JP2003240977A - Method for manufacturing plastic optical member and plastic optical member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing by which a plastic optical member having high performance can be stably manufactured with high productivity. <P>SOLUTION: The method for manufacturing a plastic optical member comprising a core part and a clad part includes a process of charging a container with a composition comprising a monomer and a polymer of the monomer and polymerizing the monomer while rotating the container to form the clad part. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technical field of a plastic optical member and a method of manufacturing the same, and more particularly to a technical field of a plastic optical member and a method of manufacturing the same which are preferably used for manufacturing a gradient index plastic optical transmission body. Belong to

[0002]

2. Description of the Related Art A plastic optical member has advantages that it is easy to manufacture and process, and that it is inexpensive, as compared with a quartz optical member having the same structure.
In recent years, various applications such as optical fibers and optical lenses have been tried. In particular, the plastic optical fiber has a disadvantage that the transmission loss is slightly larger than that of the silica type because all the strands are made of plastic, but
It has good flexibility, light weight, good workability, is easy to manufacture as a fiber having a large diameter as compared with a silica-based optical fiber, and can be manufactured at low cost. Therefore, various studies have been made as an optical communication transmission medium for short distances where the magnitude of transmission loss does not matter.

A plastic optical member generally has a different refractive index (generally low) from a core (referred to as "core part" in this specification) made of an organic compound having a polymer as a matrix. An outer shell made of an organic compound (having a refractive index) (referred to as a “clad portion” in the present specification). In particular, a gradient index plastic optical fiber having a core portion having a refractive index distribution from the center to the outside is capable of widening the band of an optical signal to be transmitted, and thus has a high transmission capacity. Has been attracting attention recently. An optical member base material (referred to as "preform" in the present specification) is produced by utilizing an interfacial gel polymerization method as one of the methods for producing the gradient index plastic optical member, and then the preform is prepared. There is a method of stretching. In this manufacturing method, first, a monomer such as methyl methacrylate (MMA) is put in a container having sufficient rigidity, and while the container is rotated, the monomer is polymerized,
A cylindrical tube made of a polymer such as polymethacrylate (PMMA) is prepared. The cylindrical tube serves as a clad portion.

Next, a core portion having a refractive index distribution is formed in the hollow portion of the cylindrical tube. As a method of imparting a refractive index distribution to the core portion, for example, in Japanese Patent Laid-Open No. 2-16504, a method of concentrically extruding a laminate of two or more kinds of polymerizable mixtures having different refractive index distributions is formed. Is disclosed. As a method for obtaining a preform by polymerization, JP-A-5-181023 and JP-A 6-1 are available.
Japanese Patent Publication No. 94530 discloses a method of heating polymerization while dropping a mixture containing a monomer capable of forming a core portion having a refractive index different from that of a polymer forming the cladding portion, a polymerization initiator and the like into the cladding portion made of a polymer. In International Publication WO93 / 08488, a cylindrical tube made of a polymer is charged with a mixture of a monomer, a polymerizable refractive index raising agent, and a polymerization initiator, followed by heat polymerization to form a core part. A method in which the refractive index distribution is produced by the concentration distribution of the refractive index adjusting agent contained in the core portion; and JP-A-4-9730, there is disclosed a compounding ratio of polymers having different refractive indexes. Is disclosed; a method of continuously varying is disclosed. The preform thus obtained is subjected to 180 ° C.
A gradient index plastic optical fiber is obtained by hot drawing in an atmosphere of about 250 ° C.

[0005]

By the way, in the case of producing a cylindrical tube to be the clad part, when the monomer is rapidly polymerized, the heat generated by the polymerization causes a foaming phenomenon and the inner surface of the clad part becomes uneven. Or, there is a problem that fluctuation occurs on the inner surface. The problem of heat generation at the time of producing the clad portion is particularly remarkable in the case of producing a large-diameter plastic optical member, which is one of the causes of adverse effects in mass production of the plastic optical member.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a manufacturing method capable of stably manufacturing a plastic optical member having good performance with high productivity.

[0007]

In order to solve the above problems, a method for producing a plastic optical member of the present invention is a method for producing a plastic optical member comprising a core portion and a clad portion, wherein a monomer and a monomer It is characterized by including a polymerization step of polymerizing the monomer while rotating a container containing a composition containing the coalescence to form a clad portion.

In the manufacturing method of the present invention, a container containing a monomer is polymerized while being rotated (hereinafter referred to as "rotational polymerization") to produce a clad portion. In the present invention, a composition containing a monomer and a polymer of the monomer is used as the raw material of the clad portion. When the composition is placed in a container and rotated, the monomer permeates the polymer of the monomer,
Swell the polymer. Further, the monomer that has not penetrated into the polymer exists inside the container due to the centrifugal force, and the polymer of the monomer swollen by the monomer exists outside the container due to the centrifugal force.
When polymerization is started in this state, in the clad portion formed, the inner main component is a polymer generated by polymerization of the monomer, and the outer main component is a polymer of the monomer contained in the composition. Be united. Therefore, in the present invention, since a part of the clad part (outer part) can be constituted by the polymer contained in the composition used as a raw material, it is possible to reduce the amount of monomers to be polymerized during the formation of the clad part, The heat generated by the polymerization reaction can be suppressed. As a result, it is possible to reduce the unevenness of the inner surface of the clad portion due to the heat of polymerization, or reduce the fluctuations that occur on the inner surface, and it is possible to stably manufacture a plastic optical member having good performance, and to improve productivity, especially Contributes to improved productivity during mass production.

As one aspect of the present invention, after the composition is charged into the container, the container is rotated for 1 hour or more,
A method for producing the plastic optical member, which comprises swelling a polymer of the monomer with the monomer, and then polymerizing the monomer; the clad portion formed in the polymerizing step is further outward There is provided a method for producing a plastic optical member, characterized in that it mainly contains a polymer of the monomer, and further mainly contains a polymer generated by polymerization of the monomer.

As a preferred embodiment of the present invention, the above-mentioned composition contains at least 30% by mass or more of a polymer of the above monomer with respect to the total mass of the composition, and the above-mentioned method for producing a plastic optical member. The composition contains a polymerization initiator having a 10-hour half-life temperature (t _1/2 ° C) that is not higher than the boiling point of the monomer, and the monomer is {(t _1/2 ) -20} in the polymerization step. A method for producing the above-mentioned plastic optical member, which comprises polymerizing with the above-mentioned polymerization initiator at a temperature of not less than 0 ° C and not more than (t _1/2 ° C); the amount average degree of polymerization of the polymer of the monomer contained in the composition is 40
0 to 1200, the method for producing the plastic optical member, wherein the composition contains a polymerization regulator,
In the polymerization step, the molecular weight of the polymer produced by the polymerization of the monomer is adjusted by the polymerization regulator, and the molecular weight of the polymer of the monomer contained in the composition is substantially the same. A method for manufacturing the plastic optical member described above; and a method for manufacturing the plastic optical member, wherein the core portion has a refractive index distribution in a cross-sectional direction of a diameter.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. For the optical member of the present invention, various members can be obtained by first producing a preform and processing the preform according to the application. For example, an optical fiber can be obtained by stretching the preform, and a light guide material can be obtained by slicing the preform in the cross-sectional direction, and a lens can be obtained when the preform has a refractive index distribution.

First, various raw materials for the plastic optical member preform used in the manufacturing method of the present invention will be described. In the present invention, the clad portion of the plastic optical member preform is made of a polymer. The cladding portion preferably has a refractive index lower than that of the core portion in order to retain the transmitted optical signal in the core portion, and is preferably transparent to the transmitted light. . For example, W
Polymethylmethacrylate (PMMA), benzylmethacrylate (BzMA), styrene (St), deuterated polymethylmethacrylate (PMMA-d8, d5, d3), polytrifluoroethylmethacrylate, as in O93 / 08488. (P3FMA), homopolymers such as polyhexafluoroisopropyl 2-fluoroacrylate (HFIP 2-FA), copolymers composed of two or more of these monomers, and mixtures thereof. Since these do not impair the transparency after the polymerization, it is desirable to reduce impurities and foreign substances which are scattering sources. In addition, it is preferable to use the same raw material as that of the polymer forming the core portion, since the transparency of the core / clad interface can be maintained.

In the present invention, the core portion of the plastic optical member preform is made of a polymer. The core part is not particularly limited as long as it is transparent to the transmitted light,
It is preferable to use a material that causes less transmission loss of the transmitted optical signal. For example, polymethylmethacrylate (PMM
Examples thereof include (meth) acrylic acid-based resins such as A) and copolymers thereof. In addition, when the optical member is used for near infrared light, absorption loss due to the vibration mode of the C—H bond constituting the optical member occurs, and therefore WO93 / 08.
As described in the specification of US Pat. No. 488, a polymer of a monomer in which a C—H bond is replaced with deuterium or other fluorine is substituted, for example, deuterated polymethylmethacrylate (P
MMA-d8), polytrifluoroethyl methacrylate (P3FMA), polyhexafluoroisopropyl 2
-Homopolymers such as fluoroacrylates (HFIP2-FA), copolymers consisting of two or more of these monomers, and mixtures thereof. It is preferable to select a raw material that is easy to perform bulk polymerization and form the core portion with a single polymer. Further, it is also possible to apply a homopolymer, a copolymer or a mixture thereof, which is composed of a monomer in which a hydrogen atom of these monomers is replaced with a deuterium atom (D) or a halogen atom (X). In a specific wavelength region, optical transmission loss due to C-H coupling occurs, but by replacing H with D or X, the wavelength region in which this transmission loss occurs can be made longer and the transmission signal light The loss can be reduced. These are the same as the clad part, in order not to impair the transparency after polymerization,
It is desirable to reduce impurities and foreign substances that become scattering sources.

When the core portion has a refractive index distribution from the center to the outside (hereinafter referred to as "gradient distribution type core portion"), the gradient index plastic optical fiber has a high transmission capacity. It is preferable because it becomes a high-performance plastic lens. The gradient index core portion can be formed by using a refractive index adjusting agent. The refractive index adjusting agent can be contained in the core portion by adding the monomer to the raw material of the core portion and then polymerizing the monomer. The refractive index adjusting agent is described in WO93 / 0848 or JP-A-5-
In comparison with a polymer produced by synthesizing a monomer as described in Japanese Patent No. 173026, the difference from the solubility parameter is within 7 (cal / cm ³ ) ^1/2 and the difference in refractive index. Is 0.001 or more, and the polymer containing this has a property of increasing the refractive index as compared with a polymer without addition. Any of those having this property, capable of stably coexisting with the polymer, and stable under the polymerization conditions (polymerization conditions such as heating and pressurization) of the above-mentioned raw material monomer can be used. . For example, benzyl benzoate (BEN), diphenyl sulfide (D
PS), triphenyl phosphate (TPP), benzyl n-butyl phthalate (BBP), diphenyl phthalate (DP)
P), biphenyl (DP), diphenylmethane (DP
M), tricresyl phosphate (TCP), diphenyl sulfoxide (DPSO) and the like, among which BE
N, DPS, TPP, DPSO are preferred. Further, as described in JP-A-08-110420, by using a material that is a solid at 70 ° C. or less, the refractive index adjusting agent suppresses the mobility of the dopant and becomes difficult to diffuse during stretching. preferable.

By adjusting the concentration and distribution of the refractive index adjusting agent in the core portion, the refractive index of the plastic optical member preform can be changed to a desired value. The amount to be added is appropriately selected depending on the application and the core material to be combined.

In addition, other additives may be added to the core portion and the cladding portion as long as the optical transmission performance is not deteriorated. For example, a stabilizer can be added for the purpose of improving weather resistance and durability of the clad portion and the core portion. Further, a stimulated emission functional compound for amplifying an optical signal can be added for the purpose of improving the optical transmission performance. By adding the compound, the attenuated signal light can be amplified by the pump light, and the transmission distance is improved, so that it can be used as a fiber amplifier in a part of the optical transmission link. These additives are also added to the raw material monomer and then polymerized,
It can be contained in the core part and the clad part.

A polymerization initiator and a chain transfer agent are used for the purpose of controlling a polymerization state and a polymerization rate when a monomer as a raw material of the core portion and the clad portion is polymerized, and a molecular weight suitable for a heat drawing step. Can be added. The polymerization initiator can be appropriately selected depending on the monomer used. For example, WO93 / 0848
Benzoyl peroxide (BPO), t-butylperoxy-2-ethylhexanate (PBO), di-t-butylperoxide (PB) as described in US Pat.
D), t-butylperoxyisopropyl carbonate (PBI), n-butyl 4,4, bis (t-butylperoxy) valalate (PHV) and the like. The chain transfer agent is mainly used for adjusting the molecular weight of the polymer, and can be appropriately selected depending on the monomer. For example, 1-butanethiol as described in WO93 / 08488. , Dodecyl mercaptan and the like can be used. You may use together 2 or more types, respectively.

Next, embodiments of the present invention will be described in detail. One embodiment in which the production method of the present invention is applied to a production method of a plastic optical fiber is that the monomer is polymerized while rotating a container containing a composition containing a monomer and a polymer of the monomer to form a clad portion. The first step of producing a hollow cylindrical tube, the interfacial polymerization of the monomer in the hollow portion of the cylindrical tube to form a region to be a core part, and to form a core region and a cladding region. It is a method for producing a plastic optical fiber, including a second step of producing a reform and a third step of stretching the obtained preform.

In the present embodiment, in the first step, a cylindrical tube having a hollow portion to be a clad portion is manufactured. The cylindrical tube is a cylindrical polymerization container in which a composition containing a monomer as a raw material and a polymer of the monomer is injected, and the polymerization container is rotated (preferably in a state where the axis of the cylinder is kept horizontal). It can be produced by polymerizing the monomer while rotating. After injecting the composition into the container, it is preferable to rotate the container sufficiently (preferably 1 hour or more) before initiating the polymerization. During this time, the polymer of the monomer in the composition can be swollen by the monomer. Further, due to the centrifugal force of rotation, the monomer that has not penetrated into the polymer is present inside the polymerization container, and the polymer (polymer swollen by the monomer) is present outside. Come to do. When the polymerization is started in this state, the monomer penetrating into the polymer and the monomer present inside the polymer are polymerized, and the outer portion of the monomer mainly contained in the composition is A cylindrical tube is obtained, which is made of a polymer and whose inner part is mainly made of a polymer produced by polymerization of the above-mentioned monomer.

In the manufacturing method of the present embodiment, the outside of the cylindrical tube to be the clad portion can be mainly constituted by the polymer contained in the composition used as the raw material, so that the monomer to be polymerized during the formation of the clad portion can be formed. The amount can be reduced, and heat generation due to the polymerization reaction can be suppressed. As a result, it is possible to reduce the unevenness of the inner surface of the clad portion due to the heat generated by polymerization, or reduce the fluctuations that occur on the inner surface, and improve the productivity of plastic optical members with good performance, especially the productivity during mass production. Contribute to. In particular, in the present embodiment, since the core part is formed by interfacial gel polymerization in the hollow part of the clad part, the property of the inner wall of the clad part affects the interfacial polymerization, but a sufficiently purified high-purity monomer is used. By using it, the inner wall surface of the clad portion can be made into a uniform surface, which is also advantageous in that the optical loss can be further reduced.

When the monomer and the polymer of the monomer are charged into the polymerization container and then the polymerization container is rotated to swell the polymer with the monomer, the polymerization of the monomer is started. It should be carried out within a temperature range that does not cause it (for example, 30 ° C. or lower when a polymerization initiator described later is used), but at low temperature, when the affinity between the monomer and the polymer of the monomer is low, etc. Alternatively, an additive such as a polymerization initiator relating to the polymerization may be added last, and the temperature may be slightly elevated (usually, the temperature is raised to about 50 ° C. to 70 ° C.).

The content of the polymer of the monomer in the composition used in the first step is usually 30% by mass or more based on the total mass of the composition, although the preferable range varies depending on the kind. Is preferred. When the content of the polymer of the monomer is less than 30% by mass, the heat generated by the polymerization tends to increase and the fluctuation of the inner wall tends to increase. On the other hand, if the content of the polymer of the monomer is too large, there is a tendency that a uniform polymer cannot be produced because the amount of the monomer with respect to the polymer is insufficient. From this point, the content of the polymer of the monomer is 30 to composition
It is more preferably 60% by mass.

Into the container, a polymerization initiator, a polymerization modifier and a stabilizer optionally added can be injected together with the monomer and the polymer of the monomer.

It is preferable that the molecular weights of the polymer of the monomer used as the raw material of the clad portion and the polymer produced by the rotational polymerization are the same. When the molecular weights of both polymers are the same, various properties such as optical properties become uniform, and the productivity of high-performance plastic optical members can be further improved. Both molecular weights can be made substantially the same by injecting a polymerization regulator together with the monomer into the container and adjusting the molecular weight of the polymer produced by the polymerization of the monomer by the polymerization regulator. The amount average degree of polymerization of both polymers is 400 to 1
It is preferably 200, more preferably 500 to 1000, and even more preferably 800 to 1000. When the molecular weight of the polymer is within the above range, the subsequent stretching step can be stably performed. The polymerization regulator is
Generally, 0.10 to 0.40 mass% is preferably added to the monomer, and 0.15 to 0.30 mass% is more preferably added.

As the polymerization initiator, it is preferable to use a material having a 10-hour half-life temperature (t _1/2 ° C) which is not higher than the boiling point of the monomer. Here, the ten-hour half-life temperature of the polymerization initiator means the temperature at which the number of the initiator is decomposed to become 1/2 in 10 hours. As the polymerization initiator, a material whose 10-hour half-life temperature is not higher than the boiling point of the starting monomer is used,
The monomer is {(t _1/2 ) -20} ° C or higher (t _1/2 ° C)
It is preferable to polymerize with the above-mentioned polymerization initiator at the following temperature. When a polymerization initiator having the above characteristics is used and the polymerization is carried out within the above temperature range, the efficiency of the polymerization is good, so that the productivity is prevented from being lowered, and explosive polymerization occurs due to the accumulation of reaction heat in rapid polymerization. Is preferable because it can be suppressed. For example, when methyl methacrylate (MMA) is used as a monomer for the clad part, PBO is one of the above-exemplified polymerization initiators as a polymerization initiator having a 10-hour half-life temperature not higher than the boiling point of MMA. To do. For example,
MMA is used as a monomer and PBO is used as a polymerization initiator.
When used, the polymerization temperature is from 10 to 16 at 70 to 50 ° C.
It is preferable to polymerize for 0 hours. In addition, the addition amount of the polymerization initiator can be appropriately determined in a preferable range according to the type of the monomer to be used, etc., but generally 0.10 to 1.00 mass% is added to the monomer. Is preferable, and it is more preferable to add 0.40 to 0.60 mass%.

After the rotational polymerization, the structure obtained may be subjected to a heat treatment at a temperature higher than the polymerization temperature of the rotational polymerization for the purpose of completely reacting the remaining monomer and the polymerization initiator.

Regarding the size of the polymerization vessel used in the first step, the amount of the composition as the raw material of the clad portion to be injected, and the number of rotations per unit time during rotational polymerization,
Objective plastic optical member (or preform)
Can be appropriately determined according to the size of the.

In the second step, the monomer as the raw material of the core portion is injected into the hollow portion of the cylindrical tube produced in the first step, and the monomer is interfacially polymerized. A polymerization initiator, a polymerization modifier and a refractive index modifier optionally added can be injected together with the monomer. The monomer is preferably the same as the monomer used to form the cylindrical tube (clad portion). Regarding the amount of addition, a preferable range can be appropriately determined according to the type of the monomer used, but the polymerization initiator is generally added in an amount of 0.005 to 0.050 mass% with respect to the monomer. Is preferable, and it is more preferable to add 0.010 to 0.020 mass%. Generally, the chain transfer agent is preferably added in an amount of 0.10 to 0.40% by mass, more preferably 0.15 to 0.30% by mass, based on the monomers. In the present embodiment, even if the refractive index adjusting agent is not used, by using two or more kinds of monomers,
It is also possible to introduce the distribution of the refractive index into the region which becomes the core portion.

In the second step, the polymerization of the monomer proceeds from the inner wall surface of the cylindrical tube toward the center in the radial direction of the cross section. When two or more kinds of monomers are used, the monomer having a high affinity for the polymer forming the cylindrical tube is unevenly distributed mainly on the inner wall surface of the cylindrical tube, and is mainly polymerized. A high polymer is formed.
Towards the center, the proportion of said high affinity monomers in the polymer formed decreases and the proportion of other monomers increases. In this way, the distribution of the monomer composition is generated in the region that becomes the core portion, and as a result, the distribution of the refractive index is introduced. In addition, when a refractive index adjusting agent is added to the monomer for polymerization, the core liquid dissolves the inner wall of the clad and the polymer constituting the clad swells to form a gel as described in WO93 / 08488. Polymerization proceeds while configuring. At this time, a monomer having a high affinity for the polymer forming the cylindrical tube is unevenly distributed on the inner wall surface of the cylindrical tube to polymerize, and a polymer having a low refractive index adjusting agent concentration is formed on the outside. To be done. The ratio of the refractive index adjusting agent in the formed polymer increases toward the center. In this way, a concentration distribution of the refractive index adjusting agent is generated in the region that becomes the core portion, and as a result, the distribution of the refractive index is introduced.

As described above, in the second step,
It is possible to introduce a refractive index distribution into the region that will be the core part to be formed, but since the thermal behavior also differs between parts with different refractive indexes, if the polymerization is carried out at a constant temperature, the core will differ in its thermal behavior. In the area that becomes a part, the response of volume contraction generated to the polymerization reaction changes, bubbles are mixed in the preform, or microscopic voids are generated, and when the obtained preform is heated and stretched. There is a possibility that a large number of air bubbles will be generated. If the polymerization temperature is too low, the polymerization efficiency is lowered, the productivity is remarkably impaired, the polymerization is incomplete, the light transmittance is lowered, and the light transmission ability of the produced optical member is impaired. On the other hand, when the initial polymerization temperature is too high, the initial polymerization rate is remarkably increased, the response to the contraction of the core region cannot be relaxed, and the tendency of bubble generation is remarkable. Therefore, it is desirable to polymerize at an appropriate polymerization temperature depending on the monomer used. For example, when MMA is used as the raw material of the core part, the polymerization temperature is preferably 50 to 150 ° C, more preferably 80 to 120 ° C. It is also possible to further reduce the generation of bubbles by dehydrating and / or deaerating the monomer in a reduced pressure atmosphere before injecting the monomer as the raw material of the core portion into the hollow portion of the cylindrical tube.

In the polymerization of the core, a polymerization initiator having a ten-hour half-life temperature of not less than the boiling point of the monomer is used, and at least 10% of the half-life time of the polymerization initiator is applied to the initial polymerization temperature. It is preferable to carry out late polymerization at a temperature not lower than Tg of the polymer and not higher than Tg + 40 ° C. after the half-life time of the polymerization initiator. Polymerization under these conditions can reduce the initial polymerization rate and improve the volumetric shrinkage responsiveness in the initial polymerization, and as a result, it is possible to reduce the inclusion of bubbles in the preform due to volumetric shrinkage and improve productivity. can do. Methyl methacrylate (M
When MA) is used, PBD and PHV among the above-exemplified polymerization initiators are applicable as the polymerization initiator having a 10-hour half-life temperature not lower than the boiling point of MMA. For example, when MMA is used as the monomer and PBD is used as the polymerization initiator, the initial polymerization temperature is 100 to 110 ° C. and 48 to
It is preferable to maintain the temperature for 72 hours, then raise the temperature to 120 to 140 ° C. and polymerize for 24 to 48 hours. When PHV is used as a polymerization initiator, the initial polymerization temperature is 100 to 1
It is preferable to maintain at 10 ° C. for 4 to 24 hours, raise the temperature to 120 to 140 ° C., and polymerize for 24 to 48 hours. The temperature may be raised stepwise or continuously, but it is preferable that the time for raising the temperature is short.

In the second step, in the second step, polymerization is carried out under pressure as described in JP-A-9-269424 or under reduced pressure as described in WO93 / 08488. May be carried out (hereinafter, polymerization carried out under pressure is referred to as “pressure polymerization”). When carrying out pressure polymerization, after injecting the monomer which is the raw material of the core part into the cylindrical tube which is the clad part, the cylindrical tube is inserted into the hollow part of the jig and is supported by the jig. It is preferable to carry out polymerization. It is preferable that the jig has a shape having a hollow portion into which the cylindrical tube can be inserted, and the hollow portion has a shape similar to that of the cylindrical tube. The jig suppresses the deformation of the cylindrical tube during the pressure polymerization, and also supports the contraction of the region serving as the core portion as the pressure polymerization progresses. Therefore, it is preferable that the hollow portion of the jig has a diameter larger than the outer diameter of the cylindrical tube and supports the cylindrical tube in a non-contact state. The hollow portion of the jig preferably has a diameter larger by 0.1% to 40% than the outer diameter of the cylindrical tube, and has a diameter larger by 10 to 20%. More preferable. In the present embodiment, since the jig has a cylindrical shape, the inner diameter of the jig is preferably 0.1% to 40% larger than the outer diameter of the cylindrical tube, and 10% to 20% larger. Is more preferable.

The cylindrical tube can be placed in the polymerization container while being inserted into the hollow portion of the jig. In the polymerization container, the cylindrical tube is preferably arranged with the height direction of the cylinder vertical. After arranging the cylindrical tube in the polymerization container while being supported by the jig, the inside of the polymerization container can be pressurized. In the case of pressurizing, it is preferable to pressurize the inside of the polymerization vessel with an inert gas such as nitrogen and proceed the pressure polymerization in an inert gas atmosphere. The preferred range of pressurization during polymerization varies depending on the monomer used, but the pressure during polymerization is generally 0.01 to 1.0 MPa.
A degree is preferable.

A preform for the plastic optical member is obtained through the first and second steps.

In this embodiment, the first and second
Although the step of heat-polymerizing the monomer is shown as the step of 1, the monomer can be polymerized by irradiating with light such as ultraviolet rays.

In the third step, the desired optical transmission medium can be obtained by processing the preform produced in the second step. For example, a flat lens can be obtained by slicing a preform, or a plastic optical fiber can be obtained by melt drawing. In particular, when the region serving as the core portion of the preform has a refractive index distribution, a plastic optical fiber having a uniform light transmission ability can be manufactured with high productivity and stably.

When processing into the form of an optical fiber, the preform is stretched while being heated. The heating temperature can be appropriately determined according to the material of the preform,
Generally, 180 to 250 ° C is preferable. Stretching conditions (stretching temperature and the like) can be appropriately determined in consideration of the diameter of the obtained preform, the diameter of the desired plastic optical fiber, the material used, and the like. For example, regarding the linear tensile force, 10 g or more for orienting the molten plastic as described in JP-A-7-234322, or strain after melt drawing as described in JP-A-7-234324. 100 to avoid leaving
It is preferably not more than g. In addition, JP-A-8-106
As described in Japanese Patent No. 015, it is also possible to adopt a method of performing preheating during stretching. Regarding the fiber obtained by the above method, the bending elongation and the lateral pressure characteristic of the fiber can be improved by defining the breaking elongation and hardness of the obtained strand as described in JP-A-7-244220.

The plastic optical fiber manufactured through the third step can be used as it is for various purposes. Further, for the purpose of protection and reinforcement, a form having a coating layer on the outside, a form having a fiber layer, and / or
Alternatively, a plurality of fibers may be bundled for various uses. In the coating step, for example, in the case where a coating is provided on the fiber strand, the fiber strand is passed through opposite dies having a hole through which the fiber strand passes, and the molten coating resin is filled between the facing dies. A coated fiber can be obtained by moving between the dice. Since the coating layer protects the internal fiber from stress when it is flexible, it is desirable that it is not fused with the fiber strand. Further, at this time, the fiber strand is thermally damaged by coming into contact with the molten resin, and therefore it is also desirable to select a resin that can be melted at a moving speed or a low temperature that suppresses the damage as much as possible. At this time, the thickness of the coating layer depends on the melting temperature of the coating material, the drawing speed of the wire, and the cooling temperature of the coating layer. In addition, a method of polymerizing a monomer applied to an optical member, a method of winding a sheet, a method of passing an optical member through an extrusion-molded hollow tube, and the like are known.

In this embodiment, the manufacturing method of the drawn fiber is shown. However, optical members such as an optical lens and an optical waveguide are produced from the preforms obtained in the first and second steps. You can

[0040]

EXAMPLES The present invention will be described in more detail with reference to the following examples. The materials, reagents, ratios, operations and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below. [Example 1] An inner diameter of 30 mm and a length of 10 with sufficient rigidity having an inner diameter corresponding to the outer diameter of a preform to be planned.
In a 00 mm cylindrical container, 0.5% by mass of benzoyl peroxide having a 10-hour half-life temperature of 73.6 ° C. dehydrated and purified as a polymerization initiator, and n-butyl mercaptan as a polymerization regulator (chain transfer agent) were used. Of 0.28% by mass, and then injecting MMA monomer from which water is removed to 0.008%,
Then, PMMA having sufficient transparency in the polymerization container
MMA for which (weight average molecular weight Mw = 80,000) is planned
-212 g which became 40 mass% was added with respect to the total mass of 530 g of PMMA mixed composition. Then, at room temperature (25
C.) and kept in a horizontal state at 3000 rpm for 3 hours to melt, and then kept at 70.degree. C. in a horizontal state and rotated at 3000 rpm for 5 hours for heat polymerization. Then, heat treatment was performed at 90 ° C. for 24 hours to obtain a hollow cylindrical tube made of PMMA. The obtained cylindrical tube made of PMMA was a homogeneous and completely hollow cylindrical tube without eccentricity, fluctuation of the inner wall, and inclusion of bubbles. When the weight average molecular weight of PMMA forming the obtained cylindrical tube was measured, the weight average molecular weight was Mw = 80000.

Next, in the hollow portion of the obtained cylindrical tube made of PMMA, MMA from which water was removed to 0.008%,
A solution mixed with a low-molecular compound for forming the refractive index distribution,
The filtrate was directly injected while filtering with a membrane filter made of ethylene tetrafluoride having an accuracy of 0.2 mm. Diphenyl sulfide is used as the low molecular weight compound, and is 1 for MMA.
1 mass% was added. Further, as a polymerization initiator, di-t
0.01% of ert-butyl peroxide to MMA
3 mass% and 0.27 mass% of n-lauryl mercaptan as a chain transfer agent with respect to MMA. When the cylindrical tube made of PMMA, into which MMA or the like was injected, was left standing vertically in the pressure polymerization vessel, the diameter of the PMMA cylindrical tube was 2 m with respect to the outer diameter.
It was inserted into a glass tube having a diameter larger by m. afterwards,
After replacing the inside of the pressure polymerization vessel with a nitrogen atmosphere, 0.2 Mp
The pressure was increased to a and heat polymerization was performed at 120 ° C. for 48 hours to obtain a preform.

This preform was drawn by hot drawing at 200 ° C., and a plastic optical fiber having a diameter of 700 to 800 μm was stably obtained at 2000 m. When the transmission loss of the obtained fiber was measured, it was 160 dB / km.

In Example 1, 20 was added to the total mass of the MMA / PMMA mixed composition for PMMA.
An attempt was made to form a PMMA tube by adding it in a mass% by rotation, but in this case, the polymerization proceeded while the viscosity of the inner wall was low, so that there was some inner wall fluctuation (however, compared with the one obtained in Comparative Example 1). Then, the degree of fluctuation was remarkably reduced.) A PMMA cylindrical tube was obtained. Using the obtained PMMA cylindrical tube, a core portion was formed in the same procedure as in Example 1 to obtain a preform, and further drawing was carried out by hot drawing in the same manner. As a result, the fiber diameter of the obtained fiber became slightly unstable due to the fluctuation of the inner wall of the PMMA cylindrical tube. In addition, fluctuations in the core diameter occur due to fluctuations in the inner wall of the PMMA cylindrical tube, and the transmission loss value is 230 dB / km.
Met.

COMPARATIVE EXAMPLE 1 In Example 1, PMMA
A cylinder made of PMMA in the same procedure as in Example 1 except that MMA was poured into a container without using the above, and viscosity was improved by prepolymerization at 70 ° C. within 2 hours, and then rotational polymerization was carried out. An attempt was made to make a tube. Depending on the timing of transition from prepolymerization to rotational polymerization, a rapid polymerization reaction partially occurs due to the gel effect, a foaming phenomenon occurs during the rotational polymerization process at 70 ° C, and PMMA at the completion of polymerization even when foaming does not occur. The inner wall of the cylindrical tube had a remarkable fluctuation, and it was difficult to use it as a cladding for a plastic optical fiber.

[0045]

According to the present invention, it is possible to provide a manufacturing method capable of stably manufacturing a plastic optical member having good performance with high productivity. In particular, a large-diameter gradient index plastic optical fiber can be manufactured with high productivity.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Takahito Miyoshi             Fuji Photo, 210 Nakanuma, Minamiashigara City, Kanagawa Prefecture             Within Film Co., Ltd. (72) Inventor Yukio Shirakura             Fuji Photo, 210 Nakanuma, Minamiashigara City, Kanagawa Prefecture             Within Film Co., Ltd. (72) Inventor Toru Ogura             Fuji Photo, 210 Nakanuma, Minamiashigara City, Kanagawa Prefecture             Within Film Co., Ltd. F-term (reference) 2H050 AA17 AB43X AB43Y AB44X                       AB44Y AB50X AB50Y AC05

Claims (2)

[Claims] 1. A method for producing a clad part of a plastic optical member comprising a core part and a clad part, wherein the monomer is polymerized while rotating a container containing a composition containing a monomer and a polymer of the monomer. A method for manufacturing a plastic optical member, including a polymerization step of forming a clad portion. 2. A plastic optical member obtained by the manufacturing method according to claim 1.