JPS63309547A - Optical resin molding - Google Patents

Abstract

PURPOSE:To obtain the title low-refractive index molding having a low water absorptivity and excellent dimensional stability, heat resistance and mechanical strengths, by mixing an aromatic vinyl polymer formed by polymerizing a monomer so that a specified relationship may hold between its melt flow or intrinsic viscosity and a weight fraction with a polyphenylene ether. CONSTITUTION:A polymer (A) based on an aromatic vinyl monomer and having a melt flow [MFR]FS of 0.5-200g/10min, obtained by (co)polymerizing an aromatic vinyl monomer alone or 50wt.% or above this monomer and other copolymerizable monomers, is mixed with a polyphenylene ether (B) having repeating units of formula I (wherein R<1-4> are each H, a halogen or a hydrocarbon group) and having an intrinsic viscosity [eta]PPE of 0.3-0.7 (in CHCl3 at 25 deg.C) so that the relationships of formulas II and III (wherein WFS is the weight fraction of component A, and WPPE is the weight fraction of component B) may hold. The obtained mixture is melt-kneaded under a high shear, and injection-molded at, for example, 270-350 deg.C into any desired shape.

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to an optical resin molded article.

The present invention relates to molded articles of optical elements such as optical disk substrates, lenses, and prisms made of specific resins.

<Conventional technology> A method of detecting recorded information etched in minute irregularities on a disk substrate using a laser beam spot and reproducing images and sounds, and furthermore, the optical properties of the recording film provided on the substrate surface. Due to changes in information technology, recording and reproducing systems that perform high-density information recording and reproducing have recently attracted attention.

In addition to being transparent, a disk substrate used in such a recording/reproducing system is required to have characteristics such as good dimensional stability, optical homogeneity, and low birefringence.

By using a resin material as a disk substrate, it is possible to mold a large number of replicated substrates at low cost.7 However, in many cases, when molding a disk substrate, molecular orientation occurs during the flow and cooling process of the resin, resulting in birefringence. It is widely known that this occurs, and this is a fatal flaw.

Since molecular orientation during molding is difficult to avoid, especially in injection molding, the only resin material with low optical anisotropy suitable for molding optical disc substrates is a polymer whose main component is methyl methacrylate. is the current situation.

However, when conventionally known polymers containing methyl methacrylate as the main component are used for substrates, they have poor dimensional stability due to their high hygroscopicity, causing warping and twisting in humid environments. It has its drawbacks.

Regarding this drawback, for example, Nikkei Electronics (1
(June 7, 1982, p. 133), and for this reason, aromatic polycarbonate resins with low moisture absorption are used as materials for acoustic compact discs.

On the other hand, since aromatic polycarbonate resins contain highly anisotropic aromatic rings in their main chains, it is difficult to reduce the birefringence of molded substrates. However, because the birefringence is caused by the material itself, it is not possible to stably manufacture a substrate with uniformly low birefringence, and the low birefringence substrate is larger in diameter than an acoustic compact disc. It is extremely difficult to manufacture substrates by injection molding.

In addition, in order to improve the dimensional stability, which is a drawback of polymers mainly composed of methyl methacrylate, for example, JP-A-57-3
Copolymers of methyl methacrylate and aromatic vinyl monomers have been proposed in JP-A No. 3446, JP-A-57-162135, and JP-A-58-88843.

However, copolymers with vinyl monomers having an aromatic ring tend to produce large birefringence and cannot be put to practical use.

Although even better birefringence and dimensional stability are required for disk substrates that can perform not only reproduction but also recording of information, a resin material that fully satisfies these requirements has not yet been found. do not have.

Furthermore, although resin materials such as methacrylic resin are conventionally used for other optical elements such as lenses and prisms, resin materials with low birefringence, heat resistance, mechanical strength, and dimensional stability are also used. are in demand.

U.S. Pat. No. 4,373,065 discloses that two types of polymers having opposite optical anisotropy but completely compatible are mixed in a composition that exactly cancels out the optical anisotropy,
An optical recording element made of an optically isotropic resin with substantially zero birefringence is disclosed.

Furthermore, the publication describes a system using polyphenylene ether and polystyrene as polymers with opposite optical anisotropy, even if stress is applied to a film made from a mixture of compositions that exactly cancel out the optical anisotropy. It has been shown that there is no birefringence, that is, no birefringence occurs when stress is applied to the solid state polymer composition.

:Problems to be Solved by the Invention> The above-mentioned U.S. Pat. There is no indication that the birefringence of the compound is significantly reduced.

The inventors have discovered that two types of polymers, which have opposite optical anisotropy in the solid state but are completely compatible, can be mixed in a composition in which the optical anisotropy in the solid state is expected to be exactly canceled out. It has been found that when optical elements such as optical disk substrates are molded by injection molding, which is a recent manufacturing method, the birefringence of the resulting molded product is not necessarily small.

In other words, when trying to create an optical material such as an optical disk substrate by injection molding using a polymer composition as a raw material, it is not enough to simply create a composition that takes into account the optical anisotropy of each individual polymer in the solid state. Therefore, it is not possible to obtain an optical material with low birefringence.

Furthermore, in recent years, attempts have been made to manufacture disk substrates for erasable and rewritable magneto-optical disks from plastic.

In this way, when reading recorded information on a magneto-optical optical disk, polarized laser light is focused onto the recording medium using a lens, and a small amount of the laser light is reflected back due to the Kerr effect. In order to read information by detecting the rotation of polarized light, it is necessary to use an optical disk substrate that does not easily cause birefringence even when light is incident from an oblique direction.

Furthermore, since the medium is heated with laser light during writing, optical disk substrates are required to have high heat resistance.

In view of these circumstances, the present invention achieves low birefringence even when injection molding, compression molding, etc. The object of the present invention is to provide an optical element with good dimensional stability.

(Means for Solving the Problems) The present invention provides an optical resin molded article consisting of a polymer portion mainly composed of an aromatic vinyl monomer and a polyphenylene ether portion. Melt fluidity of the main polymer portion (according to ASTM 01238)
230℃, 3.8 kg load・g/10 minutes) (MFR
) PI, the weight of the aromatic vinyl monomer unit in the polymer portion is expressed as Wo, and the intrinsic viscosity of the polyphenylene ether portion (measured and calculated using an Ubbelohde viscometer in chloroform solution at 25°C) is [η]2□ , when the weight of the polyphenylene ether part in the optical resin molded body is represented by W, □, [η) PPf is 0.3 to 0.7 and is within the range expressed by the following general formula. Characteristic optical resin moldings.

Y-2≦100・W, D,≦Y+2 The optical resin molded article of the present invention is a mixture of a polymer mainly composed of aromatic vinyl monomer units and polyphenylene ether, and a polymer portion of both. It consists of a block copolymer, a graft copolymer, or a mixture thereof.

In the present invention, the polymer mainly composed of aromatic vinyl monomer units refers to aromatic vinyl monomer homopolymers and copolymers containing 50% by weight or more of aromatic vinyl monomer units. Examples of aromatic vinyl monomers include styrene, α-methylstyrene, m-methylstyrene, ρ-methylstyrene, O-chlorostyrene, m-chlorostyrene, p-chlorostyrene, m-bromostyrene, Examples include ρ-bromostyrene, and styrene is particularly preferably used.

Examples of monomers copolymerized with aromatic vinyl monomers include unsaturated nitriles such as acrylonitrile and methacriconitrile; methacrylic acid alkyl esters such as methyl methacrylate, n-propyl methacrylate, and methacrylic acid -propyl, n-butyl methacrylate, cyclohexyl methacrylate; alkyl acrylates, such as methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, etc., as well as methacrylic acid, acrylic acid, maleic anhydride, Examples include citraconic anhydride, N-methylmaleimide, N-phenylmaleimide, and the like.

These copolymerizable weights can be used alone or in combination, but within the range that does not impede the transparency of the copolymer with the aromatic vinyl monomer and the resin material made of this and polyphenylene ether. The combination and usage ratio may be adjusted.

The amount of the aromatic vinyl monomer in the monomer mixture is preferably 50% by weight or more, and if it is less than 50% by weight, the hygroscopicity of the resulting resin increases, which is not preferable.

In addition, the melt flow rate (MFR) De3 of a polymer mainly composed of aromatic vinyl monomer units is based on AST) 101238, and the melt flow rate is g/10 minutes at 230°C and a load of 3.8 kg. represent

This value is approximately 0.5 to 200.

Preferably it is 2-100.

If it exceeds 200, it is not preferred because the mechanical strength decreases, and if it is smaller than 0.5, it becomes difficult to reduce birefringence, which is not preferred.

Methods for producing polymers mainly composed of aromatic vinyl monomer units include bulk polymerization using a radical initiator, suspension polymerization,
Either emulsion polymerization or solution polymerization may be used, but bulk polymerization or suspension polymerization is preferred from the viewpoint of productivity and obtaining a polymer with less contamination of impurities.

Examples of the radical initiator include peroxides such as lauroyl peroxide, benzoyl peroxide, di-tert-butyl peroxide, and dicumyl peroxide;
Examples include azo compounds such as -azobisisobutyronitrile and 1.1°-azobis(1-cyclohexanecarbonitrile).

In order to control the molecular weight, if necessary, tart-butyl, n-butyl, n-octyl,
N-dodecyl, tert-dodecyl mercaptan, etc. may be added.

The polymerization temperature is generally in the range of 50 to 150°C.

The polyphenylene ether referred to in the present invention is a polymer having a repeating unit represented by the general formula (wherein R1, RZ, R2, and R4 represent hydrogen, halogen, or a hydrocarbon group).

The polyphenylene ether is a polymer obtained by polymerizing phenolic monomers by oxidative coupling, and is produced by a known method using a copper-based or manganese-based catalyst (for example,
6-18692, Japanese Patent Publication No. 47-36518).

A specific example of this polyphenylene ether is poly(2,
6-dimethyl-1,4-phenylene)ether, poly
(2-methyl-6-nityl-1°4-phenylene) ether, poly(2-methyl-6-broby-1,4-phenylene) ether, poly(2,6-diprobyl-1.
4-phenylene)ether, poly(2-methyl-6-
Bromo-1,4-phenylene) ether, etc.
Especially poly (2,6-cymethyl-1,4-phenylene)
Ether is preferred.

Although polyphenylene ethers commonly used as engineering plastics can be used, polyphenylene ethers with lower molecular weights are suitable.

In other words, the average molecular weight of polyphenylene ether is the intrinsic viscosity of the polymer [η),...! (Measurement and calculation in chloroform at 25°C), 0.1 to 1.0 can be used, but 0.3 to 0.7 is preferable.

Among them, 0.3 to 0.45 is preferable, and more preferably 0.3
5 to 0.42 is preferred.

If it is less than 0.3, the mechanical strength of the optical resin molded body will be low.

Further, in order to further reduce birefringence, especially birefringence for obliquely incident light, it is preferably 0.45 or less.

This is due to the ease of orientation of the polymer mainly composed of aromatic vinyl monomers and polyphenylene ether, and/or when producing optical elements by injection molding, for example.
Alternatively, this may be due to a difference in the relaxation rate of the polymer within the mold.

In other words, by using a polyphenylene ether with a small average molecular weight, which inherently has a high melt viscosity during molding, tends to cause orientation, and tends to leave orientation, it becomes difficult for the polyphenylene ether portion in the resin to become oriented, and the relaxation rate increases. It is thought that because the process speed becomes faster, an optical resin molded article with low birefringence and low birefringence against obliquely incident light can be obtained in a wider resin composition range and under wider injection molding conditions.

Melt mixing or solution mixing is suitable for obtaining the resin material used in the optical resin molding of the present invention by mixing a polymer mainly composed of aromatic vinyl monomer units and polyphenylene ether. .

Melt mixing is carried out using an extruder, Banbury mixer, kneader blender, etc. at a temperature higher than the melting temperature of polyphenylene ether.
This is done under high shear using a mixing machine such as a heated roll.

Regarding the mixing degree, it is preferable that the repolymers are dispersed and mixed to a depth of about 1 μm or less, and further preferably to a molecular scale.

Whether the mixed state has reached the molecular scale can be easily determined based on the unique glass transition temperature of the mixture.

In order to obtain a sufficiently satisfactory mixing state, methods such as increasing the mixing temperature, extending the mixing time, and further increasing the shear force are adopted.

Furthermore, a small amount of an organic solvent may be used as a plasticizer in order to lower the melting temperature of the repolymer and facilitate mixing during melt mixing.

As the organic solvent, the organic solvent used in the solution mixing method described below can be used, and after the mixing is completed, the used organic solvent may be removed by evaporation.

Solution mixing involves dissolving the repolymer in an organic solvent and adding a small amount (both 1
After making a solution of % by weight and making a homogeneous mixture by stirring and mixing, the organic solvent is also evaporated off, or a poor solvent for the repolymer is added to the homogeneous mixture, and the mixed repolymer can be precipitated.

Suitable organic solvents include chloroform, methylene chloride, ethylene chloride, toluene, benzene, chlorobenzene, etc., and poor solvents include methanol, ethanol, propyl alcohol, n-hexane,
Examples include n-pentane.

A block copolymer or graft copolymer consisting of a polymer portion mainly composed of aromatic vinyl monomer units and a polyphenylene ether portion can be obtained by polymerizing one monomer in the presence of the other. It will be done.

Specifically, Special Publication No. 42-22069, No. 47-12
10, No. 47-47862, No. 52-38596, etc., in the presence of polyphenylene ether, monomers mainly consisting of aromatic vinyl monomers are polymerized, or aromatic A graft polymer or a block copolymer can be produced by oxidative coupling polymerization of a phenol monomer in the presence of a polymer mainly composed of vinyl monomer units.

In order to sufficiently reduce the birefringence of the optical resin molding of the present invention not only for vertically incident light but also for obliquely incident light,
It is necessary to have a composition that falls within the range applicable to the general formula.

Further, within the range of the general formula, it is desirable that the weight fraction W, □ of the polyphenylene ether portion is in the range of more than 0.4 and up to 0.7.

If it is less than 0.4, the heat resistance will not be sufficient, and if it exceeds 0.7, discoloration will become noticeable and the molding conditions will become harsh, which is not preferable.

In the present invention, the resin molded article includes, in addition to general optical disk substrates, magneto-optical disk substrates, various lenses,
A prism etc. can be mentioned.

Among the resin molded bodies, when used as an optical disc substrate, semiconductor laser light and the like pass through.

Therefore, the light transmittance at a wavelength of 800 nm is 1.2
It is preferable that it is 75% or more in the seagull material.

Injection molding, compression molding, injection compression molding, etc. may be used as molding methods for producing the optical resin molded article of the present invention. Among these molding methods, molding with a relatively large degree of birefringence caused by molding Regardless of the method, the effect of the present invention is remarkable, and injection molding is most preferred from the viewpoint of this and productivity.

The injection molding method referred to herein is a method of manufacturing a molded article by press-fitting heated resin into a fluidized state into a closed mold cavity and cooling and solidifying the resin.

Further, a vacuum suction method within the entire mold or an injection compression method for reducing the mold cavity capacity during injection molding may be used in combination.

When producing the optical resin molded article of the present invention by injection molding, the melted and plasticized resin is heated at a temperature of 270°C or higher to 35°C.
Injection molding is preferably carried out at a temperature of 0°C or lower, more preferably 300°C or higher and 340°C or lower.

The temperature of the resin here refers to the temperature of the resin in the injection cylinder, which is plasticized and melted by external heating from a heater or the like and shear heat generated by the rotation of the screw in the injection molding machine.

If the temperature of the resin is much lower than 270°C, the resulting optical disk substrate will have a birefringence of 20 nm or more, making it unsuitable as an optical disk substrate, and if the temperature of the resin exceeds 350°C,
This is unsuitable because the resin decomposes and defects such as discoloration and silver tend to occur, and the bit errors of the resulting optical disk substrate increase significantly.

In this injection molding, the mold temperature is preferably kept at 50°C or more and 140°C or less, more preferably 80°C or more and 120°C or less.

The mold temperature here refers to the surface temperature of the mold cavity immediately before injection.

If the mold temperature is less than 50℃, the transferability of the fine guide grooves (groups) cut into the mold surface will be poor;
Exceeding this is not preferable because the molded product will not be easily released from the mold.

In the injection molding of the present invention, the injection molding time is preferably within the range of 0.92 seconds or more and 3 seconds or less, more preferably 0.3 seconds or more and 2 seconds or less.

The injection molding time here is the time for filling the resin into the mold cavity.

If the injection molding time is less than 0.2 seconds, silver will occur and bit errors will increase significantly when used as an optical disk, and if the injection molding time exceeds 3 seconds, the birefringence of the resulting optical disk substrate will be 2.
Since it becomes 0 nm or more, it is not preferable.

<Examples> The present invention will be explained in detail below using examples, but the present invention is not limited to the following.

Note that all parts and percentages in the examples are based on weight.

Further, the physical properties shown in the examples were measured by the following method.

- Birefringence: Retardation was measured by the Senarmont compensator method at 546 nm using a polarizing microscope.

- Water absorption rate: Equilibrium water absorption rate in distilled water at 60°C was measured based on ASTM D-570.

- Light transmittance: The transmittance of a sample thickness of 1.2 ms at 800 nm was measured using a self-recording spectrophotometer (model 330 manufactured by Hitachi, Ltd.).

- Bending physical properties: Measured based on ASTM D-790.

・Heat resistance: 5m x 5 cranes x 3. The glass transition temperature was measured using the linear expansion coefficient method using the test piece.

- Intrinsic viscosity of polymer: Measured and calculated using an Ubbelohde viscometer in a chloroform solvent at 25°C.

・Melt flow rate): Based on AST-〇1238,
Measurement was performed at 230°C and a load of 3.8 kg.

- Kneading and pelletizing were performed using a two-wheel extruder (manufactured by Nippon Steel Corporation, model TEX30-30tV-2V).

・The injection molding machine is Sumitomo Heavy Industries Seimura Muff) 15
0/75 (75) n) type, and the mold has a molded object diameter of 12
A disk mold with a thickness of 0 m and a thickness of 1.2 fi was used.

Example 1. Comparative Examples 1 to 3 2.6-xylenol was polymerized using manganese chloride and ethanolamine as catalysts according to the method described in Example 2, No. 9 of Japanese Patent Publication No. 47-36518, and the intrinsic viscosity was 0.4.
Poly(2,6-dimethyl-1,4-phenylene)ether was prepared at 0 (25° C. in chloroform).

This polyphenylene ether and polystyrene resin (Nisblai 1-88-62°MFR15 manufactured by Sumitomo Chemical Co., Ltd.) were mixed and blended in the proportions shown in Table 1, kneaded and granulated in an extruder, and then heated at a cylinder temperature of 320°C. Mold temperature 105℃
A disc having a diameter of 120 fi and a thickness of 1.2 u was obtained by injection molding.

The physical property evaluation results are also shown in Table 1.

Note that the birefringence was measured at a position 35 points from the center of the disk.

Table 1 Examples 2-5. Comparative Examples 4 to 8 Poly(2,6-cymethyl-1.4
-phenylene) ether and polystyrene (manufactured by Sumitomo Chemical Co., Ltd., Nisbright 4-62A MFR24)
The resin was kneaded and pelletized at a resin temperature of 320°C,
An optical disk substrate was manufactured by injection molding under conditions of a mold temperature of 100° C. and an injection time of 1 second.

Table 2 shows the birefringence of the obtained optical disk substrate with respect to vertically incident light and 30° obliquely incident light.

Note that the measurement position is indicated by the distance in the radial direction from the center of the optical disk substrate.

Table 2 shows the bending properties and heat resistance of the plates obtained by press-molding the pelletized resin at 270°C.

Comparative Example 9 Injection molding was performed using the poly(2,6-dimethyl=1,4-phenylene) ether used in Example 1 alone.

Molding could not be performed under the same conditions as Example 1, and the cylinder temperature was 3.
Molding was carried out at 50°C and mold temperature of 130°C.

The absolute value of birefringence was 1100n or more, which was extremely large.

Comparative Example 10 Molding was performed using the polystyrene resin used in Example 1 alone under the same conditions as in Example 1.

The absolute value of birefringence was 1100n or more, and the distribution was highly uneven.

Comparative Example 11 Using bisphenol A as a raw material, interfacial polycondensation was carried out by blowing phosgene into the resin using methylene chloride as a solvent according to a conventional method to obtain a polycarbonate resin having an average molecular weight of about 15,000.

Note that t-butylphenol was used to adjust the molecular weight.

The obtained powdered resin was granulated using an extruder, and injection molding was performed under the same conditions as in Example 1.

However, the birefringence of the disk was as large as +1100n or more.

Furthermore, molding was carried out at a cylinder temperature of 340°C.

The birefringence of the disk is as large as 1100n, and the water absorption is 0.45.
%Met.

Moreover, the glass transition temperature was 136°C.

In addition, we tried molding at a higher molding temperature, but the result was 340
When the temperature exceeds ℃, the resin undergoes thermal decomposition, making molding difficult.

<Effects of the Invention> The optical resin molded article of the present invention uses polystyrene resin as one of the raw materials, which has conventionally been unusable due to its high birefringence, although it has low moisture absorption and good dimensional stability. Not only is it applicable, but it also provides a good balance of heat resistance and mechanical strength.

In particular, by using the identified polyphenylene ether with a relatively low intrinsic viscosity, it has low birefringence, and also has a wide composition with low birefringence for incident light from an oblique direction, which has not been seen before. Since it can be removed, it is also possible to have high heat resistance.

Furthermore, the optical resin molded article of the present invention has the advantage that it can be molded with low birefringence even by injection molding, which is said to be prone to producing birefringence.

The optical resin molded article of the present invention includes a substrate for an optical disc,
They are lenses, prisms, etc., and are particularly suitable for using light with a specified wavelength.

Furthermore, as mentioned above, it has low birefringence for obliquely incident light and high heat resistance, so it is used not only for general optical disk substrates but also for magneto-optical disk substrates.

Claims (1)

[Claims] (1) A polymer portion mainly composed of an aromatic vinyl monomer,
In an optical resin molded article consisting of a polyphenylene ether part, the melt fluidity of the polymer part mainly composed of an aromatic vinyl monomer (according to ASTM01238/230
°C, 3.8 kg load・g/10 minutes) [MFR]_P_
3. The weight fraction of the aromatic vinyl monomer unit in the polymer portion is expressed as W_P_3, and the intrinsic viscosity of the polyphenylene ether portion (measured and calculated using an Ubbelohde viscometer in chloroform solution at 25°C) is [η]_P_P_E , when the weight fraction of the polyphenylene ether part in the optical resin molded body is expressed as W_P_P_E, [η]_P_P_E is 0.
．． 3 to 0.7 and within the range represented by the following general formula. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [η]・10 Y−2≦100・W_P_P_E≦Y+2