JPH0614125B2 - Method for manufacturing synthetic resin optical transmitter - Google Patents

Description

The present invention relates to a method for manufacturing a synthetic resin optical transmission medium having a refractive index distribution.

As a light transmission body, a transparent rod-shaped body having a refractive index distribution that decreases in proportion to the square of the distance from the central axis is known. This transparent rod has a convex lens function, and its refractive index distribution is approximated by the equation (1).

(In the formula, n (r) represents the refractive index at the point of distance r from the central axis, No represents the refractive index in the central axis, and A represents a positive constant.) A light beam meanders in such a transparent rod. And propagates, and its period L is expressed by equation (2).

Also, as approximated by equation (3), the distance from the center is 2
When the transparent rod-shaped body has a refractive index distribution that increases in proportion to the power, the transparent rod-shaped body becomes an optical transmission body having a concave lens function.

(In the formula, n (r) and No are the same as described above, and B is a positive constant.) A method for producing a synthetic resin optical transmission body having such a refractive index distribution is disclosed in JP-B-52-5857. It is described in Japanese Patent Application Laid-Open No. 51-16394, Japanese Patent Publication No. 56-37521, Japanese Patent Application No. 57-43354, and the like.

In the methods described in JP-B-52-5857 and JP-A-51-16394, first, the crosslinkable monomer Ma that forms the network polymer Pa is changed from a liquid state to a gel state in which the fluidity is lost. To form a transparent gel-like base material. Next, this base material is immersed in a liquid phase composed of a monomer Mb different from the monomer Ma, and a concentration gradient of the monomer Mb is such that the base material gradually decreases from its surface toward the inside. To have,
Diffuse the monomer Mb. At this time, as the monomer Mb,
Polymer having a refractive index different from that of the network polymer Pa
A monomer that produces Pb is used. The monomer Mb is polymerized simultaneously with the diffusion and / or during the heat treatment step after the diffusion, and at this time, the polymerization of the monomer Ma is also completed. Thus, in the methods disclosed in Japanese Patent Publication No. 52-5857 and Japanese Patent Publication No. 51-16394, a synthetic resin optical transmission body having a desired refractive index distribution is obtained.

However, the above-mentioned method has some disadvantages because the base material is immersed in the liquid monomer Mb to bring the surface of the base material into direct contact with the liquid monomer Mb. For example, monomer
When Mb diffusion and polymerization are performed at the same time, the immersion temperature is set to a relatively high temperature, and the polymerization initiator normally contained in the base material elutes in the liquid phase with the lapse of immersion time. In the liquid phase, the polymerization of the monomer Mb gradually occurs and becomes viscous. As a result, when the base material is taken out of the liquid phase after finishing the diffusion, the viscous layer thus formed is taken out while being attached to the surface of the base material. Then, during the heat treatment step performed to complete the polymerization, the monomer Mb is leached from this viscous layer and diffused into the base material, which causes an undesired distortion of the refractive index in the vicinity of the outer periphery of the obtained optical transmission body. Cause increase. However, on the other hand, the monomer in the liquid phase
If a polymerization inhibitor is added to suppress the polymerization of Mb,
This diffuses into the base material at the same time as the diffusion of the monomer Mb, and hinders the completion of polymerization in the heat treatment step.

Further, in the case of polymerizing after the diffusion of the monomer Mb, a relatively low immersion temperature is required, but in this case, the diffused monomer is
Since Mb evaporates from the outer peripheral portion of the base material during the heat treatment step, this also causes an increase in undesirable strain in the refractive index distribution near the outer peripheral portion.

The methods described in Japanese Patent Application Laid-Open No. 54-119939 and Japanese Patent Application No. 57-43354 are intended to improve the above-mentioned method to avoid the distortion of the refractive index distribution near the outer peripheral portion. According to the method described in the above document, the diffusion of the monomer Mb is performed in the gas phase or in the atomized state. That is, the base material is placed in the vapor and atomizing atmosphere of the monomer Mb for a predetermined time to diffuse the monomer Mb into the base material, and at the same time as this diffusion, the monomer Mb is partially polymerized, and finally. Polymerization is completed by heat treatment. In this method, the base material is not in contact with the liquid-phase monomer Mb, but is in contact with the gas-phase or atomized monomer Mb, and therefore has the following advantages.

(1) Extra monomer Mb does not adhere to the surface of the base material. Therefore,
The monomer Mb attached during the heat treatment step does not diffuse from the surface of the base material to the inside. Further, since the diffusion is performed at a high temperature, the monomer Mb is polymerized and immobilized while diffusing inside the base material. Therefore, the monomer Mb does not evaporate from the outer peripheral portion of the base material during the heat treatment step. Therefore, it is possible to obtain an optical transmission body in which the distortion of the refractive index at the outer peripheral portion is small and the desired refractive index distribution is wide.

In the case of manufacturing a synthetic resin optical transmission medium having a refractive index distribution approximated by formulas (1) and (2) by these methods, in order to produce a synthetic resin optical transmission medium with small aberrations to the entire periphery, When the monomer Mb is further diffused under various conditions such as diffusion temperature diffusion time in the vapor phase or atomized state, it is extremely difficult to finely control the vapor phase concentration, the atomized concentration, and the like.

Therefore, in the present invention, instead of finely controlling various conditions, the monomer Mb is diffused into a transparent gel-like matrix in which the monomer Ma is partially polymerized, and then the monomer Mc having a different refractive index, Md ...
-Mn Diffuses as the conversion rate of the transparent gel base material rises, corrects the refractive index distribution in the peripheral region, and manufactures a synthetic resin optical transmission body with little aberration.

To explain the present invention in detail, in order to precisely control the refractive index distribution up to the periphery, a polymer (including a copolymer) Pb (where the refractive index is Nb and Na> Nb) is added to the transparent gel matrix. After polymerizing one or more types of monomer Mb that form the polymer while diffusing, when the average polymerization conversion rate of the base material reaches P ₁ % for the purpose of correcting the refractive index distribution in the peripheral part, Polymerization is carried out while diffusing one or a plurality of types of monomers Mc forming a Pc (including a copolymer) Pc (whose refractive index is Nc and Nb ≠ Nc). Further, when the average polymerization conversion rate of the base material reaches P ₂ (P ₂ > P ₁ )%, the polymer (including the copolymer) Pd (its refractive index is Nb
Nc ≠ Nd) The average polymerization conversion of the base material is repeated several times until a refractive index distribution with as small an aberration as possible is formed, for example, by polymerizing one or more kinds of monomers Md that form Nd. As the index Pk (k = 1,2,3 ... n) increases, the refractive index when a polymer (including a copolymer) is formed is It is a method of polymerizing while diffusing a monomer different from the monomer.

In this case, the average polymerization conversion rate Pk of the base material (k = 1,2,3 ... n)
The range of 10% <Pk <80% is desirable. Ie
When Pk is 10% or less, it becomes difficult to stably maintain the shape of the gel lot, and when Pk is 80% or more, it takes an extremely long time to diffuse the monomer into the gel rod, which is not practical. A more preferable Pk range is 30% to 60%. Further, if the distance between Pk and Pk + 1 is too small, the distribution correction effect due to the additional diffusion of the different kinds of monomers will be weakened.

In the method of the present invention, the monomers Mb to be diffused into the base material rod initially and the monomers Mc and Md to be diffused subsequently do not necessarily need to use all different kinds of monomers. However, if different from the monomer diffused immediately before, the monomer used in the previous step may be diffused again in some cases.

In the method of the present invention, a monomer capable of being polymerized to form a network polymer Pa having a transparent and refractive index of Na is used as the monomer Ma, but this monomer is a single monomer. It may be a monomer or a mixture of plural kinds of monomers. Such a monomer Ma has at least two groups each having a double bond, such as an allyl group, an acrylic acid group, a methacrylic acid group and a vinyl group, or a monomer having at least two of them at the same time. A monomer is preferred. Next, specific examples of the monomer Ma will be given.

(1), allyl compounds and mixtures thereof.

Diallyl esters such as diallyl phthalate, diallyl isophthalate, diallyl terephthalate, and diethylene glycol bisallyl carbonate; triallyl trimellitate,
Triallyl esters such as triallyl phosphate and triallyl phosphite; unsaturated acid allyl esters such as allyl methacrylate and allyl acrylate.

(2), compounds represented by R ₁ -R ₂ -R ₃ and mixtures thereof.

A compound in which R ₁ and R ₃ are both a vinyl group, an acrylic acid group, a vinyl ester group, or a methacrylic acid group; _one of R ₁ and R ₃ is a vinyl group, an acrylic acid group, a methacrylic acid group, and a vinyl ester. A compound wherein any of the four groups in the group is the other and the other is the remaining 3 groups.

Here, R ₂ can be selected from the divalent groups shown below.

(3), a mixture of the monomers of (1) and (2) above, or at least one of five kinds of monovinyl compounds, vinyl esters, acrylic acid esters and methacrylic acid esters and the above (1) Or (2) monomer (or mixture thereof)
Mixture with.

In the present invention, the monomers Mb, Mc, Md ... Mn are transparent polymers having a refractive index Nb, Nc, Nd ... Nn larger or smaller than the above refractive index Na when they are polymerized. Coalescing P
Those that form b, Pc, Pd ... Pn are selected. This monomer
Mb, Mc, Md ... Mn may be a single monomer or a mixture of plural kinds of monomers. The polymers Pb, Pc, Pd ... Pn may be either network polymers or linear polymers.
When the refractive index Nb is smaller than the refractive index Na, the obtained optical transmission body has a convex lens function in which the refractive index distribution represented by the above formula (1) is formed. On the contrary, the refractive index Nb
When is larger than the refractive index Na, an optical transmission body having a concave lens action with the refractive index distribution represented by the above formula (3) can be obtained. The difference between these refractive indexes (| Na-Nb |) is preferably 0.00 or more. If this difference is too small, the desired refractive index gradient cannot be obtained. Further, the monomers Mb, Nc, Nd ... Nn preferably have a relatively high vapor pressure, especially when vapor-phase diffusion is performed, and for example, at a diffusion temperature of 5 mmHg.
It is preferable to have a higher saturated vapor pressure than. Examples of such monomers Mb, Nc, Nd ... Nn include styrene, methacrylic acid ester, acrylic acid ester, vinyl acetate, vinyl chloride, acrylonitrile, butadiene and mixtures thereof.

In particular, as a combination of the monomer Ma and the monomers Mb, Nc, Nd ... Nn suitable for manufacturing a synthetic resin optical transmission body having low chromatic aberration, the following can be exemplified.

(a), Ma as diethylene glycol bisallyl carbonate, or a mixture thereof with diallyl phthalate, diallyl isophthalate, vinyl benzoate or styrene (provided that the amount of diethylene glycol bisallyl carbonate in this mixture is 50% by weight or more) Is preferable, and more preferably 70% by weight or more). Mb, N
As c, Nd ... Nn, the compound (A): [In the formula, X is a hydrogen atom or a methyl group, Y is a phenyl group, a methylphenyl group, a vinyl group, an i-propyl group, an i-
Butyl group, s-butyl group, t-butyl group, and Represents a group selected from the group consisting of ] The compound or its mixture represented by these.

(b), diethylene glycol bisallyl carbonate as Ma, or methyl acrylate, ethyl acrylate, n-butyl methacrylate or t methacrylate
-Mixture with butyl (provided that the amount of diethylene glycol bisallyl carbonate in this mixture is 10% by weight)
The above is preferable). As Mb, Nc, Nd ... Nn,
Compound (B) [In the formula, X is a hydrogen atom or a methyl group, and Y is-(C
F ₂ ) _i F (i = 1 to 6), -CH ₂ (CF ₂ ) iH (j = 1 to 8), -CH ₂ CH ₂ OCH
₂ CF ₃ − (CH ₂ CH ₂ O) _k CF ₂ CF ₂ H (k = 1 to 4), − (CH ₂ CH ₂ OCH ₂ (CF ₂ ) lF
(l = 1~6), - with _{(CH 2 (CF 2) m} O (CF 2) represents the _{n F (m = 1~2, n} = 1~4) a group selected from the group consisting of]. Methacrylic acid or fluorinated alcohol alcohol ester of acrylic acid represented, or Y in the general formula (B) is -S.
A compound (C) which is i (OC ₂ H ₅ ) ₃ .

(C), a mixture of diethylene glycol bisallyl carbonate as the monomer Ma and the above compound (B) or (C) (however, the amount of diethylene glycol bisallyl cobonate in this mixture is preferably 10% by weight or more) ). The above compound (A) as monomers Mb, Nc, Nd ... Nn.

An embodiment in which the method of the present invention is applied to a synthetic resin optical transmission device manufacturing apparatus shown in FIG. 1 will be described below with reference to the drawings.

As shown in FIG. 1, the diffusion treatment device (31) comprises a diffusion pipe (32) as a diffusion means and a pair of monomer gas generation gas (33A), (33B) as a monomer gas generation means. Made of Monomer M
Transparent gel object (3
4) is a rod support member in which the diffusion pipe (32) is placed in the diffusion chamber (43).
It is supported in a vertical position by (10). In addition, the diffusion tube (3
There is an outlet (39) at the bottom of 2), and this outlet (39)
At the other end of the exhaust pipe (40) attached to
(41) is provided. A cold trap (42) is attached in the middle of the exhaust pipe (40). Then, the diffusion chamber (43) is connected to the exhaust pipe (4) by the vacuum pump (41).
It is intended to be exhausted through 0) and the interval (44).
The outer periphery of the diffusion chamber (43) enters through the entrance (45) and exits.
The diffusion chamber (43) can be maintained at a predetermined temperature by being warmed by the hot water (47) coming out of the (46).

Further, conduits (48) (49) are attached to the upper part of the diffusion chamber (32). In the middle of this conduit (48) is a valve (5
0) is provided, nitrogen gas supplied from one end of the conduit (48) with the valve (50) opened is
It can be introduced into the diffusion chamber (43) through the nominal gap (51). Further, a valve (53) is provided in the middle of the conduit (49), and the monomer gas generator (33A) connected to the other end of the conduit (49) with the valve (53) opened. The monomer gas supplied from the conduit (49), the inlet (54) and the gap (5
It can be introduced into the diffusion chamber (43) through 5). A thermometer (76) (77) is installed above and below the diffusion tube (32).
Each (78) is attached so that the temperature of each part can be measured.

On the other hand, a supply pipe (56) for supplying the monomer Mb to be diffused is attached to the upper part of the monomer gas generator (33A), and is provided in the middle of this supply pipe (56). Valve (57) open, open the supply port (56) at the top of the supply pipe (56).
The monomer Mb can be supplied from a) into the storage chamber (58). A cooling pipe (59) is provided on the outer periphery of the storage chamber (58), and the storage chamber (58) is flowed through the cooling pipe (59) to keep the storage chamber (58) at a temperature of, for example, about 10 [° C]. It can be cooled. There is also a pipe (60) at the bottom of the storage chamber (58).
Of the monomer Mb in the storage chamber (58) with the valve (61) provided in the middle of the pipe (60) open.
From the tip (60a) of the pipe (60) as the first container (6
2) can be supplied within. This Reservoir (62)
Is maintained at, for example, about 10 [° C.] by the cooling water flowing through the cooling pipe (63) provided on the outer periphery.

Further, this storage container (62) is provided with conduits (64) (65) (66).
It is connected to a storage container (67) as a second container. A pump (68) is provided in the middle of the conduit (65), and depending on this pump (68), for example, the liquid of the quantity Mb in the storage container (67) can be transferred into the storage container (62). It has become. Further, the storage container (67) can be heated to about 30 to 100 ° C. by energizing the heater (69) provided on the outer circumference. When polyfluoroethylene methacrylate (3FMA) is used as the monomer Mb, the storage container (67) may be heated to 70 to 80 ° C. Furthermore, in this storage container (67), the tip is located in the monomer Mb (70) as a valve generator (71) as an inert gas supply means.
Is equipped with a valve (72) to this valve generator (71).
Nitrogen gas supplied from one end (73a) of the pipe (73) connected through is introduced into the monomer Mb (70) from a large number of pores provided in the valve generator (71). I'm supposed to get it. Further, the gas of the monomer Mb generated in the storage container (67) is
Diffusion chamber of diffusion pipe (32) from outlet (74) through conduit (49)
It is also being supplied to (43). The storage container (6
A flowmeter (75) is attached to the conduit (49) adjacent to 7) so that the flow rate of the gas flowing through the conduit (49) can be measured.

Also, another monomer gas generator (33B) having the same structure as the above is connected through another conduit (49), and this generator (33B) is different from the monomers Ma and Mb. Mc is stored.

Next, a method for diffusing the monomer into the rod-shaped transparent gel object (34) using the diffusion processing device (31) configured as described above will be described.

In Fig. 1, first, with the valve (57) open, supply pipe
After injecting a predetermined amount of liquid monomer Mb from the upper end (56a) of (56), the valve (57) is closed. Valve at this point (61)
Is closed and the liquid of the injected monomer Mb is stored in the storage chamber (58). After cooling the liquid of the monomer Mb to about 10 [° C.] in the storage chamber (58), open the valve (61) to open the pipe.
The liquid of the monomer Mb is introduced into the storage container (62) from the tip (60a) of the (60). The liquid of the monomer Mb gradually accumulates in the storage container (62), and when the height of the liquid level becomes approximately the same as the conduit (64), the inside of the storage container (62) passes through the conduit (64). The liquid of the monomer Mb begins to flow into the storage container (62) after a while.
The liquid level of the liquid of the monomer Mb in (67) is almost the same.
At this point, close the valve (61) slightly and let the tip (60) of the tube (60)
The state where the solution of the monomer Mb is dripped little by little from a). In addition, the storage container (62) is set to about 10 ° C in advance, and
Keep (67) at about 80 ° C.

The reservoir (6) is then activated by starting the pump (68).
The liquid of the monomer Mb in 7) begins to be transferred into the storage container (62) via the conduit (65). When the pump (68) is started, the height of the liquid level of the liquid of the monomer Mb in the storage container (67) becomes low, and the liquid of the liquid of the monomer Mb in the storage container (62) becomes low. Although the height of the surface becomes higher, part of the liquid of the monomer Mb in the storage container (62) is a conduit.
Since it flows through the (64) again into the storage container (67), there is not much difference in the liquid level of the liquid of the monomer Mb in the storage containers (62) and (67). In steady state, the tip (60a) of the tube (60)
While the liquid of the monomer Mb is being dropped from the storage container
(62) While maintaining the liquid level of the monomer Mb liquid in (67) substantially the same, circulate the monomer Mb liquid between these storage containers (62) (67). be able to. Since the upper portions of the storage containers (62) (67) are connected to each other by the conduit (66), a space (62a) not filled with the liquid of the monomer Mb of these storage containers (62) (67). It is possible to prevent a difference in the liquid level of the liquid of the monomer Mb in the storage containers (62) and (67) from being caused by the pressure difference between the (67a). Thus, by circulating the liquid of the monomer Mb between the storage containers (62) (67),
The liquid of the monomer Mb is prevented from polymerizing in the storage container (67) maintained at a high temperature of about [° C.]. The amount of the monomer Mb dropped from the tip (60a) of the tube (60) is
The selection is made so as to supplement the monomer Mb that is consumed by vaporization in the storage container (67), but is actually performed as follows. That is, if the diameter of the pipe (60) is properly selected, the liquid level of the liquid of the monomer Mb in the storage container (62) is lowered and the pipe is
When it is about to separate from the tip (60a) of (60), this tip (60a)
Since air enters into the pipe (60) from the pipe, the liquid of the monomer Mb is automatically supplied from the pipe (60) into the storage container (62).

Next, when the height of the liquid level and the liquid temperature of the liquid of the monomer Mb in the storage container (62) (67) have stabilized, nitrogen is supplied from one end (73a) of the pipe (73) with the valve (72) opened. Introduce gas and pulsus generator (71)
This nitrogen gas is fed into the monomer Mb (70). As a result, the monomer Mb is vaporized, and the storage container (67) is filled with the mixed gas of the monomer Mb gas and the nitrogen gas. The mixed gas is sent from the outlet (74) through the conduit (49) toward the diffusion pipe (32) and is supplied into the diffusion chamber (43) through the inlet (54) and the gap (55). The mixed gas thus supplied into the diffusion chamber (43) flows downward, and the outlet (39)
And exhausted by the vacuum pump (41) through the exhaust pipe (40). While the mixed gas flows downward in the space (43b), the gas of the monomer Mb contained in the mixed gas is brought into contact with the surface of the transparent gel object (34), thereby producing a single amount. The body Mb diffuses inside the transparent gel object (34). The diffusion chamber (43) was filled with warm water (47) to the storage container (6
It is maintained at the same or higher temperature than the heating temperature in 7). This temperature is, for example, 3 FM, which is known as monomer Mb.
When A is used, the temperature may be about 80 ° C. Further, during diffusion, as described above, nitrogen gas is supplied from one end (48a) of the conduit (48), and nitrogen gas is introduced into the upper chamber (52) through this conduit (48). Flow rate of conduit (49)
The flow rate of the mixed gas flowing therethrough is kept about 10 times.

As described above, at a certain stage where the diffusion and polymerization of the monomer Mb into the transparent gel object (34) proceeded, for example, the transparent gel object (3
When the conversion rate of 4) reached about 60%, the valve (53) on the side of one of the monomer gas generators (33A) was closed, and only nitrogen gas was allowed to flow into the diffusion chamber (47). The monomer Mb remaining in (47) is purged. After stopping the inflow of nitrogen gas, open the valve of the other monomer gas generator (33B) to introduce a mixed gas of monomer Mc and nitrogen into the diffusion chamber (47) to form a transparent gel object.
Polymerization is performed while diffusing monomer MC into (34). When the predetermined diffusion process is completed, the rod (34) is taken out of the diffusion chamber and heat-treated to complete the polymerization. Next, a preferred example of an apparatus for continuously forming a gradient index lens base material is shown in FIG.

The prepolymer (22) that preliminarily polymerizes the monomer Ma and retains fluidity until just before gelation is put into the extruder 1 under pressure and communicates with the extruder 1 to prevent non-adhesion of fluororesin and the like. The prepolymer is molded into a continuous gel-like rod 11 by pumping the prepolymer into a molded tube 3 made of a material, which is then pulled up by an upper pulling device 9.

The molded tube 3 penetrates through the heating jacket 2,
The jacket 2 is provided with a high temperature conduit 16 and a low temperature conduit 17 which are independent from each other at the upper and lower parts,
Pass hot water of 80 ℃ as an example of hot water through the conduit 16, and
Hot water having a relatively low temperature is passed through 17 as an example of hot water having a relatively low temperature, whereby a temperature gradient that gradually increases in the direction of travel is given to the prepolymer that advances in the molded tube 3. The base material rod 11 that has exited the forming tube 3 then enters the first diffusion chamber 5 of the vapor phase diffusion device 4. The outer periphery of the diffusion chamber 5 is surrounded by an annular jacket portion 18 that serves as a heat medium flow path.
A heat medium such as hot water having a constant temperature is introduced into the jacket portion 18 through the inflow port 21A and flows out through the outflow port 21B.
The first monomer Mb to be diffused into the base material rod 11 is vaporized by the steam generator 14A and passed through the inlet 19 to the first diffusion chamber 5
The part introduced into the inside and not contacting with the rod 11 and not contributing to the diffusion is recovered by the pump 15 through the outlet 20, liquefied by the trap and reused.

The base material rod 11 exiting the first diffusion chamber 5 further rises,
Enter the diffusion chamber 6. Similar to the first diffusion chamber 5, the second diffusion chamber 6 has an annular jacket portion 18 whose outer periphery serves as a heat medium passage.
It is surrounded by. Further, the monomer Mc vaporized by the steam generator 14B is introduced into the second diffusion chamber 6 through the inlet 19. In the second diffusion chamber 6, the base material rod 11 in which the monomer Mb is diffused in the first diffusion chamber 5 as described above is used.
Mc is spread. The base material rod 11 exiting the second diffusion chamber enters the heat treatment chamber 7 arranged above, where the polymerization is completed and further cut into a predetermined length by a cutting device (not shown).

The base material rod in which two or more kinds of monomers Mb, Mc ... Are diffused in the base material of the monomer Ma molded as described above to form a parabolic refractive index distribution, has a predetermined length. It is cut into two pieces and polished at both ends into parallel planes to be used as a lens, or the rod is further heated and drawn to have a smaller diameter and then cut and polished to obtain a lens.

The method of the present invention described based on the above embodiments has the following advantages.

That is, in the conventional method, the shape of the refractive index distribution is bound by the balance between the diffusion rate of a single type of monomer Mb in the base material and the conversion rate of the base material. It was almost impossible to highly accurately approach the ideal refractive index distribution over the entire cross section from the outer periphery to the outer periphery, but according to the method of the present invention, different monomer MbMc in different stages in the conversion of the base material are different. .. is diffused, the degree of freedom in controlling the distribution is high, and it becomes easy to control the refractive index distribution and the vicinity of the outer periphery with high precision, and it is possible to obtain a synthetic resin lens with very small aberration.

Numerical examples will be described below.

Example 1 As a polymerization initiator, 3.0 ωt% of BPO was dissolved in diethylene glycol bisaryl carbonate (CR-39
(Trade name)) A polymer rod was obtained by preliminarily polymerizing by heating at 75 ° C. for 75 minutes in a 3 mmφ polytetrafluoroethylene tube. This gel rod is extruded from a polytetrafluoroethylene tube with N ₂ gas, and the diffusion device shown in FIG.
Installed in (32). 75 in monomer gas generator (33A)
C. Nitrogen bulb amount of 300 cc / min. Pre-adjusted n-butyl metafuriate (n-BMA) (refractive index as polymer np =
The steam of 1.4831) was sent into the diffusion device (32) by using nitrogen as a carrier gas.

Here, the temperature of the hot water circulating outside the diffuser (32) is 75
C., and at this temperature, n-BMA polymerized for 20 minutes while diffusing into the gel rod. When the conversion rate of the base material reached about 60%, nitrogen was introduced into the diffusion tube to purge the n-BMA vapor, and then the other monomer gas generator (33
In B), the vapor of -2.2.2.2-trifluoroethyl methacrylate (3FMA) (nP = 1.4210), which had been adjusted in advance at a nitrogen valve amount of 300CC / min at 70 ° C, was used as nitrogen as a carrier gas in the diffusion device (32). I sent it in. Then, the interior of the diffusion tube was replaced with nitrogen again, and heat treatment was performed at about 90 ° C. for about 20 hours to manufacture a synthetic resin optical transmission body. The produced synthetic resin optical transmitter had a refractive index distribution substantially equivalent to the expression (1) up to the periphery, and A = 0.0300 mm ⁻² numerical aperture NA = 0.38.

When spherical aberration is measured, it is within 35 μm in the central region and within 150 μm in the peripheral region, which is about 3 times that in the central region and about 4 in the peripheral region, compared with the values for single diffusion by the conventional method.
What was twice as good was obtained.

Example 2 As a polymerization initiator, diethylene glycol bisallyl carbonate in which 3.0 ωt% of BPO was dissolved was prepolymerized even when heated at 75 ° C for 65 minutes to obtain a propolymer having fluidity immediately before gelation. . The viscosity of this propolymer is
It is 1015 CPS at 20 ° C, and K and n in the equation of D = Kσ ⁿ (Ostwald's power law, D: shear rate (1 / sec), σ: shear stress (dyn / Cm ² )) are 2.28.
It was × 10 ^-2 (Cm ² / dynsec) and 1.20. This prepolymer
Insert (22) into the extruder (1) of the device shown in Fig. 2 and into a polytetrafluoroethylene molded tube (3) (diameter 3 mm, length 200 mm) that penetrates the heating jacket (2) 6.3 It was continuously fed at a constant flow rate of × 10 ^-2 ml / min. In the heating jacket (2), in the upper conduit (16), warm water (16) at 80 ° C,
A temperature gradient was formed by flowing warm water at 64 ° C through the lower conduits (17).

While passing through the polytetrafluoroethylene tube for 40 minutes, the prepolymer (22) was gelated and formed into a gel rod (11) having a diameter of 3 mm. The average polymerization conversion rate of this gel rod (11) was about 30%. Then, the gel lot was pulled up by a pulling device at a constant rate of 0.52 Cm / min in the vapor phase diffusion chamber.
The methacrylic acid-2,2,2-trifluoroethylene (3) filled in the first diffusion chamber (5) in (4) and filled in this diffusion chamber (5)
FMA) was allowed to stay in the atmosphere containing the vapor for about 40 minutes. Hot water of 75 ° C. was flowed outside the first diffusion chamber (5) to maintain this portion at a temperature of 75 ° C. 3FMA vapor was adjusted in advance in the monomer vapor generator (14A) at 75 ° C with a nitrogen valve amount of 300 CC / min, and nitrogen gas was used as a carrier gas for the inlet (19).
Through the first diffusion chamber (5). Further, when 3FMA vapor was recovered from the discharge port (20) by the pump (15) and liquefied by the trap, 3FMA was not polymerized and could be used repeatedly.
The gel rod (11) that has passed through the first diffusion chamber (5) is then sent to the second diffusion chamber (6) and placed in an atmosphere containing vapor of 1,1,5-trihydroperfluoropentyl methacrylate (8FMA). Let it stay for about 40 minutes. Hot water of 80 ° C is flowing outside the second diffusion chamber (6), and the temperature of this portion is maintained at 80 ° C. Here, 8FMA polymerizes while diffusing into the gel rod. 8FMA vapor was previously adjusted in the second monomer vapor generator (14B) at a nitrogen bubble amount of 300CC / min at 80 ° C, and nitrogen gas was introduced as a carrier gas into the second diffusion chamber (6) through the inlet (19). Was done. Further, when the 8FMA vapor pump (15) recovered from the discharge port (20) and liquefied in the trap, 8FMA was not polymerized and could be used repeatedly.

The gel rod passed through the diffusing device was further fed into a heat treatment chamber (7) consisting of a microwave cavity whose nitrogen was replaced. Microwave output 2450MH z, the guide wavelength is 14
It was 7.4 mm, and the cavity used was a thin-wave tube type cavity. The temperature distribution inside the cavity was measured by an infrared radiation thermometer and found to be 120 ℃ maximum and 70 ℃ minimum. The gel rod was heat-treated in this cavity for about 5 hours to complete the polymerization.

In this way, the synthetic resin optical transmission body manufactured continuously has a refractive index distribution that is substantially equivalent to the formula (1) up to the periphery, and the refractive index distribution constant A = 0.0322 mm ^-2 , aperture The number NA = 0.40.

When measuring the spherical aberration, it is within 25 μm in the central region and within 120 μm in the peripheral region, and it is about 4 times better in the central region and about 5 times better in the peripheral region than the value of the previous single diffusion. It was

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of an apparatus suitable for carrying out the method of the present invention, and FIG. 2 is a sectional view showing an example of another apparatus. 1 ... Extruder, 2 ... Heating jacket 3 ... Molding tube, 4 ... Gas phase diffusion device 5 ... First diffusion chamber, 6 ... Second diffusion chamber 7 ... Heat treatment chamber, 11 ... Mother Material rod 14A, 14B …… Monomer vapor generator, 22 …… Prepolymer 31 …… Diffusion treatment device, 32 …… Diffusion tube 33A, 33B …… Monomer gas generator, 34 …… Gel rod 62,67 ...... Monomer storage container

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuhiro Koike 2-15-24 Nakane, Meguro-ku, Tokyo Cyanbol No. 2 Metropolitan University No. 411

Claims (2)

[Claims] 1. A step of incompletely polymerizing one or more monomers Ma that form a network polymer Pa having a refractive index Na to form a transparent gel matrix having self-shape retention property, One or more types of monomers that form a polymer (including a copolymer) P b (where the refractive index is N b and Na ≠ N b ) in the transparent gel matrix
A step of polymerizing while diffusing M b, and, after the diffusion of M b , at least one kind or a plurality of kinds different from the monomer diffused immediately before the step is provided at intervals in the process of polymerization conversion of the base material. A method for producing a synthetic resin optical transmission body, which comprises at least one step of polymerizing a monomer while diffusing it. 2. The average polymerization conversion rate P k ( k = 1,2,3 ...
n) is within the range of 10% <P k <80%.