JP2010107680A - Optical element and method of manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical element having a bonding film whose refractive index is changed in the thickness direction and having excellent light resistance and optical characteristics by firmly joining two optical components with high dimensional accuracy via the bonding film, and to provide a method of manufacturing the optical element which facilitates the manufacture of the same. <P>SOLUTION: The layered optical element 5 is manufactured through: a first step of preparing a first optical component 2 and a second optical component 4 and film-depositing the bonding film 3 by a plasma polymerization method on the surface of the first optical component 2; a second step of applying energy to the bonding film 3 by exposing the bonding film 3 to plasma to develop adhesiveness; and a third step of joining the first and second optical components 2 and 4 via the bonding film 3 to obtain the layered optical element 5. The refractive index of the bonding film 3 is changed so as to connect the refractive index of the first optical component 2 to the refractive index of the second optical component 4 by gradually changing a film-deposition condition in the plasma polymerization method. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical element and a method for manufacturing the optical element.

Conventionally, when two members (substrates) are joined (adhered), a method of using an adhesive such as an epoxy adhesive, a urethane adhesive, or a silicone adhesive is often used.
The adhesive can exhibit adhesiveness regardless of the material of the member. For this reason, members composed of various materials can be bonded in various combinations.
For example, a wavelength plate is known as an optical element having a function of causing a phase difference in transmitted light. The wave plate is a laminate of two birefringent crystal substrates such as quartz, and the substrates are bonded using an adhesive.
In this way, when the substrates are bonded to each other using the adhesive, a liquid or paste adhesive is applied to the bonding surface, and the substrates are bonded to each other through the applied adhesive. Thereafter, the adhesive is cured by the action of heat or light to bond the substrates together.

By the way, the light transmittance of the wave plate is influenced by the difference in refractive index between the adhesive and the substrate. From the viewpoint of increasing the light transmittance, the difference in refractive index is preferably small.
Therefore, Patent Document 1 proposes an adhesive composition containing a refractive index adjusting agent in order to adjust the refractive index of the adhesive in accordance with the refractive index of the substrate. This refractive index adjuster-containing adhesive composition contains a urethane hot melt adhesive as a main component and an aromatic organophosphorus compound as an additive. The refractive index of the refractive index adjusting agent-containing adhesive composition can be adjusted by changing the amount of additive added.

However, since the addition of the additive is usually performed at the time of manufacturing the adhesive, the refractive index of the adhesive cannot be adjusted after the manufacturing. For this reason, it is necessary to prepare several types of adhesives each having a different refractive index in accordance with the refractive index of the substrate to be bonded, which is extremely inefficient for industrial use.
In addition, since it is difficult to uniformly apply the adhesive with a predetermined thickness, it is inevitable that the distance between the substrates is not uniform. In this case, various aberrations such as wavefront aberration occur in the wavelength plate, which may cause a decrease in optical performance.

Furthermore, since the adhesive is made of a resin material, the light resistance is poor, and the refractive index fluctuates over time is also a major problem in bonding optical components.
Furthermore, when the refractive indexes of the two substrates to be bonded are different from each other, even if the refractive index of the adhesive is adjusted and optimized, a difference in refractive index is always generated between the adhesive and the substrate. Light loss and interference fringes are unavoidable due to light scattering at the adhesive interface.

Therefore, in Patent Document 2, when the modified layer and the hard coat layer are formed in this order on the surface of the substrate, the refractive index of the modified layer is continuously from the refractive index of the substrate to the refractive index of the hard coat layer. The modified layer is formed so as to change to Accordingly, it is possible to prevent occurrence of interference fringes when light is incident from the outside.
However, this modified layer functions as an intermediate layer between the substrate and a thin film such as a hard coat layer, but cannot be used as a bonding layer for bonding bulk bodies such as a birefringent crystal substrate.

JP-A-7-188638 JP-A-9-68601

  An object of the present invention is to have a bonding film having a refractive index changed in the thickness direction, and by firmly bonding two optical components with high dimensional accuracy via the bonding film, light resistance and optical characteristics are achieved. An object of the present invention is to provide an excellent optical element and a method for manufacturing an optical element that can easily manufacture such an optical element.

Such an object is achieved by the present invention described below.
The optical element of the present invention includes a first optical component and a second optical component having optical transparency, and a Si skeleton having a random atomic structure including a siloxane (Si—O) bond formed by a plasma polymerization method. And a leaving film that bonds to the Si skeleton, and a bonding film that bonds the first optical component and the second optical component,
Energy is applied to at least a partial region of the bonding film, and the leaving group present on the surface of the bonding film is detached from the Si skeleton, thereby causing the first adhesion to occur in the bonding film. The first optical component and the second optical component are joined,
The bonding film has a portion whose refractive index changes continuously or stepwise along the thickness direction.
As a result, it has a bonding film whose refractive index has changed in the thickness direction, and the two optical components are firmly bonded with high dimensional accuracy via this bonding film, so that it has excellent light resistance and optical characteristics. An element can be obtained.

In the optical element of the present invention, it is preferable that the total of the Si atom content and the O atom content is 10 to 90 atom% among atoms obtained by removing H atoms from all atoms constituting the bonding film. .
Thereby, in the bonding film, Si atoms and O atoms form a strong network, and the bonding film itself becomes strong. Further, such a bonding film exhibits particularly high bonding strength with respect to the first optical component and the second optical component.

In the optical element of the present invention, the abundance ratio of Si atoms and O atoms in the bonding film is preferably 3: 7 to 7: 3.
As a result, the stability of the bonding film is increased, and the first optical component and the second optical component can be bonded more firmly.
In the optical element of the present invention, the crystallinity of the Si skeleton is preferably 45% or less.
As a result, the Si skeleton particularly includes a random atomic structure. And the joining film excellent in dimensional accuracy and adhesiveness is obtained.

In the optical element according to the aspect of the invention, it is preferable that the bonding film includes a Si—H bond.
Si-H bonds are thought to inhibit the regular formation of siloxane bonds. For this reason, the siloxane bond is formed so as to avoid the Si—H bond, and the regularity of the Si skeleton is lowered. In this way, according to the plasma polymerization method, the Si skeleton having a low crystallinity can be efficiently formed by including the Si—H bond in the bonding film.

In the optical element of the present invention, in the infrared absorption spectrum of the bonding film containing the Si—H bond, when the peak intensity attributed to the siloxane bond is 1, the peak intensity attributed to the Si—H bond is 0. It is preferable that it is 001-0.2.
As a result, the atomic structure in the bonding film becomes relatively random. For this reason, the bonding film is particularly excellent in bonding strength, chemical resistance and dimensional accuracy.

In the optical element of the present invention, the leaving group includes an H atom, a B atom, a C atom, an N atom, an O atom, a P atom, an S atom, and a halogen atom, or each of these atoms bonded to the Si skeleton. It is preferably composed of at least one selected from the group consisting of atomic groups arranged in such a manner.
These leaving groups are relatively excellent in binding / leaving selectivity by applying energy. For this reason, the leaving group which leaves | separates comparatively easily and uniformly by providing energy is obtained, and the adhesiveness of the bonding film can be further enhanced.
In the optical element of the present invention, the leaving group is preferably an alkyl group.
Thereby, a bonding film excellent in weather resistance and chemical resistance can be obtained.

In the optical element of the present invention, in the infrared absorption spectrum of the bonding film containing a methyl group as the leaving group, when the peak intensity attributed to the siloxane bond is 1, the peak intensity attributed to the methyl group is 0. It is preferable that it is 05-0.45.
As a result, the content ratio of the methyl group is optimized, and a necessary and sufficient number of active hands are generated in the bonding film while preventing the methyl group from unnecessarily inhibiting the formation of the siloxane bond. Adhesiveness is sufficient. Further, the bonding film exhibits sufficient weather resistance and chemical resistance due to the methyl group.

In the optical element of the present invention, it is preferable that the bonding film has an active hand after the leaving group present at least near the surface thereof is detached from the Si skeleton.
Thereby, the bonding film can be firmly bonded to the second optical component based on chemical bonding.
In the optical element of the present invention, the active hand is preferably a dangling hand or a hydroxyl group.
As a result, particularly strong bonding is possible with respect to the second optical component.

In the optical element of the present invention, it is preferable that the bonding film is composed mainly of polyorganosiloxane.
As a result, a bonding film superior in adhesiveness can be obtained. In addition, this bonding film has excellent weather resistance and chemical resistance, and is effectively used for bonding optical components that are exposed to chemicals and the like for a long time.
In the optical element of the present invention, it is preferable that the polyorganosiloxane is mainly composed of a polymer of octamethyltrisiloxane.
Thereby, a bonding film having particularly excellent adhesiveness can be obtained.

In the optical element of the present invention, in the plasma polymerization method, the high frequency output density when generating plasma is preferably 0.01 to 100 W / cm ² .
Accordingly, it is possible to reliably form a Si skeleton having a random atomic structure while preventing the plasma gas from being added to the source gas more than necessary due to the high frequency power density. Further, it is possible to form the bonding film while reliably adjusting the refractive index to a desired value.

In the optical element of the present invention, the average thickness of the bonding film is preferably 1 to 1000 nm.
Thereby, these can be joined more firmly, preventing that the dimensional accuracy of the optical element which joined the 1st optical component and the 2nd optical component falls remarkably.
In the optical element of the present invention, it is preferable that the bonding film is a solid that does not have fluidity.
Thereby, the dimensional accuracy of the obtained optical element becomes remarkably high compared with the past. In addition, stronger bonding can be achieved in a shorter time than in the past.
In the optical element of the present invention, it is preferable that the refractive index of the bonding film is in the range of 1.35 to 1.6.
Thereby, the adjustment range of the refractive index can be increased, and a bonding film in which the refractive index is changed so as to match the refractive index of many types of optical components can be obtained.

In the optical element of the present invention, it is preferable that the energy is applied by at least one of a method of irradiating the bonding film with energy rays and a method of exposing the bonding film to plasma.
Since ultraviolet rays can be processed over a wide range in a short time without unevenness, the leaving group can be removed efficiently, and can be generated with simple equipment such as a UV lamp. .
According to the method of exposing the bonding film to plasma, energy can be selectively applied in the vicinity of the surface of the bonding film, so that adhesiveness is expressed on the surface, while changes in composition, volume, etc. are caused inside. Can be prevented.

In the optical element of the present invention, the energy beam is preferably ultraviolet light having a wavelength of 126 to 300 nm.
This optimizes the amount of energy imparted to the bonding film, so that the bond between the Si skeleton and the leaving group is selected while preventing the Si skeleton in the bonding film from being destroyed more than necessary. Can be cut. As a result, the bonding film can exhibit adhesiveness while preventing the characteristics (mechanical characteristics, chemical characteristics, etc.) of the bonding film from deteriorating.
In the optical element of the present invention, the plasma exposed to the bonding film is preferably atmospheric pressure plasma.
Thereby, it is possible to prevent the bonding film from being damaged and to obtain a bonding film excellent in adhesiveness and optical performance.

In the optical element of the present invention, it is preferable that each of the first optical component and the second optical component is made of quartz glass or quartz.
These materials have excellent adhesion to the bonding film, excellent transparency, and excellent properties such as heat resistance, light resistance, chemical resistance, and mechanical strength. It is particularly suitable as a constituent material for parts.

In the optical element of the present invention, the refractive index of the first optical component is different from the refractive index of the second optical component,
The refractive index of the bonding film preferably changes so as to connect the refractive index of the first optical component and the refractive index of the second optical component.
Thereby, it is possible to prevent a significant difference in refractive index between the first optical component and the second optical component, and to smoothly connect the refractive index difference. Scattering can be suppressed and the light transmittance of the optical element can be increased.

In the optical element of the present invention, the bonding film is obtained by changing the refractive index continuously or stepwise along the thickness direction by gradually changing the film forming conditions when forming the film.
The film forming condition is preferably a high frequency output.
The high-frequency output is a parameter that is easy to adjust and can be accurately adjusted even under film formation conditions, and is therefore a suitable control factor in terms of strictly adjusting the refractive index.

The optical element of the present invention has two or more bonding films similar to the bonding film between the first optical component and the second optical component,
The entire bonding film of two or more layers preferably has a portion where the refractive index changes continuously or stepwise along the thickness direction.
Thereby, a 1st optical component and a 2nd optical component can be joined more firmly.

The optical element manufacturing method of the present invention provides a first optical component and a second optical component that have optical transparency and can form an optical element by bonding together through a bonding film. The bonding film including a Si skeleton having a random atomic structure including a siloxane (Si—O) bond and a leaving group bonded to the Si skeleton is formed on the surface of the optical component 1 by plasma polymerization. A first step of:
A second step of applying energy to the bonding film to desorb the leaving group present in the bonding film from the Si skeleton and to exhibit adhesiveness;
A third step of bonding the first optical component and the second optical component via the bonding film to obtain an optical element;
In the plasma polymerization method of the first step, the refractive index of the bonding film is continuously or stepwise along the thickness direction by gradually changing the film forming conditions while forming the bonding film. It adjusts so that it may change to.
Thereby, an optical element having high light resistance and high dimensional accuracy and excellent optical characteristics, which is formed by bonding two optical components through the bonding film, can be easily manufactured.

Hereinafter, an optical element and a method for manufacturing the optical element of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.
The optical element of the present invention has two optical components (first optical component 2 and second optical component 4), and a bonding film 3 provided between these optical components 2, 4. Two optical components 2 and 4 are bonded via the bonding film 3.
Among these optical elements, the bonding film 3 is formed by a plasma polymerization method, and has a Si skeleton having a random atomic structure including a siloxane (Si—O) bond and a desorption bonded to the Si skeleton. Group.

Such a bonding film 3 is one in which leaving groups present in the bonding film 3 are desorbed from the Si skeleton by applying energy. And it has the characteristics that adhesiveness expresses in the area | region which provided the energy of the joining film | membrane 3 by detachment | leave of this leaving group.
The bonding film 3 having such a feature can bond the two optical components 2 and 4 firmly with high dimensional accuracy and efficiently at a low temperature. By using the bonding film 3, a highly reliable optical element obtained by firmly bonding the first optical component 2 and the second optical component 4 is obtained.

  In this embodiment, the refractive index of the first optical component 2 and the refractive index of the second optical component 4 are different from each other, and the refractive index of the bonding film 3 is the same as the refractive index of the first optical component 2. It changes continuously along the thickness direction so as to connect the refractive index of the second optical component 4. This change in refractive index can be formed by gradually changing the film forming conditions in the plasma polymerization method. For this reason, as long as the film forming conditions are appropriately set according to the refractive index of each optical component 2, 4, the refractive index is changed in the thickness direction according to the refractive index of each optical component 2, 4. The film 3 can be uniformly formed without unevenness, and an optical element having high optical characteristics can be obtained.

<< First Embodiment >>
Next, a first embodiment of the optical element manufacturing method of the present invention will be described.
1 and 2 are views (longitudinal sectional views) for explaining a first embodiment of a method for producing an optical element of the present invention. In the following description, the upper side in FIGS. 1 and 2 is referred to as “upper” and the lower side is referred to as “lower”.

  In the optical element manufacturing method according to the present embodiment, the first optical component 2 and the second optical component 4 are prepared, and the bonding film 3 is formed on the surface of the first optical component 2 by plasma polymerization. Bonding the first optical component 2 and the second optical component 4 through the bonding film 3, the step of applying energy to the bonding film 3 (second step), and the bonding film 3. And a step of obtaining the laminated optical element 5 (third step). Hereinafter, each process will be described sequentially.

[1] First, the first optical component 2 and the second optical component 4 are prepared.
These optical components 2 and 4 are capable of forming a laminated optical element 5 having optical transparency by being bonded to each other through a bonding film 3. A specific laminated optical element 5 will be exemplified later.
The constituent material of the first optical component 2 may be a light transmissive material, for example, polyolefin such as polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer (EVA), cyclic Polyolefin, modified polyolefin, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyamide (example: nylon 6, nylon 46, nylon 66, nylon 610, nylon 612, nylon 11, nylon 12, nylon 6-12, nylon 6-66) , Polyimide, polyamideimide, polycarbonate (PC), poly- (4-methylpentene-1), ionomer, acrylic resin, acrylonitrile-butadiene-styrene copolymer (ABS resin), acrylonitrile-styrene copolymer (AS resin) ), Polyesters such as tadiene-styrene copolymer, polyoxymethylene, polyvinyl alcohol (PVA), ethylene-vinyl alcohol copolymer (EVOH), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polycyclohexane terephthalate (PCT) , Polyether, polyetherketone (PEK), polyetheretherketone (PEEK), polyetherimide, polyacetal (POM), polyphenylene oxide, modified polyphenylene oxide, polysulfone, polyethersulfone, polyphenylene sulfide, polyarylate, aromatic Polyester (liquid crystal polymer), polytetrafluoroethylene, polyvinylidene fluoride, other fluororesins, styrene, polyolefin Various thermoplastic elastomers such as polyvinyl chloride, polyurethane, polyester, polyamide, polybutadiene, trans polyisoprene, fluororubber, chlorinated polyethylene, epoxy resin, phenol resin, urea resin, melamine resin, Saturated polyester, silicone-based resin, urethane-based resin, etc., or various resin materials such as copolymers, blends, polymer alloys, etc., soda glass, quartz glass, lead glass, potassium glass, borosilicate glass, Examples thereof include glass materials such as alkali-free glass, crystal materials such as quartz, calcite, sapphire, CaF ₂ , BaF ₂ , MgF ₂ , LiF, KBr, KCl, NaCl, MgO, YVO ₄ , and LiNbO ₃ .

Among these, from the viewpoint of adhesion (bondability) to the bonding film 3, silicon oxide materials such as quartz glass and quartz are preferably used. Since the silicon oxide-based material has excellent transparency and excellent properties such as heat resistance, light resistance, chemical resistance, and mechanical strength, the configuration of the first optical component 2 It is particularly suitable as a material.
On the other hand, the constituent material of the second optical component 4 may be appropriately selected from the constituent materials of the first optical component 2, but the constituent material of the first optical component 2 and the constituent material of the second optical component 4 Are different from each other, and accordingly the refractive indexes are also different from each other.
Further, the first optical component 2 and the second optical component 4 may be obtained by forming various optical thin films on the surfaces thereof.

Next, as shown in FIG. 1A, a bonding film 3 is formed on the surface of the first optical component 2 (first step). The bonding film 3 is located between the first optical component 2 and the second optical component 4 and bears the bonding therebetween.
As shown in FIGS. 3 and 4, the bonding film 3 includes a Si skeleton 301 including a siloxane (Si—O) bond 302 and a random atomic structure, and a leaving group 303 bonded to the Si skeleton 301. It is what you have.

The bonding film 3 is formed by a plasma polymerization method. In this film formation, the refractive index of the first optical component 2 is changed by gradually changing the film formation conditions. And the refractive index of the second optical component 4 are changed. That is, in the bonding film 3, in the vicinity of the surface on the first optical component 2 side, the refractive index is substantially the same as the refractive index of the first optical component 2, and the second optical component 4 side. In the vicinity of this surface, the refractive index is substantially the same as the refractive index of the second optical component 4. The refractive index continuously changes in the intermediate portion of the bonding film 3.
The bonding film 3 will be described later in detail.

In addition, before forming the bonding film 3 in the region where the bonding film 3 of the first optical component 2 is to be formed, depending on the constituent material of the first optical component 2, the first optical component is previously formed. It is preferable to perform a surface treatment for improving the adhesion between the bonding film 2 and the bonding film 3.
Examples of the surface treatment include physical surface treatment such as sputtering treatment and blast treatment, plasma treatment using oxygen plasma, nitrogen plasma, etc., corona discharge treatment, etching treatment, electron beam irradiation treatment, ultraviolet irradiation treatment, ozone Examples include chemical surface treatment such as exposure treatment, or a combination of these. By performing such treatment, the region where the bonding film 3 of the first optical component 2 is to be formed can be cleaned and the region can be activated. Thereby, the bonding strength between the first optical component 2 and the bonding film 3 can be increased.
In addition, by using plasma treatment among these surface treatments, the surface of the first optical component 2 can be particularly optimized in order to form the bonding film 3.
In addition, when the 1st optical component 2 which performs surface treatment is comprised with the resin material (polymer material), especially a corona discharge process, a nitrogen plasma process, etc. are used suitably.

Further, depending on the constituent material of the first optical component 2, there is a material in which the bonding strength of the bonding film 3 is sufficiently high without performing the surface treatment as described above. Examples of the constituent material of the first optical component 2 that can obtain such an effect include materials mainly composed of various glass materials and various crystal materials as described above.
The surface of the first optical component 2 made of such a material is covered with an oxide film, and a relatively active hydroxyl group is bonded to the surface of the oxide film. Therefore, when the first optical component 2 made of such a material is used, the adhesion strength between the first optical component 2 and the bonding film 3 can be increased without performing the surface treatment as described above. it can.
In this case, the entire first optical component 2 may not be made of the material as described above, and at least the vicinity of the surface of the region where the bonding film 3 is to be formed is made of the material as described above. Just do it.

  On the other hand, the bonding strength between the first optical component 2 and the second optical component 4 is sufficiently high even if the second optical component 4 is not subjected to the surface treatment as described above depending on the constituent material. There is something to be. As the constituent material of the second optical component 4 capable of obtaining such effects, the same constituent materials as those of the first optical component 2 described above, that is, various glass materials, various crystal materials, and the like can be used. .

Further, in the case where the following group or substance is included in the region that is in close contact with the bonding film 3 of the second optical component 4, the first optical component 2 and the second optical component 2 can be used without performing the surface treatment as described above. The bonding strength with the optical component 4 can be sufficiently increased.
Examples of such groups and substances include functional groups such as hydroxyl groups, thiol groups, carboxyl groups, amino groups, nitro groups, and imidazole groups, radicals, ring-opened molecules, double bonds, and triple bonds. And at least one group or substance selected from the group consisting of a saturated bond, a halogen such as F, Cl, Br, and I, and a peroxide.
Further, it is preferable to appropriately select and perform various surface treatments as described above so that a surface having such a material can be obtained.

Further, instead of the surface treatment, an intermediate layer is formed in advance in at least the region where the bonding film 3 of the first optical component 2 is to be formed and the region where the bonding film 3 of the second optical component 4 is in close contact. Is preferred.
The intermediate layer may have any function. For example, a layer having a function of improving adhesion to the bonding film 3, a cushioning function (buffer function), a function of reducing stress concentration, and the like are preferable. By using such an intermediate layer, a highly reliable laminated optical element can be obtained.

Examples of the constituent material of the intermediate layer include metal oxides, oxide materials such as silicon oxide, metal nitrides, nitride materials such as silicon nitride, carbon such as graphite and diamond-like carbon. Materials, silane coupling agents, thiol compounds, metal alkoxides, self-assembled film materials such as metal-halogen compounds, resin adhesives, resin films, resin coating materials, various rubber materials, resins such as various elastomers A system material etc. are mentioned, Among these, it can use combining 1 type (s) or 2 or more types.
Further, among the intermediate layers formed of these materials, the bonding strength of the laminated optical element 5 can be particularly increased by the intermediate layer formed of the oxide-based material.

[2] Next, as shown in FIG. 1B, energy is applied to the bonding film 3.
When energy is applied, the leaving group 303 is detached from the Si skeleton 301 on the surface of the bonding film 3. Since an active hand is generated after the leaving group 303 is removed, stable adhesiveness to the second optical component 4 is expressed in the bonding film 3. As a result, the bonding film 3 can be stably and firmly bonded to the second optical component 4 based on chemical bonding.

  Here, the bonding film 3 before energy is applied has a Si skeleton 301 and a leaving group 303 as shown in FIG. When energy is applied to the bonding film 3, a leaving group 303 (in this embodiment, a methyl group) near the surface is detached from the Si skeleton 301 in particular. As a result, as shown in FIG. 4, active hands 304 are generated on the surface 35 of the bonding film 3 and activated. As a result, adhesiveness develops on the surface of the bonding film 3.

It should be noted that “activating” the bonding film 3 means that the surface 35 of the bonding film 3 and the internal leaving group 303 are removed, and a bond not terminated in the Si skeleton 301 (hereinafter referred to as “unbonded bond”). "Or" dangling bond "), a state in which this dangling bond is terminated by a hydroxyl group (OH group), or a state in which these states are mixed.
Therefore, the active hand 304 means a dangling bond (dangling bond) or a dangling bond terminated by a hydroxyl group. According to such an active hand 304, particularly strong bonding can be performed to the second optical component 4.

Examples of a method for applying energy to the bonding film 3 include a method of irradiating the bonding film 3 with energy rays, a method of exposing the bonding film 3 to plasma, and the like.
Among these, as the energy rays irradiated to the bonding film 3, for example, light such as ultraviolet rays and laser light, X-rays, γ rays, electron beams, particle beams such as ion beams, etc., or a combination of these energy rays Can be mentioned.

  Among these energy rays, it is particularly preferable to use ultraviolet rays having a wavelength of about 126 to 300 nm. According to such ultraviolet rays, the amount of energy applied is optimized, so that the Si skeleton 301 in the bonding film 3 is prevented from being destroyed more than necessary, and between the Si skeleton 301 and the leaving group 303. Can be selectively cleaved. Thereby, adhesiveness can be expressed in the bonding film 3 while preventing the characteristics (mechanical characteristics, chemical characteristics, etc.) of the bonding film 3 from being deteriorated.

In addition, since ultraviolet rays can be processed in a short time without unevenness, the leaving group 303 can be efficiently eliminated. Furthermore, ultraviolet rays also have the advantage that they can be generated with simple equipment such as UV lamps.
The wavelength of ultraviolet light is more preferably about 160 to 200 nm.
In the case of using the UV lamp, the output may vary depending on the area of the bonding film 3 is preferably from ^1mW / cm ^{2 ~1W} / cm 2 or ^so, at 5mW / cm ² ~50mW / cm 2 of about More preferably. In this case, the distance between the UV lamp and the bonding film 3 is preferably about 3 to 3000 mm, more preferably about 10 to 1000 mm.

  Further, the time for irradiating the ultraviolet rays is such a time that the leaving group 303 in the vicinity of the surface 35 of the bonding film 3 can be released, that is, a time that the leaving group 303 inside the bonding film 3 is not released in a large amount. Is preferable. Specifically, it is preferably about 0.5 to 30 minutes, more preferably about 1 to 10 minutes, although it varies slightly depending on the amount of ultraviolet light, the constituent material of the bonding film 3 and the like.

Moreover, although an ultraviolet-ray may be irradiated continuously in time, you may irradiate intermittently (pulse form).
On the other hand, examples of the laser light include an excimer laser (femtosecond laser), an Nd-YAG laser, an Ar laser, a CO ₂ laser, and a He—Ne laser.

  The bonding film 3 may be irradiated with energy rays in any atmosphere. Specifically, the atmosphere, an oxidizing gas atmosphere such as oxygen, a reducing gas atmosphere such as hydrogen, nitrogen, An inert gas atmosphere such as argon, or a reduced pressure (vacuum) atmosphere in which these atmospheres are reduced can be used, and it is particularly preferable to perform in an inert gas atmosphere or a reduced pressure (vacuum) atmosphere. Thereby, it is possible to prevent the bonding film 3 from being oxidized and altered or deteriorated.

Furthermore, this atmosphere is preferably a dry atmosphere. As a result, it is possible to prevent water vapor in the atmosphere from adsorbing to the traces of chemical bonds that have been cut by irradiation with ultraviolet rays, and to prevent unintended changes in the composition of the bonding film 3.
Specifically, the dew point of the atmosphere is preferably −10 ° C. or lower, and more preferably −20 ° C. or lower.
Moreover, according to the method of irradiating energy rays, the magnitude of energy to be applied can be easily adjusted with high accuracy. For this reason, it becomes possible to adjust the desorption amount of the leaving group 303 desorbed from the bonding film 3. As a result, the bonding strength of the laminated optical element 5 can be easily controlled.

That is, by increasing the amount of elimination of the leaving group 303, more active hands are generated on the surface 35 and inside of the bonding film 3, so that the adhesiveness expressed in the bonding film 3 can be further increased. On the other hand, by reducing the amount of elimination of the leaving group 303, the number of active hands generated on the surface 35 and inside of the bonding film 3 can be reduced, and the adhesiveness expressed in the bonding film 3 can be suppressed.
In addition, in order to adjust the magnitude | size of the energy to provide, what is necessary is just to adjust conditions, such as the kind of energy beam, the output of an energy beam, the irradiation time of an energy beam.

  On the other hand, according to the method in which the bonding film 3 is exposed to plasma, energy can be selectively applied to the vicinity of the surface 35 of the bonding film 3, thereby preventing the leaving group 303 from being detached from the bonding film 3. The As a result, adhesiveness is surely developed on the surface 35 of the bonding film 3, and the composition, volume, refractive index, etc. of the bonding film 3 are changed unintentionally with the elimination of the leaving group 303 inside. Can be prevented.

  In this case, it is preferable to use atmospheric pressure plasma as the plasma to which the bonding film 3 is exposed. According to atmospheric pressure plasma, plasma treatment can be easily performed without using expensive equipment such as decompression means. In addition to the direct plasma method in which plasma is generated in the vicinity of the bonding film 3, a remote plasma method or a downflow plasma method in which the object to be processed and the plasma generation unit are separated is also preferably used for this plasma treatment. According to the direct plasma method, since plasma is generated in the vicinity of the bonding film 3, plasma processing can be performed efficiently and uniformly. Further, when the object to be processed and the plasma generating part are separated from each other, the object to be processed and the plasma generating part do not interfere with each other, so that the object to be processed can be avoided from ion damage.

Further, when the plasma treatment is performed in a reduced pressure atmosphere, there is a possibility that a gas unintentionally confined inside the bonding film 3 or a gas generated over time is forcibly extracted to the outside of the bonding film 3. . When such a phenomenon occurs, the bonding film 3 is damaged, resulting in a decrease in adhesiveness and a decrease in optical performance.
On the other hand, by performing plasma treatment under atmospheric pressure, it is possible to prevent the bonding film 3 from being damaged, and to obtain the bonding film 3 excellent in adhesiveness and optical performance.
In addition, examples of the gas that generates plasma include Ar, He, H ₂ , N ₂ , and O ₂ , and a mixture of two or more of these may be used. Among these, in consideration of oxidation of the bonding film 3, an inert gas such as Ar or He is preferably used.

The plasma treatment can also be performed using a plasma polymerization apparatus 100 shown in FIG. That is, after the bonding film 3 is formed using the plasma polymerization apparatus 100 shown in FIG. 5, the plasma treatment of this step can be continuously performed without removing the bonding film 3 from the apparatus, so that the optical element of the present invention is manufactured. The method can be simplified.
Further, when plasma is generated by discharge, the voltage applied between the electrodes is preferably a high frequency of MHz or higher. Thereby, compared with the case of direct current discharge, since a discharge start voltage falls, a discharge state can be maintained easily. Moreover, by using a high frequency, the ionization degree in plasma becomes high and a plasma density becomes high. As a result, the elimination of the leaving group 303 by plasma can be performed efficiently.
The frequency of the voltage applied between the electrodes is not particularly limited, but is preferably about 10 to 50 MHz, and more preferably about 10 to 40 MHz.
Moreover, as a method of applying energy in the step [2], in addition to the method described above, methods such as heating, pressurization, exposure to ozone, and the like can be given.

  Here, the bonding film 3 before energy is applied has a Si skeleton 301 and a leaving group 303 as shown in FIG. When energy is applied to the bonding film 3, the leaving group 303 (in this embodiment, a methyl group) is detached from the Si skeleton 301. As a result, as shown in FIG. 4, active hands 304 are generated on the surface 35 of the bonding film 3 and activated. As a result, adhesiveness develops on the surface of the bonding film 3.

It should be noted that “activating” the bonding film 3 means that the surface 35 of the bonding film 3 and the internal leaving group 303 are removed, and a bond not terminated in the Si skeleton 301 (hereinafter referred to as “unbonded bond”). "Or" dangling bond "), a state in which this dangling bond is terminated by a hydroxyl group (OH group), or a state in which these states are mixed.
Therefore, the active hand 304 means a dangling bond (dangling bond) or a dangling bond terminated by a hydroxyl group. According to such an active hand 304, the first optical component 2 and the second optical component 4 can be bonded more firmly through the bonding film 3.

[3] Next, as shown in FIG. 1 (c), the first optical component 2 and the second optical component 4 are brought into close contact with the activated bonding film 3 and the second optical component 4. And paste together. Thereby, the laminated optical element 5 as shown in FIG. 2D is obtained (third step).
In the laminated optical element 5 obtained in this way, it is not a bond based on a physical bond such as an anchor effect, but a covalent bond, unlike the adhesive used in the conventional optical element manufacturing method. Bonding is based on such a strong chemical bond that occurs in a short time. For this reason, the laminated optical element 5 can be formed in a short time, is extremely difficult to peel off, and is difficult to cause uneven bonding.

In addition, according to such a method, unlike the conventional solid bonding, the heat treatment at a high temperature (for example, 700 ° C. or higher) is not required, so the first optical component composed of a material having low heat resistance. The second and second optical components 4 can also be used for bonding.
In addition, since the first optical component 2 and the second optical component 4 are bonded via the bonding film 3, there is no restriction on the constituent materials of the first optical component 2 and the second optical component 4. There are also advantages.

From the above, according to the present invention, the range of selection of each constituent material of the first optical component 2 and the second optical component 4 can be increased.
In the present embodiment, the bonding film 3 is provided on only one of the first optical component 2 and the second optical component 4 used for bonding (in the present embodiment, the first optical component 2). ing. When forming the bonding film 3 on the first optical component 2, the first optical component 2 is exposed to plasma for a relatively long time depending on the method of forming the bonding film 3. Then, the second optical component 4 is not exposed to plasma. Therefore, for example, even when the durability of the second optical component 4 against plasma is extremely low, according to the method according to the present embodiment, the first optical component 2 and the second optical component 4 are firmly connected. Can be joined. Therefore, there is an advantage that the material constituting the second optical component 4 can be selected from a wide range of materials without much consideration of durability against plasma.

Here, the mechanism by which the first optical component 2 and the second optical component 4 are joined in this step will be described.
For example, a case where a hydroxyl group is exposed on the bonding surface of the second optical component 4 will be described as an example. In this step, the surface 35 of the bonding film 3 and the bonding surface of the second optical component 4 are in contact with each other. In addition, when these are bonded together, the hydroxyl group present on the surface 35 of the bonding film 3 and the hydroxyl group present on the bonding surface of the second optical component 4 are attracted to each other by hydrogen bonding, and there is an attractive force between the hydroxyl groups. appear. It is inferred that the first optical component 2 and the second optical component 4 are joined by this attractive force.
Further, the hydroxyl groups attracting each other by this hydrogen bond are dehydrated and condensed depending on the temperature condition or the like. As a result, at the contact interface between the first optical component 2 and the second optical component 4, the bonds in which the hydroxyl groups are bonded are bonded through oxygen atoms. Thereby, it is guessed that the 1st optical component 2 and the 2nd optical component 4 are joined more firmly.

  Note that the active state of the surface of the bonding film 3 activated in the step [2] relaxes with time. For this reason, it is preferable to perform this process [3] as soon as possible after completion of the process [2]. Specifically, after the completion of the step [2], the step [3] is preferably performed within 60 minutes, and more preferably within 5 minutes. If it is within this time, the surface of the bonding film 3 maintains a sufficiently active state. Therefore, when the first optical component 2 and the second optical component 4 are bonded together in this step, there is a gap between them. Sufficient bonding strength can be obtained.

  In other words, since the bonding film 3 before activation is a bonding film having the Si skeleton 301, it is chemically relatively stable and has excellent weather resistance. For this reason, the bonding film 3 before being activated is suitable for long-term storage. Therefore, a large amount of the first optical component 2 having such a bonding film 3 is manufactured or purchased and stored, and the step [2] is added to the necessary number just before performing the bonding in this step. If the energy application described in 1 is performed, it is effective from the viewpoint of the manufacturing efficiency of the laminated optical element 5.

As described above, the laminated optical element (optical element of the present invention) 5 shown in FIG. 2D can be obtained.
In FIG. 2D, the second optical component 4 is overlaid so as to cover the entire surface of the bonding film 3, but their relative positions may be shifted from each other. That is, the second optical component 4 may protrude from the bonding film 3.

In the laminated optical element 5 thus obtained, the bonding strength between the first optical component 2 and the second optical component 4 is preferably 5 MPa (50 kgf / cm ² ) or more, preferably 10 MPa (100 kgf / Cm ² ) or more. The laminated optical element 5 having such a bonding strength can sufficiently prevent the peeling.
After obtaining the laminated optical element 5, at least one of the following two steps ([4A] and [4B]) (laminated optical element 5) is performed on the laminated optical element 5 as necessary. The step of increasing the bonding strength) may be performed. Thereby, the joint strength of the laminated optical element 5 can be further improved.

[4A] As shown in FIG. 2 (e), the obtained laminated optical element 5 is pressurized in a direction in which the first optical component 2 and the second optical component 4 approach each other.
Thereby, the surface of the bonding film 3 is closer to the surface of the first optical component 2 and the surface of the second optical component 4, respectively, and the bonding strength in the laminated optical element 5 can be further increased.
Further, by pressurizing the laminated optical element 5, the gap remaining at the bonding interface in the laminated optical element 5 can be crushed and the bonding area can be further expanded. Thereby, the joint strength in the laminated optical element 5 can be further increased.
At this time, the pressure when pressurizing the laminated optical element 5 is a pressure that does not damage the laminated optical element 5 and is preferably as high as possible. Thereby, the joint strength in the laminated optical element 5 can be increased in proportion to this pressure.

In addition, what is necessary is just to adjust this pressure suitably according to conditions, such as each constituent material of each of the 1st optical component 2 and the 2nd optical component 4, each thickness, and a joining apparatus. Specifically, it is preferably about 0.2 to 10 MPa, preferably about 1 to 5 MPa, although it varies slightly depending on the constituent materials and thicknesses of the first optical component 2 and the second optical component 4. It is more preferable that Thereby, the joining strength of the laminated optical element 5 can be reliably increased. The pressure may exceed the upper limit, but depending on the constituent materials of the first optical component 2 and the second optical component 4, the first optical component 2 and the second optical component 4 There is a risk of damage.
The time for pressurization is not particularly limited, but is preferably about 10 seconds to 30 minutes. In addition, what is necessary is just to change suitably the time to pressurize according to the pressure at the time of pressurizing. Specifically, the higher the pressure at which the laminated optical element 5 is pressed, the higher the bonding strength can be achieved even if the pressing time is shortened.

[4B] The obtained laminated optical element 5 is heated as shown in FIG.
Thereby, the joint strength in the laminated optical element 5 can be further increased.
At this time, the temperature when heating the laminated optical element 5 is not particularly limited as long as it is higher than room temperature and lower than the heat-resistant temperature of the laminated optical element 5, but is preferably about 25 to 100 ° C., more preferably 50. ˜100 ° C. Heating at a temperature in such a range can reliably increase the bonding strength while reliably preventing the laminated optical element 5 from being altered or deteriorated by heat.

The heating time is not particularly limited, but is preferably about 1 to 30 minutes.
Moreover, when performing both said process [4A] and [4B], it is preferable to perform these simultaneously. That is, as shown in FIG. 2E, the laminated optical element 5 is preferably heated while being pressurized. Thereby, the effect by pressurization and the effect by heating are exhibited synergistically, and the joint strength of the laminated optical element 5 can be particularly increased.
By performing the steps as described above, it is possible to easily further improve the bonding strength in the laminated optical element 5.

Here, the bonding film 3 will be described in detail.
As described above, the bonding film 3 is formed by a plasma polymerization method. As shown in FIG. 3, the Si skeleton 301 including a siloxane (Si—O) bond 302 and having a random atomic structure, It has a leaving group 303 bonded to the Si skeleton 301. Such a bonding film 3 becomes a strong film that is difficult to be deformed due to the influence of the Si skeleton 301 including the siloxane bond 302 and having a random atomic structure. This is presumably because the crystallinity of the Si skeleton 301 becomes low, so that defects such as dislocations and misalignments at the grain boundaries are difficult to occur. For this reason, the bonding film 3 itself has high bonding strength, chemical resistance, light resistance and dimensional accuracy, and the finally obtained laminated optical element 5 also has bonding strength, chemical resistance, light resistance and dimensional accuracy. A high one is obtained.

In such a bonding film 3, when energy is applied, the leaving group 303 is detached from the Si skeleton 301, and as shown in FIG. 4, active hands 304 are generated on the surface 35 and inside of the bonding film 3. It is. As a result, adhesiveness is developed on the surface of the bonding film 3. When such adhesiveness is developed, the bonding film 3 can be firmly and efficiently bonded to the second optical component 4 with high dimensional accuracy.
Note that the bond energy between the leaving group 303 and the Si skeleton 301 is smaller than the bond energy of the siloxane bond 302 in the Si skeleton 301. For this reason, the bonding film 3 selectively breaks the bond between the leaving group 303 and the Si skeleton 301 and prevents the leaving group 303 from being removed while preventing the Si skeleton 301 from being destroyed by the application of energy. Can be separated.

  Further, such a bonding film 3 is a solid having no fluidity. For this reason, conventionally, the thickness and shape of the adhesive layer (bonding film 3) hardly change compared to a liquid or viscous liquid adhesive. Thereby, the dimensional accuracy of the laminated optical element 5 is remarkably higher than the conventional one. Furthermore, since the time required for curing the adhesive is not required, strong bonding can be achieved in a short time.

Note that, in the bonding film 3, in particular, the total of the Si atom content and the O atom content is about 10 to 90 atomic% among atoms obtained by removing H atoms from all atoms constituting the bonding film 3. Is preferable, and it is more preferable that it is about 20-80 atomic%. If Si atoms and O atoms are contained in the above-mentioned range, the bonding film 3 forms a strong network of Si atoms and O atoms, and the bonding film 3 itself becomes strong. In addition, the bonding film 3 exhibits particularly high bonding strength with respect to the first optical component 2 and the second optical component 4.
The abundance ratio of Si atoms and O atoms in the bonding film 3 is preferably about 3: 7 to 7: 3, and more preferably about 4: 6 to 6: 4. By setting the abundance ratio of Si atoms and O atoms to be within the above range, the stability of the bonding film 3 is increased, and the first optical component 2 and the second optical component 4 are bonded more firmly. Will be able to.

The crystallinity of the Si skeleton 301 in the bonding film 3 is preferably 45% or less, and more preferably 40% or less. As a result, the Si skeleton 301 includes a sufficiently random atomic structure. For this reason, the characteristics of the Si skeleton 301 described above become obvious, and the dimensional accuracy and adhesiveness of the bonding film 3 become more excellent.
Note that the crystallinity of the Si skeleton 301 can be measured by a general crystallinity measurement method, and specifically, a method of measuring based on the intensity of scattered X-rays in a crystal portion (X-ray method). , The method of obtaining from the intensity of the crystallization band of infrared absorption (infrared method), the method of obtaining based on the area under the differential curve of nuclear magnetic resonance absorption (nuclear magnetic resonance absorption method), It can be measured by a chemical method utilizing the difficulty.

  The bonding film 3 preferably contains Si—H bonds in the structure. This Si-H bond is generated in the polymer when the silane undergoes a polymerization reaction by the plasma polymerization method. At this time, if the Si-H bond inhibits the regular formation of the siloxane bond, Conceivable. For this reason, the siloxane bond is formed so as to avoid the Si—H bond, and the regularity of the atomic structure of the Si skeleton 301 is lowered. Thus, according to the plasma polymerization method, the Si skeleton 301 having a low crystallinity can be efficiently formed.

  On the other hand, the greater the Si—H bond content in the bonding film 3, the lower the crystallinity. Specifically, in the infrared absorption spectrum of the bonding film 3, when the intensity of the peak attributed to the siloxane bond is 1, the intensity of the peak attributed to the Si—H bond is about 0.001 to 0.2. It is preferable that it is about 0.002-0.05, and it is further more preferable that it is about 0.005-0.02. When the ratio of the Si—H bond to the siloxane bond is within the above range, the atomic structure in the bonding film 3 is relatively random. For this reason, when the peak intensity of the Si—H bond is within the above range with respect to the peak intensity of the siloxane bond, the bonding film 3 is particularly excellent in bonding strength, chemical resistance, and dimensional accuracy.

Further, as described above, the leaving group 303 bonded to the Si skeleton 301 acts to generate an active hand in the bonding film 3 by detaching from the Si skeleton 301. Therefore, although the leaving group 303 is relatively easily and uniformly desorbed by being given energy, it is securely bonded to the Si skeleton 301 so as not to be desorbed when no energy is given. It needs to be a thing.
In the film formation by the plasma polymerization method, the component of the source gas is polymerized to generate a Si skeleton 301 containing a siloxane bond and a residue bonded thereto. For example, this residue is a leaving group. 303.

  From this point of view, the leaving group 303 includes an H atom, a B atom, a C atom, an N atom, an O atom, a P atom, an S atom, and a halogen atom, or each of these atoms. What consists of at least 1 sort (s) selected from the group which consists of an atomic group arrange | positioned so that it may couple | bond with frame | skeleton 301 is used preferably. Such a leaving group 303 is relatively excellent in bond / elimination selectivity by energy application. For this reason, such a leaving group 303 can sufficiently satisfy the above-described necessity, and the adhesiveness of the bonding film 3 can be made higher.

Examples of the atomic group (group) arranged so that each atom as described above is bonded to the Si skeleton 301 include, for example, an alkyl group such as a methyl group and an ethyl group, and an alkenyl group such as a vinyl group and an allyl group. Aldehyde group, ketone group, carboxyl group, amino group, amide group, nitro group, halogenated alkyl group, mercapto group, sulfonic acid group, cyano group, isocyanate group and the like.
Among these groups, the leaving group 303 is particularly preferably an alkyl group. Since the alkyl group has high chemical stability, the bonding film 3 containing the alkyl group is excellent in weather resistance and chemical resistance.

Here, when the leaving group 303 is a methyl group (—CH ₃ ), the preferred content is defined as follows from the peak intensity in the infrared light absorption spectrum.
That is, in the infrared absorption spectrum of the bonding film 3, when the intensity of the peak attributed to the siloxane bond is 1, the intensity of the peak attributed to the methyl group is preferably about 0.05 to 0.45. More preferably, it is about 0.1 to 0.4, and more preferably about 0.2 to 0.3. Since the ratio of the peak intensity of the methyl group to the peak intensity of the siloxane bond is within the above range, it is necessary and sufficient in the bonding film 3 while preventing the methyl group from inhibiting the generation of the siloxane bond more than necessary. Since a number of active hands are generated, sufficient adhesiveness is generated in the bonding film 3. Further, the bonding film 3 exhibits sufficient weather resistance and chemical resistance due to the methyl group.

Examples of the constituent material of the bonding film 3 having such characteristics include a polymer containing a siloxane bond such as polyorganosiloxane and an organic group capable of forming a leaving group 303 bonded thereto.
The bonding film 3 made of polyorganosiloxane itself has excellent mechanical properties. In addition, it exhibits particularly excellent adhesion to many materials. Therefore, the bonding film 3 made of polyorganosiloxane adheres particularly firmly to the first optical component 2 and also exhibits a particularly strong adhesion force to the second optical component 4, and as a result. As a result, the first optical component 2 and the second optical component 4 can be firmly bonded.

Polyorganosiloxane usually exhibits water repellency (non-adhesiveness), but when given energy, it can easily desorb organic groups, changes to hydrophilicity, and exhibits adhesiveness. However, there is an advantage that the non-adhesiveness and the adhesiveness can be controlled easily and reliably.
This water repellency (non-adhesiveness) is mainly due to the action of alkyl groups contained in the polyorganosiloxane. Therefore, the bonding film 3 made of polyorganosiloxane exhibits adhesiveness on the surface 35 when energy is applied thereto, and at the portion other than the surface 35, the above-described action / effect by the alkyl group is obtained. Has the advantage of being Therefore, such a bonding film 3 has excellent weather resistance and chemical resistance, and is effectively used when assembling an optical element that is exposed to chemicals for a long time.

  Further, among polyorganosiloxanes, those mainly composed of a polymer of octamethyltrisiloxane are preferred. The bonding film 3 mainly composed of a polymer of octamethyltrisiloxane is particularly excellent in adhesiveness. Moreover, since the raw material which has octamethyltrisiloxane as a main component is liquid at normal temperature and has an appropriate viscosity, there is also an advantage that it is easy to handle.

The average thickness of the bonding film 3 is preferably about 1 to 1000 nm, and more preferably about 2 to 800 nm. By setting the average thickness of the bonding film 3 within the above range, these can be bonded more firmly while preventing the dimensional accuracy of the laminated optical element 5 from being significantly lowered.
That is, when the average thickness of the bonding film 3 is less than the lower limit, sufficient bonding strength may not be obtained. On the other hand, when the average thickness of the bonding film 3 exceeds the upper limit, the dimensional accuracy of the laminated optical element 5 may be reduced.

  Furthermore, if the average thickness of the bonding film 3 is within the above range, a certain degree of shape followability is ensured for the bonding film 3. For this reason, for example, even when unevenness is present on the bonding surface of the first optical component 2 (surface adjacent to the bonding film 3), it follows the shape of the unevenness depending on the height of the unevenness. The bonding film 3 can be deposited on the substrate. As a result, the bonding film 3 can absorb the unevenness and reduce the height of the unevenness generated on the surface. And when the 1st optical component 2 and the 2nd optical component 4 are bonded together, both adhesiveness can be improved.

Note that the degree of the shape followability as described above becomes more significant as the thickness of the bonding film 3 increases. Therefore, the thickness of the bonding film 3 should be as large as possible in order to sufficiently ensure the shape following ability.
In addition, the average thickness of the bonding film 3 is preferably equal to or less than the wavelength of light transmitted through the laminated optical element 5. Thereby, in the laminated optical element 5, the optical influence of the bonding film 3 on the transmitted light can be reduced.

  The bonding film 3 has been described in detail above. Such a bonding film 3 is produced by a plasma polymerization method. According to the plasma polymerization method, the dense and homogeneous bonding film 3 can be efficiently produced. Thereby, the bonding film 3 can be particularly strongly bonded to the second optical component 4. Furthermore, the bonding film 3 manufactured by the plasma polymerization method is maintained for a relatively long time in a state where energy is applied and activated. For this reason, the manufacturing process of the laminated optical element 5 can be simplified and efficient.

Hereinafter, a method for producing the bonding film 3 will be described.
First, prior to the description of the method for manufacturing the bonding film 3, a plasma polymerization apparatus used for manufacturing the bonding film 3 by performing plasma polymerization on the first optical component 2 will be described.
FIG. 5 is a longitudinal sectional view schematically showing a plasma polymerization apparatus used in the method for producing an optical element of the present invention. In the following description, the upper side in FIG. 5 is referred to as “upper” and the lower side is referred to as “lower”.

  The plasma polymerization apparatus 100 shown in FIG. 5 includes a chamber 101, a first electrode 130 that supports the first optical component 2, a second electrode 140, and a power source that applies a high-frequency voltage between the electrodes 130 and 140. A circuit 180, a gas supply unit 190 that supplies gas into the chamber 101, and an exhaust pump 170 that exhausts the gas in the chamber 101 are provided. Among these parts, the first electrode 130 and the second electrode 140 are provided in the chamber 101. Hereinafter, each part will be described in detail.

The chamber 101 is a container that can keep the inside airtight, and is used with the inside being in a reduced pressure (vacuum) state. Therefore, the chamber 101 has pressure resistance that can withstand a pressure difference between the inside and the outside.
The chamber 101 shown in FIG. 5 has a substantially cylindrical chamber body whose axis is arranged along the horizontal direction, a circular side wall that seals the left opening of the chamber body, and a circle that seals the right opening. And side walls.

A supply port 103 is provided above the chamber 101, and an exhaust port 104 is provided below the chamber 101. A gas supply unit 190 is connected to the supply port 103, and an exhaust pump 170 is connected to the exhaust port 104.
In this embodiment, the chamber 101 is made of a highly conductive metal material and is electrically grounded via the ground wire 102.

The first electrode 130 has a plate shape and supports the first optical component 2.
The first electrode 130 is provided on the inner wall surface of the side wall of the chamber 101 along the vertical direction, whereby the first electrode 130 is electrically grounded via the chamber 101. As shown in FIG. 5, the first electrode 130 is provided concentrically with the chamber body.

An electrostatic chuck (suction mechanism) 139 is provided on the surface of the first electrode 130 that supports the first optical component 2.
As shown in FIG. 5, the electrostatic chuck 139 can support the first optical component 2 along the vertical direction. Further, even if the first optical component 2 has a slight warp, the first optical component 2 can be subjected to a plasma treatment in a state where the warp is corrected by being attracted to the electrostatic chuck 139.

The second electrode 140 is provided to face the first electrode 130 with the first optical component 2 interposed therebetween. Note that the second electrode 140 is provided in a state of being separated (insulated) from the inner wall surface of the side wall of the chamber 101.
A high frequency power source 182 is connected to the second electrode 140 via a wiring 184. A matching box (matching unit) 183 is provided in the middle of the wiring 184. The wiring 184, the high-frequency power source 182 and the matching box 183 constitute a power circuit 180.
According to such a power supply circuit 180, since the first electrode 130 is grounded, a high frequency voltage is applied between the first electrode 130 and the second electrode 140. As a result, an electric field whose direction is reversed at a high frequency is induced in the gap between the first electrode 130 and the second electrode 140.

The gas supply unit 190 supplies a predetermined gas into the chamber 101.
A gas supply unit 190 shown in FIG. 5 stores a liquid storage unit 191 that stores a liquid film material (raw material liquid), a vaporizer 192 that vaporizes the liquid film material to change it into a gaseous state, and stores a carrier gas. And a gas cylinder 193. Each of these parts and the supply port 103 of the chamber 101 are connected by a pipe 194, and a mixed gas of a gaseous film material (raw material gas) and a carrier gas is supplied from the supply port 103 into the chamber 101. It is configured to supply.

The liquid film material stored in the liquid storage unit 191 is a raw material that is polymerized by the plasma polymerization apparatus 100 to form a polymer film on the surface of the first optical component 2.
Such a liquid film material is vaporized by the vaporizer 192 and is supplied into the chamber 101 as a gaseous film material (raw material gas). The source gas will be described in detail later.
The carrier gas stored in the gas cylinder 193 is a gas that is discharged due to the action of an electric field and introduced to maintain this discharge. Examples of such a carrier gas include Ar gas and He gas.

A diffusion plate 195 is provided near the supply port 103 in the chamber 101.
The diffusion plate 195 has a function of promoting the diffusion of the mixed gas supplied into the chamber 101. Thereby, the mixed gas can be dispersed in the chamber 101 with a substantially uniform concentration.

The exhaust pump 170 exhausts the inside of the chamber 101, and includes, for example, an oil rotary pump, a turbo molecular pump, or the like. Thus, by exhausting the chamber 101 and reducing the pressure, the gas can be easily converted into plasma. In addition, contamination and oxidation of the first optical component 2 due to contact with the air atmosphere can be prevented, and reaction products resulting from the plasma treatment can be effectively removed from the chamber 101.
The exhaust port 104 is provided with a pressure control mechanism 171 that adjusts the pressure in the chamber 101. Thereby, the pressure in the chamber 101 is appropriately set according to the operation state of the gas supply unit 190.

Next, a method for producing the bonding film 3 on the first optical component 2 using the plasma polymerization apparatus 100 will be described.
FIG. 6 is a view (longitudinal sectional view) for explaining a method of producing the bonding film 3 on the first optical component 2. In the following description, the upper side in FIG. 6 is referred to as “upper” and the lower side is referred to as “lower”.
The bonding film 3 is obtained by supplying a mixed gas of a source gas and a carrier gas in a strong electric field, thereby polymerizing molecules in the source gas and depositing the polymer on the first optical component 2. be able to. Details will be described below.

First, the first optical component 2 is prepared, and the surface treatment as described above is performed on the upper surface 25 of the first optical component 2 as necessary.
Next, after the first optical component 2 is housed in the chamber 101 of the plasma polymerization apparatus 100 and sealed, the chamber 101 is depressurized by the operation of the exhaust pump 170.

Next, the gas supply unit 190 is operated to supply a mixed gas of the source gas and the carrier gas into the chamber 101. The supplied mixed gas is filled in the chamber 101 (see FIG. 6A).
Here, the ratio (mixing ratio) of the source gas in the mixed gas is slightly different depending on the type of the source gas and the carrier gas, the target film forming speed, and the like. For example, the ratio of the source gas in the mixed gas is 20 It is preferable to set to about -70%, and it is more preferable to set to about 30-60%. As a result, it is possible to optimize the conditions for formation (film formation) of the polymer film.

Next, the power supply circuit 180 is activated, and a high frequency voltage is applied between the pair of electrodes 130 and 140. As a result, gas molecules existing between the pair of electrodes 130 and 140 are ionized to generate plasma. The molecules in the source gas are polymerized by the energy of the plasma, and the polymer adheres to and deposits on the first optical component 2 as shown in FIG. As a result, a bonding film 3 made of a plasma polymerized film is formed on the first optical component 2 (see FIG. 6C).
Further, the surface of the first optical component 2 is activated and cleaned by the action of plasma. For this reason, the polymer of the source gas is easily deposited on the surface of the first optical component 2, and the bonding film 3 can be stably formed. As described above, according to the plasma polymerization method, the adhesion strength between the first optical component 2 and the bonding film 3 can be further increased regardless of the constituent material of the first optical component 2.

Examples of the source gas include organosiloxanes such as methylsiloxane, octamethyltrisiloxane, decamethyltetrasiloxane, decamethylcyclopentasiloxane, octamethylcyclotetrasiloxane, and methylphenylsiloxane.
The plasma polymerized film obtained by using such a raw material gas, that is, the bonding film 3 is composed of a polymer obtained by polymerizing these raw materials, that is, a polyorganosiloxane.

In the plasma polymerization, the frequency of the high frequency applied between the pair of electrodes 130 and 140 is not particularly limited, but is preferably about 1 kHz to 100 MHz, and more preferably about 10 to 60 MHz.
Further, the power density of the high frequency is not particularly limited, and is preferably about 0.01~100W / cm ^2, more preferably about ^{0.1~50W / cm 2, 1~40W / cm} 2 More preferably, it is about. By setting the high-frequency power density within the above range, the Si skeleton 301 having a random atomic structure can be reliably secured while preventing the plasma gas from being added to the source gas more than necessary because the high-frequency power density is too high. Can be formed. That is, when the high-frequency output density is lower than the lower limit value, the molecules in the raw material gas cannot cause a polymerization reaction, and the bonding film 3 may not be formed. On the other hand, when the power density of the high frequency exceeds the upper limit, the structure that can be the leaving group 303 is separated from the Si skeleton 301 due to decomposition of the source gas or the like, and the leaving group in the resulting bonding film 3 is separated. There is a possibility that the content of 303 is lowered or the randomness of the Si skeleton 301 is lowered (regularity is increased).

Further, the pressure in the chamber 101 during film formation is preferably about 133.3 × 10 ^{−5 to} 1333 Pa (1 × 10 ^{−5 to} 10 Torr), and 133.3 × 10 ^{−4 to} 133.3 Pa ( More preferably, it is about 1 × 10 ^{−4 to} 1 Torr).
The raw material gas flow rate is preferably about 0.5 to 200 sccm, and more preferably about 1 to 100 sccm. On the other hand, the carrier gas flow rate is preferably about 5 to 750 sccm, and more preferably about 10 to 500 sccm.

The treatment time is preferably about 1 to 10 minutes, more preferably about 4 to 7 minutes.
Moreover, it is preferable that the temperature of the 1st optical component 2 is 25 degreeC or more, and it is more preferable that it is about 25-100 degreeC.
The bonding film 3 is obtained as described above.

  Here, in the present invention, when the bonding film 3 is formed, the film forming conditions (high frequency output, high frequency, source gas flow rate, source gas type, etc.) are gradually changed within the above ranges. The refractive index of the bonding film 3 to be formed is adjusted according to the refractive index of each optical component 2, 4. Specifically, the bonding film 3 in which the refractive index in the thickness direction is changed so as to connect the refractive index of the first optical component 2 and the refractive index of the second optical component 4 is formed.

  According to such a bonding film 3, it is possible to prevent a significant refractive index difference from occurring between the first optical component 2 and the second optical component 4 and smoothly connect the refractive index difference. Therefore, the light scattering accompanying the refractive index difference can be suppressed. For this reason, light loss at the bonding interface between the first optical component 2 and the bonding film 3 and the bonding interface between the bonding film 3 and the second optical component 4 is suppressed, and the transmittance of light transmitted through this interface is increased. be able to.

  As a method for adjusting the refractive index, for example, the bonding film 3 having a higher refractive index can be obtained by increasing the high-frequency output. On the other hand, the bonding film 3 having a lower refractive index can be obtained by reducing the high-frequency output. That is, since a certain correlation is obtained between the high-frequency output and the refractive index of the bonding film 3, the high-frequency output is adjusted so that the refractive index of the bonding film 3 becomes a desired value using this relationship. Adjust the output. One reason why the refractive index of the bonding film 3 can be adjusted in this way is that the amount or film density of the organic component remaining in the plasma polymerization film changes according to the output of the high frequency, and this organic component It is considered that the amount and the film density affect the refractive index. Note that the high-frequency output is a suitable control factor from the viewpoint of strictly adjusting the refractive index because it is a parameter that can be easily adjusted and can be accurately adjusted even under film formation conditions.

Therefore, in order to form the bonding film 3 whose refractive index in the thickness direction is changed so as to connect the refractive index of the first optical component 2 and the refractive index of the second optical component 4, first, refraction is performed. The high frequency output is set so that the rate is the same as that of the first optical component 2, and the film formation of the bonding film 3 is started. The high frequency output is gradually changed as the film formation proceeds. The rate of change at this time depends on factors such as the deposition rate of the bonding film 3, the target thickness of the bonding film 3, and the refractive index difference between the first optical component 2 and the second optical component 4. Is set. Due to such a change in the high frequency output, the bonding film 3 is formed and the refractive index thereof continuously changes. Then, when the deposition of the bonding film 3 is finished, the high frequency output is changed so that the refractive index is the same as that of the second optical component 4.
Further, the refractive index of the bonding film 3 can be adjusted by appropriately adjusting the conditions other than the high-frequency output so that the plasma density during film formation changes. Specifically, the plasma density during film formation can be increased by increasing the frequency of the high frequency and the flow rate of the source gas.

In the present embodiment, the bonding film 3 whose refractive index is continuously changed so as to connect the refractive index of the first optical component 2 and the refractive index of the second optical component 4 is described. The change in refractive index may be discontinuous or stepwise.
Further, the obtained bonding film 3 can be more strictly controlled if its refractive index is in the range of about 1.35 to 1.6. For this reason, the adjustment range of the refractive index can be increased, and the bonding film 3 in which the refractive index is changed so as to match the refractive index of many types of optical components can be obtained.
In addition, since the thermal expansion coefficient of the bonding film 3 is close to the thermal expansion coefficient of quartz or quartz glass, the difference in thermal expansion coefficient between each optical component and the bonding film 3 is reduced, and the laminated optical element 5 after bonding is deformed. Can be suppressed.

<< Second Embodiment >>
Next, a second embodiment of the optical element manufacturing method of the present invention will be described.
FIG. 7 is a view (longitudinal sectional view) for explaining a second embodiment of the method for producing an optical element of the present invention. In the following description, the upper side in FIG. 7 is referred to as “upper” and the lower side is referred to as “lower”.
Hereinafter, although the manufacturing method of the optical element concerning 2nd Embodiment is demonstrated, it demonstrates centering around difference with the said 1st Embodiment, The description is abbreviate | omitted about the same matter.

In the method of manufacturing an optical element according to this embodiment, a bonding film is formed on the surface of each optical component 2, 4, and each optical component 2, 4 is bonded so that the bonding films are in close contact with each other. Except for this, it is the same as the first embodiment.
That is, in the method for manufacturing an optical element according to the present embodiment, the first optical component 2 and the second optical component 4 are prepared, and the bonding film 31 is formed on the surface of the first optical component 2 by plasma polymerization. And the step of forming the bonding film 32 on the surface of the second optical component 4, the step of applying energy to the bonding films 31, 32, and the bonding films 31, 32 are in close contact with each other. Thus, the first optical component 2 and the second optical component 4 are bonded together to obtain a laminated optical element 5a. Hereafter, each process of the manufacturing method of the optical element concerning this embodiment is demonstrated sequentially.

[1] First, as in the first embodiment, the first optical component 2 and the second optical component 4 are prepared, and the bonding film 31 is formed on the surfaces of the optical components 2 and 4 by plasma polymerization. , 32 are formed (see FIG. 7A). At this time, the film forming conditions of the bonding films 31 and 32 are different from each other.
Specifically, the bonding film 31 is formed under film forming conditions such that the refractive index thereof is close to the refractive index of the first optical component 2, and the bonding film 32 has a refractive index of the second refractive index. The film is formed under film forming conditions that are close to the refractive index of the optical component 4.
The film formation conditions during the formation of each of the bonding films 31 and 32 may be constant or may change over time.

  When the film formation conditions during film formation are constant, the film formation conditions for forming the two-layer bonding films 31 and 32 are such that the refractive index of the two-layer bonding films 31 and 32 is the first optical layer. The refractive index of the bonding film 31 is between the refractive index of the component 2 and the refractive index of the second optical component 4, and the refractive index of the bonding film 32 is on the refractive index side of the first optical component 2. It is set to be on the refractive index side of the second optical component 4.

[2] Next, as shown in FIG. 7B, energy is applied to each of the bonding films 31 and 32.
When energy is applied, the leaving group 303 is detached from the Si skeleton 301 on the surfaces of the bonding films 31 and 32. Since an active hand is generated after the leaving group 303 is removed, stable adhesiveness to the second optical component 4 is expressed in the bonding film 3. As a result, the bonding film 3 can be stably and firmly bonded to the second optical component 4 based on chemical bonding.

[3] Next, as shown in FIG. 7 (c), the first optical component 2 and the second optical component 4 are pasted so that the bonding films 31 and 32 exhibiting adhesiveness are in close contact with each other. Match. Thereby, as shown in FIG.7 (d), the laminated optical element 5a is obtained.
Here, in this step, the bonding films 31 and 32 are bonded to each other, and this bonding is assumed to be based on both or one of the following two mechanisms (i) and (ii). .

(I) For example, the case where hydroxyl groups are exposed on the surfaces 351 and 352 of the bonding films 31 and 32 will be described as an example. In this step, the first films 31 and 32 may be in close contact with each other. When the optical component 2 and the second optical component 4 are bonded together, the hydroxyl groups present on the surfaces 351 and 352 of the bonding films 31 and 32 attract each other by hydrogen bonding, and an attractive force is generated between the hydroxyl groups. . It is inferred that the first optical component 2 and the second optical component 4 are joined by this attractive force.
Further, the hydroxyl groups attracting each other by this hydrogen bond are dehydrated and condensed depending on the temperature condition or the like. As a result, between the bonding films 31 and 32, the bonds in which the hydroxyl groups are bonded are bonded via oxygen atoms. Thereby, it is guessed that the 1st optical component 2 and the 2nd optical component 4 are joined more firmly.

  (Ii) When the first optical component 2 and the second optical component 4 are bonded so that the bonding films 31 and 32 are in close contact with each other, they are generated on the surfaces 351 and 352 of the bonding films 31 and 32 or inside thereof. Bonds that are not terminated (unbonded hands) rejoin. Since this recombination occurs in a complicated manner so as to overlap (entangle) with each other, a network-like bond is formed at the bonding interface. As a result, the respective base materials (Si skeleton 301) constituting the bonding films 31 and 32 are directly bonded to each other, and the bonding films 31 and 32 are integrated with each other.

By the mechanism (i) or (ii) as described above, a laminated optical element 5a (the optical element of the present invention) as shown in FIG. 7D is obtained.
In the laminated optical element 5a thus obtained, the refractive index in the thickness direction is the refractive index of the first optical component 2 and the refractive index of the second optical component 4 throughout the bonding film 31 and the bonding film 32. It is changing to connect the rate. For this reason, the laminated optical element 5a has the same operations and effects as the laminated optical element 5 in the first embodiment described above.
In the present embodiment, the case where two layers of bonding films 31 and 32 are provided between the first optical component 2 and the second optical component 4 has been described. However, three or more layers of bonding films are provided. May be.

The optical element manufacturing method according to each of the embodiments as described above can be used to join various optical components together.
Examples of optical components used for such bonding include optical lenses, diffraction gratings, optical filters, protective plates, photoelectric conversion elements such as solar cells, optical recording media such as optical disks, and liquid crystal display elements. And display elements such as organic EL elements and electrophoretic display elements.

<Optical element>
Here, an embodiment in which the optical element of the present invention is applied to a wave plate will be described.
FIG. 8 is a perspective view showing a wave plate (optical element) obtained by applying the optical element of the present invention.
The wave plate 9 shown in FIG. 8 is a “½ wave plate” that gives a phase difference of ½ wavelength to transmitted light, and two crystal plates 91 and 92 having birefringence are respectively provided. Are bonded so that their optical axes are orthogonal to each other. Examples of the birefringent material include inorganic materials such as quartz, calcite, MgF ₂ , YVO ₄ , TiO ₂ , and LiNbO ₃ , and organic materials such as polycarbonate. Two crystal plates 91 and 92 Have different refractive indexes.
When light passes through such a wave plate 9, the light is separated into a polarization component parallel to the optical axis and a polarization component perpendicular to the optical axis. The separated light is delayed on one side based on the refractive index difference associated with the birefringence of the crystal plates 91 and 92, and the phase difference described above is generated.

By the way, since the accuracy of the phase difference given to the transmitted light by the wave plate 9 and the transmittance of the wave plate 9 depend on the accuracy of the plate thickness of each crystal plate 91, 92, the plate of each crystal plate 91, 92. The thickness needs to be controlled with high accuracy.
In addition, since the gap between the crystal plate 91 and the crystal plate 92 also affects the phase of transmitted light, the gap between the crystal plate 91 and the crystal plate 92 is strictly controlled, and the gap is It must be firmly bonded so that it does not change.

Therefore, in the present invention, the optical element of the present invention is applied to the wave plate 9. Thereby, the wave plate 9 in which the crystal plate 91 and the crystal plate 92 are firmly bonded via the bonding film can be easily obtained.
Further, since this bonding film can be formed in a wide area at once by a vapor phase film forming method called a plasma polymerization method, it can be formed uniformly and the film thickness is highly accurate. For this reason, the wave plate 9 having a high degree of parallelism between the crystal plate 91 and the crystal plate 92 and less aberrations such as wavefront aberration is obtained.

Furthermore, the refractive index of the bonding film changes in the thickness direction so as to connect the refractive index of the crystal plate 91 and the refractive index of the crystal plate 92. Therefore, light scattering at the bonding interface between the crystal plate 91 and the bonding film 3 and the bonding interface between the bonding film 3 and the crystal plate 92 can be suppressed, and the light transmittance of the wave plate 9 can be increased.
The wave plate 9 may be a quarter wave plate, a 1/8 wave plate or the like in addition to the half wave plate.
Examples of the optical element include an optical filter such as a polarizing filter, a compound lens such as an optical pickup, a prism, a diffraction grating, and the like in addition to the wave plate.

As mentioned above, although the optical element of this invention and the manufacturing method of the optical element were demonstrated based on embodiment of illustration, this invention is not limited to these.
For example, the optical element manufacturing method of the present invention may be any one or a combination of two or more of the above embodiments.
Moreover, in the method for manufacturing an optical element of the present invention, one or more optional steps may be added as necessary.

In each of the above-described embodiments, the method of joining two optical components, the first optical component 2 and the second optical component 4, has been described. You may make it use the manufacturing method of the optical element of invention.
In each of the above embodiments, the bonding film is formed on the entire surface of each optical component. However, the bonding film may be formed only on a part thereof. In this case, by appropriately adjusting the bonding region, stress concentration at the bonding interface can be relaxed, and problems such as deformation of the optical element or peeling of the bonding interface can be prevented. Further, since a gap is formed between the two optical components, the optical component can be forcibly cooled by flowing a gas such as air through the gap, for example.
Furthermore, in each of the embodiments described above, energy is applied to the entire surface of the bonding film so as to develop the adhesiveness. However, the adhesiveness may be developed only in a part. Also in this case, by appropriately adjusting the bonding region, stress concentration at the bonding interface can be relaxed, and problems such as deformation of the optical element or peeling of the bonding interface can be prevented.

Next, specific examples of the present invention will be described.
1. Production of Laminated Optical Element In the following, a plurality of laminated optical elements were produced in each reference example, each example, and comparative example.

1.1 Production of Reference Example (Reference Example 1)
First, a quartz substrate having a length of 20 mm × width 20 mm × an average thickness of 2 mm was prepared as a first optical component, and a crystal substrate having a length of 20 mm × width 20 mm × an average thickness of 1 mm was prepared as a second optical component. . Note that these quartz substrates are all subjected to optical polishing. Moreover, the refractive index with respect to the light of wavelength 546nm of the used quartz substrate was 1.546.
Next, each substrate was accommodated in the chamber 101 of the plasma polymerization apparatus 100 shown in FIG. 5, and surface treatment with oxygen plasma was performed.

Next, a plasma polymerization film having an average thickness of 150 nm was formed on the surface subjected to the surface treatment. The film forming conditions are as shown below.
<Film formation conditions>
-Source gas composition: Octamethyltrisiloxane-Source gas flow rate: 10 sccm
Carrier gas composition: Argon Carrier gas flow rate: 10 sccm
・ High frequency power output: 100W
・ High frequency output density: 25 W / cm ²
-Chamber pressure: 1 Pa (low vacuum)
・ Processing time: 215 seconds ・ Substrate temperature: 20 ° C.
Thereby, a plasma polymerization film was formed on each substrate.

  The plasma polymerized film thus formed is composed of a polymer of octamethyltrisiloxane (raw material gas), and includes a Si skeleton including a siloxane bond and a random atomic structure, and an alkyl group (desorbed). Group). Further, the crystallinity of the plasma polymerized film was measured by an infrared absorption method. As a result, the degree of crystallinity of the plasma polymerized film was 30% or less although there was some variation depending on the measurement location.

Next, each plasma polymerization film obtained was subjected to plasma treatment under the following conditions.
<Plasma treatment conditions>
・ Plasma treatment method: Direct plasma method ・ Process gas composition: Helium gas ・ Atmospheric pressure: Atmospheric pressure (100 kPa)
・ Distance between electrodes: 1mm
・ Applied voltage: 1 kVp-p
-Voltage frequency: 40 MHz
Next, one minute after applying the plasma treatment, the respective substrates were overlapped so that the plasma polymerization films were in contact with each other. Thereby, a laminated optical element was obtained.
Then, the refractive index with respect to the light of wavelength 546nm was measured about the joining film in the obtained laminated optical element.

(Reference Example 2)
A laminated optical element was obtained in the same manner as in Example 1 except that the high frequency power for forming the plasma polymerized film was changed to 150 W.
(Reference Example 3)
A laminated optical element was obtained in the same manner as in Example 1 except that the high frequency power for forming the plasma polymerized film was changed to 200 W.

(Reference Example 4)
A laminated optical element was obtained in the same manner as in Example 1 except that the high frequency power for forming the plasma polymerized film was changed to 250 W.
(Reference Example 5)
A laminated optical element was obtained in the same manner as in Example 1 except that the high frequency power for forming the plasma polymerized film was changed to 300 W.

(Reference Example 6)
A laminated optical element was obtained in the same manner as in Example 1 except that the high frequency power for forming the plasma polymerized film was changed to 325 W.
(Reference Example 7)
A laminated optical element was obtained in the same manner as in Example 1 except that the high frequency power for forming the plasma polymerized film was changed to 350 W.

1.2 Evaluation of Reference Examples About the bonding films in the laminated optical elements obtained in the respective reference examples, when the respective refractive indexes were compared, by gradually increasing the high-frequency output when forming the plasma polymerization film, It was observed that the refractive index gradually increased. Specifically, it was recognized that the high-frequency output and the refractive index are in a substantially proportional relationship. From this, it was confirmed that the refractive index of the bonding film can be adjusted by adjusting the film formation conditions of the plasma polymerization film.
In addition, Table 1 shows manufacturing conditions and evaluation results of the laminated optical elements obtained in the respective reference examples.

Next, based on the evaluation results of the respective reference examples, the laminated optical element according to the example was manufactured.
1.3 Production of Examples (Example 1)
First, a quartz substrate having a length of 20 mm × width 20 mm × average thickness 2 mm is prepared as a first optical component, and a quartz glass plate having a length 20 mm × width 20 mm × average thickness 1 mm is prepared as a second optical component. did. Note that these quartz substrate and quartz glass substrate are both subjected to optical polishing. Moreover, the refractive index with respect to the light of wavelength 546nm of the used quartz substrate was 1.546, and the refractive index with respect to the light of wavelength 546nm of a quartz glass substrate was 1.460.
Next, each substrate was accommodated in the chamber 101 of the plasma polymerization apparatus 100 shown in FIG. 5, and surface treatment with oxygen plasma was performed.

Next, a plasma polymerization film having an average thickness of 300 nm was formed on the surface of the quartz substrate that had been subjected to the surface treatment. The film forming conditions are as shown below.
<Film formation conditions>
-Source gas composition: Octamethyltrisiloxane-Source gas flow rate: 10 sccm
Carrier gas composition: Argon Carrier gas flow rate: 10 sccm
・ High frequency power output: 325W → 100W
・ High frequency output density: 25 W / cm ²
-Chamber pressure: 1 Pa (low vacuum)
-Processing time: 430 seconds-Substrate temperature: 20 ° C

Thereby, a plasma polymerization film was formed on the quartz substrate. Note that the high-frequency output was gradually decreased after film formation was started at 325 W, and was decreased to 100 W at the end of film formation.
The plasma polymerized film thus formed is composed of a polymer of octamethyltrisiloxane (raw material gas), and includes a Si skeleton including a siloxane bond and a random atomic structure, and an alkyl group (desorbed). Group). Further, the crystallinity of the plasma polymerized film was measured by an infrared absorption method. As a result, the degree of crystallinity of the plasma polymerized film was 30% or less although there was some variation depending on the measurement location.

Next, the obtained plasma polymerization film was subjected to plasma treatment under the following conditions.
<Plasma treatment conditions>
・ Plasma treatment method: Direct plasma method ・ Process gas composition: Helium gas ・ Atmospheric pressure: Atmospheric pressure (100 kPa)
・ Distance between electrodes: 1mm
・ Applied voltage: 1 kVp-p
-Voltage frequency: 40 MHz
Next, one minute after applying the plasma treatment, the substrates were overlapped so that the plasma polymerized film and the quartz glass substrate were in contact with each other. Thereby, a laminated optical element was obtained.
Then, the refractive index with respect to the light of wavelength 546nm was measured about the joining film in the obtained laminated optical element.

(Example 2)
Except that the plasma polymerized film was formed on both the quartz substrate and the quartz glass substrate as described below, and the substrates were overlapped so that the plasma polymerized films were in close contact with each other to obtain a laminated optical element. A laminated optical element was obtained in the same manner as in Example 1.
First, a plasma polymerization film was formed on the surface of the quartz substrate that had been subjected to the surface treatment by changing the film forming conditions from those in Example 1. As a change point of the film forming conditions, the processing time was 215 seconds, and the high frequency output was gradually decreased from 325 W to 200 W. Moreover, the average thickness of the obtained plasma polymerization film | membrane was 150 nm.
On the other hand, a plasma polymerized film was formed on the surface subjected to the surface treatment of the quartz glass substrate by changing the film forming conditions from those in Example 1. As a change point of the film forming conditions, the processing time was 215 seconds, and the high frequency output was gradually increased from 100 W to 200 W. Moreover, the average thickness of the obtained plasma polymerization film | membrane was 150 nm.
Then, each plasma polymerized film was subjected to a plasma treatment in the same manner as in Example 1, and then the substrates were overlapped so that the plasma polymerized films were in close contact with each other to obtain a laminated optical element.
(Comparative example)
A laminated optical element was obtained in the same manner as in the above example, except that the first optical component and the second optical component were bonded using an epoxy-based optical adhesive (average thickness: 3 μm).

2. 2. Evaluation of Laminated Optical Element 2.1 Evaluation of Bonding Strength (Split Strength) With respect to the laminated optical elements obtained in the examples and comparative examples, the bonding strength was measured.
The bonding strength was measured by measuring the strength immediately before peeling off each substrate. Further, the measurement of the bonding strength was performed immediately after bonding and after repeating the temperature cycle of −40 ° C. to 125 ° C. 100 times after bonding.
As a result, the laminated optical element obtained in each example had sufficient bonding strength both immediately after bonding and after temperature cycling.
On the other hand, the laminated optical element obtained in the comparative example had a sufficient bonding strength immediately after bonding, but the bonding strength decreased after the temperature cycle.

2.2 Evaluation of Dimensional Accuracy The dimensional accuracy (parallelism) in the thickness direction was measured for each of the laminated optical elements obtained in each Example and Comparative Example.
Specifically, the thickness of the four corners of the laminated optical element was measured with a micro gauge. And the relative inclination of both surfaces of a laminated optical element was computed based on the difference of the thickness of four corners.
As a result, the laminated optical elements obtained in the respective examples had a parallelism of ± 1 second or less, and the variation in the parallelism was small among a plurality of laminated optical elements.
On the other hand, the laminated optical element obtained in the comparative example had a parallelism of ± 1 second or more, and the variation in the parallelism was large among a plurality of laminated optical elements.

2.3 Evaluation of light transmittance The light transmittance in the thickness direction of each of the laminated optical elements obtained in each of the examples and the comparative examples was measured. The light transmittance was measured after irradiating light with a wavelength of 546 nm and an output of 100 mW continuously in a 70 ° C. environment for 1000 hours. Then, the measured light transmittance was evaluated according to the following evaluation criteria.

<Evaluation criteria for light transmittance>
A: Light transmittance is 99.8% or more. B: Light transmittance is 99.0% or more and less than 99.8%. Δ: Light transmittance is 98.0% or more and less than 99.0%. Less than 0% Table 2 shows the evaluation results of light transmittance.

As is clear from Table 2, the laminated optical elements obtained in the respective examples had a light transmittance of 99% or more and good light transmittance. On the other hand, the laminated optical element obtained in the comparative example had sufficient light transmittance immediately after the start of light transmission, but after 1000 hours, the light transmittance became less than 98%, and the light transmittance decreased. It was.
Such a result shows that the refractive index of the bonding film in the laminated optical element obtained in each example changes so as to connect the refractive index of the quartz substrate and the refractive index of the quartz glass substrate. This is presumably due to the suppression of light scattering at each bonding interface.

2.4 Evaluation of Appearance For the laminated optical elements obtained in the examples and comparative examples, light having a wavelength of 405 nm and an output of 100 mW was continuously irradiated in a 70 ° C. environment for 1000 hours, and then the appearance of the irradiated portion was evaluated as follows. Evaluation was made according to criteria.
<Evaluation criteria for appearance>
A: No discoloration or bubbles are observed at the bonding interface. B: Slight dot discoloration or bubbles are observed at the bonding interface. Δ: Many dot discolorations or bubbles are observed at the bonding interface. X: Layered at the bonding interface. Table 2 shows the evaluation results of the appearance in which many discolorations or bubbles are observed.
As is clear from Table 2, in the laminated optical element obtained in each example, no discoloration or bubbles were observed at the bonding interface. On the other hand, in the laminated optical element obtained in the comparative example, discoloration was observed in the optical path portion.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view (longitudinal sectional view) for explaining a first embodiment of a method for producing an optical element of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view (longitudinal sectional view) for explaining a first embodiment of a method for producing an optical element of the present invention. In the manufacturing method of the optical element of this invention, it is the elements on larger scale which show the state before energy provision of a joining film | membrane. In the manufacturing method of the optical element of this invention, it is the elements on larger scale which show the state after the energy provision of a joining film | membrane. It is a longitudinal cross-sectional view which shows typically the plasma polymerization apparatus used for the manufacturing method of the optical element of this invention. It is a figure (longitudinal sectional view) for demonstrating the method of producing a joining film | membrane on the 1st optical component. It is a figure (longitudinal sectional view) for demonstrating 2nd Embodiment of the manufacturing method of the optical element of this invention. It is a perspective view which shows the wavelength plate (optical element) obtained by applying the optical element of this invention.

Explanation of symbols

  2... First optical component 25... Upper surface 3, 31, 32 .. Bonding film 301... Si skeleton 302... Siloxane bond 303 ... Leaving group 304 ... Active hand 35, 351, 352. 4 ... Second optical component 5, 5a ... Laminated optical element 100 ... Plasma polymerization apparatus 101 ... Chamber 102 ... Ground wire 103 ... Supply port 104 ... Exhaust port 130 ... First electrode 139 ... ... electrostatic chuck 140 ... second electrode 170 ... pump 171 ... pressure control mechanism 180 ... power supply circuit 182 ... high frequency power supply 183 ... matching box 184 ... wiring 190 ... gas supply unit 191 ... storage Liquid part 192 …… Vaporizer 193 …… Gas cylinder 194 …… Piping 195 …… Diffusion plate 9 …… Wave plate 91, 92 …… Crystal plate

Claims (25)

A first optical component and a second optical component having optical transparency, a Si skeleton formed by a plasma polymerization method and having a random atomic structure including a siloxane (Si—O) bond, and bonded to the Si skeleton A bonding film that bonds the first optical component and the second optical component,
Energy is applied to at least a partial region of the bonding film, and the leaving group present on the surface of the bonding film is detached from the Si skeleton, thereby causing the first adhesion to occur in the bonding film. The first optical component and the second optical component are joined,
The optical element, wherein the bonding film has a portion whose refractive index changes continuously or stepwise along the thickness direction.   2. The optical element according to claim 1, wherein a sum of a content ratio of Si atoms and a content ratio of O atoms among atoms obtained by removing H atoms from all atoms constituting the bonding film is 10 to 90 atomic%.   The optical element according to claim 1, wherein the abundance ratio of Si atoms to O atoms in the bonding film is 3: 7 to 7: 3.   The optical element according to claim 1, wherein the crystallinity of the Si skeleton is 45% or less.   The optical element according to claim 1, wherein the bonding film includes a Si—H bond.   In the infrared light absorption spectrum of the bonding film including the Si—H bond, when the peak intensity attributed to the siloxane bond is 1, the peak intensity attributed to the Si—H bond is 0.001 to 0.2. The optical element according to claim 5.   The leaving group includes an H atom, a B atom, a C atom, an N atom, an O atom, a P atom, an S atom, and a halogen atom, or an atomic group arranged so that each of these atoms is bonded to the Si skeleton. The optical element according to claim 1, wherein the optical element is composed of at least one selected from the group consisting of:   The optical element according to claim 7, wherein the leaving group is an alkyl group.   In the infrared light absorption spectrum of the bonding film containing a methyl group as the leaving group, when the peak intensity attributed to the siloxane bond is 1, the peak intensity attributed to the methyl group is 0.05 to 0.45. The optical element according to claim 8.   The optical element according to claim 1, wherein the bonding film has an active hand after the leaving group existing at least near the surface thereof is detached from the Si skeleton.   The optical element according to claim 10, wherein the active hand is a dangling bond or a hydroxyl group.   The optical element according to claim 1, wherein the bonding film is composed of polyorganosiloxane as a main material.   The optical element according to claim 12, wherein the polyorganosiloxane is mainly composed of a polymer of octamethyltrisiloxane. In the plasma polymerization method, the power density of the high frequency at the time of generating plasma, the optical element according to any one of claims 1 to 13 is 0.01~100W / cm ^2.   The optical element according to claim 1, wherein an average thickness of the bonding film is 1-1000 nm.   The optical element according to claim 1, wherein the bonding film is a solid having no fluidity.   The optical element according to claim 1, wherein a refractive index of the bonding film is in a range of 1.35 to 1.6.   The optical element according to claim 1, wherein the application of energy is performed by at least one of a method of irradiating the bonding film with energy rays and a method of exposing the bonding film to plasma. .   The optical element according to claim 18, wherein the energy beam is an ultraviolet ray having a wavelength of 126 to 300 nm.   The optical element according to claim 18, wherein the plasma exposed to the bonding film is atmospheric pressure plasma.   21. The optical element according to claim 1, wherein each of the first optical component and the second optical component is made of quartz glass or quartz. The refractive index of the first optical component is different from the refractive index of the second optical component;
The optical element according to claim 1, wherein a refractive index of the bonding film changes so as to connect a refractive index of the first optical component and a refractive index of the second optical component. The bonding film is a film in which the refractive index is changed continuously or stepwise along the thickness direction by gradually changing the film forming conditions when forming the film.
The optical element according to claim 1, wherein the film forming condition is a high frequency output. Between the first optical component and the second optical component, there are two or more bonding films similar to the bonding film,
The optical element according to any one of claims 1 to 23, wherein the entire bonding film of two or more layers has a portion whose refractive index changes continuously or stepwise along the thickness direction. A first optical component and a second optical component that have optical transparency and can be bonded to each other through a bonding film are prepared, and plasma is formed on the surface of the first optical component. A first step of forming the bonding film including a Si skeleton having a random atomic structure including a siloxane (Si-O) bond and a leaving group bonded to the Si skeleton by a polymerization method;
A second step of applying energy to the bonding film to desorb the leaving group present in the bonding film from the Si skeleton and to exhibit adhesiveness;
A third step of bonding the first optical component and the second optical component via the bonding film to obtain an optical element;
In the plasma polymerization method of the first step, the refractive index of the bonding film is continuously or stepwise along the thickness direction by gradually changing the film forming conditions while forming the bonding film. A method for manufacturing an optical element, characterized in that the adjustment is performed so as to change.

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