JP2010276940A - Glass substrate bonding method and glass bonded body - Google Patents

Abstract

An object of the present invention is to directly join glass substrates of the order in which surface roughness can be easily obtained.
[Solution]
When the first prism 21 and the second prism 22 are directly joined without using an adhesive, first, glass whose principal component is the same as the second prism 22 joined to the first prism 21 on the inclined surface 21a of the first prism 21. A thin film 24 is formed. Then, after the glass thin film 24 and the side surface 22a of the second prism 22 are brought into close contact with each other with distilled water 31 interposed therebetween, the distilled water 31 is evaporated and the first prism 21 and the second prism 22 are connected. Integrate.
[Selection] Figure 2

Description

  The present invention relates to a glass bonded body in which a glass substrate is bonded through an optical thin film and a bonding method thereof, and more specifically, a glass bonded body in which a glass substrate is bonded without using an adhesive and the bonding thereof. Regarding the method.

  Optical elements bonded with a glass substrate such as a polarizing beam splitter, a polarization conversion element, a dichroic prism, and a cemented lens are used in various products. Thus, when a glass substrate is bonded to produce a bonded optical element, the glass substrate can be bonded thinly, firmly, and inexpensively. For example, an adhesive such as a photo-curable adhesive that is cured by ultraviolet rays is used. Used.

  In recent years, projectors and optical disks using blue light have been widely used, but the above-described junction type optical elements are also used in such optical devices. However, it is known that the adhesive used for bonding the glass base material is deteriorated over time when it is irradiated with blue light close to ultraviolet light or used in a high illuminance and high temperature environment. . In particular, in the optical system of a projector used in a high illuminance and high temperature environment, or in an optical apparatus such as an optical pickup that supports blue light, the optical performance of the junction type optical element is deteriorated due to the deterioration of the adhesive. It may become a bottleneck that determines the overall lifespan. For this reason, the junction type optical element is required to have durability that does not easily deteriorate due to high illuminance, high temperature environment and ultraviolet rays.

  For this reason, in recent years, a method of directly bonding glass substrates such as a glass substrate, a prism, and a lens without using an adhesive, so-called optical contact is known (Patent Document 1).

  Optical contact is a method in which glass substrates are bonded to each other by interatomic and intermolecular interactions by bringing bonded surfaces that have been polished extremely precisely into contact with each other. For this reason, in order to join the glass substrates by optical contact, the arithmetic surface roughness (Ra, hereinafter simply referred to as “surface roughness”) of the joining surface should be at most on the order of 1 to 2 nm. It is said that the surface roughness is substantially in the order of angstroms.

  Similar to the optical contact, in the semiconductor field, a technique for directly bonding a semiconductor substrate without using an adhesive is known. For example, a semiconductor substrate is directly bonded by forming a thin oxide film and bringing the oxide films into contact with bonding surfaces subjected to a surface treatment for imparting a hydroxyl group and performing a heat treatment. Thus, even when directly bonding semiconductor substrates, the surface roughness of the bonding surface is at least on the order of 1 to 2 nm, and if the bonding surface is not substantially less than this, the bonding surface should be directly bonded. Is known to be difficult.

JP 2004-279495 A

  The surface roughness of the bonding surface required when directly bonding the glass substrates by optical contact is not impossible to achieve, but it is not an orderly obtained surface roughness. For example, a mirror polishing process is known as a polishing process that finishes the surface of a glass substrate or the like particularly smoothly, but the surface roughness obtained by a general mirror polishing process is about 5 to 10 nm even if it is a precise one. ing. Compared with this, it can be seen that the optical contact is required to be polished by an order of magnitude more precise than mirror polishing.

  For this reason, it is difficult to manufacture a bonded optical element in which a glass substrate is directly bonded with an optical contact, and there is a problem that even if it can be manufactured, it becomes expensive. In particular, it is difficult to use a junction type optical element using an optical contact in an optical apparatus such as a projector or an optical pickup that is remarkably widespread and is desired to be mass-produced at a low cost.

  The present invention has been made in view of the above-described problems, and an object thereof is to provide a glass substrate bonding method for directly bonding glass substrates of the order in which the surface roughness of the bonding surface can be easily obtained. . It is another object of the present invention to provide a bonded optical element obtained by directly bonding a glass substrate so that it can be stably manufactured and provided at a low cost.

  The glass substrate bonding method of the present invention includes a film forming step of forming a thin film having the same main component as the second glass substrate bonded to the first glass substrate on the bonding surface of the first glass substrate; The first glass substrate and the second glass substrate are integrated by evaporating the water after adhering the thin film and the bonding surface of the second glass substrate with water interposed therebetween. A glass substrate bonding method comprising: a bonding step of:

  Further, the evaporation of the water in the joining step is performed by heating at a predetermined temperature not lower than the normal temperature and lower than the boiling point of water in the atmosphere.

  Moreover, after the said joining process, the joining reinforcement | strengthening process which heats the joined body of a said 1st glass base material and a said 2nd glass base material in a vacuum is characterized by the above-mentioned.

  Further, an optical thin film having a predetermined optical function is formed in advance on the bonding surface of the first glass substrate, and the film forming step is performed on the surface of the optical thin film.

  Further, the film forming step is performed after polishing the surface of the optical thin film.

  In addition, a plurality of the thin films are continuously provided in a layer shape.

  The thin film formed in the film forming step is characterized in that a change in refractive index with respect to d-line is 0.5% or less with respect to a temperature change between room temperature and 100 degrees.

  The thin film is made of silicon dioxide.

  The glass joined body of the present invention is a joined body of a first glass substrate and a second glass substrate, and the second glass is formed on a joint surface of the first glass substrate with the second glass substrate. A thin film having the same main component as that of the base material is formed, and by evaporating water interposed between the thin film and the bonding surface of the second glass substrate, the bonding surface of the second glass substrate is It is bonded to the bonding surface of the first glass substrate through a thin film.

  According to the glass substrate bonding method of the present invention, a glass substrate of the order in which the surface roughness of the bonding surface can be easily obtained can be directly bonded. Moreover, by using this glass base material joining method, the joining type optical element which directly joined the glass base material can be manufactured stably, and can be provided at low cost.

It is explanatory drawing which shows the structure of a beam splitter. It is explanatory drawing which shows the manufacturing process of a beam splitter. It is explanatory drawing which shows a mode that the surface of a semipermeable membrane is grind | polished. It is explanatory drawing which shows the example which provides multiple glass thin films. It is explanatory drawing which shows a mode that a beam splitter is manufactured from a glass substrate. It is explanatory drawing which shows a mode that a beam splitter is manufactured from a glass substrate.

  The optical pickup 11 is an optical system that reads and writes data by making light incident on the optical disk 12 for blue light, and includes a light source 16, a beam splitter 17 (glass bonded body), a power monitor 18, and the like.

  The optical disk 12 reads and writes data using blue light having a wavelength of around 405 nm. The light source 16 is a light source that generates blue light to be incident on the optical disc 12, and includes a laser diode, a collimating lens, a half-wave plate, a diffraction grating, and the like. The laser diode emits blue light having a wavelength of around 405 nm. The blue light emitted from the laser diode is adjusted to parallel light by the collimator lens and adjusted to S-polarized light by passing through the half-wave plate. Further, it is branched by the diffraction grating into a main beam used for reading and writing data and two sub beams used for tracking and the like, and enters the beam splitter 17.

  The beam splitter 17 is an optical element that branches blue light incident from the light source 16 in two directions, ie, the direction of the optical disk 12 and the direction of the power monitor 18, and includes a first prism 21 (first glass substrate) and a second prism. 22 (second glass substrate), a semipermeable membrane 23, and a glass thin film 24.

  The first prism 21 is a right-angled triangular prism made of borosilicate glass in which boric acid is mixed with silicon dioxide, and is joined to the second prism 22 on the hypotenuse via the semipermeable membrane 23 and the glass thin film 24. . Similar to the first prism 21, the second prism 22 is a right-angled triangular prism made of borosilicate glass, and a semipermeable membrane is formed on a side surface 22a (joint surface) on one side of two sides forming a right angle. The hypotenuse of the first prism 21 is joined via the glass 23 and the glass thin film 24. The surfaces of the first prism 21 and the second prism 22 are smooth surfaces with a surface roughness Ra of about 10 nm. Further, no adhesive is used to join the first prism 21 and the second prism 22, and the glass thin film 24 provided on the surface of the first prism 21 and the side surface 22 a of the second prism 22 are brought into direct contact with each other. The first prism 21 and the second prism 22 are directly joined.

  The semipermeable membrane 23 is configured by laminating a plurality of dielectric thin films, and is provided on the inclined surface 21 a (bonding surface) of the first prism 21. S-polarized blue light from the light source 16 enters the semipermeable membrane 23 through the first prism 21. At this time, the semi-transmissive film 23 reflects about 70% of the incident blue light to the optical disk 12 side and transmits the remaining 30% to the second prism 22 side. Here, only the S-polarized light is incident on the semi-permeable film 23, but the semi-permeable film 23 transmits substantially 100% of the P-polarized light regardless of the wavelength.

  The glass thin film 24 is a thin film having a thickness of 0.2 μm made of the same glass material as that of the second prism 22 that is directly bonded, and is formed on the semipermeable membrane 23. Here, as described above, since the second prism 22 is made of borosilicate glass, the glass thin film 24 is made of silicon dioxide. Further, when the film is formed, the surface of the glass thin film 24 is a smooth surface having a surface roughness Ra of about 10 nm, and the beam splitter 17 is formed by joining the first prism 21 and the second prism 22. When doing so, the surface of the glass thin film 24 comes into direct contact with and is bonded to the surface of the second prism 22 without using an adhesive.

  Furthermore, the glass thin film 24 is a high-density glass thin film whose refractive index hardly changes with respect to a temperature change in the range from room temperature to about 100 degrees, and the temperature is in the range from room temperature (15 to 25 degrees) to 100 degrees. When changed, the change in the refractive index Nd with respect to the d-line (589.3 nm) is suppressed to a range of 0.02 to 0.1%.

  The blue light transmitted through the semi-transmissive film 23 and incident on the second prism 22 is totally reflected by the side surface 22b on the side facing the first prism 21 out of the two sides forming the right angle of the second prism 22, and the power monitor 18 is incident.

  In this way, the beam splitter 17 is provided with the glass thin film 24 on the surface on the first prism 21 side, and the surface of the glass thin film 24 and the surface of the second prism 22 are brought into contact with each other to directly connect the first prism 21 and the second prism 22. Join. Therefore, the beam splitter 17 does not use an adhesive to join the first prism 21 and the second prism 22. For this reason, although blue light is incident on the beam splitter 17, the blue light does not cause deterioration over time in the beam splitter 17. Similarly, since the first prism 21 and the second prism 22 are directly joined, even when the beam splitter 17 is used in a high illumination environment, this does not cause deterioration of the beam splitter 17 over time.

  The power monitor 18 photoelectrically converts the blue light incident from the beam splitter 17 and measures the amount of light. Based on the amount of blue light measured by the power monitor 18 in this way, the amount of blue light emitted from the light source 16 is adjusted so that the amount of blue light incident on the optical disk 12 is appropriate for reading and writing data. Is done.

  Since the optical pickup 11 configured as described above uses the beam splitter 17 in which the first prism 21 and the second prism 22 are directly joined without using an adhesive, the time-lapse due to the incidence of blue light. No significant degradation occurs. Further, the beam splitter 17 directly joins the glass thin film 24 having a surface roughness Ra of the order of 10 nm and the second prism 22 by a joining method described later. Such a surface having a surface roughness Ra of the order of 10 nm can be easily obtained by a general precision polishing process such as film formation by ion plating or mirror polishing process. For this reason, the beam splitter 17 can be manufactured stably and inexpensively.

  The beam splitter 17 is manufactured according to the procedure shown in FIGS. First, as shown in FIG. 2A, first, a semipermeable membrane 23 is formed on the slope 21a of the first prism 21. At this time, the surface of the first prism 21 is polished, and all the surfaces including the inclined surface 21a on which the semipermeable membrane 23 is formed are smoothly finished to the order of the surface roughness Ra of 10 nm.

  Next, as shown in FIG. 2B, a high-density glass thin film 24 is formed on the semipermeable membrane 23 (film formation step). The glass thin film 24 is formed by ion plating. The surface of the glass thin film 24 is a smooth surface having a surface roughness Ra on the order of 10 nm at the stage of film formation. Further, the glass thin film 24 formed here is formed to a thickness of 0.2 μm, and the change in the refractive index Nd depending on the temperature between room temperature and 100 degrees as described above is 0.02 to 0%. The film is formed at a high density so as to be suppressed to about 1%. Thereby, as described later, distilled water can be spread on the glass thin film 24 without being dissipated.

  Then, as shown in FIG. 2C, the first prism 21 and the second prism 22 are joined (joining step). At this time, distilled water 31 is thinly applied on the slope 21 a (on the glass thin film 24) of the first prism 21, and the glass thin film 24 and the side surface 22 a of the second prism 24 are brought into close contact with each other through the distilled water 31. The first prism 21 and the second prism 22 thus brought into close contact with each other are heated to 85 degrees in the atmosphere, and this state is maintained for 4 hours, whereby the distilled water 31 between the first prism 21 and the second prism 22 is gradually added. Evaporate. 2D, the distilled water 31 between the first prism 21 and the second prism 22 evaporates, and the surface of the glass thin film 24 (first prism 21) and the side surface 22a of the second prism 22 are obtained. Directly contact each other, the first prism 21 and the second prism 22 are directly joined to form an integrated beam splitter 17.

  The beam splitter 17 thus bonded is firmly bonded to such an extent that the bonding does not naturally peel off due to changes in the environment such as temperature and humidity. The bonding strength of the beam splitter 17 is an ultraviolet curable adhesive. It is weak compared to the strength of bonding with adhesives such as. For this reason, the 1st prism 21 and the 2nd prism 22 joined in air | atmosphere are heated at 350 degree | times for 4 hours in a vacuum (joining reinforcement | strengthening process). Thereby, the bonding strength between the first prism 21 and the second prism 22 is enhanced.

  When the beam splitter 17 is manufactured as described above, the first prism 21 and the second prism 22 can be directly joined without using an adhesive. Furthermore, if the beam splitter 17 is manufactured according to the above-described procedure, even a surface that can be easily obtained by film formation or polishing with a surface roughness Ra of about 10 nm can be directly bonded. For this reason, the beam splitter 17 can be manufactured stably and inexpensively with a high yield.

  In the above-described embodiment, after the semipermeable membrane 23 is formed on the inclined surface 21a of the first prism 21, the surface of the semipermeable membrane 23 is not polished and the glass thin film 24 is formed thereon. However, it is preferable to polish the surface of the semipermeable membrane 23 before the glass thin film 24 is formed.

  As shown in FIG. 3A, when the semipermeable membrane 23 is formed on the inclined surface 21a of the first prism 21, depending on the form of the film formation, a local convex portion 36 (hereinafter, referred to as a semi-permeable membrane 23). A convex portion) may occur. For example, the semipermeable membrane 23 is formed by ion plating as described above, but when the material of the semipermeable membrane 23 forms a cluster and lands on the first prism 21, a convex portion using this as a nucleus. 36 occurs locally. When the glass thin film 24 is formed on the semipermeable membrane 23 with the projections 36 remaining, if the glass thin film 24 is thinner than the size of the projections 36, the glass thin film 24 has the same projections. Appears. For this reason, generally, the surface roughness Ra of the glass thin film 24 is about 10 nm, and even if the beam splitter 17 is manufactured by the above-described procedure, the first prism 21 and the second prism 22 are not joined. Even if they are joined, they become extremely weak joints. For this reason, as shown in FIG. 3B, after forming the semipermeable membrane 23 on the slope 21a of the first prism 21, the surface of the semipermeable membrane 23 is polished to remove the convex portion 36 (polishing step). After that, it is preferable to form the glass thin film 24 on the surface of the semipermeable membrane 23 without the convex portion 36.

  When polishing the surface of the semipermeable membrane 23 in order to remove the convex portions 36, a sponge made of melamine resin, fine frosted glass, or the like can be suitably used as a file. In particular, these files preferably have a fineness equivalent to # 2000.

  In the above-described embodiment, the example in which the glass thin film 24 is formed on the semipermeable membrane 23 has been described. However, when the glass thin film 24 is formed in this manner, the glass thin film 24 is formed as shown in FIG. A partial hole 37 (hereinafter referred to as a pinhole) may occur. If there is a pinhole 37 in the glass thin film 24, the distilled water 31 is dissipated from the pinhole 37 when the distilled water 31 is spread on the glass thin film 24. When the distilled water 31 is thus dissipated, when the first prism 21 and the second prism 22 are joined, the first prism 21 (glass thin film 24) and the second prism 22 come into direct contact without passing through the distilled water 31. Therefore, when the first prism 21 and the second prism 22 are to be joined by the procedure described in the above-described embodiment, the first prism 21 and the second prism 22 are dependent on the position and distribution of the pinholes 37. May not be joined. For this reason, it is preferable to form a plurality of glass thin films on the slope 21 a of the first prism 21.

  For example, as shown in FIG. 4B, two glass thin films are formed on the slope 21a of the first prism 21 in the order of the first glass thin film 42a and the second glass thin film 42b from the first prism 21 side. . The first glass thin film 42a and the second glass thin film 42b are made of a glass material having the same component as the glass thin film 24 described above, and each has a thickness half that of the glass thin film 24 (0.1 μm). In this case, when the pinhole 37 opens in the first glass thin film 42a, the second glass thin film 42b is formed thereon, so that the pinhole 37 of the first glass thin film 42a is closed. For this reason, the distilled water 31 is spread on the first prism 21 (second glass thin film 42b) without the distilled water 31 being dissipated from the pinhole 37, and the first prism 21 and the second prism 21 are separated by the procedure of the above-described embodiment. The prism 22 can be reliably directly joined.

  Even when a pinhole is opened in the second glass thin film 42b, the pinhole in the second glass thin film 42b is shallower and smaller than the pinhole 37 opened in the single layer glass thin film 24. Become a thing. Therefore, when the distilled water 31 is stretched on the first prism 21, the dissipation of the distilled water 31 from the pinhole 37 opened in the second glass thin film 42b can be suppressed to be small. For this reason, by forming the glass thin film formed on the first prism 21 into two layers, the first prism 21 and the second prism 22 can be more reliably compared with the case where the single glass thin film 24 is provided. Can be directly joined.

  Here, an example in which two glass thin films of the first glass thin film 42a and the second glass thin film 42b are provided in place of the single glass thin film 24 has been described. However, the inclined surface 21a of the first prism 21 has 3 A plurality of the above glass thin films may be continuously provided in layers. However, when a plurality of glass thin films are provided on the inclined surface 21a of the first prism 21, the number of film forming steps increases according to the number of layers of the glass thin film, and the productivity decreases. For this reason, when providing multiple layers of glass thin films on the slope 21a of the first prism 21, it is particularly preferable to provide two layers of glass thin films as in the above example.

  In the above-described embodiment, the semi-transmissive film 23 and the glass thin film 24 (glass thin films 42a and 42b) are formed on the first prism 21 formed in a triangular prism shape in advance, and this is formed in a triangular prism shape in advance. Although an example in which the beam splitter 17 is manufactured by being joined to the two prisms 22 has been described, the beam splitter 17 may be manufactured from a glass substrate.

  In this case, first, a thin first glass substrate 46 (first glass material) to be the first prism 21 and a thick second glass substrate 47 (second glass material) to be the second prism 22 are prepared. At this time, the surfaces of the glass substrates 46 and 47 are assumed to be polished smoothly to a surface roughness Ra of about 10 nm. When manufacturing the beam splitter 17 from these glass substrates 46 and 47, first, as shown in FIG. 5A, the semipermeable membrane 23 is formed on the surface of the first glass substrate 46. Next, as shown in FIG. 5B, a glass thin film 24 is formed on the semipermeable membrane 23 (film formation step).

  And as shown in FIG.5 (C), the distilled water 31 is spread on the surface of the 1st glass substrate 46, this distilled water 31 is interposed between the glass thin film 24 and the 2nd glass substrate 47, The first glass substrate 46 and the second glass substrate 47 are brought into close contact with each other. Then, it heats to 85 degree | times in air | atmosphere, The distilled water 31 is evaporated gradually by maintaining this state for 4 hours. As shown in FIG. 5D, when the glass thin film 24 and the second glass substrate 47 are in direct contact with each other, the first glass substrate 46 and the second glass substrate 47 are directly bonded (bonding). Process).

  The bonded body 51 of the first glass substrate 46 and the second glass substrate 47 directly bonded in this way is heated at 350 ° C. for 4 hours in a vacuum, and the bonding strength is strengthened (bonding strengthening step).

  Thereafter, as shown in FIG. 6A, the joined body 51 is cut at intervals of the width of the beam splitter 17 to obtain a prismatic member 51a that is long in the depth direction of FIG. 6A. Then, as shown in FIG. 6 (B), the corners 52a to 52c of each prismatic member 51a are removed by polishing and adjusted to the shape of the beam splitter 17, and then cut into predetermined lengths in the longitudinal direction. Thus, the beam splitter 17 is obtained.

  Thus, when the beam splitter 17 is manufactured from the glass substrates 46 and 47, a plurality of beam splitters 17 can be manufactured simultaneously, and the productivity is good. In addition, it is more stable in shape when the first glass substrate 46 and the second glass substrate 47 are bonded as described above than when the first prism 21 and the second prism 22 formed in a triangular prism shape in advance are bonded. Because of this, it can be easily joined directly.

  Further, when the beam splitter 17 is manufactured from the glass substrates 46 and 47, the area of the surface to be joined is larger than when the prisms 21 and 22 are joined, so that it is less susceptible to pinholes generated in the glass thin film 24. . For this reason, when the beam splitter 17 is manufactured from the glass substrates 46 and 47, the beam splitter 17 can be manufactured more stably and efficiently.

  Even in the case of manufacturing the beam splitter 17 from the glass substrates 46 and 47 in this way, it is preferable to provide the glass thin film 24 after removing the convex portions 36 of the semipermeable membrane 23 by polishing, as described above. It is preferable to form a plurality of thin glass films on the film 23.

  Further, here, an example has been described in which after removing the corners 52a to 52c of the prismatic member 51a, the beam splitter 17 is obtained by cutting it into the length of the beam splitter 17 in the longitudinal direction. Alternatively, the beam splitter 17 may be obtained by cutting the corner after the beam splitter 17 is cut.

  In the above-described embodiment, the example in which the optical thin film is not provided on the outer peripheral surface of the beam splitter 17 and the surfaces of the prisms 21 and 22 are exposed has been described. In particular, an antireflection film is preferably provided on the surface through which blue light passes. In addition, the antireflection film is usually formed at a high temperature (for example, about 350 degrees) in order to improve the adhesion to the glass materials such as the prisms 21 and 22. However, the antireflection film is described in the above embodiment. According to the bonding method, since the bonded portions of the prisms 21 and 22 and the glass substrates 46 and 47 are not peeled off or deteriorated even under such a high temperature environment, antireflection is performed after the prisms 21 and 22 and the glass substrates 46 and 47 are bonded. A film may be formed. This is not limited to the antireflection film, and the same applies when an optical thin film that needs to be formed in a high temperature environment is provided on the outer peripheral surface of the beam splitter 17.

  In the above-described embodiment, the example of the beam splitter 17 in which the first prism 21 and the second prism 22 are bonded with the semipermeable membrane 23 interposed therebetween has been described. However, the bonding method described in the above-described embodiment is a semi-transparent method. Even when a glass material such as a prism or a glass substrate is directly bonded without interposing an optical thin film such as the permeable film 23, the bonding method described in the above embodiment can be suitably used.

  Furthermore, in the above-described embodiment, an example in which the glass thin film 24 (glass thin films 42a and 42b) is provided separately from the semipermeable membrane 23 has been described, but an optical thin film (semipermeable membrane 23) is interposed as in the above-described embodiment. When the glass material is bonded as described above, if the uppermost layer of the optical thin film (the layer closest to the glass material to be bonded and is in direct contact) is made of the same material as the glass thin film 24, the glass thin film 24 is again formed thereon. It is not necessary to provide the glass thin film 24, and this uppermost layer may be used as the glass thin film 24.

  In the above-described embodiment, the example in which the glass thin films 24, 42a, and 42b are formed by ion plating has been described. However, the method of forming the glass thin films 24, 42a, and 42b is not limited to ion plating, and the surface roughening is performed. If the glass thin films 24, 42a, and 42b having a high density can be formed to such an extent that the distilled water 31 does not dissipate to about 10 nm or less, this can be performed by other known film forming methods such as sputtering and CVD. You may make it provide. In the above-described embodiment, the range of the amount of change in the refractive index Nd with respect to the temperature change from room temperature to 100 degrees has been described as an example of the density of the glass thin films 24, 42a, and 42b. Is about 10 nm or less, and the amount of change in the refractive index Nd may exceed the aforementioned range as long as the distilled water 31 does not dissipate. For example, in the above-described embodiment, the glass thin films 24, 42a, and 42b suppress the change amount of the refractive index Nd to about 0.02% to 0.1% with respect to the temperature change from room temperature to 100 degrees. However, the amount of change in the refractive index Nd of the glass thin films 24, 42a, 42b within this temperature range is preferably 0.5% or less, and 0.2% or less. More preferably, it is particularly preferably 0.1% or less as in the above-described embodiment.

  In the above-described embodiment, an example of the thickness of the glass thin films 24, 42a, and 42b has been described. However, the thickness of the glass thin films 24, 42a, and 42b may be arbitrarily determined. Moreover, although the example which provides the glass thin film 42a, 42b in the half thickness of the glass thin film 24 was demonstrated in the above-mentioned embodiment, not only this but also when providing a several glass thin film, each glass thin film of The thickness may be arbitrarily determined.

  In the above-described embodiment, the specific examples of environment, temperature, and time at the time of joining the prisms 21 and 22 (glass substrates 46 and 47) have been described. However, the prisms 21 and 22 (glass substrates 46 and 47) are described. If the distilled water 31 intervening between them can be gradually evaporated, conditions such as environment, temperature, and time at the time of joining can be arbitrarily determined. Similarly, in the above-described embodiment, the specific examples of environment, temperature, and time when strengthening the bonding strength of the prisms 21 and 22 (glass substrates 46 and 47) have been described. If the strength can be enhanced, conditions such as the environment, temperature, and time of this process can be arbitrarily determined.

  For example, in the above-described embodiment, when the prisms 21 and 22 are joined, the example in which the distilled water 31 is evaporated by heating to 85 degrees has been described. However, the prisms 21 and 22 that are brought into contact with each other via the distilled water 31 are described. The heating temperature is not limited to this, and it may be heated to an arbitrary temperature that is not lower than normal temperature and lower than the boiling point of distilled water 31. Further, in the above-described embodiment, when the bonding strength is strengthened, the example of heating to 350 degrees in vacuum has been described. However, the heating temperature when strengthening the bonding is higher than the normal temperature, and the prism or the glass substrate. The glass thin film may be heated at an arbitrary temperature within a temperature range lower than both the glass transition point of the glass thin film and the melting point of the material used for the semipermeable membrane 23.

  In the above-described embodiment, when the prisms 21 and 22 and the glass substrates 46 and 47 are brought into close contact with each other via the distilled water 31, the weights of these members are between the prisms 21 and 22 and between the glass substrates 46 and 47. In the above example, the distilled water 31 is simply evaporated and bonded to each other without applying pressure. However, when the distilled water 31 is evaporated and the prisms 21 and 22 and the glass substrates 46 and 47 are bonded, These may be held while being pressurized. For example, since the glass substrate 46 may be warped by providing the glass substrate 46 with the semipermeable membrane 23 or the glass thin film 24, in such a case, the warpage of the glass substrate 46 is reduced in addition to simply contacting. The glass substrate 46 and the glass substrate 47 are preferably brought into close contact with each other while being pressurized.

In the above-described embodiment, the example in which the distilled water 31 is interposed when the prisms 21 and 22 and the glass substrates 46 and 47 are joined has been described. , 42b, the liquid intervening between them is sufficient if water (H ₂ O) is sufficiently contained and can be volatilized, and other components such as alcohols and ions are mixed. May be.

  In the above-described embodiment, the example in which the prisms 21 and 22 and the glass substrates 46 and 47 are made of borosilicate glass has been described. However, the material of the glass base material to be joined such as the prisms 21 and 22 and the glass substrates 46 and 47 is as follows. Not limited to this, any glass material may be used. For example, the prisms 21 and 22 and the glass substrates 46 and 47 do not have to be amorphous, and those made of quartz may be used. Further, the prisms 21 and 22 and the glass substrates 46 and 47 do not need to be made of borosilicate glass, and may be made of other well-known glasses such as soda lime glass containing sodium or calcium, and the purity of silicon dioxide is high. It may be made of quartz glass. Furthermore, for manufacturing the prisms 21 and 22 and the glass substrates 46 and 47, those manufactured by a well-known method according to the composition and the like can be used. Even when a glass substrate made of such an arbitrary material is bonded by the method described in the above embodiment, the glass thin films 24, 42a, and 42b are thin films made of silicon dioxide, which is the main component of the glass substrate. It is preferable. Further, the glass thin films 24, 42a, 42b may be any film containing silicon dioxide as the main component of the glass substrate, and may be a thin film containing impurities of the same component as the glass substrate in direct contact. A thin film containing impurities of a component different from that of the glass substrate in direct contact may be used.

  In the above-described embodiment, an example in which the beam splitter 17 is manufactured has been described. However, the bonding method described in the above-described embodiment is not limited to the shape and application, and other well-known bonding-type optics that bonds glass materials. The present invention can also be suitably applied to elements. In the above-described embodiment, the example in which the surfaces to be directly bonded are flat has been described. However, the shape of the surface to be directly bonded by the bonding method described in the above-described embodiments may be a curved surface. For this reason, the bonding method described in the above embodiment is a well-known bonding type other than the beam splitter 17 such as a PS converter that adjusts the polarization state of transmitted light to one of P-polarized light and S-polarized light, a polarized beam splitter, and a bonded lens. It can be suitably used for an optical element.

11 Optical pickup 17 Beam splitter 21 First prism (glass substrate)
21a Slope (joint surface)
22 Second prism (glass substrate)
22a Side surface (joint surface)
23 Semipermeable membrane 24, 42a, 42b Glass thin film 31 Distilled water 46, 47 Glass substrate (glass substrate)
51 Conjugate

Claims (9)

A film forming step of forming a thin film having the same main component as the second glass substrate to be bonded to the first glass substrate on the bonding surface of the first glass substrate;
The first glass substrate and the second glass substrate are integrated by evaporating the water after adhering the thin film and the bonding surface of the second glass substrate with water interposed therebetween. A joining process to perform,
A method for joining glass substrates, comprising:   The glass substrate bonding method according to claim 1, wherein the water evaporation in the bonding step is performed in the air by heating at a predetermined temperature not lower than normal temperature and lower than the boiling point of water.   3. The glass substrate according to claim 1, wherein after the bonding step, a bonding strengthening step of heating the bonded body of the first glass substrate and the second glass substrate in a vacuum is performed. Joining method.   The optical thin film having a predetermined optical function is formed in advance on the bonding surface of the first glass substrate, and the film forming step is performed on the surface of the optical thin film. The glass substrate joining method as described.   The glass substrate bonding method according to claim 4, wherein the film forming step is performed after polishing the surface of the optical thin film.   The glass substrate bonding method according to claim 1, wherein a plurality of the thin films are continuously provided in a layer shape.   The thin film formed in the film forming step has a refractive index change amount with respect to d-line of 0.5% or less with respect to a temperature change between room temperature and 100 degrees. 7. The method for bonding glass substrates according to any one of 6 to 6.   The glass substrate bonding method according to claim 1, wherein the thin film is made of silicon dioxide.   A thin film having a main component equal to that of the second glass substrate on a bonding surface of the first glass substrate and the second glass substrate, the bonded body of the first glass substrate and the second glass substrate. And the water interposed between the thin film and the bonding surface of the second glass substrate is evaporated, so that the bonding surface of the second glass substrate passes through the thin film and the first glass. A glass joined body which is joined to a joining surface of a substrate.

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