JP4421249B2 - Method for manufacturing polarization separating element - Google Patents

Description

The present invention relates to the production how the polarization separating element.

As a method for separating two orthogonal polarization components, in Patent Document 1, an organic birefringent film having a different refractive index is adhered to a transparent substrate on a vibrating surface having different incident light, and a period is formed on the surface of the organic birefringent film. A polarization separation element in which a general unevenness (diffraction grating) is formed has been proposed. In Patent Document 1, an organic birefringent film is bonded to a transparent substrate, and then a periodic resist mask is formed on the surface of the organic birefringent film by photolithography, and if necessary, inverted to a metal mask by lift-off. Then, a process for forming a diffraction grating by dry etching is disclosed.

  Patent Documents 2 and 3 disclose a method for producing a bonded optical disk by curing an ultraviolet curable adhesive by irradiating ultraviolet rays during rotation.

JP 2000-75130 A JP 10-334521 A JP 2000-268416 A

  In an optical pickup for an optical disk, a polarization separation element is used to separate incident light from a light source and reflected light (information signal) from the optical disk and efficiently guide the reflected light (information signal) to a light receiving element. Yes. Conventionally, a combination of a beam splitter with a prism attached and a λ / 4 wavelength plate was used. However, in order to meet the demands for miniaturization and cost reduction of the pickup, a thin polarization separation element can be realized instead of the beam splitter. Birefringent diffraction grating type polarization separation elements are being developed.

  As a method of separating two orthogonal polarization components, in Patent Document 1, an organic birefringent film having a different refractive index is bonded to a transparent substrate on a vibrating surface having different incident light, and the organic birefringent film surface is periodically formed. There has been proposed a polarization separation element in which a simple concavo-convex grating (diffraction grating) is formed. The organic birefringent film is made of a stretched organic polymer material.

  In this polarization separation element, when the organic birefringent film is bonded to the transparent substrate using an adhesive, the thickness of the adhesive layer needs to be uniform in order to make the optical path constant in the diffraction grating plane. Further, when bubbles enter the adhesive layer, light (incident light, outgoing light) is scattered by the bubbles and the diffraction efficiency is lowered. Therefore, an adhesion method that does not entrap the bubbles is required.

  From the above points, the spinner method used in the bonded optical disk is suitable for the method of adhering the organic birefringent film to the transparent substrate.

  A method for manufacturing a bonded optical disk by the spinner method will be described below with reference to FIG. In this manufacturing method, the process proceeds in the order of the following (a) to (e).

  (A) First, the hub 502 of the first substrate 501 is inserted into the center pin 504 of the spin table 503, and the ultraviolet curable adhesive 505 is dropped on the first substrate 501 while the spin table 503 is rotated.

  (B) When the adhesive 505 spreads to the periphery of the first substrate 501, the rotation of the spin table 503 is stopped.

  (C) The hub 507 of the second substrate 506 is inserted into the center pin 504 of the spin table 503, and the first substrate 501 and the second substrate 506 are brought into contact with each other.

  (D) Rotate the spin table 503, shake off excess adhesive, and make the adhesive layer thickness constant.

  (E) The rotation of the spin table 503 is stopped, the ultraviolet ray is irradiated to cure the adhesive layer, and the bonded optical disk is completed.

  In the bonded optical disk, a polycarbonate substrate or PMMA substrate having a thickness of about 0.6 mm is bonded. This can be handled as a rigid body because the substrate is relatively thick. Therefore, when the second substrate 506 is placed on the first substrate 501, the flatness of the second substrate 506 is good even after being placed on the first substrate 501, and the second and first substrates 506 and 501 are attached to each other. When rotated at high speed, the surface of the optical disk can be completely flattened.

  However, in the production of the polarization separation element, since the size of the polarization separation element is about several millimeters square, several tens to several hundreds of pieces are formed on the organic birefringent film bonded to the transparent substrate having a diameter of 4 to 8 inches. A diffraction grating is formed in an array, and then individual polarization separation elements are taken out by dicing. In order to increase the number of polarization separation elements that can be taken from one substrate, the organic birefringent film 603 and the transparent substrate are not provided with the hubs 502 and 507.

  Therefore, as shown in FIG. 15, the transparent substrate 601 is vacuum-adsorbed on the spin table 503, and then an ultraviolet curable adhesive 602 is dropped on the center of the transparent substrate 601, and the spin table 503 is rotated to apply the adhesive 602. After spreading over the entire surface of the transparent substrate 601, the organic birefringent film 603 is placed on the transparent substrate 601. However, since the organic birefringent film 603 does not have a hub, it cannot be fixed with the center pin 504, and the transparent substrate is free. 601. Generally, the organic birefringent film 603 is placed on the transparent substrate 601 coated with the adhesive 602 by using a mounting device, and the center of the organic birefringent film 603 is accurately aligned with the rotation center of the spin table 503. Is often difficult in terms of mechanical accuracy of the mounting device. Therefore, when the organic birefringent film 603 is not placed on the rotation center of the spin table 503, when the spin table 503 is rotated as described above (FIG. 15A), the organic birefringent film 603 is displaced. A problem occurs (FIG. 15B). When this positional deviation is large, the organic birefringent film 603 protrudes from the transparent substrate 601.

  Then, after curing the adhesive 602 by ultraviolet irradiation, lithography and dry etching are performed in order to form a diffraction grating. In many cases, the side of the substrate 601 is clamped in the apparatus or between processes. If the organic birefringent film 603 protrudes from the transparent substrate 601, it becomes difficult to carry and a diffraction grating cannot be formed.

  Therefore, when the position of the organic birefringent film 603 is shifted during the rotation of the spin table 503, the rotation of the spin table 503 is stopped, and the organic birefringent film 603 is returned to an appropriate position. It was necessary to rotate 503, and the throughput of the bonding process was slowed by repeating the above operation. Further, due to the above work, the rotation time of the spin table 503 cannot be made constant, and there is a problem that the thickness of the adhesive layer is not uniform between the substrates 601.

  In order not to cause the displacement of the organic birefringent film 603 during the rotation of the spin table 503, a method of irradiating ultraviolet rays during the rotation can be considered. For example, as a method for manufacturing a bonded optical disk, Patent Documents 2 and 3 propose a method of curing the ultraviolet curable adhesive 505 by irradiating ultraviolet rays during rotation.

  However, in the production of the polarization separating element, since it is necessary to irradiate ultraviolet rays after rotating the substrate 601 to some extent in order to make the adhesive layer thickness uniform, it is possible to completely prevent the misalignment of the organic birefringent film 603. Was difficult.

  In addition, the image recognition function is mounted on the mounting device, the rotation center of the spin table 503 and the center of the organic birefringence film 603 are detected, and the organic birefringence is applied to the rotation center of the spin table 503 while feedback control is performed on the mounting device. In the case where means for placing the center of the film 603 is used, the alignment accuracy between the rotation center of the spin table 503 and the center of the organic birefringence film 603 can be remarkably improved, so that the organic birefringence during the rotation of the spin table 503 is achieved. Misalignment of the film 603 hardly occurs.

  However, it is necessary to provide a detection device using a CCD or the like and a feedback control system in the mounting device, which increases the cost of the mounting device. In addition, since position detection and feedback control are performed at the time of bonding, the throughput of the bonding process is reduced. Therefore, it is difficult to produce a polarization separation element at low cost.

  Further, since the organic birefringent film 603 has different refractive indexes in two in-plane directions, it is necessary to form a diffraction grating in one specific direction out of the two in-plane directions. Therefore, in the lithography process, a resist pattern must be formed in alignment with one specific direction (referred to as the “exposure reference axis” of the organic birefringent film 603) out of two directions having different refractive indexes within the plane of the organic birefringent film 603. Don't be. Therefore, a mark (usually using an orientation flat) serving as an index of the exposure reference axis is provided on the organic birefringent film 603, and a resist pattern is formed using the mark on the organic birefringent film 603 as a reference position.

  Although a reduction projection exposure apparatus is used for exposure, the reduction projection exposure apparatus normally detects the orientation flat of the substrate 601 and performs the first exposure (exposure without alignment with the lower layer) using the orientation flat as a reference position. Therefore, in order to perform the first exposure with the mark of the organic birefringent film 603 inside the transparent substrate 601 as the reference position, another mechanism is required, which leads to an increase in the cost of the apparatus.

  Therefore, as shown in FIG. 15, an orientation flat 611 is also provided on the transparent substrate 601, and the relative position of the orientation flat of the transparent substrate 601 and the mark of the organic birefringent film 603 is within an allowable range in the bonding process of the organic birefringent film 603. (When the orientation flat 612 is provided on the organic birefringent film 603, the transparent substrate 601 and the orientation flat 612 of the organic birefringent film 603 are parallel to each other). In the exposure process, the orientation flat 612 of the transparent substrate 601 is First exposure is performed at the reference position.

  Even when the organic birefringent film 603 can be suppressed to such an extent that the organic birefringent film 603 does not protrude from the transparent substrate 601 in the bonding process of the organic birefringent film 603, the slight misalignment of the organic birefringent film 603 is not. The relative position between the mark of the organic birefringent film 603 and the orientation flat 612 of the transparent substrate 601 is shifted to increase the ratio exceeding the allowable range. As a result, since the orientation flat 611 of the transparent substrate 601 is used as the reference position in the exposure process, the ratio that the resist pattern direction does not coincide with the exposure reference axis of the organic birefringent film 603 increases and polarization separation having desired optical characteristics is achieved. There is a problem that the yield at which the element is obtained is lowered.

In Patent Document 1 , an organic birefringent film is bonded to a transparent substrate, and then a periodic resist mask is formed on the surface of the organic birefringent film by photolithography, and if necessary, inverted to a metal mask by lift-off. Then, a process for forming a diffraction grating by dry etching is disclosed. In addition, a periodic resist mask is formed on the surface of the organic birefringent film by photolithography, then a diffraction grating is formed by dry etching, and then the process of adhering the organic birefringent film having the diffraction grating formed on a transparent substrate is performed. Disclosure.

However, when the bonding method employed in the bonded optical disk is used in the process disclosed in Patent Document 1 , the following problems occur.

  That is, the items affected by the unevenness of the surface of the organic birefringent film 603 after bonding are the one shot area in the exposure process for producing the mask pattern for forming the diffraction grating, and the wavefront of the polarization separating element. Aberration.

  When the organic birefringent film is bonded by the method used for the bonded optical disk, it has been found that the unevenness of the organic birefringent film is small in the range of several mm square, but a long span like swell occurs. . A conceptual diagram of the unevenness of the organic birefringent film after bonding is shown in FIG.

  Here, when the size of one polarization separation element is 5 mm square and the exposure uses a Nikon NSR2205i12D as a reduction projection exposure apparatus, the unevenness of the organic birefringent film allowed from the wavefront aberration of the polarization separation element is 1 It has been confirmed by experiments that the depth of focus is 2.9 μm at NA = 0.50.

  From the above data, in order to reduce the wavefront aberration of the polarization separation element, it is necessary to suppress the unevenness to 1.0 μm or less at least 5 mm square. The unevenness defined by the wavefront aberration is assumed to be unevenness (A).

  Further, the above-described NSR2205i12D has a maximum exposure area of 22 mm square, and the focal depth of lithography is 2.5 μm. Therefore, if the unevenness is 2.5 mm or less, it can be exposed with one shot. Here, the unevenness defined by the depth of focus is assumed to be unevenness (B).

  In the process of forming a diffraction grating after adhering an organic birefringent film to a transparent substrate, the unevenness of the organic birefringent film is small in the range of several mm square, so the unevenness (A) specified by wavefront aberration is less than 5 mm square, and the fabrication is Almost all polarized light separating elements are suppressed to wavefront aberrations that are not problematic in practice.

  On the other hand, when looking at the exposure area of one shot, the long-span irregularities such as waviness exceed the irregularities (B) defined by the focal depth, so the exposure area of one shot cannot be set to 22 mm square. It was necessary to reduce the exposure area. In the case of exposing a pattern with a 2.0 μm pitch and duty = 50%, the exposure area is limited to 10 mm square, reducing the lithography throughput.

  Further, when trying to expose a finer pattern in the exposure process, the depth of focus of lithography decreases, and the unevenness (B) defined by the focal depth may be larger than the unevenness (A) defined by the wavefront aberration. . In that case, even if the exposure area of one shot is set to 1 chip angle, there is a problem that the manufacturing yield of the polarization separation element is significantly lowered in the process of forming the diffraction grating after the organic birefringent film 603 is bonded to the transparent substrate.

  Next, the problem of the process of adhering to a transparent substrate after forming a diffraction grating on the organic birefringent film will be described.

  An apparatus for performing lithography on a film-shaped member is used in a plastic LCD. By using such an apparatus, a resist pattern can be formed on an organic birefringent film. However, an apparatus for dry etching a film-shaped member is not commercially available, and it is practically impossible to process an organic birefringent film without being fixed to a transparent substrate.

  Further, even when a dry etching apparatus that can process a film-shaped member is newly developed, there are the following concerns.

  That is, since the optical disk is 0.6 mm thick, it is stored in the cassette rack, the suction arm is inserted into the cassette rack, and the surface facing the recording layer is held by the suction arm, so that the recording layer is not damaged. We are handling.

  However, since the thickness of the organic birefringent film that can be obtained in the polarization separation element is about 50 to 100 μm, it cannot be stored in a cassette rack, and a diffraction grating is formed by placing it horizontally one by one. It is necessary to hold the surface. Therefore, there is a concern that the diffraction grating is scratched by handling during bonding, and the wavefront aberration of the polarization separation element is reduced.

  Although it is conceivable to devise the mechanism of the suction arm and hold only the surface opposite to the surface on which the diffraction grating is formed, the mechanism of the suction arm becomes complicated.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide an optimum technique for manufacturing a polarization separation element.

The invention according to claim 1 is a mask pattern forming step of forming a periodic mask pattern that transmits ultraviolet light on one surface of an organic birefringent film having a different refractive index with respect to different vibration surfaces of incident light, An adhesion step of bonding the organic birefringent film to a transparent substrate on a surface opposite to the surface on which the mask pattern of the organic birefringent film is formed; and etching the surface of the organic birefringent film using the mask pattern. In the method for manufacturing a polarization separation element including a diffraction grating forming step of forming a diffraction grating by periodic unevenness, in the bonding step, the transparent substrate is given a first rotation that is a rotation in the substrate surface direction, and An ultraviolet curable adhesive is applied to the entire surface of the transparent substrate, and then the organic birefringent film is placed on the surface opposite to the surface on which the mask pattern is formed on the ultraviolet curable adhesive. A second rotation which is a rotation in the substrate surface direction is applied to the bright substrate to flatten the surface of the organic birefringent film, the ultraviolet curable adhesive is dissolved during the second rotation, and the organic birefringence is obtained. An organic solvent that does not dissolve the film is dropped to remove the UV curable adhesive at the periphery of the transparent substrate, and then the UV curable adhesive is cured by irradiating the transparent substrate with a first ultraviolet ray. Do.

According to a second aspect of the present invention, in the method of manufacturing a polarization separation element according to the first aspect, in the mask pattern forming step, the mask pattern is formed of SiO ₂ , Si ₃ N ₄ , SiON, In ₂ O ₃ , It is made of at least one material selected from the group consisting of ITO (Indium thin Oxide) materials.

According to a third aspect of the present invention, in the method of manufacturing a polarization separation element according to the first or second aspect , in the bonding step, at least one of isopropyl alcohol and acetone is used as the organic solvent.

In the first aspect of the present invention, since the ultraviolet curable adhesive is applied to the entire surface of the transparent substrate by applying the first rotation, a region without the adhesive does not occur on the transparent substrate and the periodic mask is used. Since the pattern transmits ultraviolet rays, the entire surface of the organic birefringent film formed with the transparent substrate and the mask pattern can be realized by irradiating the first ultraviolet rays.

  Further, the flatness of the surface of the bonded organic birefringent film may have long-span irregularities such as undulations as in the conventional example, but the irregularities in the range of about several mm square can be reduced. It is this unevenness in the range of several mm square that affects the wavefront aberration of the polarized light separating element, and the flatness of several mm square is good on the bonded organic birefringent film. The wavefront aberration can be suppressed to a level that causes no problem in practice.

Furthermore, since the mask pattern has already been formed on the surface of the organic birefringent film before bonding, long-span irregularities such as waviness after bonding cause the exposure area and resolution of one shot in the exposure to form the mask pattern. Does not affect.
In addition, the exposure area and resolution of one shot are determined by the flatness of the organic birefringent film in the exposure for forming the mask pattern. In the exposure for forming the mask pattern, when the organic birefringent film is flattened by applying tension to the organic birefringent film, the unevenness at the time of exposure can be made smaller than in the conventional case. As a result, the exposure area of one shot can be increased as compared with the conventional case, and the throughput during exposure can be improved. Since the resolution is improved, a finer diffraction grating can be formed.

  During the second rotation, the UV curable adhesive is dissolved around the transparent substrate that is not covered with the organic birefringent film because the organic solvent that dissolves the UV curable adhesive and does not dissolve the organic birefringent film is dropped. Is done. As a result, even if the peripheral portion of the substrate is handled between the apparatuses or in the apparatus, the generation of foreign matter from the peripheral portion of the substrate is very small, so that the manufacturing yield of the polarization separating element can be improved.

  Since the organic solvent is dropped while rotating the transparent substrate, a centrifugal force is applied to the organic solvent, and it is difficult to penetrate the ultraviolet curable adhesive in the region sandwiched between the organic birefringent film and the transparent substrate. By irradiating the first ultraviolet ray, a sufficient adhesion area can be obtained between the transparent substrate and the organic birefringent film.

  Further, in view of the planarity of the surface of the bonded organic birefringent film, long-span irregularities such as undulations remain as in the second and third aspects, but the irregularities in the range of several mm square are reduced. As a result, the wavefront aberration of each polarization separation element can be suppressed to a level that causes no problem in practice.

  Further, when exposure is performed to form a mask pattern, if the organic birefringent film is flattened by applying tension to the organic birefringent film, the exposure area of one shot can be increased as compared with the conventional case. In addition, a finer diffraction grating can be formed.

  In addition, an ultraviolet curable adhesive around the transparent substrate that is not coated with the organic birefringent film is added so that the organic solvent that does not dissolve the organic birefringent film is dropped during the second rotation. Is removed.

  Since the organic solvent is dropped while rotating the transparent substrate, a centrifugal force is applied to the organic solvent, and it is difficult to penetrate the ultraviolet curable adhesive in the region sandwiched between the organic birefringent film and the transparent substrate. By irradiating the first and second ultraviolet rays, a sufficient adhesion area can be obtained between the transparent substrate and the organic birefringent film.

  Since the ultraviolet curable adhesive is semi-cured by performing the first ultraviolet irradiation during the second rotation, the adhesive force between the ultraviolet curable adhesive and the organic birefringent film is increased, and the organic caused by the second rotation Misalignment of the birefringent film can be reduced. As a result, the frequency with which the organic birefringent film protrudes from the transparent substrate is reduced, so that conveyance failure can be reduced, and a polarization separation element can be manufactured at a lower cost.

  If the mask pattern is formed in parallel to one of the two directions in the plane of the organic birefringent film before bonding, the organic birefringent film slightly moves during the second rotation, and the organic birefringence is formed on the transparent substrate. Even when the film rotates, since the organic birefringent film is etched using the mask pattern, the direction of the diffraction grating can be aligned with one of the two directions in the plane of the organic birefringent film. A predetermined diffraction efficiency is obtained.

  Further, in view of the planarity of the surface of the bonded organic birefringent film, long-span irregularities such as waviness remain as in the case of claims 2 to 4, but the irregularities in the range of several mm square are reduced. As a result, the wavefront aberration of each polarization separation element can be suppressed to a level that causes no problem in practice.

  Further, when exposure is performed to form a mask pattern, if the organic birefringent film is flattened by applying tension to the organic birefringent film, the exposure area of one shot can be increased as compared with the conventional case. In addition, a finer diffraction grating can be formed.

  In addition, an ultraviolet curable adhesive around the transparent substrate that is not coated with the organic birefringent film is added to drop the organic solvent that dissolves the ultraviolet curable adhesive and does not dissolve the organic birefringent film during the third rotation. Is removed.

  Since the organic solvent is dropped while rotating the transparent substrate, a centrifugal force is applied to the organic solvent, and it is difficult to penetrate the ultraviolet curable adhesive in the region sandwiched between the organic birefringent film and the transparent substrate. By irradiating the first and second ultraviolet rays, a sufficient adhesion area can be obtained between the transparent substrate and the organic birefringent film.

  Further, after stopping the second rotation, sliding the organic birefringent film on the transparent substrate, correcting the position, and confirming that the relative position between the transparent substrate and the organic birefringent film is within the allowable value, Since the ultraviolet curable adhesive is semi-cured by performing the ultraviolet irradiation of No. 1, the relative position of the transparent substrate and the organic birefringent film can be kept within an allowable value, and the adhesion force between the organic birefringent film and the transparent substrate can be strengthened. As a result, the displacement of the organic birefringent film is less likely to occur during the third rotation, and the frequency at which the organic birefringent film protrudes from the transparent substrate can be further reduced.

  When the mask pattern is formed in parallel with one of the two directions in the plane of the organic birefringent film before bonding, the organic birefringent film slightly moves during the third rotation, Even when the organic birefringent film is rotated, the organic birefringent film is etched using the mask pattern, so that the direction of the diffraction grating is aligned with one of the two directions in the plane of the organic birefringent film. And a predetermined diffraction efficiency is obtained.

According to the second aspect of the present invention, SiO ₂ , Si ₃ N ₄ , SiON, In ₂ O ₃ , and ITO can be removed with an etching solution containing an acid as a main component. Specifically, SiO ₂ , Si ₃ N ₄ , and SiON can be removed with a hydrofluoric acid etching solution, and In ₂ O ₃ and ITO can be removed with a ferric chloride and hydrochloric acid etching solution. Therefore, since the wet etching has a large selection ratio between the periodic mask pattern that transmits ultraviolet light, which is the object to be etched, and the organic birefringent film, the etching pattern of the organic birefringent film is not deteriorated in the mask pattern removal process, which is good A simple diffraction grating shape.

Also, since SiO ₂ , Si ₃ N ₄ , SiON, In ₂ O ₃ , and ITO are unnecessary in most organic solvents, the UV curable adhesive is dissolved during the second and third rotations, and organic Even if an organic solvent that does not dissolve the birefringent film is dropped, the shape of the mask pattern does not deteriorate.
According to the third aspect of the present invention, the acrylic or epoxy UV curable adhesive widely used in the bonding process for bonded optical disks and the like is very well soluble in isopropyl alcohol and acetone. When alcohol or acetone is used, it is possible to improve the working environment and the safety of the apparatus as compared with other organic solvents that are highly harmful.

  A plurality of examples of the best mode for carrying out the invention will be described.

[Polarization Separation Device Manufacturing Method 1]
1 and 2 are explanatory views showing steps (a) to (n) of the method for manufacturing a polarization beam splitting element according to the first embodiment. The steps of this manufacturing method proceed in the order of (a) to (n).

  (A) First, tensile tensions (indicated by arrows) are applied to the four corners of an organic birefringent film 101 having a thickness of 80 μm cut into 120 mm square, and the organic birefringent film 101 is flattened. Thereafter, a positive resist 102 (for example, PFi-34 manufactured by Sumitomo Chemical Co., Ltd.) is applied to the surface of the organic birefringent film 101 by a spray method or a roll coat method while applying a tensile tension to the organic birefringent film 101, and is heated to 60 ° C. Pre-bake

  (B) A periodic pattern (pitch: 2.0 μm, duty = 50) on the reticle 103 using a reduction projection exposure apparatus (for example, NSR2205i12D manufactured by Nikon Corporation) with a tension applied to the organic birefringent film 101. %) Is exposed parallel to the slow axis of the organic birefringent film 101. The exposure is performed with NA = 0.50, and one shot is 15 mm square.

  In the polarization separation element 1, the diffraction grating 112 needs to be aligned in one specific direction out of the two directions in the plane of the organic birefringent film 101. In this example, the direction of the diffraction grating 112 can be aligned with the direction parallel to the slow axis by exposing the periodic pattern parallel to the slow axis.

  (C) Dip development is performed using a developer (for example, 2.38% solution of NMD-3 manufactured by Tokyo Ohka Kogyo Co., Ltd.) to complete a periodic resist pattern 104 on the surface of the organic birefringent film 101.

  (D) An ultraviolet curable adhesive 109 (described later) used for bonding the organic birefringent film 101 and a transparent substrate 105 (described later) onto the periodic resist pattern 104 while applying a tensile tension to the organic birefringent film 101. A film 106 that transmits ultraviolet light for curing is formed to a thickness of 50 to 100 nm by sputtering or vacuum deposition. In this example, an ITO (Indium thin Oxide) film of 60 nm is formed as the film 106 that transmits ultraviolet rays by an EB vapor deposition method. After the film 106 (ITO) that transmits ultraviolet rays is formed, the tension of the organic birefringent film 101 is released.

  (E) The organic birefringent film 101 is immersed in an acetone bath, lifted off by applying ultrasonic vibration for 10 minutes, and a periodic mask pattern (ITO pattern) 107 that transmits ultraviolet rays from the periodic resist pattern 104 is formed. Form. Thereafter, the organic birefringent film 101 is cut into φ90 mm.

  (F) Then, a transparent substrate 105 (for example, optical glass (for example, BK7 of Schott)) having a diameter of 100 mm and a thickness of 1.0 mm is placed on the spin table 111 and fixed to the spin table 111 by vacuum suction. Thereafter, the spin table 111 is rotated at 10 to 50 rpm, and the transparent substrate 105 is rotated in the direction of the substrate surface, and an acrylic ultraviolet curable adhesive having a refractive index of 1.52 is used at the center of the transparent substrate 105 using the dispenser 108. 3-10 g of 109 is dropped. Thereafter, the spin table 111 is rotated at 150 to 500 rpm (first rotation), the ultraviolet curable adhesive 109 is spread over the entire surface of the transparent substrate 105 (FIG. 1G), and the rotation of the spin table 111 is stopped.

  (H) A surface on which the mask pattern (ITO pattern) is formed on the ultraviolet curable adhesive 109 using a mounting device while the center of the organic birefringent film 101 is substantially aligned with the rotation center of the spin table 111. The organic birefringent film 101 is placed on the opposite surface.

  (I) By rotating the spin table 111 at 1000 to 3000 rpm, the transparent substrate 105 is rotated in the direction of the substrate surface (second rotation), the UV curable adhesive 109 is shaken off, and the thickness of the adhesive layer is changed to the substrate. The surface of the organic birefringent film 101 is flattened in the plane of 105.

  (J) During the second rotation, isopropyl alcohol is dropped on the organic birefringent film 101. Isopropyl alcohol is an organic solvent that dissolves the acrylic ultraviolet curable adhesive 109 used in this example and does not dissolve the organic birefringent film 101. After the step (j), the ultraviolet curable adhesive 109 remaining around the transparent substrate 105 is removed with isopropyl alcohol.

  (K) The rotation of the spin table 111 is stopped, and ultraviolet rays (first ultraviolet rays) are irradiated from the organic birefringent film 101 side using a high pressure mercury lamp to cure the ultraviolet curable adhesive 109.

  (L) Then, the transparent substrate 105 to which the organic birefringent film 101 is bonded is removed from the spin table 111, and the mask pattern 107 that transmits the ultraviolet rays in an etching gas atmosphere containing oxygen gas as a main component using an NLD etching apparatus. Using the (ITO pattern) as a mask, the organic birefringent film 101 is etched by a depth of 3 μm.

  Then, the mask pattern (ITO pattern) 107 is removed using an ITO etching solution using hydrochloric acid and ferric chloride, and a diffraction grating 112 in which periodic irregularities are formed by the organic birefringent film 101 after etching is completed. Let

(M) Thereafter, a flat plate-processed substrate having a diffraction grating 112 formed thereon is placed on a stainless steel table (not shown) having a diameter of 200 mm and a thickness of 50 mm, and optically isotropic acrylic ultraviolet curing is performed on the surface of the diffraction grating 112. 1.0 mL of mold adhesive (isotropic adhesive) 113 is dropped with a micro syringe. Then, a counter transparent substrate 114 having a diameter of 100 mm and a thickness of 1 mm having both surfaces optically polished (for example, using an optical glass BK7 manufactured by SCHOTT) is mounted, and optical glass having been optically polished is mounted on the counter transparent substrate 114. A pressure of 100 gf / cm ² is applied to spread the isotropic adhesive 113 over the entire surface to be bonded. Note that an antireflection film (not shown) is formed on the surface of the counter transparent substrate 114 facing the surface to be bonded so as to minimize the reflection of incident light. In this state, the isotropic adhesive 113 is cured by irradiating ultraviolet rays through the counter transparent substrate 114.

  (N) The product 116 created by the above steps is cut into a 5 mm square using a dicing saw 115 to complete a plurality of polarization separation elements 1.

  In the polarization separation element 1 manufactured in this way, an organic birefringent film 101 having a different refractive index is bonded to a transparent substrate 105 with respect to different vibration surfaces of incident light with an ultraviolet curable adhesive 109, thereby organic birefringence. The diffraction grating 112 is formed by forming periodic irregularities on the surface of the film 101.

  The completed polarization separation element 1 is irradiated with S-polarized light having a wavelength of 680 nm, and the first-order diffraction efficiency is measured by receiving the first-order diffracted light with the light-receiving element. As a result, the polarization separation element 1 in which the diffraction grating 112 is well formed generally achieves a diffraction efficiency of 32% or more.

  According to the method for manufacturing the polarization separating element 1 described above, the ultraviolet curable adhesive 109 is applied to the entire surface of the transparent substrate 105 by the first rotation, and therefore, no region without the adhesive is generated on the transparent substrate 105. . Therefore, when the organic birefringent film 101 is placed on the surface opposite to the surface on which the periodic mask pattern that transmits ultraviolet rays is formed on the transparent substrate 105 to which the adhesive is applied, the organic birefringent film 101 covers the entire surface. To contact the surface of the transparent substrate 105 through an adhesive.

  Further, since the periodic mask pattern 107 is formed of a film 106 that transmits ultraviolet rays, not only the region between the periodic mask patterns 107 but also immediately below the periodic mask pattern 107 by the first ultraviolet irradiation. The UV curable adhesive 109 is also cured and can be adhered to the entire surface.

  The film 106 that transmits ultraviolet rays does not need to have 100% transmission of ultraviolet rays, and if there is some absorption, there is no problem if the irradiation energy of ultraviolet rays is increased. Practically, 30 to 99% of ultraviolet rays having a wavelength suitable for curing the ultraviolet curable adhesive 109 may be transmitted.

  This is an effect that can be realized only when the mask pattern 107 formed on the surface of the organic birefringent film 101 is made of a material that transmits ultraviolet rays, and an etching mask such as a resist or metal absorbs or shields ultraviolet rays, and is periodic. The ultraviolet curable adhesive 109 immediately below the mask pattern 107 is not cured, and the adhesive force between the organic birefringent film 101 and the transparent substrate 105 cannot be increased. As a result, the organic birefringent film 101 is likely to be peeled off in the dicing process described above.

  Further, according to the method of manufacturing the polarization separation element 1, the periodic mask pattern 107 that transmits ultraviolet rays is formed in the region that becomes the convex portion of the diffraction grating 112 by dry etching, so that the diffraction grating 112 The protrusions are not easily scratched during handling during bonding.

  On the other hand, a region that becomes a concave portion of the diffraction grating 112 by dry etching is scratched because there is no periodic mask pattern that transmits ultraviolet rays, but is removed by subsequent dry etching of the organic birefringent film 101. Therefore, wavefront aberration can be suppressed as compared with the conventional example in which the organic birefringent film 101 on which the diffraction grating 112 is formed is bonded to the transparent substrate 105.

  Looking at the planarity of the surface of the bonded organic birefringent film 101, in the bonding method in this example, long-span irregularities such as waviness remain as in the conventional example, but the irregularities in the range of several mm square are reduced.

  It is unevenness in the range of several mm square that affects the wavefront aberration of the polarization separation element 1. According to the manufacturing method of the polarization separation element of this example, the flatness of several mm square is good, and therefore the wavefront aberration of each polarization separation element 1 divided by dicing can be suppressed to a level that does not cause a problem in practice.

  Further, in the manufacturing method of the polarization separating element of this example, since the mask pattern has already been formed on the surface of the organic birefringent film 101 before bonding, long span irregularities such as waviness after bonding are 1 in the exposure process. Does not affect shot exposure area.

  The exposure area of one shot is determined by the flatness of the organic birefringent film 101 in the exposure step (b). In the exposure process, the organic birefringent film 101 is exposed to a flattened surface by applying a tension. Since the tension of the tension can be made larger than the centrifugal force by the rotation of the conventional example, the unevenness at the time of exposure can be reduced. As a result, the exposure area of one shot can be increased as compared with the conventional example, and the throughput of the exposure process can be improved.

  In the conventional bonding method, when a 2.0 μm pitch pattern is exposed, the exposure area of one shot is 10 mm square in order to increase the lithography yield to 90% or more. With this manufacturing method, the exposure area of one shot can be expanded 2.25 times.

Further, in this example, ITO (Indium thin Oxide) is used as a periodic mask pattern that transmits ultraviolet rays, but SiO ₂ , Si ₃ N ₄ , SiON, and In ₂ O ₃ are suitable for others. Since SiO ₂ , Si ₃ N ₄ , SiON, In ₂ O ₃ and ITO are resistant to oxygen ions and oxygen radicals, they are good etching masks in the dry etching process of the organic birefringent film 101 using NLD. A rectangular pattern can be formed on the organic birefringent film 101.

Furthermore, SiO ₂ , Si ₃ N ₄ , SiON, In ₂ O ₃ and ITO can be removed by acid. SiO ₂ , Si ₃ N ₄ , and SiON can be removed with a hydrofluoric acid based etchant, and In ₂ O ₃ and ITO can be removed with a ferric chloride and hydrochloric acid based etchant. Since the wet etching has a large selection ratio between the mask pattern 107 to be etched and the organic birefringent film 101, the etching pattern of the organic birefringent film 101 is not deteriorated in the removal process of the mask pattern 107, and a good diffraction grating 112 is formed. Shape can be made.

In addition, SiO ₂ , Si ₃ N ₄ , SiON, In ₂ O ₃ , and ITO are unnecessary in most organic solvents, so the UV curable adhesive 109 is dissolved during the second rotation, and the organic composite is dissolved. Even when an organic solvent that does not dissolve the refractive film 101 is dropped, the shape of the mask pattern does not deteriorate.

  Further, in this example, an organic solvent that dissolves the ultraviolet curable adhesive 109 and does not dissolve the organic birefringent film 101 is dropped during the second rotation, so that it is not covered with the organic birefringent film 101. The ultraviolet curable adhesive 109 around the substrate 105 is removed.

  Since the organic solvent is dropped while rotating the transparent substrate 105, centrifugal force is applied to the organic solvent, and the ultraviolet curable adhesive 109 in the region sandwiched between the organic birefringent film 101 and the transparent substrate 105 is applied. Hard to penetrate. Therefore, when the first ultraviolet ray is irradiated, a sufficient adhesion area is obtained between the transparent substrate 105 and the organic birefringent film 101.

  In addition, since no adhesive remains in the peripheral portion of the transparent substrate 105, foreign matter generation from the peripheral portion of the substrate 105 is very small even if the peripheral portion of the substrate 105 is handled between apparatuses or in the apparatus. The production yield of the polarization separation element 1 can be improved.

  In this example, isopropyl alcohol is used as the organic solvent. However, the organic solvent is not necessarily limited to isopropyl alcohol, and the organic solvent that dissolves the ultraviolet curable adhesive 109 and does not dissolve the organic birefringent film 101. If so, various organic solvents can be used. However, the acrylic or epoxy UV curable adhesive 109 widely used in the bonding process of bonded optical disks and the like is very well soluble in isopropyl alcohol and acetone, and therefore more harmful than other organic solvents. The use of isopropyl alcohol or acetone is more desirable from the viewpoint of work environment and equipment safety.

  In this example, after the transparent substrate 105 is fixed to the spin table 111, the acrylic UV curable adhesive 109 is dropped onto the central portion of the transparent substrate 105 while the spin table 111 is rotated, and the adhesive is applied. The method of applying the agent is not necessarily limited to this method, and after fixing the transparent substrate 105 to the spin table 111, the adhesive is dropped on the central portion of the transparent substrate 105 while the spin table 111 is stopped, and then the spin is performed. The table 111 may be rotated to spread the adhesive on the entire surface of the transparent substrate 105.

  Further, the ultraviolet curable adhesive 109 is applied at room temperature, but the viscosity of the ultraviolet curable adhesive 109 is high, and when the organic birefringent film 101 is placed, the fluidity of the ultraviolet curable adhesive 109 is poor, and bubbles are generated. When it is easy to entrain, the transparent substrate 105 coated with the ultraviolet curable adhesive 109 is heated using an oven, an infrared lamp, or the like to reduce the viscosity of the ultraviolet curable adhesive 109. It is desirable to mount the organic birefringent film 101 later. Alternatively, the ultraviolet curable adhesive 109 is preheated using an oven or the like to reduce the viscosity of the ultraviolet curable adhesive 109 and then applied to the transparent substrate 105 by the first rotation, and then the organic birefringent film It is also desirable to load 101.

[Polarization Separation Element Manufacturing Method 2]
3 and 4 are explanatory diagrams showing steps (a) to (n) of the method for manufacturing a polarization beam splitting element according to the second embodiment. The steps of this manufacturing method proceed in the order of (a) to (n).

  (A) First, one end is drawn out from the roll-shaped organic birefringent film 101, and a positive resist 102 (for example, TDMR-AR640 of Tokyo Ohka Kogyo Co., Ltd.) is applied to the surface of the organic birefringent film 101 by a roll coating method. Pre-bake at ℃. The organic birefringent film 101 has a width of 120 mm and a thickness of 100 μm.

  (B) A tension is applied to the organic birefringent film 101 to flatten it. Later, using a reduction projection exposure apparatus (for example, NSR2205i12D manufactured by Nikon Corporation), a periodic pattern (pitch 1.6 μm, duty = 50%) on the reticle 103 is made parallel to the slow axis of the organic birefringent film 101. Exposure. The exposure is performed at NA = 0.50, and one shot is 10 mm square.

  (C) Spray development is performed using a developer (for example, a 2.38% solution of NMD-3 manufactured by Tokyo Ohka Kogyo Co., Ltd.) to complete a periodic resist pattern 104 on the surface of the organic birefringent film 101.

(D) For curing the ultraviolet curable adhesive 109 used for bonding the organic birefringent film 101 and the transparent substrate 105 on the periodic resist pattern 104 while applying a tensile tension to the organic birefringent film 101. A film 106 that transmits ultraviolet rays is formed to a thickness of 50 to 100 nm by sputtering or vacuum deposition. In this example, a 60 nm SiO ₂ film is formed by sputtering as the film 106 that transmits ultraviolet rays.

(E) After forming the film 106 (SiO ₂ ) that transmits ultraviolet rays, the tension of the organic birefringent film 101 is released. Thereafter, the organic birefringent film 101 is immersed in an acetone bath, lifted off by applying ultrasonic vibration for 10 minutes, and a periodic mask pattern (SiO ₂ pattern) that transmits ultraviolet rays from the periodic resist pattern 104 is formed. To do.

  (F) Then, the organic birefringent film 101 is cut into φ90 mm.

  In this example, the steps (a) to (f) are performed consistently using an inline device.

  (G) Thereafter, a transparent substrate 105 made of optical glass (for example, BK7 manufactured by Schott) having a diameter of 100 mm and a thickness of 1.0 mm is placed on the spin table 111 and fixed to the spin table 111 by vacuum suction. Then, while rotating the spin table 111 at 10 to 50 rpm, 3 to 10 g of an epoxy-based ultraviolet curable adhesive 109 having a refractive index of 1.56 is dropped onto the central portion of the transparent substrate 105 using the dispenser 108. Thereafter, the spin table 111 is rotated at 150 to 500 rpm, and the transparent substrate 105 is rotated in the direction of the substrate surface (first rotation), so that the ultraviolet curable adhesive 109 is spread over the entire surface of the transparent substrate 105 (FIG. 3). (H)), the rotation of the spin table 111 is stopped.

(I) The mask pattern 107 (SiO ₂ pattern) is formed on the ultraviolet curable adhesive 109 using a mounting device while the center of the organic birefringent film 101 is substantially aligned with the rotation center of the spin table 111. The organic birefringent film 101 is placed on the surface opposite to the surface that has been subjected to.

  (J) Then, by rotating the spin table 111 at 1000 to 3000 rpm, the transparent substrate 105 is rotated in the direction of the substrate surface (second rotation), the UV curable adhesive 109 is shaken off, and the thickness of the adhesive layer Is made constant in the plane of the substrate 105 to flatten the surface of the organic birefringent film 101.

  (K) 60 seconds after the start of the second rotation, acetone is dropped on the organic birefringent film 101 while performing the second rotation, and ultraviolet light (first ultraviolet light) is emitted from the organic birefringent film 101 side using a metal halide lamp. To cure the ultraviolet curable adhesive 109.

  Acetone is an organic solvent that dissolves the epoxy ultraviolet curable adhesive 109 used in this example and does not dissolve the organic birefringent film 101. Therefore, the ultraviolet curable adhesive 109 remaining in the periphery of the transparent substrate 105 after the step (k) is removed with acetone.

  In this example, it is preferable to cure the ultraviolet curable adhesive 109 while flattening the organic birefringent film 101 by centrifugal force. Therefore, the recommended curing conditions for the ultraviolet curable adhesive 109 are achieved with an ultraviolet irradiation time of 10 minutes. Thus, the light intensity of ultraviolet rays is set.

(L) Stop the rotation of the spin table 111, remove the transparent substrate 105 to which the organic birefringent film 101 is bonded from the spin table 111, and use an NLD etching apparatus in an etching gas atmosphere mainly containing oxygen gas. The organic birefringent film 101 is etched to a depth of 3 μm using the mask pattern 107 (SiO ₂ pattern) that transmits ultraviolet rays of the mask as a mask. Then, the mask pattern 107 (SiO ₂ pattern) is removed using a SiO ₂ etching solution using hydrofluoric acid and nitric acid, and the diffraction grating 112 is completed.

(M) Then, a substrate 105 on which a diffraction grating 112 is formed is placed on a flat-processed stainless steel plate (not shown) having a diameter of 200 mm and a thickness of 50 mm, and an optically isotropic epoxy UV curing type is provided on the surface of the diffraction grating 112. 1.0 mL of the adhesive 109 (isotropic adhesive 113) is dropped with a micro syringe (not shown). Then, an opposing transparent substrate 114 (optical glass (for example, using BK7 of Schott)) having a diameter of 100 mm and a thickness of 1 mm, which is optically polished on both sides, is placed, and further optically polished optical glass is placed on the opposing transparent substrate 114 and facing. A pressure of 100 gf / cm ² is applied to the transparent substrate 114 to spread the isotropic adhesive 113 over the entire adherend surface. An antireflection film (not shown) is formed on the surface of the counter transparent substrate 114 opposite to the surface to be bonded so as to minimize the reflection of incident light. In this state, the isotropic adhesive 113 is cured by irradiating ultraviolet rays through the counter transparent substrate 114.
(N) Thereafter, the product 116 is cut into a 5 mm square by using a dicing saw 115 to complete a plurality of polarization separation elements 1.

  In the polarization separation element 1 manufactured in this way, an organic birefringent film 101 having a different refractive index is bonded to a transparent substrate 105 with respect to different vibration surfaces of incident light with an ultraviolet curable adhesive 109, thereby organic birefringence. The diffraction grating 112 is formed by forming periodic irregularities on the surface of the film 101.

  The polarization splitting element 1 thus completed is irradiated with S-shaped light having a wavelength of 680 nm, and the light receiving element receives the first-order diffracted light and measures the first-order diffraction efficiency. As a result, the polarization separation element 1 in which the diffraction grating 112 is well formed generally achieves a diffraction efficiency of 32% or more.

  Also by such a method of manufacturing a polarization separation element, the entire surface of the diffraction grating 112 can be bonded in the same manner as the method of manufacturing method 1 of the polarization separation element.

  Compared with the conventional example in which the organic birefringent film 101 on which the diffraction grating 112 is formed is bonded to the transparent substrate 105 in order to protect the region where the periodic mask pattern that transmits ultraviolet rays becomes the convex portion of the diffraction grating 112. Wavefront aberration can be suppressed.

  Looking at the planarity of the surface of the bonded organic birefringent film 101, long-span irregularities such as waviness remain as in the polarization separation element manufacturing method 1, but the irregularities in the range of several mm square are reduced. Therefore, the wavefront aberration of each polarization separation element 1 divided in the step (n) can be suppressed to a level that causes no problem in practice.

  Further, the unevenness at the time of exposure can be reduced by performing exposure by applying a tension to the organic birefringent film 101 in the exposure step (b) and performing exposure before bonding. As a result, the exposure area of one shot can be increased as compared with the conventional example, and the throughput of the exposure process can be improved.

  In the conventional bonding method, when a pattern having a pitch of 1.6 μm is exposed, in order to increase the lithography yield to 90% or more, the exposure area of one shot needs to be 5 mm square. According to the manufacturing method of the separation element, the exposure area of one shot can be expanded four times.

Further, in this example, SiO ₂ is used as the periodic mask pattern 107 that transmits ultraviolet rays. However, SiO ₂ is a good etching mask in the dry etching process of the organic birefringent film 101 like ITO.

Furthermore, since SiO ₂ can be removed by a hydrofluoric acid-based etching solution, a favorable shape of the diffraction grating 112 can be formed.

In addition, since SiO ₂ is not necessary for the organic solvent, even if the organic solvent that dissolves the ultraviolet curable adhesive 109 and does not dissolve the organic birefringent film 101 is dropped during the second rotation described above, The shape of the mask pattern does not deteriorate.
Also in this example, since the ultraviolet curable adhesive 109 is dissolved during the second rotation and the organic solvent that does not dissolve the organic birefringent film 101 is dropped, the transparent substrate 105 not covered with the organic birefringent film 101 is used. The UV curable adhesive 109 in the vicinity of is removed.

[Polarization Separation Element Manufacturing Method 3]
5 and 6 are explanatory diagrams showing steps (a) to (n) of the method for manufacturing a polarization beam splitting element according to the third embodiment. The steps of this manufacturing method proceed in the order of (a) to (n).

  (A) First, tensile tension is applied to the four corners of the organic birefringent film 101 having a thickness of 80 μm cut into 120 mm square, and the organic birefringent film 101 is flattened. Thereafter, with a tensile tension applied to the organic birefringent film 101, 0.7 μm of positive resist 102 (for example, TDMR-AR640 manufactured by Tokyo Ohka Kogyo Co., Ltd.) is applied to the surface of the organic birefringent film 101 by a spray method or a roll coat method. Apply and pre-bake at 60 ° C.

  (B) A periodic pattern (pitch 1.2 μm, duty) on the reticle 103 using a reduction projection exposure apparatus (for example, NSR2205i12D manufactured by Nikon Corporation) with a tensile tension applied to the organic birefringent film 101. = 50%) is exposed parallel to the slow axis of the organic birefringent film 101. The exposure is performed with NA = 0.50, and one shot is 5 mm square.

  (C) Dip development is performed using a developer (for example, a 2.38% solution of NMD-3 manufactured by Tokyo Ohka Kogyo Co., Ltd.) to complete a periodic resist pattern 104 on the surface of the organic birefringent film 101.

  (D) For curing the ultraviolet curable adhesive 109 used for bonding the organic birefringent film 101 and the transparent substrate 105 onto the periodic resist pattern 104 while applying a tensile tension to the organic birefringent film 101. A film 106 that transmits ultraviolet rays is formed to a thickness of 50 to 100 nm by sputtering or vacuum deposition. In this example, a 50 nm thick SiON film is formed by sputtering as the film 106 that transmits ultraviolet rays.

  (E) After the film 106 (SiON) that transmits ultraviolet rays is formed, the tension of the organic birefringent film 101 is released. Thereafter, the organic birefringent film 101 is immersed in an acetone bath and lifted off by applying ultrasonic vibration for 10 minutes to form a periodic mask pattern 107 (SiON pattern) that transmits ultraviolet rays from the periodic resist pattern 104. To do. Thereafter, the organic birefringent film 101 is cut into φ90 mm.

  (F) A transparent substrate 105 made of optical glass having a diameter of 100 mm and a thickness of 1.0 mm (for example, BK7 manufactured by Schott) is placed on the spin table 111 and fixed to the spin table 111 by vacuum suction. Then, while rotating the spin table 111 at 10 to 50 rpm, 3 to 10 g of an epoxy-based ultraviolet curable adhesive 109 having a refractive index of 1.56 is dropped onto the central portion of the transparent substrate 105 using the dispenser 108. Thereafter, by rotating the spin table 111 at 150 to 500 rpm, the transparent substrate 105 is rotated in the substrate surface direction (first rotation), and the ultraviolet curable adhesive 109 is spread over the entire surface of the transparent substrate 105 (FIG. 5G )), The rotation of the spin table 111 is stopped.

  (H) Then, the mask pattern 107 (SiON pattern) is formed on the ultraviolet curable adhesive 109 using the mounting device while the center of the organic birefringent film 101 is substantially aligned with the rotation center of the spin table 111. The organic birefringent film 101 was placed on the surface opposite to the formed surface.

  (I) The spin table 111 is rotated at 1000 to 3000 rpm, the transparent substrate 105 is rotated in the substrate surface direction (second rotation), the UV curable adhesive 109 is shaken off, and the thickness of the adhesive layer is set to The surface of the organic birefringent film 101 is flattened while being constant in the plane.

  (J) Then, 60 seconds after the start of the second rotation, acetone is dropped on the organic birefringent film 101 while performing the second rotation, and ultraviolet rays (first first) are used from the organic birefringent film 101 side using a metal halide lamp. The ultraviolet curable adhesive 109 is semi-cured by irradiating with ultraviolet rays.

  Acetone is an organic solvent that dissolves the epoxy ultraviolet curable adhesive 109 used in this example and does not dissolve the organic birefringent film 101. Therefore, the ultraviolet curable adhesive 109 remaining around the transparent substrate 105 after the step (j) is removed with acetone.

  Further, in this example, the ultraviolet curable adhesive 109 may be semi-cured by the first ultraviolet irradiation, so that the first ultraviolet irradiation is 1/10 to 1/3 the energy of the manufacturing method 2 of the polarization beam splitting element. To do.

  (K) Thereafter, the rotation of the spin table 111 is stopped, and ultraviolet rays (second ultraviolet rays) are irradiated from the organic birefringent film 101 side using a metal halide lamp to completely cure the ultraviolet curable adhesive 109.

(L) The transparent substrate 105 to which the organic birefringent film 101 is bonded is removed from the spin table 111, and the mask pattern 107 (SiON) that transmits the ultraviolet rays in an etching gas atmosphere containing oxygen gas as a main component using an NLD etching apparatus. Using the pattern as a mask, the organic birefringent film 101 is etched to a depth of 2.4 μm. Then, the mask pattern 107 (SiON pattern) is removed using a SiO ₂ etching solution using hydrofluoric acid and nitric acid, and the diffraction grating 112 is completed.

(M) Thereafter, a substrate 105 on which a diffraction grating 112 is formed is placed on a flat-finished stainless steel plate (not shown) having a diameter of 200 mm and a thickness of 50 mm, and an optically isotropic epoxy ultraviolet curing type is provided on the surface of the diffraction grating 112. 1.0 mL of the adhesive 109 (isotropic adhesive 113) is dropped with a micro syringe (not shown). Then, the opposite transparent substrate 114 (optical glass (for example, using BK7 manufactured by Schott)) having a diameter of 100 mm and a thickness of 1 mm, which is optically polished on both sides, is placed, and further optically polished optical glass is placed on the opposite transparent substrate 114 to face the substrate. A pressure of 100 gf / cm ² is applied to the transparent substrate 114 to spread the isotropic adhesive 113 over the entire adherend surface. An antireflection film (not shown) is formed on the surface of the counter transparent substrate 114 opposite to the surface to be bonded so as to minimize the reflection of incident light. In this state, the isotropic adhesive 113 is cured by irradiating ultraviolet rays through the counter transparent substrate 114.
(N) The product 116 is cut into a 5 mm square using a dicing saw 115 to complete a plurality of polarized light separating elements 1.

  In the polarization separation element 1 manufactured in this way, an organic birefringent film 101 having a different refractive index is bonded to a transparent substrate 105 with respect to different vibration surfaces of incident light with an ultraviolet curable adhesive 109, thereby organic birefringence. The diffraction grating 112 is formed by forming periodic irregularities on the surface of the film 101.

  The polarized light separating element 1 thus completed is irradiated with S-polarized light having a wavelength of 400 nm, the first-order diffracted light is received by the light-receiving element, and the first-order diffraction efficiency is measured. As a result, the polarization separation element 1 in which the diffraction grating 112 is well formed achieves the specified diffraction efficiency of 25% or more.

  According to such a method of manufacturing a polarization separation element, the ultraviolet curable adhesive 109 is applied to the entire surface of the transparent substrate 105 by the first rotation, and therefore, no region without the adhesive 109 is generated on the transparent substrate 105. Therefore, when the organic birefringent film 101 is placed on the surface opposite to the surface on which the periodic mask pattern 107 that transmits ultraviolet rays is formed on the transparent substrate 105 to which the adhesive 109 is applied, the organic birefringent film 101 is The entire surface contacts the surface of the transparent substrate 105 via an adhesive.

In addition, since the periodic mask pattern is formed from the film 106 that transmits ultraviolet rays, not only the region between the periodic mask patterns 107 but also the periodicity due to the first ultraviolet irradiation and the second ultraviolet irradiation. The ultraviolet curable adhesive 109 just below the typical mask pattern 107 is also cured, and the entire surface can be bonded.
Furthermore, in order to protect the region where the periodic mask pattern 107 that transmits ultraviolet rays becomes a convex portion of the diffraction grating 112, the organic birefringent film 101 on which the diffraction grating 112 is formed is compared with the conventional example in which the transparent substrate 105 is bonded. Thus, wavefront aberration can be suppressed.

  Further, since the ultraviolet curable adhesive 109 is semi-cured by performing the first ultraviolet irradiation during the second rotation, the adhesive force between the ultraviolet curable adhesive 109 and the organic birefringent film 101 is increased, and the transparent substrate The misalignment of the organic birefringent film 101 caused by the rotation of 105 can be reduced. As a result, the frequency with which the organic birefringent film 101 protrudes from the transparent substrate 105 is reduced, the conveyance failure can be reduced, and the polarization separation element 1 can be manufactured at a lower cost.

In order to make the thickness of the adhesive layer uniform, the transparent substrate 105 must be rotated and the adhesive must be shaken off to some extent, so that the UV curable adhesive 109 is rapidly cured by the first UV irradiation and has a high viscosity. Therefore, it is desirable to irradiate the first ultraviolet ray with a relatively weak intensity. In this example, the ultraviolet ray irradiation is performed with an intensity of 1/10 of the second ultraviolet ray irradiation.
Further, in order to make the thickness of the adhesive layer uniform while increasing the viscosity of the UV curable adhesive 109 by the first UV irradiation, it is necessary to optimize the recipe for the second rotation. During the first ultraviolet irradiation, the rotational speed is increased in three steps.

  In this example, the first ultraviolet ray is irradiated while rotating the transparent substrate 105 during the dropping of the organic solvent. However, the irradiation of the first ultraviolet ray is not necessarily limited to this, or before the dropping of the organic solvent, or It does not matter if it is one after dropping, as long as the ultraviolet curable adhesive 109 is semi-cured by the first ultraviolet irradiation to increase the viscosity, and the adhesive strength with the organic birefringent film 101 is increased.

  Further, according to the manufacturing method of this example, the organic birefringent film 101 slightly moves during the second rotation, and the organic birefringent film 101 does not protrude from the transparent substrate 105, but the organic birefringent film 101 rotates. In addition, since a periodic mask pattern that transmits ultraviolet rays is formed in parallel to one specific direction (that is, to the slow axis) of the two directions in the plane of the organic birefringent film 101 before bonding, The diffraction grating 112 of the polarized light separating element 1 can be aligned in one specific direction (that is, the slow axis) of the two directions in the plane of the organic birefringent film 101. As a result, a predetermined diffraction efficiency is obtained. Therefore, compared with the conventional bonding method, in this example, the specification for the deviation of the organic birefringent film 101 during the second rotation can be limited to the distance between the end of the organic birefringent film 101 and the end of the transparent substrate 105.

  In general, the slow axis and the fast axis of the organic birefringent film 101 are supplied from the manufacturer so that they can be determined by the outer shape. Therefore, in the exposure step (b), exposure is performed based on the outer shape of the organic birefringent film 101. Thus, it is possible to form a periodic mask pattern that transmits ultraviolet light so as to be aligned in one specific direction out of the two directions in the plane of the organic birefringent film 101, and can be realized relatively easily.

  Looking at the planarity of the surface of the bonded organic birefringent film 101, the bonding method of this example has long-span irregularities such as waviness as in the manufacturing methods 1 and 2 of the polarized light separating element, but it has a range of several mm square. The unevenness of becomes smaller. Therefore, the wavefront aberration of each polarization separation element 1 divided by dicing can be suppressed to a level that does not cause a problem in practice.

  Further, in the manufacturing method of the polarization separating element of this example, since the mask pattern 107 is already formed on the surface of the organic birefringent film 101 before bonding, long span irregularities such as waviness after bonding are not observed in the exposure process. Does not affect the exposure area of one shot. In the exposure step (b), the organic birefringent film 101 is flattened by applying tension to the organic birefringent film 101, so that unevenness can be reduced during exposure. As a result, when a finer pattern is exposed, the lithography yield can be improved as compared with the conventional example.

  In the bonding method of the conventional example, when a 1.2 μm pitch is exposed, the lithography yield is about 40 to 60% even if one shot is 5 mm square, but according to the manufacturing method of the polarization separating element of this example, the yield is 70%. % Can be improved.

In this example, SiON is used as the periodic mask pattern 107 that transmits ultraviolet rays. However, SiON is a good etching mask in the dry etching process of the organic birefringent film 101 like ITO and SiO ₂ .

  Furthermore, since SiON can be removed by a hydrofluoric acid-based etching solution, a favorable shape of the diffraction grating 112 can be formed.

In addition, since SiO ₂ is not necessary for the organic solvent, the mask pattern can be removed even when the organic solvent that dissolves the ultraviolet curable adhesive 109 and does not dissolve the organic birefringent film 101 is dropped during the second rotation. The shape of 107 does not deteriorate.

  Further, in this example, an organic solvent that dissolves the ultraviolet curable adhesive 109 and does not dissolve the organic birefringent film 101 is dropped during the second rotation. The ultraviolet curable adhesive 109 around 105 is removed.

  Since the light intensity of the first ultraviolet irradiation is low, the ultraviolet curable adhesive 109 is slowly cured, and the adhesive around the transparent substrate 105 is sufficiently removed by the dropping of the organic solvent.

[Polarization Separation Element Manufacturing Method 4]
7 and 8 are explanatory views showing steps (a) to (r) of the method for manufacturing a polarization beam splitting element according to the fourth embodiment. The steps of this production method proceed in the order of (a) to (r).

  (A) Tensile tension is applied to the four corners of the organic birefringent film 101 having a thickness of 80 μm cut into 200 mm square, and the organic birefringent film 101 is flattened. Thereafter, with a tensile tension applied to the organic birefringent film 101, a 0.7 μm positive resist 102 (for example, TDMR-AR640 manufactured by Tokyo Ohka Kogyo Co., Ltd.) is applied to the surface of the organic birefringent film 101 by a roll coating method. Pre-bake at ℃.

  (B) A periodic pattern (pitch: 2.0 μm, duty = 50) on the reticle 103 using a reduction projection exposure apparatus (for example, NSR 4425i manufactured by Nikon Corporation) with a tension applied to the organic birefringent film 101. %) Is exposed parallel to the slow axis of the organic birefringent film 101. Exposure is performed at NA = 0.30, and one shot is 30 mm square.

  (C) Then, dip development is performed using a developer (for example, a 2.38% solution of NMD-3 manufactured by Tokyo Ohka Kogyo Co., Ltd.) to complete a periodic resist pattern 104 on the surface of the organic birefringent film 101.

(D) Ultraviolet light for curing the ultraviolet curable adhesive 109 used for bonding the organic birefringent film 101 and the transparent substrate 105 on the periodic resist pattern 104 while applying tension to the organic birefringent film 101. A film 106 that transmits light is formed to a thickness of 50 to 100 nm by a sputtering method or a vacuum evaporation method. In this example, an In ₂ O ₃ film by EB vapor deposition is formed to a thickness of 60 nm as the film 106 that transmits ultraviolet rays.

(E) Next, after forming a film 106 (In ₂ O ₃ ) that transmits ultraviolet rays, the tension of the organic birefringent film 101 is released. Thereafter, the organic birefringent film 101 is immersed in an acetone bath, lifted off by applying ultrasonic vibration for 10 minutes, and a periodic mask pattern (In ₂ O ₃ pattern) that transmits ultraviolet rays from the periodic resist pattern 104. Form. Thereafter, the organic birefringent film 101 is cut to φ155 mm.

  (F) A transparent substrate 105 made of optical glass having a diameter of 165 mm, a thickness of 1.0 mm, and an orientation flat (for example, BK7 manufactured by Schott) is placed on the spin table 111 and fixed to the spin table 111 by vacuum suction. Thereafter, while rotating the spin table 111 at 10 to 50 rpm, 8 to 13 g of an epoxy ultraviolet curable adhesive 109 having a refractive index of 1.56 is dropped onto the central portion of the transparent substrate 105 using the dispenser 108. Thereafter, the spin table 111 is rotated at 100 to 200 rpm, the transparent substrate 105 is rotated in the substrate surface direction (first rotation), and the ultraviolet curable adhesive 109 is spread over the entire surface of the transparent substrate 105 (FIG. 7G). Then, the rotation of the spin table 111 is stopped.

(H) While aligning the center of the organic birefringent film 101 substantially with the rotation center of the spin table 111, the mask pattern (In ₂ O ₃ pattern) is formed on the ultraviolet curable adhesive 109 using a mounting device. The organic birefringent film 101 was placed on the surface facing the formed surface.

  (I) The spin table 111 is rotated at 400 rpm for 8 seconds, the transparent substrate 105 is rotated in the substrate surface direction (second rotation), and the adhesive is shaken off.

  (J) When the rotation of the spin table 111 is stopped and the misalignment of the organic birefringent film 101 is visually observed, the organic birefringent film 101 moves about 2 mm on the transparent substrate 105, and the organic birefringent film 101 There is a case where the center and the rotation center of the spin table 111 are greatly deviated. In this case, the adjustment jig 131 is used to push the end of the organic birefringent film 101 on the outer side to the center side of the transparent substrate 105 (see FIG. 9A) and slide on the transparent substrate 105. The organic birefringent film 101 is moved (hereinafter, “sliding” is referred to as “sliding”), and the position of the organic birefringent film 101 is corrected (that is, the center of the transparent substrate 105 and the organic birefringent film 101 are aligned). (FIG. 9B).

  (K) The spin table 111 is rotated again, the transparent substrate 105 is rotated in the substrate surface direction (second rotation), and the adhesive is shaken off. Then, the misalignment of the organic birefringent film 101 is visually observed, and any misalignment is corrected. This operation is repeated, but an example of this case is given below.

  First, the spin table 111 is rotated again at 400 rpm for 2 seconds, the transparent substrate 105 is rotated in the substrate surface direction (second rotation), and the adhesive is shaken off. When the rotation of the spin table 111 was stopped and the misalignment of the organic birefringent film 101 was observed visually, the organic birefringent film 101 hardly moved on the transparent substrate 105.

  Thereafter, the spin table 111 is rotated at 700 rpm for 5 seconds, the transparent substrate 105 is rotated in the substrate surface direction (second rotation), and the adhesive is shaken off. When the rotation of the spin table 111 was stopped and the misalignment of the organic birefringent film 101 was visually observed, the organic birefringent film 101 moved about 2 mm on the transparent substrate 105. Therefore, using the adjusting jig 131 described above, the organic birefringent film 101 was slid on the transparent substrate 105 to correct the position of the organic birefringent film 101.

  Thereafter, the spin table 111 is rotated again at 700 rpm for 11 seconds, the transparent substrate 105 is rotated in the direction of the substrate surface (second rotation), and the adhesive is shaken off. When the rotation of the spin table 111 was stopped and the misalignment of the organic birefringent film 101 was visually observed, the organic birefringent film 101 moved about 4 mm on the transparent substrate 105. Therefore, using the adjusting jig 131 described above, the organic birefringent film 101 was slid on the transparent substrate 105 to correct the position of the organic birefringent film 101.

  Thereafter, the spin table 111 was again rotated at 700 rpm for 11 seconds, the transparent substrate 105 was rotated in the direction of the substrate surface (second rotation), and the adhesive was shaken off. Thereafter, when the rotation of the spin table 111 was stopped and the positional deviation of the organic birefringent film 101 was visually observed, the organic birefringent film 101 hardly moved on the transparent substrate 105.

  Thereafter, the spin table 111 was rotated again at 700 rpm for 6 seconds, the transparent substrate 105 was rotated in the direction of the substrate surface (second rotation), and the adhesive was shaken off. When the rotation of the spin table 111 was stopped and the misalignment of the organic birefringent film 101 was visually observed, the organic birefringent film 101 hardly moved on the transparent substrate 105.

  Thereafter, the spin table 111 was rotated at 900 rpm for 3 seconds, the transparent substrate 105 was rotated in the direction of the substrate surface (second rotation), and the adhesive was shaken off. When the rotation of the spin table 111 was stopped and the displacement of the organic birefringent film 101 was visually observed, the organic birefringent film 101 moved on the transparent substrate 105 by about 5 mm. Thereafter, using an adjustment jig, the organic birefringent film 101 was slid on the transparent substrate 105 to correct the position of the organic birefringent film 101.

  Thereafter, the spin table 111 was again rotated at 900 rpm for 8 seconds, the transparent substrate 105 was rotated in the substrate surface direction (second rotation), and the adhesive was shaken off. When the rotation of the spin table 111 was stopped and the misalignment of the organic birefringent film 101 was visually observed, the organic birefringent film 101 moved about 2 mm on the transparent substrate 105. Thereafter, using the adjustment jig 131, the organic birefringent film 101 was slid on the transparent substrate 105 to correct the position of the organic birefringent film 101.

  Thereafter, the spin table 111 was rotated again at 900 rpm for 29 seconds, the transparent substrate 105 was rotated in the direction of the substrate surface (second rotation), and the adhesive was shaken off. When the rotation of the spin table 111 was stopped and the misalignment of the organic birefringent film 101 was visually observed, the organic birefringent film 101 hardly moved on the transparent substrate 105.

  Thereafter, the spin table 111 was again rotated at 900 rpm for 20 seconds, the transparent substrate 105 was rotated in the direction of the substrate surface (second rotation), and the adhesive was shaken off. Thereafter, the rotation of the spin table 111 is stopped, and the relative position between the organic birefringent film 101 and the transparent substrate 105 is observed with a length measuring microscope having a magnification of 4 to 50 times. The edge distance was 4 mm or more.

In the specification after the organic birefringent film 101 is bonded, the distance between the end of the transparent substrate 105 and the end of the organic birefringent film 101 is defined by the clamp width of the etching apparatus. In this example, it is 2 mm or more.
From the measurement result with the above-mentioned microscope, it was confirmed that the distance between the end of the organic birefringent film 101 and the end of the transparent substrate 105 was within an allowable value.

  (L) Next, in a state where the rotation of the spin table 111 is stopped, the ultraviolet curable adhesive 109 is semi-cured by irradiating the first ultraviolet light from the organic birefringent film 101 side using a high pressure mercury lamp.

  (M) The transparent substrate 105 is rotated at 700 rpm for 45 seconds, the transparent substrate 105 is rotated in the substrate surface direction (third rotation), and acetone is dropped at the boundary between the organic birefringent film 101 and the transparent substrate 105. Acetone is an organic solvent that dissolves the epoxy ultraviolet curable adhesive 109 used in this example and does not dissolve the organic birefringent film 101. By this step, the ultraviolet curable adhesive 109 remaining on the periphery of the substrate after the step (m) is removed with acetone. In this example, since the ultraviolet curable adhesive 109 may be semi-cured by the first ultraviolet irradiation, the first ultraviolet irradiation has energy of 1/10 to 1/3 of the recommended curing conditions.

  (N) Thereafter, the rotation of the spin table 111 is stopped, and the second ultraviolet ray is irradiated from the organic birefringent film 101 side using a high-pressure mercury lamp, and the ultraviolet curable adhesive 109 is completely cured.

  (O) The transparent substrate 105 is removed from the spin table 111, and the relative position between the organic birefringent film 101 and the transparent substrate 105 is measured again with a length measuring microscope having a magnification of 4 to 50 times. As a result, the distance between the end of the organic birefringent film 101 and the end of the transparent substrate 105 did not change even after the steps (l) to (n).

(P) An organic birefringent film using the mask pattern 107 (In ₂ O ₃ ) that transmits ultraviolet light as a mask for the transparent substrate 105 in an etching gas atmosphere containing oxygen gas as a main component using an NLD etching apparatus. 101 is etched to a depth of 3 μm. Thereafter, the mask pattern 107 (In ₂ O ₃ pattern) is removed using an In ₂ O ₃ etching solution using hydrochloric acid and ferric chloride, and the diffraction grating 112 is completed.

(Q) A transparent substrate 105 on which a diffraction grating 112 is formed is placed on a flat-finished stainless steel plate (not shown) having a diameter of 250 mm and a thickness of 50 mm, and an optically isotropic acrylic ultraviolet curable adhesive is adhered to the surface of the diffraction grating 112. 1.2 mL of the agent 109 (isotropic adhesive 113) is dropped with a micro syringe. Then, both surfaces are optically polished on a counter transparent substrate 114 (optical glass (for example, BK7 of Schott)) having a diameter of 165 mm and a thickness of 1 mm, and further optically polished optical glass is mounted on the counter transparent substrate 114. A pressure of 100 gf / cm ² was applied to the surface to spread the isotropic adhesive 113 over the entire adherend surface. In this state, the isotropic adhesive 113 is cured by irradiating ultraviolet rays through the counter transparent substrate 114.

  (R) Then, it cuts out into 5 mm square using the dicing saw 115, and completes the several polarization separation element 1. FIG.

  In the polarization separation element 1 manufactured in this way, an organic birefringent film 101 having a different refractive index is bonded to a transparent substrate 105 with respect to different vibration surfaces of incident light with an ultraviolet curable adhesive 109, thereby organic birefringence. The diffraction grating 112 is formed by forming periodic irregularities on the surface of the film 101.

  The polarized light separating element 1 thus completed is irradiated with S-polarized light having a wavelength of 680 nm, and the first-order diffracted light is received by the light-receiving element, and the first-order diffraction efficiency is measured. As a result, all the polarization separation elements 1 in which the diffraction grating 112 is well formed achieve the specified diffraction efficiency of 32% or more.

  The substrate 105 to which the organic birefringent film 101 is bonded by the steps (a) to (r) is cut using a dicing saw 115, the cross section is observed with a 200-fold metal microscope, and the bonding layer in the diameter direction of the substrate The result of measuring the thickness is shown in FIG. As shown in FIG. 10, regardless of the distance from the end of the organic birefringent film 101, it was confirmed that the adhesive layer thickness in this example was an average of 31 μm and was substantially uniform in the diameter direction. Then, there was no problem in the film thickness control of the adhesive layer.

  Also by this manufacturing method, the entire surface can be bonded by the first ultraviolet irradiation and the second ultraviolet irradiation as in the manufacturing method 3 of the polarization beam splitting element.

  Compared with the conventional example in which the organic birefringent film 101 on which the diffraction grating 112 is formed is bonded to the transparent substrate 105 in order to protect the region where the periodic mask pattern 107 that transmits ultraviolet rays becomes the convex portion of the diffraction grating 112. Thus, wavefront aberration can be suppressed.

  Further, according to the manufacturing method of this example, the bonding process of the organic birefringent film 101 applies the ultraviolet curable adhesive 109 on the transparent substrate 105, and then the organic birefringent film 101 is applied on the ultraviolet curable adhesive 109. After that, the transparent substrate 105 is rotated, and after the rotation of the transparent substrate 105 is stopped, the organic birefringent film 101 is slid on the transparent substrate 105 to correct the position, and then the transparent substrate 105 is rotated. The rotation of the transparent substrate 105 is stopped again, and after confirming that the relative position between the transparent substrate 105 and the organic birefringent film 101 is within the allowable value, the rotation of the transparent substrate 105 and the transparent substrate 105 is stopped. The ultraviolet curable adhesive 109 is semi-cured by irradiating the ultraviolet ray 1. Therefore, the relative position between the transparent substrate 105 and the organic birefringent film 101 can be kept within an allowable value, and the adhesion force between the organic birefringent film 101 and the transparent substrate 105 can be increased. As a result, the displacement of the organic birefringent film 101 is less likely to occur during the third rotation, and the frequency at which the organic birefringent film 101 protrudes from the transparent substrate 105 can be further reduced.

In addition, also in this example, the organic birefringent film 101 moves slightly during the third rotation, and the organic birefringent film 101 does not protrude from the transparent substrate 105, but even when the organic birefringent film 101 rotates, Since the periodic mask pattern 107 that transmits ultraviolet rays is formed in parallel with one specific direction (that is, with respect to the slow axis) of the two directions in the plane of the organic birefringent film 101 before bonding, it is manufactured. The diffraction grating 112 of the polarization separating element 1 is aligned in one specific direction (that is, the slow axis) of the two directions in the plane of the organic birefringent film 101, and a predetermined diffraction efficiency can be obtained.
Therefore, in the manufacturing method of this example, after the second rotation is stopped, the item for which it is necessary to confirm that the relative position between the transparent substrate 105 and the organic birefringent film 101 is within the allowable value is the organic birefringent film 101. One item of the distance between the edge and the edge of the transparent substrate 105 is sufficient.

  Looking at the planarity of the surface of the bonded organic birefringent film 101, in the bonding method of this example, as in the manufacturing methods 1 to 3 of the polarization separating element, long-span irregularities such as waviness remain, but in the range of several mm square. The unevenness of becomes smaller. As a result, the wavefront aberration of each polarization separation element 1 divided by dicing can be suppressed to a level that does not cause a problem in practice.

  Also in this example, the long span unevenness such as the waviness after bonding does not affect the exposure area of one shot in the exposure process, and the exposure area of one shot is the organic birefringent film 101 in the exposure process of (b). Determined by the flatness. In this exposure step, the organic birefringent film 101 is flattened by applying tension to the organic birefringent film 101, so that the tension can be made larger than the centrifugal force due to the rotation of the conventional example, and the unevenness at the time of exposure can be reduced. As a result, the exposure area of one shot can be increased as compared with the conventional example, and the throughput of the exposure process can be improved.

  In the conventional bonding method, when a reduced projection exposure apparatus with NA = 0.30 is used, when exposing a pattern with a pitch of 2.0 μm, in order to increase the lithography yield to 90% or more, the exposure area of one shot is reduced. Although it was necessary to make it 15 mm square, the exposure area of one shot could be expanded four times by the method of manufacturing the polarization separating element 1 of this example.

In this example, In ₂ O ₃ is used as the periodic mask pattern 107 that transmits ultraviolet rays. However, since In ₂ O ₃ is resistant to oxygen ions and oxygen radicals, the organic birefringent film 101 is dried. In the etching process, a good etching mask is obtained.

Furthermore, since In ₂ O ₃ can be removed with a ferric chloride and hydrochloric acid-based etching solution, the etching pattern of the organic birefringent film 101 is not deteriorated in the removal process of the mask pattern 107, and a good diffraction grating 112 shape can be obtained. Can be made.

In addition, since In ₂ O ₃ is unnecessary for most organic solvents, an organic solvent that dissolves the UV curable adhesive 109 and does not dissolve the organic birefringent film 101 during the second rotation is dropped. However, the shape of the mask pattern 107 does not deteriorate.

  According to the manufacturing method of the polarization separating element of this example, the ultraviolet curable adhesive is rotated (third rotation) while the transparent substrate 105 is rotated (third rotation) after irradiating the first ultraviolet ray and semi-curing the ultraviolet curable adhesive 109. Since the organic solvent which dissolves 109 and does not dissolve the organic birefringent film 101 is dropped, the ultraviolet curable adhesive 109 around the transparent substrate 105 not covered with the organic birefringent film 101 can be removed. Further, since the organic solvent is dropped while rotating the transparent substrate 105, a centrifugal force is applied to the organic solvent, and the ultraviolet curable adhesive 109 in the region sandwiched between the organic birefringent film 101 and the transparent substrate 105 is applied. The transparent substrate 105 and the organic birefringent film 101 can obtain a sufficient bonding area because they do not easily penetrate into the substrate. As a result, no adhesive remains in the peripheral portion of the transparent substrate 105. Therefore, even if the peripheral portion of the substrate is handled by conveyance between apparatuses or in the apparatus, the generation of foreign matter from the peripheral portion of the substrate is very small. 1 production yield can be improved.

  In this example, the organic birefringent film 101 after rotation is visually observed for deviation, and the relative position between the organic birefringent film 101 and the transparent substrate 105 is accurately measured with a length measuring microscope before the first ultraviolet ray is irradiated. However, the deviation of the organic birefringent film 101 after rotation may be accurately measured using a length measuring microscope or the like each time. In addition, it is more desirable to calculate the difference between the measurement result and the allowable value and to apply feedback control to the position adjustment, because the positional deviation of the organic birefringent film 101 can be suppressed in a short time.

[Optical pickup]
Next, a configuration example of an optical pickup using the polarization separation element manufactured by the above-described method for manufacturing a polarization separation element will be described. FIG. 11 is an explanatory diagram showing an example of the configuration of this optical pickup.

  That is, in this optical pickup 201 for DVD, after the S-polarized light having a wavelength of 680 nm emitted from the laser diode 202 passes through the polarization separation element 1, the collimator lens 203, the λ / 4 wavelength plate 204, and the objective lens 205. The reflected light from the recording pit of the DVD 206 is linearly polarized by the λ / 4 wavelength plate 204 and then diffracted by the polarization separation element 1 and guided to the photodiode 207 by a known means. Focus detection, track detection, and signal detection are performed.

  When an information signal was reproduced from a DVD-ROM using the optical pickup 201 of this example, a signal output equivalent to that of a conventional DVD optical pickup combining a beam splitter with a prism attached and a λ / 4 wavelength plate is obtained. It can be confirmed that the optical pickup 201 of this example has the same reproduction characteristics as those of the conventional optical pickup. Further, in the pickup 201 of this example, since the polarization separation element 1 is smaller than the beam splitter to which the prism is bonded, the entire apparatus can be made smaller than the conventional optical pickup.

[Adhesion device 1]
An example of an adhesion apparatus used for the operation of adhering the organic birefringent film 101, which is suitable for use in the above-described method for manufacturing a polarization separation element, will be described. FIG. 12 is an explanatory diagram of this bonding apparatus.

  The bonding apparatus 301 is driven by a rotation device (not shown) including a spin table 111 that holds the transparent substrate 105, a stepping motor that rotates the spin table 111, and the robot arm 307, and the transparent substrate 105 is UV-cured. A coating device 302 composed of a dispenser 108 for applying a mold adhesive 109 and two organic arm refraction films 101 on which a periodic mask pattern 107 that transmits ultraviolet rays is formed by two adsorption arms 303 are held on a transparent substrate. 105, a placement device 304 that is placed on the surface opposite to the surface on which the mask pattern 107 is formed on the ultraviolet curable adhesive 109 applied on the surface 105, an ultraviolet curable adhesive 109, and an organic composite. A rinsing device 305 for dropping an organic solvent that does not dissolve the refractive film 101 onto the transparent substrate 105, and the transparent substrate 1 And a ultraviolet irradiation device 306 consisting of a high-pressure mercury lamp or a metal halide lamp for irradiating ultraviolet rays to 5.

  Next, the procedure for bonding the organic birefringent film 101 using the bonding apparatus 301 of this example will be described. A transparent substrate 105 made of optical glass (for example, BK7 manufactured by Schott) having an orientation flat having a diameter of 100 mm and a thickness of 1.0 mm is placed on the spin table 111 and fixed to the spin table 111 by vacuum suction. Thereafter, the dispenser 108 is moved by the robot arm 307 to the central portion of the transparent substrate 105 and the spin table 111 is rotated at 50 rpm, and the acrylic ultraviolet ray having a refractive index of 1.52 is used by using the dispenser 108 at the central portion of the transparent substrate 105. 4 g of curable adhesive 109 is dropped.

  Thereafter, the dispenser 108 is returned to the original position, the spin table 111 is rotated at 400 rpm (first rotation), the ultraviolet curable adhesive 109 is spread over the entire surface of the transparent substrate 105, and the rotation of the spin table 111 is stopped. Thereafter, both ends of the organic birefringent film 101 (diameter: 90 mm, thickness: 80 μm) on which a periodic mask pattern that transmits ultraviolet rays is formed by the method of the polarization separating element manufacturing method 1 are placed on the two mounting devices 304. The suction arm 303 is vacuum-sucked and held, the mounting device 304 is moved onto the transparent substrate 105, and the vacuum of the two suction arms 303 is adjusted while the center of the organic birefringent film 101 is substantially aligned with the rotation center of the spin table 111. The adsorption is gradually released, and the organic birefringent film 101 is placed on the surface opposite to the surface on which the mask pattern is formed on the ultraviolet curable adhesive 109.

  Thereafter, the mounting device is returned to the original position, the spin table 111 is rotated at 700 rpm for 10 seconds, and then rotated at 1100 rpm (second rotation), and the ultraviolet curable adhesive 109 is shaken off, and the organic birefringent film 101 is rotated. Flatten the surface.

  In addition, the ultraviolet irradiation device 306 and the rinsing device 305 are moved 5 seconds after the start of the rotation of 1100 rpm, and the first ultraviolet ray is irradiated from the organic birefringent film 101 side in a state where the spin table 111 is rotated at 1100 rpm. While the curing agent 109 is semi-cured, an organic solvent (in this example, using isopropyl alcohol) that dissolves the ultraviolet curable adhesive 109 and does not dissolve the organic birefringent film 101 is dropped onto the end of the transparent substrate 105 to surround the substrate. Part of the UV curable adhesive 109 is removed. Thereafter, the rotation of the spin table 111 is stopped, and the rinse mechanism is returned to the original position. Then, the ultraviolet curable adhesive 109 is completely cured by irradiating the second ultraviolet ray from the organic birefringent film 101 side using the ultraviolet irradiation mechanism. After the ultraviolet irradiation is completed, the ultraviolet irradiation mechanism is returned to the original position, the vacuum adsorption of the spin table 111 is released, and the organic birefringent film 101 is bonded. The transparent substrate 105 is taken out.

  As described above, when the bonding apparatus 301 of this example is used, since the polarization separating element manufacturing method 3 can be performed, the organic birefringent film 101 can be prevented from protruding from the transparent substrate 105.

  Further, even if the organic birefringent film 101 after the bonding is slightly displaced during the second rotation, the organic birefringent film 101 transmits ultraviolet rays in parallel to one specific direction (that is, to the slow axis) out of the two in-plane directions. Since the periodic mask pattern is formed, the diffraction grating 112 can be aligned in one specific direction (that is, on the slow axis) of the two in-plane directions. As a result, a predetermined diffraction efficiency can be obtained.

  Further, after the ultraviolet ray curable adhesive 109 is semi-cured by irradiating the first ultraviolet ray, the ultraviolet curable adhesive 109 is dissolved while the transparent substrate 105 is rotated, and the organic birefringent film 101 is not dissolved. The adhesive remains on the periphery of the substrate. As a result, even if the substrate peripheral part is handled by conveyance between apparatuses or in the apparatus, the generation of foreign matter from the peripheral part of the substrate is very small, so that the manufacturing yield of the polarization separation element 1 can be improved.

  In this example, the ultraviolet curable adhesive 109 is semi-cured by the first ultraviolet irradiation. However, when the ultraviolet irradiation energy 109 is increased and the ultraviolet curable adhesive 109 is completely cured by the first ultraviolet irradiation, the polarization is changed. The manufacturing method 2 of a separation element can be implemented.

  In addition, if the first ultraviolet irradiation is not performed during the second rotation, and the ultraviolet irradiation energy is increased after the second rotation is stopped and the ultraviolet curable adhesive 109 is completely cured by the first ultraviolet irradiation, the polarization separation is performed. Element manufacturing method 1 can be carried out.

[Adhesion device 2]
Another example of the bonding apparatus used for the operation of bonding the organic birefringent film 101, which is suitable for use in the above-described method for manufacturing the polarization separation element, will be described. FIG. 13 is an explanatory diagram of this bonding apparatus.

  The bonding apparatus 301 applies a UV curable adhesive 109 to the transparent substrate 105 and a rotating device (not shown) including a spin table 111 that holds the transparent substrate 105, a stepping motor that rotates the spin table 111, and the like. An ultraviolet ray applied on the transparent substrate 105 while holding both ends of the organic birefringent film 101 on which a periodic mask pattern 107 that transmits ultraviolet rays is formed by a coating device 302 including a dispenser 108 and two adsorption arms 303. Position adjustment for correcting the position by sliding the organic birefringent film 101 on the transparent substrate 105 and the mounting device 304 mounted on the surface opposite to the surface on which the mask pattern 107 is formed on the curable adhesive 109. A device 311, a position detection device 312 for reading the distance between the end of the transparent substrate 105 and the end of the organic birefringent film 101, and purple A rinsing device 305 that drops an organic solvent that dissolves the linear curing adhesive 109 and does not dissolve the organic birefringent film 101 onto the transparent substrate 105, and an ultraviolet ray that includes a high-pressure mercury lamp, a metal halide lamp, or the like that irradiates the transparent substrate 105 with ultraviolet rays. The irradiation device 306 is configured.

  The position adjustment device 311 has an adjustment jig 131 at the tip of a biaxial arm 313 that can move in the X and Y directions. The adjustment jig 131 pushes the organic birefringent film 101 with the adjustment jig and slides on the transparent substrate 105. The position detection device 312 includes a CCD camera with a zoom lens whose magnification can be varied from 4 to 50 times, and an image processing device capable of measuring the length between two points from this captured image.

  Next, the procedure for bonding the organic birefringent film 101 using the bonding apparatus 301 of this example will be described. A transparent substrate 105 made of optical glass having a diameter of 165 mm, a thickness of 1.0 mm, and an orientation flat with a thickness of 54 mm (for example, BK7 from Schott) is placed on the spin table 111 and fixed to the spin table 111 by vacuum suction. Thereafter, the dispenser 108 is moved by the robot arm 307 to the central portion of the transparent substrate 105 and the spin table 111 is rotated at 20 rpm, and the epoxy ultraviolet ray having a refractive index of 1.56 is used by using the dispenser 108 at the central portion of the transparent substrate 105. 10 g of curable adhesive 109 is dropped.

  Thereafter, the dispenser 108 is returned to the original position, the spin table 111 is rotated at 300 rpm (first rotation), the ultraviolet curable adhesive 109 is spread over the entire surface of the transparent substrate 105, and the rotation of the spin table 111 is stopped. Thereafter, both ends of the organic birefringent film 101 (having a diameter of 155 mm and a thickness of 80 μm) on which the periodic mask pattern 107 that transmits ultraviolet rays is formed by the method of manufacturing method 4 of the polarized light separating element are placed on the two ends of the mounting device 304. The suction arm 303 is vacuum-sucked and held, the mounting device 304 is moved onto the transparent substrate 105, and the vacuum of the two suction arms 303 is adjusted while the center of the organic birefringent film 101 is substantially aligned with the rotation center of the spin table 111. The adsorption is gradually released, and the organic birefringent film 101 is placed on the surface opposite to the surface on which the mask pattern 107 is formed on the ultraviolet curable adhesive 109.

  Thereafter, the mounting device 304 is returned to the original position, the spin table 111 is rotated at 1100 rpm (second rotation), the ultraviolet curable adhesive 109 is shaken off, and the surface of the organic birefringent film 101 is flattened. Thereafter, the rotation of the spin table 111 is stopped, the biaxial arm 313 is moved, the adjustment jig 131 is abutted against the side surface of the organic birefringent film 101, and the biaxial arm 313 is moved to XY according to the positional deviation of the organic birefringent film 101. The organic birefringent film 101 is pushed in the direction by the adjusting jig 131, and the organic birefringent film 101 is slid on the transparent substrate 105 (sliding) to correct the position of the organic birefringent film 101. After the position adjustment is completed, the position adjustment device 311 is returned to the original position. Thereafter, the spin table 111 is rotated at 1100 rpm for 5 seconds (second rotation), and the rotation of the spin table 111 is stopped. Thereafter, the position detection device 312 is moved onto the transparent substrate 105, the distance between the end of the transparent substrate 105 and the end of the organic birefringent film 101 is measured in two directions XY, and the end of the transparent substrate 105 and the organic birefringent film are measured. Confirm that the distance to the end of 101 is within the allowable value. If the measured value exceeds the allowable value, the deviation between the allowable value and the actually measured value is calculated, the position detecting device 312 is returned to the original position, the biaxial arm of the position adjusting device 311 is moved, and the adjusting jig 131 is moved. Abutting on the side surface of the organic birefringent film 101, the biaxial arm 313 is moved in the X and Y directions according to the calculated deviation, the organic birefringent film 101 is pushed by the adjusting jig 131, and the organic birefringent film 101 is made transparent. The position is adjusted by sliding on 105. Thereafter, the position adjusting device 311 is returned to the original position, the spin table 111 is again rotated at 1100 rpm for 5 seconds (second rotation), the rotation of the spin table 111 is stopped, and the position detection device 312 is placed on the transparent substrate 105. Is moved again, the distance between the end of the transparent substrate 105 and the end of the organic birefringent film 101 is measured, and the above operation is repeated until the distance falls within an allowable value. Thereafter, the ultraviolet irradiating device 306 and the rinsing device 305 are moved, and the ultraviolet curable adhesive 109 is semi-cured by irradiating the first ultraviolet light from the organic birefringent film 101 side while the rotation of the spin table 111 is stopped. After the first ultraviolet irradiation, the spin table 111 is rotated at 700 rpm (third rotation) to dissolve the ultraviolet curable adhesive 109 and not to dissolve the organic birefringent film 101 (in this example, acetone is used). ) Is dropped onto the edge of the transparent substrate 105 to remove the ultraviolet curable adhesive 109 remaining on the periphery of the substrate 105. Thereafter, the rotation of the spin table 111 is stopped, and the rinse device 305 is returned to the original position. Then, the ultraviolet curable adhesive 109 is completely cured by irradiating the second ultraviolet light from the organic birefringent film 101 side using the ultraviolet irradiation device 306. After the ultraviolet irradiation is completed, the ultraviolet irradiation device 306 is returned to the original position, the vacuum adsorption of the spin table 111 is released, and the transparent substrate 105 to which the organic birefringent film 101 is bonded is taken out.

  As described above, when the bonding apparatus 301 of the present example is used, the polarization separating element manufacturing method 4 can be realized, and thus the protrusion of the organic birefringent film 101 from the transparent substrate 105 can be further prevented.

  In addition, the relative position between the transparent substrate 105 and the organic birefringent film 101 can be within an allowable value, and the frequency of the organic birefringent film 101 protruding from the transparent substrate 105 can be significantly reduced.

  Further, even if the organic birefringent film 101 after bonding is slightly displaced during the third rotation, the organic birefringent film 101 transmits ultraviolet rays in parallel to one specific direction (that is, to the slow axis) out of the two in-plane directions. Since the periodic mask pattern 107 is formed, the diffraction grating 112 can be aligned in one specific direction (that is, on the slow axis) of the two in-plane directions. As a result, a predetermined diffraction efficiency can be obtained.

  In addition, after the ultraviolet ray curable adhesive 109 is semi-cured by irradiating the first ultraviolet ray, the ultraviolet curable adhesive 109 is dissolved while the transparent substrate 105 is rotated, and the organic birefringent film 101 is not dissolved. As a result, no adhesive residue remains on the periphery of the substrate 105. As a result, since the generation of foreign matter from the peripheral portion of the substrate is very small even if the peripheral portion of the substrate is handled by conveyance between apparatuses or in the apparatus, the manufacturing yield of the polarization separation element 1 can be improved.

It is explanatory drawing which shows each process of the manufacturing method 1 of the polarization splitting element which is the best form for implementing this invention. It is explanatory drawing which shows each process of the manufacturing method 1 of a polarization splitting element. It is explanatory drawing which shows each process of the manufacturing method 2 of a polarization splitting element. It is explanatory drawing which shows each process of the manufacturing method 2 of a polarization splitting element. It is explanatory drawing which shows each process of the manufacturing method 3 of a polarization splitting element. It is explanatory drawing which shows each process of the manufacturing method 3 of a polarization splitting element. It is explanatory drawing which shows each process of the manufacturing method 4 of a polarization splitting element. It is explanatory drawing which shows each process of the manufacturing method 4 of a polarization splitting element. It is explanatory drawing of the (j) process of the manufacturing method 4 of a polarization splitting element. The substrate to which the organic birefringent film is bonded by the steps (a) to (r) of the manufacturing method 4 of the polarized light separating element is cut using a dicing saw, the cross section is observed with a 200 times metal microscope, and the diameter direction of the substrate It is a graph which shows the result of having measured the adhesive layer thickness in. It is explanatory drawing of the optical pick-up using the polarization separation element manufactured with the manufacturing methods 1-4 of the polarization separation element. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory view of a bonding apparatus 1 which is the best mode for carrying out the present invention. It is explanatory drawing of the bonding apparatus 2. FIG. It is explanatory drawing explaining the manufacturing method of the bonded optical disk by a spinner method. It is explanatory drawing explaining the subject of this invention. It is explanatory drawing explaining the subject of this invention. It is explanatory drawing explaining the subject of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polarization separation element 101 Organic birefringent film 105 Transparent substrate 107 Mask pattern 109 UV curable adhesive 112 Diffraction grating 111 Spin table 301 Adhesive device 302 Coating device 304 Placement device 305 Rinse device 306 Ultraviolet irradiation device 311 Position adjustment device 312 Position Detection device

Claims (3)

A mask pattern forming step of forming a periodic mask pattern that transmits ultraviolet light on one surface of an organic birefringent film having a different refractive index with respect to different vibration surfaces of incident light, and the mask pattern of the organic birefringent film Bonding the organic birefringent film to a transparent substrate on the surface opposite to the formed surface, and etching the surface of the organic birefringent film using the mask pattern to form a diffraction grating with periodic irregularities And a method of manufacturing a polarization separation element including a diffraction grating forming step,
In the bonding step,
Applying a first rotation which is a rotation in the substrate surface direction to the transparent substrate to apply an ultraviolet curable adhesive to the entire surface of the transparent substrate,
Then, the organic birefringent film is placed on the surface opposite to the surface on which the mask pattern is formed on the ultraviolet curable adhesive,
Then, a second rotation which is a rotation in the substrate surface direction is applied to the transparent substrate to flatten the surface of the organic birefringent film, the ultraviolet curable adhesive is dissolved during the second rotation, and Dropping an organic solvent that does not dissolve the organic birefringent film to remove the UV curable adhesive around the transparent substrate,
Thereafter, a process for irradiating the transparent substrate with a first ultraviolet ray to cure the ultraviolet curable adhesive is performed. In the mask pattern forming step, the mask pattern is
_2. The polarization separation according to claim 1, wherein the polarization separation is made of at least one material selected from the group consisting of SiO ₂ , Si ₃ N ₄ , SiON, In ₂ O ₃ , and ITO (Indium thin Oxide). Device manufacturing method. 3. The method of manufacturing a polarization separation element according to claim 1, wherein at least one of isopropyl alcohol and acetone is used as the organic solvent in the adhesion step.

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