JP2007034063A - Method for manufacturing improved refractive index distribution type light transmitter according to self-propagating frontal polymerization utilizing heat storage effect - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light transmitter having a large refractive index between the center axis and the periphery, with respect to the refractive index distribution type light transmitter which is prepared by using self-propagating frontal polymerization utilizing heat storage effect and has the refractive index changed gradually from the center axis. <P>SOLUTION: In the method for manufacturing the refractive index distribution type light transmitter having the refractive index changed gradually from the center axis, by using the self-propagating frontal polymerization utilizing heat storage effect, the self-propagating frontal polymerization is caused to progress from the center part of a polymerization vessel toward the periphery part of the polymerization vessel and/or from the periphery part of the polymerization vessel toward the center part of the polymerization vessel, while using monomer, polymer and polymerization initiator as material. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a refractive index distribution type optical transmission body in which a refractive index gradually changes from a central axis, using spontaneous frontal polymerization using a heat storage effect. Furthermore, the present invention relates to an optical transmission body such as an optical fiber and a lens manufactured by such a method.

  A lens whose refractive index continuously changes in the radial direction is called a refractive index distribution (GRIN) type lens, and is expected to be applied to various optical devices in recent years. The GRIN type lens has superior optical characteristics compared to the uniform refractive index lens, and can reduce the thickness and aberration of the lens. Various methods have been developed as a method of manufacturing a GRIN lens (see Patent Documents 1 to 9).

  The present inventor previously described a monomer and a polyfunctional monomer having one or more double bonds such as an allyl group, an acrylic group, a methacryl group, and a vinyl group, a propionic acid ester, an isobutyric acid ester, or a phthalic acid ester. And a method called spontaneous frontal polymerization (frontal polymerization method) using a low-molecular compound (low-molecular dopant) such as adipic acid ester and a polymerization initiator (see Patent Document 10). Spontaneous frontal polymerization is a polymer-monomer interface called the front at the center of the polymerization vessel due to the three factors of heat storage effect, gel effect, and thermal diffusion, and this front moves to the periphery of the polymerization vessel. This is a polymerization method (FIG. 1). By this method, it is possible to form a polymer from the central portion of the polymerization vessel, so that mixing of bubbles can be reduced.

Japanese Patent No.976507 Japanese Patent No. 1858593 Japanese Laid-Open Patent Publication No. 5-173026 Japanese Patent Laid-Open No. 5-241036 JP-A-6-186441 Japanese Unexamined Patent Publication No. 6-19530 JP-A-8-54520 JP-A-8-62434 Japanese Patent Laid-Open No. 9-269424 WO 2004/068202

  The present invention does not require pre-treatment and does not require a complicated apparatus, and uses a simple apparatus, without limiting the material of the polymerization vessel, and the refractive index gradually changes from the central axis. It is an object of the present invention to obtain a refractive index distribution type optical transmission body that is a refractive index distribution type optical transmission body that is free of bubbles and cavities and has excellent transparency. Specifically, the present invention relates to a method for producing a refractive index distribution type optical transmission body in which a refractive index gradually changes from a central axis, using spontaneous frontal polymerization using a thermal effect, comprising: By allowing spontaneous frontal polymerization to proceed from the polymerization vessel center to the polymerization vessel periphery and / or from the polymerization vessel periphery to the polymerization vessel center using the monomer, polymer and polymerization initiator as An object of the present invention is to provide a method of manufacturing an optical transmission body having a large refractive index difference between the central axis and the periphery. In addition, the present invention provides a refractive index in which the central axis of the refractive index is offset from the center of the lens by tilting the polymerization container when producing a refractive index distribution type optical transmission body using spontaneous frontal polymerization. It is an object of the present invention to provide a method for manufacturing a distributed optical transmission body.

  The present inventor previously described a monomer and a polyfunctional monomer having one or more double bonds such as an allyl group, an acrylic group, a methacryl group, and a vinyl group, a propionic acid ester, an isobutyric acid ester, or a phthalic acid ester. We have developed a method called spontaneous frontal polymerization (frontal polymerization method) using low molecular weight compounds (low molecular dopants) such as adipic acid esters and polymerization initiators.

  The present inventor has intensively studied a method for manufacturing an optical transmission body in which the difference between the refractive index at the center and the refractive index at the periphery is large.

  As a result, it was found that the site where polymerization is initiated varies by mixing the monomer, the polymer and the polymerization initiator and adjusting the mixing ratio of the polymer to the monomer when performing frontal rimization. That is, when the mixing ratio of the polymer is low, the polymerization proceeds from the center of the polymerization vessel toward the peripheral portion, and when the mixing ratio of the polymer is high, the polymerization proceeds from the peripheral portion of the polymerization vessel toward the central portion. In the middle, the polymerization proceeds in two directions from the central portion of the polymerization vessel to the peripheral portion and from the peripheral portion of the polymerization vessel to the central portion. In this way, by adjusting the polymerization start site and the traveling direction, an optical transmission body having an arbitrary refractive index distribution can be produced. In particular, by allowing the polymerization to proceed in two directions, the central portion and the peripheral portion can be produced. Thus, an optical transmission body having a large difference in refractive index from the above could be produced.

  In order to produce an optical transmission body having an arbitrary refractive index distribution, the present inventor has intensively studied a method for manufacturing an optical transmission body whose center is shifted from the central axis of the polymerization vessel. As a result, it has been found that an optical transmission body with an off-center can be produced by adding a polymerization inhibitor during polymerization and tilting the polymerization vessel from the vertical direction.

That is, the aspects of the present invention are as follows.
[1] In a method of manufacturing a refractive index distribution type optical transmission body in which the refractive index gradually changes from the central axis, a monomer, a polymer and a polymerization initiator are filled in a polymerization vessel, the polymerization vessel is heated, and the addition of the polymer Refractive index distribution type characterized in that one or both of a front formation polymerization reaction from the container center to the container periphery and a front formation polymerization reaction from the container periphery to the container center proceed by adjusting the amount A method for producing an optical transmission body,
[2] In a method of manufacturing a refractive index distribution type optical transmission body in which the refractive index gradually changes from the central axis, a monomer, a polymer and a polymerization initiator are filled in a polymerization vessel, the polymerization vessel is heated, and the addition of the polymer The refractive index of [1], wherein both the front-forming polymerization reaction from the container center to the container periphery and the front-forming polymerization reaction from the container periphery to the container center are advanced by adjusting the amount A method for producing a distributed optical transmission body;
[3] A method for producing a refractive index distribution type optical transmission body according to [2], wherein the polymer is contained in an amount of 5 to 10% by weight with respect to the monomer when the polymerization container is filled.
[4] A method for producing a refractive index distribution type optical transmitter according to any one of [1] to [3], wherein two or more types of monomers and / or polymers are filled in a polymerization vessel,
[5] A method for producing a refractive index distribution type optical transmitter according to any one of [1] to [4], wherein the heating temperature is 50 ° C. or less,
[6] A method for producing a refractive index distribution type optical transmitter according to [5], wherein the polymerization initiator has a 10-hour half-life temperature of 20 ° C. to 70 ° C.,
[7] The method for producing a refractive index distribution type optical transmitter according to [6], wherein the polymerization initiator is selected from the group consisting of organic peroxides, persulfates, and azo compounds,
[8] A method for producing a refractive index distribution type optical transmitter according to any one of [1] to [7], wherein the monomer is methacrylic acid ester or acrylic acid ester;
[9] A method for producing a refractive index distribution type optical transmitter according to any one of [1] to [8], wherein the polymer is selected from the group consisting of polyalphamethylstyrene.
[10] An optical transmission body having a length exceeding 50% of the height in the polymerization container is produced by tilting the polymerization container from 10 degrees to 90 degrees with respect to the vertical direction. Any one of [1] to [9] A method for producing a refractive index distribution type optical transmission body,
[11] A method for producing a refractive index distribution type optical transmitter according to [10], wherein an optical transmitter having a length of 75% or more of the height in the polymerization vessel is prepared;
[12] Further, by adding a polymerization inhibitor or a polymerization inhibitor in the polymerization vessel and tilting the polymerization vessel from 10 degrees to 90 degrees with respect to the vertical direction, the center is shifted from the central axis of the polymerization vessel. A method for producing a refractive index distribution type optical transmission body according to any one of [1] to [9].
[13] A method for producing a refractive index distribution type optical transmitter according to [12], wherein the polymerization vessel is tilted by 75 to 90 degrees with respect to the vertical direction.
[14] A method for producing a refractive index distribution type optical transmitter according to [12] or [13], wherein the polymerization inhibitor is a hydroquinone compound or a derivative thereof, 2,2-diphenyl-1-picrylhydrazyl or nitrobenzene,
[15] The method for producing a refractive index distribution type optical transmitter according to any one of [12] to [14], wherein the addition amount of the polymerization inhibitor is 0.0001 to 0.002% by weight based on the monomer,
[16] A method for producing a refractive index distribution type optical transmitter according to any one of [10] to [15], wherein a propionic acid ester or an isobutyric acid ester is added as a low-molecular compound instead of a polymer;
[17] An optical transmission body manufactured by the refractive index distribution type optical transmission body manufacturing method according to any one of [1] to [16].

  By using the method of the present invention, the frontal polymerization can proceed from the central part, the peripheral part or both the central part and the peripheral part in the polymerization vessel, and the refractive index distribution of the optical transmission member to be produced can be freely set. Can be designed. In particular, when frontal polymerization is advanced from both the central portion and the peripheral portion of the polymerization vessel, an optical transmission body having a large difference in refractive index between the central portion and the peripheral portion can be produced.

  Since the refractive index distribution can be freely designed in this way, an optical lens having an arbitrary refractive index distribution can be obtained. Further, an optical transmission body having a large difference in refractive index between the central portion and the peripheral portion can be used as an optical transmission fiber with little optical transmission loss even in a bent state.

  Furthermore, the method of the present invention makes it possible to produce an optical transmission body whose center is shifted. By shifting the center, a lens having a non-uniform refractive index can be produced.

  The method of the present invention makes it possible to produce a refractive index distribution type optical transmission body having an arbitrary shape and an arbitrary refractive index distribution by using a polymerization vessel having an arbitrary shape.

  The shape of the polymerization vessel used in the present invention may be a hollow spherical shape, a shape like a hollow egg, or a shape such as a cylindrical shape that can transfer heat from the outside of the vessel and induce a heat storage effect. . For example, when an artificial lens imitating an animal crystalline lens is to be produced, a container having a crystalline lens shape may be produced and used as a polymerization container. Here, the heat storage effect means that when the polymerization container containing the light transmission material is heated inside, the added heat gathers from the outside of the container to the center of the polymerization container and the central part is heated compared to other parts. That means. That is, the shape in which the heat storage effect is induced means a shape in which heat applied from the periphery of the polymerization vessel can be concentrated in the center of the vessel by conduction. Since the central portion where heat is stored is determined by the shape of the polymerization container, the polymerization container shape can be designed to start polymerization from an arbitrary position. Further, since the polymerization container itself does not require reactivity, any material such as metal, plastic, glass, ceramics, ceramics can be used. Furthermore, an arbitrary shape can be formed by using a plastic material.

  The material of the optical transmission body of the present invention includes a monomer, a polymer, a polymerization initiator, and the like, and these substances are filled in the polymerization container. When the center in the polymerization vessel reaches a certain temperature or higher due to the heat storage effect due to heating, the polymerization initiator acts and polymerization starts at the central portion in the polymerization vessel. Polymerization of the monomer begins, and a front composed of the interface between the monomer and the polymer is formed, and the polymerization proceeds while the front moves from the central part toward the inner wall of the polymerization vessel and / or from the peripheral part toward the central part ( Frontal polymerization).

  When polymer is used instead of the low molecular weight compound, it is possible to form a clad layer portion of the optical fiber in the polymer. That is, it is possible to produce an optical fiber preform with a clad layer that has a refractive index distribution in a portion that guides light and that does not leak light by a single polymerization. Furthermore, if this is heat-stretched, a graded index optical fiber can be obtained. When considering application to intraocular lenses, a polymer of 2-methacryloyloxyethyl phosphorylcholine (MPC), which is currently attracting attention as a biocompatible material, can be used. By successfully forming this in the vicinity of the surface of the artificial crystalline lens material, the biocompatibility of the element can be improved.

  Monomers that can be used in the present invention are polyfunctional monomers having one or more double bonds such as allyl group, acrylic group, methacryl group, and vinyl group, which give a transparent polymer. Without limitation, styrene (1.592), parachlorostyrene (1.610), acrylonitrile (1.520), methacrylonitrile (1.520), vinyl phenylacetate (1.567), vinyl benzoate (1.578), vinylnaphthalene (1.682), acrylic Methyl acetate (1.480), Methyl methacrylate (1.490), Ethyl acrylate (1.469), Ethyl methacrylate (1.485), Butyl acrylate (1.463), Butyl methacrylate (1.483), Cyclohexyl methacrylate (1.507), Methacrylic acid Phenyl (1.571), benzyl methacrylate (1.568), naphthyl methacrylate (1.635), triflate methacrylate Examples include oroethyl (1.437) and hydroxyethyl methacrylate (1.512). The refractive index when each monomer is polymerized is shown in parentheses.

  Among these, styrene, methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, adamantyl (meth) acrylate, (meth) acrylic Alkyl (meth) acrylate monomers such as acid perfluoro and hydroxyethyl (meth) acrylate are particularly preferred.

  Examples of the polymer that can be used in the present invention include polymers and copolymers of the above monomers, and also biocompatible materials such as polyalphamethylstyrene, a copolymer of maleic anhydride and vinyl ether, and 2-methacryloyloxyethyl phosphorylcholine (MPC). Include a functional polymer. The molecular weight of the polymer used is 3,000 to 500,000. As the molecular weight increases, frontal polymerization starts from the periphery of the polymerization vessel at a lower concentration. Of these, polyalphamethylstyrene is particularly preferred.

  Moreover, both the monomer and the polymer may contain a plurality of types, and the mixing ratio of different types of monomers and the mixing ratio of different types of polymers are not limited. For example, when a plurality of types of monomers are used, a monomer that is more easily polymerized is polymerized at the center of the optical transmission body. In consideration of the refractive index, solubility, ease of polymerization, and the like of the monomer to be used, an optical transmission body having a desired refractive index distribution can be produced by selecting the type of monomer and polymer.

  When the light transmitter is used as an artificial intraocular lens simulating the refractive index distribution of an animal lens, the monomer and polymer must be biocompatible materials. Here, biocompatibility refers to an attribute of a material that can coexist with a living body while performing its original function without giving adverse effects or strong stimulation to the living body for a long period of time. Examples of the biocompatible monomer include hydroxyethyl (meth) acrylate and glycerin monomethacrylate, and the biocompatible polymer includes MPC. However, the biocompatible monomer is not limited thereto.

  The polymerization initiator is used by mixing with a monomer and a polymer. As the polymerization initiator, known ones can be used. However, since the polymerization reaction of the present invention proceeds at a relatively low temperature, preferably 50 ° C. or less, it is preferable that the polymerization initiator also works at a relatively low temperature for 10 hours. The half-life temperature is preferably equal to or lower than the polymerization temperature, for example, about 40 ° C. A polymerization initiator having a 10-hour half-life temperature equal to or higher than the temperature at the time of polymerization can also be used. For example, a polymerization initiator having a 10-hour half-life temperature of about 70 ° C. or less can be used. In this case, the efficiency of the polymerization reaction is lowered, but polymerization occurs, so that the optical transmission body of the present invention can be obtained. The polymerization initiator to be used can be appropriately selected using a 10-hour half-life temperature as an index depending on the temperature at which the polymerization proceeds. Examples of polymerization initiators include azo compounds such as azobisisobutyronitrile and azobisisovaleronitrile, organic peroxides such as peroxycarbonates and peroxyesters, persulfates, benzoyl peroxide (10 Time half-life temperature of about 70 ° C.) and the like, and these can be used alone or in appropriate combination. The polymerization initiator may be mixed in an amount of 0.1 to 10% by weight with respect to the monomer.

  Among these, persulfates are mainly used as an aqueous polymerization initiator, and examples of persulfates include ammonium persulfate, sodium persulfate, and potassium persulfate. Peroxycarbonates include diisopropyl peroxydicarbonate (10-hour half-life temperature 40.5 ° C), di-n-propyl peroxydicarbonate (40.5 ° C), and bis (4-t-butylcyclohexyl) peroxydi. Carbonate (40.8 ° C), di (2 ethoxyethyl) peroxydicarbonate (43.4 ° C), di (2ethylhexyl) peroxydicarbonate (43.5 ° C), etc., as peroxyesters, cumylperoxyneodecano Ate (36.5 ° C), 1,1,3,3 tetramethylbutylperoxyneodecanoate (40.7 ° C), t-hexylperoxyneodecanoate (44.5 ° C), t-butylperoxyneodecanoate (46.4 ° C).

  If necessary, molecular weight modifiers can be used alone or in appropriate combination. Examples of the molecular weight modifier include alkyl halides such as carbon tetrachloride and carbon tetrabromide, and mercaptans such as butyl mercaptan, lauryl mercaptan, octyl mercaptan, dodecyl mercaptan, 2-hydroxyethyl mercaptan, and octyl thioglycolate. .

  In addition, a polyfunctional monomer may be added as long as the transparency of the produced polymer is not impaired. By doing so, the rigidity of the produced polymer is increased, and at the same time, the chemical resistance is excellent. As the polyfunctional monomer, ethylene glycol dimethacrylate, divinylbenzene or the like can be used in an amount of about 20% by weight based on the monomer. Examples of the antioxidant include hindered phenols and hindered amines.

  In the polymerization of the present invention, a solvent can be used. However, when a solvent is used, a solvent removal step after the polymerization is necessary, and a bad effect due to the solvent removal occurs. It is desirable to carry out the polymerization reaction using the monomer itself or the polymer itself instead of the solvent.

  In the method of the present invention, a polymerization vessel is filled with a mixture of the above monomer, polymer, polymerization initiator and the like at a predetermined mixing ratio, and polymerization is started. At this time, it is preferable to first dissolve the polymer in the monomer and add the polymerization initiator to the solution. Further, the mixing may be performed simultaneously with the filling or may be performed after filling the polymerization container. At this time, the mixture is preferably substituted with nitrogen in order to prevent suppression of polymerization due to oxygen in the mixture. After filling, the polymerization vessel is allowed to stand and heated. The heating may be performed, for example, by placing the polymerization vessel containing the material in a water bath or oil bath at a predetermined temperature, or by placing it in a predetermined temperature atmosphere. In the method of the present invention, since the polymerization is started from the central portion and / or the peripheral portion, bubbles are likely to be generated due to volume shrinkage during the polymerization. This is because the supply of the monomer is stopped due to the increase in viscosity accompanying the polymerization of the monomer by heating the polymerization vessel, but since the polymerization of the monomer is difficult to occur by polymerization at a low temperature, the viscosity does not increase, Since the supply can be maintained, the generation of bubbles is suppressed. In high temperature polymerization, the convection of the polymerization solution itself and the thermal storage effect runaway caused by the polymerization heat generated by the polymer itself are likely to occur, so the formation of a stable front is hindered, and the refraction changes continuously. Since a rate distribution cannot be obtained, it is desirable to polymerize at a lower temperature. The heating temperature in the method of the present invention is 60 ° C. or lower, preferably 50 ° C. or lower, particularly preferably 45 ° C. or lower.

  By heating the polymerization vessel, heat is conducted from the outside of the vessel to the inside of the vessel, and the heat reaches the center of the vessel and is stored in that portion. Here, the center of the container means a point where the container is equidistant from all points on the surface of the container, or a point where the surface of the container is symmetrical. Polymerization is theoretically initiated at the center of the polymerization vessel because heat applied from the outer surface of the vessel is conducted at a constant rate in the vessel. However, heat is not always stored accurately in the center of the container depending on the shape of the container and the heating method, and the polymerization is started near the center of the container. In this specification, the container central portion refers to a portion near the center of the container defined above.

  At this time, when the concentration of the polymer is low, that is, when the viscosity of the mixed solution of the monomer and the polymer is low, the center of the container reaches a certain temperature due to heat storage, and the polymerization is started at the center of the container. On the contrary, when the concentration of the polymer is high, that is, when the viscosity of the mixed solution of the monomer and the polymer is high, the heat from the periphery of the polymerization vessel is difficult to be transmitted to the center. Polymerization is started at the peripheral portion, and the polymerization proceeds from the peripheral portion to the central portion. In addition, when the polymer concentration is medium, heat is stored in the central portion, and at the same time, the temperature in the peripheral portion increases. For this reason, polymerization is initiated at both the center and the periphery of the vessel. The concentration of the polymer when the polymerization is initiated at both the center and the periphery of the container varies depending on the monomer used and the type of polymer, but the polymer is 4% to 30% by weight, preferably 6% by weight, based on the monomer. -15% by weight, more preferably 6-12% by weight. For example, when methyl methacrylate is used as the monomer and a high molecular weight polymer of polyalphamethylstyrene is used as the polymer, the amount is about 6% by weight, methyl methacrylate and benzyl methacrylate are used as the monomer, and polymethyl methacrylate is used as the polymer. When used, it is about 10% by weight.

  When the central part of the container or the peripheral part of the container reaches a certain temperature due to heat conduction or heat storage, polymerization is started at that part. As described above, the temperature at which the polymerization is initiated can be appropriately adjusted by selecting a polymerization initiator having a specific 10-hour half-life temperature. For example, a polymerization initiator having a 10-hour half-life temperature of 20 ° C. to 70 ° C. may be used.

  When polymerization is started at the center or the periphery of the container and a polymer is formed, the front of the polymer is formed, and polymerization proceeds while the front proceeds from the container center to the inner wall of the polymerization container or from the container periphery to the container center. Go ahead. Keep the temperature constant until polymerization is complete inside the vessel. The time until the polymerization is completed is several hours to several days although it varies depending on the shape of the container and the size of the container.

  As described above, since the polymerization is started from the central portion of the polymerization vessel or the peripheral portion of the polymerization vessel, the polymerization initiation site is determined by the shape of the vessel, and the polymerization initiation site, that is, the portion having the maximum or minimum refractive index becomes the desired portion. Thus, the container shape can be designed as appropriate.

  Although the refractive index distribution type optical transmission body in which the refractive index gradually changes from the central axis can be obtained by the production method of the present invention, the refractive index distribution can be changed by changing the type of the monomer and the low molecular compound used as described above. Control is possible, and an optical transmission body having a desired refractive index distribution can be obtained.

  The refractive index distribution type optical transmission body obtained by the production method of the present invention can be formed by using a polymerization vessel having a desired shape without being processed, and a polymerization vessel having an appropriate shape can be formed. It is possible to obtain an optical transmission body having a desired shape by using and processing. For example, the optical transmission body obtained by the method of the present invention can be polished as a base material and processed into a lens shape, or can be stretched and used as an optical fiber. The gradient index optical transmitter manufactured by the method of the present invention can be used as an optical fiber, a spectacle lens, a contact lens, or the like.

Furthermore, according to the method of the present invention, it is possible to produce an optical transmission body having an arbitrary shape and an arbitrary refractive index distribution. In particular, when the polymerization is started from the central portion and the peripheral portion of the polymerization vessel, an optical transmission body having a large difference in refractive index between the central portion and the peripheral portion or a polymer having a cladding layer can be manufactured. An optical transmission body having a large refractive index difference between the central portion and the peripheral portion and further including a cladding layer has little optical transmission loss even in a bent state, and is useful as an optical fiber or an image transfer device. An optical transmission body having a large refractive index difference can be used even in a thin disk state, and is useful for manufacturing a thin lens. Furthermore, an intraocular lens whose refractive index difference simulates a crystalline lens of an animal, particularly a human, can be produced. In order to fabricate intraocular lenses, it is necessary to use a biocompatible material, and since the refractive index is as low as 1.3 to 1.4, a monomer or polymer having a low refractive index when polymerized and a low molecular compound having a low refractive index are used. There is a need. A monomer that satisfies these requirements is hydroxyethyl methacrylate, a polymer is MPC, and a low molecular weight compound is H ₂ O. The shape and refractive index distribution of the crystalline lens are known, and the shape and refractive index distribution of the intraocular lens can be designed in accordance with, for example, the description of Liu Longki et al., Optics 30, 6 (2001) 407-413.

  Furthermore, the present invention provides a method for producing an optical transmission body that is long in the axial direction by tilting the polymerization container when performing frontal polymerization in the polymerization container by the above method, and the refractive index of the optical transmission body. It includes a method of producing an optical transmission body in which the central axis (center) of the distribution is shifted from the central axis of the polymerization vessel. Here, the central axis of the polymerization container means a line where the container is equidistant from all points on the surface of the container, or a line where the surface of the container is symmetrical. The center of the optical transmission body means a line having the highest refractive index or a lowest refractive index in the refractive index distribution type optical transmission body.

In this case, a low molecular compound (low molecular dopant) may be used instead of the polymer. Low molecular compounds that can be used include, but are not limited to, propionic acid-based esters, isobutyric acid-based esters, phthalic acid-based esters, and adipic acid-based esters in view of compatibility with polymer materials. The molecular weight of the low molecular weight compound is larger than the molecular weight of the monomer used. Examples of the low molecular weight compound include methyl isobutyrate (1.384), methyl caprylate (1.417), H ₂ O (1.333), and the like. The refractive index is shown in parentheses.

  The refractive index of the low molecular weight compound is different from the refractive index shown when the monomer used is polymerized to become a polymer, but may be larger or smaller than the refractive index of the polymer obtained by polymerizing the monomer. However, in order to use it as an optical fiber, an artificial intraocular lens, etc., the refractive index of a low molecular compound needs to be smaller than the refractive index of a polymer made of a monomer. When it is small, a refractive index distribution type optical transmission body in which the refractive index decreases from the central axis toward the outside is obtained, and when large, the refractive index distribution type optical transmission body in which the refractive index increases from the central axis toward the outside is obtained. Is obtained. By changing the type of monomer used, the type of low molecular weight compound, and the mixing ratio of the monomer and low molecular weight compound, an optical transmission body having a desired refractive index distribution can be produced. At this time, the type and mixing ratio of the monomer and low molecular compound to be used should be determined in consideration of the refractive index, solubility, ease of polymerization of the monomer, and the like of the high molecular compound and low molecular compound obtained by polymerizing the monomer. Can do.

  Moreover, the low molecular weight compound may include a plurality of types. Production of an optical transmission body by polymerization using a low molecular weight compound can be performed according to the description of WO 2004/068202.

  An optical transmission body that is long in the axial direction is obtained by a long front formed in frontal polymerization. In the optical transmission body, the length of the optical transmission body obtained when polymerization is performed with the polymerization container vertical in the axial direction is about 50% of the axial length (height) of the polymerization container. Is 70% or more, preferably 80% or more. The polymerization vessel may be tilted by 10 degrees to 90 degrees with respect to the vertical direction.

  For the optical transmission body whose central axis (center) is deviated from the central axis of the polymerization vessel, a polymerization inhibitor or a polymerization inhibitor may be added to the material for starting the polymerization. By adding a polymerization inhibitor or a polymerization inhibitor, the polymerization can be delayed, and accordingly, the front formation is delayed in the frontal polymerization, so that the center of the optical transmission body can be shifted. Examples of the polymerization polymerization inhibitor include hydroquinone polymerization inhibitors such as hydroquinone, hydroquinone monomethyl ether and parabenzoquinone, 2,2-diphenyl-1-picrylhydrazyl and nitrobenzene. The polymerization inhibitor may be added in an amount of 0.0001 to 0.002% by weight based on the monomer. Further, when the polymerization is performed, the polymerization vessel may be inclined at 10 to 90 degrees, preferably 45 to 90 degrees, more preferably 75 degrees or more, and particularly preferably 90 degrees with respect to the vertical direction. In this case, the front formation in the frontal polymerization is shifted downward from the central axis of the polymerization vessel, and the refractive index on the upper side of the optical transmission body is reduced.

  A lens having a non-uniform refractive index can be produced from the optical transmission member whose center is shifted without being scraped, and the position of the focal point can be adjusted. For example, it can be used for producing a bifocal lens.

  The refractive index distribution of the gradient index optical transmitter obtained by the method of the present invention can be roughly predicted by measuring the refractive index distribution constant and the effective field radius ratio. Furthermore, in order to measure the refractive index distribution over the entire diameter of the optical transmission body, non-destructive measurement methods such as transverse interference pattern method, backscatter pattern method, convergence method, spatial filtering method, near field pattern method, A destructive measurement method such as an interference pattern method may be used. Among these, the transverse interference pattern method is preferable for measuring an optical transmission body having a diameter of about 1 to 2 mm such as an optical fiber in consideration of measurement time, measurement accuracy, ease of sample preparation, ease of ellipse deformation correction, etc. The longitudinal interference pattern method is preferable for measuring an optical transmission body having a diameter of about 10 to 20 mm. An interference microscope may be used to measure the refractive index of the optical transmission body. For example, an interference phase contrast microscope Interphako manufactured by Carl Zeiss aus jena, East Germany may be used as the interference microscope.

  The present invention will be specifically described by the following examples, but the present invention is not limited to these examples.

Example 1 Production of Refractive Index Distribution Type Optical Transmitter Using Polyalphamethylstyrene as Polymer As a monomer, methyl methacrylate (MMA, MMA, Wako Pure Chemical Industries, Ltd.) was used. In order to remove a polymerization inhibitor contained in a small amount as a stabilizer in commercially available MMA, various washing steps have been performed. However, polymerization inhibitors called hydroquinone and hydroquinone monomethyl ether vaporize MMA when MMA is distilled under reduced pressure. Under such conditions, it was confirmed that it was present in the liquid phase and did not vaporize. Therefore, the main fraction (46 to 47 ° C./760 mmHg) obtained directly under reduced pressure without washing the commercially available MMA was used for the polymerization as purified MMA.

  Polymers include polyalphamethylstyrene, low (Poly (α-methylstyrene), low: PαMS, low, Aldrich Chemical Company) and polyalphamethylstyrene, high (Poly (α-methylstyrene), high: PαMS, high, Aldrich). Chemical Company). The difference between high and low is the molecular weight. These used the commercial thing as it was.

  Table 1 shows the molecular weight and refractive index of the monomers and polymers used.

  As a polymerization initiator, 2,2'-azobisisobutyronitrile (AIBN, Wako Pure Chemical Industries, Ltd.) was used. A commercially available polymerization initiator was used as it was.

Production of GRIN rod lens As described above, MMA purified as a monomer, PαMS, low or PαMS, high as a polymer, and AIBN as a polymerization initiator were used. First, MMA and PαMS were mixed and dissolved by ultrasonic degassing for about 1 hour. AIBN was added to this solution, and after substituting with nitrogen for 1 minute, it was deaerated over 30 minutes by ultrasonic deaeration. This was put into a glass tube having an inner diameter of 12 mm and polymerized in a 45 ° C. constant temperature bath (oil bath) for about 24 hours. AIBN was used at 2 wt% with respect to MMA.

The bulk lens taken out from the glass tube was cut, the surface was polished, and it was confirmed how it looks through the lens. Thereafter, a measurement sample having a thickness of 1 to 2 mm was prepared, and the refractive index distribution was measured using an interference microscope. A schematic diagram of the interference microscope is shown in FIG. The light emitted from the light source (9) passes through the slit (7) and the condenser lens (8) and proceeds to the sample (4). This sample is covered with an immersion liquid and set in a glass cell (5), and this glass cell is placed on a stage (6). For the immersion liquid, use a liquid paraffin-based transparent liquid (n _d = 1.473 / 23 ° C) and Nikon immersion oil (n _d = 1.515 / 23 ° C) that does not attack the sample and n _d = 1.492. It was. Light exiting the sample passes through the objective lens (3) and enters the interferometer. Inside, the light beam is divided into two by the prism I (Pr-I), and one (left side) directly goes to the prism II (Pr-II) and reaches the eyepiece lens (1). The other (right side) is directed to the prism II by the sharing device (2) with a deviation of ΔY _p perpendicular to the optical axis. Although the two light beams are synthesized by the prism II, the deviation ΔYp between the two is held even in front of the eyepiece. Therefore, the rays separated by ΔY _p here cause interference with each other, resulting in interference fringes.

  In this way, when using the Interphako Interferometer, the reference sample is not required, and the light beam from one sample is targeted, so there is no need to adjust the optical axis during measurement and the operation is simple. Measurement accuracy is also good.

The refractive index distribution was performed by the longitudinal interference pattern method. There are two types of longitudinal interference pattern methods, the total-splitting method and the partial-splitting method, and the partial-splitting method is used in this embodiment. As shown in the left diagram of FIG. 3A, the image is moved slightly compared to the sample by the sharing device (2), that is, shifted much smaller than the sample diameter (ΔY _p << 2R _p ). This method has an advantage that measurement is possible even when a sample to be measured is somewhat large. On the other hand, in the Total-splitting method, which is another method of the longitudinal interference pattern method, the image is shifted larger than the diameter of the sample as shown in the left diagram of FIG. 3B (ΔY _p > 2R _p ). This method is suitable when the sample to be measured is small, for example very thin fibers.

The actually observed interference fringes are shown in the right diagrams of FIGS. 3A and 3B for each case. The circled portion in the figure is the portion of the sample placed in the glass cell (5), and the fringes seen in the horizontal direction on the left and right are interference fringes. Since the left and right portions of the sample are interference fringes due to light that has passed through the portion of the immersion liquid containing the sample, the refractive index does not change and is linear. In addition, the interference fringes passing through the center of the sample are referred to as reference interference fringes. The distance D between the interference fringes corresponds to a shift of one wavelength of the measurement light. In this way, in the case of the partial-splitting method, the light that actually interferes and becomes a fringe is measured by light beams that have passed through different positions by the sharing width of the sample being measured. The image seen inside is related to the refractive index as shown in FIG. 4A. In this figure, the portion where the diagonal lines do not overlap indicates the difference in refractive index that causes the interference fringes to shift. At this time, the deviation of the interference fringe from the reference interference fringe is _defined as dr (y _p ).

In contrast, in the case of the Total-splitting method, as shown in FIG. 4B, the interference between the light passing through the immersion liquid and the light passing through only the sample is measured as a stripe. For this reason, the interference fringe pattern has the largest fringe shift on the central axis. At this time, the deviation of the interference fringe from the reference interference fringe is assumed to be ΔR (Y _p ).

Partial-splitting method of displacement of the interference fringes ΔR and (Y _p) between the displacement of the interference fringes of Total-splitting method R (Y _p), when the [Delta] Y _p and sharing width, the following formula (I) There is a relationship.

The change in the refractive index at each part of the GRIN rod is calculated using ΔY _p , D by measuring the deviation ΔR (Y _p ) of this interference fringe pattern from the reference interference fringe and its position Y _p. .

  By the longitudinal interference pattern method, the change in refractive index from the center is obtained as follows.

となる。Partial-splitting法では、屈折率分布がn(y)とn(y+Δy)の部分を通過する光線が波面のずれを生ずるので、そのずれの大きさは、

となる。ここで、干渉縞のずれΔRと基準干渉縞１波長分のずれDと光線の波長λとの間には、

の関係がある。 When a light beam passes through a flat plate having a refractive index distribution n (y) and having a thickness t, the light beam has traveled an optical path of n (y) · t. Since n = 1 in vacuum, the deviation of the wavefront from the light beam that has advanced this vacuum by t is

It becomes. In the partial-splitting method, since the light beam passing through the portions of the refractive index distribution n (y) and n (y + Δy) causes a wavefront shift, the magnitude of the shift is

It becomes. Here, between the interference fringe shift ΔR, the reference interference fringe shift D for one wavelength, and the light beam wavelength λ,

There is a relationship.

において以下の式が成り立つ。 If the refractive index at the reference point y ₀ is n (y ₀ ) and the interference fringe shift is ΔR (y ₀ ), then each point

The following equation holds.

となり、中心からの屈折率の変化が求められる。 Taking these sums together,

Thus, a change in refractive index from the center is required.

  The portion of the sample obtained in this example in a steady state was cut into a disk shape having a thickness of about 3 mm, both end surfaces were polished, and a measurement sample having a thickness of about 1 to 2 mm was prepared. And measured. In this study, n (y) = 0 because we wanted to obtain the refractive index distribution from the center to the periphery of the GRIN rod. In actual measurement, about 10 points were measured for one sample, and the refractive index distribution over the entire rod area was obtained using the above relational expression. In this method, only the part of the actual sample length excluding the sharing width can be measured, but in this study, the sample length is about 10 to 20 mm, and the sharing width may be 0.05 mm. There was practically no problem.

  In the combination using MMA as the monomer and PαMS, low as the polymer, five concentrations of PαMS, low of 2 wt%, 4 wt%, 6 wt%, 8 wt% and 10 wt% with respect to MMA were prepared. The initiator was AIBN of 2 wt% with respect to MMA, and the polymerization was carried out in a constant temperature bath at 45 ° C.

  Table 2 shows the polymerization behavior in MMA-PαMS, low. When the concentration of PαMS, low is 2 wt% and 4 wt%, a front is formed in the center of the container, and the polymerization proceeds from the center to the periphery, but the concentration of PαMS, low is 6 wt%, 8 wt%, and 10 wt%. In the case of%, no front was formed at the center, and polymerization proceeded from the periphery toward the center.

  Further, FIGS. 5, 6 and 7 show that the polymerization is actually progressing at PαMS, low concentrations of 2 wt%, 6 wt% and 10 wt%. In FIG. 5, it can be seen that a front is formed at the center of the container (FIG. 5 (2)) and moves to the periphery of the container (FIG. 5 (4)). Polymerization proceeds at a stroke in about 3 minutes from the formation of the front to the periphery. In FIG. 6, the front part is not formed in the central part, and it seems that the polymerization proceeds from the peripheral part (particularly the right side) (FIGS. 6 (2) to (4)). Finally, FIG. 7 shows that the polymerization proceeds from the peripheral part (both left and right sides). Further, as apparent from FIGS. 6 and 7, the progress of polymerization is slower than that in FIG. In MMA-PαMS, low, a front is formed at the center, and when polymerization starts from the center (PαMS, low concentration is 2wt%, 4wt%), the polymerization proceeds rapidly and polymerization starts from the periphery. (PαMS, low concentration of 6 wt%, 8 wt%, 10 wt%), the polymerization proceeded slowly.

  This photo was taken and edited with a video camera, and it can be seen that the superposition is a movie, but it is difficult to understand if it is a still image. It is particularly difficult to understand how the polymerization proceeds from the peripheral part to the central part.

  FIG. 8 shows the refractive index distribution in MMA-PαMS, low. In this figure, the horizontal axis represents the normalized radius and the vertical axis represents the refractive index difference. Lenses with PαMS, low concentrations of 2 wt% and 4 wt% showed a distribution in which the refractive index increased from the center toward the periphery. The lens with a PαMS, low concentration of 6 wt% has a distribution in which the refractive index decreases from the center to the periphery when the normalized radius is 0 to 0.7, and increases when the normalized radius is 0.7 to 1.0. A lens with a PαMS, low concentration of 8 wt% and 10 wt% has a distribution in which the refractive index decreases from the center toward the periphery, and the shape of the refractive index distribution differs depending on the concentration of PαMS, low.

  This is related to whether the polymerization is started from the center or the periphery. When a front is formed in the center and polymerization proceeds from the center to the periphery, PαMS, low is pushed to the periphery. Therefore, PαMS, low having a high refractive index is a composition having a large amount in the peripheral portion, and the refractive index is higher in the peripheral portion than in the central portion. On the other hand, when polymerization is started from the peripheral part, it is considered that PαMS, low is pushed to the central part. PαMS, low has a large composition in the center, and the center has a higher refractive index than the periphery.

  The difference in refractive index between the center and the periphery of the lens is the largest for the lens with PαMS, low density of 2 wt%, and conversely, the difference in the refractive index is the smallest for the lens with PαMS, low density of 6 wt%. was.

  Even in the case of using a combination of MMA for the monomer and PαMS, high for the polymer, the concentration of PαMS, high is 2 wt%, 4 wt%, 6 wt%, 8 wt%, 10 wt% with respect to the MMA as in the case of using PαMS, low. Five types were produced. The initiator was AIBN of 2 wt% with respect to MMA, and the polymerization was carried out in a constant temperature bath at 45 ° C.

  Table 3 shows the polymerization behavior in MMA-PαMS, high. When the concentration of PαMS, high was 2 wt% and 4 wt%, a front was formed at the center, and polymerization proceeded from the center toward the periphery. When the concentration of PαMS, high was 6 wt%, the polymerization was started from the peripheral part, but then the front was formed in the central part and the front moved to the peripheral part. When the concentration of PαMS, high was 8 wt% or 10 wt%, no front was formed in the central portion, and polymerization proceeded from the peripheral portion toward the central portion.

  Further, FIGS. 9, 10 and 11 show the state in which the polymerization actually progresses at concentrations of PαMS, high of 2 wt%, 6 wt% and 10 wt%. From FIG. 9, it can be seen that the front is formed at the center (FIG. 9 (2)) and moves to the periphery (FIG. 9 (4)). The front shape is elongated compared to the case where PαMS, low concentration is 2 wt%. Since the amount of the mixed solution containing the monomer, polymer and initiator injected into the polymerization vessel is constant, the front shape may change depending on the polymer used. In FIG. (10), the polymerization is started from the peripheral part (right side) (FIGS. 10 (2) to 10 (4)), the front is formed in the central part (FIG. 10 (5)), and moves to the peripheral part. (FIG. 10 (6)). In FIG. 11, it can be seen that the polymerization proceeds from the peripheral part (both left and right sides). Similarly to the case of MMA-PαMS, low, the time taken from the formation of the front to the peripheral portion is several minutes, and the polymerization proceeds rapidly.

  FIG. 12 shows the refractive index distribution in MMA-PαMS, high. Lenses with PαMS, high concentrations of 2 wt% and 4 wt% have a distribution in which the refractive index increases from the center toward the periphery. A lens with a PαMS, high concentration of 6 wt% has a distribution in which the refractive index increases from the center toward the periphery when the normalized radius is 0 to 0.7, and decreases toward the periphery when the normalized radius is 0.7 to 1.0. It was. Lenses with a PαMS, high concentration of 8 wt% and 10 wt% have a distribution in which the refractive index decreases from the center to the periphery, and the shape of the refractive index distribution differs depending on the concentration of PαMS, high as with MMA-PαMS, low. When the concentration of PαMS, high is 2 wt% and 4 wt%, PαMS, high is pushed to the periphery, and the composition of PαMS, high is high in the periphery, conversely, the concentration of PαMS, high is 8 wt%, 10 wt% In this case, it is considered that PαMS, high was pushed to the center and the composition was rich in PαMS, high in the center. When the concentration of PαMS, high is 6 wt%, PαMS, high is first pushed from the periphery to the center, and then pushed to the periphery by the movement of the front, so it rises toward the periphery as shown in FIG. It seems that the refractive index distribution decreased.

  Regarding the refractive index difference, the lens with the PαMS, high density of 2 wt% was the largest, and conversely the lens with the PαMS, high density of 8 wt% was the smallest.

Measurement of temperature change in the system The spontaneous frontal polymerization method is based on three factors: thermal storage effect, gel effect, and thermal diffusion. Since these three factors are related to heat, it is important to measure temperature changes in the system. Therefore, the temperature inside the system was measured using a thermocouple. Thermocouples were attached to two locations, the central portion and the peripheral portion of the polymerization vessel, and two temperatures were measured at 1 minute intervals. An outline of the apparatus is shown in FIG.

  FIG. 14 shows the measurement results of the temperature change in the system when the concentration of PαMS, low is 2 wt%. Until about 90 minutes after the start of polymerization, the temperature at the center and the periphery of the container remained almost unchanged. Thereafter, a temperature difference gradually occurred, and after 200 minutes, the temperature difference between the central portion and the peripheral portion became about 2 ° C. Around 220 minutes, a front was formed in the center, and the temperature of the entire system, especially the center, rose rapidly. When the front reached the periphery, the temperature in the system dropped.

  Next, FIG. 15 shows the measurement results of the temperature change in the system when the concentration of PαMS, low is 10 wt%. The temperature change was quite different from that in FIG. From the start of polymerization until 50 minutes, there is almost no temperature difference between the central part and the peripheral part. Thereafter, the temperature of the central part increased by about 1 ° C., and the temperature became the highest in both the central part and the peripheral part 315 minutes after the start of polymerization. The temperature at this time was 51.5 ° C. at the center and 47.3 ° C. at the periphery, and the temperature did not explosively rise as shown in FIG.

  When the concentration of PαMS, low is 2 wt%, the temperature rose explosively when the front was formed, indicating that the polymerization proceeded at once. On the other hand, when the concentration of PαMS, low is 10 wt%, it can be said that the polymerization is proceeding slowly because the temperature did not rise so much and the way of the rise was slow.

  From the above examples, the following was found regarding the difference in polymerization behavior depending on the concentration of PαMS.

  As shown in the examples, the polymerization behavior varies depending on the concentration of PαMS. From Tables 1 and 2, when PαMS, low and PαMS, high were used, three types of polymerization behavior were observed depending on the concentration. Specifically, one is a type in which a front is formed in the center and polymerization proceeds toward the periphery, the second is a type in which polymerization proceeds from the periphery to the center, and finally polymerization from the periphery. However, this is a type in which a front is formed at the center and polymerization proceeds toward the periphery. The difference in the polymerization behavior depending on the concentration of PαMS seems to be caused by the difference in viscosity of the MMA-PαMS mixed solution. The details are divided into three types below.

(a) A type in which a front is formed in the central part and polymerization proceeds in the peripheral part. This type is a polymerization behavior observed when the concentration of PαMS is low, that is, when the viscosity of the MMA-PαMS mixed solution is low.

  Since the viscosity of the system is low for a while after the start of polymerization, convection occurs inside the system. Therefore, there is no temperature difference between the peripheral part and the central part. Thereafter, the conversion rate of the entire system increases and the viscosity of the system increases, so that convection hardly occurs. As a result, the reaction heat is stored, and the temperature of the central part is higher than that of the peripheral part. Due to this temperature gradient, a front is formed in the center and polymerization proceeds in the periphery. As apparent from FIG. 14, no temperature difference has occurred between the peripheral portion and the central portion for a while after the start of polymerization.

(b) Type in which polymerization proceeds from the peripheral part to the central part This type is a polymerization behavior observed when the concentration of PαMS is high, that is, when the viscosity of the MMA-PαMS mixed solution is high.

  Since the viscosity of the system is high from the beginning, convection inside the system is unlikely to occur. For this reason, the heat from the oil bath enters the peripheral part, but it is difficult to transfer heat to the central part. However, since convection hardly occurs inside the system, the reaction heat is easily stored in the center. Under these conditions, it is considered that the element in which heat enters from the oil bath in the peripheral part has a stronger influence on the polymerization than the element in which the polymerization heat is stored in the central part. Therefore, it is considered that the polymerization progressed from the peripheral part. Also in FIG. 15, the temperature in the peripheral portion was not higher than that in the central portion, but the temperature difference between the peripheral portion and the central portion is smaller than that in FIG. 14. This seems to be due to the two factors mentioned above.

(c) Type in which polymerization proceeds from the peripheral part, but a front is formed in the central part. This type was observed only when the concentration of PαMS, high was 6 wt%. This is because the viscosity of the system is lower than in the case of (b), and is considered to be a result of both the element in which the polymerization heat is stored in the central part and the element in which the heat enters from the oil bath in the peripheral part. These two factors may have affected the polymerization to the same extent.

  Furthermore, the following was found from the above examples regarding the shape of the refractive index distribution.

  The shape of the refractive index distribution varies depending on the concentration of PαMS from the results of FIGS. That is, it is related to whether the polymerization proceeds from the central portion or the peripheral portion, that is, whether a front is formed at the central portion.

  If the polymerization proceeds in the process where the front is formed in the central part and the front is moved to the peripheral part, the refractive index distribution should be formed by the refractive index distribution forming method.

  On the other hand, when polymerization proceeds from the peripheral part to the central part, PαMS is pushed in the central direction. An outline is shown in FIG. First, a gel layer is formed around the periphery. As the polymerization proceeds, the gel layer spreads in the center direction. Here, since PαMS having a large molecular size is difficult to diffuse into the gel layer, the composition has a large amount of PαMS at the center. As a result, it is considered that the refractive index decreases from the center to the periphery. Unlike the refractive index profile formation method, it seems that something similar to the interfacial gel polymerization method has occurred.

  When MMA is used as the monomer and PαMS is used as the polymer, it is possible to produce lenses having convex and concave distribution shapes by changing the concentration of PαMS.

  Furthermore, the following was found for the refractive index difference of the optical transmission body obtained from the examples.

The refractive index difference (Δn _low ) of the MMA-PαMS, low lens is summarized in Table 4, and the refractive index difference (Δn _high ) of the MMA-PαMS, high lens is summarized in Table 5. Here, the refractive index difference is obtained by subtracting the minimum refractive index from the maximum refractive index of the distribution. Arranged from the larger Δn _low , 2wt%>4wt%>8wt%>10wt%> 6wt%, and arranged from the larger Δn _high , 2wt%>10wt%>6wt%>4wt%> 8wt% Become.

  On the other hand, from Tables 1 and 2, it can be said that the concentration of PαMS is about 6 wt% at the boundary between whether the polymerization proceeds from the central portion or the peripheral portion. That is, when the concentration of PαMS is 6 wt%, it seems that there are both elements in which polymerization proceeds from the central part and elements in which polymerization proceeds from the peripheral part. The effect of pushing PαMS toward the center and the effect pushing toward the periphery try to form a refractive index distribution in opposite directions, so that cancellations occur and the difference in refractive index is considered to be small.

  Based on the above thoughts, the difference in refractive index due to the concentration of PαMS will be discussed. Since the polymerization behavior varies depending on the concentration of PαMS, (a) a comparison of 2 wt%, 4 wt%, and 6 wt% and (b) a comparison of 6 wt%, 8 wt%, and 10 wt% are performed.

Comparison of PαMS concentrations 2wt%, 4wt%, 6wt%
When the concentration of PαMS is 6 wt%, the difference in refractive index seems to be small for the reason described above. When the concentration of PαMS is 4 wt%, there are both an element in which polymerization proceeds from the central part and an element in which polymerization proceeds from the peripheral part, but since the front is formed at the central part, the polymerization proceeds from the central part. The element is stronger. Therefore, it is considered that the refractive index difference is larger than the case of 6 wt%. Finally, when the concentration of PαMS is 2 wt%, the element that polymerizes from the center is strong and the element that polymerizes from the periphery is weak compared to the case of 4 wt%. It seems that the refractive index difference is large. In summary, Δn is considered to be in the order of 2 wt%> 4 wt%> 6 wt%. In the measurement results, Δn _low was 2 wt%> 4 wt%> 6 wt%, and Δn _high was 2 wt%> 6 wt%> 4 wt%.

Comparison of PαMS concentrations 6wt%, 8wt%, 10wt%
When the concentration of PαMS is 8 wt%, compared to the case of 6 wt%, the element that polymerizes from the center is weak and the element that polymerizes from the periphery is strong, so the difference in refractive index is 6 wt%. It seems big. Next, when the concentration of PαMS is 8 wt%, the element in which the polymerization proceeds from the peripheral portion is strong, so it is considered that the refractive index difference is the largest among these three types. In summary, Δn is considered to be in the order of 10 wt%> 8 wt%> 6 wt%. In the measurement results, Δn _low was 8 wt%> 10 wt%> 6 wt%, and Δn _high was 10 wt%> 6 wt%> 8 wt%.

  Of course, the difference in refractive index is related to the amount of contained PαMS, and the refractive index distribution varies depending on the position of the lens. Conceivable.

Example 2 Production of Light Transmitter Using Polymethyl Methacrylate as Polymer Polymerization was conducted in the same manner as in Example 1 using methyl methacrylate and benzyl methacrylate as monomers and polymethyl methacrylate as a polymer. The polymerization tube used was a Pyrex glass test tube with an outer diameter of 18 mm and an inner diameter of 15 mm, and the test tube was kept vertical during the polymerization. The polymerization temperature is 45 ° C. Monomers used were 8.0 g of MMA, 2.0 g of BzMA, 1.0 g of Poly (MMA) (10 wt% based on the monomer), and 0.2 g of AIBN (2 wt% based on the monomer) was used as a polymerization initiator. After mixing these, nitrogen substitution for 30 seconds and ultrasonic degassing for 20 minutes were performed, followed by polymerization in an oil bath at 45 ° C.

  FIG. 17 shows a refractive index distribution measured by an interference microscope after polishing a cylindrical sample obtained in this example into a disk shape. As shown in FIG. 17, a large refractive index distribution was obtained at the center and the periphery.

Example 3 Production of an optical transmission body in which the central axis of the optical transmission body is deviated from the central axis of the polymerization vessel
BzMA-EHMA copolymerization A Pyrex glass test tube having an outer diameter of 18 mm and an inner diameter of 15 mm was used as the polymerization tube, and the test tube was kept horizontal (laid at 90 degrees) during the polymerization. The polymerization temperature is 44 ° C. The monomers used were 12.0 g of benzyl methacrylate (BzMA), 3.0 g of ethylhexyl methacrylate (EHMA), 0.15 g of ethylene glycol dimethacrylate (EGDMA) (1 wt% based on the monomer) as a crosslinking agent, and azobisiso as a polymerization initiator. Butyronitrile (AIBN) 0.3 g (2 wt% with respect to the monomer) and monomethyl ether hydroquinone (MEHQ) (about 1 ppm) were used as a polymerization inhibitor. After mixing these, nitrogen substitution for 30 seconds and ultrasonic degassing for 20 minutes were performed, followed by polymerization in an oil bath at 44 ° C.

  As a result of polymerization under the above conditions, a front was generated at a position shifted from the center of the polymerization tube.

  The front was confirmed 2 hours after the start of polymerization. The front reached the lower side of the test tube 5 minutes after the front formation, and reached the upper side 10 minutes later.

  A sample obtained by this experiment was polished into a disk shape, and the refractive index distribution measured by an interference microscope is shown in FIGS.

  FIG. 18 shows a cross section of the produced cylindrical lens, and the direction (1) in the figure is the side on which polymerization was performed. The measured cross sections were represented by (1)-(2), (3)-(4) and (5)-(6), and the respective refractive index distribution data are shown in FIGS.

  As shown in FIGS. 19 to 21, a lens whose center was shifted was obtained.

BzMA-MMA copolymerization A Pyrex glass test tube having an outer diameter of 15 mm and an inner diameter of 12 mm was used as the polymerization tube, and the test tube was kept horizontal during the polymerization. The polymerization temperature was 43 ° C. The monomers used were BzMA 12.0 g and MMA 3.0 g, AIBN 0.3 g (2 wt% based on the monomer) was used as a polymerization initiator, and MEHQ (about 10 ppm) was used as a polymerization inhibitor. After mixing these, nitrogen substitution for 30 seconds and ultrasonic degassing for 20 minutes were performed, followed by polymerization in an oil bath at 44 ° C.

  A cylindrical sample obtained by this experiment is polished into a disk shape, and a refractive index distribution measured by an interference microscope is shown below.

  FIG. 22 shows a cross section of the manufactured lens, and the direction of (1) in the figure is the side on which the polymerization was performed. The measured cross sections are represented by (1)-(2), (3)-(4) and (5)-(6), and the respective data are shown in FIGS.

  As shown in FIGS. 23 to 25, a lens whose center was shifted was obtained.

It is a figure which shows refractive index profile formation by spontaneous frontal polymerization. It is the schematic of an interference phase contrast microscope. It is a figure which shows the principle of refractive index distribution measurement by the vertical direction interference pattern method. A is a partial splitting method, and B is a total splitting method. It is a figure which shows the interference pattern observed with an interference microscope. A is a pattern of the partial splitting method, and B is a pattern of the total splitting method. It is a figure which shows the mode of progress of superposition | polymerization at the time of using MMA-P (alpha) MS, low as a polymer (2 wt%). It is a figure which shows the mode of progress of superposition | polymerization at the time of using MMA-P (alpha) MS, low as a polymer (6 wt%). It is a figure which shows the mode of advancing of superposition | polymerization when MMA-P (alpha) MS, low is used as a polymer (10 wt%). It is a figure which shows the refractive index distribution of the optical transmission body produced using MMA-P (alpha) MS, low as a polymer. It is a figure which shows the mode of progress of superposition | polymerization when MMA-P (alpha) MS, high is used as a polymer (2 wt%). It is a figure which shows the mode of advancing of superposition | polymerization when MMA-P (alpha) MS, high is used as a polymer (6 wt%). It is a figure which shows the mode of advancing of superposition | polymerization when MMA-P (alpha) MS, high is used as a polymer (10 wt%). It is a figure which shows the refractive index distribution of the optical transmission body produced using MMA-P (alpha) MS, high as a polymer. It is a figure which shows the outline of the system temperature measuring apparatus using a thermocouple. It is a figure which shows the system temperature change measurement result in case the density | concentration of P (alpha) MS, low is 2 wt%. It is a figure which shows the system temperature change measurement result in case the density | concentration of P (alpha) MS, low is 10 wt%. In the method of this invention, it is the figure which showed a mode that frontal polymerization progressed from a peripheral part toward a center part. It is a figure which shows the refractive index distribution of the optical transmission body produced using methyl methacrylate and benzyl methacrylate as a monomer, and polymethylmethacrylate as a polymer. It is sectional drawing which shows a measurement location in the optical transmission body produced by shifting the center by BzMA-EHMA copolymerization. FIG. 19 is a diagram showing a refractive index distribution measured in the (1)-(2) direction in the cross-sectional view of FIG. 18. FIG. 19 is a diagram showing a refractive index distribution measured in the (3)-(4) direction in the cross-sectional view of FIG. 18. FIG. 19 is a diagram showing a refractive index distribution measured in the (5)-(6) direction in the cross-sectional view of FIG. 18. It is sectional drawing which shows a measurement location in the optical transmission body produced by shifting the center by BzMA-MMA copolymerization. FIG. 23 is a diagram showing a refractive index distribution measured in the (1)-(2) direction in the cross-sectional view of FIG. 22. FIG. 23 is a diagram showing a refractive index distribution measured in the (3)-(4) direction in the cross-sectional view of FIG. 22. FIG. 23 is a diagram showing a refractive index distribution measured in the (5)-(6) direction in the cross-sectional view of FIG. 22.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Eyepiece 2 Sharing device 3 Objective lens 4 Sample 5 Glass cell 6 Stage 7 Slit 8 Condenser lens 9 Light source 10 Thermocouple 11 Measurement system 12 Computer 13 Monomer 14 Front

Claims (17)

  In a method of manufacturing a refractive index distribution type optical transmission body in which the refractive index gradually changes from the central axis, a monomer, a polymer and a polymerization initiator are filled in a polymerization vessel, the polymerization vessel is heated, and the amount of polymer added is adjusted A refractive index distribution type optical transmission characterized in that one or both of a front formation polymerization reaction from the container center to the container periphery and a front formation polymerization reaction from the container periphery to the container center proceeds. How to make a body.   In a method of manufacturing a refractive index distribution type optical transmission body in which the refractive index gradually changes from the central axis, a monomer, a polymer and a polymerization initiator are filled in a polymerization vessel, the polymerization vessel is heated, and the amount of polymer added is adjusted 2. The refractive index distribution type according to claim 1, wherein both the front formation polymerization reaction from the container center to the container periphery and the front formation polymerization reaction from the container periphery to the container center proceed. Of manufacturing an optical transmission body.   3. The method for producing a refractive index distribution type optical transmitter according to claim 2, wherein the polymer is contained in the polymerization vessel in an amount of 5 to 10% by weight based on the monomer.   The method for producing a refractive index distribution type optical transmitter according to any one of claims 1 to 3, wherein two or more types of monomers and / or polymers are filled in a polymerization vessel.   The manufacturing method of the refractive index distribution type optical transmission body according to claim 1, wherein the heating temperature is 50 ° C. or less.   The method for producing a refractive index distribution type optical transmitter according to claim 5, wherein the polymerization initiator has a 10-hour half-life temperature of 20 to 70 ° C.   The method for producing a refractive index distribution type optical transmitter according to claim 6, wherein the polymerization initiator is selected from the group consisting of organic peroxides, persulfates, and azo compounds.   The method for producing a refractive index distribution type optical transmitter according to any one of claims 1 to 7, wherein the monomer is methacrylic acid ester or acrylic acid ester.   The method for producing a refractive index distribution type optical transmitter according to any one of claims 1 to 8, wherein the polymer is selected from the group consisting of polyalphamethylstyrene.   The optical transmission body having a length exceeding 50% of the height in the polymerization container is produced by tilting the polymerization container from 10 degrees to 90 degrees with respect to the vertical direction. A method of manufacturing a refractive index distribution type optical transmission body.   The method for producing a refractive index distribution type optical transmitter according to claim 10, wherein an optical transmitter having a length of 75% or more of the height in the polymerization vessel is prepared.   Further, a polymerization inhibitor or a polymerization inhibitor is added to the polymerization container, and the polymerization container is tilted from 10 degrees to 90 degrees with respect to the vertical direction to produce an optical transmission body whose center is deviated from the central axis of the polymerization container. A method for manufacturing a refractive index distribution type optical transmitter according to any one of claims 1 to 9.   13. The method for producing a refractive index distribution type optical transmitter according to claim 12, wherein the polymerization container is tilted from 75 degrees to 90 degrees with respect to the vertical direction.   14. The refractive index distribution type optical transmitter according to claim 12, wherein the polymerization inhibitor is a hydroquinone compound or a derivative thereof, 2,2-diphenyl-1-picrylhydrazyl, or nitrobenzene. Method.   The method for producing a refractive index distribution type optical transmitter according to any one of claims 12 to 14, wherein the addition amount of the polymerization inhibitor is 0.0001 to 0.002 wt% with respect to the monomer.   The method for producing a refractive index distribution type optical transmitter according to any one of claims 10 to 15, wherein a propionic acid ester or an isobutyric acid ester is added as a low-molecular compound instead of the polymer.   An optical transmission body manufactured by the method for manufacturing a refractive index distribution type optical transmission body according to any one of claims 1 to 16.

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