JP3449593B2 - Optical material and optical waveguide using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical material that can be used for a waveguide type optical component such as an optical integrated circuit and an optical waveguide formed of the optical material. It can be used for various optical components, optical integrated circuits, optical wiring boards, etc. used in the fields of optical communication and optical information processing.

[0002]

2. Description of the Related Art A polymer material is easy to form a thin film by a spin coating method or a dipping method, and is suitable for producing an optical component having a large area. Further, since the heat treatment step at high temperature is not included in the film formation, the film is formed on a substrate such as a semiconductor substrate or a plastic substrate which cannot withstand the heat treatment at high temperature as compared with the case of using an inorganic glass material such as quartz. There is an advantage that an optical waveguide can be manufactured. Furthermore, it is possible to fabricate a flexible optical waveguide that takes advantage of the flexibility and toughness of a polymer. For these reasons, it is expected that optical waveguide components such as optical integrated circuits used in the field of optical communication and optical wiring boards used in the field of optical information processing can be mass-produced at low cost using polymer optical materials. ing.

On the other hand, polymer optical materials have been conventionally (1)
Environmental resistance such as heat resistance or moisture resistance, (2) transparency that enables low loss of optical components in the optical communication wavelength band (visible region to near infrared region), and (3) waveguide manufacturing process and guide It has been said that there is a problem in that cracks are generated which lowers the yield when the waveguide component is used.

With respect to the problems (1) environment resistance and (2) transparency described above, in recent years, materials have been invented and reported which have greatly improved them. For example, Japanese Patent Laid-Open No. 3-4
The material disclosed in 3423 is a polymer material having a silsesquioxane structure as a molecular skeleton and has excellent heat resistance. In addition, the phenyl group and the alkyl group of the side chain are hydrophobic and have high moisture resistance. Furthermore, C- contained in the side chain
The hydrogen of the H bond is replaced with halogen or deuterium, and the absorption in the near infrared region due to the overtone or the bond sound of the stretching or bending vibration of the C—H bond is significantly reduced,
Two major communication wavelengths (1.3 μm and 1.55 μ
In the 1.3 μm band of m), a considerably low loss was achieved.

Explaining (3) the problem of crack generation during the waveguide manufacturing process and the use of the waveguide component, the crack is generated by the stress generated in the polymer thin film, and the larger the film thickness, the higher the probability of occurrence. When manufacturing an optical waveguide having a core / clad structure, it is necessary to form a thin film having a certain thickness or more. For example, a single mode optical waveguide in which the cross section of the core is a square of 8 μm square is used. When formed on a silicon substrate, a film thickness of about 15 μm or more is required for the lower cladding in order to avoid the influence of metal cladding. Here, metal cladding means that when the thickness of the lower clad is thin, light guided in the core part is drawn into the silicon substrate on which the optical waveguide is formed to absorb light,
It means that the waveguide loss becomes significantly large. Also, regarding the upper clad, in order to prevent the influence of dust or dirt on the surface and the stress from the outside from affecting the light guided through the core part, a film thickness of about 8 μm or more is formed as the upper clad from the upper surface of the core. Although necessary, the problem of cracking becomes more significant as the film thickness increases. 8μ for conventional materials
Generation of cracks is recognized at a film thickness of about m. When a crack is generated, the loss increases remarkably and it cannot be used as a waveguide. In order to solve such a crack generation problem, for example, in JP-A-7-258604, a bifunctional structural unit such as a dimethylsiloxane unit is introduced into the molecular structure of the material as a structural unit that plays a role of relaxing stress. A method of doing so is disclosed.

[0006]

However, the material disclosed in Japanese Patent Laid-Open No. 3-43423 mentioned above cannot sufficiently achieve low loss in the 1.55 μm band of the two main communication wavelengths. The problem still remains.

Further, in the method disclosed in the above-mentioned JP-A-7-258604, the absorption based on the C--H bond appears in the near infrared region, and the above-mentioned near red by halogen or deuterium substitution. There is a problem that the low loss effect in the outer region becomes completely meaningless.

The present invention has been made in view of such circumstances, and an object thereof is to have excellent heat resistance and moisture resistance,
An object of the present invention is to provide an optical material that has low loss in both of the two main communication wavelengths in the near infrared region and does not cause cracks in the waveguide manufacturing process, and an optical waveguide using the optical material.

[0009]

DISCLOSURE OF THE INVENTION As a result of intensive studies to solve the above problems, the present inventors have found that a bifunctional structure to be introduced into a polysilsesquioxane optical material for imparting crack resistance. As a unit, a fluoroaralkyl type unit or a fluoroalkyl type unit mainly having a C—F bond which does not have absorption in the near infrared region is introduced instead of a conventional C—H bondable unit. Not only crack resistance in the waveguide manufacturing process, but also two main communication wavelengths in the near infrared region (1.3 μm and 1.55 μm).
found that the transparency in m) was also satisfied at the same time,
The present invention has been completed.

That is, in the conventional polysilsesquioxane-based optical material, since it is mainly composed of a trifunctional structural unit having a halogen or deuterium-substituted phenyl group in its side chain, it is in the 1.55 μm band. There is a problem that the reduction of the loss is insufficient and the frequency of crack generation due to stress is high in the waveguide manufacturing process, and in order to improve this, a material in which a bifunctional structural unit having a C—H bond is introduced. However, in the case of using C.sub.3, there was a problem that the loss at 1.3 .mu.m and 1.55 .mu.m was increased, but the present inventors, on the other hand, found that the content of C--H bond was as small as possible in fluoro-substituted alkyl or fluoro. The inventors have found that the aforementioned problems can be solved by using a material in which a substituted aralkyl unit is introduced into the molecular structure, and have completed the present invention.

The present invention is summarized as follows. The optical material according to the first aspect of the present invention has the following general formulas (I) and (II).

[0012]

[Chemical 5]

[0013]

[Chemical 6]

[0014] [wherein Z ₁ and Z ₂ represent the same or different phenyl groups or deuterium-substituted phenyl groups], and a copolymer comprising repeating units is characterized.

Further, the optical material according to the second aspect of the present invention has the following general formulas (I) and (III):

[0016]

[Chemical 7]

[0017]

[Chemical 8]

[Wherein Z ₁ represents a phenyl group or a deuterium-substituted phenyl group, and n represents a positive integer], and the copolymer is characterized by containing a repeating unit.

Further, the optical waveguide according to the third aspect of the present invention comprises a core portion made of a polymer material and a clad portion surrounding the core portion and made of a polymer material having a refractive index lower than that of the core portion. An optical waveguide comprising the core part and the clad part is characterized by containing a thermosetting material of the optical material according to the first or second aspect of the present invention.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The optical material of the present invention and the optical waveguide using the same will be described in more detail below.

First, the optical material according to the first embodiment of the present invention will be described. This optical material has the following general formula (I)
And (II)

[0022]

[Chemical 9]

[0023]

[Chemical 10]

A copolymer comprising a repeating unit represented by the formula: wherein Z ₁ and Z ₂ represent the same or different phenyl groups or deuterium-substituted phenyl groups is contained. As the raw material component from which the repeating unit (I) is derived,
Examples thereof include phenyltrichlorosilane and deuterated phenyltrichlorosilane. Repeating unit (II)
Examples of the raw material component from which 1,2-bis (hexafluoro-2-hydroxyisopropyl) benzene and the like are mentioned. The molecular weight of this copolymer is 3000
The range is up to 5000. This copolymer is not particularly limited in its production method as long as it satisfies the above-mentioned molecular structure. For example, a trifunctional compound such as phenyltrichlorosilane or deuterated phenyltrichlorosilane can be used in an aprotic solvent. A method in which a halosilane raw material is dissolved, a fluoro-substituted aryl type diol raw material is added and reacted, and then the unreacted halosilane raw material is hydrolyzed, or phenyltriethoxysilane or deuterated phenyltriethoxy is used as an alcohol solvent. Like silane 3
It can be produced by a method in which a functional alkoxysilane raw material and a fluoro-substituted aryl type diol raw material are dissolved and then an acid catalyst is added and heated. In order to construct a single mode optical waveguide by using these optical materials for a core and a clad, two types of raw material components with different refractive indexes are required. Such refractive index control is achieved by mixing two types of raw materials. This can be done by precisely adjusting the ratio.

Next, the optical material according to the second embodiment of the present invention will be described. This optical material has the following general formula (I)
And (III)

[0026]

[Chemical 11]

[0027]

[Chemical 12]

The copolymer contains a repeating unit represented by the formula: wherein Z ₁ is a phenyl group or a deuterium-substituted phenyl group, and n is a positive integer. Examples of the raw material component from which the repeating unit (III) is derived include 2,
Examples include 2,3,3,4,4-hexafluoropentanediol and 2,2,3,3,4,4,5,5-octafluorohexanediol. The molecular weight of this copolymer is in the range of 3000 to 5000. This copolymer is not particularly limited in its production method as long as it satisfies the above-mentioned molecular structure. For example, phenyltrichlorosilane or deuterated phenyl may be used in the aprotic solvent as in the case of the first embodiment. A method in which a trifunctional halosilane raw material such as trichlorosilane is dissolved, a fluoro-substituted alkanediol raw material is added and reacted, and then the unreacted halosilane raw material is hydrolyzed, or phenyltriethoxysilane in an alcohol solvent is used. It can be produced by a method of dissolving a trifunctional alkoxysilane raw material such as deuterated phenyltriethoxysilane and a fluoro-substituted alkanediol raw material and then adding an acid catalyst and heating. The refractive index control can also be performed by accurately adjusting the mixing ratio of the raw material components of the two types of units, as in the first invention.

First and second obtained by such a method
The optical material of the invention is a polymer material having a silsesquioxane structure, which is known as a heat resistant structure, as a main molecular skeleton. No thermal decomposition is observed even when heated to ~ 300 ° C, and excellent heat resistance is exhibited. Further, since a fluoroaralkyl type or fluoroalkyl type structural unit mainly having a C—F bond having no absorption in the near infrared region is introduced, the transparency in the main communication wavelength region in the near infrared region is improved. It is remarkable. Furthermore, since the introduced fluoroaralkyl-type or fluoroalkyl-type structural unit is flexible, there is an advantage that cracking does not occur in the waveguide manufacturing process.

Next, the optical waveguide of the third invention will be described. The optical waveguide of the present invention has a core part made of a polymer material, and a clad part surrounding the core part and made of a polymer material having a lower refractive index than the core part, and the core part and the clad part are The first aspect or the second aspect of the present invention
And is formed by heat curing the optical material. The manufacturing method is not particularly limited as long as it is an optical waveguide satisfying this requirement, but it can be manufactured, for example, by the following method.

First, at least two kinds of optical materials having a precisely controlled refractive index difference are prepared as materials for the core and the clad, respectively, according to the waveguide mode conditions required for the optical waveguide. The magnitude of the refractive index difference is determined according to the mode of guided light and the dimensions of the core, but is generally in the range of 0.1% to 5%. For example, when the mode diameters of the single-mode optical fiber and the guided light are matched, it is desirable that the cross section of the core has a square shape of 8 μm square and the refractive index difference is 0.3%. In the optical material of the first invention, the raw material component of the repeating unit represented by the general formula (I) has a higher refractive index than the raw material component of the repeating unit represented by the general formula (II), In the optical material of the second invention, the raw material component of the repeating unit represented by the general formula (I) has a higher refractive index than the raw material component of the repeating unit represented by the general formula (III). Therefore, the refractive index can be adjusted by changing the copolymerization ratio of the raw material components of the two types of repeating units.

Next, a clad material whose refractive index has been adjusted is applied onto the substrate by a spin coating method or the like, and this is thermally crosslinked to form a lower clad. Then, a core material having a controlled refractive index is applied onto this by spin coating or the like,
This is thermally crosslinked to form a core layer. Subsequently, a layer serving as an etching mask is formed on the core layer and processed into a desired waveguide pattern by photolithography or the like. As a material for the etching mask, organic photoresist, metal or the like is used. Further, the core layer is processed according to the above waveguide pattern by reactive ion etching to form a core portion. Finally, a clad material is applied to the upper part of the core part and then thermally crosslinked to form an upper clad layer. The optical waveguide manufactured in this manner can be peeled off from the substrate and used as necessary.

The third aspect of the present invention produced by such a method
The optical waveguide in the form of has excellent heat resistance and transparency due to the material used, and due to the structural unit having appropriate flexibility, stress due to heat cycle when using the optical waveguide element is There is an advantage in that the occurrence of cracking is mitigated and the occurrence of cracking is reduced, and thus the element destruction due to the occurrence of cracking is suppressed.

[0034]

EXAMPLES The present invention will now be described in more detail with reference to examples, but the present invention is not limited thereto.

Example 1 A phenylsiloxane unit (the general formula (I)): bis (hexafluoroisopropyl) phenyl unit (the general formula (II)) was prepared by the following procedure.
= 80: 20 (molar ratio), an optical material (optical material A) was produced.

200 cc of THF in a 1 liter reaction vessel
Phenylsiloxane unit [the above general formula (I)]
50 g of phenyltrichlorosilane was dissolved as a raw material component. To this, bis (hexafluoroisopropyl)
As a raw material component of the phenyl unit [the general formula (II)], 24 g of 1,4-bis (hexafluoro-2-hydroxyisopropyl) benzene dissolved in a small amount of THF and a small excess of triethylamine were added. After stirring this mixture for 1 hour, 11 cc of water was added little by little and the mixture was further stirred for 1 hour. The insoluble matter was removed, the solvent was removed, and 200 cc of toluene was added to the obtained oily matter, followed by washing with water,
The solvent was removed to obtain a colorless and transparent oily substance (optical material A).

Next, the phenylsiloxane unit (the above-mentioned general formula (I) was prepared by the same procedure as above except that the amounts of phenyltrichlorosilane and 1,4-bis (hexafluoro-2-hydroxyisopropyl) benzene were changed. ): Bis (hexafluoroisopropyl) phenyl unit (the above general formula (II)) = 74:26 (molar ratio), and an optical material was produced (optical material B).

An optical waveguide having the optical material A as a core and the optical material B as a clad obtained as described above was manufactured by the following procedure. The structure of the optical waveguide according to this embodiment is shown in FIG.

Each of the above two kinds of optical materials was dissolved in chlorobenzene and filtered using a filter having a pore size of 0.2 micron. First, a solution of the clad component (optical material B) was applied onto the silicon substrate 1 so that the film thickness after curing was 20 μm, and heat-cured at 300 ° C. for 1 hour to form the lower clad 2. Next, a solution of the core component (optical material A) is applied onto the lower clad 2 so that the film thickness after curing is 8 μm.
And was heat-cured at 300 ° C. for 1 hour to form a core layer. This core layer was finely processed by ordinary photolithography to have a length of 50 mm, a width of 8 μm, and a height of 8 μm to form a ridge-shaped core 3. Finally, a solution of the clad component (optical material B) is applied to the upper part of the core 3 so that the film thickness from the upper surface of the core after curing becomes 20 μm, and heat-cured at 300 ° C. for 1 hour to form an upper clad 4 Was formed. No cracking was observed in the process of producing the waveguide. When the waveguide loss in the near infrared region of the obtained optical waveguide was measured, it was less than 0.20 dB / cm at both wavelengths of 1.3 μm and 1.55 μm, and was 150 ° C. · 1.
000 hours, 75 ° C, 90% relative humidity, 100
It was confirmed that no crack was generated even after the 0-hour environment resistance test, and the increase in loss was within 5%.

Example 2 Optical materials C and D (constitution of each unit) were carried out in the same manner as in Example 1 except that deuterated phenyltrichlorosilane was used as a raw material component of the phenylsiloxane unit [the above-mentioned general formula (I)]. Manufactured optical materials A and B respectively). An optical waveguide was manufactured using these. No cracking was observed in the waveguide manufacturing process. The waveguide loss of the obtained optical waveguide was measured in the near infrared region.
It was less than 0.10 dB / cm at both wavelengths of 3 μm and 1.55 μm, and cracks were observed even after the environment resistance test at 150 ° C. for 1000 hours and 75 ° C. at 90% relative humidity for 1000 hours. It was confirmed that the increase in loss was within 5%.

Example 3 An optical material (optical material) of phenylsiloxane unit (the above-mentioned general formula (I)): hexafluoropentane unit (the above-mentioned general formula (III)) = 75:25 (molar ratio) by the following procedure E) was produced.

THF 200 cc in a 1 liter reaction vessel
Phenylsiloxane unit [the above general formula (I)]
50 g of phenyltrichlorosilane was dissolved as a raw material component. As a raw material component of the hexafluoropentane unit [the general formula (III)], 2,2,3,3,4,
17 g of 4-hexafluoropentanediol was added to a small amount of T
What was dissolved in HF and a small excess of triethylamine were added. After stirring this mixture for 1 hour, 10 cc of water was added.
Was added little by little and the mixture was further stirred for 1 hour. The steps of removing the insoluble matter and the solvent and washing with water were performed in the same manner as in Example 1 to obtain a colorless and transparent oily substance (optical material E).

Next, the same procedure as above was repeated except that the amounts of phenyltrichlorosilane and 2,2,3,3,4,4-hexafluoropentanediol used were changed.
Phenylsiloxane unit (the general formula (I)): hexafluoropentane unit (the general formula (III)) = 70:
An optical material of 30 (molar ratio) was produced (optical material F).

An optical waveguide having the optical material E obtained as above as a core and F as a clad was manufactured in the same procedure as in Example 1. No cracking was observed during the manufacturing process. The waveguide loss of the obtained optical waveguide in the near infrared region was measured and found to be 1.3 μm.
And 0.20 at any wavelength of 1.55 μm
It was less than dB / cm, and no cracks were observed even after the environment resistance test at 150 ° C. for 1000 hours and at 75 ° C., 90% relative humidity for 1000 hours, and it was confirmed that the increase in loss was within 5%. It was

(Example 4) The same procedure as in Example 3 was repeated except that deuterated phenyltrichlorosilane was used as a raw material component of the phenylsiloxane unit [the general formula (I)].
Optical materials G and H (each unit structure is the same as the above optical materials E and F, respectively) were manufactured. An optical waveguide was manufactured using these. No cracking was observed in the waveguide manufacturing process. When the waveguide loss in the near infrared region was measured for the obtained optical waveguide,
It is less than 0.10 dB / cm at both wavelengths of 1.3 μm and 1.55 μm, and is 150 ° C./1000.
It was confirmed that cracks were not generated even after the environment resistance test at 75 ° C., 90% relative humidity and 1000 hours, and the increase in loss was within 5%.

(Comparative example) 80:20 (molar ratio) of phenyltrichlorosilane and dimethyldichlorosilane and 7
Dissolved in THF at a ratio of 5:25, subjected to hydrolysis, solvent removal, and water washing in the same manner as in Example 1 above, to manufacture optical materials J and K for comparison, respectively. An optical waveguide having the thus obtained optical material J as a core and K as a clad was manufactured by the same procedure as in Example 1 and loss was evaluated. At 1.3 μm, it was 0.3 dB / cm. ,
A large loss value of 1.8 dB / cm was exhibited at 1.55 μm.

[0047]

As described above, the optical material of the present invention has remarkably improved transparency in the near-infrared region as compared with the conventional one, and has excellent heat resistance and moisture resistance. Furthermore, the occurrence of cracks, which has been an obstacle to the manufacture of optical waveguides, can be suppressed. Therefore, a high-performance optical waveguide can be manufactured with high efficiency, and the application to an optical waveguide type component is particularly advantageous.

[Brief description of drawings]

FIG. 1 is a component diagram showing an example of a polymer optical waveguide.

[Explanation of symbols]

1 substrate 2 Lower cladding 3 core part 4 Upper clad

Continuation of the front page (56) Reference JP-A-9-176323 (JP, A) JP-A-9-40680 (JP, A) JP-A-7-258604 (JP, A) JP-A-4-145108 (JP , A) JP-A-3-43423 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G02B 1/00-1/04 C08G 77/00-77/62 G02B 6/12 -6/14 G02B 6/00 386-391 REGISTRY (STN) CA (STN)

Claims (3)

(57) [Claims] 1. The following general formulas (I) and (II): [Chemical 2] An optical material containing a copolymer comprising a repeating unit represented by the formula: [wherein Z ₁ and Z ₂ represent the same or different phenyl groups or deuterium-substituted phenyl groups]. 2. The following general formulas (I) and (III): [Chemical 4] An optical material containing a copolymer comprising a repeating unit represented by the formula: wherein Z ₁ is a phenyl group or a deuterium-substituted phenyl group, and n is a positive integer. 3. An optical waveguide comprising: a core portion made of a polymer material; and a clad portion surrounding the core portion and made of a polymer material having a refractive index lower than that of the core portion. An optical waveguide, wherein the clad portion contains the thermosetting material of the optical material according to claim 1.