JP2007090405A - Laminated optical element, and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated optical element which is formed such that when a plurality of large-area wafers in a state of being laminated and bonded are cut and separated into respective pieces by laser beam, in a process of cutting the plurality of wafers held in a temporarily joined state along cutting lines between the respective pieces, simultaneously only a joining surface peripheral part (non-valid optical area) is bonded; and to provide its manufacturing method. <P>SOLUTION: In the laminated optical elements 1 formed by integrally laminating the plurality of optical elements 2, 3 having similar shapes of the circumference contour, the peripheral edges of faced surfaces of the respective optical elements have a weld joint part 4 formed by welding the respective optical elements. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a laminated optical element formed by laminating a plurality of optical elements, and a manufacturing method thereof, and more particularly, a laminated optical element in which a plurality of optical elements are joined and integrated without using a special adhesive, and a manufacturing method thereof. About.

Optical disc recording / reproducing apparatuses in recent years include optical components compatible with blue-violet lasers (with the same wavelength of 405 nm) such as Blue-ray Disc and HD DVD in addition to DVD (with a wavelength of 660 nm for recording / reproducing) and CD (with the same wavelength of 785 nm). A convertible type compatible with recording media has been proposed and implemented.
In such an optical system used in a recording / reproducing apparatus that can cope with recording / reproducing with different wavelengths, it is necessary to use an optical element having a wider use wavelength. For example, a quarter wavelength plate is required to have a phase difference of 90 ° in the band of 405 to 785 nm. In order to satisfy such a demand, a laminated wave plate in which a half-wave plate and a quarter-wave plate are laminated is generally used (Patent Documents 1 to 3).
By the way, when manufacturing plate-like or polyhedral-like optical elements such as mirrors, wave plates, prisms, etc. by batch processing using a large-area sheet-like glass substrate (wafer), it is possible to collect each individual region at once. Then, it is manufactured by dicing into optical element pieces after completing the required processing. Conventionally, when a laminated optical element as described above is manufactured by a process using a sheet-like wafer, the opposing surfaces of two wafers are bonded together using an adhesive, and then along the boundary of each optical element. It was cut and separated by a dicing blade along the formed cutting line.
However, since the adhesive is applied to the opposite surface including the effective optical region in order to bond the two wafers, an adhesive having a refractive index different from that of the material constituting the wafer is interposed on the effective optical region surface. Thus, there has been a problem that the optical properties inherent to the wave plate and other optical elements are affected.
Further, there is a problem that the wavefront aberration is deteriorated in the optically effective area of the optical element due to the variation in the thickness of the adhesive layer.
Furthermore, since the process of bonding the wafer by an adhesive or heat bonding involves a complicated operation, it has been a cause of reducing productivity.

Next, in recent years, dicing equipment manufacturers have replaced the wafer cutting device using a conventional dicing blade with a laser beam such as an excimer laser along the cutting line of the wafer to divide the wafer into individual pieces. (Patent Documents 4 and 5).
Cutting using a laser beam is advantageous in that the cutting surface can be reduced in burr and chipping (chipping) as compared to cutting with a dicing blade.
However, in this case as well, there is no change in the process other than using a laser beam instead of dicing, so a bonding process between wafers using an adhesive or thermal bonding is still necessary. In addition, the problems caused by the adhesive being interposed between the optical elements have not been improved.
Japanese Patent Laid-Open No. 10-68816 JP 2001-101700 A WO03 / 091768 JP 2005-21940 A JP 2004-111428 A

As described above, conventionally, when mass-producing bonded optical elements having a structure in which different or similar optical elements are laminated and bonded, a large-area wafer serving as a base material of each optical element is bonded with an adhesive. After being used and bonded, dicing was performed along a cutting line formed along the boundary of each optical element piece. For this reason, an adhesive agent intervenes on the joint surface between the laminated optical elements, which adversely affects the optical characteristics. Furthermore, there is a problem that productivity is lowered by the amount of the process of bonding the wafers together. Further, when cutting a wafer bonded by a laser beam, there is a problem in that similar characteristic defects and defects in work processes remain.
The present invention has been made in view of the above, and in order to mass-produce laminated optical elements, a plurality of large-area wafers are laminated and bonded in a state of being cut and separated into individual pieces with a laser beam in a bonded state. In the process of cutting a plurality of wafers held in a temporarily bonded state by temporary bonding that can be performed in the process of cutting along the cutting line between the individual pieces, only the bonding surface peripheral portion (ineffective optical region) of the individual pieces is bonded at the same time. The present invention provides a laminated optical element and a manufacturing method thereof.

In order to solve the above problems, the invention of claim 1 is a laminated optical element in which a plurality of optical elements having the same outer peripheral contour shape are laminated and integrated, and each optical element is arranged on the outer peripheral edge of the opposing surface of each optical element. It is characterized by comprising a welded joint portion on which is welded.
According to a second aspect of the present invention, in the first aspect, an air layer is provided between the opposing surfaces of the optical elements.
According to a third aspect of the present invention, a first wafer in which a plurality of first optical elements are connected in a sheet form, and a plurality of second optical elements having the same outer peripheral contour shape as the first optical element are formed in a sheet form. A temporary bonding step of forming a wafer laminated body by stacking and temporarily bonding the second wafer connected to each other in an aligned state, and each optical element on the first and second wafers constituting the wafer laminated body The first and second optical elements are cut and separated in the laminated state by irradiating a laser beam along a cutting line along the boundary between the first optical element and the second optical element by heat of the laser beam. A cutting and welding process for joining only the outer peripheral edge of the opposing surface of the optical element by welding.
According to a fourth aspect of the present invention, in the third aspect, in the temporary bonding step, both wafers are formed such that an air layer is formed between the first wafer and the second wafer when the wafer stack is formed. Are laminated and temporarily bonded.

According to the present invention, in a laminated optical element in which a plurality of optical elements having the same outer peripheral contour shape are laminated and integrated, the welded joint portion in which each optical element is welded to the outer peripheral edge of the opposing surface of each optical element is provided. Since it is provided, no adhesive is present in the effective optical region, and deterioration of optical characteristics can be prevented.
In addition, according to the method of the present invention, a plurality of large area wafers can be laminated and bonded to each other with a laser beam in order to mass-produce laminated optical elements. In the process of cutting a plurality of wafers held in a temporary bonded state by temporary bonding that does not adversely affect the effective optical area and cut along the cutting line between the individual pieces, the peripheral edge portion of the bonding surface (non- Only the effective optical area) can be glued.

Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings.
1A and 1B are a perspective view and a cross-sectional view taken along line AA, showing a configuration of a laminated optical element according to an embodiment of the present invention.
The laminated optical element 1 is, for example, a wave plate, and includes a first wave plate (1/2 wave plate) 2 as a first optical element having the same outer peripheral contour shape, and a first wave element as a second optical element. A structure in which a two-wave plate (quarter-wave plate) 3 is joined and integrated is provided.
As shown in FIG. 1B, the laminated optical element 1 is configured so that the opposing surfaces 2a and 3a of the first wave plate 2 and the second wave plate 3 are in close contact with each other. Only the outer peripheral edge portion (welding joint portion) 4 is joined by welding over the entire circumference.
In FIG. 1C, the first wave plate 2 and the second wave plate 3 are arranged to face each other through a gap made of an air layer S between the respective facing surfaces, and only the outer peripheral edge 4 is extended over the entire circumference. The structure joined by welding is provided. Even if the air layer S exists without the bonding surfaces of the first and second wave plates 2 and 3 being in close contact with each other, the refractive index of air does not affect the characteristics of the laminated optical element.
In addition to the laminated wave plate in which two wave plates are joined, the laminated optical element 1 is sandwiched between a laminated optical element in which a wave plate and a diffraction grating (grating) are joined, a resin film wave plate and a glass substrate. Laminated optical element (Japanese Patent No. 3458895) Two or more optical elements of the same kind or different kinds, such as an optical low-pass filter (Japanese Patent Laid-Open No. 2004-70340) in which a quarter-wave plate is disposed between two birefringent plates Widely includes laminated ones.

Next, FIGS. 2A to 2D are views showing a manufacturing process in the case where the laminated wave plate as the laminated optical element 1 shown in FIG. 1 is mass-produced using two sheet-like wafers.
FIG. 2A shows a first wafer 11 in which a plurality of first wave plates 2 as first optical elements are connected in a sheet form, and a second optical having the same outer peripheral contour shape as the first wave plate 2. A second wafer 12 in which a plurality of second wave plates 3 as elements are connected in a sheet form is shown. Each of the wafers 11 and 12 is manufactured by performing a necessary process (polishing or the like) at once on a large-area sheet-like glass substrate or an individual piece region on a quartz substrate.
The shape and arrangement of the individual first wave plates 2 constituting the first wafer 11 and the shape and arrangement of the individual second wave plates 3 constituting the second wafer 12 are configured in advance so as to coincide with each other. . That is, the layout of the cutting lines (boundary lines) C between the individual pieces formed on both the wafers 11 and 12 is also formed to match (align). In the case of a wafer cut by a conventional dicing blade, the width dimension of the cutting line C is set to a predetermined value in consideration of the thickness of the blade, but in this embodiment, an individual piece using a laser beam L Therefore, the width dimension of the cutting line C is set to be larger than the spot diameter of the laser beam by a predetermined width.
FIG. 2B shows a temporary bonding step of forming the wafer laminate 13 by stacking the first and second wafers 11 and 12 in alignment and temporarily bonding them. Temporary bonding is performed by bonding edge portions along the outer peripheral edge of the wafer outside the effective optical region with an adhesive. Here, the alignment state means a state in which the cutting lines C on the wafers 11 and 12 are matched.
At this time, it is ideal that the opposing surfaces of the two wafers are in close contact with each other, but the air layer S may be interposed without the two being in close contact.

  2C and 2D show a process of joining the first and second wave plates at the same time as cutting and separating the wafer laminate 13 along the cutting line C with a laser beam. The spot diameter when the laser beam L is irradiated onto the wafer surface is smaller than the width w of the cutting line C, and the orbit of the laser beam emitted from a laser device (not shown) is the center line of the width dimension w of the cutting line C. Control the device to move along. For this reason, the portion along the center line is cut into a linear shape by the ablation (evaporation) effect, and at the same time, only the outer peripheral edge portion (welded joint portion) 4 of the opposed surfaces of the wave plates 2 and 3 in the laminated state It can be set as the state joined by welding over. That is, since the spot diameter of the laser beam is sufficiently smaller than the width w of the cutting line C, the laser beam moves along the center line of the width dimension of the cutting line C by setting the power of the laser beam to a predetermined value. At this time, since the wafer material along the center line of the width dimension of the cutting line C is completely evaporated, a dividing line is formed along the center line. It remains in the molten state. In other words, during the irradiation of the laser beam L, the outer peripheral surfaces of the first wave plate 2 and the second wave plate 3 are in a state where the constituent materials are melted. Only the joint part) 4 can be welded over the entire circumference, and can be shifted to the joined state by cooling.

As described above, in the present invention, only the outer peripheral surface of the optical element is welded by using a laser beam cutting and welding method without using an adhesive, and the outer peripheral edges of the opposing surfaces of the wave plates 2 and 3 are joined. Thus, the cut and separated laminated optical element 1 is in a state where no adhesive is present on the optically effective area, and optical characteristics such as wavefront aberration are not deteriorated. Even in the case where the air layer S exists without the bonding surfaces of the first and second wave plates 2 and 3 being in close contact with each other, the refractive index of air does not significantly affect the characteristics of the laminated optical element. However, in order to prevent irregular reflection of light on the facing surfaces of the wave plates 2 and 3, an AR coat (antireflection film) may be formed on both facing surfaces to increase the transparency.
In addition, no special bonding process using an adhesive or a thermal bonding method is required, and the bonding process is performed simultaneously with the cutting process using a laser beam, so that the lead time can be shortened.
The manufacturing method of the present invention can be widely applied to optical components other than those described above.

(A) thru | or (c) is a perspective view which shows the structure of the laminated optical element which concerns on one Embodiment of this invention, and AA sectional drawing. (A) thru | or (d) is a figure which shows the manufacturing process in the case of mass-producing the laminated wavelength plate as a laminated optical element shown in FIG. 1 using two sheet-like wafers.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Laminated optical element, 2, 3 ... Wave plate (optical element), 2a, 3a ... Opposite surface, 4 ... Outer peripheral edge part, 11, 12 ... Wafer, 13 ... Wafer laminated body, 15 ... Material.

Claims (4)

In a laminated optical element in which a plurality of optical elements having the same outer peripheral contour shape are laminated and integrated,
A laminated optical element comprising a welded joint in which each optical element is welded to the outer peripheral edge of the opposing surface of each optical element.   The laminated optical element according to claim 1, further comprising an air layer between opposing surfaces of the optical elements. A first wafer in which a plurality of first optical elements are connected in a sheet shape, and a second wafer in which a plurality of second optical elements having the same outer peripheral contour shape as the first optical elements are connected in a sheet shape And a temporary adhesion step of forming a wafer laminate by laminating and temporarily adhering in an aligned state,
The first and second optical elements are cut in a laminated state by irradiating a laser beam along a cutting line along the boundary between the optical elements on the first and second wafers constituting the wafer laminate. At the same time as the separation, a cutting and welding step in which the outer peripheral edges of the opposing surfaces of the first optical element and the second optical element are joined by welding with the heat of the laser beam;
A method for producing a laminated optical element, comprising:   In the temporary bonding step, both wafers are stacked and temporarily bonded so that an air layer is formed between the first wafer and the second wafer when the wafer stack is formed. Item 4. A method for producing a laminated optical element according to Item 3.

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