JPH09251113A - Heat-resistant polymer optical waveguide having large difference of refractive index and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polymer optical waveguide having excellent heat resistance and further large difference in the refractive index between the core and the clad compared to a conventional polymer optical waveguide by using a combination of polyimides which generate specified or more difference in the refractive index between the core and the clad for the core and the clad. SOLUTION: The core and the clad consists of a polymer material, and a combination of polyimides which generate >=3% difference in the refractive index between the core and the clad are used for the core and the clad. The material is preferably a polyimide having a repeating unit expressed by formula. In the production of the optical waveguide, the polyimide having the repeating unit expressed by formula is used for the core material. After a lower clad layer is formed, the core layer of the polyimide is formed by spin coating and hardening. Moreover, when an embedded type optical waveguide is to be produced, the core layer is processed by photolithography and dry etching, and then an upper clad layer is formed on the core.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical waveguide, which is particularly excellent in heat resistance and has a refractive index difference (Δ) between a core and a clad.
Is large (hereinafter referred to as “high Δ”).

[0002]

2. Description of the Related Art With the practical use of an optical communication system by developing a low loss optical fiber, development of various optical communication parts is desired. It is also desired to establish an optical wiring technology for mounting these optical components at a high density, particularly an optical waveguide technology. Generally, optical waveguides have low optical loss, are easy to manufacture,
Conditions such as being able to control the refractive index difference between the core and the clad in a wide range are required. High Δ especially for high-density optical wiring
In order to manufacture the optical waveguide, the wide controllability of the refractive index difference between the core and the clad is important. The difference in the refractive index between the core and the clad of an ordinary optical waveguide is approximately 0.3 to 1.0%, but so far in the case of silica optical waveguides
y) et al.
s), Vol. 26, No. 13, pp. 2621 to 2624 (1987), silicon oxide (SiO ₂ ) is used for the clad, and silicon nitride (Si ₃ N ₄ ) is used for the core. High Δ optical waveguides with an index difference of 37.7% have been reported. However, the existing silica-based high Δ optical waveguide including this optical waveguide needs to be manufactured on a substrate such as Si and used on the substrate because the optical waveguide itself is poor in flexibility. In addition, for the production of the silica-based optical waveguide, 1
Since a high temperature treatment of 000 ° C. or higher is required, the cost becomes high, and there is a restriction on component production such that an optical waveguide cannot be produced afterward when a material weak to heat is used. On the other hand, an organic polymer material can be formed into a thin film by desolvation or imidization (in the case of polyimide) after casting the solution on a substrate or the like. Therefore, an optical waveguide at a relatively low temperature of 400 ° C or lower is used. Can be manufactured, and the problem of restrictions in manufacturing parts can be solved. Since the polymer optical waveguide has flexibility, not only a rigid substrate such as a quartz or silicon substrate but also a film type optical waveguide (tape optical waveguide) is produced. If this feature is utilized, a flexible printed circuit board (FPC) having flexibility is used in the field of electronic components to achieve miniaturization and high density. By using the optical wiring to realize high-density optical wiring in a limited space. Booth uses the acrylic resin in Journal of Lightwave Technology, Volume 7, No. 10, pp. 1445-1453 (1989), and the refractive index difference between the core and the clad. Reported a polymer optical waveguide having a maximum of 5%. However, this optical waveguide has a drawback that it has a low heat resistance temperature because it uses an acrylic resin. In addition to the above, the present inventors have realized a film optical waveguide using polyimide in Japanese Patent Application No. 6-54376 as a polymer optical waveguide having excellent flexibility and heat resistance. There is. However, this film optical waveguide has a small refractive index difference of about 0.4% between the core and the clad.

As described above, at present, a polymer optical waveguide having both heat resistance and high Δ has not been realized. In order to achieve higher density by using a film optical waveguide, which is advantageous for performing high-density optical wiring, in order to achieve higher bending strength, that is, the optical transmission loss is small with respect to bending with a small curvature, and the optical waveguide characteristic is small. A film optical waveguide having stable properties is required. For that purpose, it is necessary to increase the difference in refractive index between the core and the clad of the optical waveguide to strengthen the light confinement effect. Specifically, in order to wire an optical waveguide having a bend with a curvature of 1 mm or less with low loss, it is necessary to make the refractive index difference between the core and the clad 3% or more. Further, also in this case, it is necessary to have solder heat resistance for mixed mounting with electric wiring.

[0004]

In the polymer optical waveguide useful for high-density optical wiring as shown in the prior art, an optical waveguide having excellent heat resistance and a larger refractive index difference between the core and the clad. Is needed. An object of the present invention is to provide a polymer optical waveguide having a larger difference in refractive index between the core and the clad than existing polymer optical waveguides and having excellent heat resistance.

[0005]

The first aspect of the present invention is to provide a polymer optical waveguide in which a core and a clad are made of a polymer material. A feature is that a combination of polyimides having a difference in refractive index of 3% or more is used. A second aspect of the present invention is a polymer optical waveguide in which a core and a clad are made of a polymer material, which uses a combination of polyimide having a refractive index difference of 3% or more between the core and the clad. The invention relates to a Δ polymer optical waveguide, and as a core material thereof, the following structural formula (Formula 1):

[0006]

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It is characterized by using a polyimide having a repeating unit represented by: A third aspect of the present invention is a polymer optical waveguide in which a core and a clad are made of a polymer material, which uses a combination of polyimide having a refractive index difference of 3% or more between the core and the clad. The invention relates to a high Δ polymer optical waveguide having properties, and the following general formula (Formula 2) is used as a core material thereof:

[0008]

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[Wherein R ₁ is the following structural formula (Formula 3):

[0010]

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Represents a tetravalent organic group selected from the group consisting of groups represented by the following formula, wherein R ₂ is the following structural formula (Formula 4):

[0012]

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A divalent organic group selected from the group consisting of the groups represented by:] is used, and a polyimide having a repeating unit represented by the formula:

[0014]

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[Wherein R ₁ has the same meaning as in the general formula (Formula 3), and R ₃ is the following structural formula (Formula 6):

[0016]

[Chemical 6]

A divalent organic group selected from the group consisting of the groups represented by:] is used, and a polyimide having a repeating unit represented by the following is used. The fourth aspect of the present invention
The present invention relates to a method for manufacturing a high Δ polymer optical waveguide according to the first invention. That is, a polyimide having a repeating unit represented by the structural formula (Formula 1) described in the second invention is used as the core material, and after forming the lower clad layer, a core layer made of this polyimide is formed on the lower clad layer. The core layer is formed by spin coating and curing, and in the case of an embedded optical waveguide, the core layer is processed by photolithography and dry etching, and then the upper clad layer is formed on the core. A fifth invention of the present invention is an invention relating to a method for manufacturing a high Δ polymer optical waveguide having heat resistance according to the first invention. That is, a polyimide having a repeating unit represented by the general formula (Formula 2) described in the third invention is used as the core material, and a structural formula (formula) also described in the third invention is used as the cladding material. Using a polyimide having a repeating unit represented by 5), a lower clad layer made of this polyimide is formed by spin coating and curing, and then a core layer made of this polyimide is formed on the lower clad layer by spin coating and curing, Further, in the case of a buried type optical waveguide, this core layer is processed by photolithography and dry etching, and then an upper clad layer is formed on the core by spin coating and curing.

As a result of various investigations by the present inventors on polymer optical waveguides having excellent heat resistance and bending characteristics, a combination of polyimide having a refractive index difference of 3% or more between the core and the clad is used for the core and the clad. By doing so, they have found that a polymer optical waveguide that realizes the purpose can be produced. That is, according to the present invention, a heat-resistant polymer optical waveguide having a minimum bending radius of 1 mm or less and extremely excellent bending characteristics was realized.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below. The clad polyimide and the core polyimide of the optical waveguide, which are the constituent elements of the present invention, may be polyimide having any molecular structure as long as it is a combination of two kinds of polyimides having a difference in refractive index of 3% or more. A polyimide having a repeating unit represented by the formula (Formula 2) is used as a core material and a polyimide having the repeating unit represented by the formula (Formula 5) is used as a clad material. To be able to achieve a rate difference,
It is preferable from the viewpoints of excellent light transmittance and heat resistance, and easy production of an optical waveguide. Furthermore, it is also possible to use a mixture or copolymer of two or more types of polyimide as each polyimide used for the core and the clad. The polyimide having the repeating unit represented by the general formula (Formula 2) is 4,4′-oxydiphthalic acid dianhydride and 1,4-bis (3,4-dicarboxytrifluorophenoxy) tetrafluorobenzene dianhydride. , 2, 2
-Bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride, or a derivative thereof and 4,4'-
Oxydianiline, 4,4'-methylenedianiline,
It can be produced from 4,4'-diaminodiphenyl sulfone or 3,3'-diaminophenyl sulfone.

On the other hand, the polyimide having the repeating unit represented by the structural formula (Formula 5) is 4,4'-oxydiphthalic acid dianhydride, 1,4-bis (3,4-dicarboxytrifluorophenoxy) tetrafluoro. Benzene dianhydride,
2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride, or a derivative thereof and 2,
2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl, 2,2'-bis (4-aminophenyl)
It can be produced from hexafluoropropane, bis (2,3,5,6-tetrafluoro-4-aminophenyl) ether, pentafluorophenoxy-2,4-diaminobenzene. Among them, the method for producing 1,4-bis (3,4-dicarboxytrifluorophenoxy) tetrafluorobenzene dianhydride is described in JP-A No. 5-1148. 2,2'-bis (trifluoromethyl) -4,
The method for producing 4'-diaminobiphenyl is described in, for example, Journal of the Chemical Society of Japan, No. 3, pp. 675-676 (1972). The method for producing bis (2,3,5,6-tetrafluoro-4-aminophenyl) ether is
For example, published by Springer-Verlag, Berlin City, 1985, I.S. L. Knunyanz and G. G. FIG. Jacobson (IL Knunyants, GG Ya
kobson) Co-editing, Synthesis of Fluoroorganic Compo
unds). A method for producing pentafluorophenoxy-2,4-diaminobenzene is described in JP-A-1-180860. Polyamic acid is produced by reacting these diamines with tetracarboxylic dianhydride. The acid dianhydride used in the synthesis of the polyamic acid can also be used as the ring-opened tetracarboxylic acid or an acid chloride or ester compound as a derivative thereof.

The reaction conditions may be the same as the usual polyamic acid polymerization conditions, and generally, the reaction is carried out in a polar organic solvent such as N-methyl-2-pyrrolidone, N, N-dimethylacetamide or dimethylformamide. Next, the polyimide synthesis is carried out by imidization of the obtained polyamic acid. This can also be carried out by a usual polyimide synthesis method such as imidization by heating or chemical imidization using acetic anhydride or the like. When synthesizing a polyimide mixture, two or more types of polyamic acid after the completion of the polymerization reaction are prepared, and these are mixed and stirred until they become uniform in a solution state, and then imidized. When the polyimide used is soluble, the synthesized polyimide may be dissolved in a solvent and mixed, and then the solvent may be removed. 2 when synthesizing a polyimide copolymer
A polyamic acid copolymer is synthesized using two or more kinds of diamines, or two or more kinds of acid anhydrides or derivatives thereof,
This is imidized.

The structure of the high Δ polyimide optical waveguide of the present invention includes, for example, a slab type and a buried type. A method of manufacturing the embedded optical waveguide will be described with reference to FIG. That is, FIG. 1 is a process chart showing an example of a method for manufacturing an embedded optical waveguide according to the present invention, wherein reference numeral 1 is a substrate,
2 is a lower clad layer, 3 is a core layer, 4 is a mask for forming a core pattern, 5 is a photoresist layer, and 6 is an upper clad layer. A polyimide solution or a polyamic acid solution is applied onto a substrate 1 made of silicon or the like by a method such as spin coating, and is cured by heating or the like to obtain a lower clad layer 2. Next, a solution of a polyimide having a higher refractive index than the polyimide used as the lower clad layer or a polyamic acid solution is formed thereon by the same method as that for forming the lower clad layer 2 to obtain the core layer 3. Next, a mask layer 4 for forming a core pattern is formed thereon (FIG. 1A). As the mask, metals such as Al and Ti, silicon oxide (SiO ₂ ), spin-on-glass (SOG), silicon-containing photoresist, photosensitive polyimide and the like can be used. After applying the mask layer 4, a photoresist is applied, prebaked, exposed, developed and afterbaked to obtain a patterned photoresist layer 5 (FIG. 1B). Next, after removing the mask layer not protected by the photoresist layer by etching [FIG. 1 (c)], the polyimide not protected by the aluminum layer is removed by dry etching [FIG. 1 (d)]. When a Si-containing photoresist or photosensitive polyimide is used for the mask layer 4, a patterned mask layer can be obtained by directly exposing and developing the mask layer, so that it is not necessary to use a photoresist. Next, the remaining mask layer 4 is removed by dry etching or using a peeling solution [FIG. 1 (e)]. Next, a polyimide solution having a refractive index smaller than that of the core layer or a polyamic acid solution is formed thereon by the same method as that for forming the lower clad layer 2 to obtain an upper clad layer 6 [FIG.
(F)]. In this way, a buried type polyimide optical waveguide is obtained. Further, in order to manufacture the embedded film optical waveguide, the previously manufactured optical waveguide is peeled off from the substrate. When Si whose surface is thermally oxidized is used as the substrate, it can be peeled by immersing it in hydrofluoric acid. When an Al plate is used as the temporary substrate, it can be peeled off by immersing it in dilute hydrochloric acid. In this way, an embedded polyimide film optical waveguide is obtained. Further, by heat-treating this polyimide optical waveguide at a predetermined temperature, an optically uniform embedded polyimide film optical waveguide can be obtained [FIG. 1 (g)].

Further, as shown in FIG. 2, the lower clad layer 2, the core layer 3 and the upper clad layer 6 are sequentially formed on the substrate by using the same method as the embedded polyimide optical waveguide of FIG. In this way, a slab type polyimide optical waveguide is obtained [FIG. 2 (a)]. Further, in order to manufacture the slab type polyimide film optical waveguide, the previously manufactured optical waveguide is peeled from the substrate. Further, by heat-treating this film optical waveguide at a predetermined temperature, an optically uniform slab type polyimide film optical waveguide can be obtained [Fig.
(B)]. In the production of the polyimide optical waveguide on the substrate, for the purpose of improving the adhesion between the substrate and the lower clad,
For example, when a silicon substrate is used, it goes without saying that an adhesion improver layer containing a silane coupling agent as a main component can be added.

[0024]

EXAMPLES Next, the present invention will be described more specifically with reference to some examples. It should be noted that the combination of various polymers, and the high Δ of the present invention due to the optical waveguide structure are limitless.
It is clear that a polyimide optical waveguide can be obtained, and the present invention is not limited to these examples.

The thermal decomposition temperature of the polyimide used in this example is shown in Table 1. The thermal decomposition temperature is shown as the temperature at the time of 10 wt% weight loss when the temperature was raised at a rate of 10 ° C./min in a nitrogen stream.

[0026]

[Table 1]

The symbols used in Table 1 and the table below have the following meanings. 6FDA: 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride 10FEDA: 1,4-bis (3,4-dicarboxytrifluorophenoxy) tetrafluorobenzene dianhydride ODPA: 4, 4'-oxydiphthalic anhydride PMDA: pyromellitic dianhydride TFDB: 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl 4FMPD: tetrafluoro-m-phenylenediamine 8FODA: bis (2 , 3,5,6-Tetrafluoro-4-aminophenyl) ether 4,4'-ODA: 4,4'-oxydianiline 3,4'-ODA: 3,4'-oxydianiline 2,4 ' -ODA: 2,4'-oxydianiline 3FDAM: 1,1-bis (4-aminophenyl) -1-phen Le -2,2-2- trifluoroethane 3F-EDAM: [1,1-bis {4- (4-aminophenoxy) phenyl} -1-phenyl-2,2,2
- trifluoroethane] 3,3'-DDSO _2: 3,3'- Shi-diaminodiphenyl sulfone 4,4'-DDSO _2: 4,4'- shea diaminodiphenylsulfone 4,4'-MDA: 4,4 ' -Methylenedianiline 4-BDAF: 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane APHF: 2,2-bis (3-amino-4-)
Hydroxyphenyl) hexafluoropropane 4,4′-6F: 2,2-bis (4-aminophenyl) hexafluoropropane m-A5F: pentafluorophenoxy-2,
4-diaminobenzene

It can be seen from Table 1 that all of the polyimides used in the present invention have a thermal decomposition temperature of 450 ° C. or higher and thus are optical waveguide materials having excellent heat resistance.

The refractive index difference (Δ) between the core and the clad used in this example is the refractive index [n (core)] of the polyimide film used for the core and the refractive index [n of the polyimide film used for the clad at a wavelength of 1.55 μm. n (clad)] was measured by the prism coupling method, and the value was calculated from the following mathematical formula (Equation 1).

[0030]

## EQU1 ## Δ% = [{n (core) -n (clad)} / n
(Core)] x 100

Further, the minimum bending radius of the produced film optical waveguide is such that the optical waveguide in a linear state is gradually curved, and the optical loss of the guided light is obtained from the intensity ratio of the incident light and the outgoing light each time, and the optical loss increases. It is shown as the radius of curvature of the optical waveguide when it starts. The cross-sectional structure of the optical waveguide was evaluated by a transmission optical microscope using a sample obtained by cutting the produced optical waveguide to a length of 2 mm with a dicing saw.

Example 1 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA) and 2,2-bis (3-amino-4-hydroxyphenyl) were prepared on a 4-inch silicon wafer. ) N, N-dimethylacetamide (DMAc) 15 wt of polyamic acid, which is a precursor of polyimide synthesized using hexafluoropropane (APHF)
% Solution was applied by spin coating so that the film thickness after heating was 20 μm. This is 160 degreeC for 2 hours at 70 degreeC
The lower cladding layer was formed by heat treatment at 1 ° C. for 1 hour, 250 ° C. for 30 minutes, and 350 ° C. for 1 hour. Next, 4,4'-oxydiphthalic anhydride (ODP) was formed on the lower clad layer.
A) and 4,4'-oxydianiline (4,4'-OD
The film thickness after heating a 15 wt% DMAc solution of polyamic acid, which is a polyimide precursor synthesized using A), was 3 μm.
It was applied by a spin coating method so as to have a thickness of m. 2 hours at 70 ℃, 160 hours for 1 hour, 250 ℃ for 30 hours
A heat treatment was performed at 380 ° C. for 1 minute to form a core layer.
Next, an aluminum layer having a thickness of 0.2 μm was vapor-deposited on the core layer. Next, a positive photoresist was applied on this aluminum layer by a spin coating method, and then prebaked at about 95 ° C. Next, a photomask for pattern formation and an ultra-high pressure mercury lamp were used to irradiate with ultraviolet rays, and then development was performed using a developer for a positive resist. 135 ° C thereafter
I did a post bake. As a result, a linear resist pattern having a line width of 3 μm was obtained. Next, wet etching of aluminum was performed to transfer the resist pattern to the aluminum layer. Further, using the patterned aluminum as a mask, the polyimide of the core layer was processed by dry etching. Next, the aluminum on the upper layer of the polyimide was removed with an etching solution. Then, 15 wt% of the same polyamic acid as the polyimide used as the lower clad, which is a precursor of the polyamic acid, DMAc
% Solution was applied by spin coating so that the film thickness after heating was 20 μm. This is 160 degreeC for 2 hours at 70 degreeC
Heat treatment was performed at 1 ° C. for 1 hour, 250 ° C. for 30 minutes, and 380 ° C. for 1 hour to form an upper cladding layer. Then this is 10%
The silicon substrate was peeled off by immersing in a hydrochloric acid aqueous solution. Finally, this was heat-treated at 350 ° C. for 1 hour to obtain an embedded polyimide film optical waveguide. The refractive index difference between the core and the clad at a wavelength of 1.55 μm of this optical waveguide was 8.4% as a result of the refractive index of the polyimide film used for the core and the refractive index of the clad. The minimum bending radius when this polyimide film optical waveguide was gradually bent from a straight state was 0.3 mm. Further, this optical waveguide was heat-treated at 350 ° C. for 1 hour using an oven in a nitrogen atmosphere. As a result of evaluating the cross-sectional structure of this optical waveguide with a microscope, the shape of the core and the film of the clad layer did not change as compared with those before the heat treatment. Further, the optical loss of the optical waveguide after the heat treatment did not change as compared with that before the heat treatment.

Examples 2 to 22 Polyamides prepared from the acid dianhydride and the diamine as the raw materials shown in Table 2 were prepared from DMAc solutions of polyamic acid, which is the precursor of the polyimide used as the lower clad layer and the upper clad layer in Example 1, as shown in Table 2. An embedded polyimide optical waveguide was prepared in the same manner as in Example 1, except that the acid was changed to a DMAc solution. Table 2 shows the refractive index difference between the core and the clad of this polyimide film optical waveguide, and the minimum bending radius. Further, this optical waveguide is 350 ° C. by using an oven in a nitrogen atmosphere.
Heat treatment was performed at 1 ° C. for 1 hour. As a result of evaluating the cross-sectional structure of this optical waveguide with a microscope, in all the optical waveguides of Example 2 to Example 22, the core shape and the film of the cladding layer did not change as compared with those before the heat treatment. Further, the optical loss of the optical waveguides after the heat treatment did not change in all the optical waveguides of Example 2 to Example 22 as compared with that before the heat treatment.

[0034]

[Table 2]

Examples 23 to 46 Polyamide acid DMAc solutions, which are polyimide precursors used as the lower clad layer and the upper clad layer in Example 1, and polyimide precursors used as the core layer in Example 1. A DMAc solution of polyamic acid was changed to a DMAc solution of polyamic acid synthesized from acid dianhydride and diamine as raw materials shown in Table 3, and an embedded polyimide optical waveguide was manufactured by the same method as in Example 1. Table 3 shows the refractive index difference between the core and the clad of this polyimide film optical waveguide, and the minimum bending radius. Further, this optical waveguide was heat-treated at 350 ° C. for 1 hour using an oven in a nitrogen atmosphere. As a result of evaluating the cross-sectional structure of this optical waveguide with a microscope, in all the optical waveguides of Example 2 to Example 20, the core shape and the film of the clad layer did not change as compared with those before the heat treatment. Further, the optical loss of the optical waveguides after the heat treatment did not change in all the optical waveguides of Example 23 to Example 46 as compared with that before the heat treatment.

[0036]

[Table 3]

Example 47 In Example 18, after forming the core layer having a film thickness of 3 μm, the upper clad layer was formed without forming the aluminum layer, and then the lower clad layer, the core layer, and the lower clad layer were formed in the same manner as in Example 1. A three-layer slab-type polyimide film optical waveguide including an upper clad layer was produced. The difference in refractive index between the core and the clad and the minimum bending radius of this polyimide film optical waveguide were the same as those of the embedded optical waveguide of Example 1 produced using the same material. Further, this optical waveguide was heat-treated at 350 ° C. for 1 hour using an oven in a nitrogen atmosphere. As a result of evaluating the sectional structure of this optical waveguide with a microscope, the shape of the core and the film of the clad layer did not change as compared with those before the heat treatment. Further, the optical loss of the optical waveguide after the heat treatment did not change as compared with that before the heat treatment.

Comparative Examples 1 and 2 DMAc solution of polyamic acid, which is a precursor of polyimide used as the lower clad layer and the upper clad layer of Example 1, and the polyimide precursor used as a core layer of Example 1. The DMAc solution of polyamic acid was changed to a DMAc solution of polyamic acid synthesized from the raw material acid dianhydride and diamine shown in Table 3, and the thickness of the core layer after heating was 8 μm.
Then, a buried type polyimide optical waveguide was manufactured by the same method as in Example 1 except for the above. Further, this optical waveguide was heat-treated at 350 ° C. for 1 hour using an oven in a nitrogen atmosphere.
As a result of evaluating the sectional structure of this optical waveguide with a microscope, the shape of the core and the film of the clad layer did not change as compared with those before the heat treatment. Further, the optical loss of the optical waveguide after the heat treatment did not change as compared with that before the heat treatment. However, the refractive index difference between the core and the clad of this polyimide film optical waveguide is less than 3%, and the minimum bending radius of this polyimide film optical waveguide exceeds 1 mm. Has increased significantly.

[0039]

According to the present invention, a high refractive index difference polymer optical waveguide having a refractive index difference between the core and the clad of 3% or more, a minimum bending radius of 1 mm or less, and excellent heat resistance is provided.
There is an effect that it can be realized at a low production temperature of 00 ° C. or less. By using this optical waveguide, high-density optical wiring having excellent heat resistance can be realized.

[Brief description of drawings]

1A to 1C are cross-sectional views sequentially showing a method of manufacturing an embedded high-refractive index difference polyimide optical waveguide and an embedded high-refractive index difference polyimide film optical waveguide on a substrate according to the present invention.

2A to 2D are cross-sectional views sequentially showing a method for producing a slab type high refractive index difference polyimide optical waveguide and a slab type high refractive index difference polyimide film optical waveguide according to the present invention.

[Explanation of symbols]

1: substrate, 2: lower clad layer, 3: core layer, 4: aluminum layer, 5: photoresist layer, 6: upper clad layer

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Tomomi Sakata 3-19-3 Nishishinjuku, Shinjuku-ku, Tokyo Inside Nippon Telegraph and Telephone Corporation (72) Inventor Shigekuni Sasaki 3-19-3 Nishishinjuku, Shinjuku-ku, Tokyo No. 2 within Nippon Telegraph and Telephone Corporation

Claims (5)

[Claims] 1. A polymer optical waveguide whose core and clad are made of a polymer material, characterized in that a combination of polyimide having a refractive index difference between the core and the clad of 3% or more is used for the core and the clad. High refractive index polymer optical waveguide. 2. The structure according to claim 1, which has the following structural formula (Chemical Formula 1): A high refractive index difference polymer optical waveguide characterized by using a polyimide having a repeating unit represented by: 3. The core material according to claim 1, having the following general formula (Formula 2): [Wherein R ₁ is the following structural formula (Formula 3): Represents a tetravalent organic group selected from the group consisting of the following groups, wherein R ₂ is the following structural formula (Formula 4): Represents a divalent organic group selected from the group consisting of groups represented by the following formula], and uses a polyimide having a repeating unit represented by [In the formula, R ₁ has the same meaning as in the general formula (Formula 3), and R ₃ is the following structural formula (Formula 6): A divalent organic group selected from the group consisting of groups represented by the following formula] is used. A high refractive index difference polymer optical waveguide having heat resistance, comprising a polyimide having a repeating unit represented by 4. The method for producing a polymer optical waveguide according to claim 1, wherein a polyimide having a repeating unit represented by the structural formula (Formula 1) according to claim 2 is used as a core material, After forming the clad layer, a core layer made of this polyimide is formed on the lower clad layer by spin coating and curing, and in the case of an embedded optical waveguide, this core layer is processed by photolithography and dry etching, and then on the core. A method of manufacturing a high refractive index difference polymer optical waveguide, which comprises forming an upper clad layer on the substrate. 5. The method for producing a polymer optical waveguide according to claim 1, wherein a polyimide having a repeating unit represented by the general formula (Formula 2) according to claim 3 is used as a core material thereof, A polyimide having a repeating unit represented by the structural formula (Formula 5) according to claim 3 is used as a clad material, and a lower clad layer made of this polyimide is formed by spin coating and curing, and then the polyimide is formed on the lower clad layer. The core layer consisting of is formed by spin coating and curing, and in the case of an embedded optical waveguide, this core layer is processed by photolithography and dry etching, and then the upper clad layer is formed on the core by spin coating and curing. And a method for producing a high-refractive-index-difference polymer optical waveguide having heat resistance.