JPH0250443B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a plastic light conduit with a refractive index gradient. It is conventionally known that a transparent body having a refractive index distribution in which the refractive index gradually decreases approximately in proportion to the square of the distance from the central axis acts as a convex lens. In such a transmission body, assuming that the refractive index of the central axis is NO, the refractive index N at a distance of X from the central axis is expressed by equation (1). Here, A is a positive constant (refractive index distribution constant). N=NO(1-1/2AX ² ) (1) A light flux incident from one end of a rod-shaped body having such a distribution travels while meandering around the central axis. The period L of the meandering optical path is expressed by equation (2). When the refractive index distribution is expressed by equation (3), it becomes a concave lens. Here B is a positive constant. N = NO (1 + 1/ ^2B A so-called slab lens that has a refractive index distribution as expressed by equation 3) is also known. When molding an optical transmission body with such a refractive index gradient using a plastic material, conventionally, a monomer Ma forming a polymer Pa having a refractive index of Na is partially polymerized to form a desired lens shape, for example, a cylindrical shape. and mold this lens base material into a monomer Mb forming a polymer Pb having a refractive index Nb different from the above refractive index Na.
A method has been implemented in which the polymerization is completed after immersing the base material in a liquid to give a refractive index distribution based on the diffusion concentration gradient of monomer Mb from the surface of the base material toward the inside. However, in the conventional method described above, the shape of the monomer Ma lens base material that should be initially prepared cannot be maintained unless the polymerization has progressed to a point where polymerization is almost complete. The rate of inward diffusion is slow, and it takes a very long time to obtain the desired refractive index distribution, and the lens shape often deforms until the end of the process, making it difficult to manufacture lenses with precise shapes. There was a problem that it was difficult and it was difficult to obtain large ones. Because it is necessary to perform two separate steps: molding of the lens base material by partial polymerization of monomer Ma and subsequent diffusion treatment in monomer Mb, the entire process takes a lot of time. The drawback was that the process was complicated. An object of the present invention is to solve the above-mentioned conventional problems, and to form a monomer Ma for forming a refractive index distribution on the lens base material while maintaining its shape accurately in a state where the monomer Ma constituting the lens base material has a low degree of polymerization. It is an object of the present invention to provide a method for manufacturing a plastic optical transmission body having a refractive index gradient suitable for mass production, which can diffuse the mercury Mb and thus greatly shorten the overall processing time. In the method according to the present invention for achieving the above object,
The refractive index at the outer surface of the target optical transmission body is Nb,
When the refractive index at the center is Na, monomers (including monomer mixtures) Mb forming polymers (including copolymers) and Pb with a refractive index of Nb are non-reactive with respect to the monomer Mb. The monomer Mb is impregnated into a mold made of a porous material having fine continuous pores, such as a porous material having fine continuous pores. In this mold, a female cavity is formed which approximately matches the desired shape of the optical transmitter, such as a columnar shape, a flat plate shape, an elbow shape, or the like. Then, a monomer (including a monomer mixture) Ma forming a polymer (including a copolymer) Pa having a refractive index of Na is filled into the female mold part in an uncompleted polymerization state. Here, filling the female mold space with the monomer Ma and impregnating the aforementioned mold with the monomer Mb may be performed first. As a result of the above, monomer Mb leaches from the mold surface in contact with monomer Ma, diffuses into the monomer inside the female mold space, and completes polymerization at a predetermined stage to form the mold in the female mold. A refractive index distribution is formed in the polymer Pa in which the refractive index gradually changes from Nb to Na based on the concentration distribution of the monomer Mb from the surface toward the center. According to the method described above, the resin monomer for forming the refractive index distribution is diffused into the base material through the wall surface of the mold while the resin monomer for the lens base material is held in the target shape within the mold. Therefore, unlike conventional methods, it is not necessary to proceed with polymerization to the extent that the lens base resin body is not deformed, and diffusion can be carried out in a highly fluid state. Therefore, the diffusion rate is extremely high compared to conventional methods, and the embodiments of the present invention make it possible to significantly shorten the entire processing process. It has now become possible to fabricate a refractive index gradient type plastic optical transmission body. In the present invention, the materials used in the mold containing the monomer Mb include polyolefin, polycarbonate, polyurethane, cellulose, phenolic resin, and oligomers such as polyether, polycarbonate, polyester, polyamide, and polyolefin, which have a double molecule at both ends. Porous bodies made of organic polymer materials such as macromonomer polymers with crosslinkable functional groups such as bonds and silanol groups introduced, ceramics such as glass powder sintered bodies and unglazed clay, or porous metals are used. It is possible. The monomer Ma filling the female mold space is
Polymerization may be carried out to any degree as long as it does not leak out through the wall of the mold.The specific degree of polymerization is determined by the relationship with the diffusion conditions, but if the degree of polymerization is too high, monomer diffusing into
Since the diffusion rate of Mb becomes slow and the treatment takes time, it is desirable that the degree of polymerization of the monomer Ma during the Mb diffusion treatment is 90% or less. The monomer Ma can be polymerized until it reaches the desired viscosity, and then poured into the female cavity of the mold. The boundary surface may be removed after the monomer Ma is polymerized. In addition, when the mold is made of an organic polymer material, the precursor of the substance forming the mold and the monomer Ma are separated at an interface having a predetermined shape, and the reaction is proceeded simultaneously. It is also effective to remove the boundary surface after a suitable state is reached. The mold constituent material may contain monomeric Mb, and
Any material may be used as long as it does not interfere with Mb. Next, the monomer Mb is included in the mold constituent material, and the partially polymerized monomer Ma is removed from the inner wall surface of the female mold space of the mold that has come into contact with the partially polymerized monomer Ma. Monomer Mb is diffused and polymerized into the interior, and the concentration of monomer Mb gradually decreases from the surface of the partially polymerized monomer Ma in contact with the mold to the inside. Create a slope that looks like this and fix it. At this time, the monomer Mb can be included in the mold later, but if the mold can be formed in such a way that Mb does not react with the precursor of the material that forms the mold, it is possible to form the mold. You may mix both before doing so. Monomer Mb may be first diffused to obtain a desired distribution and then polymerized together with monomer Ma to fix the distribution, or diffusion and polymerization may occur simultaneously. The monomer Ma used to form the lens base material in the present invention may be any molecule as long as it contains a polymerizable double bond, but is preferably an allyl group, an acrylic acid group, or a methacrylic acid group. A monomer having two or more groups or vinyl groups, or two or more groups selected from the group consisting of an allyl group, an acrylic acid group, a methacrylic acid group, and a vinyl group can be used. Examples of monomers suitable for the present invention include (1) allyl compounds diallyl esters such as diallyl phthalate, diallyl isophthalate, diallyl terephthalate, diethylene glycol bisallyl carbonate, triallyl trimellitate, triallyl phosphate, and triallyl phosphite; Triallyl esters such as: unsaturated acid allyl esters such as allyl methacrylate and allyl acrylate (2) Compounds represented by R ₁ - R _{2 -} R _{3 R 1 and R 3 are both} vinyl groups, acrylic groups,
It is a vinyl ester group or a methacrylic group.
Alternatively, one of R ₁ and R ₃ is any of the four groups vinyl, acrylic, methacrylic, and vinyl ester, and the other is any of the other three groups among the four groups. That's it. _R2 :

[Formula] (P- or m-different gender) or

[Formula] (P- or m-isomer) (more than 2A groups) or

[Formula] - (CH ₂ CH ₂ O -) mCH ₂ CH ₂ - (m = 0 to 20) -( _CH2 )p- (p=3~15) or

[Formula] (The above 2B groups) (3) A mixture of the monomers in (1) and (2) above, or at least one of the five types of monovinyl compounds, vinyl esters, acrylic esters, and methacrylic esters. A mixture of a species and monomers (1) and (2) above (or a mixture thereof). As Mb, (4)

Compound represented by [Formula] However, X is hydrogen or methyl group, Y is

【formula】

[Formula] -CH= _CH2- ( _CH2 )lH (l=1-8) i-propyl, i-butyl, S-butyl, t-
butyl

【formula】

[Formula] (h=0 to 2) or -(CH ₂ CH ₂ O-) _p CH ₂ CH ₃ (p=1 to 6) (more than 4A groups) or - (CF ₂ ) _a F (a=1 to 6) -CH ₂ (CF ₂ ) _b H (b = 1 to 8) - CH ₂ CH ₂ O・CH ₂ CF ₃ - (CH ₂ CH ₂ O) _c CF ₂ CF ₂ H (c = 1 to 4) -CH ₂ CH ₂ O・CH ₂ (CF ₂ ) _a F (a=1 to 6) - CH ₂ (CF ₂ ) _d O(CF ₂ ) _l F (d=1 to 2, l=
1 to 4) or -Si(OC ₂ H ₅ ) ₃ (4B groups) (5)

Compound R ₄ represented by [Formula]: -(CH ₂ ) _f - CH ₃ (f = 0 to 2) (5A groups) or - (CH ₂ ) _g H (g = 1 to 3)

【formula】

[Formula] (The above 5B groups) (6) Any of the above (1) to (3) as Ma and (4) to (6) as Mb can be combined as the mixture of monomers described in Items 4 and 5. But especially as Ma
If a 2B group monomer is used and a 4B group or (5A) monomer is used as Mb, an optical transmission body with extremely small chromatic aberration and excellent durability can be obtained. In addition, in order to adjust the degree of polymerization of the transparent polymer, the method of adding a monomer having one unsaturated group to the crosslinkable Ma as mentioned in Section 3, and the method of adding CBr ₄ ,
A method of adding a chain transfer agent such as Ccl ₄ or mercaptans, or a method of using both in combination is effective. Next, an embodiment of the method of the present invention shown in the drawings will be described. 1 to 3 show a method of manufacturing a one-dimensional gradient index lens having a lens function equivalent to a semi-cylindrical lens using the method of the present invention. As shown in Fig. 4, a gradient index type one-dimensional lens has a parallelepiped substrate 1 made of transparent plastic, and the refractive index Na at the center of the thickness of the substrate 1 is the maximum, and the refractive index Na is the maximum at the center of the thickness to of the substrate 1. The lens has a refractive index distribution such that the refractive index Nb is the minimum and the refractive index gradually decreases parabolically from the center toward both surfaces, and the refractive index is uniform in the direction of the width W of the substrate 1. . In such an optical transmission body 10, when a parallel light beam is incident from one end surface 1A side, the light beam that enters the substrate 1 meanderingly travels with the period L of the above-mentioned equation (2), and the lens length z corresponds to the lens length z. The focal lines are connected at appropriate distances from the end surface 1B. In the method according to the present invention for manufacturing the flat one-dimensional lens as described above, first, as shown in FIG. A lens mold 3 is placed on the substrate 2. As described above, the mold 3 is made of a material that is non-reactive with the monomer Mb and can be freely impregnated and leached with the monomer Mb, such as a phenolic resin foam having continuous pores. A lens female mold space 4 is provided in this mold 3 in accordance with the desired lens shape. In the case of this example, a plurality of flat female spaces 4 are provided at intervals. Next, each of the female mold spaces 4 is filled with a partially polymerized resin monomer Ma, and another substrate similar to the substrate 2 is placed between the two substrates 2, 2 and the mold 3. After the laminate is fixed so as not to be separated from each other, it is immersed in a liquid of resin monomer Mb for forming a refractive index distribution. As a result, the monomer Mb seeps into the mold 3 from the side-exposed mold surface, oozes out from the inner wall surface of the lens female mold space 4, and fills this space 4. It diffuses into the partially polymerized monomer Ma. After being immersed for a certain period of time, it is taken out to complete the polymerization, thereby obtaining a flat plate-shaped gradient index plastic one-dimensional lens as shown in FIG. Similarly, by changing the shape of the female mold space 4 of the mold 3, it is possible to easily produce refractive index distribution type plastic optical transmitters 10 having various shapes as illustrated in FIGS. 5 to 7, for example. It can be manufactured. Figure 5 shows an elbow-type transmission body in which a cylindrical lens is bent at 90 degrees.For example, by connecting optical fibers to both end faces, the light transmitted from one optical fiber is bent at right angles and then transferred to the other optical fiber. Relay transmission to. The one in Figure 6 is for branching and merging, and by connecting optical fibers to each end of the trident, the light transmitted through one optical fiber is split equally into two optical fibers. Or conversely, it is used to mix the light transmitted by two optical fibers and then transmit it to a single optical fiber. In addition, the one in Figure 7 has a single gradient index cylindrical lens in the center, with multiple gradient index cylindrical lenses branching out at both ends, and optical fibers are connected to each of these branch ends. By doing this, the lights of various wavelengths sent individually through one group of fibers are mixed in the center, and then
It works as a mixing coupler that evenly splits and injects light into the group of optical fibers on the other side. Example 1 Approximately 30 communicating bubbles with a pore diameter of around 60 μm
% of the phenolic resin foam is cut into the shape shown in Figure 1 to form a mold 3, and CR-39 (diethylene glycol bisallyl carbonate) is
This foam is made by adding approximately 3% BPO (benzoyl peroxide) and uniformly dissolving it, polymerizing it in a constant temperature water bath at 75 degrees Celsius, and cooling it when the viscosity reaches about 20,000 cp at 25 degrees Celsius. A rectangular parallelepiped female mold space 4 made in the molded product was filled with the mixture, and a lid was placed between a glass plate. Add this to 4FMA (methacrylic acid 1,
1,3-trihydroperfluoropropyl) and left at room temperature for about 1 hour, then transferred to a constant temperature water bath at 75°C and heated for 10 hours to cure. After polishing the end face, when the light from the mercury lamp passes through it, about 3
Three bright lines were observed on the screen placed at mm. Example 2 Approximately 3% BPO (benzoyl peroxide) is added to DAIP (diallylisophthalate) and dissolved to approximately 1%, and this is polymerized in a constant temperature water bath at 75°C to a viscosity of approximately 20,000 cp at 25°C. When the temperature reached the temperature, it was cooled to stop the polymerization. A mold 3 shown in FIG. 1 is made by sintering fine polyethylene powder and pasting together plates in which fine pores communicate with the outside, and the mold 3 shown in FIG. A half-polymer of DAIP prepared as described above was injected into the container, and the top and bottom were sandwiched between glass plates and a lid was placed. This was immersed in MMA (methyl methacrylate) and left at room temperature for about 1 hour, then transferred to a constant temperature water bath at 75°C and heated for 10 hours to harden. After polishing the end face, when light from the mercury lamp was passed through it, three bright lines were observed on the screen placed approximately 2 mm from the end face of the lens on the opposite side of the mercury lamp.

[Brief explanation of drawings]

The drawings show examples of the invention, and Figure 1 shows monomers.
Figure 2 is a cross-sectional view showing the state in which Ma is filled into the mold, Figure 2 is a plan view of the same, and Figure 3 is a diagram showing the mold filled with monomer Ma being immersed in monomer Mb to transfer Mb into Ma. FIG. 4 is a cross-sectional view showing the diffusion process, FIG. 4 is a perspective view showing a gradient index type one-dimensional lens obtained by the method shown in FIGS. 1 to 3, and FIGS. FIG. 3... Molding mold, 4... Female mold space, 10... Optical transmission body, Ma, Mb... Monomer.

Claims (1)

[Claims] 1. Polymer (including copolymer) Pb with a refractive index of Nb
Monomers (including monomer mixtures) forming Mb
is impregnated into a mold made of a substance that is non-reactive with the monomer Mb and can be freely impregnated and leached with the monomer Mb, and the mold is filled with a material having a desired shape of the light transmitting body. forming a mated female mold part; in the female mold part;
A monomer (including a monomer mixture) Ma forming a polymer (including a copolymer) Pa having a refractive index Na different from that of Nb is filled in an uncompleted polymerized state and brought into contact with the monomer Ma. Refraction characterized in that polymerization is completed after giving a refractive index gradient that gradually changes from the surface to the inside of the polymer Pa by leaching and diffusing the monomer Mb from the surface of the mold. A method of manufacturing a plastic optical conduit with a rate gradient. 2. The method of manufacturing a plastic optical transmission body according to claim 1, wherein the mold is made of a porous material having fine continuous pores.