KR100878032B1 - Method for manufacturing flexible optical waveguide - Google Patents

Abstract

A method for manufacturing flexible optical waveguide is provided to allow an optical wave guide to be thin while having excellent flexibility by using epoxy adhesive part as a clad layer. A method for manufacturing flexible optical waveguide is comprised of steps: arranging a coverlay layer consisting of polyimide and epoxy adhesive upper and lower part of a core layer; arranging epoxy adhesive part to face a core layer; laminating the coverlay layer by pressurizing each coverlay with a hot press from the outside of coverlay to the core layer(S120); forming the optical waveguide including polyimide layer(S130).

Description

Method for manufacturing high bending optical waveguide

The present invention relates to a method for manufacturing a high bending optical waveguide, and more particularly, to a method for manufacturing a high bending optical waveguide having improved bendability of an optical waveguide.

The optical waveguide corresponds to a waveguide for transmitting light, and includes a core part having a high refractive index near the center and a clad part having a low refractive index around the core. .

Light incident on the optical waveguide propagates through the core while repeating total reflection on the interface between the core and the cladding.

However, as the conventional optical waveguide develops the core and the clad material in a liquid state, the flexibility is inferior even after each liquid material is cured, and its use is limited, or the durability of the optical waveguide is damaged when frequent bending occurs. Or there is a problem that is broken.

In addition, since the thickness of the cladding layer is manufactured to be thick, there are limitations in making a slim optical waveguide and its applicability is also limited.

The present invention was created in order to solve the above-described problems, by using the epoxy adhesive layer of the coverlay (Claylay) when forming the cladding layer of the optical waveguide excellent flexibility and not easily broken and can be manufactured to be slim, high flexibility It is an object of the present invention to manufacture a method for producing a high bending optical waveguide that can be further enhanced the optical waveguide.

High bending optical waveguide manufacturing method of the present invention for achieving the above object, the core layer forming step of forming a core layer; A coverlay layer made of polyimide and an epoxy adhesive is disposed on the upper and lower portions of the core layer, respectively, and the epoxy adhesive portion is disposed toward the core layer, so that the coverlay layer is disposed on the upper and lower portions of the core layer. A coverlay layer stacking step of pressing each coverlay layer with a hot press toward a core layer; And forming an optical waveguide by pressing the hot press to form an optical waveguide including a cladding layer made of the epoxy adhesive surrounding the outer circumference of the core layer and a polyimide layer disposed above and below the cladding layer, respectively. .

Here, the epoxy adhesive may be a transparent epoxy adhesive.

In addition, the core layer may be a polymer material.

According to the high bending optical waveguide manufacturing method according to the present invention provides the following effects.

First, in the upper and lower core layer, the coverlay layer made of polyimide and epoxy adhesive is laminated by hot press at high temperature and high pressure, and the epoxy adhesive portion is used as a clad layer, which has excellent bendability and is not easily broken, and is slim and thin. Since it can be manufactured as an optical waveguide that can further improve the flexibility is possible advantage.

In addition, since the core layer is made of a polymer material, there is little risk of breakage during bending, and the use of a transparent epoxy adhesive as an epoxy adhesive constituting the clad layer may reduce the transmission loss of light.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Prior to this, terms or words used in the specification and claims should not be construed as having a conventional or dictionary meaning, and the inventors should properly explain the concept of terms in order to best explain their own invention. It should be interpreted as meanings and concepts corresponding to the technical idea of the present invention based on the principle of definition.

Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

1 is a flow chart of a method for manufacturing a high bending optical waveguide according to an embodiment of the present invention, Figure 2 is a structure of a general coverlay, Figure 3 is a cross-sectional view showing a manufacturing process of the high bending optical waveguide of the present invention using Figure 2, Figure 4 3 is a side cross-sectional view showing a light transmission path according to the optical waveguide configuration of FIG. 3, and FIG. 5 is a cross-sectional view showing a conventional optical waveguide structure.

Hereinafter, a method of manufacturing a high bending optical waveguide according to an embodiment of the present invention will be described in more detail with reference to FIGS. 1 to 5.

First, the core layer 10 of FIG. 3 serving as a transmission path of light on the optical waveguide is formed (S110).

The refractive index n of the core layer 10 may have a range of 1.5 to 1.6 as usual, and the core layer 10 may have a polymer having a refractive index n within the range of 1.5 to 1.6 described above. It may be made of a material.

The material used as the core layer 10 may be a quartz-based (glass) or a polymer-based, but the quartz-based is difficult to be broken during bending and thus difficult to be used as a flexible optical waveguide. In the present invention, it is preferable that the above-described polymer material is used as the material of the core layer 10.

On the other hand, since the method for forming the core layer 10 is variously disclosed in the prior art, a more detailed description thereof will be omitted.

In addition, although the cross section of the core layer 10 is shown as a quadrangular shape in FIG. 3, the present invention is not limited to the quadrangular shape, and the core layer 10 having various cross-sectional shapes may be applied. .

In addition, the core layer 10 may be arranged in one or more various numbers (for example, three as shown in FIG. 3), but is not necessarily limited to the above-described example, and the number of formation of the core layer 10 is as described above. Is a part which can be variously changed according to the circuit design (required number of optical transmission paths).

After forming the core layer 10 (S110), as shown in FIG. 3, a coverlay layer 20 made of a polyimide 21 and an epoxy adhesive 22 may be disposed on upper and lower portions of the core layer 10. Each of the epoxy adhesives 22 may be disposed to face the core layer 10, and the core layer 10 may be disposed on the outer side of each coverlay layer 20 disposed above and below the core layer 10. Pressing the coverlay layer 20 between the hot press (not shown) toward (S120).

The polyimide (PI) is a material having excellent heat resistance, chemical resistance, abrasion resistance, chemical resistance, and bending resistance, as well as excellent mechanical strength, impact strength, and electrical insulation. The coverlay layer 20 made of the polyimide 21 and the epoxy adhesive 22 has excellent flexible characteristics in itself and thus, a flexible printed circuit board (FPCB) or a dynamic layer board (FCCL). It is widely used in manufacturing flexible copper clad laminate.

Here, the coverlay layer 20 is made of the above-described polyimide 21 and the epoxy adhesive 22 under the polyimide 21, as shown in Figure 2 is commonly referred to as a coverlay, the present invention By using the coverlay layer 20 described above, the flexibility of the optical waveguide can be improved.

On the other hand, the epoxy adhesive 22 is a thermosetting material that is physically changed from the initial semi-cured state to a hardened state by high temperature heat, that is, a material that can be hardly cured by high temperature pressurization of the hot press (not shown). to be.

Here, the epoxy adhesive 22 is a portion for forming the cladding layer 30 of the optical waveguide after surrounding the periphery of the core layer 10 as shown in the right side of Figure 3, the refractive index (n) of the core layer 10 It may have a refractive index in the range of 1.4 to 1.5, the refractive index (n) value smaller than the range of 1.5 to 1.6. Since the cladding layer 30 has a lower refractive index n than the core layer 10 corresponds to the basic specification of the optical waveguide, a detailed description thereof will be omitted.

On the other hand, in the coverlay layer stacking step (S120), the temperature conditions of the hot press applied to the coverlay layer 20 is 100 ℃ to 200 ℃, the pressing conditions of the hot press is 30kgf / ㎠ to 100kg f / cm 2.

According to the above-described high temperature conditions, the curing of the thermosetting epoxy adhesive 22 included in the coverlay layer 20 is induced, and according to the pressure conditions, between the core layer 10 and the core layer 10 The gap and the circumference of each core layer 10 so that the epoxy adhesive 22 is evenly introduced and filled.

On the other hand, after the coverlay layer stacking step (S120) described above, by pressing the hot press (not shown) as shown in the right side of FIG. 3, to the epoxy adhesive 22 surrounding the outer periphery of the core layer 10 The optical waveguide 100 of the present invention including the cladding layer and the polyimide layer 40 disposed on the upper and lower portions of the cladding layer 30 is formed (S130).

That is, as the epoxy adhesive 22 is enclosed and cured around the outer circumference of the core layer 10 through the pressurization of the hot press, the clad made of the epoxy adhesive 22 along the outer circumference of the core layer 10. Layer 30 may be formed.

In addition, as the polyimide layer 40 is covered on the upper and lower portions of the clad layer 30, the optical waveguide 100 having high flexibility may be completed.

The polyimide layer 40 has excellent heat resistance, chemical resistance, abrasion resistance, chemical resistance, flex resistance, mechanical strength, impact strength, and electrical insulation, which are characteristics of the polyimide 21 itself as described above. The characteristics of the optical waveguide 100 also have the effect of making it robust to external factors, as well as excellent ductility, and can greatly improve the flexibility of the optical waveguide 100 of the present invention.

4 is a side cross-sectional view of the optical waveguide of FIG. 3, that is, a cross-sectional view along a light propagation path, and as shown, the optical waveguide 100 manufactured according to the present invention has a refractive index n ranging from 1.5 to 1.6. The cladding layer 30 and the cladding layer 30 having a core layer 10 having a C) and a refractive index n in the range of 1.4 to 1.5, which is a lower refractive index than the core layer 10 around the core layer 10. It consists of a polyimide layer 40 laminated on the top and bottom of.

Here, as the light incident on the optical waveguide is shown in FIG. 4, the total reflection is repeated on the interface between the core layer 10 and the clad layer 30 while the optical waveguide 100 or the core layer 10 extends in the longitudinal direction. As it propagates through the core layer 10.

Here, comparing the angle of incidence performance between the optical waveguide 100 of the present invention and the conventional optical waveguide (3) developed by other companies are shown in Table 1.

TABLE 1

Comparison parameter Optical waveguide 100 of the present invention (FIG. 3 or 4) Conventional optical waveguide 3 (FIG. 5) Refractive index of the core layer (n1) 1.5, core layer (10) 1.586, core layer (1) Refractive index of the cladding layer (n2) 1.4, cladding layer 30 1.551, cladding layer (2) Incidence angle (θ = sin ^-1 (n2 / n1)) 68.9 ° 78 °

FIG. 5 shows a conventional optical waveguide 30 composed of a core layer 1 and a cladding layer 2, in which a core layer 1 is laminated on a lowermost cladding layer 2a. (1) It is formed by stacking the upper cladding layer 2b again on top.

The present invention as shown in FIG. 3 adopts 1.5 and 1.4 as the refractive indices n of the core layer 10 and the cladding layer 30, respectively, and is incident in the incident angle range of 68.9 ° or more, that is, in the range of 68.9 ° to 90 °. It is possible to transmit about light.

In contrast, conventionally, 1.586 and 1.551 are employed as the refractive indices n of the core layer 1 and the cladding layer 2, respectively, and are applied to light incident in the incident angle range of 70 ° or more, that is, 70 ° to 90 °. About the transmission is possible.

That is, in the case of the present invention, since the difference in refractive index between the core layer 10 and the cladding layer 20 is large, the range of the incident angle θ through which the light can be transmitted through the core layer 10 is also the conventional case. As it is wider than, the selection or adjustment of the incident angle is advantageous and easy compared with the conventional case.

On the other hand, it is preferable that the epoxy adhesive 22 forming the cladding layer 30 is a transparent epoxy adhesive.

That is, the epoxy adhesive 22 should be maintained in a transparent state even after curing by the high temperature of the hot press, which is the same as when the clad layer 30 made of the epoxy adhesive 22 is opaque. This is because loss of light may occur due to the opacity of the cladding layer 30 on the propagation path of light through the core layer 10.

In general, optical waveguide material development companies develop the refractive index of the core layer is usually about 1.5 to 1.6, and the clad layer is manufactured to the optical waveguide by making the refractive index about 0.03 to 0.05 lower than the core layer.

In addition, as the incidence angle-related equation of FIG. 4, in general, as the difference in refractive index between the core layer 10 and the clad layer 30 increases, total reflection may occur in a large angular range, and thus, transmission loss of light may also be reduced.

Here, the transmission loss of light can be reduced according to the transparency of the cladding layer 30, that is, the air having the refractive index of 1 can be considered to have the highest transparency.

For example, in FIG. 5, when there is only air around the core layer 1, the propagation loss is about 0.01 dB / cm (absorption loss of the core layer), indicating that there is almost no light loss due to the high transparency of the air. Can be.

As another example of FIG. 5, when the cladding layer 2 having the refractive index n is 1.551 around the core layer 1 having the refractive index n of 1.585, the propagation loss is about 0.05 dB / cm. The value of 0.05 dB / cm includes the loss due to the absorption loss of the core layer 1, the loss of the nonuniformity of the bonding surface between the core layer 1 and the cladding layer 2, and the loss due to the transparency of the cladding layer 20. Corresponds to)

Therefore, in order to reduce the propagation loss described above, it is preferable that the transparency of the cladding layer 30 is secured, and in the present invention, the epoxy adhesive 22, which is the configuration of the coverlay layer 20, is applied as a transparent epoxy adhesive. As a result, there is an effect of reducing the loss of light on the optical waveguide 100 of the present invention.

The opacity and transparency of the epoxy adhesive 22 can be controlled differently according to the manufacturing process or manufacturing purpose of the manufacturer, and are actually divided into opaque adhesives and transparent adhesives, and are variously sold in the present invention. It is possible to realize by adopting and applying an epoxy adhesive having transparency while the refractive index n is in the range of 1.4 to 1.5 in the epoxy adhesive 22.

On the other hand, the high bending optical waveguide 100 of FIG. 3 manufactured by the present invention as described above has an advantage that can be manufactured to a slim thickness compared to the conventional optical waveguide 3 as shown in FIG.

In the case of the left side of FIG. 3, an embodiment regarding the thickness of the core layer 10 and the coverlay layer 20, which are raw materials, is shown. The polyimide 21 and the epoxy adhesive 22 constituting the coverlay layer 20 are shown. The thickness of 12.5㎛, 15㎛ are used, respectively, the core layer 10 may be used a thickness of 20㎛.

Here, the thickness of the polyimide 21 and the epoxy adhesive 22 constituting the coverlay layer 20 is not an arbitrarily set thickness and is one of the embodiments of the thickness specification of the coverlay which is actually used in the field of FPCB. In addition, the fine thickness has an advantageous effect not only on the slimness of the optical waveguide 100 but also on the high flexibility.

Meanwhile, the coverlay layer 20 and the core layer 10 of the present invention having the above-described thickness have the core layer 10, the clad layer 30, and the polyimide as shown in the right part of FIG. The optical waveguide 100 is formed in the form of a layer 40, and the final thickness of the optical waveguide 100 may be about 50 μm to about 55 μm.

That is, the thickness of the polyimide layer 40 stacked on the upper and lower portions of the optical waveguide 100 is 12.5 μm, which has a total thickness of 25 μm, and the core layer 10 and the clad disposed between the polyimide layer 40. The thickness of the layer 30 is formed of the epoxy adhesive 22 as the epoxy adhesive 22 is filled between the core layer 10 and the circumference of the core layer 10 by the press of the hot press. The cladding layer 30 and the core layer 10 portion therein may have a thickness in the range of about 25 μm to 30 μm.

Therefore, the sum of the thickness (25 μm) of the polyimide layer 40 located above and below the optical waveguide 100 and the thickness (25 μm to 30 μm) including the core layer 10 and the cladding layer 30. As a result, the optical waveguide 100 of the present invention has a thickness of about 50 μm to 55 μm, whereby the optical waveguide 100 having a slim thickness may be manufactured, thereby further improving flexibility.

On the other hand, in the conventional case of FIG. 5, a core layer 1 having a thickness of 20 μm is formed on the clad layer 2a having a thickness of 30 μm, and again from 30 μm to the top of the core layer 1. A 50 µm thick cladding layer 2b is stacked to form an optical waveguide 3 having a total thickness of 80 µm to 100 µm.

Here, in the case of the high bending optical waveguide 100 of the present invention using the coverlay layer 20 as shown in FIG. 3, the optical waveguide 3 using the conventional general cladding layer 2 of FIG. It can be manufactured with a thickness of about 30㎛ to 45㎛ small size, according to the present invention, as well as excellent flexibility in using the coverlay layer 20, and can be manufactured in a slim, the flexibility can be further maximized There is an advantage that it is possible to provide the optical waveguide 100.

As described above, although the present invention has been described by way of limited embodiments and drawings, the present invention is not limited thereto and is described by the person of ordinary skill in the art to which the present invention pertains. Various modifications and variations are possible without departing from the scope of the appended claims.

1 is a flow chart of a method of manufacturing a high bending optical waveguide according to an embodiment of the present invention,

2 is a structure of a general coverlay,

3 is a cross-sectional view showing a high bending optical waveguide manufacturing process of the present invention using FIG.

4 is a side cross-sectional view showing an optical transmission path according to the optical waveguide configuration of FIG. 3;

5 is a cross-sectional view showing a conventional optical waveguide structure.

<Explanation of symbols for the main parts of the drawings>

10 ... core layer 20 ... coverlay layer

21 ... Polyimide 22 ... Epoxy Adhesive

30 Clad layer 40 Polyimide layer

100.High Flexure Waveguide

Claims (3)

A core layer forming step of forming a core layer; A coverlay layer made of polyimide and an epoxy adhesive is disposed on the upper and lower portions of the core layer, respectively, and the epoxy adhesive portion is disposed toward the core layer, so that the coverlay layer is disposed on the upper and lower portions of the core layer. A coverlay layer stacking step of pressing each coverlay layer with a hot press toward a core layer; And An optical waveguide forming step of forming an optical waveguide including a cladding layer made of the epoxy adhesive surrounding the outer circumference of the core layer and a polyimide layer disposed above and below the cladding layer by pressing the hot press; Method for manufacturing a curved optical waveguide. The method of claim 1, wherein the epoxy adhesive, It is a transparent epoxy adhesive, The high bending optical waveguide manufacturing method characterized by the above-mentioned. The method of claim 1, wherein the core layer, A high bending optical waveguide manufacturing method, characterized in that the polymer material.

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