Method for manufacturing optical waveguide

Abstract

To provide a method for manufacturing an optical waveguide which has low transmission loss, and can suppress positional deviation of a core part when a needle-like part is extracted.SOLUTION: A method for manufacturing an optical waveguide includes a first step of implanting a needle-like part at the tip of a discharge part into an uncured clad part formed of a photosensitive resin composition for a clad, a second step of relatively moving the needle-like part in an uncured clad part, while discharging the photosensitive resin composition for the core from the needle-like part, and forming an uncured core part whose periphery is coated in the uncured clad part, a third step of extracting the needle-like part from the uncured clad part, and a fourth step of curing the uncured clad part and the uncured core part, wherein the photosensitive resin composition for the core and the photosensitive resin composition for the clad contain one or more kinds of (meth)acrylate resins selected from the group consisting of an urethane (meth)acrylate resin and an epoxy (meth)acrylate resin.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an optical waveguide.

Background Art

[0002] In recent years, in anticipation of high-capacity information transmission, research on transmission using optical signals has been actively conducted. With the progress of these studies, it is considered that conventional electronic circuits will be gradually replaced by optical circuits. Therefore, a co-packaged optics (CPO) circuit in which optical and electrical circuits are mixed is regarded as promising.

[0003] In order to achieve high-speed transmission, as an optical waveguide for forming an optical circuit, a single-mode optical waveguide is desirable. For a single-mode optical waveguide, in addition to reducing the loss of the optical waveguide, the formation of a flexible optical waveguide and the accurate alignment of the optical waveguide are required. In order to form an optical waveguide that satisfies these requirements, the formation of an optical waveguide by the mosquito method has been studied (Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the mosquito method, generally, an optical waveguide is manufactured using an application device including a discharge portion having a needle-like portion capable of discharging an uncured core material at its tip. Specifically, the needle-like portion is inserted into the uncured clad portion. Then, while moving the needle-like portion within the clad portion, the core material is discharged from the needle-like portion. The discharged core material forms an uncured core portion within the clad portion. Thereafter, the discharge of the core portion is stopped, the needle-like portion is removed, and then the core portion and the clad portion are cured to obtain an optical waveguide. In this mosquito method, it is expected that a core portion with a free design according to the movement path of the needle-like portion can be formed within the clad portion.

[0006] However, in the conventional mosquito method, when the needle-like portion was removed from the clad portion, stringing of the core material occurred. This "stringing" of the core material refers to a phenomenon in which a part of the core material discharged into the clad portion (usually, the end portion of the core portion close to the needle-like portion) extends in a string-like manner. When stringing occurs, since the core material moves as if it is pulled by the needle-like portion, the core portion cannot stay at the desired position in the moved portion, which may cause misalignment. Therefore, in order to form the core portion with high positional accuracy, it is desired to suppress the misalignment when removing the needle-like portion as described above while achieving the low transmission loss required for the optical waveguide.

[0007] The present invention was conceived in view of the above problems, and an object thereof is to provide a method for manufacturing an optical waveguide that has low transmission loss and can suppress misalignment of the core portion when removing the needle-like portion.

Means for Solving the Problems

[0008] The present inventor earnestly studied to solve the above problems. As a result, the present inventor found that the above problems can be solved when using a core photosensitive resin composition containing a specific type of (meth)acrylate resin and a clad photosensitive resin composition containing a specific type of (meth)acrylate resin for the mosquito method, and completed the present invention. That is, the present invention includes the following.

[0009] <1> A first step of piercing a needle-like portion at the tip of a discharge portion into an uncured clad portion formed of a photosensitive resin composition for a clad; A second step of discharging a photosensitive resin composition for a core from the needle-like portion while relatively moving the needle-like portion within the uncured clad portion to form an uncured core portion surrounded by the uncured clad portion in the uncured clad portion; A third step of removing the needle-like portion from the uncured clad portion; A fourth step of curing the uncured clad portion and the uncured core portion, which is a method for manufacturing an optical waveguide; The photosensitive resin composition for a core contains one or more (meth)acrylate resins selected from the group consisting of urethane (meth)acrylate resins and epoxy (meth)acrylate resins, A method for manufacturing an optical waveguide, wherein the photosensitive resin composition for a clad contains one or more (meth)acrylate resins selected from the group consisting of urethane (meth)acrylate resins and epoxy (meth)acrylate resins. <2> The method for manufacturing an optical waveguide according to <1>, wherein the (meth)acrylate resin contained in the photosensitive resin composition for a core contains one or more selected from the group consisting of a urethane (meth)acrylate resin containing a polyether skeleton and an epoxy (meth)acrylate resin containing a bisphenol A skeleton. <3> The method for manufacturing an optical waveguide according to <1> or <2>, wherein the photosensitive resin composition for a core contains 70% by mass or more of a (meth)acrylate resin with respect to 100% by mass of the non-volatile components of the photosensitive resin composition for a core. <4> The method for manufacturing an optical waveguide according to any one of <1> to <3>, wherein the photosensitive resin composition for a clad contains 70% by mass or more of a (meth)acrylate resin with respect to 100% by mass of the non-volatile components of the photosensitive resin composition for a clad. <5> Parameter D represented by the following formula (1) clad is 400 or more and 5000 or less, and is the method for manufacturing an optical waveguide according to any one of <1> to <4>.

Equation

Advantages of the Invention

[0010] The present invention can provide a method for manufacturing an optical waveguide with low transmission loss and capable of suppressing displacement of the core portion during removal of the needle-like portion.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

[0012] Hereinafter, the present invention will be described in detail with reference to embodiments and examples. However, the present invention is not limited to the embodiments and examples described below, and can be arbitrarily modified and implemented without departing from the scope of the claims and their equivalents.

[0013] In the following description, unless otherwise specified, the term “(meth)acrylic acid” includes acrylic acid, methacrylic acid, and combinations thereof, and the term “(meth)acrylate” includes acrylate, methacrylate, and combinations thereof.

[0014] <Outline of Manufacturing Method of Optical Waveguide> In a method for manufacturing an optical waveguide according to an embodiment of the present invention, an optical waveguide is manufactured using a coating apparatus including a discharge portion having a needle-like portion capable of discharging a photosensitive resin composition for a core at its tip. This manufacturing method includes a first step of inserting the needle-like portion at the tip of the discharge portion into an uncured clad portion formed of a photosensitive resin composition for a clad, a second step of discharging the photosensitive resin composition for a core from the needle-like portion while relatively moving the needle-like portion within the clad portion to form an uncured core portion surrounded by the uncured clad portion, a third step of removing the needle-like portion from the uncured clad portion, a fourth step of curing the uncured clad portion and the uncured core portion include in this order. Moving the needle-shaped portion "relatively" within the clad portion in the second step means changing the position of the needle-shaped portion relative to the clad portion. Therefore, the needle-shaped portion may move while the clad portion is fixed, or the clad portion may move while the needle-shaped portion is fixed.

[0015] According to the above manufacturing method, an optical waveguide including a core portion and a clad portion can be manufactured. The core portion is formed in the clad portion. Therefore, the periphery of the core portion is covered by the clad portion. The core portion and the clad portion are in direct contact with each other without another layer therebetween. At this time, an interface may or may not be formed between the core portion and the clad portion. When an interface is formed, usually, a step-index type (SI type) optical waveguide capable of transmitting light by reflection at the interface can be obtained. On the other hand, when no interface is formed, usually, a graded-index type (GI type) optical waveguide in which the refractive index continuously decreases from the center of the core portion to the outer peripheral portion with the center of the core portion as the maximum value can be obtained. According to the above manufacturing method, in many cases, a graded-index type optical waveguide can be manufactured, but a step-index type optical waveguide may also be manufactured.

[0016] In this embodiment, a photosensitive resin composition for a core containing a specific type of (meth)acrylate resin and a photosensitive resin composition for a clad containing a specific type of (meth)acrylate resin are used in combination. By using this combination of the photosensitive resin composition for a core and the photosensitive resin composition for a clad, when the needle-shaped portion is removed from the uncured clad portion in the third step, displacement of the core portion can be suppressed. Further, the transmission loss of the manufactured optical waveguide can be reduced. Furthermore, according to the manufacturing method according to this embodiment, preferably, the adhesion between the clad portion of the manufactured optical waveguide and the support can be improved, and the warping of the optical waveguide can be suppressed.

[0017] In the manufacturing method according to this embodiment, between the third step and the fourth step, the first step, the second step, and the third step may be repeatedly performed as a series of steps. In this case, after forming a plurality of uncured core portions by repeating the first step, the second step, and the third step, the uncured clad portion and the uncured core portion are cured in the fourth step.

[0018] <First step> The manufacturing method according to this embodiment includes a first step of inserting a needle-like portion at the tip of a discharge portion into an uncured clad portion formed of a photosensitive resin composition for a clad. Usually, this first step is performed after performing a step of preparing a support for supporting the uncured clad portion and a step of forming the uncured clad portion on the support. The uncured clad portion is formed of a photosensitive resin composition for a clad, but since this photosensitive resin composition for a clad is generally a liquid or gel-like composition, it usually does not have self-supporting properties. Therefore, a support is prepared, and an uncured clad portion is formed on the support.

[0019] FIG. 1 is a cross-sectional view schematically showing a support 100 used in the manufacturing method according to an embodiment of the present invention. As shown in FIG. 1, the support 100 includes a base material 110 and a frame portion 120 provided on the base material 110.

[0020] As the base material 110, a member having a surface 110U for supporting an uncured clad portion is usually used, and the frame portion 120 is provided on the surface 110U. There is no particular limitation on the planar shape of the base material 110, but it is generally rectangular. The "planar shape" represents the shape seen from the thickness direction unless otherwise specified. The surface 110U of the base material 110 preferably has high flatness. As the material of the base material 110, for example, resin, glass, silicon, ceramics, metal, etc. can be used. From the viewpoint of incorporating an optical waveguide into an optoelectronic integrated circuit, a circuit board having an electric circuit such as a printed wiring board or a semiconductor chip package may be used as the base material 110. In this embodiment, an example in which a rectangular plate material is used as the base material 110 will be described.

[0021] The frame portion 120 is a frame material provided so as to surround a portion of the surface 110U for forming an uncured clad portion. Usually, this frame material 120 has a rectangular planar shape and has an opening 120a for supplying the uncured clad portion. In the present embodiment, an example will be described in which the frame portion 120 is provided at the peripheral edge portion of the base material 110 so as to surround the entire circumference of the central portion of the base material 110 (the portion for forming the clad portion in this example) as viewed in the thickness direction. The frame portion 120 may be detachably provided on the base material 110. Examples of the material of the frame portion 120 include, for example, the same material as that of the base material 110. The material of the base material 110 and the material of the frame portion 120 may be the same or different.

[0022] FIG. 2 is a schematic cross-sectional view for explaining the operation of the first step in the manufacturing method according to an embodiment of the present invention. After preparing the support 100, as shown in FIG. 2, an uncured clad portion 210 is formed at a portion of the surface 110U of the base material 110 surrounded by the frame portion 120. Usually, the photosensitive resin composition for clad is supplied through the opening 120a to the portion surrounded by the frame portion 120 using a supply device such as a coating device (dispenser, etc.) or a printing device. The photosensitive resin composition for clad is generally liquid, but since it is blocked by the frame portion 120, an uncured clad portion 210 can be formed within the frame portion 120. If necessary, the supplied photosensitive resin composition for clad may be spread uniformly to make the thickness of the uncured clad portion 210 uniform. For a specific example, the clad portion 210 may be rubbed with a rubbing material such as a squeegee or a flat plate to make the thickness of the uncured clad portion 210 uniform.

[0023] The formed uncured clad portion 210 contains the photosensitive resin composition for clad and usually contains only the photosensitive resin composition for clad. The thickness of this uncured clad portion 210 may be set according to the diameter of the core portion and the manufacturing conditions, and may be, for example, 50 μm to 1,000 μm.

[0024] FIG. 3 is a schematic cross-sectional view for explaining the operation of the first step in the manufacturing method according to an embodiment of the present invention. After forming the uncured clad portion 210, as shown in FIG. 3, the needle-like portion 310 is inserted into the uncured clad portion 210. Specifically, it is as follows.

[0025] Prepare a coating device (not shown) including a discharge unit 300 including a discharge unit main body 320 and a needle-like portion 310. Usually, the coating device includes an arithmetic device such as a CPU and a storage device such as a memory. And the coating device is provided so that the discharge unit 300 can be relatively moved at a desired moving speed with respect to the uncured clad portion 210 according to a program. The coating device may fix the support 100 and move the discharge unit 300, or may fix the discharge unit 300 and move the support 100. Further, the coating device is provided so that the photosensitive resin composition for the core can be discharged from the needle-like portion 310 included in the discharge unit 300 at a desired discharge pressure. Such a coating device can be configured to include, for example, a desktop coating robot, a dispenser, and the like. In the present embodiment, an example will be described in which a coating device provided so that the discharge unit 300 can be moved in any of the X direction perpendicular to the thickness direction, the Y direction perpendicular to both the thickness direction and the X direction, and the Z direction as the thickness direction is used.

[0026] The needle-like portion 310 is provided at the tip of the discharge unit 300. Further, the needle-like portion 310 is provided so that the photosensitive resin composition for the core can be discharged from the tip portion 311 of the needle-like portion 310. In the present embodiment, an example in which a thin tubular needle is used as the needle-like portion 310 will be described. The cross-sectional shape of the needle-like portion 310 may be, for example, an annular shape, a square shape, or other shapes. When the cross-sectional shape of the needle-like portion 310 is an annular shape, its inner diameter may be set according to the diameter of the core portion to be formed, and may be, for example, 50 μm to 500 μm.

[0027] In the first step, after preparing the uncured clad portion 210, a part of the needle-shaped portion 310 is inserted into the uncured clad portion 210. Specifically, the needle-shaped portion 310 is inserted so that the tip portion 311 of the needle-shaped portion 310 reaches a desired depth within the uncured clad portion 210. The depth within the uncured clad portion 210 can be represented, for example, by the height H1 from the surface 110U of the base material 110 of the support 100 to the tip portion 311 of the needle-shaped portion 310. This height H1 can be set, for example, in the range of 100 μm to 1,000 μm.

[0028] <Second Step> FIG. 4 is a schematic cross-sectional view for explaining the operation of the second step in the manufacturing method according to an embodiment of the present invention. The manufacturing method according to the present embodiment includes, after the first step, as shown in FIG. 4, a second step of relatively moving the needle-shaped portion 310 within the uncured clad portion 210 as indicated by the arrow A1 while discharging the core photosensitive resin composition from the needle-shaped portion 310. In this second step, an uncured core portion 410 is formed by the core photosensitive resin composition discharged from the needle-shaped portion 310. The formed uncured core portion 410 contains the core photosensitive resin composition and usually contains only the core photosensitive resin composition. Generally, since the core photosensitive resin composition is a liquid or gel-like composition, according to the discharged core photosensitive resin composition, a continuous uncured core portion 410 can be formed.

[0029] In the second step, the tip portion 311 of the needle-shaped portion 310 moves within the uncured clad portion 210, and the uncured core portion 410 can be formed so as to trace the locus of the movement of the tip portion 311. Therefore, the uncured core portion 410 is formed within the uncured clad portion 210 from the starting point 410S where the needle-shaped portion 310 starts moving to the ending point 410E where the movement stops. Therefore, the uncured core portion 410 is obtained in a state of being surrounded by the uncured clad portion 210.

[0030] FIG. 5 is a plan view schematically showing a state of the clad portion 210 after the uncured core portion 410 is formed in the second step of the manufacturing method according to an embodiment of the present invention, as viewed in the thickness direction. In FIG. 5, illustration of the discharge portion 300 is omitted. There is no particular limitation on the moving direction of the needle-like portion 310, and it can be set according to the shape of the core portion 410 to be formed. For example, as shown in FIG. 5, the needle-like portion 310 may be moved in one direction to form a linear core portion 410. Also, the moving direction of the needle-like portion 310 may be changed in the in-plane direction and the thickness direction to form a curved or bent core portion (not shown). The "in-plane direction" represents a direction perpendicular to the thickness direction unless otherwise specified.

[0031] The moving speed of the needle-like portion 310 can be appropriately set according to physical properties such as the viscosities of the photosensitive resin composition for the core and the photosensitive resin composition for the clad, and the diameter of the uncured core portion 410 to be formed. The above-mentioned moving speed may be, for example, 5 mm / second to 30 mm / second. During the movement period of the needle-like portion 310, the moving speed may be constant or may be changed. For example, when the moving speed of the needle-like portion 310 is constant, a core portion 410 having a uniform diameter can be formed. On the other hand, when the moving speed of the needle-like portion 310 is changed, a core portion 410 having partially different diameters can be formed.

[0032] The discharge pressure of the photosensitive resin composition for the core discharged from the needle-like portion 310 can be appropriately set according to physical properties such as the viscosities of the photosensitive resin composition for the core and the photosensitive resin composition for the clad, and the diameter of the uncured core portion 410 to be formed. The above-mentioned discharge pressure may be, for example, 10 kPa to 1,000 kPa. During the movement period of the needle-like portion 310, the discharge pressure may be constant or may be changed. For example, when the discharge pressure of the photosensitive resin composition for the core is constant, a core portion 410 having a uniform diameter can be formed. On the other hand, when the discharge pressure of the photosensitive resin composition for the core is changed, a core portion 410 having partially different diameters can be formed.

[0033] Generally, the second step can be carried out at room temperature, or it may be carried out by adjusting the temperature with a temperature control device (not shown) such as a cooling plate. In particular, when forming a core portion 410 with a small diameter of 10 μm or less, the second step is preferably carried out at 10°C to 20°C.

[0034] As shown in FIG. 4, in the second step, after the needle-like portion 310 reaches the end point 410E, the needle-like portion 310 may be held at the end point 410E. That is, the second step may include maintaining the needle-like portion 310 in a stopped state without moving it at the end point 410E. The period of maintaining the stopped state is preferably 0.1 second or more, more preferably 0.3 second or more, preferably 5 seconds or less, and more preferably 2 seconds or less. By holding the needle-like portion 310 in the stopped state in this way, the photosensitive resin composition for the core discharged from the needle-like portion 310 can be stabilized, and displacement can be effectively suppressed.

[0035] <Third Step> FIG. 6 is a schematic cross-sectional view for explaining the operation of the third step in the manufacturing method according to an embodiment of the present invention. The manufacturing method according to this embodiment includes a third step of removing the needle-like portion 310 from the uncured clad portion 210 after the second step, as shown in FIG. 6. Usually, the discharge portion 300 is moved relative to the clad portion 210 in the thickness direction to remove the needle-like portion 310. Therefore, the removal of the needle-like portion 310 may be carried out by moving the needle-like portion 310 with the clad portion 210 fixed, or by moving the clad portion 210 with the needle-like portion 310 fixed. Since the clad portion 210 is uncured when the needle-like portion 310 is removed, usually no trace of the removal remains on the uncured clad portion 210 even when the needle-like portion 310 is removed.

[0036] In this embodiment, the displacement of the core portion 410 that may occur when the needle-like portion 310 is removed in this way can be suppressed. Hereinafter, the suppression of this displacement will be described with reference to the drawings. FIG. 7 is a cross-sectional view schematically showing an enlarged view of the vicinity of the end point 410E of the uncured core portion 410 formed in the uncured clad portion 210 according to an example. As shown in FIG. 7, when the needle-shaped portion 310 is removed, the core portion 410 may be stretched by the needle-shaped portion 310, resulting in wire drawing. When such wire drawing occurs, a displacement portion 411 may occur in the vicinity of the end point 410E where the position of the core portion 410 has moved from the position before removal. This displacement portion 411 deviates from its original position. Also, usually, the displacement portion 411 is stretched and its diameter may be unintentionally reduced. Therefore, since such a displacement portion 411 does not match the design in terms of position and dimensions, it is desirable to reduce its size. In this regard, in the present embodiment, it is possible to reduce the displacement portion 411. Specifically, the length L of the displacement portion 411 can be reduced, for example, the length L can be made 1 mm or less.

[0037] The inventor speculates as follows about the mechanism by which the length L of the displacement portion 411 can be reduced as described above. However, the present invention is not limited by the following mechanism. The types of (meth)acrylate resins contained in the core photosensitive resin composition and the clad photosensitive resin composition generally have a flexible molecular backbone and few branched structures in the molecule, so the degree of entanglement between the molecules is small. Therefore, even when the uncured core portion 410 is pulled when the needle-shaped portion 310 is removed, the scale of wire drawing in the uncured core portion 410 is small. Therefore, the displacement portion 411 that may be caused by such wire drawing can be reduced.

[0038] The moving speed of the needle-shaped portion 310 during removal can be appropriately set according to the physical properties such as the viscosity of the core photosensitive resin composition and the clad photosensitive resin composition, and the diameter of the uncured core portion 410. The moving speed may be, for example, 10 mm / second to 200 mm / second.

[0039] <Repeating the first to third steps> FIG. 8 is a plan view schematically showing a state of a clad portion 210 immediately before a fourth step in a manufacturing method according to an embodiment of the present invention, as viewed in the thickness direction. The manufacturing method according to the present embodiment includes, before the fourth step, a first step of inserting a needle-like portion 310 into an uncured clad portion 210 as shown in FIG. 3, a second step of forming an uncured core portion 410 as shown in FIG. 4, and a third step of removing the needle-like portion 310 from the uncured clad portion 210 as shown in FIG. 6. By repeating these steps, a plurality of uncured core portions 410 may be formed as shown in FIG. 8. The plurality of uncured core portions 410 may be formed of a core photosensitive resin composition having the same composition or may be formed of core photosensitive resin compositions having different compositions.

[0040] When forming a plurality of uncured core portions 410, there is no limitation on the arrangement of the uncured core portions 410. For example, as shown in FIG. 8, the plurality of core portions 410 may be formed side by side so as to extend in the same direction. When forming a plurality of core portions 410, the range of the pitch of the core portions 410 can be, for example, 20 μm to 300 μm. The pitch of the core portions 410 may be uniform or non-uniform in the optical waveguide.

[0041] <Fourth step> FIG. 9 is a schematic cross-sectional view for explaining the operation of the fourth step in a manufacturing method according to an embodiment of the present invention. The manufacturing method according to the present embodiment includes a fourth step of curing the uncured clad portion 210 and the uncured core portion 410 after the third step. By curing the uncured clad portion 210, a cured clad portion 200 can be obtained. Also, by curing the uncured core portion 410, a cured core portion 400 can be obtained. Therefore, as shown in FIG. 9, an optical waveguide 500 including a cured clad portion 200 and a cured core portion 400 is obtained.

[0042] In this embodiment, the uncured clad portion 210 and the uncured core portion 410 contain a photosensitive resin composition. Usually, the photosensitive resin composition can be cured by irradiation with light. Therefore, the fourth step generally includes irradiating the uncured clad portion 210 and the uncured core portion 410 with actinic rays to cure these clad portion 210 and core portion 410. Examples of the actinic rays include ultraviolet rays, electron beams, X-rays, etc., and ultraviolet rays are preferred. Examples of the light source used for ultraviolet irradiation include sunlight, chemical lamps, low-pressure mercury lamps, high-pressure mercury lamps, metal halide lamps, xenon lamps, UV-LEDs, etc.

[0043] The fourth step may further include performing a heat treatment (post-bake treatment) after irradiation with actinic rays. According to the heat treatment, the curing of the clad portion 210 and the core portion 410 can be further advanced. The heat treatment can be performed using a heating device such as a hot plate or an oven. In one example, the heating temperature can be 50°C to 300°C and the heating time can be 1 minute to 120 minutes.

[0044] <Photosensitive resin composition for core> The photosensitive resin composition for core used in the above-described manufacturing method contains a (meth)acrylate resin as the component (A). The (meth)acrylate resin includes acrylate resin, methacrylate resin, and combinations thereof, and generally represents a resin containing a (meth)acryloyl group. However, acrylic acid and methacrylic acid are not included in the (meth)acrylate resin. Here, the term "(meth)acryloyl group" includes an acryloyl group and a methacryloyl group. The (meth)acrylate resin may contain only an acryloyl group, only a methacryloyl group, or a combination of an acryloyl group and a methacryloyl group in its molecule. The photosensitive resin composition for core containing the (A)(meth)acrylate resin can be cured by the reaction of the (meth)acryloyl group in the fourth step.

[0045] (A) The (meth)acrylate resin contains one or more selected from the group consisting of urethane (meth)acrylate resin and epoxy (meth)acrylate resin.

[0046] The urethane (meth)acrylate resin represents a (meth)acrylate resin containing a urethane bond. Examples of the urethane (meth)acrylate resin include those obtained by a urethanization reaction of a polyisocyanate compound, a polyol compound, and a (meth)acrylate resin containing a hydroxyl group; those obtained by a urethanization reaction of a polyol compound and an isocyanate compound containing a (meth)acryloyl group; those obtained by a urethanization reaction of a (meth)acrylate resin containing a hydroxyl group and a polyisocyanate compound; and the like.

[0047] Among the urethane (meth)acrylate resins, a urethane (meth)acrylate resin containing a polyether backbone and a urethane (meth)acrylate resin containing a carbonate backbone are preferred; a urethane (meth)acrylate resin containing a polyether backbone is more preferred. The urethane (meth)acrylate resin containing a polyether backbone is a urethane (meth)acrylate resin containing two or more ether backbones. For example, as the polyol compound, it can be produced using a polyether polyol compound such as polyoxyethylene glycol, polyoxypropylene glycol, polytetramethylene glycol, or polyoxymethylene glycol.

[0048] The epoxy (meth)acrylate resin represents a (meth)acrylate resin containing a structure obtained by reacting an epoxy resin containing one or two or more epoxy groups in one molecule with (meth)acrylic acid. Examples of the epoxy resin include bisphenol A type epoxy resin, hydrogenated bisphenol A type epoxy resin, novolac type epoxy resin, hydrogenated novolac type epoxy resin, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, glycerin diglycidyl ether, and the like.

[0049] Among epoxy (meth)acrylate resins, an epoxy (meth)acrylate resin containing a bisphenol A skeleton is preferable. The epoxy (meth)acrylate resin containing a bisphenol A skeleton can be produced, for example, by reacting a bisphenol A type epoxy resin with (meth)acrylic acid.

[0050] When a photosensitive resin composition for a core containing a (meth)acrylate resin (A) containing at least one selected from the group consisting of urethane (meth)acrylate resin and epoxy (meth)acrylate resin is used in combination with a photosensitive resin composition for a clad described later, effects such as suppression of displacement of the core portion during removal of the needle-shaped portion and reduction of transmission loss of the optical waveguide can be obtained. More preferably, the adhesion between the clad portion and the support and the warp of the optical waveguide can be improved.

[0051] The total amount of the urethane (meth)acrylate resin and the epoxy (meth)acrylate resin is preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 25% by mass or more, and preferably 100% by mass or less, more preferably 90% by mass or less, still more preferably 80% by mass or less, based on 100% by mass of the (meth)acrylate resin (A). When the total amount of the urethane (meth)acrylate resin and the epoxy (meth)acrylate resin is within the above range, effects such as suppression of displacement of the core portion during removal of the needle-shaped portion and reduction of transmission loss of the optical waveguide can be remarkably obtained. More preferably, the warp of the optical waveguide can be effectively improved.

[0052] Further, the (meth)acrylate resin (A) may contain any (meth)acrylate resin in combination with a urethane (meth)acrylate resin and an epoxy (meth)acrylate resin. Examples of the any (meth)acrylate resin include an aliphatic (meth)acrylate resin (a (meth)acrylate resin containing an aliphatic skeleton), a carbonate (meth)acrylate resin (a (meth)acrylate resin containing a carbonate skeleton), an ether (meth)acrylate resin (a (meth)acrylic resin containing an ether bond in addition to the ether bond contained in the (meth)acryloyloxy group), a fluorine-based (meth)acrylate resin (a (meth)acrylic resin containing a fluorine atom), a silicon-based (meth)acrylate resin (a (meth)acrylic resin containing a silicon atom), and the like. The classification of the (meth)acrylate resin exemplified here is not exclusive, and a certain (meth)acrylate resin may belong to a plurality of classifications.

[0053] (A) The (meth)acrylate resin may be a commercially available product. Examples of the commercially available (meth)acrylate resin include "A-DOG" manufactured by Shin-Nakamura Chemical Co., Ltd.; "EA-0200" manufactured by Osaka Gas Chemical Co., Ltd.; "UN-6306", "PMH-401H", "UN-9200A", "M-3N" manufactured by Negami Industries Co., Ltd.; "EBECRYL 3708", "EBECRYL 3701", "EBECRYL 3605" manufactured by Daicel Ornex Co., Ltd.; "Biscoat 3F", "KBM-503" manufactured by Osaka Organic Chemical Industry Co., Ltd.; and the like. The (meth)acrylate resin may be used alone or in combination of two or more.

[0054] (A) The number N of (meth)acryloyl groups contained in one molecule of the (meth)acrylate resin may be 1 or may be 2 or more. The range of the number N of (meth)acryloyl groups contained in one molecule of the (A) (meth)acrylate resin is preferably 1 to 3, more preferably 1 to 2. Among them, it is preferable to use in combination a monofunctional (meth)acrylate resin containing one (meth)acryloyl group in one molecule and a bifunctional (meth)acrylate resin containing two (meth)acryloyl groups in one molecule. The amount of the monofunctional (meth)acrylate resin with respect to 100% by mass of the total amount of the (A) (meth)acrylate resin is preferably 1% by mass or more, more preferably 5% by mass or more, still more preferably 8% by mass or more, and preferably 30% by mass or less, more preferably 20% by mass or less, still more preferably 15% by mass or less.

[0055] (A) The (meth)acrylate resin may include a (meth)acrylate resin containing an arbitrary crosslinkable group in addition to the (meth)acryloyl group. The (meth)acrylate resin containing an arbitrary crosslinkable group can react not only with the (meth)acryloyl group but also with an arbitrary crosslinkable group in the fourth step to generate a bond and cure the photosensitive resin composition for the core. Examples of the arbitrary crosslinkable group include, but are not limited to, an epoxy group, a phenolic hydroxyl group (a hydroxyl group bonded to an aromatic ring), etc. The arbitrary crosslinkable group can be utilized for adjusting the refractive index. For example, according to a (meth)acrylate resin containing an epoxy group, the refractive index of the cured product of the photosensitive resin composition for the core can be increased.

[0056] (A) The weight average molecular weight Mw of the (meth)acrylate resin preferably ranges from 86 or more, more preferably 200 or more, still more preferably 300 or more, and preferably 30,000 or less, more preferably 20,000 or less, still more preferably 15,000 or less. The weight average molecular weight can be measured as a value in terms of polystyrene by gel permeation chromatography (GPC). When the weight average molecular weight Mw of the (meth)acrylate resin is within the above range, effects such as suppression of displacement of the core part during removal of the needle-like part and reduction of transmission loss of the optical waveguide can be remarkably obtained. More preferably, the warp of the optical waveguide can be effectively improved.

[0057] (A) The (meth)acrylic equivalent of the (meth)acrylate resin is preferably 86 or more, more preferably 100 or more, still more preferably 150 or more, and preferably 20,000 or less, more preferably 15,000 or less, still more preferably 10,000 or less. The (meth)acrylic equivalent represents the molecular weight of the (meth)acrylate resin per equivalent of the (meth)acryloyl group. When the (meth)acrylic equivalent of the (meth)acrylate resin is within the above range, effects such as suppression of displacement of the core part during removal of the needle-like part and reduction of transmission loss of the optical waveguide can be remarkably obtained. More preferably, the warp of the optical waveguide can be effectively improved.

[0058] (A) The (meth)acrylate resin is preferably selected and used such that the parameter D represented by the following formula (2) core falls within a specific range.

[0059] [Number]

[0060] In formula (2), W core represents the content rate (mass%) of each (meth)acrylate resin contained in the photosensitive resin composition for the core, based on 100 mass% of the non-volatile components of the photosensitive resin composition for the core; C corerepresents the value Mw / N obtained by dividing the weight-average molecular weight Mw of each (meth)acrylate resin contained in the photosensitive resin composition for the core by the number N of (meth)acryloyl groups possessed by one molecule of the (meth)acrylate resin. The above value C core corresponds to the molecular weight of the (meth)acrylate resin per equivalent of (meth)acryloyl group, and is hereinafter referred to as the "(meth)acrylic equivalent" C core in some cases. Therefore, parameter D core is the (meth)acrylic equivalent C core of the (meth)acrylate resin and the content W core of the (meth)acrylate resin, and represents the total value obtained by summing over all the (meth)acrylate resins contained in the photosensitive resin composition for the core.

[0061] The range of parameter D core in the photosensitive resin composition for the core is preferably 100 or more, more preferably 200 or more, still more preferably 300 or more, and preferably 6,000 or less, more preferably 5,000 or less, still more preferably 4,000 or less. When parameter D core is within the above range, effects such as suppression of displacement of the core portion during removal of the needle-shaped portion and reduction of transmission loss of the optical waveguide can be remarkably obtained. More preferably, the warp of the optical waveguide can be effectively improved.

[0062] (A) The amount of the (meth)acrylate resin is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, particularly preferably 95% by mass or more, based on 100% by mass of the non-volatile components of the photosensitive resin composition for the core. The upper limit is 100% by mass or less, and may be 99.9% by mass or less. When the photosensitive resin composition for the core contains the (meth)acrylate resin in such an amount within the above range, effects such as suppression of displacement of the core portion during removal of the needle-shaped portion and reduction of transmission loss of the optical waveguide can be remarkably obtained. More preferably, the warp of the optical waveguide can be effectively improved.

[0063] With respect to 100% by mass of the total amount of the photosensitive resin composition for the core, the amount range of the (meth)acrylate resin (A) is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably 95% by mass or more. The upper limit is 100% by mass or less, and may be 99.9% by mass or less. When the photosensitive resin composition for the core contains the (meth)acrylate resin (A) in such an amount range, effects such as suppression of displacement of the core portion during removal of the needle-shaped portion and reduction of transmission loss of the optical waveguide can be remarkably obtained. More preferably, the warp of the optical waveguide can be effectively improved.

[0064] The uncured photosensitive resin composition for the core may further contain an arbitrary component in combination with the (meth)acrylate resin (A). For example, the uncured photosensitive resin composition for the core may contain a (B) photopolymerization initiator as an arbitrary component. The (B) photopolymerization initiator as this (B) component does not include those corresponding to the (A) component. According to the (B) photopolymerization initiator, the curing of the photosensitive resin composition for the core can proceed efficiently. The (B) photopolymerization initiator may be used alone or in combination of two or more.

[0065] (B) As the photoinitiator, a compound capable of generating radicals upon receiving actinic rays can be used.Examples of this (B) photoinitiator include oxime ester photoinitiators such as 2-(benzoyloxyimino)-1-[4-(phenylthio)phenyl]octan-1-one (OXE01), [1-[9-ethyl-6-(2-methylbenzoyl)carbazol-3-yl]ethylideneamino]acetate (OXE02), ethanone, 1-[9-ethyl-6-(2-methylbenzoyl)-9H-carbazol-3-yl]-, 1-(O-acetoxyoxime), etc.; aminoketone photoinitiators such as 2-methyl-1-phenyl-2-morpholinopropan-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 2-methyl-1-(4-hexylphenyl)-2-morpholinopropan-1-one, 2-ethyl-2-(dimethylamino)-1-(4-morpholinophenyl)butan-1-one, 2-benzyl-2-(dimethylamino)-1-(4-morpholinophenyl)butan-1-one, 2-(dimethylamino)-2-(4-methylphenylmethyl)-1-(4-morpholinophenyl)butan-1-one, 2-methyl-1-(9,9-dibutylfluoren-2-yl)-2-morpholinopropan-1-one, etc.; acylphosphine photoinitiators such as bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, (2,4,6-trimethylbenzoyl)diphenylphosphine oxide, polyoxyethylene glycerin ether tris[phenyl(2,4,6-trimethylbenzoyl)phosphinate] (Polymeric TPO-L), etc.; α-hydroxyketone photoinitiators such as 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropanone, 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methylpropanone, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)benzyl]phenyl}-2-methylpropan-1-one, etc.; benzoin photoinitiators such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, etc.; benzyl ketal photoinitiators such as 2,2-dimethoxy-2-phenylacetophenone, etc.

[0066] (B) The photoinitiator may be a commercially available product. Examples of commercially available (B) photoinitiators include "Omnirad 907", "Omnirad 369", "Omnirad 379", "Omnirad 379EG", "Omnirad 819", "Omnirad TPO" manufactured by IGM; "Irgacure TPO", "Irgacure OXE-01", "Irgacure OXE-02" manufactured by BASF; "N-1919" manufactured by ADEKA, etc.

[0067] (B) The amount range of the photoinitiator is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, still more preferably 0.1% by mass or more, and preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 1% by mass or less, based on 100% by mass of the total amount of the photosensitive resin composition for the core.

[0068] (B) The amount range of the photoinitiator is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, still more preferably 0.1% by mass or more, and preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 1% by mass or less, based on 100% by mass of the non-volatile components of the photosensitive resin composition for the core.

[0069] (B) The amount range of the photoinitiator is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, still more preferably 0.1% by mass or more, and preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 1% by mass or less, based on 100% by mass of the (meth)acrylate resin (A).

[0070] The photosensitive resin composition for the core may contain, as an optional component, (C) an optional curable resin. The (C) optional curable resin as the component (C) does not include those corresponding to the components (A) to (B). The photosensitive resin composition for the core containing the (C) optional curable resin can be cured by reacting not only the (A) (meth)acrylate resin but also the (C) optional curable resin in the fourth step to generate a bond. The (C) optional curable resin may be used alone or in combination of two or more.

[0071] Examples of the (C) optional curable resin include radical-reactive resins containing a radical-reactive unsaturated group. Examples of the radical-reactive unsaturated group include unsaturated hydrocarbon groups such as vinyl group, allyl group, 1-propenyl group, 3-cyclohexenyl group, 3-cyclopentenyl group, 2-vinylphenyl group, 3-vinylphenyl group, 4-vinylphenyl group; α,β-unsaturated carbonyl groups such as maleimide group (2,5-dihydro-2,5-dioxo-1H-pyrrol-1-yl group); and the like. Examples of the radical-reactive resin include maleimide resin, styryl resin, and allyl resin.

[0072] Examples of the (C) optional curable resin include resins containing an arbitrary crosslinkable group other than the radical-reactive unsaturated group. Examples of the arbitrary crosslinkable group include epoxy group, phenolic hydroxyl group, benzoxazine ring, active ester group, cyanate group, carbodiimide group, acid anhydride group, amino group, and the like. Examples of the resin containing an arbitrary crosslinkable group include epoxy resin, phenolic resin, benzoxazine resin, active ester resin, cyanate ester resin, carbodiimide resin, acid anhydride resin, amine resin, and the like.

[0073] Further, as (C) an arbitrary curable resin, a resin containing a combination of a radical-reactive unsaturated group and an arbitrary crosslinkable group in one molecule may be used. For example, a resin containing a combination of an allyl group and a phenolic hydroxyl group may be used. Specific examples of such a resin include "BPA-CA" (2,2-bis(3-allyl-4-hydroxyphenyl)propane) manufactured by Konishi Chemical Industry Co., Ltd.

[0074] (C) The range of the amount of the arbitrary curable resin is preferably 30% by mass or less, more preferably 20% by mass or less, still more preferably 10% by mass or less, based on 100% by mass of the total amount of the photosensitive resin composition for the core. The lower limit may be 0% by mass, may be more than 0% by mass, and may be, for example, 1% by mass or more, 3% by mass or more, or 5% by mass or more.

[0075] (C) The range of the amount of the arbitrary curable resin is preferably 30% by mass or less, more preferably 20% by mass or less, still more preferably 10% by mass or less, based on 100% by mass of the non-volatile components of the photosensitive resin composition for the core. The lower limit may be 0% by mass, may be more than 0% by mass, and may be, for example, 1% by mass or more, 3% by mass or more, or 5% by mass or more.

[0076] (C) The range of the amount of the arbitrary curable resin is preferably 40% by mass or less, more preferably 30% by mass or less, still more preferably 20% by mass or less, based on 100% by mass of the (meth)acrylate resin. The lower limit may be 0% by mass, may be more than 0% by mass, and may be, for example, 1% by mass or more, 5% by mass or more, or 10% by mass or more.

[0077] The photosensitive resin composition for the core may contain, as an optional component, (D) an optional additive. The (D) optional additive as the component (D) does not include those corresponding to the above-mentioned components (A) to (C). Examples of the (D) optional additive include an ultraviolet absorber, a silane coupling agent, a plasticizer, a flame retardant, an antistatic agent, an antioxidant, an antibacterial agent, an antifoaming agent, a leveling agent, a thickening agent, an adhesion promoter, a thixotropy-imparting agent, a release agent, a surface treatment agent, a dispersant, a surface modifier, a stabilizer, a thermoplastic resin, and the like. The (D) optional additive may be used alone or in combination of two or more kinds.

[0078] (D) The optional additive may contain inorganic particles. For example, when containing metal oxide nanoparticles, the refractive index of the core part can be increased. However, from the viewpoint of effectively reducing the transmission loss of the optical waveguide, the amount of the inorganic particles is preferably small. Specifically, the range of the amount of the inorganic particles is preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 1% by mass or less, and particularly preferably 0% by mass, based on 100% by mass of the non-volatile components of the photosensitive resin composition for the core. Therefore, it is preferable that the resin composition does not contain inorganic particles.

[0079] The photosensitive resin composition for the core may contain (E) a solvent as an optional volatile component in combination with non-volatile components such as components (A) to (D). Usually, an organic solvent is used as the (E) solvent. Examples of the organic solvent include ketone solvents such as ethyl methyl ketone (MEK) and cyclohexanone; aromatic hydrocarbon solvents such as toluene, xylene, and tetramethylbenzene; glycol ether solvents such as diethylene glycol monoethyl ether acetate, ethyl diglycol acetate (EDGAc), methyl cellosolve, butyl cellosolve, methyl carbitol, butyl carbitol, propylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol diethyl ether, and triethylene glycol monoethyl ether; ester solvents such as ethyl acetate, butyl acetate, butyl cellosolve acetate, carbitol acetate, and ethyl diglycol acetate; aliphatic hydrocarbon solvents such as octane and decane; petroleum solvents such as petroleum ether, petroleum naphtha, hydrogenated petroleum naphtha, and solvent naphtha; and the like. The (E) solvent may be used alone or in combination of two or more.

[0080] (E) The range of the amount of the solvent is preferably 30% by mass or less, more preferably 20% by mass or less, still more preferably 10% by mass or less, still more preferably 5% by mass or less, and may be 0% by mass, based on 100% by mass of the photosensitive resin composition for the core.

[0081] The photosensitive resin composition for the core exhibits a liquid or gel-like property under the temperature conditions (usually room temperature of about 23°C) in the second step. At this time, the viscosity range of the photosensitive resin composition for the core is preferably 1 Pa·s or more, more preferably 5 Pa·s or more, still more preferably 10 Pa·s or more, preferably 150 Pa·s or less, more preferably 120 Pa·s or less, still more preferably 100 Pa·s or less. When the photosensitive resin composition for the core has a viscosity within the above range, the effects of the present invention can be remarkably obtained. The viscosity can be measured by the method described in the examples below.

[0082] The photosensitive resin composition for the core preferably has a higher viscosity than the photosensitive resin composition for the clad under the temperature conditions (usually room temperature of about 23 ° C) in the second step. At this time, the difference in viscosity between the photosensitive resin composition for the core and the photosensitive resin composition for the clad is preferably 1 Pa·s or more, more preferably 10 Pa·s or more, still more preferably 40 Pa·s or more, and preferably 100 Pa·s or less, more preferably 80 Pa·s or less, still more preferably 60 Pa·s or less. When the difference in viscosity between the photosensitive resin composition for the core and the photosensitive resin composition for the clad has a viscosity within the above range, the effects of the present invention can be remarkably obtained.

[0083] By curing the photosensitive resin composition for the core, a cured product can be obtained. The core portion of the optical waveguide is formed by this cured product. When the photosensitive resin composition for the core is cured, heat is usually applied, so (E) volatile components such as a solvent are volatilized and removed. Therefore, the cured product of the photosensitive resin composition for the core may contain non-volatile components of the photosensitive resin composition for the core and reaction products thereof.

[0084] The refractive index n of the cured product of the photosensitive resin composition for the core core is in the range of preferably 1.3 or more, more preferably 1.4 or more, still more preferably 1.5 or more, and preferably 2 or less, more preferably 1.9 or less, still more preferably 1.8 or less at a measurement wavelength of 1310 nm. The refractive index n core can be measured by the method described in the examples below. Also, when the sample is an uncured photosensitive resin composition for the core, it is exposed at an illuminance of 3,000 mW / cm 2 and further heated at 150 ° C for 30 minutes to obtain a cured product, and the refractive index n core of the cured product can be measured.

[0085] The refractive index n of the cured product of the photosensitive resin composition for the core core is preferably within a specific range of the numerical aperture NA represented by the following formula (3) with respect to the refractive index n clad of the cured product of the photosensitive resin composition for the clad. In formula (3), n corerepresents the refractive index of the cured product of the photosensitive resin composition for the core, and n clad represents the refractive index of the cured product of the photosensitive resin composition for the cladding. The refractive index n core and the refractive index n clad The measurement wavelength is the wavelength of the light transmitted through the optical waveguide, for example, 1310 nm. The numerical aperture NA is specifically preferably greater than 0.03, more preferably greater than 0.04, still more preferably greater than 0.05, still more preferably greater than 0.06, and also preferably less than 0.80, more preferably 0.75 or less, still more preferably 0.70 or less, still more preferably 0.30 or less. When the photosensitive resin composition for the core and the photosensitive resin composition for the cladding are combined so as to satisfy the numerical aperture NA within such a range, the transmission loss of the optical waveguide can be effectively reduced.

[0086]

Number

[0087] The photosensitive resin composition for the core can be produced by mixing each component to be included in the photosensitive resin composition for the core. Therefore, the photosensitive resin composition for the core can be produced by mixing component (A) and, if necessary, components (B) to (E). When mixing, if necessary, kneading may be performed by a kneading device such as a three-roll mill, ball mill, bead mill, sand mill, etc., or stirring may be performed by a stirring device such as a super mixer, planetary mixer, etc. There is no limitation on the order of mixing of each component. Also, cooling or heating may be performed during the process of mixing each component.

[0088] <Photosensitive resin composition for cladding> The photosensitive resin composition for the cladding used in the above-described production method contains (a) (meth)acrylate resin as component (a). The photosensitive resin composition for the cladding containing (a) (meth)acrylate resin can be cured by the reaction of (meth)acryloyl groups in the fourth step. (a) (meth)acrylate resin may be used alone or in combination of two or more.

[0089] (a) The (meth)acrylate resin contains one or more (meth)acrylate resins selected from the group consisting of urethane (meth)acrylate resins and epoxy (meth)acrylate resins.

[0090] As the urethane (meth)acrylate resin contained in the photosensitive resin composition for cladding, those within the same range as the urethane (meth)acrylate resin that can be contained in the photosensitive resin composition for core may be used. At this time, the urethane (meth)acrylate resin contained in the photosensitive resin composition for cladding and the urethane (meth)acrylate resin contained in the photosensitive resin composition for core may be the same or different. As the urethane (meth)acrylate resin contained in the photosensitive resin composition for cladding, a urethane (meth)acrylate resin containing a polyether backbone and a urethane (meth)acrylate resin containing a carbonate backbone are preferable; a urethane (meth)acrylate resin containing a polyether backbone is more preferable.

[0091] As the epoxy (meth)acrylate resin contained in the photosensitive resin composition for cladding, those within the same range as the epoxy (meth)acrylate resin that can be contained in the photosensitive resin composition for core may be used. At this time, the epoxy (meth)acrylate resin contained in the photosensitive resin composition for cladding and the epoxy (meth)acrylate resin contained in the photosensitive resin composition for core may be the same or different. As the epoxy (meth)acrylate resin contained in the photosensitive resin composition for cladding, an epoxy (meth)acrylate resin containing a bisphenol A backbone is preferable.

[0092] When using in combination the photosensitive resin composition for cladding containing the (a)(meth)acrylate resin containing one or more selected from the group consisting of the urethane (meth)acrylate resin and the epoxy (meth)acrylate resin as described above with the photosensitive resin composition for core, effects such as suppression of the displacement of the core part during removal of the needle-like part and reduction of the transmission loss of the optical waveguide can be obtained. More preferably, the adhesion between the cladding part and the support and the warp of the optical waveguide can be improved.

[0093] The total amount range of the urethane (meth)acrylate resin and the epoxy (meth)acrylate resin contained in the photosensitive resin composition for the clad is preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 30% by mass or more, and preferably 90% by mass or less, more preferably 80% by mass or less, still more preferably 70% by mass or less, based on 100% by mass of the (meth)acrylate resin (a). When the total amount of the urethane (meth)acrylate resin and the epoxy (meth)acrylate resin is within the above range, effects such as suppression of displacement of the core part during removal of the needle-shaped part and reduction of transmission loss of the optical waveguide can be remarkably obtained. More preferably, the adhesion between the clad part and the support and the warp of the optical waveguide can be effectively improved.

[0094] In addition, the (meth)acrylate resin (a) may further contain any arbitrary (meth)acrylate resin in combination with the urethane (meth)acrylate resin and the epoxy (meth)acrylate resin. As the arbitrary (meth)acrylate resin, those in the same range as any arbitrary (meth)acrylate resin that the photosensitive resin composition for the core may contain may be used. At this time, the arbitrary (meth)acrylate resin contained in the photosensitive resin composition for the clad and the arbitrary (meth)acrylate resin contained in the photosensitive resin composition for the core may be the same or different. The arbitrary (meth)acrylate resin may be used alone or in combination of two or more.

[0095] The number N of (meth)acryloyl groups contained in one molecule of the (meth)acrylate resin (a) may be 1 or 2 or more. The range of the number N of (meth)acryloyl groups contained in one molecule of the (meth)acrylate resin (a) is preferably 1 to 3, more preferably 1 to 2.

[0096] (a) The (meth)acrylate resin may include a (meth)acrylate resin containing any crosslinkable group other than the (meth)acryloyl group. Examples of any crosslinkable group include the same examples as any crosslinkable group that the (A) (meth)acrylate resin contained in the photosensitive resin composition for the core may contain.

[0097] (a) The range of the weight average molecular weight Mw of the (meth)acrylate resin is preferably 86 or more, more preferably 200 or more, still more preferably 300 or more, and preferably 40,000 or less, more preferably 30,000 or less, still more preferably 20,000 or less. When the weight average molecular weight Mw of the (a) (meth)acrylate resin is within the above range, effects such as suppression of the displacement of the core part during the removal of the needle-shaped part and reduction of the transmission loss of the optical waveguide can be remarkably obtained. More preferably, the adhesion between the clad part and the support and the warp of the optical waveguide can be effectively improved.

[0098] (a) The (meth)acrylic equivalent of the (meth)acrylate resin is preferably 86 or more, more preferably 100 or more, still more preferably 150 or more, and preferably 30,000 or less, more preferably 20,000 or less, still more preferably 10,000 or less. When the (meth)acrylic equivalent of the (a) (meth)acrylate resin is within the above range, effects such as suppression of the displacement of the core part during the removal of the needle-shaped part and reduction of the transmission loss of the optical waveguide can be remarkably obtained. More preferably, the adhesion between the clad part and the support and the warp of the optical waveguide can be effectively improved.

[0099] (a) The (meth)acrylate resin preferably selects and uses the type and its amount so that the parameter D represented by the following formula (1) clad falls within a specific range.

[0100]

Number

[0101] In formula (1), W cladrepresents the content rate (mass %) of each (meth)acrylate resin contained in the photosensitive resin composition for cladding, based on 100 mass % of the non-volatile components of the photosensitive resin composition for cladding; C clad represents the value Mw / N obtained by dividing the weight average molecular weight Mw of each (meth)acrylate resin contained in the photosensitive resin composition for cladding by the number N of (meth)acryloyl groups that one molecule of the (meth)acrylate resin has. The above value C clad corresponds to the molecular weight of the (meth)acrylate resin per equivalent of (meth)acryloyl group. Therefore, hereinafter, it is sometimes referred to as the “(meth)acrylic equivalent” C clad Thus, the parameter D clad is the (meth)acrylic equivalent C clad of the (meth)acrylate resin and the content rate W clad of the (meth)acrylate resin, and represents the value obtained by summing up all the (meth)acrylate resins contained in the photosensitive resin composition for cladding.

[0102] The parameter D clad in the photosensitive resin composition for cladding preferably has a range of 400 or more, more preferably 500 or more, still more preferably 600 or more, and preferably 5,000 or less, more preferably 4,950 or less, still more preferably 4,900 or less. When the parameter D clad is within the above range, effects such as suppression of the displacement of the core part during the removal of the needle-like part and reduction of the transmission loss of the optical waveguide can be remarkably obtained. More preferably, the adhesion between the cladding part and the support and the warp of the optical waveguide can be effectively improved.

[0103] With respect to 100% by mass of the non-volatile components of the photosensitive resin composition for a clad, the amount of the (meth)acrylate resin (a) is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably 95% by mass or more. The upper limit is 100% by mass or less, and may be 99.9% by mass or less. When the photosensitive resin composition for a clad contains the (meth)acrylate resin (a) in such an amount range, effects such as suppression of the core misalignment during removal of the needle-like portion and reduction of the transmission loss of the optical waveguide can be remarkably obtained. More preferably, the adhesion between the clad portion and the support and the warp of the optical waveguide can be effectively improved.

[0104] With respect to 100% by mass of the total amount of the photosensitive resin composition for a clad, the amount range of the (meth)acrylate resin (a) is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably 95% by mass or more. The upper limit is 100% by mass or less, and may be 99.9% by mass or less. When the photosensitive resin composition for a clad contains the (meth)acrylate resin (a) in such an amount range, effects such as suppression of the core misalignment during removal of the needle-like portion and reduction of the transmission loss of the optical waveguide can be remarkably obtained. More preferably, the adhesion between the clad portion and the support and the warp of the optical waveguide can be effectively improved.

[0105] The uncured photosensitive resin composition for a clad may further contain an arbitrary component in combination with the (meth)acrylate resin (a). For example, the uncured photosensitive resin composition for a clad may contain a (b) photopolymerization initiator as an arbitrary component. The (b) photopolymerization initiator as this (b) component does not include those corresponding to the (a) component. The (b) photopolymerization initiator may be used alone or in combination of two or more. As the (b) photopolymerization initiator, those in the same range as the (B) photopolymerization initiator that the photosensitive resin composition for a core may contain may be used.

[0106] (b) The range of the amount of the photopolymerization initiator is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, still more preferably 0.1% by mass or more, and preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 1% by mass or less, based on 100% by mass of the total amount of the photosensitive resin composition for the clad.

[0107] (b) The range of the amount of the photopolymerization initiator is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, still more preferably 0.1% by mass or more, and preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 1% by mass or less, based on 100% by mass of the non-volatile components of the photosensitive resin composition for the clad.

[0108] (b) The range of the amount of the photopolymerization initiator is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, still more preferably 0.1% by mass or more, and preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 1% by mass or less, based on 100% by mass of the (meth)acrylate resin (a).

[0109] The photosensitive resin composition for the clad may contain (c) an arbitrary curable resin as an optional component. The (c) arbitrary curable resin as this (c) component does not include those corresponding to the (a) to (b) components. The (c) arbitrary curable resin may be used alone or in combination of two or more. As the (c) arbitrary curable resin, those in the same range as the (C) arbitrary curable resin that the photosensitive resin composition for the core may contain may be used.

[0110] (c) The range of the amount of the arbitrary curable resin is preferably 30% by mass or less, more preferably 20% by mass or less, still more preferably 10% by mass or less, based on 100% by mass of the total amount of the photosensitive resin composition for the clad. The lower limit may be 0% by mass, may be more than 0% by mass, for example, may be 1% by mass or more, 3% by mass or more, or 5% by mass or more.

[0111] (c) The range of the amount of any curable resin is preferably 30% by mass or less, more preferably 20% by mass or less, still more preferably 10% by mass or less, based on 100% by mass of the non-volatile components of the photosensitive resin composition for cladding. The lower limit may be 0% by mass, may be more than 0% by mass, and may be, for example, 1% by mass or more, 3% by mass or more, or 5% by mass or more.

[0112] (c) The range of the amount of any curable resin is preferably 40% by mass or less, more preferably 30% by mass or less, still more preferably 20% by mass or less, based on 100% by mass of the (meth)acrylate resin. The lower limit may be 0% by mass, may be more than 0% by mass, and may be, for example, 1% by mass or more, 5% by mass or more, or 10% by mass or more.

[0113] The photosensitive resin composition for cladding may contain, as an optional component, (d) any additive. The (d) any additive as the component (d) does not include those corresponding to the above components (a) to (c). The (d) any additive may be used alone or in combination of two or more. As the (d) any additive, those in the same range as the (D) any additive that the photosensitive resin composition for core may contain may be used.

[0114] The photosensitive resin composition for cladding may contain, in combination with the non-volatile components such as the components (a) to (d), (e) a solvent as an optional volatile component. The (e) solvent may be used alone or in combination of two or more. As the (e) solvent, those in the same range as the (E) solvent that the photosensitive resin composition for core may contain may be used.

[0115] (e) The range of the amount of the solvent is preferably 30% by mass or less, more preferably 20% by mass or less, still more preferably 10% by mass or less, still more preferably 5% by mass or less, and may be 0% by mass, based on 100% by mass of the photosensitive resin composition for cladding.

[0116] The photosensitive resin composition for a clad exhibits a liquid or gel-like property under the temperature conditions (usually room temperature of about 23°C) in the second step. At this time, the viscosity range of the photosensitive resin composition for a clad is preferably 0.1 Pa·s or more, more preferably 1 Pa·s or more, still more preferably 2 Pa·s or more, and preferably 100 Pa·s or less, more preferably 80 Pa·s or less, still more preferably 50 Pa·s or less. When the photosensitive resin composition for a clad has a viscosity within the above range, effects such as suppression of displacement of the core part during removal of the needle-like part and reduction of transmission loss of the optical waveguide can be remarkably obtained. More preferably, the adhesion between the clad part and the support and the warpage of the optical waveguide can be effectively improved. Generally, the uncured core part after formation may sink due to gravity. At this time, the higher the viscosity of the photosensitive resin composition for a clad, the more effectively the sinking of the uncured core part can be suppressed. Therefore, for example, when it is desired to provide a core part at a high position within the clad part, from the viewpoint of suppressing the sinking of the core part, it is preferable that the viscosity of the photosensitive resin composition for a clad is high. Also, for example, when it is desired to provide a core part at a low position within the clad part, since the sinking of the core part can be tolerated, the viscosity of the photosensitive resin composition for a clad may be high or low. Furthermore, usually, the lower the viscosity of the photosensitive resin composition for a clad, the smoother the formation of the uncured core part within the uncured clad part can be performed. Therefore, it is desirable to set the specific viscosity of the photosensitive resin composition for a clad according to the above circumstances.

[0117] By curing the photosensitive resin composition for a clad, a cured product can be obtained. The cured product forms the clad part of the optical waveguide. When the photosensitive resin composition for a clad is cured, heat is usually applied, so (e) volatile components such as a solvent volatilize and are removed. Therefore, the cured product of the photosensitive resin composition for a clad may contain the non-volatile components of the photosensitive resin composition for a clad and their reaction products.

[0118] Refractive index n of the cured product of the photosensitive resin composition for a clad cladThe range is preferably 1.35 or more, more preferably 1.40 or more, still more preferably 1.45 or more, and preferably 1.8 or less, more preferably 1.7 or less, still more preferably 1.6 or less at a measurement wavelength of 1310 nm. The refractive index n clad can be measured by the method described in the examples below. Also, when the sample is an uncured photosensitive resin composition for cladding, it is exposed at an illuminance of 3,000 mW / cm 2 and further heated at 150 °C for 30 minutes to obtain a cured product, and the refractive index n clad of the cured product can be measured.

[0119] The photosensitive resin composition for cladding can be produced by mixing each component to be included in the photosensitive resin composition for cladding. Therefore, the photosensitive resin composition for cladding can be produced by mixing components (a) to (e) as necessary. When mixing, kneading by a kneading device or stirring by a stirring device may be performed as necessary. There is no limitation on the order of mixing of each component. Also, cooling or heating may be performed during the process of mixing each component.

[0120] <Optical waveguide> According to the manufacturing method according to this embodiment, an optical waveguide including a core portion and a cladding portion can be manufactured. The core portion includes a cured product of the photosensitive resin composition for core, and usually includes only the cured product of the photosensitive resin composition for core. Also, the cladding portion includes a cured product of the photosensitive resin composition for cladding, and usually includes only the photosensitive resin composition for cladding. Since the core portion has a higher refractive index than the cladding portion, an optical signal can be transmitted through the core portion.

[0121] In the optical waveguide manufactured by the manufacturing method according to this embodiment, the transmission loss can be reduced. In one example, the transmission loss per unit distance of the optical waveguide is preferably 2.0 dB / cm or less, more preferably 1.0 dB / cm or less, still more preferably 0.5 dB / cm or less, and particularly preferably 0.4 dB / cm or less. The lower limit is ideally 0.0 dB / cm, but usually 0.1 dB / cm or more. The transmission loss of the optical waveguide can be measured by the method described in the examples below.

[0122] In the optical waveguide manufactured by the manufacturing method according to this embodiment, preferably, the adhesion between the clad portion and the base material can be increased. This advantage is particularly useful when applying the optical waveguide to an optoelectronic integrated circuit. Specifically, it is as follows.

[0123] When the clad portion and the core portion are removed from the base material and used after manufacturing the optical waveguide, the adhesion between the clad portion and the base material may be low. However, when manufacturing an optoelectronic integrated circuit using the mosquito method, it is required to utilize the technology of circuit boards such as printed circuit boards currently used in electric circuits. Therefore, it is desirable that the formation of the optical waveguide by the mosquito method can be carried out on the circuit board. Specifically, it is desirable to use a circuit board as the base material and provide the clad portion and the core portion on the circuit board. However, when an uncured clad portion is formed on the circuit board and cured, conventionally, the clad portion may peel off from the circuit board due to curing stress.

[0124] On the other hand, according to the manufacturing method according to the above-described embodiment, it is possible to improve the adhesion between the clad portion and the base material, which can contribute to the realization of an optoelectronic integrated circuit. In one example, the optical waveguide obtained by the manufacturing method according to this embodiment can achieve a high adhesion that can suppress peeling between the clad portion and the base material even when the optical waveguide is bent by 5 mm as in the examples described later to apply stress to the core portion and the clad portion.

[0125] Generally, an insulating layer, a sealing layer, or a solder resist layer is formed on the outermost layer of the circuit board. Usually, these layers are cured product layers formed by curing a resin composition. In order to realize an optoelectronic integrated circuit with excellent durability and stability, it is desirable that the clad portion be stably held on the circuit board. Therefore, in the examples described later, the evaluation of adhesion is performed using a base material provided with a solder resist layer as the cured product layer.

[0126] However, even when the optical waveguide is applied to an optoelectronic integrated circuit, members other than the circuit board may be used as the base material. For example, a glass substrate, a metal substrate, a ceramic substrate, a wafer, etc. may be used as the base material. Further, as the wafer, for example, a semiconductor wafer such as a silicon wafer, a gallium arsenide (GaAs) wafer, an indium phosphide (InP) wafer, a gallium phosphide (GaP) wafer, a gallium nitride (GaN) wafer, a gallium telluride (GaTe) wafer, a zinc selenide (ZnSe) wafer, a silicon carbide (SiC) wafer, etc. may be used, or a dummy wafer may be used. As the dummy wafer, for example, a plate-like member including a mold resin and electronic components embedded in the mold resin can be used.

[0127] The optical waveguide manufactured by the manufacturing method according to the present embodiment can preferably reduce warpage. For example, when a circuit board is used as the base material, conventionally, warpage may occur in the optical waveguide due to the stress during curing of the cladding portion and the core portion. On the other hand, since the optical waveguide manufactured by the manufacturing method according to the present embodiment can suppress the above-mentioned warpage, it can be expected to smoothly perform the application of the optical waveguide to the transmission path and the mounting of the optical waveguide on the optoelectronic integrated circuit. In one example, the warpage amount of the optical waveguide is preferably 1 cm or less, more preferably 5 mm or less. The warpage amount can be measured by the method described in the examples below.

[0128] The diameter of the core portion in the optical waveguide may be set according to the design of the optical waveguide. In one example, the range of the specific diameter of the core portion is preferably 0.5 μm or more, more preferably 1 μm or more, still more preferably 5 μm or more, preferably 100 μm or less, more preferably 70 μm or less, still more preferably 50 μm or less, and may be 30 μm or less, 20 μm or less, or 10 μm or less.

[0129] The distance between the core parts is preferably set appropriately within a range that allows light transmission. The specific range of the distance between the core parts is preferably 50 μm or more, more preferably 70 μm or more, still more preferably 100 μm or more, and preferably 1000 μm or less, more preferably 500 μm or less, still more preferably 300 μm or less.

[0130] The thickness of the cladding part in the optical waveguide is usually larger than the diameter of the core part. The specific thickness of the cladding part is preferably 5 μm or more, more preferably 10 μm or more, still more preferably 100 μm or more, and preferably 1,000 μm or less, more preferably 800 μm or less, still more preferably 600 μm or less.

[0131] The wavelength of light that the optical waveguide can transmit can be selected in various ways. For example, the preferred wavelength range of the transmitted light can be 840 nm to 860 nm (e.g., 850 nm), 1300 nm to 1320 nm (e.g., 1310 nm), 1540 nm to 1560 nm (e.g., 1550 nm), etc. Among them, the wavelength range of the light transmitted through the optical transmission path is preferably 1300 nm to 1320 nm.

[0132] The optical waveguide may be a single-mode optical waveguide or a multi-mode optical waveguide, but it is preferably a single-mode optical waveguide. Among them, the optical waveguide is preferably a single-mode optical waveguide for light in the above-mentioned preferred wavelength range. For example, the optical waveguide is preferably a single-mode optical waveguide for 1310 nm light.

[0133] In an optical waveguide, the refractive index distribution between the cladding portion and the core portion may be discontinuous or continuous. For example, when the refractive index distribution between the cladding portion and the core portion is discontinuous, an interface of refractive index is formed between the cladding portion and the core portion, so that a step-index type (SI type) optical waveguide can be obtained. Also, when the refractive index distribution between the cladding portion and the core portion is continuous, a graded-index type (GI type) optical waveguide can be obtained. In many cases, according to the manufacturing method according to the above-described embodiment, a graded-index type optical waveguide can be manufactured, but a step-index type optical waveguide may also be manufactured.

[0134] <Any process> The manufacturing method of the optical waveguide is not limited to the above-described embodiment, and may be further modified and implemented. For example, in the above-described embodiment, an example of forming the uncured core portion 410 one by one using one discharge portion 300 is shown, but a plurality of core portions 410 may be formed simultaneously using a plurality of discharge portions 300. As a specific example, while discharging the photosensitive resin composition for the core, a plurality of uncured core portions 410 may be simultaneously formed in the uncured cladding portion 210 by moving a plurality of needle-like portions 310.

[0135] In the above-described embodiment, the support 100 is formed of separate members, namely the base material 110 and the frame portion 120, but these may be integrally formed of the same member. For example, when a circuit board is used as the support 100, a concave portion such as a trench may be formed in the circuit board, and the uncured cladding portion 210 may be formed in the concave portion.

[0136] The manufacturing method of the optical waveguide may further include an arbitrary process in combination with the above-described processes. As a specific example, the manufacturing method of the optical waveguide may include a process of removing the cladding portion 200 and the core portion 400 from the support 100.

[0137] Further, the method for manufacturing an optical waveguide may include a step of providing an arbitrary element other than the support 100, the cladding portion 200, and the core portion 400 to the optical waveguide. Examples of the arbitrary element include a protective layer (not shown) that protects the cladding layer 200 and the core portion 400, a conductive layer such as a plating layer (not shown), and the like.

[0138] Furthermore, the method for manufacturing an optical waveguide may include a step of dicing the manufactured optical waveguide, and may also include a step of removing the misalignment portion 411 near the end point of the core portion 400 by a removal process such as cutting and polishing.

Example

[0139] Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. In the following description, "parts" and "%" representing amounts mean "parts by mass" and "mass%", respectively, unless otherwise specified. Further, the operations described below were performed in the air at normal temperature and pressure (23°C, 1 atm) unless otherwise specified.

[0140] <Synthesis Example 1: Production of silicone-based resin A> Into a 100 mL three-necked eggplant flask equipped with a Dean-Stark trap, 21.6 g (0.10 mol) of DPSD (manufactured by Tokyo Chemical Industry Co., diphenyldisilanediol), 25.0 g (0.10 mol) of STMS (manufactured by Shin-Etsu Chemical Co., trimethoxy(4-vinylphenyl)silane), and 30 g of toluene were charged to obtain a mixture. The inside of the flask was purged with nitrogen using a nitrogen balloon. After heating the mixture to 50 °C, 19 mg (0.1 mmol) of barium hydroxide monohydrate (manufactured by MERCK) was added and stirred for 3 hours. After further heating the mixture to 85 °C, it was stirred for 24 hours while removing the generated methanol. The obtained reaction product was cooled to room temperature, and insolubles were removed using a membrane filter with a pore size of 0.2 μm. Thereafter, toluene was distilled off using an evaporator and a vacuum pump to obtain 32.2 g of a vinyl group-containing silane compound as a colorless transparent oily substance. The weight average molecular weight Mw of the vinyl group-containing silane compound measured by GPC in terms of polystyrene conversion was 972, and the dispersity: Mw (weight average molecular weight) / Mn (number average molecular weight) was 1.6.

[0141] <Production Example 1: Production of Photosensitive Resin Composition 1> 15 parts of a photocurable resin ("A-DOG" manufactured by Shin-Nakamura Chemical Co., dioxane glycol diacrylate), 30 parts of a urethane acrylate resin containing a polyether backbone ("UN-6306" manufactured by Negami Kogyo Co.), 5 parts of an epoxy acrylate resin containing an epoxy group ("EBECRYL 3605" manufactured by Daicel Allnex Co., epoxy equivalent 450 g / eq., a half acrylate obtained by esterifying one epoxy group of a bisphenol A type epoxy resin), and 0.1 part of a photopolymerization initiator ("Irgacure OXE-01" manufactured by BASF) were mixed using a high-speed rotary mixer to prepare Resin Composition 1 (Resin Ink 1). The obtained Resin Composition 1 was filled into a 50 mL UV-block syringe ("PSY-50-FU-OR" manufactured by Musashi Engineering Co.), and stirring and defoaming were performed for 2 minutes using a centrifugal defoamer for syringes ("AW-50-3" manufactured by Musashi Engineering Co.).

[0142] <Production Examples 2 to 14: Production of Resin Compositions> Resin compositions 2 to 14 were prepared in the same manner as in Production Example 1, except that the components shown in Tables 1 and 2 were mixed in the amounts (parts by mass) described in the tables. In Tables 1 and 2, the meanings of the abbreviations are as follows.

[0143] (A) (Meth)acrylate resin: · "A-DOG": Manufactured by Shin-Nakamura Chemical Co., Ltd., dioxane acrylic monomer glycol diacrylate, Mw = 326, number of (meth)acryloyl groups N = 2, Mw / N = 163 · "EA-0200": Manufactured by Osaka Gas Chemical Co., Ltd., 9,9-bis[4-(2-acryloyloxyethyloxy)phenyl]fluorene, Mw = 546, number of (meth)acryloyl groups N = 2, Mw / N = 273 · "UN-6306": Manufactured by Negami Industries Co., Ltd., urethane acrylate resin containing a polyether skeleton, Mw = 6600, number of (meth)acryloyl groups N = 2, Mw / N = 3300 · "PMH-401H": Manufactured by Negami Industries Co., Ltd., urethane acrylate resin containing a polyether skeleton, Mw = 19000, number of (meth)acryloyl groups N = 2, Mw / N = 9500 · "EBECRYL 3708": Manufactured by Daicel Ornex Co., Ltd., modified bisphenol A type epoxy acrylate, Mw = 1500, number of (meth)acryloyl groups N = 2, Mw / N = 750 · "UN-9200A": Manufactured by Negami Industries Co., Ltd., urethane acrylate resin containing a polycarbonate skeleton, Mw = 13000, number of (meth)acryloyl groups N = 2, Mw / N = 6500 · "M-3N": Manufactured by Negami Industries Co., Ltd., urethane acrylate resin containing a polyether skeleton, Mw = 560, number of (meth)acryloyl groups N = 3, Mw / N = 187 · "EBECRYL 3701": Manufactured by Daicel Ornex Co., Ltd., epoxy acrylate resin, Mw = 850, number of (meth)acryloyl groups N = 2, Mw / N = 425 · "EBECRYL 3605": Manufactured by Daicel Ornex Co., Ltd., bisphenol A type epoxy half acrylate, Mw = 412, number of (meth)acryloyl groups N = 1, Mw / N = 412 · "Biscuit 3F": Manufactured by Osaka Organic Chemical Industry Co., Ltd., 2,2,2-trifluoroethyl acrylate, Mw = 154, number of (meth)acryloyl groups N = 1, Mw / N = 154) · "KBM-503": Manufactured by Osaka Organic Chemical Industry Co., Ltd., 3-methacryloxypropyltrimethoxysilane, Mw = 248, number of (meth)acryloyl groups N = 2, Mw / N = 124)

[0144] (B) Photoinitiator: · "Irgacure OXE-01": Manufactured by BASF, 2-(benzoyloxyimino)-1-[4-(phenylthio)phenyl]-1-octanone

[0145] (C) Optional radically polymerizable resin: · "BPA-CA": Manufactured by Konishi Chemical Industry Co., Ltd., 2,2-bis(3-allyl-4-hydroxyphenyl)propane, Mw = 306 · "Synthesis Example 1": Vinyl group-containing silane compound synthesized in Synthesis Example 1, Mw = 972

[0146] <Method for Measuring Refractive Index of Cured Product of Photosensitive Resin Composition> The refractive index of the cured product of the resin composition produced in the above-described production example was measured by the following method. The resin composition was applied onto a silicon wafer, exposed at an illuminance of 3,000 mW / cm 2 and then heated at 150 °C for 30 minutes to obtain a cured product. The refractive index n (measurement wavelength 1310 nm) of the obtained cured product was measured at room temperature and normal pressure using a 2010M type prism coupler (manufactured by Metricon) with 1310 nm laser light.

[0147] <Method for Measuring Viscosity> The viscosity of the resin composition produced in the above-described production example was measured by the following method. 0.22 ml of the resin composition was introduced into an E-type viscometer ("RE-80U" manufactured by Toki Sangyo Co., Ltd.), and the viscosity was measured under the conditions of 5 rpm and 2 minutes using a rotor of 3°×R9.7 in accordance with the procedure compliant with JIS-K7117-2.

[0148]

Table 1

[0149]

Table 2

[0150] <Examples 1 to 11 and Comparative Examples 1 to 2> As described in Table 3 and Table 4, a combination of a photosensitive resin composition for a core and a photosensitive resin composition for a clad was selected from the photosensitive resin compositions of the production examples, and an optical waveguide was fabricated. Hereinafter, a specific manufacturing method of the optical waveguide will be described.

[0151] (Manufacture of the base evaluation substrate A) 60 parts of cresol novolak skeleton-containing acid-modified epoxy acrylate resin (“CCR-1171H” manufactured by Nippon Kayaku Co., Ltd.), 20 parts of biphenyl type epoxy resin (“YX4000H” manufactured by Mitsubishi Chemical Corporation), 40 parts of a photocurable resin (“DPHA” manufactured by Nippon Kayaku Co., Ltd., dipentaerythritol hexaacrylate), 2.0 parts of a photopolymerization initiator (“Omnipol379” manufactured by IGM), 4.0 parts of melamine, and 25 parts of barium sulfate (“Variess B-30” manufactured by Sakai Chemical Industry Co., Ltd.), 2 parts of a green pigment (“CG5370” manufactured by Dainichi Seika Kogyo Co., Ltd.) were mixed, and methyl ethyl ketone was further added so that the non-volatile component concentration became 60% by mass, and the mixture was stirred using a high-speed rotary mixer to prepare a varnish-like solder resist composition.

[0152] A polyethylene terephthalate film (PET film; “Lumirror T6AM” manufactured by Toray Industries, Inc., thickness 38 μm, softening point 130 ° C) was prepared. The varnish-like solder resist composition prepared above was uniformly applied to such a PET film using a die coater and dried at 75 ° C to 110 ° C for 10 minutes to form a solder resist layer having a thickness of 25 μm. Through these operations, a resin sheet including a photosensitive solder resist layer and a PET film was obtained.

[0153] A copper-clad laminate comprising a glass epoxy substrate and a 18-μm-thick copper layer formed on the surface of the glass epoxy substrate was prepared. The copper layer of the copper-clad laminate was roughened with a surface treatment agent containing an organic acid (Mektec's "CZ8100"). A resin sheet was placed on the copper-clad laminate so that the solder resist layer was in contact with the copper-clad laminate, and they were laminated using a vacuum laminator (Nitto Materials' "VP160"). The lamination conditions were a vacuum evacuation time of 30 seconds, a crimping temperature of 60°C, a crimping pressure of 0.3 MPa, and a pressurization time of 30 seconds. Thereafter, the PET film was peeled off.

[0154] Using a projection exposure apparatus (USHIO INC.'s "UFX-2240"), ultraviolet exposure was performed on the solder resist layer at an exposure energy at which the number of gloss remaining steps of a 41-step tablet was 8 steps. The exposure was performed without using a quartz glass mask. After leaving it at room temperature for 30 minutes after the exposure, the photosensitive resin composition in the unexposed portion was spray-developed with a 1 mass% aqueous sodium carbonate solution at 30°C for 60 seconds, and further ultraviolet irradiation of 2 J / cm 2 was performed. Thereafter, it was put into a clean oven, heated from room temperature to 160°C, and after reaching 160°C, heat treatment was performed for 90 minutes in a nitrogen atmosphere to cure the solder resist layer, and a base evaluation substrate A as a base material was obtained. The obtained base evaluation substrate A had a layer structure of "copper-clad laminate / solder resist layer".

[0155] (Formation of uncured clad portion) The obtained base evaluation substrate A was cut into a size of 3 cm in length × 15 cm in width, and five layers of polyimide tape (thickness 65 μm, Kapton (registered trademark) tape) were attached. By cutting out the central portion (1 cm in length × 10 cm in width) of the attached polyimide tape with a cutter to form a frame portion, a support was obtained. The frame portion of the support was gently filled with a photosensitive resin composition for clad. Thereafter, voids and dust were removed with tweezers and left standing for 10 minutes. Thereafter, an uncured clad portion with a thickness of about 500 μm was formed by rubbing on the polyimide tape with a slide glass.

[0156] (Formation of uncured core portion) A support with a clad part formed thereon was placed on the worktable of a high-precision general-purpose desktop robot (Musashi Engineering, Inc.'s "SHOTMASTER (registered trademark) 300ΩX") located in a constant-temperature chamber maintained at 23°C. Next, a 50 mL UV-blocking syringe filled with a photosensitive resin composition for the core was attached with a discharge part having a needle-like part at its tip (a metal needle "SNA-26G-C" manufactured by Musashi Engineering, Inc.) and mounted on the desktop coating robot. At this time, as the discharge part, one having a needle-like part with an inner diameter described in Table 3 or Table 4 was selected and attached.

[0157] The needle-like part at the tip of the discharge part was inserted into the clad part, and the position of the discharge part was adjusted so that the height from the surface of the base evaluation substrate A to the tip of the needle-like part was 150 μm. The discharge pressure of a digital control dispenser ("SuperΣCMIII" manufactured by Musashi Engineering, Inc.) that controls the discharge of the photosensitive resin composition for the core from the discharge part was set to the value shown in Table 3 or Table 4. Also, the drawing speed of the high-precision general-purpose desktop robot (the moving speed of the needle-like part provided in the discharge part) was set to 15 mm / second. While discharging the photosensitive resin composition for the core from the needle-like part into the clad part, the discharge part was swept from left (starting point) to right toward the device. By this sweeping of the discharge part, the needle-like part linearly moved so that the core part had a length of 8 cm starting from a position where the height from the surface of the base evaluation substrate A to the tip of the needle-like part was 150 μm. At the end point, the discharge part and the needle-like part it provided were stopped for 0.5 seconds, and then the discharge part was lifted and the needle-like part was withdrawn from the uncured clad part. By this operation, a channel 1 as an uncured core part was formed in the clad part.

[0158] Immediately thereafter, at a position 1 mm before the starting point of channel 1, the needle-like part was inserted into the clad part. In the same manner as the formation of channel 1, the needle-like part was moved while discharging the photosensitive resin composition for the core, the needle-like part was stopped at the end point, and the needle-like part was withdrawn from the uncured clad part to form a channel 2 as an uncured core part.

[0159] Further, the channels 3, 4, and 5 were formed by repeating the same method as that of channel 2, except that the position where the needle-like part was inserted into the clad part was moved 1 mm forward each time, and a total of five channels of uncured core parts were formed in the clad part.

[0160] (Curing of the core part and the clad part) The clad part in which five channels were formed as uncured core parts was immediately irradiated with light equivalent to an illuminance of 3,000 mW / cm 2 (365 nm detection) to cure the core part and the clad part. The above-mentioned light irradiation was carried out by sweeping a UV-LED head with a wide-range irradiation lens (365 nm, manufactured by HOYA Corporation) installed on a high-precision general-purpose desktop robot back and forth 10 times at a speed of 10 mm / sec. Then, the core part and the clad part were further cured by heating in an oven at 150°C for 30 minutes to obtain an optical waveguide sample B. The obtained optical waveguide sample B included a base evaluation substrate A, a clad part formed on the base evaluation substrate A, and five core parts formed in the clad part.

[0161] <Evaluation test of the core shape at the end point> The end point part of the core part of the obtained optical waveguide sample B was observed at a magnification of 200 times using a digital microscope ("VHX-8000" manufactured by Keyence Corporation). The length of the part where the core part was displaced was measured as the displacement amount. Specifically, in both the examples and comparative examples where displacement occurred, the part where the core part was pulled was seen to extend in a shape different from the part on the starting point side of that part. This pulled part extended upward in the gravitational direction (i.e., the extraction direction of the discharge part) and extended in the direction approaching the starting point in the sweeping direction of the discharge part. The length of the pulled part was measured as the displacement amount.

[0162] <Adhesion evaluation test> The polyimide tape as the frame portion was peeled off from the obtained optical waveguide sample B. Next, holding the ends of the base evaluation substrate A with both hands, the base evaluation substrate A was deflected by 5 mm so that the clad portion side faced the outer peripheral side. At that time, those in which no peeling occurred between the base evaluation substrate A and the clad layer were judged as "good", and those in which peeling occurred were judged as "bad".

[0163] <Bending evaluation test> The side on the starting point side of the obtained optical waveguide sample B was fixed to a horizontal support surface with a polyimide tape. At that time, the height of the vertices on the end point side of the optical waveguide sample B (that is, the vertices at both ends of the side on the end point side) from the support surface was measured. The measured maximum height was obtained as the amount of warp.

[0164] <Loss evaluation test> (1. Preparation of test substrate) The optical waveguide sample B manufactured by the above operation was cut, and the portion where the core layer was formed was cut out. Specifically, a portion including a 5 cm linear core portion and the clad portion around it was cut out to obtain a test substrate C provided with an optical waveguide. The cutting conditions are as follows. · Dicing device: DAD3221 (manufactured by DISCO Corporation) · Blade: ZH14 - SD4000 - VI - 50 · Spindle rotation speed: 30K / min · Cutting speed: 5 mm / sec · Blade height: 0.060 mm · Dicing tape: T - 80W (manufactured by Denka Co., Ltd., 80μm thick)

[0165] (2. Measurement of optical transmission loss of calibration optical system) As described below, the transmission loss of the optical system with the test substrate C and the condenser module removed was measured from the optical system for measuring the transmission loss of the test substrate C. That is, on a vibration isolation table covered with a dark curtain, a light source (1310 nm light source, "LPSC-1310-FC" manufactured by THORLABS) and a light receiver (optical power meter "N7742" manufactured by Keysight Technologies) were connected via an optical fiber (input fiber) to obtain a calibration optical system. The light source was caused to emit light, and the intensity of the light that entered the light receiver was measured by the light receiver to measure the loss of this calibration optical system.

[0166] (3. Measurement of Optical Transmission Loss of Optical Waveguide) The test substrate C was placed on a vibration isolation table covered with a dark curtain. A condenser module (numerical aperture 0.18) was connected to one end (input end) of the optical waveguide of the test substrate C, and further a light source (1310 nm light source, "LPSC-1310-FC" manufactured by THORLABS) was connected to the condenser module via an optical fiber (input fiber). Also, another condenser module (numerical aperture 0.18) was connected to the other end (output end) of the optical waveguide of the test substrate C, and further a light receiver (optical power meter "N7742" manufactured by Keysight Technologies) was connected to the condenser module via an optical fiber (output fiber). Through the above operations, an optical system was obtained in which the light emitted from the light source passed through the optical fiber (input fiber), condenser module, optical waveguide, condenser module, and optical fiber (output fiber) in this order and then entered the light receiver. Hereinafter, this optical system may be referred to as a "sample optical system". The light source was caused to emit light, and the intensity of the light that entered the light receiver was measured by the light receiver to measure the transmission loss of the sample optical system.

[0167] The transmission loss of the calibration optical system was subtracted from the transmission loss of the sample optical system to obtain the transmission loss of the optical waveguide included in the test substrate C.

[0168] (4. Measurement of Optical Transmission Loss per Unit Distance (dB / cm)) After measuring the transmission loss of the optical waveguide with a length of 5 cm, the optical waveguide was cut to 4 cm. Using the thus obtained optical waveguide with a length of 4 cm, the transmission loss of the optical waveguide was measured by the same method as in (3. Measurement of the optical transmission loss of the optical waveguide).

[0169] Thereafter, the optical waveguide was cut to 3 cm. Using the thus obtained optical waveguide with a length of 3 cm, the transmission loss of the optical waveguide was measured by the same method as in (3. Measurement of the optical transmission loss of the optical waveguide).

[0170] The measurement results of the transmission loss of the optical waveguide with a length of 5 cm, the transmission loss of the optical waveguide with a length of 4 cm, and the transmission loss of the optical waveguide with a length of 3 cm were plotted in a coordinate system with the length of the optical waveguide on the horizontal axis and the transmission loss of the optical waveguide on the vertical axis to obtain the coordinates of three points representing the measurement results. The approximate straight line of these three points was calculated by the least squares method, and the slope of the approximate straight line was obtained as the transmission loss per unit distance (optical transmission loss) of the optical waveguide.

[0171] <Results> The results of the above-described examples and comparative examples are shown in the following table. In the warpage evaluation test in Comparative Example 2, the cladding layer was easily peeled off, and the warpage amount could not be measured. In the following table, the meanings of the abbreviations are as follows. Needle inner diameter: The inner diameter of the needle-like part. Needle length: The length of the needle-like part. Scanning speed: The moving speed of the needle-like part.

[0172]

Table 3

[0173]

Table 4

Explanation of Symbols

[0174] 100 Support 110 Base material 110U Surface 120 Frame part 120a opening 200 hardened clad part 210 unhardened clad part 300 ejection part 310 needle-like part 311 tip of the needle-like part 320 ejection part body 400 hardened core part 410 unhardened core part 410S starting point 410E end point 411 displacement part 500 optical waveguide

Claims

1. A first step of piercing a needle-like portion at the tip of a discharge portion into an uncured clad portion formed of a photosensitive resin composition for a clad; A second step of forming an uncured core portion surrounded by the uncured clad portion by relatively moving the needle-like portion within the uncured clad portion while discharging the photosensitive resin composition for a core from the needle-like portion; A third step of removing the needle-like portion from the uncured clad portion; A fourth step of curing the uncured clad portion and the uncured core portion, which is a method for manufacturing an optical waveguide; The photosensitive resin composition for a core contains one or more (meth)acrylate resins selected from the group consisting of urethane (meth)acrylate resins and epoxy (meth)acrylate resins; A method for manufacturing an optical waveguide, wherein the photosensitive resin composition for a clad contains one or more (meth)acrylate resins selected from the group consisting of urethane (meth)acrylate resins and epoxy (meth)acrylate resins.

2. The method for manufacturing an optical waveguide according to Claim 1, wherein the (meth)acrylate resin contained in the photosensitive resin composition for a core contains one or more selected from the group consisting of a urethane (meth)acrylate resin containing a polyether skeleton and an epoxy (meth)acrylate resin containing a bisphenol A skeleton.

3. The method for manufacturing an optical waveguide according to Claim 1, wherein the photosensitive resin composition for a core contains 70% by mass or more of a (meth)acrylate resin with respect to 100% by mass of the non-volatile components of the photosensitive resin composition for a core.

4. The method for manufacturing an optical waveguide according to Claim 1, wherein the photosensitive resin composition for a clad contains 70% by mass or more of a (meth)acrylate resin with respect to 100% by mass of the non-volatile components of the photosensitive resin composition for a clad.

5. The parameter D represented by the following formula (1) ｃｌａｄ is 400 or more and 5000 or less, and the method for manufacturing an optical waveguide according to claim 1. 【Number 1】 (In formula (1), W ｃｌａｄ represents the content ratio (mass %) of each (meth)acrylate resin contained in the photosensitive resin composition for cladding, based on 100 mass % of the nonvolatile components of the photosensitive resin composition for cladding. C ｃｌａｄ represents a value Mw / N obtained by dividing the weight average molecular weight Mw of each (meth)acrylate resin contained in the photosensitive resin composition for a cladding by the number N of (meth)acryloyl groups possessed by one molecule of the (meth)acrylate resin.)

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