JP3124324B2 - Method for producing thermoplastic resin molded article for optical use - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an optical thermoplastic resin molded article such as an optical component, a plastic optical fiber preform, and an optical waveguide.

[0002]

2. Description of the Related Art This type of optical thermoplastic resin molding is
It is manufactured by extrusion molding or injection molding depending on the type of the molded body.

[0003]

However, these conventional methods for producing a molded article of an optical thermoplastic resin have various disadvantages. First, when the optical molded body is manufactured by extrusion molding, there are a large number of grooves in the resin passage of the extruder in which the resin formed by the screw is easy to accumulate,
The resin supplied simultaneously from the hopper to the extruder is not extruded at the same time, but partly adheres to the screw because it causes convection, and the resin adhered to this screw becomes a screw when the molding temperature is high. And is colored by the heat of Therefore, the colored resin is mixed with the subsequent resin and extruded, so that there is a disadvantage that the molded product is colored.

When an optical molded product is manufactured by injection molding, distortion occurs in the resin when the resin is solidified in a mold, so that the molded product is easily broken, and a molded product having such distortion is generated. Are not suitable for optical products. In addition, injection molding is not suitable for producing an elongated molded article or a molded article having a special shape.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical thermoplastic resin molding capable of producing a molded article without the above-mentioned drawbacks, without causing internal distortion and without causing coloring even at a high molding temperature. An object of the present invention is to provide a method for producing a body.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a thermoplastic resin filled in an opening mold.
Vacuum degassing while heating and melting the conductive resin , then
A method for producing a thermoplastic resin molded article for optical use , comprising sequentially cooling the thermoplastic resin from the bottom to the top of the mold while pressurizing the thermoplastic resin with an inert gas to produce the thermoplastic resin molded article for optical use. Is to do.

[0007]

As described above, the mold is filled in the mold having the opening.
Vacuuming and defoaming the heated thermoplastic resin while heating and melting it, no voids remain in the resin, and this
When the resin is pressurized with an inert gas, no cavities are formed inside the molded body. In addition, from the bottom of the mold to the top
By successively cooling, the strain is favorably released from the bottom to the top of the compact.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The method for producing an optical thermoplastic resin molded article of the present invention is as follows. A molding die made of a glass or metal container is filled with a thermoplastic resin as a molding material, and this molding die is placed in a thermostat. put, a thermoplastic resin heated solvent in the thermostatic chamber
Vacuuming and defoaming while melting , then injecting an inert gas into the thermostat, pressurizing the thermoplastic resin in the mold to form it, and finally gradually moving the thermostat from bottom to top And the mold is taken out of the thermostat to obtain a molded article for optical use.

The thermoplastic resin as a molding material may be either a crystalline resin or an amorphous resin. However, a resin which requires a molding temperature of usually 200 ° C. or higher is oxidatively degraded by an ordinary method. It is suitable for production by the method of the present invention because of its ease. Further, it is preferable that the thermoplastic resin has almost no volatile substances inside.

The thermoplastic resin can be filled in the form of pellets, powders or flakes at normal temperature into the mold, but may be filled by flowing at a molding temperature or lower in a fluid state. When the resin is poured in a fluidized state, it is preferable to perform it in a vacuum state.

When defoaming in a vacuum state in a thermostat,
Since impurities such as monomers mixed in the resin are removed and there is no contact with the outside, no impurities or foreign substances are mixed from the outside.If the molded article is an optical product, Has no effect.

The pressurization by the inert gas at the time of molding has a function of preventing generation of minute bubbles remaining in the thermoplastic resin outside the molding of the resin and voids due to shrinkage from inside the material at the time of cooling. If the pressure is too small, voids are generated inside the molded body, and if the value is too large,
Since the gas is too much dissolved in the material and voids are generated in the molded body, an appropriate value is set in between. still,
This pressure is several tens of kg, which is significantly lower than several hundred kgf / cm ² which is the pressure applied during the conventional injection molding.
Since a pressure on the order of f / cm ² is sufficient, when a brittle resin or an elongated resin is molded, cracking of the resin hardly occurs.

The reason why the thermostat is cooled from the bottom to the top when the optical molded body is cooled is that the optical distortion inside the molded body is released from the bottom to the top. By performing the process together with the pressurization with the inert gas, the voids inside the material can be sequentially moved upward to effectively remove the voids from the material.

In the case where the molded body formed by cooling in this manner is stretched later, before the stretching, drying is performed in an atmosphere in which a vacuum state is sufficiently maintained while maintaining the temperature at or below the glass transition point. Is preferred. This way,
The gas dissolved in the molded body is sufficiently released to the outside, and a high-quality optical product is manufactured.

It is preferable to apply a release material to the molding die in order to facilitate the peeling of the molded body after the molded body is formed. The release liner is used smoothness and soluble fluorine resin fluorocarbon solvent in consideration of the optical effects of the resin, for example, main chain fluorine resin having an alicyclic group or multiple heterocyclic group fluorine-substituted Is preferred. In addition, it preferably has a glass transition point higher than the softening point of the thermoplastic resin forming the molded article. These fluorocarbon resins soluble in fluorine carbide are dissolved in a solvent, applied to the inner surface of the mold, and then the solvent is removed and adhered to the mold. As described above, when a fluorine resin soluble in fluorine carbide is used by dissolving it in a solvent, the surface of the molded body is not roughened as in the case of using a fine particle release material. In the case of the preform, there is no increase in transmission loss. Also, when a fluororesin is dissolved in a solvent and applied to a mold, a uniform film of a release material can be formed on the surface of the mold,
Therefore, if the surface of the mold is a mirror surface, the film surface of the release material is also a mirror surface, and the surface of the molded body is also a mirror surface. Furthermore, after molding of the molded article, the fluororesin adhering to the surface of the mold can be easily removed by dissolving it in a fluorocarbon solvent. The fluorocarbon resin soluble in fluorine carbide has heat resistance to maintain a peeling effect even when exposed to high temperature, and therefore can be used for a resin molded at high temperature. Further, the release material is preferable because it has a function of preventing impurities from the mold from migrating to the resin as the molding material and does not adversely affect the quality of the optical product.

Next, some specific examples of the present invention will be described together with comparative examples. (Specific Example 1) As shown in FIGS. 1 and 2, a Teflon AF2400 (trade name, manufactured by DuPont) was used as a release material on a solvent of Fluorinert FC-72 manufactured by Sumitomo 3M on the inner surface of a cylindrical mold 10 having an open top surface . A release material formed by dissolving 0.5% was applied and dried sufficiently. The molding die 10 was filled with a molding material, polycarbonate Panlite AD-5503 (trade name, manufactured by Teijin Chemicals) through an opening , and was placed in a thermostat 12 shown in FIG. The polycarbonate panlite was filled after drying at 120 ° C. for 120 hours. The constant temperature bath 12 has five zones of heaters H1 to H5 and cooling fans F1 to F5, and is connected to a vacuum source V and an inert gas source I such as argon gas via a switching valve B at the upper part. I have. In FIG. 3, reference symbol M denotes a pressure gauge, and C denotes a pressure gauge.
Is a water cooling pipe provided on the upper part of the thermostat 12, and L is a leak valve.

The five heater areas H1 to H of the thermostat 12
5, the switching valve B was switched to the vacuum source V to evacuate the vacuum while maintaining the temperature of the thermostat 12 at 250 ° C., and this state was continued for about 1 hour to defoam the molding material. Next, the switching valve B was switched to the inert gas source I side, and argon gas was introduced into the thermostat 12, and the pressure was maintained at 10 kgf / cm ² for about 10 minutes. After that, first, the lowest heater H1 is turned off and the fan F1 is driven at the same time, and after 10 minutes, the next heater H2 is turned off and the fan F2 is driven at the same time. By driving, the mold 10 was sequentially cooled from below.

In this way, after 90 minutes, the leak valve L was opened, the inside of the thermostat 12 was set to the atmospheric pressure, and the mold 10 was taken out. The molded body obtained in this way is 10 cm
The end face was hot-plated and the transmittance was measured. The light transmittance at 660 nm was 86.
%Met.

(Specific Example 2) As shown in FIGS. 4 and 5,
The same release material as in Example 1 is applied to the inner surface of a cylindrical molding die 14 having a rod-shaped portion 14a at the center, and the same molding material as in Example 1 is filled. Then, a molded article was produced. In exactly the same manner as in Example 1, the molding die 12 is placed in a thermostat 12 shown in FIG. 3, heated, evacuated, pressurized with an inert gas, and cooled from below to form a cylindrical molded body. Was manufactured. This cylindrical formed body can be used as it is as an optical waveguide, and when used as an optical fiber clad, the formed body is drawn into a tube. An optical fiber can be obtained by pouring a thermosetting resin having a high refractive index into the tube and curing the resin. The optical fiber thus obtained is preferable because the inner surface of the tube is extremely clean and the transmission loss is small. In particular, when a molding material is molded from polymethylpentene or an ethylene-tetrafluoroethylene copolymer instead of polycarbonate, a core material (thermosetting resin) is easily selected from the problem of the refractive index.

(Specific Example 3) As shown in FIGS. 6 and 7,
The same release material as in Examples 1 and 2 is applied to the inner surface of a molded body 16 composed of a square pillar having four square rods 16a therein, and the same molding as in Examples 1 and 2 is performed in the molding die 16. The material was filled. In exactly the same manner as in Example 1, this mold 12 was placed in a thermostat 12 shown in FIG.
After evacuation, pressurization with an inert gas and cooling from below were performed to produce a rectangular column-shaped molded body 18 having four rectangular cavities inside as shown in FIG. This rectangular column shaped body 18 can be cut as shown in FIG. 9 and both ends can be optically polished to form an optical waveguide 20.

(Specific Example 4) Exactly the same as Specific Example 1, except that a polyarylate P-5001 manufactured by Unitika was used as a molding material instead of polycarbonate, and a thermostat 12 was used.
The inside temperature was maintained at 310 ° C. to produce a molded body. This molded body was cut into a length of 10 cm, and the end face was subjected to hot plate treatment to measure the transmittance. As a result, the light transmittance at 660 nm was 68%.

(Specific Example 5) Exactly the same as Specific Example 1, except that polyether sulfone manufactured by Mitsui Toatsu Chemicals was used instead of polycarbonate as the molding material, and the temperature in the thermostat 12 was maintained at 330 ° C. Thus, a molded body was produced. The molded body thus obtained also had good shape and optical characteristics.

(Example 6) As shown in FIGS. 10 and 11, which are similar to the molds of FIGS.
The same release material as that used in Example 1 was applied to the inner surface of the cylindrical mold 22 having a as the release material, and was sufficiently dried. The mold 22 was placed in a thermostat 24 shown in FIG. The thermostatic chamber 24 has a funnel R provided so as to communicate with the upper opening 22b of the molding die 22 therein, and a heater H is provided on the peripheral surface. In the drawing, the same reference numerals as those in FIG. 3 indicate the same parts.

On the other hand, a flaky polycarbonate L-1250 manufactured by Teijin Chemicals, which is a pre-weighed molding material, is filled through the funnel R of the thermostatic chamber 24, and the switching valve B is maintained while the inside of the chamber is maintained at 260 ° C. by the heater H. Is the vacuum source V
And maintained this state for 3 hours. The molding material was filled after drying at 120 ° C. for 120 hours. After defoaming, the switching valve B is switched to the inert gas source I side, and argon gas is introduced into the thermostat 24, and 10 kgf is applied for about 10 minutes.
/ Cm ² was maintained. After that, the heater H was removed, and the portion covered with the heater was brought into contact with water sequentially from below to cool from below.

Thereafter, the leak valve L is opened to open the thermostat 1
The inside of 2 was set to atmospheric pressure, the molding die 22 was taken out, and a molded body 26 shown in FIG. 13 was manufactured. The molded body 26 was cut as shown in FIG. 14 and both ends were optically polished to form a good optical waveguide 28. It is to be noted that the molded body 26 can be drawn and used for an optical fiber clad.

Comparative Example 1 A polycarbonate panlite AD-5503 manufactured by Teijin Chemicals was used as a molding material, and this material was injected into a mold 30 shown in FIG. 15 from an injection molding machine having an inner diameter of 65 mm. Silicone oil is applied to the inner surface of the mold 30 as a release material.
Maintained at 0 ° C. After the molding, the mold was cooled and the molded body was taken out. The molded body thus obtained was cut into 10 cm, its end face was subjected to hot plate treatment, and the transmittance was measured. As a result, the light transmittance at 660 nm was as low as 58%. In addition, it was confirmed that one was cracked after four were produced.

Comparative Example 2 The same molding material as in Comparative Example 1 was similarly injected from an injection molding machine into a mold 30 shown in FIG. Ceramic powder was applied to the inner surface of the mold 30 as a release material, and the temperature of the mold 30 was maintained at 260 ° C. The molded body obtained in this comparative example was cut into 10 cm,
The end face was subjected to a hot plate treatment, and the transmittance was measured. The light transmittance at 660 nm was 79%. However, after manufacturing five pieces, it was confirmed that four pieces had cracks.

[0028]

According to the present invention, as described above,
Vacuum while heating and melting the thermoplastic resin filled inside
Since defoaming and come, without voids remain in the resin,
In addition, since the resin is molded by pressurizing it with an inert gas, no cavities are formed inside the molded body, and furthermore, since the cooling is sequentially performed from the lower part to the upper part of the mold, the strain can be released favorably. Good quality molded products can be manufactured.

[Brief description of the drawings]

FIG. 1 is a front view of a molding die used in a specific example of the present invention.

FIG. 2 is a top view of the mold of FIG.

FIG. 3 is a side view of a thermostat used in a specific example of the present invention.

FIG. 4 is a front view of a molding die used in another embodiment of the present invention.

FIG. 5 is a top view of the mold of FIG. 4;

FIG. 6 is a front view of a molding die used in still another embodiment of the present invention.

FIG. 7 is a top view of the mold of FIG. 6;

FIG. 8 is a front view of a molded body molded by the molding dies of FIGS. 6 and 7.

9 is a front view of an optical waveguide obtained from the molded body of FIG.

FIG. 10 is a front view of a molding die used in still another embodiment of the present invention.

FIG. 11 is a top view of the mold of FIG. 10;

FIG. 12 is a front view of a thermostat in which the molds of FIGS. 10 and 11 are used.

FIG. 13 is a front view of a molded body molded by the molding dies of FIGS. 10 and 11;

FIG. 14 is a front view of an optical waveguide obtained from the molded body of FIG.

FIG. 15 is a front view of a mold used in a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Mold 12 Thermostat 14 Mold 16 Mold 18 Mold 20 Optical waveguide 22 Mold 24 Thermostat 26 Mold 28 Optical waveguide

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI G02B 6/13 G02B 6/12 MB29K 69:00 81:00 B29L 11:00 (58) Fields surveyed (Int.Cl. ⁷ , DB name) B29C 39/02 B29C 39/22-39/42 B29C 43/02 B29C 43/32-43/56 B29B 11/06-11/12

Claims (1)

(57) [Claims] 1. A thermoplastic filled in an opening mold.
Vacuumed and defoamed while heating and melting the resin, then prior to
A method for producing a molded article for optical thermoplastic resin, characterized by producing a molded article for optical thermoplastic resin by sequentially cooling the thermoplastic resin from the lower part to the upper part of the mold while pressurizing the thermoplastic resin with an inert gas.