JPS59137904A - Method for producing plastic optial transmission body - Google Patents

Abstract

PURPOSE:To obtain a plastic optical transmission body of which the refractive index decreases in proportion to the square of the distance from a central axis over the entire part of said body by selecting a combination and mixing ratio of at least three kinds of monomers at which the monomers having the lower refractive indices are easier to copolymerize. CONSTITUTION:The figure indicating the example of the combination of ternary monomers is shown. The mixing ratio of the monomers varies with the kind of the monomers, the diameter of an optical transmission body, refractive index distribution, polymerizing conditions, etc. and is usually selected from the range of 20-90wt% M1, 2-40 M2 and 5-60 M3. A prescribed amt. of the monomers M1, M2, M3 are first mixed, and a prescribed amt. of a photopolymn. initiator (for example, benzoyl peroxide (BPO), benzoin methyl ether, etc.) is dissolved therein. The mixture is filled in a glass tube which has a prescribed bore (for example, about 2.9mm.) and is closed at one end, then the mixture is photopolymerized. A tubular UV lamp is provided at the center of the device, and cylindrical light shielding plates are attached in the upper and lower parts of the lamp so that the mixture in the glass tube is irradiated only with the UV light released from the central part of the tube.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a synthetic multi-layer optical transmission body having a refractive index distribution in which the refractive index gradually changes and having a low optical transmission loss.

A synthetic resin optical transmission body whose refractive index distribution is expressed by the formula (1) is a special specification "Sho 5it-3o3oi" (Special application Showa so-//7.2).
．． ? ) and JP-A-6T-/1190011 (Japanese Patent Application Sho!;!;-33920).

N −No (/ −−A, r2) (1) Here, No is the refractive index of the central axis, N is the refractive index of a point at a distance of r from the central axis, A is the constant of the refractive index distribution, and be.

The patent utilizes the fact that the composition of a copolymer changes with the progress of polymerization, and monomers M1 and M2 have different refractive index values when they become a polymer, and moreover, a transparent copolymer. Copolymerization starts from a predetermined portion of the monomer mixture, which is selected to form a copolymer and kept in a predetermined shape, and then copolymerization is carried out so that the resulting copolymer is continuously precipitated within the reaction system. By selecting conditions, an optical transmission body having a refractive index gradient can be manufactured.

The patent describes a method for producing a synthetic resin light transmission body having a refractive index gradient, in which the difference in refractive index when the polymer is formed is o,
two types of monomers (including monomer mixtures) Ml and M2 such that oos or larger,
And if the monomer reactivity ratios of monomers M1 and M2 in their copolymerization reactions are rl and r2, respectively, and the mixing molar ratio of monomers M1 and monomers I and M2 is (Ti)m, then , the value of /
, 1 or more or 1 or more /, / Holding a mixture of monomers M1 and M2 in a predetermined shape, such as a cylinder, and for a mixed object of the predetermined shape. By applying copolymerization conditions that are locally nonuniform, only a predetermined portion of the mixture, for example, the outer peripheral portion of a cylindrical mixture, has a ratio of M1 and M2 components that is different from the mixing ratio. A copolymer is formed locally, and then copolymerization gradually proceeds from that part to other parts, such as the central part, so that the copolymerization is carried out from the predetermined part to other parts inside the copolymer body. 7) describes a method for manufacturing a synthetic resin optical transmitter having a refractive index gradient, which has a concentration gradient in which the content ratio of M1 component and M2 component gradually changes.

Examples of combinations of monomers M and M2 include methyl methacrylate and vinyl benzoate, and alkyl methacrylate and phenylacetic acid beers. However, are these listed here? An optical transmitter obtained from a combination of μ-mers has a refractive index distribution expressed by equation (1) only near its central axis, and the gradient of the refractive index becomes extremely steep toward the periphery. Put it away. This is because the refractive index of the copolymer increases with polymerization, and although the increase is only about 1 μm at the beginning, it increases rapidly in the latter half of the polymerization. In order to obtain a rod-shaped convex lens by this method, the peripheral part must be scraped and removed to obtain a transmitter.As a result of intensive research, the present invention number is J-2, 0, that is,
X types of monomers (X is at least 3) that satisfy the following conditions Ml * M2 + M3...
The mixture of Mx is polymerized into a light transmitter by the polymerization method described in the above patent. In general, multicomponent copolymerization reactions are as follows. Growth reaction/LA#-al +MJ-→If the rate constant of MJ is kij, the reactivity ratio rij is rij
It is defined as w kii/kij , and there are X (X-/) reactivity ratios in the X element copolymerization.

Monomer combination 9 of the present invention (indicates the conditions to be satisfied. Now, two integers i, j are /≦i, j≦X, i)j. (1) Regarding the reactivity ratio: (Xj/Mj)m is the mixing molar ratio of monomer Mi and monomer xj.

(2) Regarding the refractive index, it is necessary that ni (refractive index of 14i homopolymer)>nj (refractive index of Mj homopolymer).

The case of X-3 will be specifically explained. In ternary copolymerization, the following nine types of growth reactions occur in competition.

* -wMl+Myo- SMl* (11 to rate constant) He M1*10M2→ hWM 2* (〃k12)* To Ml*+M3-”/%”M3 (tt k13)
A−v, M2 +M1→ −vswMl (u
k21) ~M2*+M2 → Satoshi M2*(u k22)~
-M2*+M3→Kishi M3*(u k23)* Dahe M3 +M1-+ w-J(tt k31
)~”M3 +M2-+ 7VIAIM2 (〃
32) -+M3 +M3→-M3 (u k33
) The monomer reactivity ratio is defined by equation (3).

r 12'! klx/k12 r21 = k22 / to 21 r13- to 11/to 13 (3) r31 = k33/ to 3x The conditions that the combination of monomers M 1 r M 21 M 3 of the present invention must satisfy are (1) reactivity Regarding the ratio, (Mi/Mj)m is the mixing molar ratio of monomer Mi and monomer Mj.

(2) Regarding the refractive index, nl (B (refractive index of 1 homopolymer) < n2 (refractive index of M2 homopolymer) < 13 ([3 homopolymer at least o
, oos is preferable.

Condition (1) is that as the ternary copolymerization progresses, the initial monomer M
1 polymerizes rapidly, followed by monomer M2, and monomer M3 polymerizes most slowly. In other words, the copolymer produced at the initial stage of polymerization has a 7 ml content, and the Ml content rapidly decreases, and in addition, the monomer Ml content decreases rapidly.
The content of 2 increases. As the polymerization progresses further, the content of M2 also decreases, and the content of monomer M3 increases. If condition (, 2) is satisfied, the refractive index of the copolymer produced will increase as the polymerization progresses, but by adjusting the type of monomer and the monomer charging ratio, the refractive index of the copolymer will increase as the polymerization progresses. The refractive index of the coalescence can be gradually increased over a wide conversion range with the polymerization conversion rate, and a sharp increase in the refractive index can be avoided.

An example of a combination of ternary monomers used in the present invention is Fang 1.
Listed in the table.

The mixing ratio of monomers depends on the type of monomer, the diameter of the optical transmitter,
Although it varies depending on the refractive index distribution bipolymerization conditions, etc., it is usually G;
iMl, 20~90, [2j~llO,M3
! selected from within the range of ~60% by weight.

Next, the present invention will be explained in detail.

First, a predetermined amount of monomer M'l 1M 2 r M 3 is mixed, and a predetermined amount of a photopolymerization initiator (for example, benzoyl peroxide (BPO), benzoin methyl ether, etc.) is mixed therewith.
Although it contains a large amount of monomer M1, as the polymerization progresses, the monomer M1 is dissolved and the monomer M1 is dissolved in a predetermined inner diameter (e.g., approximately, ;), 9 m.
m), filled a glass tube with one end closed, and photocopolymerized using the apparatus shown in FIG. A tubular ultraviolet lamp l is located at the center of the device, and cylindrical light-shielding plates are attached to the top and bottom of the lamp l, allowing the mixture in the glass tube q to be illuminated only by the ultraviolet light emitted from the central part of the tube. so that it is irradiated.

Note that /l is a brim-shaped auxiliary light-shielding plate provided so that the light from lamp l is emitted only to the interval between the light-shielding plates (for example, 7 mm).
is being monitored. A plurality of glass tubes filled with the monomer mixture are attached to the support member S at a predetermined distance, for example, 70 m from the ultraviolet lamp /, and the motor 6
For example, let it rotate at qO rotations per minute. First, the ultraviolet lamp / is placed at a position lower than the F end of the glass tube, and the lamp '/ is pumped with air at a constant temperature from the artificial gap using a fan 9 to be discharged. Therefore, the temperature rises, but the humidity remains constant at a level higher than the inlet air temperature. Photocopolymerization occurs from the bottom of the glass tube l.

Although the volume shrinks due to polymerization, the monomer mixture is always supplied from the upper part of the glass tube that is not undergoing polymerization, so no voids are created inside the polymer. As the lamp 1 moves, the portion to be polymerized gradually moves upward, and finally all of the monomer mixture in the glass tube solidifies. After a predetermined period of time, e.g., approximately 70 hours, from the start of irradiation, the glass tube is removed from the apparatus and placed in a gooc, for example.
(Heat for a period of time to polymerize as much of the remaining monomer as possible.

Next, the glass tube q is crushed and the copolymer rod is taken out. The refractive index distribution constant A of the rod exhibits a constant value over the entire rod except for both end portions.

The obtained light transmitting body is heated and stretched to obtain a light-focusing fiber. Prior to heating and stretching the rod, trace amounts of volatile substances contained in the rod are removed under reduced pressure of 10-3 to 10-4 mmHg.
I'll ask you questions every day.

Next, it is stretched using a hot stretching device whose principle is shown in FIG. That is, the above synthetic resin rod is attached as a preform 21 to the support member 1, lowered at a speed of 1 (mm/5ec), passed between constant temperature heaters 23 at a constant temperature T'd, and driven in the F direction. , the speed is 2 m by the roll 21.
Stretch and stretch at m/S e C.

V2/Vl is the stretching ratio. The obtained synthetic resin optical fiber 2j is cut and polished to form a rod lens of length /-Jmm, and from the lens action, the refractive index distribution constant A of equation (1) is obtained.
seek. In addition, a synthetic resin optical fiber is wound around a drum, a laser beam of 63 kozas A is input from one end, and the intensity of the light emitted from the other end is measured. Transmission loss is determined from the relationship between the length of the fiber and the intensity of the emitted light.

Examples are shown below.

Examples 1 to 1 Monomer M1 was methyl methacrylate (HMA) with a refractive index of /, 1L2, and M2 was a refractive index of /, t, 2.
.

Using acrylonitrile (AM) and M3 as a ternary system using the apparatus shown in the drawing, lenses were manufactured under the conditions shown in Table 2, and the results shown in the table were obtained.

In addition, the monomer reactivity ratio in formula (3) is r12-/,
31゜r13-tr, sco, r21-o, ico, r2
3-j, Os r31-(7,07.

r32-0.03, and (su,
(3).

The values on the left side of the equation (≦) are respectively /, #, J, jko and j, 4J, and all of them are (su, C3>,
Equation (4) was satisfied. In Examples 1 to 2, formulas (ri) to (6) were also satisfied.

Oko table example number l ko 3'I MMA (part) 4u t7. Ot
Fu01mu7) AN (department)
9. J lr, 2 z9 1JVB
(Department) JIAj J4! , #J
u 23.0BPO (part) Ql
O, ma i, o o, s ramp movement speed V (
mm/m1n) 0.7 0. A to 0.
1 refractive index distribution number A (10-3mm-2) yo4
1 'A63 3. /3,? ,,g70 radius Rp (II ml) /,113'/,1
13/, lj/, 41! The refractive index distribution of Example q is shown in FIG.

For comparison, MMA7j part and VB2! without using AN. The dotted line in Figure 3 shows the refractive index distribution in the case where an optical transmission body having the same dimensions as that of Example D was manufactured using the above-mentioned part.

An optical fiber of $ loss/, 2 (IBlm) was obtained.

Example 5 - IO Table 3 shows the manufacturing conditions and results of the optical transmission body manufactured using a ternary system other than MMA-AN-VB.

[Brief explanation of drawings]

FIG. 7 is a partial side view of an example of a manufacturing apparatus for explaining the present invention, and FIG. 1 Figure 19- Second cause

Claims (2)

[Claims] (1) When the monomer Xi becomes a polymer, the refractive index of
If i is at least three types of monomers (including one monomer mixture) where ni is different from each other, ' M 1+ M2 !
M 3......- to hold the mixture in a predetermined shape? By applying locally non-uniform co-consolidation conditions to a mixed body having a predetermined shape, first, only a predetermined portion of the mixed body has a ratio of monomer components that is different from the above-mentioned mixing ratio. After forming a copolymer locally, copolymerization gradually proceeds from that part to other parts, thereby creating a concentration gradient in which the odor component inside the copolymer body changes gradually. In the method for manufacturing each resin optical transmitter having a refractive index gradient, the monomer M
By selecting a combination of monomers such as i, a monomer with a low ni, and monomers that are easy to copolymerize, the refractive index of the entire optical transmitter decreases in proportion to the square of the distance from the central axis.・A method of manufacturing a synthetic resin optical transmission body. (2) The mixture of at least three monomers 6 is composed of monomers M1 + M2 and Mj, and Mi
The monomer reactivity ratio of Mj to (i+j −i, r, 3
) is expressed by rij, and the mixing molar ratio of Mi and Mj is. (r23(H)m+/) / (, (7)m+r32)
A method for manufacturing a Tanise resin optical transmission body according to claim 1, which satisfies all of the formulas >/-'/.