JPH0580642B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a preform rod for manufacturing a gradient index optical transmission body for image transmission made of synthetic resin.

As a gradient index optical transmitter that can be used as an image transmitter, a glass fiber body in which the refractive index gradually decreases from the central axis toward the surface has been proposed in Japanese Patent Publication No. 1981-816. However, such glass image transmitting bodies have problems in that they have low productivity, are expensive, and have poor flexibility.

In contrast to such a glass image transmitting body, a method of manufacturing a synthetic resin image transmitting body that is highly productive and has excellent flexibility has been proposed. These synthetic resin image transmitters can be roughly divided into: (1) those in which the concentration of metal ions is continuously changed from the central axis of a synthetic resin cylinder made of an ionically crosslinked polymer toward its surface (especially (2) A synthetic resin rod (preform rod) made from a mixture of two or more transparent polymers with different refractive indexes is treated with a specific solvent, and the synthetic resin is A rod-shaped body having a refractive index distribution by partially dissolving and removing at least one of the constituent components of the rod-shaped body (Japanese Patent Publication No. 47-28059); A mixture of different monomers is placed in a cylindrical container, and the polymerization method is devised to create a copolymer composition distribution that produces a continuous refractive index distribution from the surface to the inside (Japanese Patent Publication No. 54-30301) ), (4) From the surface of a cylindrical cross-linked polymer (preform rod), a monomer forming a polymer having a refractive index lower than that of the cross-linked polymer is diffused from the surface to the inside, and the monomer is After arranging the monomers so that the content thereof changes continuously, the polymerization reaction of the monomers is carried out to give a cylindrical object a refractive index distribution (Japanese Patent Publication No. 52-5857) and (5) diffusing and reacting a low-molecular compound that reacts with the reactive groups of the polymer and lowers the refractive index of the polymer from the surface of the reactive polymer cylinder (preform rod). A cylindrical object with a continuous refractive index distribution from the surface to the inside
29682) etc.

In manufacturing these image-transmitting synthetic resin bodies, except for manufacturing method (3), a cylindrical preform rod is prepared in advance, and then this cylindrical object is subjected to a treatment to impart a refractive index distribution. It requires a two-step process. In order to impart clear image transmission to a cylindrical object in the post-process, the preform rod created in the pre-process must have high roundness, low outer diameter variation, and a smooth surface. Not only that, but also during the formation of the refractive index distribution in the subsequent process, it is necessary for these cylindrical objects to maintain high roundness, low outer diameter variation, and smooth surface shape as much as possible.

The conventionally known molding method for preform rods is the so-called melt-forming method in which preform rod molding resin is extruded through a precision-machined orifice. The resin extruded through an orifice, which has the highest processing precision, can only be applied to low molecular weight resins whose heated molten state is relatively stable and whose melt viscosity is relatively low. The preform rod, which is not only extremely narrow but also has high processing accuracy, causes a flow phenomenon during the subsequent process of forming the refractive index distribution using the refractive index distribution forming agent, making it extremely difficult to maintain the shape stably. The problem is that

In order to solve these problems in the post-process, it is possible to increase the molecular weight of the resin that makes up the preform rod, or to introduce a cross-linked structure into the resin that makes up the preform rod. A method is used to stabilize the shape of the rod during the process. However, it is difficult to make preform rods by melt shaping using resins that have a high molecular weight or have a crosslinked structure introduced into the resin structure, so plastic tube-shaped containers are used. Therefore, the method of casting and shaping the monomer for resin production using a glass container or the like is inevitable. The method of obtaining a preform rod by casting using such a container not only requires a container with high processing precision, but also requires polymerization conditions that take into account the volume change of the monomer that occurs within the container during polymerization. It is necessary to set the length, and since it is not possible to continuously create long lengths, productivity is also extremely low.

The inventors of the present invention have conducted intensive studies on a method for solving the problems of the conventional preform rod shaping method for manufacturing a gradient index optical transmitter made of synthetic resin, and have developed the following method. By using such a shaping method, it is possible to continuously manufacture preform rods that have high shaping precision and can maintain high shaping precision even during the formation of refractive index distribution in the subsequent process. They discovered this and completed the present invention.

That is, in the present invention, 0.02 to 5 parts by weight of a photopolymerization initiator is mixed with 100 parts by weight of a composition containing 80 to 20 parts by weight of an amorphous polymer and 20 to 80 parts by weight of a photopolymerizable monomer. After extruding a photocurable composition with a viscosity of 100 to 1,000,000 poise (measured at 60℃) from a nozzle, it is photocured by irradiating active light from the surrounding area, creating a refractive index gradient optical transmission with extremely high dimensional accuracy. The present invention provides a new method for continuously manufacturing preform rods for body manufacturing.

Examples of the amorphous polymer constituting the photocurable composition used in carrying out the present invention include methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, 2-
Homopolymers consisting of ethylhexyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, furfuryl methacrylate, glycidyl methacrylate, β-methylglycidyl methacrylate, hydroxyethyl methacrylate, and 1,4-butanediol methacrylate, diethylene glycol bisallyl carbonate, etc. or copolymers, copolymers of one or more of these monomers with methacrylic acid, styrene, α-methylstyrene, methyl acrylate, and ethyl acrylate, or polycarbonates.

These polymers can be produced by techniques commonly used in industry, such as bulk polymerization, suspension polymerization, emulsion polymerization, and solution polymerization. The polymer used is preferably one made by bulk polymerization because it has high optical purity.

Furthermore, although there is no particular restriction on the molecular weight of these polymers, if the molecular weight is too high, it will take a long time to stir and mix to obtain a uniform composition when preparing a photocurable composition, resulting in poor workability. descend. Therefore, it is preferable to use a polymer having a number average molecular weight in the range of 20,000 to 1,000,000.

Specific examples of photopolymerizable monomers constituting the photocurable composition used in carrying out the present invention include:
Glycidyl methacrylate, β-methylglycidyl methacrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate,
n-butyl methacrylate, sec-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, phenyl methacrylate,
Benzyl methacrylate, cyclohexyl methacrylate, hydroxyethyl methacrylate, hydroxyethyl acrylate, hydroxypropyl methacrylate, 1,4-butanediol methacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, ethylene glycol diallyl carbonate , pentaerythritol diacrylate, pentaerythritol dimethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, pentaerythritol tetraacrylate,
diethylene glycol bisallyl carbonate,
Pentaerythritol tetramethacrylate, trimethylolpropane diacrylate, trimethylolpropane dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, dipentaerythritol hexaacrylate, dipentaerythritol pentaacrylate, dipentaerythritol tetraacrylate, dipentari Erythritol triacrylate, tetrahydrofurfuryl acrylate, 2,2-bis(4-acryloyloxydiethoxyphenyl)propane, 2,2-bis-(4-acryloyloxypropoxyphenyl)propane, isophorone diisocyanate diacrylate, hexa Examples include methylene diisocyanate diacrylate, xylylene diisocyanate diacrylate, and ethyl carbitol acrylate. One or more of these may be added to form a photocurable composition.

The photopolymerization initiator constituting the photocurable composition used in carrying out the present invention includes p-tert-
Examples include butyl trichloroacetophenone, 2,2-diethoxyacetophenone, benzophenone, Michler's ketone, benzyl, benzoin, benzoin ethers, benzyl dimethyl ketal, thioxanthone, and the like. These are 1 type or 2
A photocurable composition is prepared by adding more than one species.

The composition of the polymer, monomer, and photoinitiator constituting the photocurable composition used in the present invention is from polymer 80 to
This is carried out by adding 0.02 to 5 parts by weight of a photopolymerization initiator to 100 parts by weight of a composition containing 20 parts by weight of a monomer and 20 to 80 parts by weight of a monomer. If the content of the polymer contained in 100 parts by weight of the composition including the polymer and monomer exceeds 80 parts by weight, the viscosity will become too high and the workability will be significantly reduced when preparing the photocurable composition. Not only does this worsen, but it also becomes difficult to obtain a uniform composition. In addition, the molecular weight of the polymer contained in the preform rod obtained by photocuring the photocurable composition discharged from the orifice with active light is also low, making it difficult to use in the post-process of the preform rod. The shape stability of the preform rod during formation of the refractive index distribution also deteriorates. On the other hand, if the polymer content in the polymer-monomer mixture is less than 20 parts by weight, the viscosity will be too low when extruding the photocurable composition from the orifice, and the outer diameter of the resulting preform rod will vary. becomes larger. Therefore, the content of the polymer contained in 100 parts by weight of the composition including the polymer and monomer needs to be set in the range of 80 to 20 parts by weight.

The content of the monomer contained in 100 parts by weight of the composition including the polymer and monomer is determined in consideration of the content of the polymer. For the same reason as the content of the polymer, it is necessary to set the monomer contained in the composition in the range of 20 to 80 parts by weight.

If the amount of the photopolymerization initiator added to 100 parts by weight of the composition including the polymer and monomer is less than 0.02 parts by weight, the photocuring speed of the composition will decrease significantly, making it difficult to produce preform rods. On the other hand, if the amount exceeds 5 parts by weight, the preform rod made from the composition becomes discolored and its light transmittance becomes poor. Therefore, the amount of photopolymerization initiator added to 100 parts by weight of the mixture of polymer and monomer is preferably set in the range of 0.02 to 5 parts by weight.

In addition, when preparing a photocurable composition, hydroquinone,
It is permissible to add a thermal polymerization inhibitor such as p-methoxyphenol. However, since adding a large amount of these thermal polymerization inhibitors may cause discoloration of the photocurable composition or reduce the photocuring speed, it is preferable to reduce the amount as much as possible.

In the present invention, as a method for extruding the photocurable composition through an orifice and forming it into a preform rod, it is possible to use ordinary melt spinning technology, wet spinning technology, dry spinning technology, etc. For example, an orifice at the tip and a metering pump can be used. A method using a screw extruder with can give.

In order to improve the shaping precision of the preform rod, the hole diameter of the orifice and its L/D should be optimized according to the viscosity of the photocurable composition at the extrusion temperature and the desired diameter of the preform rod. Good. Normally, it is preferable that the hole diameter of the orifice is 1 to 10 times the diameter of the preform rod to be manufactured, and the L/D of the orifice is 1 to 10 times the diameter of the preform rod to be manufactured.
The range is preferably from 100 to 100, more preferably from 2 to 50.
It is.

In the present invention, the photocurable composition is formed into a rod shape and then photocured, and a high pressure mercury lamp is preferably used as the active light source used here.
The active light here refers to light that can photolyze the photopolymerization initiator added to the photocurable composition and generate radicals, and generally refers to ultraviolet light with a wavelength of 400 nm or less. Any light source can be used as long as it efficiently generates light, and is not limited to the high-pressure mercury lamp. The atmosphere during exposure of the excipient of the photocurable composition may be either air or inert gas, but in order to increase the curing speed, inert gas is preferable.

Furthermore, in order to obtain a preform rod with high shaping precision, it is necessary to make the amount of irradiated light as uniform as possible around the discharged material of the photocurable composition. To do this, you can arrange multiple light sources symmetrically around the rod-shaped object from which they are emitted, create reflective walls or light-scattering walls, or rotate the light source around the rod-shaped object to irradiate the rod-shaped object. It is preferable to make the amount of light uniform.

An example of a manufacturing apparatus suitable for carrying out the present invention is shown in FIGS. 1 and 2.

FIG. 1 is a drawing showing the configuration of a photocurable composition blending apparatus.

An amorphous polymer, a photocurable monomer, a photopolymerization initiator, and a thermal polymerization inhibitor are charged into a mixing pot 1. The mixing pot 1 is equipped with a cooling pipe 2, a vacuum pot 3 connected to the tip thereof, a nitrogen supply pot 4, and a stirring blade 6 driven by an induction motor 5, and a heater 7 and a stirrer 8 are connected from the outside. It is heated in a silicone oil bath 9 equipped with. Predetermined materials are put into the mixing pot 1, and the vacuum pot 3 connected to the tip of the cooling pipe 2 is opened to reduce the pressure in the mixing pot 1, followed by heating and stirring. After stirring the added photopolymerizable composition so that it becomes uniform,
Open the nitrogen supply pot 4, pressurize the inside of the mixing pot 1 while watching the pressure gauge 10, set the extrusion cylindrical tube 11 to the extraction port at the bottom of the pot, open the ball pot 12, and add the light-curing mixture mixed into the cylindrical tube 11. The sexual composition is injected under pressure. The injection state is observed with a mirror 13 installed at the bottom of the cylindrical tube 11. When the inside of the cylindrical tube 11 is almost filled with the photocurable composition, the ball caulk 12 is closed and the die 16 is placed at one end of the cylindrical tube 11. After installation, extrusion with a piston is performed from above at a constant speed using the constant speed ram extrusion device shown in FIG. 14 is a jack, and 15 is a frame.

FIG. 2 is a diagram showing the configuration of a preform rod manufacturing apparatus.

A die 16 having a precisely machined nozzle is attached to one end of the cylindrical tube 11 and set in the heating furnace 17.
A linear head 20 (a device that converts rotational motion into linear motion) and an extrusion piston 21 driven by a motor 18 and a deceleration gear 19 are set vertically on top of the extruder, and the die 16 is moved at a constant speed. The photocurable composition is extruded into a Pyrex glass cylinder 22. Nitrogen is supplied into the Pyrex glass cylinder 22 from a nitrogen inlet 23,
A nitrogen atmosphere is maintained, and a high-pressure mercury lamp 24 and a light-reflecting aluminum cylinder 25 are placed around the periphery.
The photocurable composition extruded into a cylindrical shape is photocured with active light emitted from a high pressure mercury lamp 24,
By picking it up with the Nitsu roller 26,
A preform rod 27 with high shaping accuracy is manufactured.

Cross-sectional views taken along the plane A-A' and B-B' in FIG. 2 are shown as FIG. 2A and FIG. 2B, respectively.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 A mixture of β-methylglycidyl methacrylate, 500 ppm of polymerization initiator azobisisobutyronitrile, and 1500 ppm of chain transfer agent was surrounded by a soft vinyl chloride gasket with a thickness of 8 mm and a length of
It was injected between two tempered glass plates with a 650mm x 400mm wide surface covered with a 100μ thick polyester film, adjusted so that the distance between the top and bottom glass plates was 7mm, and immersed in a hot tub at 70℃ for 18 hours. Then, the polymerization was completed by heating in an air heating oven at 110° C. for 2 hours, and after cooling to room temperature, the resin was peeled off from between the glass plates to obtain a colorless and transparent resin plate.

This resin plate was pulverized using a pulverizer installed in a clean box to produce polyβ-methylglycidyl methacrylate powder. This polymer was dissolved in chloroform to make a 3wt% solution, and the specific viscosity (ηsp/c) was measured to be 0.78 dl/g. 1 kg of this polymer, 500 g of β-methylglycidyl methacrylate, 5 g of ethylene glycol dimethacrylate, 100 mg of hydroquinone, and 1 g of benzoyl methyl ether were placed in the mixing pot shown in Figure 1, and the mixture was heated at 80°C under a reduced pressure of 100 mmHg for 5 hours. After stirring and mixing, nitrogen gas was introduced and the mixture was pressurized at a pressure of 4 kg/cm ² . The ball pot at the bottom of the mixing pot was opened and the mixture was press-fitted into a stainless steel cylindrical tube with an inner diameter of 30 mm. A die with a precisely machined nozzle with a hole diameter of 6 mm and L/D = 15 is attached to one end of the cylindrical tube, and the die is placed in the heating furnace of the preform rod manufacturing equipment shown in Fig. 2, and the upper linear head is used for extrusion. Set the piston and linear head vertically, heat the furnace to 60°C, push the piston, and pour the photocurable composition (viscosity 65,000 poise) into a 50 mm diameter Pyrex glass cylinder filled with nitrogen gas from the die. The material was extruded into a cylindrical shape, irradiated with light from a high-pressure mercury lamp from the periphery to be photocured, and then removed using a nip roller. The descending speed of the linear head and the take-up speed of the nip roller are
The diameter of the photocured preform rod was adjusted to 3 mm. The photocured preform rod was cut into appropriate lengths and placed in an air heating oven at 110° C. for 2 hours to complete polymerization.

Using a laser outer diameter measuring device with a reading accuracy of 1μ, we measured the roundness and diameter variation rate expressed by formulas (1) and (2) below, and found that the roundness was 0.1%.
The diameter variation rate was 0.4%, which showed very good dimensional accuracy.

Roundness: |1-γb/γa|×100 (%)……(1) γa: Long axis of rod cross section γb: 〃 Short axis Diameter fluctuation rate: γmax−γmin/γmax×100(%)……( 2
) γmax: Maximum diameter measured along the length of a 50 cm long rod. γmin: Minimum diameter measured along the length of a 50 cm long rod. After cutting into 10 small rods and immersing them in absolute ethanol at 70°C for 24 hours, the ethanol absorption rate of each preform rod was determined by the following equation (3) as the weight of the preform rod before immersion (W ₀ ), preform rod weight after soaking
(W): Absorption rate = W - W ₀ / W ₀ × 100 (wt%) When measured, it was in the range of 30wt% = 0.3%, showing an extremely stable degree of swelling, and is suitable for manufacturing graded index optical transmission. Performance as a preform rod was extremely stable.

Ethanol absorption rate = W - W ₀ / W ₀ (wt%) ... (3) W ₀ : Rod weight before immersion W: Rod weight after immersion Example 2 Commercially available methyl methacrylate polymer (Acrypet VH, Mitsubishi Rayon) company) pellets 1Kg,
A photocurable composition (viscosity
55,000 poise) was extruded to create a preform rod with a diameter of 3 mm.

When the roundness and diameter variation rate were measured using the same method as in Example 1, the roundness was 0.1% and the diameter variation rate was 0.1%.
It had an extremely high dimensional accuracy of 0.3%.

This preform rod was cut into a length of 5 cm, divided into 10 small rods, and the ethanol absorption rate was measured under the same conditions as in Example 1. The ethanol absorption rate was in the range of 43 wt% ± 0.2% for each rod, which was extremely high. It showed a stable degree of swelling.

[Brief explanation of the drawing]

Fig. 1 is a drawing showing the configuration of a photocurable composition mixing device, Fig. 2 is a drawing showing the configuration of a preform rod manufacturing device, and Fig. 2A is a sectional view taken along the plane A-A' in Fig. 2. , FIG. 2B is a sectional view taken along line B-B' in FIG. 1...Blending pot, 11...Cylindrical tube, 12...Ball pot, 16...Dice, 17...Heating furnace, 20...Linear head, 21...Piston, 24...High pressure mercury lamp, 27...Preform rod.

Claims (1)

[Claims] 1 80 to 20 parts by weight of amorphous polymer, photopolymerizable monomer
Viscosity of 0.02 to 5 parts by weight of photopolymerization initiator mixed to 100 parts by weight of the composition mixed in the range of 20 to 80 parts by weight
A method for producing a preform rod for producing a gradient index optical transmitter, which comprises extruding a photocurable composition of 100 to 1,000,000 poise from a nozzle and then photocuring it by irradiating active light from the surrounding area. .