CN110546119B

CN110546119B - Method for applying coating liquid to optical fiber

Info

Publication number: CN110546119B
Application number: CN201880027290.5A
Authority: CN
Inventors: R·C·穆尔; D·G·尼尔森; J·E·华生
Original assignee: Corning Inc
Current assignee: Corning Inc
Priority date: 2017-04-24
Filing date: 2018-04-16
Publication date: 2021-02-19
Anticipated expiration: 2038-04-16
Also published as: JP7050089B2; CN110546119A; JP2020517435A; RU2019137429A; DK3395775T3; NL2019098B1; RU2019137429A3; RU2763944C2

Abstract

A method of applying a coating liquid to an optical fiber is described. The fiber is drawn through the guide die into the pressurized coating chamber and through the pressurized coating chamber to the sizing die. The pressurized coating chamber contains a coating liquid. The method includes directing a coating liquid in a pressurized coating chamber in a direction transverse to a process path of the optical fiber. The lateral flow of the coating liquid counteracts the detrimental effects associated with the circulating currents that form in the pressurized coating chamber during the drawing process. Advantages of lateral flow include: the removal of bubbles, lowering the temperature of the circulating current, improving wetting, homogenizing the properties of the coating liquid in the pressurized coating chamber, and stabilizing the meniscus.

Description

Method for applying coating liquid to optical fiber

This application claims priority to dutch patent application No. 2019098 filed on 20.6.2017, which claims priority to U.S. provisional application serial No. 62/489,123 filed 24.4.2017, the contents of which are herein incorporated by reference in their entirety.

Technical Field

The present description relates to a method for coating an optical fiber. More particularly, the present description relates to a method of applying a coating liquid to an optical fiber.

Background

The transmission of light through an optical fiber is highly dependent on the nature of the coating applied to the optical fiber. The coating typically includes a primary coating and a secondary coating, wherein the secondary coating surrounds the primary coating and the primary coating contacts the glass waveguide (core + cladding) portion of the optical fiber. The secondary coating is a harder (higher young's modulus) material than the primary coating and is designed to protect the glass waveguide from damage caused by abrasion or external forces generated during processing and handling of the optical fiber. The primary coating is a softer (low young's modulus) material and is designed to buffer or dissipate stresses generated by forces applied to the outer surface of the secondary coating. Stress dissipation within the primary layer attenuates the stress and minimizes the stress reaching the glass waveguide. The primary coating is particularly important in dissipating the stresses generated when the fiber is bent. The bending stress of the glass waveguide transmitted to the optical fiber needs to be minimized because the bending stress causes local perturbations in the refractive index profile of the glass waveguide. Local refractive index perturbations can result in a loss of intensity of light transmitted through the waveguide. By dissipating the stress, the primary coating minimizes the strength loss induced by bending.

Coating liquids commonly used in optical fiber manufacturing are acrylate-based compositions that can be cured by exposure to heat or Ultraviolet (UV) light. The coating liquid is applied to the surface of the optical fiber in a liquid state and then exposed to heat or UV light for curing. The coating liquid may be spin coated in one or more layers, with a two-layer coating system (primary + secondary) often being the preferred embodiment. The primary coating is applied directly to the surface of the optical fiber and the secondary coating is applied over the primary coating.

In a typical optical fiber drawing process, an optical fiber is continuously drawn from a glass preform at a specific drawing speed. The glass preform comprises a central region having a desired core composition of the drawn optical fiber and one or more surrounding annular regions having a desired composition of one or more cladding regions of the drawn optical fiber. The preform is positioned in a draw furnace and heated sufficiently to soften the glass. Gravity or capstan-driven pulling forces act to extend the glass from the softened portion of the preform. As the glass extends, it thins and forms an optical fiber. The diameter of the optical fiber is controlled, the optical fiber is cooled, and then directed to a coating unit for applying one or more coating liquids. The coating liquid is cured to form a solid coating, and the coated optical fiber is then wound up and wound on a reel. The path that the fiber travels as it advances from the draw furnace to the spool is referred to as the process path.

There is a continuing need to reduce the cost of fiber manufacture by increasing draw speeds. However, as the draw speed increases, applying and curing the coating liquid becomes more difficult. In particular, it becomes more difficult to achieve a coating with a uniform thickness over the entire length and circumference of the optical fiber. Uniformity in coating thickness is required to facilitate splicing and bonding of coated optical fibers, and to attach a connector to the end of a coated optical fiber. There is a need for coating methods that allow the formation of coatings of uniform thickness on glass optical fibers in a continuous high speed drawing process.

Disclosure of Invention

A method of applying a coating liquid to an optical fiber is described. The fiber is drawn through a guide die into a coating chamber and through the coating chamber to a sizing die. The coating chamber contains a coating liquid. The method comprises the following steps: in the coating chamber, the coating liquid is guided in a direction transverse to the process path of the optical fiber. The lateral flow of the coating liquid counteracts the detrimental effects associated with the circulating currents that form in the coating chamber during the drawing process. Advantages of lateral flow include: the removal of bubbles, lowering the temperature of the circulating current, improving wetting, homogenizing the properties of the coating liquid in the coating chamber, and stabilizing the meniscus.

The present description extends to:

a method of processing an optical fiber, the method comprising the steps of:

drawing the optical fiber along a process path in a drawing direction through a coating chamber containing a coating liquid for coating the optical fiber, and

in a direction transverse to the draw direction, separate flows of coating liquid are directed through the coating chamber that are swept across, and/or swept around a process path in the draw direction to mix, dilute, or otherwise thermally or mechanically interact with the coating liquid contained in the coating chamber.

The present description extends to:

a method of processing an optical fiber, comprising:

drawing an optical fiber through a guide die at a draw speed to a pressurized coating chamber containing a first coating liquid;

forming a meniscus of the first coating liquid on the optical fiber in the pressurized coating chamber;

forming a boundary layer on the optical fiber in the pressurized coating chamber, the boundary layer including a first coating liquid and starting at the meniscus, a thickness of the boundary layer increasing with increasing distance from the guide die;

drawing the optical fiber through the pressurized coating chamber at the draw speed to a sizing die, the sizing die causing the boundary layer to contract, the contraction causing the first coating liquid to be expelled from the boundary layer into the pressurized coating chamber and form a circulating flow in the pressurized coating chamber, the circulating flow comprising the first coating liquid;

drawing the optical fiber through the sizing die at the draw speed, the optical fiber exiting the sizing die and having a surface layer of the first coating liquid; and

flowing the first coating liquid in the coating chamber in a transverse direction through a channel between the guide die and the sizing die.

The present description extends to:

a method of processing an optical fiber, the method comprising the steps of:

a separate flow (stream) or stream (flow) of coating liquid is guided through the coating chamber in a direction transverse to the drawing direction of the optical fiber through the coating chamber, wherein the transverse flow of coating liquid is swept across, swept over and/or swept around a process path in the drawing direction to mix, dilute or otherwise thermally or mechanically interact with the coating liquid contained in the coating chamber.

The present description extends to:

a system for processing an optical fiber, comprising:

one or more coating chambers for holding a coating liquid to coat the optical fiber, the coating chambers comprising an optical fiber inlet and an optical fiber outlet,

an inlet for delivering a flow or stream of coating liquid into the coating chamber,

an outlet for removing coating liquid from the coating chamber, the inlet and outlet being different from the optical fiber inlet and the optical fiber outlet, the inlet being configured for conveying a flow of coating liquid through the coating chamber in a direction transverse to the drawing direction of the optical fiber.

Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments as described in the written description and claims hereof, as well as the appended drawings.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and are intended to provide an overview or framework for understanding the nature and character of the claims.

The accompanying drawings are included to provide a further understanding, and are incorporated in and constitute a part of this specification. The drawings are illustrative of selected aspects of the specification and, together with the description, explain the principles and operations of the methods, products, and compositions contained in the specification. The features illustrated in the drawings are exemplary of selected embodiments of the present description and are not necessarily depicted to scale.

Drawings

While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter of the present written description, it is believed that the specification will be better understood from the following written description when taken in conjunction with the accompanying drawings, wherein:

FIG. 1 shows a calculated boundary layer of coating liquid on an optical fiber.

Fig. 2 shows a conventional design of a sizing die.

Fig. 3 shows a taper-only design of the sizing die.

Fig. 4 shows a calculated temperature distribution of the circulating current formed by the sizing die having the conventional design.

Fig. 5 shows a calculated temperature distribution of the circulating current formed by the sizing die having only the tapered design.

Fig. 6 shows the transverse flow of coating liquid in a coating chamber operatively connected to a sizing die of conventional design.

Fig. 7 shows the transverse flow of coating liquid in a pressurized coating chamber operatively connected to a sizing die having only a conical shape.

Fig. 8 shows the lateral flow of coating liquid through a channel in a pressurized coating chamber between a guide die and a sizing die.

FIG. 9 shows a coating unit having a pressurized coating chamber for applying a primary coating liquid and a secondary coating liquid to an optical fiber.

FIG. 10 shows a coating unit having a pressurized coating chamber for applying a primary coating liquid and a secondary coating liquid to an optical fiber.

The embodiments illustrated in the figures are exemplary in nature and are not intended to limit the scope of the detailed description or the claims. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like features.

Detailed Description

The present disclosure is provided as a teaching that can be implemented and can be more readily understood with reference to the following description, drawings, examples, claims. To this end, those skilled in the relevant art will recognize and appreciate that many changes can be made to the various aspects of the embodiments described herein, while still obtaining the beneficial results. It will also be apparent that some of the desired benefits of this embodiment can be obtained by selecting some of the features without utilizing other features. Accordingly, those who work in the art will recognize that many modifications and adaptations are possible and can even be desirable in certain circumstances and are a part of the present disclosure. Accordingly, it is to be understood that this disclosure is not limited to the particular compositions, articles, devices, and methods disclosed unless otherwise specified. It is also to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting.

The present description relates to methods and processes for forming optical fibers. In the continuous manufacturing of optical fibers, an optical fiber is drawn from a heated preform located in a draw furnace and passed through a series of processing stages. The processing stages typically include a metering unit for assessing the quality and other characteristics of the optical fiber (e.g., fiber diameter control), a heating stage, a cooling state, a primary coating stage, a secondary coating stage, an ink layer stage, one or more curing stages for curing a coating liquid or ink layer liquid applied to the optical fiber, and a winding or other winding stage for receiving and storing the coated optical fiber. The path followed by the fiber as it exits the draw furnace, passes through one or more process units to the winding stage is referred to herein as the process path of the fiber. The process path may be linear or may include turns.

The relative position of one process element with respect to another along the process path is referred to herein as upstream or downstream. The upstream direction of the process path is towards the preform and the downstream direction of the process path is towards the winding stage. Along the process path, a position or process cell upstream of the reference position or process cell is closer to the preform than the reference position or process cell. A process unit located closer to the draw furnace along the process path is said to be upstream of a process unit located further from the draw furnace along the process path. The draw furnace is upstream of all other process units and the take-up reel (or winding stage or other terminal unit) is downstream of all other process units. For example, in the illustrated drawing process, the process path of the optical fiber extends from the draw furnace to the cooling unit, from the cooling unit to the coating application unit, from the coating application unit to the coating curing unit, and from the coating curing unit to the take-up reel. In the context of the terminology used herein, the draw furnace is located upstream of the cooling unit, the cooling unit is located upstream of the paint application unit, the paint application unit is located upstream of the paint curing unit, and the paint curing unit is located upstream of the take-up reel. Similarly, the take-up reel is located downstream of the paint curing unit, which is located downstream of the paint application unit, which is located downstream of the cooling unit, which is located downstream of the draw furnace.

The present specification provides a method of applying a coating liquid to an optical fiber. The method is used to apply a coating liquid to a glass optical fiber, to apply a coating liquid to another coating liquid, or to apply a coating liquid to a cured coating. The method comprises the following steps: the optical fiber is guided along a process path, which includes passing the optical fiber through a coating application unit. The coating application unit includes a guide die, a pressurized coating chamber, and a finishing die. The pressurized coating chamber contains a coating liquid for coating the optical fiber. The guide die is located upstream of the pressurized coating chamber, which is located upstream of the sizing die. The fiber enters the pressurized coating chamber through the guide die, passes through the pressurized coating chamber to the sizing die, and passes through the sizing die to a downstream unit in the fiber drawing process.

The method enables a high drawing speed process for manufacturing an optical fiber. Drawing speed is currently limited by two problems: (1) it is difficult to wet the fiber with coating liquid as the fiber exits the guide die and enters the coating chamber; and (2) the severity of the effects associated with the circulating currents that form in the coating chamber near the sizing die increases as the optical fiber exits the coating chamber. The present method solves both problems and allows for increased drawing speed while minimizing coating defects. The drawing speeds available with the prior art methods are at least 30m/s, or at least 40m/s, or at least 50m/s, or at least 60m/s, or at least 70m/s, or in the range of 30m/s to 90m/s, or in the range of 40m/s to 80 m/s.

As the fiber exits the guide die and enters the coating chamber, it contacts the coating liquid. As the fiber wets, a meniscus of coating liquid forms on the fiber near the exit of the guided mode. The coating liquid is carried away by the optical fiber as it reaches the sizing die along the process path. The fiber exits the sizing die and it adheres to a layer of coating liquid, which is directed along a process path to a downstream process unit (e.g., another coating unit or a curing unit). The thickness of the coating liquid applied to the optical fiber is determined by the geometry of the sizing die, the viscosity of the coating liquid, the temperature of the optical fiber, and the draw speed. The diameter of the outlet of the sizing die is particularly important for establishing the thickness of the coating liquid applied to the optical fiber.

Successful coating and uniform coating thickness require that the optical fiber be effectively wetted by the coating liquid as it enters the coating chamber. When the fiber passes through the guide mode, the surrounding of the fiber is a gas (e.g., air, CO)₂He). As the fiber passes through the guided mode, a boundary layer of gas is formed on the surface of the fiber as the fiber moves through the gas environment. The gas boundary layer accompanies the fiber as it exits the guide die and enters the coating chamber.

Wetting is the process of replacing the gas boundary layer with the coating liquid as the optical fiber contacts and passes through the coating liquid. When the optical fiber is properly wetted with the coating liquid, a meniscus of the coating liquid is formed at the interface of the surface of the optical fiber and the coating liquid near the exit of the guide die, and a boundary layer of the coating liquid is formed on the optical fiber from the tip of the meniscus as the optical fiber is transported toward the exit of the sizing die.

If the coating liquid does not wet the fiber, a boundary layer of gas remains on the fiber. This results in gas being entrained into the coating chamber and gas being contained in the coating liquid. The presence of gas in the coating liquid causes the formation of bubbles in the coating liquid and the inclusion of bubbles in the coating liquid applied to the optical fiber. The bubbles destabilize the meniscus and lead to uneven coverage of the coating liquid on the fiber surface. When the coating liquid is solidified downstream of the sizing die, air bubbles remaining in the coating liquid adhering to the optical fiber remain in the coating. Bubbles in the cured coating constitute defects that impair the performance of the optical fiber and promote delamination of the cured coating. The presence of air bubbles in the coating chamber also makes it difficult to center and stabilize the position of the optical fiber as it passes through the coating application unit, which effect further leads to non-uniform coating thickness.

As the draw speed increases, the force required to displace the gas boundary layer increases. In the present method, a force sufficient to displace the gas boundary layer to enable wetting of the optical fiber at high draw speeds is achieved by pressurizing the coating chamber. By increasing the pressure of the coating liquid in the coating chamber, greater force can be achieved to apply the coating liquid to the optical fiber and keep the optical fiber wet at all times at the draw speeds disclosed herein. Pressurization of the coating chamber may be accomplished by equipping the coating chamber with a pressure sensor and using the pressure sensor to control the coating chamber pressure. In one embodiment, the flow of coating liquid delivered to the coating chamber is supplied by a pressurized source. By increasing the pressure of the coating chamber, the pressure of the coating liquid in the coating chamber is increased and as the draw speed increases, the pressure associated with the gas phase boundary layer can be overcome to achieve wetting.

As used herein, a pressurized coating chamber refers to a coating chamber having a pressure greater than 0 psig. In various embodiments, the pressure of the pressurized coating chamber is at least 0.10psig, or at least 0.50psig, or at least 1.0psig, or at least 5.0psig, or at least 10psig, or at least 25psig, or at least 50psig, or at least 100psig, or at least 200psig, or in the range of 0.10psig to 300psig, or in the range of 0.25psig to 275psig, or in the range of 0.50psig to 250psig, or in the range of 1.0psig to 225psig, or in the range of 5.0psig to 200psig, or in the range of 10psig to 175psig, or in the range of 25psig to 150psig, or in the range of 50psig to 100psig, where psig refers to psi (pounds per square inch gauge).

The higher pressure of the coating liquid in the pressurized coating chamber results in a higher meniscus pressure. A higher drawing speed is thus achieved by stabilizing the meniscus of the coating liquid with a high pressure. The meniscus pressure of the coating liquid provided by the present process is greater than 0psig, or at least 0.10psig, or at least 0.50psig, or at least 1.0psig, or at least 5.0psig, or at least 10psig, or at least 25psig, or at least 50psig, or at least 100psig, or at least 200psig, or in the range of 0.1psig to 500psig, or in the range of 1.0psig to 400psig, or in the range of 5.0psig to 300psig, or in the range of 10psig to 200 psig.

The measures taken to increase the meniscus pressure are complicated by the effects that the optical fiber has on leaving the coating chamber in the vicinity of the sizing die. As described above, when the wetted optical fiber moves from the guide die to the sizing die, a meniscus of the coating liquid is formed on the optical fiber, and a boundary layer of the coating liquid is formed at the tip of the meniscus. The boundary layer extends with the optical fiber as it passes through the coating liquid. FIG. 1 shows a calculated (finite element) boundary layer of coating liquid on an optical fiber as it passes through a coating chamber. Optical fiber 10 enters coating chamber 20 through guide die exit 30, passes through coating chamber 20 to sizing die 40 and exits through sizing die exit 50. The coating chamber 20 contains a coating liquid, and when the optical fiber 10 enters the coating chamber 20 through the guide mode exit 30, the optical fiber 10 is wetted with the coating liquid. For the purpose of the calculations, wetting of the fiber 10 involves complete displacement of the gas boundary layer associated with the fiber 10 in the guided mode by the coating liquid, and which occurs without the formation of bubbles in the coating chamber 20.

As the optical fiber 10 passes through the coating chamber 20, a boundary layer 60 of coating liquid is formed. As the optical fiber 10 travels toward the sizing die 40, the thickness of the boundary layer 60 increases. To a first order approximation, the thickness of the boundary layer is related to (vX/V)_f) Where V is the kinematic viscosity of the coating liquid, X is the distance of a location in the boundary layer along the path of the optical fiber relative to the starting point of the boundary layer at the tip of the meniscus proximate the exit of the guide mode, and V_fIs the drawing speed of the optical fiber.

Sizing die 40 includes a tapered surface 70 that constricts the space available for coating liquid. As the contraction occurs, a portion 80 of the coating fluid from boundary layer 60 is expelled from sizing die 40 back into coating chamber 20. The expelled coating fluid forms a loop in coating chamber 20 adjacent to finishing die 40. The circulation is a local loop pattern of coating liquid with nearly closed flow lines. During the drawing process, as the coating liquid circulates in the loop, the shear stresses associated with the flow cause the temperature of the coating liquid in the loop to increase.

The shape of the circulation and the temperature distribution in the circulation depends on the design of the sizing die. For example, the size and severity of the circulating flow depends on the degree of contraction of the space available for the coating liquid. For thinner fiber coatings, a narrower finishing mode is required, and therefore greater shrinkage occurs. The greater contraction results in a greater amount of coating liquid being expelled from the boundary layer as the fiber enters the tapered section of the sizing die and a more pronounced circulating flow is formed.

The shape of the sizing die also affects the location, shape and temperature distribution of the circulating current. Fig. 2 illustrates a conventional design of a sizing die. The conventional design includes a bell section, a tapered section, and a lower (land) section. Figure 3 shows a taper-only design of the sizing die. The cone-only design lacks a bell section, including a cone section and a lower section. Additional information regarding the taper-only design can be found in U.S. published patent application No. 20150147467a1, the disclosure of which is incorporated herein by reference.

Fig. 4 shows the calculated shape and temperature distribution of the circulating current formed near the sizing die having the conventional design shown in fig. 2. The optical fiber 110 enters the coating chamber section 120 through the guide die exit 130 and passes through the exit 150 of the conventional sizing die 140. The drawing speed of the optical fiber 110 was 50 m/s. A circular flow having an outer boundary 160 is formed around the optical fiber 110. The shading in the circulating current indicates the temperature distribution formed in the circulating current at the steady state. The darker shading corresponds to the higher temperature of the coating liquid present in the circulating flow. The temperature scale shown on the left indicates the temperature in degrees celsius. The temperature of the coating liquid is highest near the optical fiber 110 and decreases away from the optical fiber 110. The circulating flow is surrounded by the coating liquid. The boundary 160 of the circular flow corresponds to the point at which the temperature of the coating liquid in the circular flow and the temperature around the coating liquid come to equilibrium. For calculation purposes, the temperature of the coating liquid around the loop flow was set at 60 ℃. Fig. 4 shows that the process path along the optical fiber by the circulating current formed on a normal scale is long, and the spatial range of the circulating current is limited to a region close to the optical fiber. Figure 4 also shows that the maximum temperature in the loop is about 100 c higher than the temperature of the coating fluid away from the loop.

Fig. 5 shows the calculated shape and temperature distribution of the circulating current formed near the sizing die having the taper-only design shown in fig. 3. The optical fiber 210 enters the coating chamber section 220 through the guide die exit 230 and passes through the exit 250 of the sizing die 240, which is only tapered. A circulating current having an outer boundary 260 is formed around the optical fiber 210. The shading in the circulating current indicates the temperature distribution formed in the circulating current at the steady state. The temperature scale shown on the left indicates the temperature in degrees celsius. The darker shading corresponds to the higher temperature of the coating liquid present in the circulating flow. The temperature of the coating liquid is generally higher near the optical fiber 210 and decreases away from the optical fiber 210 until an equilibrium with the temperature surrounding the coating liquid occurs at the outer boundary 260 of the annular flow. For calculation purposes, the temperature of the coating liquid around the loop flow was set at 60 ℃. Fig. 5 shows that the circulating current formed by the tapered mode only is long in a direction transverse to the process path of the fiber. The circulating current formed by the tapered mode alone is less tightly confined to the space near the fiber, relative to a normal scale. The circulating current extends a significant distance in a lateral direction away from the process path. Figure 5 also shows that the maximum temperature in the loop is about 80 c higher than the temperature of the coating fluid away from the loop. For a sizing die with only a conical shape, the coating liquid in the loop is heated to a lesser extent than in the conventional sizing die shown in fig. 4.

The heating of the coating liquid occurring in the loop is detrimental to the stability of the meniscus and can result in flooding of the guide die. Flooding is a process failure in which the pressure of the coating liquid in the coating chamber forces the coating liquid through the guide die exit into the guide die. Flooding often results in fiber breakage and therefore requires a shutdown process. Due to the presence of the circulation, the probability of flooding becomes greater, since the viscosity of the coating liquid decreases as it is heated in the circulation. The reduction in viscosity and the degree of heating become more pronounced as draw speed increases, because higher draw speeds increase the circulation flow rate in the loop, which results in greater shear effects, and more heating due to viscous dissipation. For typical draw speeds of current manufacturing processes, the temperature rise (-70 ℃ and above) associated with circulation is sufficient to reduce the viscosity of the coating liquid by one or more orders of magnitude. As draw speeds increase above existing values, heating and thermal effects associated with circulating currents become more pronounced.

The heating and the reduction in viscosity of the coating liquid increases the likelihood of flooding because they (1) make the coating liquid more buoyant than the surrounding coating liquid, and (2) reduce the pressure required to cause the coating liquid to flow back into the guide die. As a result, if the higher temperature, less viscous coating liquid escapes from the loop and enters the surrounding coating liquid, it tends to flow upward in the coating chamber to the guide die. If the higher temperature, less viscous coating liquid reaches the meniscus, it destabilizes the meniscus and causes dewetting of the fiber. As the fiber dehumidifies, the liquid boundary layer-related drag forces required to inhibit backflow of the coating liquid into the guide die disappear, and the pressure required to force the coating liquid up through the guide die exit into the guide die becomes less. Therefore, flooding ensues.

Gas bubbles in the coating liquid also contribute to flooding. The presence of the gas bubbles causes the coating liquid in and around the circulating flow to move randomly and disorderly. This random, disordered movement promotes the escape of the higher temperature viscous coating liquid from the circulating flow and promotes the migration of the higher temperature viscous coating liquid towards the meniscus.

In order to maintain a stable meniscus and uninterrupted continuous wetting of the fiber, it is necessary to limit the effect of the circulating current on the coating process. The method mitigates the detrimental effects of circulation by supplying a transverse flow of coating liquid to the space between the outlet of the guide die and the inlet of the sizing die. Lateral flow refers to the flow of coating liquid in a direction transverse to the process path of the optical fiber as it passes through the coating chamber. The transverse direction refers to any direction that is not parallel to the process path of the optical fiber. The cross flow of coating liquid mixes or interacts with the coating fluid in the circulating flow. In one embodiment, the cross flow of coating liquid enters the loop, mixes with coating liquid in the loop, cross flows through the loop, exits from the loop, and removes or otherwise displaces a portion of the coating liquid in the loop. In another embodiment, the cross flow of coating liquid is directed around the loop without entering the loop. In one embodiment, establishing the cross flow comprises: adding coating liquid from an external source to existing coating liquid in the coating chamber, and removing coating liquid from the coating chamber. The coating liquid removed is the coating liquid originally present in the coating chamber, the coating liquid added to the coating chamber, or a combination thereof. In one embodiment, a transverse flow of coating liquid is supplied to a pressurized coating chamber.

The cross flow of the coating liquid mitigates the effects of the circulating flow in a number of ways. First, at the moment the cross flow enters the coating chamber, the temperature of the coating liquid in the cross flow can be controlled and maintained at a temperature lower than the maximum, average or minimum temperature of the coating fluid contained in the loop. The circular flow cools as the cross-flow cooler coating fluid interacts with the circular flow of hotter coating fluid. As the loop cools, the buoyancy of the coating liquid in the loop becomes less and the viscosity becomes stronger. This reduces the possibility of coating liquid escaping from the loop flow. If the coating liquid does escape from the loop, the reduced buoyancy, lower temperature and higher viscosity reduce the likelihood that the coating liquid from the loop will reach the meniscus. If the coating liquid from the circulating flow does reach the meniscus, the lower temperature and higher viscosity means that a higher pressure is required to force the coating liquid into the guide die. Therefore, the possibility of flooding becomes small. By maintaining a continuous transverse flow of coating liquid and continuously removing coating liquid, the temperature of the coating fluid in the loop can be managed.

Second, the cooling of the coating fluid provided by the cross flow also reduces the temperature gradient in the circulating flow and the difference between the average temperature of the circulating flow and the average temperature of the surrounding coating fluid. A higher temperature equilibrium results in a more uniform coating liquid with more stable and consistent properties (e.g. flow pattern, density, viscosity of the circulating flow). Better uniformity improves coating uniformity and concentricity.

Third, the displacement and removal of the coating liquid in the coating chamber, whether in or around the loop, reduces the bubble concentration in the coating chamber. The cross-flow of coating fluid is unaffected by the entrained gas in the coating chamber and enters the coating chamber substantially free of bubbles. Thus, the cross flow of the coating fluid dilutes the bubble concentration in the coating chamber. Removing the coating fluid containing bubbles of coating liquid from the coating chamber reduces the bubble concentration. The lower bubble concentration minimizes the likelihood of dewetting and flooding. The lower bubble concentration also eliminates random, chaotic motion in the annular flow, which results in better concentricity by having a more consistent stabilizing flow pattern in the annular flow and reduces the tendency of the coating fluid to escape from the annular flow.

Fourth, replenishing the coating liquid in the coating chamber reduces the concentration of dissolved gas in the coating fluid. As described above, the gas may enter the coating chamber by being entrained by the optical fiber as it exits the guide die. Entrainment can lead to dewetting and is undesirable. However, even when the fiber is properly wetted, gas can enter the coating chamber. Wetting of the optical fiber includes forming a meniscus of the coating liquid on the optical fiber as the optical fiber enters the coating liquid. When the meniscus forms, the gas boundary layer on the fiber is displaced. However, the meniscus is exposed to gas from the displaced boundary layer. Common process gases (e.g. air, CO) present in the guide die₂He) are soluble in coating liquids commonly used to coat optical fibers. As the drawing process runs over time, the concentration of gas dissolved in the coating liquid increases and eventually reaches a saturation level.

When the coating liquid is saturated with gas, two adverse effects occur. First, the dissolution of the gas into the coating liquid is one of the steps associated with the wetting process. The rate of wetting is related to the permeability of the gas from the gas boundary layer of the optical fiber into the coating liquid. (see, e.g., Jacqmin, D.; Journal of Fluid Mechanics,455,347-358 (2002)). Gas permeability is proportional to the solubility and diffusion rate of the gas in the coating liquid. If the coating liquid is saturated with gas, additional gas cannot be dissolved in the coating liquid, and gas from the gas boundary layer of the optical fiber cannot enter the coating liquid. As a result, dewetting may occur. Second, the inability of the gas to dissolve in the coating liquid increases the likelihood of bubble formation in the coating liquid. The dissolution of the gas in the coating liquid removes gas that may otherwise form bubbles in the coating liquid. By dissolution, bubble formation is suppressed. However, if the coating liquid becomes saturated with gas, it is no longer possible to dissolve, and it becomes more common for the gas to be contained in the form of bubbles into the coating liquid. Replenishing the saturated coating liquid with fresh coating liquid helps to wet and suppress bubble formation by avoiding saturation and keeping the gas always soluble in the coating liquid.

Fifth, the decrease in temperature of the coating liquid in the coating chamber increases the solubility of common process gases in the coating liquid. The higher solubility results in more dissolution of the gas in the coating liquid and longer times for saturation to occur. This allows for longer operating times before dewetting and bubble retention associated with saturation of the coating liquid occurs.

Establishing a cross-flow of the coating liquid comprises: a flow of coating liquid is directed into the space between the outlet of the guide die and the inlet of the sizing die. The space defines a channel through which the coating liquid flows in a transverse direction. The process path coincides with the optical fiber and extends from the exit of the guided mode to the entrance of the finishing mode. The cross-flow traverses, sweeps across, and/or sweeps around the process path to mix, dilute, remove, or otherwise interact (thermally or mechanically) with the coating liquid present in the coating chamber. The velocity of the cross flow is adjusted to counteract the adverse effects of the circulating flow. With increasing draw speed, larger cross-flow rates are preferred. In various embodiments, the velocity of the cross-flow is greater than 0.1cm³S, or more than 0.2cm³S, or more than 0.3cm³S, or more than 0.4cm³S, or more than 0.5cm³S, or more than 0.75cm³S, or more than 1.0cm³S, greater than 2.5cm³Or greater than 5.0cm³In/s, or in 0.1cm³/s-20cm³In the range of/s, or in the range of 0.1cm³/s-10cm³In the range of/s, or in the range of 0.1cm³/s–5.0cm³In the range of/s, or in the range of 0.2cm³/s-20cm³In the range of/s, or in the range of 0.2cm³/s-10cm³In the range of/s, or in the range of 0.2cm³/s–5.0cm³In the range of/s, or in the range of 0.5cm³/s-20cm³In the range of/s, or in the range of 0.5cm³/s-10cm³In the range of/s, or in the range of 0.5cm³/s–5.0cm³In the range of/s.

Fig. 6 shows a variation of the configuration shown in fig. 4, which includes a transverse flow of coating liquid in the channel between the guide die outlet 130 and the sizing die 140. The cross flow includes the introduction 170 of the coating liquid and the removal 180 of the coating liquid from the loop and/or coating chamber. Similarly, fig. 7 shows a variation of the configuration shown in fig. 5, which includes a transverse flow of coating liquid in the channel between the guide die outlet 230 and the sizing die 240. The cross flow includes the introduction 270 of the coating liquid and the removal 280 of the coating liquid from the loop and/or the coating chamber. In one embodiment, the lateral flow rate corresponds to the rate of coating liquid introduction at the coating chamber inlet. In another embodiment, the lateral flow rate corresponds to the rate of removal of the coating liquid from the coating chamber. In another embodiment, the lateral flow rate is measured by placing a sensor or flow meter in the coating chamber near the loop.

In various embodiments, the rate of introduction of the coating liquid for generating the cross-flow is greater than 0.1cm³S, or more than 0.2cm³S, or more than 0.3cm³S, or more than 0.4cm³S, or more than 0.5cm³S, or more than 0.75cm³S, or more than 1.0cm³S, greater than 2.5cm³S, or more than 5.0cm³In/s, or in 0.1cm³/s-20cm³In the range of/s, or in the range of 0.1cm³/s-10cm³In the range of/s, or in the range of 0.1cm³/s–5.0cm³In the range of/s, or in the range of 0.2cm³/s-20cm³In the range of/s, or in the range of 0.2cm³/s-10cm³In the range of/s, or in the range of 0.2cm³/s–5.0cm³In the range of/s, or in the range of 0.5cm³/s-20cm³In the range of/s, or in the range of 0.5cm³/s-10cm³In the range of/s, or in the range of 0.5cm³/s–5.0cm³In the range of/s.

In various embodiments, the rate of removal of coating liquid from the coating chamber is greater than 0.1cm³S, or more than 0.2cm³S, or more than 0.3cm³S, or more than 0.4cm³S, or more than 0.5cm³S, or more than 0.75cm³S, or more than 1.0cm³S, greater than 2.5cm³S, or more than 5.0cm³In/s, or in 0.1cm³/s-20cm³In the range of/s, or in the range of 0.1cm³/s-10cm³In the range of/s, or in the range of 0.1cm³/s–5.0cm³In the range of/s, or in the range of 0.2cm³/s-20cm³In the range of/s, or in the range of 0.2cm³/s-10cm³In the range of/s, or in the range of 0.2cm³/s–5.0cm³In the range of/s, or in the range of 0.5cm³/s-20cm³In the range of/s, or in the range of 0.5cm³/s-10cm³In the range of/s, or in the range of 0.5cm³/s–5.0cm³In the range of/s.

In one embodiment, to accommodate the cross flow of coating liquid, the coating chamber is adapted to include an inlet for delivering the cross flow of coating liquid and an outlet for removing the cross flow of coating liquid. The entrance and exit points are different from the entrance and exit points of the fiber into the coating chamber. Fig. 8 shows an embodiment of a coating chamber comprising an inlet for supplying coating liquid from an external source to the coating chamber and an outlet for removing coating liquid from the coating chamber. In fig. 8, the flow of the coating liquid is shown by grey arrows. The coating liquid flows from the inlet into the coating chamber and flows in a transverse direction through the optical fiber in a channel between the guide die and the sizing die. The coating liquid in the transverse flow leaves the channel and is removed from the coating chamber at the outlet. The inlet for supplying the coating liquid from an external source is different from the position where the optical fiber enters the coating chamber (guide die outlet). The outlet for removing the coating liquid from the coating chamber is different from the position where the optical fiber enters and leaves the sizing die. At steady state, the amount of coating liquid removed at the outlet is approximately equal to the amount of coating liquid supplied at the inlet. Since the coating liquid is removed in the form of a thin layer on the optical fiber at the sizing die and, if present, leaks into the guide die, an accurate balance of the amounts of coating liquid at the inlet and outlet does not occur.

In the embodiments of fig. 4 and 5, the circulating current occupies a large portion of the distance between the fiber entrance of the coating chamber and the fiber exit of the coating chamber.

As a result, as shown in FIG. 8, to facilitate mitigating the effects of circulating currents on fiber wetting, it is preferred that the coating liquid interact with a large portion of the circulating currents in a transverse flow. In fig. 8, the fiber entrance of the coating chamber corresponds to the exit of the guide die, and the fiber exit of the coating chamber corresponds to the entrance of the sizing die. In one embodiment, the interaction of the cross flow with the circulation is determined by the overlap of the cross section of the cross flow with the circulation. The cross flow is characterized by a cross section in a plane perpendicular to the direction of the cross flow. The cross-section is a two-dimensional area defined by a perimeter having a shape and size. The shape and size of the perimeter is affected by several factors, including the shape and size of the inlet that supplies the cross flow to the coating chamber and the size of the channel between the directing die and the sizing die through which the cross flow passes. In various embodiments, the shape of the perimeter is circular, elliptical, square, rectangular, or irregular. The dimension of the perimeter is characterized by a cross-sectional dimension. The cross-sectional dimension corresponds to the longest line segment connecting two points of the perimeter of the cross-section. For example, when the shape of the perimeter is circular, the cross-sectional dimension is a diameter. When the perimeter is square or rectangular in shape, the cross-sectional dimension is the diagonal length. When the shape of the perimeter is elliptical, the cross-sectional dimension is the length of the major axis of the ellipse.

In order to increase the interaction of the transverse flow of coating liquid with the circulating flow, the cross-sectional dimension of the transverse flow of coating liquid is more than 30% of the distance between the outlet of the guide die and the inlet of the sizing die, or more than 40% of the distance between the guide die outlet and the finishing die inlet, or more than 50% of the distance between the guide die outlet and the finishing die inlet, or more than 70% of the distance between the guide die outlet and the finishing die inlet, or more than 90% of the distance between the guide die outlet and the finishing die inlet, or 30-100% of the distance between the outlet of the guide die and the inlet of the finishing die, or 50% -100% of the distance between the outlet of the guide die and the inlet of the finishing die, or 70-100% of the distance between the outlet of the guide die and the inlet of the finishing die, or 30-90% of the distance between the guide die outlet and the finishing die inlet.

In other embodiments, the cross-sectional dimension of the transverse flow of coating liquid is greater than 30% of the distance between the fiber entrance of the coating chamber and the fiber exit of the coating chamber, or greater than 40% of the distance between the fiber entrance of the coating chamber and the fiber exit of the coating chamber, or greater than 50% of the distance between the fiber entrance of the coating chamber and the fiber exit of the coating chamber, or greater than 70% of the distance between the fiber entrance of the coating chamber and the fiber exit of the coating chamber, or greater than 90% of the distance between the fiber entrance of the coating chamber and the fiber exit of the coating chamber, or 30% -100% of the distance between the fiber entrance of the coating chamber and the fiber exit of the coating chamber, or 50% -100% of the distance between the fiber entrance of the coating chamber and the fiber exit of the coating chamber, or 70% -100% of the distance between the fiber entrance of the coating chamber and the fiber exit of the coating chamber, or 30% -90% of the distance between the fiber entrance of the coating chamber and the fiber exit of the coating chamber.

In one embodiment, the cross-sectional dimension of the transverse flow of coating liquid is controlled by the dimension of the inlet supplying the transverse flow of coating liquid to the coating chamber. The inlet includes an opening at an interface with the coating chamber through which a transverse flow of coating liquid is supplied. The cross-sectional area of the inlet is determined by the size and shape of the opening and is characterized by the cross-sectional dimension. The cross-sectional dimension of the inlet corresponds to the longest line segment connecting two points of the perimeter of the opening.

In various embodiments, the cross-sectional dimension of the inlet is greater than 30% of the distance between the fiber entrance of the coating chamber and the fiber exit of the coating chamber, or greater than 40% of the distance between the fiber entrance of the coating chamber and the fiber exit of the coating chamber, or greater than 50% of the distance between the fiber entrance of the coating chamber and the fiber exit of the coating chamber, or greater than 70% of the distance between the fiber entrance of the coating chamber and the fiber exit of the coating chamber, or greater than 90% of the distance between the fiber entrance of the coating chamber and the fiber exit of the coating chamber, or 30% -100% of the distance between the fiber entrance of the coating chamber and the fiber exit of the coating chamber, or 50% -100% of the distance between the fiber entrance of the coating chamber and the fiber exit of the coating chamber, or 70% -100% of the distance between the fiber entrance of the coating chamber and the fiber exit of the coating chamber, or 30% -90% of the distance between the fiber entrance of the coating chamber and the fiber exit of the coating chamber.

In various embodiments, the cross-sectional dimension of the inlet is greater than 30% of the distance between the guide die outlet and the sizing die inlet, or greater than 40% of the distance between the guide die outlet and the sizing die inlet, or greater than 50% of the distance between the guide die outlet and the sizing die inlet, or greater than 70% of the distance between the guide die outlet and the sizing die inlet, or greater than 90% of the distance between the guide die outlet and the sizing die inlet, or 30% to 100% of the distance between the guide die outlet and the sizing die inlet, or 50% to 100% of the distance between the guide die outlet and the sizing die inlet, or 70% to 100% of the distance between the guide die outlet and the sizing die inlet, or 30% to 90% of the distance between the guide die outlet and the sizing die inlet.

The temperature and/or flow rate of the coating liquid supplied at the inlet may be controlled to manage the thermal environment of the coating fluid in the coating chamber or in the loop. The temperature of the coating liquid supplied at the inlet is lower than the highest temperature of the coating liquid in the loop, or lower than the average temperature of the coating liquid in the loop, or lower than the lowest temperature of the coating liquid in the loop, or lower than the average temperature of the coating liquid in the coating chamber outside the loop.

Managing the thermal environment of the coating liquid includes minimizing the temperature differential of the coating liquid in the circulating stream. By including a cross flow of coating liquid in the passage between the guiding die and the sizing die, the difference between the highest temperature of the coating fluid in the loop and the lowest temperature of the coating fluid in the loop is less than 80 ℃, or less than 60 ℃, or less than 50 ℃, or less than 40 ℃, or less than 30 ℃.

In various embodiments, the temperature of the coating liquid supplied at the inlet of the coating chamber is at least 5 ℃, at least 10 ℃, or at least 20 ℃, or at least 30 ℃, or an amount from 5 ℃ to 40 ℃, or an amount from 10 ℃ to 30 ℃ lower than the average temperature of the coating fluid in the loop.

Managing the thermal environment of the coating liquid includes minimizing the difference between the temperature of the coating liquid in the loop and the temperature of the coating liquid around the loop. By including a cross flow of coating liquid in the passage between the guiding die and the sizing die, the difference between the maximum temperature of the coating fluid in the loop and the temperature of the coating fluid around the loop is less than 80 ℃, or less than 60 ℃, or less than 50 ℃, or less than 40 ℃, or less than 30 ℃.

Coating assemblies featuring lateral flow of coating liquids according to the present description are used to apply one or more coatings to optical fibers. A typical optical fiber includes a low mode primary coating on a glass optical fiber and a high mode secondary coating on the primary coating. A colored layer is also often formed on the secondary coating. The benefits associated with the lateral flow of coating liquid extend to any coating formed on the optical fiber. When applying multiple coatings to an optical fiber, the liquid primary coating composition is applied to the optical fiber at a location along the process path that is upstream of the location where the liquid secondary coating composition is applied to the optical fiber. In one embodiment, the liquid primary coating composition is cured before the liquid secondary coating composition is applied (wet-on-dry process). In another embodiment, the liquid primary coating composition is not cured prior to application of the liquid secondary coating composition (wet-on-wet process). If a liquid tint layer composition is applied, it is applied at a location along the process path downstream of the location at which the liquid secondary coating composition is applied. In one embodiment, the liquid secondary coating composition is cured prior to application of the liquid color layer composition (wet-on-dry process). In another embodiment, the liquid secondary coating composition is not cured prior to application of the liquid tint layer composition (wet-on-wet process).

FIG. 9 illustrates an embodiment of applying primary and secondary coating liquids to an optical fiber in a wet-on-wet process. The coating unit 300 is used to apply a liquid one-time coating composition to the optical fiber 305. The optical fiber 305 is drawn in the direction shown at a particular draw speed. The optical fiber 305 is drawn into a coating chamber 315 through a guide die 310, drawn into a sizing die 320 through the coating chamber 315, and drawn into a downstream coating unit 325 through the sizing die 320. In the coating chamber 315, a single coating liquid is applied to the optical fiber 305. The primary coating liquid is supplied to the coating chamber 315 at inlet 330 and removed from the coating chamber 315 at outlet 335. The primary coating liquid flows in the coating chamber 315 in the

transverse directions

340 and 345. The optical fiber 305 enters the coating unit 325 at the guide die 350, is drawn through the guide die 350 to the coating chamber 355, is drawn through the coating chamber 355 to the sizing die 360, and is drawn through the sizing die 360 to a downstream process unit (not shown). In the coating chamber 355, a secondary coating liquid is applied to the optical fiber 305. The coating chamber 355 is supplied with the secondary coating liquid at inlet 365 and the secondary coating liquid is removed from the coating chamber 355 at outlet 370. The secondary coating liquid flows in coating chamber 355 in

transverse directions

375 and 380. Although the cross-flow of coating liquid is depicted as occurring in the same or similar cross-direction in coating

chambers

315 and 355, it should be understood that the cross-flow of coating liquid may occur in different directions in

coating chambers

315 and 355.

FIG. 10 illustrates another embodiment of applying primary and secondary coating liquids to an optical fiber in a wet-on-wet process. The coating unit 400 is used to apply liquid primary and secondary coating compositions to the optical fiber 405. The fiber 405 is drawn in the direction shown at a particular draw speed. The optical fiber 405 is drawn into the coating chamber 415 through the guide die 410, into the mixing die 420 through the coating chamber 415, into the coating chamber 425 through the mixing die 420, into the sizing die 430 through the coating chamber 425, and into a downstream process unit (not shown) through the sizing die 430. The hybrid mode 420 acts as a finishing mode for the fiber 405 as the fiber 405 exits the coating chamber 415 and as a guided mode for the fiber 405 as the fiber 405 enters the coating chamber 425. In the coating chamber 415, a single coating liquid is applied to the optical fiber 405. The coating chamber 415 is supplied with the primary coating liquid at the inlet 435 and removed from the coating chamber 415 at the outlet 440. The primary coating liquid flows in the coating chamber 415 in the

transverse directions

445 and 450. Fiber 405 enters coating chamber 425 through a mixing die at 420. In coating chamber 425, a secondary coating liquid is applied to optical fiber 405. Secondary coating liquid is supplied to coating chamber 425 at inlet 455 and removed from coating chamber 425 at outlet 460. The secondary coating liquid flows in coating chamber 425 in

transverse directions

465 and 470. Although the cross-flow of coating liquid is depicted as occurring in the same or similar cross-direction in the coating chambers 415 and 425, it should be understood that the cross-flow of coating liquid may occur in different directions in the coating chambers 415 and 425.

In another embodiment, the coating liquid removed from the coating chamber is circulated to the coating chamber. The coating liquid removed from the coating chamber is directed to a return loop that delivers the removed coating liquid directly to the coating chamber or to an external source of coating liquid operatively connected to the inlet of the coating chamber.

In a preferred embodiment, the guide die is free of coating liquid. In another preferred embodiment, flooding of the guide die does not occur. In a further preferred embodiment, the coating liquid associated with the cross flow does not enter the guide die.

Preferred coating liquids are curable coating liquids. The curable coating liquid includes one or more curable components. As used herein, the term "curable" is intended to mean that when the component is exposed to a suitable source of curing energy, the component includes one or more curable functional groups capable of forming covalent bonds that participate in the attachment (bonding) of the component to itself or to other components to form a polymeric coating material. The cured product obtained by curing the curable coating liquid is a coating. The curing process is induced by any of a variety of forms of energy. The form of energy includes radiant energy or thermal energy. A radiation curable component is a component that can be induced to undergo a curing reaction when the component is exposed to radiation of a suitable wavelength at a suitable intensity for a sufficient time. The radiation curing reaction preferably takes place in the presence of a photoinitiator. Optionally, the radiation curable component is also thermally curable. Similarly, a thermally curable component is a component that can be induced to undergo a curing reaction when the component is exposed to thermal energy of sufficient intensity for a sufficient time. Optionally, the thermally curable component is also radiation curable. The curable component includes monomers, oligomers, and polymers.

The curable component includes one or more curable functional groups. The curable component having only one curable functional group is a monofunctional curable component. The curable component having two or more curable functional groups is a multifunctional curable component. The multifunctional curable component includes two or more functional groups capable of forming covalent bonds during the curing process, and may introduce cross-linking into the polymeric network formed during the curing process. The multifunctional curable component is also referred to as a "crosslinker" or "curable crosslinker". Examples of functional groups involved in the formation of covalent bonds during curing are identified below.

The coating composition includes a single monomer or a combination of monomers. The monomers include ethylenically unsaturated compounds, ethoxylated acrylates, ethoxylated alkylphenol monoacrylates, propylene oxide acrylates, n-propylene oxide acrylates, iso-propylene oxide acrylates, monofunctional aliphatic epoxy acrylates, multifunctional aliphatic epoxy acrylates and combinations thereof.

In one embodiment, the monomer component of the curable coating liquid includes an ethylenically unsaturated monomer. The monomers include functional groups as polymerizable groups and/or groups that promote or enable crosslinking. The monomer is a monofunctional monomer or a multifunctional monomer. In combinations having two or more monomers, the monomers of the composition are monofunctional monomers, multifunctional monomers, or a combination of monofunctional monomers and multifunctional monomers. Suitable functional groups of the ethylenically unsaturated monomers include, but are not limited to, (meth) acrylates, acrylamides, N-vinyl amides, styrenes, vinyl ethers, vinyl esters, acid esters, and combinations thereof.

Exemplary monofunctional ethylenically unsaturated monomers for the curable coating liquid include, but are not limited to, hydroxyalkyl acrylates such as 2-hydroxyethyl-acrylate, 2-hydroxypropyl-acrylate, and 2-hydroxybutyl acrylate; long and short chain alkyl acrylates, such as methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, pentyl acrylate, isobutyl acrylate, tert-butyl acrylate, pentyl acrylate, isopentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, isodecyl acrylate, undecyl acrylate, dodecyl acrylate, lauryl acrylate, stearyl acrylate, and stearyl acrylate; aminoalkyl acrylates, such as dimethylaminoethyl acrylate, diethylaminoethyl acrylate, and 7-amino-3, 7-dimethyloctyl acrylate; alkoxyalkyl acrylates, such as butoxyethyl acrylate, phenoxyethyl acrylate [ e.g., SR339 from Sartomer Company, Inc. ] and ethoxyethoxyethyl acrylate; monocyclic and polycyclic cyclic aromatic or non-aromatic acrylates, such as cyclohexyl acrylate, benzyl acrylate, dicyclopentadienyl acrylate, dicyclopentyl acrylate, tricyclodecanyl acrylate, bornyl acrylate (bomyl) ester, isobornyl acrylate (e.g. SR423 from sartomer), tetrahydrofurfuryl acrylate (e.g. SR285 from sartomer), caprolactone acrylate (e.g. SR495 from sartomer) and acryloyl morpholine; alcohol-based acrylates, such as polyethylene glycol monoacrylate, polypropylene glycol monoacrylate, methoxy ethylene glycol acrylate, methoxy polypropylene glycol acrylate, methoxy polyethylene glycol acrylate, ethoxy diethylene glycol acrylate, and various alkoxylated alkylphenol acrylates, such as ethoxylated (4) nonylphenol acrylate [ e.g., Photomer 4066 from IGM Resins (IGM Resins) ]; acrylamides such as diacetone acrylamide, isobutoxy methacrylamide, N' -dimethyl-aminopropyl acrylamide, N-dimethylacrylamide, N-diethylacrylamide and tert-octylacrylamide; vinyl compounds such as N-vinylpyrrolidone and N-vinylcaprolactam; and acidic esters such as maleic acid esters and fumaric acid esters. For the long and short chain alkyl acrylates listed above, the short chain alkyl acrylate is an alkyl group having 6 or less carbons and the long chain alkyl acrylate is an alkyl group having 7 or more carbons.

Representative radiation curable ethylenically unsaturated monomers include alkoxylated monomers having one or more acrylate or methacrylate groups. Alkoxylated monomers are monomers comprising one or more alkyleneoxy groups, wherein the alkyleneoxy groups have the form-O-R-and R is a straight or branched chain hydrocarbon. Examples of alkyleneoxy groups include ethyleneoxy (-O-CH)₂-CH₂-) n-propylidene (-O-CH)₂-CH₂-CH₂-) isopropylidene (-O-CH)₂-CH(CH₃) -) and the like. The degree of alkoxylation as used herein refers to the number of alkyleneoxy groups in the monomer. In one embodiment, the alkyleneoxy groups are continuously bonded in the monomer.

Representative polyfunctional ethylenically unsaturated monomers for the curable coating liquid include, but are not limited to, alkoxylated bisphenol a diacrylates, such as ethoxylated bisphenol a diacrylates, having a degree of alkoxylation of 2 or greater. The monomer component of the secondary composition may include ethoxylated bisphenol a diacrylate having a degree of ethoxylation of from 2 to about 30 (e.g., SR349 and SR601 available from sartomer, west chester, pa and Photomer 4025 and Photomer 4028 available from IGM resins), or a propoxylated bisphenol a diacrylate having a degree of propoxylation of 2 or greater, e.g., from 2 to about 30; alkoxylated and non-alkoxylated methylol propane polyacrylates such as ethoxylated trimethylolpropane triacrylate having a degree of ethoxylation of 3 or greater, for example, 3 to about 30 (e.g., Photomer 4149 by IGM resins and SR499 by sandoma); propoxylated trimethylolpropane triacrylate having a degree of propoxylation of 3 or more, for example 3 to 30 (e.g., Photomer 4072 from IGM resin and SR492 from sartomer); ditrimethylolpropane tetraacrylate (e.g., Photomer 4355 from IGM resins); alkoxylated glyceryl triacrylates, e.g., propoxylated glyceryl triacrylates having a degree of propoxylation of 3 or greater (e.g., Photomer 4096 from IGM and SR9020 from sartomer); alkoxylated and non-alkoxylated erythritol polyacrylates such as pentaerythritol tetraacrylate (e.g., SR295 available from sartomer, west chester, pennsylvania), ethoxylated pentaerythritol tetraacrylate (e.g., SR494 from sartomer), and dipentaerythritol pentaacrylate (e.g., Photomer 4399 from IGM resins and SR399 from sartomer); isocyanurate polyacrylates formed by reacting a suitable functional isocyanurate with acrylic acid or acryloyl chloride, such as tris- (2-hydroxyethyl) isocyanurate triacrylate (e.g., SR368 from sartomer company) and tris- (2-hydroxyethyl) isocyanurate diacrylate; alkoxylated and non-alkoxylated alcohol polyacrylates such as tricyclodecane dimethanol diacrylate (e.g., CD406 from sartomer company) and ethoxylated polyethylene glycol diacrylate having a degree of ethoxylation of 2 or greater, e.g., about 2 to 30; epoxy acrylate formed by adding acrylate to bisphenol a diglycidyl ether or the like (for example, Photomer 3016 from IGM resins); and monocyclic and polycyclic cyclic aromatic or non-aromatic polyacrylates such as dicyclopentadiene diacrylate and dicyclopentane diacrylate.

In an embodiment, the monomer component of the coating liquid comprises a monomer having the general formula R₂—R₁—O—(CH₂CH₃CH—O)_q—COCH＝CH₂Wherein R is₁And R₂Is aliphatic, aromatic or a mixture of the two, and q is 1 to 10; or comprises a compound having the formula R₁—O—(CH₂CH₃CH—O)_q—COCH＝CH₂Wherein R is₁Is aliphatic or aromatic and q is 1 to 10. Representative examples include: ethylenically unsaturated monomers, for example lauryl acrylate (e.g. SR335 from Sadoma, AGEFLEX FA12 from BASF and AGEFLEX FA12 from BASF)PHOTOMER 4812 from IGM RESIN, ethoxylated nonylphenol acrylate (e.g., SR504 from Saedoma and PHOTOMER 4066 from IGM RESIN), caprolactone acrylate (e.g., SR495 from Saedoma and TONE M-100 from Dow Chemical), phenoxyethyl acrylate (e.g., SR339 from Saedoma, AGEFLEX PEA from Pasteur, and PHOTOMER 4035 from IGM RESIN), isooctyl acrylate (e.g., SR440 from Saedoma and AGEFLEX FA8 from Pasteur), tridecyl acrylate (e.g., SR489 from Saedoma), isobornyl acrylate (e.g., SR506 from Saedoma and EBEX OA from CPS (CPS Co.), tetrahydroxy acrylate (e.g., SR285 from Saedoma), stearyl acrylate (e.g., SR257 from Saedoma), and stearyl acrylate (e.g., SR285 from Saedoma), Isodecyl acrylate (e.g., SR395 from Saedoma and AGEFLEX FA10 from Pasteur), 2- (2-ethoxyethoxy) ethyl acrylate (e.g., SR256 from Saedoma), epoxy acrylate (e.g., CN120 from Saedoma and EBECRYL 3201 and 3604 from Setec Industries, Inc.), lauryl glycidyl acrylate (e.g., CN130 from Saedoma) and phenoxy glycidyl acrylate (e.g., CN131 from Saedoma), and combinations thereof.

In some embodiments, the monomer component of the coating liquid comprises a multifunctional (meth) acrylate. As used herein, the term "(meth) acrylate" means an acrylate or methacrylate. A multifunctional (meth) acrylate is a (meth) acrylate having two or more polymerizable (meth) acrylate moieties per molecule, or three or more polymerizable (meth) acrylate moieties per molecule. Examples of multifunctional (meth) acrylates include dipentaerythritol monohydroxypentaacrylate (e.g., PHOTOMER 4399 available from IGM resins, Inc.); alkoxylated and non-alkoxylated methylol propane polyacrylates such as trimethylolpropane triacrylate, ditrimethylolpropane tetraacrylate (e.g., PHOTOMER 4355 from IGM resins); alkoxylated glycerol triacrylates, e.g., propoxylated glycerol triacrylates having a degree of propoxylation of 3 or greater (e.g., PHOTOMER 4096 from IGM resins, Inc.); and alkoxylated and non-alkoxylated erythritol polyacrylates such as pentaerythritol tetraacrylate (e.g., SR295 available from sartomer company (west chester, pa)); ethoxylated pentaerythritol tetraacrylate (e.g., SR494 from sartomer company); dipentaerythritol pentaacrylate (e.g., PHOTOMER 4399 available from IGM resins and SR399 from Saedoma); tripropylene glycol di (meth) acrylate; propoxylated hexanediol di (meth) acrylate; tetrapropylene glycol di (meth) acrylate; pentapropylene glycol di (meth) acrylate.

In one embodiment, the monomer component of the coating liquid comprises an N-vinylamide, such as N-vinyllactam or N-vinylpyrrolidone or N-vinylcaprolactam.

The curable coating liquid optionally includes one or more oligomers. One type of optional oligomer is an ethylenically unsaturated oligomer. Suitable optional oligomers include monofunctional oligomers, multifunctional oligomers, or a combination of monofunctional and multifunctional oligomers. In some embodiments, the optional oligomers include aliphatic and aromatic urethane (meth) acrylate oligomers, urea (meth) acrylate oligomers, polyester and polyether (meth) acrylate oligomers, acrylated acrylic oligomers, polybutadiene (meth) acrylate oligomers, polycarbonate (meth) acrylate oligomers, and melamine (meth) acrylate oligomers, or combinations thereof. The curable coating liquid may be free of urethane groups, groups that react to form urethane groups, urethane acrylate compounds, urethane oligomers, or urethane acrylate oligomers.

The polymerization initiator facilitates initiation of a polymerization process associated with curing of the coating composition to form a coating. Polymerization initiators include thermal initiators, chemical initiators, electron beam initiators, and photoinitiators. The photoinitiator includes a ketone photoinitiating additive and/or a phosphine oxide additive. When used in the photo-formation of coatings of the present disclosure, the photoinitiator is present in an amount sufficient to effect rapid radiation cure. The wavelength of the curing radiation is an infrared, visible or ultraviolet wavelength.

Representative photoinitiators include 1-hydroxycyclohexyl phenyl ketone (e.g., IRGACURE 184 available from basf); bis (2, 6-dimethoxybenzoyl) -2,4, 4-trimethylpentylphosphine oxide (e.g., a commercial blend of IRGACURE 1800, 1850 and 1700 available from basf); 2, 2-dimethoxy-2-phenylacetophenone (e.g., IRGACURE 651 from basf); bis (2,4, 6-trimethylbenzoyl) -phenylphosphine oxide (IRGACURE 819); (2,4, 6-trimethylbenzoyl) diphenylphosphine oxide (LUCIRIN TPO available from BASF corporation (Munich, Germany)); ethoxy (2,4, 6-trimethylbenzoyl) -phenylphosphine oxide (LUCIRIN TPO-L from Pasteur); (2,4, 6-triethylbenzoyl) diphenylphosphine oxide (e.g., Darocur 4265, a commercial blend from basf); 2-hydroxy-2-methyl-1-phenylpropan-1-one (e.g., Darocur 4265, a commercial blend from basf corporation) and combinations thereof.

In addition to the monomeric, oligomeric, and/or oligomeric material, and the polymerization initiator, the coating composition optionally includes one or more additives. Additives include adhesion promoters, strength additives, antioxidants, catalysts, stabilizers, optical brighteners, property enhancing additives, amine synergists, waxes, lubricants, and/or slip agents.

Embodiments of the method include curing the coating liquid on the optical fiber. In one embodiment, the curable coating liquid is cured with an LED or laser source. In one embodiment, the LED source is a UVLED source. The peak wavelength of the LED or laser source is a wavelength less than 410nm, or less than 405nm, or less than 400nm, or less than 395nm, or in the range of 340 nm-410 nm, or in the range of 350 nm-405 nm, or in the range of 360 nm-405 nm, or in the range of 365 nm-400 nm, or in the range of 370 nm-395 nm, or in the range of 375 nm-390 nm, or in the range of 375 nm-400 nm, or in the range of 380 nm-400 nm.

Representative radiation curable ethylenically unsaturated monomers include monomers having one or more acrylates or methacrylatesAn alkoxylated monomer of methacrylate groups. Alkoxylated monomers are monomers comprising one or more alkyleneoxy groups, wherein the alkyleneoxy groups have the form-O-R-and R is a straight or branched chain hydrocarbon. Examples of alkyleneoxy groups include ethyleneoxy (-O-CH)₂-CH₂-) n-propylidene (-O-CH)₂-CH₂-CH₂-) isopropylidene (-O-CH)₂-CH(CH₃) -) and the like. The degree of alkoxylation as used herein refers to the number of alkyleneoxy groups in the monomer. In one embodiment, the alkyleneoxy groups are continuously bonded in the monomer. Reference is made to the description of the secondary coating of ID 27449.

Unless otherwise stated, it is not intended that any method described herein be construed as requiring that its steps be performed in a particular order. Thus, where a method claim does not actually recite an order to be followed by its steps or it does not otherwise specifically imply that the steps are to be limited to a specific order in the claims or specification, it is not intended that any particular order be implied.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the illustrated embodiments. Since numerous modifications, combinations, sub-combinations and variations of the disclosed embodiments can be made by those skilled in the art in light of the spirit and scope of the exemplary embodiments, it is intended that the present disclosure include all modifications and equivalents within the scope of the appended claims.

Claims

1. A method of processing an optical fiber (10,110,210,288,305,405), the method comprising the steps of:

drawing an optical fiber (10,110,210,288,305,405) along a process path in a draw direction through a coating chamber (20,120,220,315,415) containing a coating liquid for coating the optical fiber (10,110,210,288,305,405), and

directing a separate flow (170,180,270,280,340,345,445,450) of coating liquid through the coating in a direction transverse to a draw direction of the optical fiber (10,110,210,288,305,405) through the coating chamber (20,120,220,315,415)A cover chamber (20,120,220,315,415), the transverse flow of coating liquid (170,180,270,280,340,345,445,450) sweeping across the process path in the draw direction and sweeping across the process path in the draw direction to mix and dilute the coating liquid contained in the coating chamber (20,120,220,315,415), wherein the transverse flow of coating liquid is greater than 0.1cm in the transverse direction³The flow rate of the gas/s is such that,

wherein a lateral flow (170,180,270,280,340,345,445,450) of the individual coating liquids is introduced (170,270,340,445) into the coating chamber (20,120,220,315,415) at an inlet (330,435), and wherein the lateral flow (170,180,270,280,340,345,445,450) of the individual coating liquids is removed from the coating chamber (20,120,220,315,415) at an outlet (335,440) opposite the inlet (330,435).

2. The method of claim 1, wherein the laterally flowing coating liquid is greater than 0.2cm in a lateral direction³The velocity of flow/s.

3. The method of claim 1, wherein the laterally flowing coating liquid is greater than 0.5cm in a lateral direction³The velocity of flow/s.

4. The method of claim 1, wherein the laterally flowing coating liquid is at 0.1cm in a lateral direction³/s-20cm³Flow at a rate in the range of/s.

5. The method of claim 1, wherein the laterally flowing coating liquid is at 0.2cm in the lateral direction³/s-20cm³Flow at a rate in the range of/s.

6. The method of claim 1, wherein the laterally flowing coating liquid is at 0.5cm in the lateral direction³/s-20cm³Flow at a rate in the range of/s.

7. The method of claim 1, wherein the coating chamber (20,120,220,315,415) is pressurized, wherein the pressurized coating chamber has a pressure greater than 1.01 bar.

8. The method of claim 7, wherein the pressurized coating chamber has a pressure of at least 1.02 bar.

9. The method of claim 7, wherein the pressurized coating chamber has a pressure of at least 1.08 bar.

10. The method of claim 7, wherein the pressurized coating chamber has a pressure of at least 1.36 bar.

11. The method of claim 7, wherein the pressurized coating chamber has a pressure of at least 1.70 bar.

12. The method of claim 7, wherein the pressurized coating chamber has a pressure in the range of 1.02 bar to 21.70 bar.

13. The method of claim 7, wherein the pressurized coating chamber has a pressure in the range of 1.08 bar to 16.53 bar.

14. The method of claim 7, wherein the pressurized coating chamber has a pressure in the range of 1.36 bar to 14.80 bar.

15. The method of claim 1, wherein the optical fiber (10,110,210,288,305,405) enters the coating chamber (20,120,220,315,415) through a guide die (284,310,410), and/or wherein the optical fiber (10,110,210,288,305,405) is drawn through the coating chamber (20,120,220,315,415) to a sizing die (40,140,240,286,320).

16. The method of claim 1, wherein the coating liquid flowing through the coating chamber (20,120,220,315,415) in a direction transverse to a draw direction of the optical fiber (10,110,210,288,305,405) is directed through a transverse guide channel in the coating chamber (20,120,220,315,415) between the guide die (284,310,410) and the sizing die (40,140,240,286,320).

17. The method of claim 16, wherein the sizing die (40,140,240,286,320) comprises a taper-only die including a taper section (96) and a lower section (98), the taper-only die lacking a bell section.

18. The method of any of claims 15 to 17, wherein the guide die (284,310,410) comprises a bell section, a tapered section, and a lower section, or wherein the guide die (284,310,410) comprises a taper-only die comprising a taper section and a lower section, the taper-only die lacking a bell section.

19. The method of any of claims 1 to 17, wherein the optical fiber (10,110,210,288,305,405) is drawn at a draw speed of at least 30 m/s.

20. The method of claim 19, wherein the draw speed is at least 40 m/s.

21. The method of claim 19, wherein the draw speed is at least 50 m/s.

22. The method of claim 19, wherein the draw speed is in the range of 40m/s-80 m/s.

23. The method of any of claims 1 to 17, further comprising curing the coating liquid after the optical fiber (10,110,210,288,305,405) exits the sizing die (40,140,240,286,320).

24. The method of claim 23, wherein the curing is accomplished with an LED source.

25. The method of any of claims 1 to 17, wherein the lateral flow of coating liquid is directed for a loop flow comprising coating liquid, the loop flow being formed around the optical fiber (10,110,210,288,305,405) in a coating chamber (20,120,220,315,415).

26. The method of claim 25, wherein the difference between the maximum temperature of the coating liquid in the loop and the minimum temperature of the coating liquid in the loop is less than 80 ℃.

27. The method of claim 25, wherein the difference between the maximum temperature of the coating liquid in the loop and the minimum temperature of the coating liquid in the loop is less than 60 ℃.

28. The method of claim 25, wherein the laterally flowing coating liquid is mixed with the circulating coating liquid.

29. The method of claim 15, wherein an outlet (335,440) is spaced apart from the guide die (284,310,410) and the sizing die (40,140,240,286,320).

30. The method of claim 29, wherein an amount of coating liquid substantially equal to the amount of coating liquid supplied to the inlet (330,435) of the coating chamber (20,120,220,315,415) is removed from the coating chamber (20,120,220,315,415) at the outlet (335,440).

31. The method of claim 29, further comprising: the coating liquid removed at the outlet (335,440) is returned to the coating chamber (20,120,220,315,415).

32. The method of claim 25, wherein the temperature of the coating fluid supplied at the inlet (330,435) is lower than the average temperature of the coating liquid in the loop.

33. The method of claim 32, wherein the temperature of the coating fluid at the inlet (330,435) is at least 5 ℃ lower than the average temperature of the first coating liquid in the loop.

34. The method of claim 29, wherein the distance is greater than 0.1cm³The rate of/s introduces coating liquid at the inlet (330,435) and/or removes coating liquid from the outlet (335,440).

35. The method of claim 34, wherein the rate is greater than 0.2cm³/s。

36. The method of claim 34, wherein the rate is greater than 0.5cm³/s。

37. The method of claim 34, wherein the rate is at 0.1cm³/s-20cm³In the range of/s.

38. The method of claim 1, further comprising drawing the optical fiber (10,110,210,288,305,405) through a second coating chamber (355,425) containing a second coating liquid.

39. The method of claim 38, further comprising: directing a separate flow of a second coating liquid through a second coating chamber in a direction transverse to a draw direction of the optical fiber through the second coating chamber, the transverse flow of the second coating liquid sweeping across a process path in the draw direction and sweeping across the process path in the draw direction to mix and dilute the second coating liquid contained in the second coating chamber, wherein the transverse flow of the second coating liquid is greater than 0.1cm in the transverse direction³The flow rate of the gas/s is such that,

wherein the lateral flow of the individual second coating liquid is introduced into the second coating chamber at an inlet, and wherein the lateral flow of the individual second coating liquid is removed from the second coating chamber at an outlet opposite the inlet.

40. A system for processing an optical fiber (10,110,210,288,305,405), comprising:

one or more coating chambers (20,120,220,315,415,355,425) for holding a coating liquid to coat an optical fiber (10,110,210,288,305,405), the optical fiber (10,110,210,288,305,405) being drawable through the coating chamber (20,120,220,315,415,355,425) along a process path in a draw direction, the coating chamber (20,120,220,315,415,355,425) including a fiber inlet and a fiber outlet;

an inlet (330,435,365,455) for delivering a flow of coating liquid into the coating chamber (20,120,220,315,415,355,425); and

an outlet (335,440,370,460) for removing coating liquid from the coating chamber (20,120,220,315,415,355,425), the inlet (330,435,365,455) and outlet (335,440,370,460) being different from the optical fiber inlet and outlet, the inlet (330,435,365,455) being configured for removal at greater than 0.1cm³A velocity of/s to convey a flow of coating liquid through the coating chamber (20,120,220,315,415,355,425) in a direction transverse to a draw direction of the optical fiber (10,110,210,288,305,405) and through the process path in the draw direction,

the outlet (335,440) is opposite the inlet (330,435).

41. The system of claim 40, wherein the velocity is greater than 0.2cm³/s。

42. The system of claim 40, wherein the velocity is greater than 0.5cm³/s。

43. The system of claim 40, wherein the velocity is at 0.1cm³/s-20cm³In the range of/s.

44. The system of claim 40, wherein the velocity is at 0.2cm³/s-20cm³In the range of/s.

45. As claimed in claim40, wherein the velocity is at 0.5cm³/s-20cm³In the range of/s.