JP2013120338A - Method for producing optical waveguide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing optical waveguides capable of stably acquiring a high-quality optical waveguide without any defects such as cracks formed on a core.SOLUTION: The method for producing optical waveguides includes the steps of: forming an underclad layer 22 on a flexible substrate 30; applying a resin composition including fluorine-containing polyarylene prepolymer including crosslinkable functional group and propylene glycol monomethyl ether acetate to the underclad layer 22, prebaking the underclad layer, and acquiring a laminate 33 in which a core precursor layer 12 is formed on the underclad layer 22; forming a core 10 by exposing the core precursor layer 12 to light, developing it and forming a pattern thereon; and forming an overclad layer 24 on the underclad layer 22 and the core 10. A ratio X of the mass of a solvent included in the core precursor layer 12 after the prebake to the mass of a dry solid matter included in the core precursor layer 12 is defined as 0.14-0.48.

Description

  The present invention relates to an optical waveguide manufacturing method.

  In the field of communication equipment, with the miniaturization of equipment and the speeding up of communication, the use of resin-made optical waveguides for signal transmission has attracted attention. The resin used for the core and clad of the optical waveguide is required to have high transparency and heat resistance. As a resin having high transparency and heat resistance, a fluorine-containing polyarylene prepolymer is known (Patent Document 1), and a curable composition using the fluorine-containing polyarylene prepolymer has also been proposed (Patent Document). 2).

As a method for manufacturing an optical waveguide, for example, a method having the following steps (i) to (iii) is known (Patent Document 3).
(I) A curable composition containing a clad-forming resin is applied on a flexible substrate such as a resin film, and baked to form an underclad layer.
(Ii) A curable composition containing a core-forming resin is applied onto the undercladding layer, pre-baked to form a core precursor layer, patterned by exposure and development, and then finished post-baking To form a core.
(Iii) A curable composition containing a resin for forming a clad is again applied on the under clad layer and the core, and baked to form an over clad layer.
By the steps (i) to (iii), an optical waveguide having a core surrounded by a clad composed of an under clad layer and an over clad layer is obtained.

International Publication No. 2006/137327 International Publication No. 2007/119384

TECHNO-COSMOS 2008 Mar. Vol.21 15-21

  However, when the fluorine-containing polyarylene prepolymer is used as the core forming resin in the manufacturing method, cracks may occur in the core of the manufactured optical waveguide. In particular, when the roll-to-roll method is adopted and there is a step of winding the laminate formed with the core precursor layer in step (ii) once on a roll, a crack is generated in the core of the manufactured optical waveguide. There is a high tendency.

  An object of this invention is to provide the manufacturing method of the optical waveguide from which the high quality optical waveguide without a defect, such as a crack, in a core is obtained stably.

The method for producing an optical waveguide of the present invention includes a step (IA) of forming an underclad layer on a flexible substrate, a core-forming resin comprising a fluorine-containing polyarylene prepolymer having a crosslinkable functional group, and The process of obtaining the laminated body which apply | coated the resin composition for core formation containing the solvent which consists of propylene glycol monomethyl ether acetate on the said under clad layer, performs prebaking, and formed the core precursor layer on the said under clad layer (II-A), a step of exposing and developing the core precursor layer and patterning to form a core (III-A), and a step of forming an overcladding layer on the undercladding layer and the core (IV -A)
In this method, the mass ratio X of the solvent contained in the core precursor layer after pre-baking with respect to the dry solid content of the core precursor layer is 0.14 to 0.48.
The ratio X is preferably 0.14 to 0.37.
Moreover, it is preferable to have the step which winds up the laminated body which formed the core precursor layer on the said under clad layer once before a exposure.

The method for producing an optical waveguide according to the present invention includes a step (IB) of forming an undercladding layer on a flexible first substrate, and a core comprising a fluorine-containing polyarylene prepolymer having a crosslinkable functional group. A core-forming resin composition comprising a forming resin and a solvent comprising propylene glycol monomethyl ether acetate is applied onto a flexible second substrate, pre-baked, and a core precursor is formed on the second substrate. A step (II-B) of obtaining a laminate in which a body layer is formed, and the core precursor layer of the laminate in which a core precursor layer is formed on the second substrate, on the first substrate. After laminating on the formed under clad layer by a thermal laminating method, the core precursor layer is exposed, developed and patterned to form a core (III-B), the under clad layer and the core A step of forming the over cladding layer on the (IV-B), and
In this method, the mass ratio X of the solvent contained in the core precursor layer after pre-baking with respect to the dry solid content of the core precursor layer is 0.14 to 0.48.
The ratio X is preferably 0.14 to 0.37.
Moreover, it is preferable to have the step which winds up the laminated body which formed the said core precursor layer on the said 2nd base material around a roll once.

  According to the optical waveguide manufacturing method of the present invention, a high-quality optical waveguide free from defects such as cracks in the core can be stably obtained.

It is sectional drawing which shows an example of an optical waveguide. It is a figure which shows an example of the manufacturing method of the optical waveguide of this invention. It is a figure which shows an example of the manufacturing method of the optical waveguide of this invention. It is a figure which shows an example of the manufacturing method of the optical waveguide of this invention. It is a figure which shows an example of the manufacturing method of the optical waveguide of this invention. It is a figure which shows an example of the manufacturing method of the optical waveguide of this invention. It is a figure which shows an example of the manufacturing method of the optical waveguide of this invention.

<Optical waveguide>
FIG. 1 is a view showing an example of an optical waveguide manufactured by the optical waveguide manufacturing method of the present invention, and is a cross-sectional view perpendicular to the length direction of the core. The optical waveguide 1 is in the form of a long film having a plurality of cores 10 provided in parallel with each other and spaced apart from each other, and a clad 20 surrounding the core 10.

(core)
The refractive index of the core 10 is higher than the refractive index of the clad 20.
The cross-sectional shape of the core 10 is rectangular in the illustrated example, but is not limited thereto. For example, it may be a trapezoid, a circle, an ellipse, or a pentagon or more polygon. When the cross-sectional shape of the core 10 is a polygon, the corners may be rounded.
What is necessary is just to design the cross-sectional shape and magnitude | size of the core 10 suitably considering the coupling efficiency with a light source or a light receiving element. The coupling efficiency depends on the core diameter and the numerical aperture (NA).

  The width a and height b of the core 10 are each preferably 1 to 100 μm. When the width a and the height b of the core 10 are 1 μm or more, a decrease in the coupling efficiency with the light source or the light receiving element can be suppressed. When the width a and the height b of the core 10 are 100 μm or less, even when the bending radius (R) is about 1 mm, bending loss can be reduced. In addition, since the size (width and height) of the light receiving portion of the photodiode (PD) used as the light receiving element is usually 100 μm or less, the width a and height b of the core 10 is 100 μm or less from this point. Preferably there is.

The core-forming resin that forms the core is a fluorine-containing polyarylene prepolymer having a crosslinkable functional group (hereinafter referred to as “prepolymer (A)”).
The prepolymer (A) has a polyarylene structure in which a plurality of aromatic rings are bonded via a single bond or a linking group, a fluorine atom, and a crosslinkable functional group.
Examples of the linking group in the polyarylene structure include an ether bond (—O—), a sulfide bond (—S—), a carbonyl group (—CO—), and a divalent group obtained by removing a hydroxyl group from a sulfonic acid group (—SO ₂ —). Etc.

Of the prepolymer (A), one having a structure in which a plurality of aromatic rings are bonded via a linking group containing an ether bond (—O—) is referred to as a fluorinated polyarylene ether prepolymer (A1).
Examples of the linking group containing an ether bond include an ether bond (—O—) consisting only of an etheric oxygen atom, and an alkylene group containing an etheric oxygen atom in the carbon chain.
Since the fluorinated polyarylene ether prepolymer (A1) has an etheric oxygen atom, the molecular structure has flexibility and the cured product has good flexibility.

Since the prepolymer (A) has an aromatic ring, the heat resistance is good.
The crosslinkable functional group of the prepolymer (A) does not substantially react during the production of the prepolymer, reacts by applying external energy, and causes a high molecular weight by crosslinking or chain extension between prepolymer molecules. It is a group. Examples of external energy include heat, light, and electron beam. A plurality of external energies may be used in combination.

  Crosslinkable functional groups include vinyl, allyl, allyloxy, methacryloyl (oxy), acryloyl (oxy), vinyloxy, trifluorovinyl, trifluorovinyloxy, ethynyl, 1-oxocyclopenta Examples include -2,5-dien-3-yl group, cyano group, alkoxysilyl group, diarylhydroxymethyl group, hydroxyfluorenyl group, cyclobutalene ring, and oxirane ring. A vinyl group, a methacryloyl (oxy) group, an acryloyl (oxy) group, a trifluorovinyloxy group, an ethynyl group, a cyclobutalene ring, and an oxirane ring are preferable because of high reactivity and high crosslink density. A vinyl group and an ethynyl group are particularly preferable from the viewpoint of good heat resistance.

  When heat is used as external energy, the prepolymer (A) preferably has a reactive functional group that reacts at a reaction temperature of 40 to 500 ° C. as a crosslinkable functional group. If the reaction temperature is too low, the stability of the prepolymer (A) or the curable composition containing the prepolymer (A) during storage cannot be ensured. If the reaction temperature is too high, thermal decomposition of the prepolymer itself will occur during the reaction. The reaction temperature is more preferably from 60 to 300 ° C, further preferably from 70 to 200 ° C, particularly preferably from 120 to 250 ° C.

  When light (actinic radiation) is used as external energy, it is preferable to perform exposure in a state where the prepolymer (A) and the photosensitive agent coexist. Specifically, the core 10 formed of a core-forming resin composition (curable composition) containing a prepolymer (A) and a photosensitizer is preferable. In the step (II) described later, if light (actinic radiation) is selectively irradiated only on a desired portion, the prepolymer (A) becomes high molecular weight only in the exposed portion, and the unexposed portion is dissolved in the developer. As a result, the core 10 having a desired pattern is obtained.

The prepolymer (A) has a fluorine atom. That is, since the prepolymer (A) has a C—F bond in which a hydrogen atom of a C—H bond is substituted with a fluorine atom, the presence ratio of the C—H bond is reduced. Since the C—H bond has absorption in the optical communication wavelength band (1250 to 1650 nm), the prepolymer (A) having few C—H bonds can suppress light absorption in the optical communication wavelength band. Moreover, since it has a fluorine atom, the water absorption rate and moisture absorption rate are low, the resistance to high temperature and high humidity is excellent, and the chemical stability is also high. Therefore, in the optical waveguide using the prepolymer (A), the change in the external environment, particularly the refractive index fluctuation due to the humidity change is small, the characteristics are stable, and the transparency in the optical communication wavelength band is also high. high.
Ratio of the number of C—F bonds (N _F ) to the sum of the number of C—F bonds (N _F ) and the number of C—H bonds (N _H ) in the prepolymer (A) (N _F / (N _F + N _H )) is preferably 0.1 or more, more preferably 0.8 or more, and particularly preferably 1.

  Moreover, since the cured product of the prepolymer (A) has high transparency in the vicinity of a wavelength of 1310 nm, an optical waveguide having good compatibility with existing optical elements can be obtained. In an optical transmission device using a normal silica-based optical fiber, a wavelength of 1310 nm is often used, so that many optical elements such as a light receiving element suitable for the wavelength of use are manufactured, and the reliability is high.

Preferred prepolymers (A) include fluorine-containing aromatic compounds (perfluoro (1,3,5-triphenylbenzene), perfluorobiphenyl, etc.) and phenolic compounds (1,3,5-trihydroxybenzene, 1, 1,1-tris (4-hydroxyphenyl) ethane) and a crosslinkable compound (pentafluorostyrene, acetoxystyrene, chloromethylstyrene, etc.) in the presence of a dehydrohalogenating agent (potassium carbonate, etc.) The polymer obtained by making it include.
A prepolymer (A) may be used individually by 1 type, and may use 2 or more types together.

(Clad)
The clad 20 includes an under clad layer 22 and an over clad layer 24.
The material of the under cladding layer 22 and the material of the over cladding layer 24 are the same as long as the refractive index of the under cladding layer 22 and the refractive index of the over cladding layer 24 are lower than the refractive index of the core 10. May be different.
The thickness c of the under-cladding layer 22 and the thickness d of the over-cladding layer 24 are designed so as to reduce the light loss according to the numerical aperture (NA) value.

The thickness c of the under cladding layer 22 is preferably 5 to 50 μm from the viewpoint of protecting the core 10.
The thickness d of the over clad layer 24 is thicker than the height b of the core 10 and is preferably 15 to 150 μm from the viewpoint of protecting the core 10.
The thickness (c + d) of the clad 20 is preferably 20 to 200 μm.

  The material forming the clad 20 is the prepolymer (A), a compound having a molecular weight of 140 to 5000, a crosslinkable functional group, and no fluorine atom (hereinafter referred to as “compound (B)”). .)).

  The compound (B) has a molecular weight of 140 to 5000, has a crosslinkable functional group, and does not have a fluorine atom. Since it does not have a fluorine atom, the cost is likely to be lower than that of a fluorine-containing compound. If the molecular weight of the compound (B) is 5000 or less, the viscosity of the compound (B) can be kept low, and a uniform composition can be easily obtained when mixed with the prepolymer (A). Also, good flatness can be easily obtained. When the molecular weight of the compound (B) is 140 or more, good heat resistance is obtained, and decomposition and volatilization due to heating hardly occur. The molecular weight range of the compound (B) is preferably 250 to 3000, particularly preferably 250 to 2500.

The crosslinkable functional group of the compound (B) does not contain a fluorine atom, and a reactive functional group that causes a reaction in the same step as the step of reacting the crosslinkable functional group of the prepolymer (A) is preferable.
The crosslinkable functional group of compound (B) reacts with at least compound (B) to cause crosslinking or chain extension. It is preferable that the crosslinkable functional group of the compound (B) reacts with both the prepolymer (A) and the compound (B) to cause crosslinking or chain extension.
As a crosslinkable functional group of a compound (B), the double bond or triple bond in a carbon atom-carbon atom is preferable. However, aromatic double bonds and triple bonds are not included.
The double bond and triple bond as the crosslinkable functional group may exist inside the molecular chain or may exist at the terminal, but preferably exist at the terminal because of high reactivity. In the case of a double bond, it may be an internal olefin or a terminal olefin, but a terminal olefin is preferred. Being inside a molecular chain includes being present in a part of an aliphatic ring such as cycloolefins.
Specifically, it is preferable to include at least one selected from the group consisting of a vinyl group, an allyl group, an ethynyl group, a vinyloxy group, an allyloxy group, an acryloyl group, an acryloyloxy group, a methacryloyl group, and a methacryloyloxy group. Among these, an acryloyl group and an acryloyloxy group are preferable in that the reaction proceeds by light irradiation even in the absence of a photosensitizer.

  The compound (B) preferably has two or more crosslinkable functional groups, more preferably 2 to 20, and particularly preferably 2 to 8. When two or more crosslinkable functional groups are present, the molecules can be cross-linked, so that the heat resistance of the cured film can be improved, and the film thickness reduction due to heating in the cured film can be satisfactorily suppressed.

Specific examples of the compound (B) include dipentaerythritol triacrylate triundecylate, dipentaerythritol pentaacrylate monoundecylate, ethoxylated isocyanuric acid triacrylate, ε-caprolactone-modified tris- (2-acryloxyethyl). Isocyanurate, dipentaerythritol polyacrylate, 9,9-bis [4- (2-acryloyloxyethoxy) phenyl] fluorene, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, polypropylene glycol diacrylate, polypropylene glycol dimethacrylate, ethoxylation Bisphenol A diacrylate, ethoxylated bisphenol A dimethacrylate, propoxylated bisphenol A diacrylate Propoxylated bisphenol A dimethacrylate, 1,10-decanediol diacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, 1,4-butanediol dimethacrylate, 1,3-butanediol diacrylate Methacrylate, hydroxypivalate neopentyl glycol diacrylate, 1,9-nonanediol diacrylate, 1,9-nonanediol dimethacrylate, neopentyl glycol diacrylate, neopentyl glycol dimethacrylate, pentaerythritol triacrylate, trimethylolpropane tri Acrylate, ethoxylated trimethylolpropane triacrylate, propoxylated trimethylolpropane triacrylate, triallyl cyanurate, Triallyl isocyanurate, trimethallyl isocyanurate, 1,4-butanediol divinyl ether, 1,9-nonanediol divinyl ether, cyclohexanedimethanol divinyl ether, triethylene glycol divinyl ether, trimethylolpropane trivinyl ether, pentaerythritol tetra Vinyl ether, 2- (2-vinyloxyethoxy) ethyl acrylate, 2- (2-vinyloxyethoxy) ethyl methacrylate, trimethylolpropane diallyl ether, pentaerythritol triallyl ether, dipentaerythritol hexaacrylate, pentaerythritol tetraacrylate , Ethoxylated pentaerythritol tetraacrylate represented by the following formula (1), propoxy represented by the following formula (2) Pentaerythritol tetraacrylate, ditrimethylolpropane tetraacrylate, tricyclodecane dimethanol diacrylate, tricyclodecane dimethanol methacrylate, compounds represented by the following formula (3). Further, polyester acrylate (compound obtained by modifying both ends of the condensate of dihydric alcohol and dibasic acid with acrylic acid: manufactured by Toagosei Co., Ltd., trade name Aronix (M-6100, M-6200, M-6250, M-6500) ); Compound obtained by modifying the hydroxyl terminal of the condensate of polyhydric alcohol and polybasic acid with acrylic acid: manufactured by Toagosei Co., Ltd., trade name Aronix (M-7100, M-7300K, M-8030, M-8060, M -8100, M-8530, M-8560, M-9050)). These can be obtained from commercial products.
Among the examples mentioned above, polypropylene glycol dimethacrylate and 1,10-decanediol diacrylate are preferable because the moldability of the cured film is good.

The refractive index of the clad 20 is lower than the refractive index of the core 10. The refractive index of the clad 20 can be adjusted by the type of the compound (B) and the mixing ratio of the prepolymer (A) and the compound (B).
Among the examples of the compound (B) listed above, those in which the refractive index of the cured product obtained by curing the compound (B) alone is lower than the refractive index of the cured product obtained by curing the prepolymer (A) alone. By adding this to the prepolymer (A), the refractive index can be lowered as compared with the cured product of the prepolymer (A).
When the compound (B) that increases the refractive index is used, the refractive index of the clad 20 can be made lower than the refractive index of the core 10 by combining with the compound (B) that decreases the refractive index.

Since the clad 20 contains the compound (B) having a relatively low molecular weight, the clad 20 tends to be a uniform layer, and the surface tends to be flat during curing. Further, since the compound (B) undergoes a crosslinking reaction, it contributes to good heat resistance.
The ratio of the prepolymer (A) to the total mass of the prepolymer (A) and the compound (B) contained in the clad 20 is preferably 1 to 97% by mass, more preferably 5 to 50% by mass, and 8 to 35. More preferred is mass%. The higher the prepolymer (A) content, the higher the heat resistance, and the higher the compound (B) content, the better the flatness of the cladding 20 surface.

<Optical waveguide manufacturing method>
Hereinafter, a method for manufacturing the optical waveguide 1 will be described as an example of the method for manufacturing the optical waveguide of the present invention.
[First Embodiment]
The manufacturing method of the optical waveguide 1 of the present embodiment includes the following steps (IA) to (IV-A).
(I-A) As shown in FIG. 2, a step of forming an under cladding layer 22 on a flexible base material 30 (hereinafter simply referred to as “base material 30”).
(II-A) A core-forming resin composition (hereinafter referred to as “composition”) comprising a core-forming resin comprising a prepolymer (A) and a solvent comprising propylene glycol monomethyl ether acetate (hereinafter referred to as “PGMEA”). a) ") is applied onto the underclad layer 22 and prebaked to obtain a laminate 33 in which the core precursor layer 12 is formed on the underclad layer 22.
(III-A) A step of forming the core 10 by exposing and developing the core precursor layer 12 and patterning it.
(IV-A) A step of forming the over clad layer 24 on the under clad layer 22 and the core 10.

Step (IA):
For example, as shown in FIG. 3, a roll 40 around which a base material 30 is wound is prepared, the base material 30 is sent out from the roll 40, and a resin composition for forming an undercladding layer (hereinafter referred to as “undercladding layer forming resin composition”) , Composition (b)) was applied, and baking was performed by heating and / or light irradiation in the baking means 42, thereby forming the under cladding layer 22 on the substrate 30 as shown in FIG. After obtaining the laminated body 31, the protective film 32 sent out from the roll 43 is further laminated on the under cladding layer 22 of the laminated body 31 and wound around the roll 44.

Examples of the substrate 30 include a film-like or sheet-like substrate having flexibility that can be wound around a roll by a roll-to-roll method, and examples thereof include a plastic film and a silicone film. Examples of the plastic film material include polyimide and polyethylene terephthalate.
Moreover, as the protective film 32, the same thing as what was mentioned by the base material 30 is mentioned. By laminating the protective film 32 on the under-cladding layer 22, scratches are generated on the surface of the under-cladding layer 22 by winding dust or dust when wound on a roll, and the under-cladding from the back surface of the base material 30. Transfer to the layer 22 can be prevented.

As the composition (b), for example, a prepolymer (A), a compound (B), and a solvent are included as essential components, and additives such as a thermosetting accelerator, a photosensitizer, and an adhesion improver are added as necessary. The curable composition containing is mentioned.
The solvent used in the composition (b) may be any solvent as long as it can dissolve or disperse the prepolymer (A) and the compound (B). For example, PGMEA, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, pentyl acetate , Isopentyl acetate, isobutyl isobutyrate, methyl-3-methoxypropionate, dipropylene glycol methyl ether acetate, cyclopentanone, cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, dibutyl ketone and the like.

The total proportion of the prepolymer (A) and the compound (B) in the composition (b) (100% by mass) is 1% by mass or more from the viewpoint of adhesion to the core and flexibility when formed into a film. Preferably, 20 mass% or more is more preferable. The ratio is preferably 99% by mass or less, more preferably 30% by mass or less from the viewpoint of cost and light confinement.
The ratio of the prepolymer (A) to the total mass of the prepolymer (A) and the compound (B) in the composition (b) is preferably 1 to 97 mass%, more preferably 5 to 50 mass%, and 8 -35 mass% is further more preferable. The higher the prepolymer (A) content, the higher the heat resistance of the undercladding layer 22, and the higher the compound (B) content, the better the flatness of the surface of the undercladding layer 22.

When baking by heating, the composition (b) may contain a thermosetting accelerator. Examples of the thermosetting accelerator include azobisisobutyronitrile, benzoyl peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, di-tert-butyl peroxide, and dicumyl peroxide.
Moreover, when baking by light irradiation, a composition (b) may contain a photosensitive agent. IRGACURE 907 (α-aminoalkylphenone series), IRGACURE 369 (α-aminoalkylphenone series), DAROCUR TPO (acylphosphine oxide series), IRGACURE OXE01 (oxime ester derivative), IRGACURE OXE02 (oxime ester derivative) ) (Both manufactured by Ciba Specialty Chemicals). Of these, DAROCUR TPO, IRGACURE OXE01, and IRGACURE OXE02 are particularly preferable.
The composition (b) may contain an adhesion improver. Thereby, the adhesiveness of the under clad layer 22 and the layer in contact with it improves. Examples of the adhesion improver include a silane coupling agent.

When the under cladding layer 22 is formed by heating, the heating temperature is preferably 120 to 500 ° C, more preferably 150 to 210 ° C. If the heating temperature is equal to or higher than the lower limit, it is easy to sufficiently crosslink the under cladding layer. If the heating temperature is not more than the upper limit value, it is easy to suppress the material from being scattered or decomposed while sufficiently bridging the undercladding layer.
The heating time is preferably 0.1 to 3 hours.
When the formation of the under cladding layer 22 by light irradiation, accumulated illuminance is preferably ^{10~2000mJ / cm 2, 100~1000mJ / cm} 2 is more preferable. If the integrated illuminance is at least the lower limit value, it is easy to sufficiently crosslink and cure. If the integrated illuminance is less than or equal to the upper limit value, the processing time can be shortened and productivity is improved.

Step (II-A):
As shown in FIG. 4, the laminate 31 in which the under clad layer 22 is protected by the protective film 32 is sent out from the roll 44, and the protective film 32 on the under clad layer 22 is peeled off and wound on the roll 45. The composition (a) is applied on the undercladding layer 22 by the die coater 46, and prebaked by heating in the oven 47 to form the core precursor layer 12 on the undercladding layer 22, as shown in FIG. After obtaining the laminated body 33, the protective film 34 fed from the roll 48 is laminated on the core precursor layer 12 and wound around the roll 49.
When prebaking is performed, a part of the crosslinkable functional group of the prepolymer (A) reacts to form the semi-cured core precursor layer 12. The semi-cured state means a state in which only a part of the curing reaction has progressed and can be dissolved and removed in the developer in the development after exposure in the step (III-A) described later.

The composition (a) is a curable composition containing a core-forming resin composed of the prepolymer (A) and a solvent composed of PGMEA as essential components. The composition (a) may contain additives such as the thermosetting accelerator, the photosensitizer, and the adhesion improver mentioned in the composition (b) as necessary.
The proportion of the prepolymer (A) in the composition (a) (100% by mass) is preferably 20% by mass or more, and preferably 50% by mass or more from the viewpoints of transparency, heat resistance, flexibility, adhesion, and curability. Is more preferable. Moreover, it is preferable that the ratio of the said prepolymer (A) is as large as possible within the range in which the quantity of the solvent which can apply | coat the composition (a) is contained.

When the present inventors examined that the core is likely to crack when the prepolymer (A) is used as the core-forming resin, the pre-baking is more effective than the case where a resin other than the prepolymer (A) is used. In the handling from the formation of the core precursor layer to before the exposure, it has been found that the cause is that the core precursor layer is easily cracked due to bending or the like. In particular, when the roll-to-roll method is employed and there is a step of winding the laminate formed with the core precursor layer around the roll, the core precursor layer is curved by being wound around the roll, so that cracks are likely to occur. . Further examination of this problem has found that the occurrence of cracks in the core precursor layer can be suppressed by controlling the solvent content of the core precursor layer after pre-baking to a specific range.
That is, in this embodiment, in the step (II-A), the mass (unit) of the solvent contained in the core precursor layer 12 after pre-baking with respect to the mass (unit: g) of the dry solid content of the core precursor layer 12. : G), the ratio X is 0.14 to 0.48.

When the ratio X is 0.14 or more, the core precursor layer 12 is cracked when the laminate 33 is handled during manufacturing, such as when the laminate 33 on which the core precursor layer 12 is formed is wound around the roll 49. Is suppressed from occurring. The factors for obtaining such an effect are considered as follows. It is considered that the prepolymer (A) has a property of becoming less flexible and brittle when the amount of the solvent contained in a completely uncured state is smaller than that of other resins. However, by setting the ratio X to 0.14 or more, the core precursor layer 12 is appropriately swollen with a solvent, and sufficient flexibility is obtained for the core precursor layer 12 even after pre-baking. Thereby, the core precursor layer 12 is suppressed from becoming brittle, and it is considered that generation of cracks is suppressed even if the core precursor layer 12 is bent during handling.
In addition, the core precursor layer 12 is less likely to crack as the content of the solvent is larger. However, if the content of the solvent is too large, tacking occurs. By setting the ratio X to 0.48 or less, it is possible to suppress the occurrence of tacking in the core precursor layer 12. The ratio X is preferably 0.37 or less because it can further suppress the occurrence of tacking in the core precursor layer 12.

The ratio X is calculated by performing the following test separately from the manufacturing method of the present invention.
Under the same conditions as the manufacturing method of the specific embodiment of the present invention for which the ratio X is to be obtained, each test piece is prepared in the following steps (x1) and (x2), and its mass is measured.
(X1) A test piece-I in which an under cladding layer is formed on a base material having a predetermined size is prepared, and the mass W ₁ (unit: g) of the test piece-I is measured.
(X2) The composition (a-1) is applied on the underclad layer of the test piece-I, prebaked to obtain the test piece-II, and the mass W ₂ (unit: g) of the test piece-II is measured. .
Thereafter, the core precursor layer of the test piece-II was heated at 190 ° C. for 1 hour to be completely cured (full bake), and the solvent was removed to obtain a test piece-III. The mass W _{3 of the} test piece-III (unit: g) is measured. Then, by subtracting W ₃ from the mass W _2, the mass Y (= W ₂ −W ₃ ) of the solvent contained in the pre-baked core precursor layer is calculated, and the mass W ₁ is subtracted from the mass W ₃ . The mass Z (= W ₃ −W ₁ ) of the dry solid content of the core precursor layer is calculated. Thereafter, the ratio X is calculated by the formula X = Y / Z.
Since the relationship between the ratio of the heating temperature and the heating time in the pre-baking and the ratio X is known from the above test, the ratio X when the pre-baking under the same conditions as the conditions tested in the manufacture of the optical waveguide 1 is known.

The ratio X can be adjusted by adjusting prebaking conditions such as the heating temperature and processing time in the oven 47. The ratio X becomes smaller as the heating temperature is higher and the treatment time is longer.
The prebaking heating temperature is preferably 64 to 108 ° C, more preferably 80 to 90 ° C. If the heating temperature is equal to or higher than the lower limit, the core precursor layer 12 is less likely to be tacked. If heating temperature is below an upper limit, processing time can be shortened and productivity will improve.
The prebaking time is preferably from 0.1 to 10 minutes, more preferably from 0.5 to 2 minutes. If the treatment time is equal to or more than the lower limit value, the core precursor layer 12 is less likely to be tacked, and is easy to dry. When the processing time is less than or equal to the upper limit value, the processing time can be shortened and productivity is improved.

After the pre-baking and forming the core precursor layer 12, the protective film 34 is laminated on the core precursor layer 12 of the obtained laminate 33 and wound around a roll 49. Thereby, even when the laminate 33 is stored for a long time, the volatilization amount of the solvent from the core precursor layer 12 can be further reduced, and the ratio X of the solvent contained in the core precursor layer 12 is maintained within the above range. Easy to do.
As the protective film 34, the plastic film, the silicone film, etc. mentioned in the base material 30 can be used.

Step (III-A):
The core precursor layer 12 on the undercladding layer 22 is exposed and developed through a photomask and patterned to form the core 10 on the undercladding layer 22 as shown in FIG. That is, the core precursor layer 12 is processed by the photolithography method to form the core 10. After development, finishing post-baking may be performed as necessary.
Until the exposure is performed in the step (III-A), the mass ratio X of the solvent in the core precursor layer 12 is controlled within the above range.

  When the protective film 34 transmits light, the core precursor layer 12 may be exposed while the protective film 34 is laminated, or after the protective film 34 is removed. When exposure is performed with the protective film 34 being laminated, a photomask may be disposed on the protective film 34. Further, when the protective film 34 does not transmit light, the exposure is performed after the protective film 34 is removed.

Step (IV-A):
A resin composition for forming an overcladding (hereinafter referred to as “composition (c)”) is applied onto the undercladding layer 22 and the core 10, and heating and / or light irradiation is performed as in the case of the undercladding layer 22. Then, baking is performed to form an overcladding layer 24 as shown in FIG. Thereby, the optical waveguide 1 is obtained. The base material 30 may be peeled off and removed as necessary.
Examples of the composition (c) include the same as those mentioned in the composition (b). The compositions of the composition (b) and the composition (c) may be the same or different as long as the refractive indexes of the under cladding layer 22 and the over cladding layer 24 are lower than the refractive index of the core 10. It may be.
As the heating condition and the light irradiation condition for forming the over cladding layer 24, the same conditions as those for forming the under cladding layer 22 can be adopted.

  The method for forming the over cladding layer 24 on the under cladding layer 22 and the core 10 is not limited to the above method. For example, a cured film to be the over clad layer 24 is once formed on another base material, and the cured film peeled off from the base material is bonded onto the under clad layer 22 and the core 10 by a thermal laminating method. The clad layer 24 may be formed.

[Second Embodiment]
Hereinafter, another embodiment of the method for manufacturing the optical waveguide 1 will be described. The manufacturing method of the optical waveguide 1 of 2nd Embodiment has process (IB)-(IV-B).
(IB) The process of forming the under clad layer 22 on the flexible 1st base material 50 (henceforth "the 1st base material 50" simply) as shown in FIG.
(II-B) The composition (a) is applied onto a flexible second substrate 51 (hereinafter simply referred to as “second substrate 51”), and prebaked to form the core precursor layer 12. Forming step.
(III-B) After laminating the core precursor layer 12 from the second base material 51 on the under cladding layer 22 formed on the first base material 50 by the thermal laminating method, the core precursor layer 12 is A step of forming the core 10 by patterning by exposure and development.
(IV-B) A step of forming the over clad layer 24 on the under clad layer 22 and the core 10.

Step (IB):
For example, in the same manner as in the step (IA) of the first embodiment, a roll around which the first base material 50 is wound is prepared, the first base material 50 is fed out from the roll, and the first coater or the like is used. The undercladding layer 22 is formed on the first substrate 50 as shown in FIG. 5 by applying the composition (b) on the one substrate 50 and baking by heating and / or light irradiation. After obtaining the laminated body 52, a protective film 53 is further laminated on the under cladding layer 22 and wound around a roll.

As the 1st base material 50 and the protective film 53, the same thing as what was mentioned by the base material 30 of 1st Embodiment is mentioned.
Baking conditions such as the heating temperature, the heating time, and the integrated illuminance of light irradiation are the same as the conditions in the step (IA) of the first embodiment.

Step (II-B):
For example, as shown in FIG. 6, a roll 60 around which the second base material 51 is wound is prepared, and the composition (a) is applied by the die coater 61 on the second base material 51 fed out from the roll 60. After applying and pre-baking by heating in an oven 62, as shown in FIG. 5, after obtaining a laminate 54 in which the core precursor layer 12 was formed on the second base material 51, it was fed out from a roll 63. The protective film 55 is laminated on the core precursor layer 12 of the laminated body 54 and wound around the roll 64.

  As the second base material 51, for example, a film-like or sheet-like base material that has flexibility that can be wound around a roll by a roll-to-roll method and that easily peels the formed core precursor layer 12 is used. preferable. Specifically, a release film such as a plastic film having a surface coated with silicone can be used.

Also in the second embodiment, in the step (II-B), the ratio X of the mass of the solvent contained in the core precursor layer 12 after pre-baking with respect to the mass of the dry solid content of the core precursor layer 12 is 0.14. It is characterized by being -0.48. Thereby, it is possible to suppress the occurrence of cracks and tacking in the core precursor layer 12 during handling of the laminate 54 until exposure, and the high-quality optical waveguide 1 free from defects such as cracks in the core 10 can be obtained. Moreover, since it can suppress more that tacking arises in the core precursor layer 12, the upper limit of the ratio X is preferably 0.37.
The preferable aspect of the prebaking conditions such as the heating temperature and processing time in the oven 62 is the same as the preferable aspect of the prebaking conditions in the first embodiment.

The ratio X in the second embodiment is calculated by performing the following test separately from the manufacturing method of the present invention.
The second base material having a predetermined dimension is set as test piece-IV, and the mass W ₄ of the test piece-IV is measured. And the composition (a-1) is apply | coated on test piece-IV on the same conditions as the manufacturing method of the specific embodiment of this invention which is going to obtain | require the ratio X, and it prebakes to make test piece -V. The mass W ₅ (unit: g) of the test piece-V is measured. Thereafter, the core precursor layer of the test piece-V was heated at 190 ° C. for 1 hour to be completely cured (full bake), and the solvent was removed to obtain a test piece-VI. The mass W _{6 of the} test piece- _VI (unit: g) is measured. Then, by subtracting W ₆ from the mass W _5, the mass Y (= W ₅ -W ₆ ) of the solvent contained in the core precursor layer after pre-baking is calculated, and the mass W ₄ is subtracted from the mass W ₆ . The mass Z (= W ₆ -W ₄ ) of the dry solid content of the core precursor layer is calculated. Thereafter, the ratio X is calculated by the formula X = Y / Z.
Since the relationship between the ratio of the heating temperature and the heating time in the pre-baking and the ratio X is known from the above test, the ratio X when the pre-baking under the same conditions as the test conditions is adopted in the manufacture of the optical waveguide 1 is known.

After pre-baking to form the core precursor layer 12, the protective film 55 is laminated on the core precursor layer 12 of the obtained laminate 54 and wound around a roll 64. Thereby, even when the laminated body 54 is stored for a long time, the volatilization amount of the solvent from the core precursor layer 12 can be further reduced, and the ratio X of the solvent contained in the core precursor layer 12 is maintained within the above range. Easy to do.
As the protective film 55, the plastic film, the silicone film, etc. mentioned in the base material 30 of the first embodiment can be used.

Step (III-B):
The core precursor layer 12 of the laminate 54 is laminated by the thermal lamination method on the under clad layer 22 side of the laminate 52, and the first substrate 50, the under clad layer 22 and the core precursor layer 12 are laminated. After obtaining the body 56, the core precursor layer 12 is exposed and developed through a photomask and patterned in the same manner as in the step (III-A) of the first embodiment to form the core 10.
The specific procedure for laminating the core precursor layer 12 is not particularly limited as long as the laminated body 56 in which the core precursor layer 12 is laminated on the under clad layer 22 side of the laminated body 52 is obtained. For example, as shown in FIG. 7, the laminate 52 from which the protective film 53 has been peeled off and the laminate 54 from which the protective film 55 has been peeled off are bonded by a thermal lamination method so that the core precursor layer 12 and the underclad layer 22 face each other. Method (B-1) of combining, the laminate 52 from which the protective film 53 has been peeled off, the laminate of the core precursor layer 12 and the protective film 55 from which the second base material 51 has been peeled off, the core precursor layer 12 and the underclad The method (B-2) etc. which are bonded together by the heat laminating method so that the layer 22 may face each other are mentioned. In both the method (B-1) and the method (B-2), the second substrate 51 or the protective film 55 in the obtained laminate is a protective film that protects the core precursor layer 12 of the laminate 56. May be laminated as they are, or may be peeled off.

When the second substrate 51 or the protective film 55 transmits light, the exposure and development are performed in a state where the second substrate 51 or the protective film 55 is laminated on the core precursor layer 12 of the laminate 56. Also good.
After development, finishing post-baking may be performed as necessary.

  The temperature at which the laminate 52 and the core precursor layer 12 are thermally laminated is such that the reaction of the crosslinkable functional group of the prepolymer (A) in the core precursor layer 12 does not proceed excessively, and the patterning accuracy by exposure and development is high. As long as it is within a range that does not impair. Specifically, 40-120 degreeC is preferable.

Step (IV-B):
The over clad layer 24 is formed on the under clad layer 22 and the core 10 in the same manner as in the step (IV-A) of the first embodiment. The first substrate 50 may be peeled off and removed as necessary.

According to the optical waveguide manufacturing method of the present invention described above, the ratio X of the mass of the solvent contained in the core precursor layer to the mass of the dry solid content of the core precursor layer is controlled within a specific range. By doing so, it can suppress that a crack and tacking arise in a core precursor layer at the time of handling during manufacture. Therefore, a high-quality optical waveguide having no defects such as cracks in the core can be stably obtained.
When the roll-to-roll method is employed and the laminate having the core precursor layer formed thereon is temporarily wound around a roll before exposure, the core precursor layer is curved by being wound around the roll and the core precursor is curved. The possibility of cracks in the body layer is increased. However, the method for manufacturing an optical waveguide according to the present invention is particularly effective in manufacturing an optical waveguide that adopts a roll-to-roll method because cracks can be suppressed even in this case.

  The manufacturing method of the optical waveguide of the present invention is not limited to the method described above. For example, it may be a method that does not include a step of winding the laminated body on which the core precursor layer is formed once on a roll before exposure. Moreover, the method which does not laminate | stack a protective film on a core precursor layer may be sufficient as long as the said ratio X can be controlled in the said range until exposure. Further, the coating method of the compositions (a) to (c) may be other methods such as spin coating.

EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by the following description.
(Prepolymer (A1-1))
In N, N-dimethylacetamide (hereinafter referred to as “DMAc”), perfluorobiphenyl and 1,3,5-trihydroxybenzene were reacted in the presence of potassium carbonate, followed by 4-acetoxystyrene. A prepolymer was synthesized by reaction in the presence of potassium hydroxide. The obtained DMAc solution of the prepolymer was poured into an aqueous hydrochloric acid solution for purification by reprecipitation, followed by vacuum drying to obtain a powdery prepolymer (A1-1).

(Composition (a-1))
48 g of prepolymer (A1-1), 0.0144 g of 4-tert-butylcatechol (TBC) as a stabilizer, and 52 g of PGMEA as a solvent are placed in a sample bottle and mixed for 72 hours at room temperature using a mix rotor. Then, the mixture was filtered using a filtration device (Millipore Corporation, filter pore size: 5 μm) to obtain a composition (a-1).

(Composition (b-1))
48 g of prepolymer (A1-1), 192 g of polypropylene glycol # 400 (9PG) as compound (B), 52 g of benzoyl peroxide (manufactured by NOF Corporation) as a thermosetting accelerator, and 0.08 of TBC as a stabilizer. 0144 g and 52 g of PGMEA as a solvent were placed in a sample bottle, mixed at room temperature for 72 hours using a mix rotor, and then filtered using a filtration device (Millipore, filter pore size: 5 μm). A composition (b-1) was obtained.

The following tests were performed on the ratio X of the mass of the solvent contained in the core precursor layer after pre-baking to the dry solid content of the core precursor layer and the occurrence of cracks and tacking in the core precursor. It was.
[Example 1]
A polyethylene terephthalate (PET) film (length 300 mm × width 150 mm × thickness 188 μm) is used as a flexible substrate, and the composition (b-1) is applied to the surface by a die coater and heated at 190 ° C. for 1 hour. Then, an under clad layer having a thickness of 15 μm was formed on the PET film to obtain a test piece-I. Mass A (W ₁ ) of the obtained Specimen-I was 1.0727 g.
Next, the composition (a-1) was applied on the undercladding layer of the obtained test piece-I with a die coater so as to have a thickness of 120 μm, to obtain a test piece-IA. The mass B of the laminate-IA was 1.4265 g. Thereafter, the test piece-IA was pre-baked by heating at 100 ° C. for 5 minutes to obtain a test piece-II in which the core precursor layer was formed on the undercladding layer. Winded up. The mass C (W ₂ ) of the test piece-II after prebaking was 1.2965 g.
Subsequently, test piece-II was pulled out from the roll and heated at 190 ° C. for 1 hour to completely cure the core precursor layer (full bake), and the solvent was removed to obtain test piece-III. The mass D (W ₃ ) of the test piece-III after full baking was 1.2486 g.

[Examples 2-28]
The prebaking heating temperature when forming the core precursor layer is changed as shown in Tables 1 to 3, and the ratio X of the solvent contained in the core precursor layer after prebaking is changed as shown in Tables 1 to 3. In the same manner as in Example 1, after preparing a laminate having a core precursor layer formed thereon and winding it on a roll, the core precursor layer was drawn out from the roll and completely cured (full bake) to remove the solvent. After removing, the masses A to D were measured.

(Calculation method of ratio X etc.)
The mass Y (= C−D) of the solvent contained in the core precursor layer after pre-baking and the mass Z (= D−A) of the dry solid content of the core precursor layer are calculated, and the formula X = Y / Z The ratio X was calculated by In addition to the ratio X, the following ratios G, H, and I were calculated.
Ratio G (G = 1−F / E): The ratio of the mass of the solvent removed by prebaking with respect to the coating amount of the composition (a-1).
Ratio H (H = 1−Z / E): The ratio of the mass of the solvent contained in the core precursor layer with respect to the coating amount of the composition (a-1).
Ratio I (I = Y / F): The ratio of the mass of the solvent contained in the core precursor layer after pre-baking to the mass of the core precursor layer after pre-baking.

[Evaluation method]
About the laminated body obtained by each example, the presence or absence of the crack of a core precursor layer after full baking and a tack was confirmed, and the following references | standards evaluated. Evaluation of tacking ○: The surface is smooth.
[Delta]: After touching, there is no problem in manufacturing.
×: Sticky
2. Evaluation of cracks ○: The film surface does not crack even when wound around a 3-inch core.
Δ: Even when wound around a 6-inch core, the film surface does not crack, but when wound around a 3-inch core, the film surface cracks.
X: The film surface is cracked by being wound around a 6-inch core.
The results of each example are shown in Tables 1-3.

  As shown in Tables 1 to 3, in Examples 24 to 28 in which the ratio X is smaller than 0.14, the core precursor layer is cracked by winding the laminate on which the core precursor layer is formed on a roll. On the other hand, generation of cracks was suppressed in Examples 1 to 23 in which the ratio X was 0.14 or more. Furthermore, in Examples 1 to 23 in which the ratio X was 0.48 or less, the occurrence of tacking was also suppressed, and in particular in Examples 5 to 23 in which the ratio X was 0.37 or less, the occurrence of tacking was suppressed.

DESCRIPTION OF SYMBOLS 1 Optical waveguide 10 Core 12 Core precursor layer 20 Clad 22 Under clad layer 24 Over clad layer 30 Flexible base material 50 Flexible 1st base material 51 Flexible 2nd base material

Claims (6)

Forming an underclad layer on a flexible substrate (I-A);
A core-forming resin comprising a fluorine-containing polyarylene prepolymer having a crosslinkable functional group and a core-forming resin composition comprising a solvent comprising propylene glycol monomethyl ether acetate are applied onto the undercladding layer and prebaked. A step (II-A) of obtaining a laminate in which a core precursor layer is formed on the underclad layer;
Step (III-A) of exposing and developing the core precursor layer and patterning to form a core;
Forming an overcladding layer on the undercladding layer and the core (IV-A),
The manufacturing method of the optical waveguide which sets ratio X of the mass of the solvent contained in the core precursor layer after a prebaking with respect to the dry solid content mass of the said core precursor layer as 0.14-0.48.   The method for manufacturing an optical waveguide according to claim 1, wherein the ratio X is 0.14 to 0.37.   The method for producing an optical waveguide according to claim 1, further comprising a step of winding a laminated body in which a core precursor layer is formed on the under-cladding layer onto a roll before exposure. Forming an underclad layer on the flexible first substrate (IB);
A core-forming resin comprising a fluorine-containing polyarylene prepolymer having a crosslinkable functional group and a core-forming resin composition comprising a solvent comprising propylene glycol monomethyl ether acetate are applied onto a flexible second substrate, Performing pre-baking to obtain a laminate in which a core precursor layer is formed on the second substrate (II-B);
After laminating the core precursor layer of the laminate in which the core precursor layer is formed on the second base material on the under clad layer formed on the first base material by a thermal laminating method, A step of exposing and developing the core precursor layer and patterning to form a core (III-B);
And forming an over clad layer on the under clad layer and the core (IV-B),
The manufacturing method of the optical waveguide which sets ratio X of the mass of the solvent contained in the core precursor layer after a prebaking with respect to the dry solid content mass of the said core precursor layer as 0.14-0.48.   The method for manufacturing an optical waveguide according to claim 4, wherein the ratio X is 0.14 to 0.37.   6. The method for manufacturing an optical waveguide according to claim 4, further comprising a step of winding a laminate in which a core precursor layer is formed on the second base material around a roll.

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