | coating a resin material. Further, the third optical unit 30 may be formed by etching.

  In this embodiment, a biconvex lens is described as an example of a composite optical element. However, the present invention is not limited to this form. For example, a binary optical element, a microlens array element, and a phase step are formed. An optical element or an optical element having SWS (Subwavelength Structure Surface) may be used.

<Modification>
FIG. 5 is a cross-sectional view showing a modification of the composite optical element of the present invention. In the following, the same parts as those in the above embodiment are denoted by the same reference numerals, and only differences will be described.

  As shown in FIG. 5, the composite optical element 2 according to this modification is configured by a biconvex lens, and has a convex aspherical optical function surface (lens surface) 11 and an optical function surface (lens surface) 14. The second optical unit 20 and the third optical unit 30 are stacked and bonded to each other.

  That is, the second optical unit 20 is bonded to the optical functional surface 11 of the first optical unit 10, and the third optical unit 30 is bonded to the optical functional surface 22 of the second optical unit 20. Although it is the same as that of embodiment, in this modification, the 2nd optical part 20 is further joined also to the optical function surface 14 of the 1st optical part 10, and the optical function surface 22 of this 2nd optical part is joined. The third optical unit 30 is bonded.

  Further, the optical function surface 32 of the third optical unit 30 joined to the optical function surface 14 side of the first optical unit 10 is also provided on the smooth surface portion 33 and the smooth surface portion 33 provided at the center portion and the outer peripheral portion thereof. An uneven surface portion 34 provided so as to be adjacent to each other is formed. Specifically, the concavo-convex surface portion 34 is configured by a diffractive surface having a sawtooth cross section.

  As described above, according to the composite optical element 2 according to the modification of the present invention, the second and third optical units 20 and 30 are laminated and bonded to both convex surfaces of the first optical unit 10, respectively. Since a diffractive structure is formed on the optical functional surface, a more complicated optical system can be realized.

  As described above, the present invention provides a highly practical effect that can prevent the separation of the joint surfaces between different materials and provide a composite optical element having excellent mass productivity and reliability. Therefore, it is extremely useful and has high industrial applicability. In particular, it is useful as a composite optical element used in an optical system of an optical disk device and an imaging system such as a digital still camera or a mobile phone.

It is sectional drawing which shows the structure of the composite optical element which concerns on embodiment of this invention. It is sectional drawing for demonstrating the manufacturing method of a 1st optical part. It is sectional drawing for demonstrating the manufacturing method of a 2nd optical part. It is sectional drawing for demonstrating the manufacturing method of a 3rd optical part. It is sectional drawing which shows the modification of the composite optical element of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Composite optical element 2 Composite optical element 10 1st optical part 11 Optical functional surface 14 Optical functional surface 20 2nd optical part 21 Optical functional surface 22 Optical functional surface 30 3rd optical part 31 Optical functional surface 32 Optical functional surface 33 Smooth surface 34 Uneven surface

Claims (10)

A first optical unit;
A second optical unit bonded to the optical functional surface of the first optical unit;
A third optical unit joined to the optical functional surface of the second optical unit,
The linear thermal expansion coefficient α1 of the first optical unit, the linear thermal expansion coefficient α2 of the second optical unit, and the linear thermal expansion coefficient α3 of the third optical unit satisfy the condition of α3 ≧ α2 ≧ α1. A composite optical element characterized by being set to In claim 1,
The optical functional surfaces of the first optical unit are respectively provided on both surfaces of the first optical unit,
The composite optical element, wherein the second optical unit and the third optical unit are laminated and bonded to each of the optical functional surfaces. In claim 1,
At least of the joint surface between the first optical unit and the second optical unit, the joint surface between the second optical unit and the third optical unit, and the optical functional surface of the third optical unit. One is a composite optical element formed on a diffractive surface. In claim 3,
The diffractive surface is formed only on a part of the surface having the diffractive surface. In claim 1,
Each of the first to third optical units is substantially composed of glass or resin. In claim 1,
Each of the first to third optical units is composed of a material having a refractive index with respect to d-line of 1.5 or more. In claim 1,
Each of the first to third optical units is composed of a material having a light transmittance of 90% or more at a light wavelength of 400 nm or more. In claim 1,
The composite optical element, wherein the optical functional surface is a light transmitting surface or a light reflecting surface. In claim 1,
A composite optical element used as a lens, a mirror, or a prism. A procedure for preparing first to third optical units in which linear thermal expansion coefficients α1, α2, α3 satisfy the condition of α3 ≧ α2 ≧ α1;
A procedure of joining the second optical part to the optical functional surface of the first optical part by press molding;
A method of manufacturing a composite optical element, comprising: a step of joining the third optical unit to the optical functional surface of the second optical unit by press molding.

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