JP3048183B2 - Low birefringence methacrylic resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low birefringence methacrylic resin composition, and more particularly to a methacrylic resin excellent in low birefringence suitable for optical information recording carriers and optical elements such as optical lenses. Composition.

[0002]

2. Description of the Related Art Conventionally, glass has been widely used as an optical material such as a lens in terms of accuracy and reliability, and plastics have been in the field for many years. Nevertheless, there is no plastic alternative to glass. However, with the development of society and industry in recent years, the required quality of optical elements has been diversified, and fields where glass quality and performance are not necessarily required, or fields where plastic has many advantages such as weight reduction, mass production, asphericity etc. In addition, the use of plastics is rapidly expanding, and the use of plastics in cameras, copiers, optical lenses of laser optical equipment, optical information recording disks, and the like is remarkable.

However, plastics used as optical materials have many problems to be improved such as heat resistance, hygroscopicity, and optical properties such as refractive index, dispersion, and birefringence. . For example, polycarbonate resin has a problem that chromatic aberration is large because of large dispersion as an optical lens, and a recording optical disc material has a drawback such as a large birefringence due to its molecular structure. The range of use is limited. on the other hand,
The methacrylic resin has a problem of high hygroscopicity and low heat resistance, but has properties most necessary for an optical lens such as low dispersion and low birefringence, and an optical disk. Therefore in recent years,
Many proposals have been made regarding improvement of hygroscopicity and heat resistance while maintaining the optical properties of methacrylic resin. For example, as a method of improving the hygroscopicity, a method of copolymerizing methyl methacrylate and styrene (JP-A-57-33)
446), a method of copolymerizing methyl methacrylate and cyclohexyl methacrylate (JP-A-57-1862).
No. 41), a method of copolymerizing methyl methacrylate and cyclodecyl methacrylate (JP-A-61-159408).
JP-A-64-1749), a method of blending a copolymer of methyl methacrylate and cycloalkyl methacrylate with a polycarbonate (JP-A-64-1749), and a method of mixing a copolymer of methyl methacrylate and styrene with an acrylic resin (Japanese Unexamined Patent Publication (Kokai) No. 2-115251), and a method of blending an aromatic polycarbonate and modified polystyrene (Japanese Unexamined Patent Publication (Kokai) No. 61-19630) as a method for reducing birefringence.

[0004]

However, although the proposed method has a certain effect of improving the hygroscopicity, the improvement in the hygroscopicity is limited due to a large decrease in mechanical strength. There are problems such as an increase in birefringence and a decrease in transparency due to the generated molecular orientation. Therefore, it is a fact that a satisfactory material has not been obtained as an optical element material such as an optical information recording carrier.

Accordingly, an object of the present invention is to provide a methacrylic resin composition having excellent low birefringence and good transparency, heat resistance and mechanical strength.

[0006]

Means for Solving the Problems In order to achieve the above object, the present inventors have conducted intensive studies focusing on a specific methacrylate ester. As a result, a copolymer comprising methyl methacrylate and a specific methacrylate ester was obtained. And, a resin composition in which a copolymer of methyl methacrylate and an aromatic vinyl monomer, and an aromatic polycarbonate resin are blended at a specific ratio, has excellent low birefringence, and transparency, which is a characteristic of methacrylic resin, The inventors have found that they have maintained the mechanical strength, and have completed the present invention.

That is, the gist of the present invention is that 50 to 90% by weight of methyl methacrylate is represented by the following general formula (I):

Embedded image (Wherein R represents a hydrogen atom or a halogen atom, and n is an integer of 1 to 5), and 10 to 50% by weight of a methacrylic acid ester represented by the following formula: 60-98.
A copolymer (B) comprising 9 parts by weight, 10 to 90% by weight of methyl methacrylate, 90 to 10% by weight of an aromatic vinyl monomer and 0 to 20% by weight of another copolymerizable vinyl monomer; 0.6 to 30 parts by weight, and 0.5 to 10 parts by weight of the aromatic polycarbonate resin (C), and the ratio of the copolymer (B) to the aromatic polycarbonate resin (C) is
A low birefringence methacrylic resin composition satisfying 1.2 ≦ (B) / (C) ≦ 3.0, and an optical element comprising the resin composition. Hereinafter, the present invention will be described in detail.

[0008] Methyl methacrylate constituting the copolymer (A) used in the present invention is another methacrylic resin in order to maintain excellent optical properties and balanced mechanical strength, which are characteristics of methacrylic resin. Dominant over monomer , ie 50
It is necessary to use 90% by weight, the good Mashiku 60-85
% By weight. If the amount used is less than 50% by weight, the above characteristics are not maintained, while if it exceeds 90% by weight,
It is not preferable because there are problems such as no improvement in the hygroscopicity and an increase in haze due to low compatibility with the copolymer (B).

The methacrylic acid ester represented by the general formula (I) as another component constituting the copolymer (A) of the present invention includes, for example, phenyl methacrylate, bromophenyl methacrylate, dibromophenyl methacrylate And 2,4,6-tribromophenyl methacrylate, monochlorophenyl methacrylate, dichlorophenyl methacrylate, and trichlorophenyl methacrylate. These can be used alone or in combination of two or more. Among these methacrylic acid esters, the general formula (II)

[0010]

Embedded image (Wherein, X represents a halogen atom, and n is an integer of 1 to 5), and is preferably a methacrylic acid ester having a halogenated aromatic hydrocarbon group represented by the following formula:
4,6-Tribromophenyl is particularly preferred. General formula
The methacrylate represented by (I) is used mainly for the purpose of improving low hygroscopicity and improving the compatibility between the copolymer (B) and the polycarbonate.
Must be a 50% by weight, the good Mashiku 15
４０40% by weight. If the addition amount is less than 10% by weight, the effect of improving the low hygroscopicity is low, and the compatibility between the copolymer (B) used in the present invention and the polycarbonate is insufficient, and the haze tends to increase, which is not preferable. On the other hand, if it exceeds 50% by weight, problems such as a decrease in mechanical properties and a decrease in transparency may occur, which is not preferable.

The copolymer (A) may optionally contain other vinyl monomers copolymerizable with the methyl methacrylate and the methacrylate represented by the general formula (I) in order to improve moldability and the like. A monomer can be a component thereof. Other copolymerizable vinyl monomers include acrylates such as methyl acrylate, ethyl acrylate, butyl acrylate, octyl acrylate, cyclodecyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, and naphthyl methacrylate. , Methacrylates such as benzyl methacrylate, styrene, aromatic vinyl monomers such as vinyltoluene, acrylonitrile, nitrile compounds such as methacrylonitrile, cyclohexylmaleimide, N-substituted maleimide compounds such as o-chlorophenylmaleimide and the like. Can be These vinyl monomers can be used alone or in combination of two or more, and the addition amount thereof is 0 to 20% by weight, preferably 1 to 10% by weight.
It is. If the amount exceeds 20% by weight, heat resistance and mechanical properties tend to decrease, which is not preferable.

The methyl methacrylate constituting the copolymer (B) used in the present invention is compatible with the copolymer (A),
It is a component for maintaining transparency, and its addition amount is 10 to
90% by weight, preferably 20 to
80% by weight. If the amount is less than 10% by weight or more than 90% by weight, the compatibility with the copolymer (A) is reduced, and transparency cannot be obtained. The aromatic vinyl monomer which is another component used in the copolymer (B) of the present invention, styrene, vinyl toluene, alpha-methyl styrene and the like, good Mashiku is styrene. It is necessary that the added amount be 10 to 90% by weight, preferably 20 to 80% by weight. If the addition amount is less than 10% by weight or more than 90% by weight, the compatibility may be lowered and transparency may not be obtained, which is not preferred. For the copolymer (B), other vinyl monomers copolymerizable with methyl methacrylate and the aromatic vinyl monomer can be used as necessary as constituents thereof. Other copolymerizable vinyl monomers include acrylates such as methyl acrylate, ethyl acrylate, and butyl acrylate, and methacrylates such as ethyl methacrylate and butyl methacrylate (excluding methyl methacrylate) ),
Examples thereof include nitrile compounds such as acrylonitonyl and methacrylonitrile, and N-substituted maleimide compounds such as cyclohexylmaleimide and O-chlorophenylmaleimide. The amount of these vinyl monomers added is 0 to 20% by weight.
And preferably 1 to 10% by weight. When the amount of the vinyl monomer exceeds 20% by weight,
It is not preferable because defects such as reduced heat resistance and reduced transparency tend to occur.

The aromatic polycarbonate (C) of the present invention
Is used together with the copolymer (B) for the purpose of improving low birefringence and decreasing moisture absorption. As the aromatic polycarbonate used in the present invention, for example, bis- (4-hydroxyphenyl) methane polycarbonate, 1,1-
Bis- (4'-hydroxyphenyl) propane polycarbonate, 2,2-bis- (4'-hydroxyphenyl) propane polycarbonate, 2,2-bis- (4 '
-Hydroxyphenyl) butane polycarbonate, 2,
2-bis- (4'-hydroxy-3 ', 5'-dimethylphenyl) propane polycarbonate, 2,2-bis-
(4'-hydroxy-3'-methylphenyl) polycarbonate and the like, and particularly preferred is bisphenol A polycarbonate.

Each of the above copolymer (A), copolymer (B) and aromatic polycarbonate (C) has a molecular weight
Although there is no particular limitation, it is preferable that the intrinsic viscosity in chloroform at 20 ° C. is in the range of 0.3 to 1.3 dl / gr. When the intrinsic viscosity is less than 0.3, the mechanical strength tends to decrease, which is not preferable.
When the ratio exceeds 1.3, the transparency tends to decrease due to insufficient melting of the resin and the like, which is not preferable.

The method for producing the copolymers (A) and (B) is as follows:
Generally known polymerization methods, such as suspension polymerization method,
It is performed by a bulk polymerization method, a solution polymerization method, or the like, and any method may be used. The polymerization temperature is 50 commonly used.
It can be polymerized at up to 160 ° C. Also, upon polymerization,
Examples of commonly used polymerization initiators include, for example, 2,2'-
Azobisisobutyronitrile, 2,2'-azobis-
Azo compounds such as 2,4-dimethylvaleronitrile, lauroyl peroxide, tert. Organic peroxides such as -butylperoxy-2-ethylhexanoate, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate and benzoyl peroxide; and n-butylmercaptan as a chain transfer agent , N-octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan and the like can be used.

The method for producing the aromatic polycarbonate includes a generally known interface method, a pyridine method and a melting method, and any method may be used. Generally commercially available polycarbonates can also be used.

The low birefringence resin composition of the present invention comprises 60 to 98.9 parts by weight of the copolymer (A) and 0.1 to 10 parts by weight of the copolymer (B).
6 to 30 parts by weight, and aromatic polycarbonate (C) 0.1.
5 to 10 parts by weight, and the blend ratio of the copolymer (B) and the polycarbonate (C) is represented by the following formula (a):
Preferably, it is necessary to satisfy (b). 1.2 ≦ B / C ≦ 3.0 (a) 1.4 ≦ B / C ≦ 2.5 (b) (where B is the blending amount of the copolymer (B), and C is the aromatic polycarbonate ( The amount of C) is shown.)

When the ratio of B / C is less than 1.2 or more than 3.0, the effect of reducing birefringence is hardly observed.
Not preferred. The compounding amount of the aromatic polycarbonate (C) is 0.5 to 10 parts by weight, more preferably 2 to 10 parts by weight.
８8 parts by weight. When the amount of the aromatic polycarbonate (C) is less than 0.5 part by weight, there is no effect of reducing birefringence. On the other hand, when the amount is more than 10 parts by weight, haze increases and transparency decreases, which is not preferable. .

As a method for producing such a resin composition, the copolymers (A) and (B) and the aromatic polycarbonate (C) in the above mixing ratio are usually used such as Brabender, Henschel mixer, compactor and tumbler. They can be mixed with a mixer, or they can be kneaded with an extruder to form pellets or sheets.Using these mixtures or pellets, they can be formed with molding machines such as injection molding machines or compression molding machines. There can be mentioned a method of molding to obtain a molded product, and there is no particular limitation.

In carrying out the present invention, additives such as an ultraviolet absorber, a heat stabilizer, an antioxidant, a lubricant, a release agent, and a face wash can be added as needed, and polymerization, mixing, and melt mixing can be performed. Any of the steps may be used.

[0021]

EXAMPLES The present invention will now be described specifically with reference to examples, but the present invention is not limited to these examples. The evaluation methods in the examples are as follows (1) to (5).
Was carried out in the manner described above. (1) Total light transmittance and haze (%) After molding a disk substrate of 120φ × 1.2t (mm) with an injection molding machine M-100DM (manufactured by Meiki Seisakusho), this is conformed to the method of ASTM D1003. Measured. (2) Birefringence Using a disk substrate of 120φ × 1.2t (mm), the optical path difference (nm) at a point 10 mm from the gate was measured using a polarizing microscope L.
It was measured by ABOPHOT-POL type (manufactured by Nippon Kogaku Kogyo Co., Ltd.). (3) Intrinsic viscosity (dl / gr) After dissolving a resin at a certain concentration in chloroform, it was measured at 20 ° C. with an automatic viscometer. (4) using a tensile strength (Kg / cm ²⁾ Dan Bell molds according to ASTM D638, and molded by an injection molding machine J75SAV (manufactured by Japan Steel Works), AS
It was measured by the method of TM D638. (5) Moisture absorption (%) Using a disk mold of 50.8φ × 3.2t (mm), molding with an injection molding machine J75SAV (manufactured by Nippon Steel Works), a thermo-hygrostat (Tabayespec PL-2 type) ) 60 ° C, 90% R
The saturated moisture absorption under the condition of H was measured.

Embodiment 1 1. Production of copolymer (A) 70% by weight of methyl methacrylate, 5% by weight of methyl acrylate, 2,4,6-tribromophenyl methacrylate 2
15 kg of a monomer mixture obtained by dissolving 0.2 parts by weight of lauroyl peroxide, 0.2 parts by weight of n-octyl mercaptan, and 0.1 parts by weight of stearyl alcohol in 100 parts by weight of a 5% by weight monomer mixture; 300 kg of a 1 wt% aqueous solution of potassium methacrylate, 7 gr of sodium dihydrogen phosphate and 30 kg of pure water in which 22 gr of disodium hydrogen phosphate were previously dissolved were charged into a 50-liter pressure-resistant reaction vessel equipped with a stirrer. Then, the reactor was purged with nitrogen, polymerized at 80 ° C., and after an exothermic peak, further heated at 120 ° C.
Polymerized for 1 hour. After cooling, a beaded copolymer was obtained through the steps of washing, dehydration and drying. The intrinsic viscosity of the beads was 0.75 dl / gr.

2. Production of copolymer (B) 100 parts by weight of a mixture of 30% by weight of methyl methacrylate and 70% by weight of styrene were added to 0.4 part of lauroyl peroxide.
15 parts by weight of a monomer mixture in which 0.15 parts by weight of n-octyl mercaptan and 0.1 part by weight of stearyl alcohol are dissolved, and 1.0% by weight of potassium polymethacrylate
Aqueous solution 450 gr, sodium dihydrogen phosphate 14 gr,
30 kg of pure water in which 40 gr of sodium hydrogen phosphate was previously dissolved was charged into a 50-liter pressure-resistant polymerization tank equipped with a stirrer. Next, the reaction vessel was purged with nitrogen,
After the exothermic peak, polymerization was further performed at 120 ° C. for 1 hour. After cooling, a beaded copolymer was obtained through washing, dehydration and drying steps. The intrinsic viscosity of the beads is 0.
It was 87 dl / gr.

3. Blend and evaluation 87% by weight of copolymer (A) obtained as described above
8.0% by weight of copolymer (B) and Panlite L-1250 (intrinsic viscosity 0.3 as polycarbonate (C))
(70 dl / g) was mixed in a Henschel mixer and pelletized with an extruder having a cylinder diameter of 40 mm (B / C of the pellets was 1.60). The pellet was injection molded to obtain a test piece. Using the obtained test piece, the total light transmittance, haze, optical path difference, tensile strength, and moisture absorption rate were measured.
2.2%, haze 0.1%, optical path difference 0.0 nm, tensile strength 620 kg / cm ² , exhibiting physical properties of a moisture absorption of 0.85%, a transparent low moisture absorption low birefringence resin composition. You can see that there is.

Comparative Example 1 87% by weight of the copolymer (A) of Example 1 and the copolymer (B)
10.4% by weight and 2.6% by weight of Panlite (L-1250) were blended and pelletized under the same conditions as in Example 1 (B / C of the pellets was 4.0). As a result of evaluating the pellets in the same manner as in Example 1, the total light transmittance was 81.6%, the haze was 11.0%, and the transparency was very low.
In addition, the birefringence was high and it was not suitable for an optical material.

Comparative Example 2 55% by weight of the copolymer (A) of Example 1 and the copolymer (B)
30% by weight and 15% by weight of Panlite (L-1250) were blended in the same manner as in Example 1 to obtain pellets (B / C of the pellets was 2.0). As a result of evaluating the pellets in the same manner as in Example 1, the total light transmittance was 65.0.
% And haze of 38.0%, there was almost no transparency.

Examples 2 to 7 Except that the types and amounts of the chain transfer agent and the polymerization initiator were changed so that the compositions shown in Tables 1 and 2 had the intrinsic viscosities shown in Tables 1 and 2, respectively. After polymerization under the same conditions as in Example 1,
In the same manner as in Example 1, a copolymer (A) and a copolymer (B) were obtained. The copolymer (A), the copolymer (B) and the polycarbonate (C) were mixed at the ratios shown in Table 3 and pelletized, and evaluated according to a predetermined evaluation method. The results are shown in Examples 2 to 5 of Table 3, wherein the ratio of the copolymer (B) to the aromatic polycarbonate (C) is within the scope of the claims, and the ratio of the polycarbonate in the resin composition is 0.5 ~
It can be seen that when the content is 10% by weight, a low birefringence resin composition excellent in transparency and low moisture absorption can be obtained. The tensile strength of these resin compositions was good at 400 kg / cm ² or more. Further, as shown in Example 6, even when an aromatic polycarbonate having a high intrinsic viscosity was used, a birefringence reduction effect was obtained, and a transparent and low-hygroscopic resin composition was obtained.

[0028]

[Table 1]

[0029]

[Table 2] Abbreviations of the monomers in the table are as follows. TBPMA: 2,4,6-tribromophenyl methacrylate MBPMA: monobromophenyl methacrylate PhMA: phenyl methacrylate CHMA: cyclohexyl methacrylate BzMA: benzyl methacrylate EMA: ethyl methacrylate MA: methyl acrylate EA: ethyl acrylate ST: Styrene MST: Methylstyrene AN: Acrylonitrile

[0030]

[Table 3] The abbreviations of the polycarbonates in the table are as follows. PL: Panlite L-1250 (Teijin Kasei) UP: Iupilon H-4000 (Mitsubishi Gas Chemical Industry Co., Ltd.) NV: NOVAREX 7020AD3 (Mitsubishi Kasei Co., Ltd.) TF: Toughlon 12500 (Idemitsu Petrochemical Co., Ltd.) )

Comparative Examples 3 to 6 As in Comparative Examples 3 and 4 shown in Table 4, when the compositions of the copolymer (A) and the copolymer (B) are outside the scope of the claims, the blend ratio Is within the range, transparency cannot be obtained or birefringence increases.

As shown in Comparative Examples 5 and 6, the copolymer (B)
Alternatively, when the aromatic polycarbonate (C) is not added, transparency is insufficient, or birefringence is high, and a resin having sufficient performance cannot be obtained.

[0033]

[Table 4] Example 8 Using the same resin as in Example 1, an injection molding machine M-250 was used.
A DM (manufactured by Meiki Seisakusho) was mounted with a disk die having a diameter of 300 φ (mm) equipped with a nickel stamper having a groove width of 0.8 μm, a groove depth of 0.07 μm, and a pitch between grooves of 1.6 μm, and a cylinder temperature of 260 ° C. The disc was injection molded under the conditions of a mold temperature of 60 ° C. and a cooling time of 20 seconds. 60 mm from the center of the obtained disc, 100 mm
As a result of measuring the birefringence at each point of mm and 140 mm, they were 2.5 nm, 0 nm, and 0 nm, respectively, and showed good low birefringence.

[0034]

As described above, the methacrylic resin composition of the present invention has excellent transparency, moldability, and well-balanced mechanical properties, which are the characteristics of methacrylic resin. It is characterized in that the hygroscopicity, which is a drawback, is greatly improved and excellent low birefringence can be obtained.

For this reason, this resin composition is suitably used for an optical element, in particular, an optical lens of a camera, a copying machine, a laser optical apparatus or the like, or an optical information recording carrier.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification code FI C08L 69:00) (56) References JP-A-64-1749 (JP, A) JP-A-63-295662 (JP, A) JP-A-3-153715 (JP, A) JP-A-2-113455 (JP, A) JP-A-61-19656 (JP, A) JP-A-56-28233 (JP, A) (58) (Int.Cl. ⁷ , DB name) C08L 33/00-33/26 C08L 25/00-25/18 C08L 69/00

Claims (4)

(57) [Claims] 1. 50 to 90% by weight of methyl methacrylate,
The following general formula (I) (Wherein R represents a hydrogen atom or a halogen atom, and n is an integer of 1 to 5), and 10 to 50% by weight of a methacrylic acid ester represented by the following formula: 60-98.
A copolymer (B) comprising 9 parts by weight, 10 to 90% by weight of methyl methacrylate, 10 to 90% by weight of an aromatic vinyl monomer and 0 to 20% by weight of another copolymerizable vinyl monomer; A low birefringent methacrylic resin composition comprising 6 to 30 parts by weight and 0.5 to 10 parts by weight of an aromatic polycarbonate (C), and satisfying the following formula (a). 1.2 ≦ B / C ≦ 3.0 (a) (where B represents the blending amount of the copolymer (B), and C represents the blending amount of the aromatic polycarbonate (C).) 2. The resin composition according to claim 1, wherein the methacrylate represented by the general formula (I) is 2,4,6-tribromophenyl methacrylate. 3. The resin composition according to claim 1, wherein the aromatic vinyl monomer is styrene. 4. An optical element comprising the resin composition according to claim 1.