JP2778916B2 - Optical element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical element.
More specifically, the present invention relates to a method for preparing methyl methacrylate, N
-Aryl maleimides and aromatic vinyl compounds
Meta, excellent in transparency and heat resistance
The present invention relates to an optical element made of a cryl copolymer resin. [0002] 2. Description of the Related Art A meth based on methyl methacrylate
Krill resin has excellent optical properties and weather resistance.
Odor, mechanical properties, thermal properties, moldability, etc.
However, it has relatively balanced performance,
Signs, lighting covers, nameplates, automatic
Car parts, electrical equipment parts, decorative or miscellaneous goods, etc.
Is widely used in the field of
ing. However, on the one hand, the heat deformation temperature is 100 ° C.
Later, because of insufficient heat resistance, the application development is restricted
In some areas, there is a need to improve heat resistance.
There are strong demands. Improved heat resistance of methacrylic resin
Many suggestions have already been made on how to improve
You. For example, methyl methacrylate and α-methylstyrene
Methacrylate, α-meth
Method for copolymerizing styrene and maleic anhydride
(Japanese Patent Publication No. 49-10156), methyl methacrylate
G, α-methylstyrene and maleimide are copolymerized
Method, in the presence of a cross-linked polymer using a polyfunctional monomer
Method for copolymerizing methyl methacrylate, methyl methacrylate
Method for copolymerizing acrylate and methacrylic acid, methyl
Methacrylate, α-methylstyrene and acrylonitrile
A method of copolymerizing tolyl has been proposed. Only
However, the method proposed above improves heat resistance to some extent
However, productivity is extremely low due to the extremely low polymerization rate.
Low mechanical properties, weather resistance and optical properties
And the molded product is markedly colored or the molding area
Is too small for practical use due to poor molding processability.
At present, there are many problems. Further, methyl methacrylate and N-ary
A method of copolymerizing lumaleimide (JP-B-43-975)
No. 3) has also been proposed, but can be obtained by this method.
The resin has excellent mechanical properties inherent to methacrylic resin
The quality and weather resistance are impaired, and the copolymerizability of the monomers is different.
Therefore, the amount of residual monomer is large, so the moldability is poor and the appearance is
Only damaged and colored products are obtained. Furthermore, the polymerization method
Depending on the method, mistiness is remarkable and methacrylic resin is originally
Transparency is impaired. [0005] After all, any of the conventionally proposed methods is practical.
Poor performance, especially for optical applications
It has not been reached yet. [0006] SUMMARY OF THE INVENTION The object of the present invention is to
Excellent optical properties comparable to methyl methacrylate resin
With properties, mechanical properties, weather resistance and moldability
Not only have excellent heat resistance and productivity,
To provide an optical element made of a ril-based co-resin
You. [0007] An optical element according to the present invention.
Is the following equation (1) [0008] Embedded imageThe methyl methacrylate unit 98
~ 60% by weight, the following formula (2) [0010] Embedded image (Where R₁, R_Two, R_ThreeIs hydrogen or ha
Indicate Logen. N-arylmaleimide represented by
1 to 30% by weight, and styrene, vinyltoluene,
And at least one selected from the group consisting of α-methylstyrene
From 1 to 10% by weight of one kind of aromatic vinyl compound unit
A mole of N-arylmaleimide
The ratio β / α between the number α and the molar number β of the aromatic vinyl monomer is
In the range of 0.2-5, measured in chloroform at 25 ° C
The intrinsic viscosity is 0.3-1.0 dl / g,Copolymer
100% by weightIn the copolymerResidual N-allyluma
When the amount of reimide is 0.3% by weight or less andThe total amount of remaining monomers is
It is characterized by being made of a heat-resistant resin of 1.5% by weight or less.
And The heat-resistant resin used in the present invention is methyl
98-60% by weight of methacrylate, N-arylmale
1 to 30% by weight of amide and aromatic vinyl compound 1 to 10
% Of a monomer mixture consisting of the following components (B) and (C):
Suspension polymerization in the presence of the component and, if desired, component (A)
It can be manufactured by performing. (A) (a) an catalyst having an alkyl group having 1 to 12 carbon atoms;
Alkyl acrylate and / or methacrylic acid
0 to 60% by weight of acrylic acid and / or
Lithium, sodium, potassium and methacrylic acid
Acrylic acid selected from the group consisting of ammonium salts and
And / or methacrylic acid salt (II) 100 to 40% by weight
A water-soluble polymer obtained by polymerizing (B) (a) an catalyst having an alkyl group having 1 to 12 carbon atoms;
Alkyl acrylate and / or methacrylic acid
Lukyl ester (I) 0-60% by weight and (b) acrylic
Acid and / or methacrylic acid lithium, sodium
Selected from the group consisting of potassium, potassium and ammonium salts
At least one acrylic acid and / or methacrylate
0 to 20% by weight of a salt of lylic acid (II) and (c) a general formula [0013] Embedded image An acrylic acid derivative or
Polymerization of acrylic acid derivative (III) with 100 to 20% by weight
A water-soluble polymer obtained by (C) An electrolyte having a monovalent cation. In the heat-resistant resin used in the present invention, methacrylic
To maintain excellent mechanical properties and weather resistance of resin
The amount of methyl methacrylate units in the copolymer is N-A
Must be in priority amount to reel maleimide unit amount
It is. Further, N-arylmaleimide is mixed with a monomer.
Consider stabilizing polymerization by dissolving in the compound
Of methyl methacrylate and aromatic vinyl compound
The total amount should be at least about twice the amount of N-arylmaleimide.
It is. Methyl methacrylate is based on methacrylic resin
To develop conventional optical, weather resistance or mechanical properties
Necessary in the resin, contained in the resin in the range of 60 to 98% by weight.
Need to be owned. If less than 60% by weight, weather resistance
Properties and optical properties are easily impaired, and 98% by weight
If it exceeds, substantial improvement in heat resistance cannot be expected. N-arylmaleimide has improved heat resistance.
Essential component, the content in the resin is 1 to 30% by weight
And more preferably in the range of 5 to 25% by weight.
is there. If the amount is less than 1% by weight, the improvement of heat resistance is insufficient, and 30%
If the content exceeds% by weight, the mechanical strength is greatly reduced. resin
The aromatic vinyl compound is mainly N-arylmale.
A component for enhancing copolymerizability with imide,
Is in the range of 1 to 10% by weight. Less than 1% by weight
In this case, it is difficult to obtain the effect of improving the copolymerizability,
If the amount exceeds%, the optical properties as a methacrylic resin and
Mechanical properties are easily impaired. The purpose of the present invention is impaired.
Unless otherwise specified, a small proportion of monomers copolymerizable with the above monomers
Can be used for copolymerization. The heat-resistant resin used in the present invention is a molding material
At 25 ° C to obtain the desired fluidity
Value in the range of 0.3 to 1 dl / g.
Must be in the range of 0.35 to 0.8 dl / g
A range is preferred. In particular, appearance with little distortion for optical applications
0.35 to 0.60 dl / g to obtain a good injection molded product
Is optimal, and when extruding,
It is desirable that it is in the range of 0.60 to 0.80 dl / g.
No. The heat-resistant resin used in the present invention has little coloring.
In order to have an excellent appearance, the copolymer
It is necessary that the residual monomer is 1.5% by weight or less.
And preferably not more than 1.0% by weight. More details
For example, for residual N-arylmaleimide,
It is easy to cause color.
desirable. More preferably, it is at most 0.2% by weight.
Residual methyl methacrylate and aromatic vinyl compounds
The main source that impairs the appearance due to volatilization during heating such as rubber and foam
1.2% by weight or less, preferably 0.9% by weight
Do the following. The N-arylmaleimide used is
This is represented by equation (4). [0020] Embedded image (Where R₁, R_TwoAnd R_ThreeIs hydrogen or
Shows halogen. ) Chlorine is a halogen-substituted product because of its easy availability.
And bromo substitutions are recommended. Such N-arylmers
Examples of the reimide monomer include N- (2-chlorophenyl).
L) Maleimide, N- (2-bromophenyl) maleimi
N- (4-chlorophenyl) maleimide, N-
(2,4,6-trichlorophenyl) maleimide and the like
I can do it. Aromatic vinyl compound and N-arylmale
To obtain better synergistic effect of heat resistance improvement by mid
Represents the number of moles of N-arylmaleimide in the copolymer.
α, when the total number of moles of the aromatic vinyl compound is β,
β / α needs to be adjusted in the range of 0.2 to 5
It is. If β / α is less than 0.2, constraints on manufacturing conditions
And the productivity tends to decrease. On the other hand, β / α
Is more than 5, coloring tends to occur, and
Decrease in physical properties such as transparency as tacryl resin
Can be Β / α range where a more favorable synergistic effect is obtained
Is in the range of 0.5 to 2. As aromatic vinyl compounds, productivity and
Styrene and vinyltoluene from the viewpoint of balance
And a small number selected from the group consisting of α-methylstyrene
At least one kind is used. In particular, α-methylstyrene
Is used when it is desired to further improve heat resistance.
And vinyltoluene are used to improve productivity
This is useful for industrial production. Methyl methacrylate and N-aryl
A copolymer comprising maleimide is disclosed in JP-B-43-9753.
In principle, lumps and solution emulsification are also
Alternatively, it can be produced by suspension polymerization. But
In particular, comparable to polymethyl methacrylate resin,
High productivity and stable resin with excellent optical properties
It is desirable to manufacture by suspension polymerization
New In bulk polymerization, special reactor and devolatilizer are required
And the control of the reaction is complicated. Solution polymerization is called bulk polymerization
It has the same disadvantages and productivity is lower than bulk polymerization.
You. Monomer mixture or partial polymerization mixture in opposite cells
The sheet polymerization method in which the compound is injected and polymerized is also a kind of bulk weight
Although it is a combination method, productivity is low and
In order to use it, grinding and reshaping processes are required,
It is. Emulsion and suspension polymerization are carried out on the equipment side and on the polymerization strip.
This method is more advantageous than the above-mentioned method for control. But
In emulsion polymerization, a large amount of
Requires emulsifiers, resulting in copolymers being smeared
However, transparency is inferior to suspension polymerization. In addition, polymerization
There is also a problem in the stability of
Often. Therefore, the heat-resistant resin used in the present invention is
It is preferably produced by suspension polymerization. In the polymerization, the reaction system is dispersed stably.
It is an industrial standard to produce polymer beads with a uniform particle size.
This is especially important in imitation. Also, depending on the compound used,
Not to color or contaminate the polymer as well
is important. For that purpose, the above (A), (B) and
And (C) or two components (B) and (C)
It is important to carry out the suspension polymerization in the presence of The component constituting the water-soluble polymer (B)
Acrylic acid represented by the general formula (1)
Examples of the derivative (III) of methacrylic acid include methacrylic acid.
Sodium salt of 2-sulfoethyl citrate, methacrylic acid
2-sulfopropyl sodium salt, 2-acrylia
Potassium salt of mido-2-methylpropanesulfonic acid
Is mentioned. As an electrolyte (C) having a monovalent cation,
For example, the use of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, etc.
Lithium, Sodium, Potassium and Ammonium Acids
Lithium salt of a lower carboxylic acid having 1 to 4 carbon atoms;
Thorium, potassium and ammonium salts; and fats
Lithium and sodium aliphatic and aromatic sulfonic acids,
And potassium and ammonium salts. The proportions of the above (A), (B) and (C) are
(A) 0 to 1 with respect to 100 parts by weight of the monomer to be subjected to turbid polymerization.
Parts by weight, (B) 0.002 to 1.0 parts by weight, (C) 0.
It is preferably from 0.05 to 10 parts by weight. (A) is used together
The stability of the reaction system can be maintained without this, but the polymer adheres to the wall
To reduce the amount of derivation and the uniformity of the particle size
Are preferably used together. (B) more preferred
The use ratio is 0.003 to 1.0 parts by weight, and 0.00
If the amount is less than 1 part by weight, the dispersing effect is insufficient.
The suspension polymerization itself can be carried out smoothly even with
However, the diversification effect does not increase so much and is not economically feasible.
No. A more preferred ratio of (C) is in the range of 0.1 to 5 parts by weight.
If the amount of electrolyte added is too small, a normal sphere
Amorphous powdery polymers besides powdery particles
The amount of derivation increases and conversely, if it is too large, the particle size increases.
The tendency to be excessive is remarkable, and finally leads to solidification. Among other known suspension methods, for example, the reaction
Polymerization is carried out in an alkaline dispersion system where the pH of the system is less than 8.
In the method, as the reaction progresses, the dispersion system becomes unstable and solidifies.
It is not easy to adopt. CMC (carboxymethyl cell
(Rose) is poor in dispersibility.
Easy to solidify when used and residue on the copolymer
An optically inferior product is obtained. Insoluble inorganic salts (for example, hydrogen phosphate calcium)
And tricalcium phosphate) and anionic surfactants
Is also an effective suspension polymerization method in which
Method, but the stability of the dispersion is poor depending on the monomer composition.
In some cases, it is necessary to perform acid cleaning,
Coalescence has a disadvantage that it is difficult to avoid contamination and coloring by the dispersant.
You. The above three components (A), (B) and (C)
Or a dispersant comprising the two components (B) and (C)
The suspension polymerization may be performed according to a conventional method. Was
For example, water, components (A), (B) and (C)
Dispersants and polymerization initiators, chain transfer agents,
Introduces a monomer that dissolves (mixes) auxiliaries such as mud dyes and pigments
And polymerize in a dispersed state with stirring. Start polymerization with monomer
The entire amount of the agent may be charged to the reactor before polymerization, or
To the monomer or polymerization start as the polymerization progresses.
The initiator may be added continuously or intermittently. Further, the resin used in the present invention is produced.
At the time, for the purpose of adjusting the molecular weight, such as mercaptan
Chain transfer agents can be used. Of the mercaptans used
Examples include alkyl or substituted alkyl groups
Primary, secondary, tertiary mercaptans; for example, n-butyl
Rumercaptan, isobutyl mercaptan, n-octy
Rumercaptan, n-dodecyl mercaptan, sec.
-Butyl mercaptan, sec. -Dodecyl mercapta
, Tert. -Butyl mercaptan, tert. -Do
Decyl mercaptan; aromatic mercaptan, for example,
Enyl mercaptan, thiocresol, 4-tert.
-Butyl-o-thiocresol; thioglycolic acid and
Esters of C3 to C1 such as ethylene glycol
8 mercaptans. These alone and
Can be used in combination of two or more. These methods
Among the rucaptans, tert. -Butyl mercaptan,
n-butyl mercaptan, n-octyl mercaptan,
n-dodecyl mercaptan and tert. -Dodecyl
Mercaptans are preferred. Where to use mercaptan
In this case, the amount used is 1 mol% or less based on the monomer.
When it exceeds 1 mol%, the molecular weight becomes small and the physical properties become poor.
descend. As the polymerization initiator to be added to the monomer, known ones
Oil-soluble materials such as peroxides
Cetyl, propionyl peroxide, butyryl peroxide, peroxide
Caprylyl, octanoyl peroxide, decanoyl peroxide,
Lauroyl peroxide, stearoyl peroxide, benzoic peroxide
Diyl, 2,4-dichlorobenzoyl, etc.
Luperoxide; t-butyl peracetate, t-butyl
Luper pivalate, t-butyl peroctanoate, t
Peresters such as -butyl perbenzoate; 2,2 '
-Azobisisobutyronitrile, 2,2'-azobis-
Azobis compounds such as 2,4-dimethylvaleronitrile
No. The polymerization temperature for carrying out the suspension polymerization depends on the weight used.
It varies depending on the type and amount of the initiator and the type of monomer.
However, it is generally in the range of 50 to 150 ° C. Ma
In addition, the weight ratio of the oil phase to the aqueous phase during suspension polymerization is oil phase /
Aqueous phase = 1/10 to 1/1, preferably
It is in the range of 1 / 1.2 to 1/3. By the above method
The resulting polymer beads are devolatilized and extruded by a known method.
It can be shaped and pelletized. Polymer beads
1% by weight or more of residual N-arylmaleimide contained therein
10 parts per 100 parts by weight of polymer beads
Wash with 0 parts by weight or more of polymer beads insoluble solvent
Thereby, coloring of the resin can be suppressed. Solvent
If the amount is less than 100 parts by weight, the cleaning effect is small.
Cleaning is possible even if it exceeds 0 parts by weight, but the cleaning effect is high.
Not economically disadvantageous. Washing temperature is from normal temperature to 100 ° C
Is used, and a range of 35 to 70 ° C. is particularly preferable.
No. Methanol, ethanol, hexane as examples of solvents
And the like. In particular, methanol is preferred.
No. In the resin used in the present invention,
And other small quantities of como
Nomer combination, plasticizer, crosslinking agent, heat stabilizer, colorant, purple
An external ray absorbing agent and a release agent can be added. [0038] The present invention will be described in more detail with reference to the following examples.
I do. Parts in Examples are parts by weight and% is% by weight.
Show. Further, both the dispersants (A) and (B) are as follows:
Synthesized. Example of synthesis of component (A) of dispersant (A-1) 30 g of methyl methacrylate, potassium methacrylate
70 g of water and 400 g of deionized water
Raise the temperature to 70 ° C while stirring under a nitrogen atmosphere in Lasco
And ammonium persulfate dissolved in 10 ml of deionized water
0.1 g was added, and the temperature was raised to 80 ° C. 6 hours later 49
0 g, diluted, cooled and polymer temperature about 10%,
A cloudy solution having a viscosity of about 370 cp (25 ° C.) was obtained. (A-2) 35 g of ethyl acrylate, ammonium methacrylate
Except for using 65g of monium, exactly the same as (A-1)
As a result, a cloudy solution having a viscosity of about 260 cp was obtained. (A-3) 25 g of butyl acrylate, potassium methacrylate
Except that 75 g is used, the viscosity is approximately the same as in (A-1).
A 190 cp cloudy solution was obtained. Synthesis Example of Component (B) in Dispersion Example (B-1) sodium of 2-sulfoethyl methacrylate
100g of salt, 900g of deionized water, 2000ml
Raise to 50 ° C while stirring under a nitrogen atmosphere in a flask
And add 0.1 g of ammonium persulfate and raise to 60 ° C.
Warmed. Cool after 6 hours and clear with viscosity about 840cp
Solution was obtained. (B-2) sodium of 2-sulfoethyl methacrylate
Except that 80 g of salt and 20 g of methyl methacrylate are used.
It becomes slightly cloudy with a viscosity of about 670 cp as in (B-1).
A solution was obtained. (B-3) Nutrition of 2-sulfopropyl methacrylate
60 g of potassium salt, 10 g of potassium methacrylate,
The same as (B-1) except that 30 g of ethyl acrylate was used.
Thus, a cloudy solution having a viscosity of about 800 cp was obtained. The evaluation of various characteristics in the examples is based on the following standards.
It was carried out based on.   VSP (Vicat Softening Point) ASTM D1525   HDT (Heat Deformation Temperature) ASTM D648   Total light transmittance ASTM D1003   Parallel light transmittance ASTM D1003   Haze value ASTM D1003   MFR (fluidity, 230 ° C, load 10kg) ASTM D1238   Tensile strength ASTM D638   Tensile elongation ASTM D638   Izod impact strength ASTM D256 Residual monomer concentration is determined by gas chromatography using standard methods.
It was measured. The color tone and transparency of the injection molded plate can be visually checked.
It was judged more. The weather resistance was measured by the accelerated exposure test (1100 hours
Suga Co., Ltd. weather tester, temperature 60 ° C, carbon
Light, 12 minutes rainfall per hour)
Was. Boiling resistance is a test piece of dimensions 2mm x 50mm x 100mm
Is immersed in pure water at 100 ° C. for 4 hours to visually determine the degree of whitening.
Specified. Evaluation of grindability was made by Takubo Seiki HD-30W
2mm x 110mm x 110mm sample using handrailer
Was carried out by a method of pressing and grinding to a grindstone surface. Embodiment 1 2700g deionized in 5000ml flask
0.27 g of water and A-1, 0.54 g of B-1 and sulfuric acid
9 g of dispersant component of sodium silicate
80 parts of related, N- (2-chlorophenyl) maleimi
12 parts, α-methylstyrene 8 parts, n-octylmer
0.14 parts of captan, 0.1% of azobisisobutyronitrile.
Charge 1800 g of a monomer solution consisting of 35 parts,
While agitating at 400 rpm with oxygen removed,
The suspension polymerization was performed by heating to 80 ° C. for 3 hours. The polymerization system is heavy
It is stable until the end of the synthesis,
Polymer adhering to the stirring blade or floating above the water surface
Almost no polymer beads were observed, and the average diameter was 0.28.
Polymer beads having a uniform particle size of mm were obtained. dehydration,
The remaining monomer of the polymer beads after drying is methylmethacrylate.
2.4% Nylate, N- (2-chlorophenyl) maleate
The mid was 0.2%. To 100 parts of the polymer beads was added methanol.
500 parts of water, stirred and heated to 40 ° C. for 1 hour,
It was filtered and dried. No secondary aggregation is observed
won. Residual monomer is less than 0.2%
Was. α-Methylstyrene was not detected. This poly
Pressing the beads at 245 ° C with a small twin screw extruder with 2 vents
It was cast, shaped and used for physical property evaluation. This pellet is colorless
It is transparent and has an intrinsic viscosity of 0.50 dl / g.
P and HDT were 140 ° C and 122 ° C, respectively.
The flowable MFR was 4.1 g / 10 minutes. Also, 25
Molded at 0 ° C and measured optical and mechanical properties
As a result, the following values were obtained. [0045] 92.0% of total light transmittance Cloudiness 0.8% Board thickness 2mm Tensile strength 618kg / cm^Two Tensile elongation 2.2% Izod impact strength 1.3kgcm / cm
(Mild notch) From the above, the physical properties of the acrylic molding material are maintained and heat resistance is maintained.
It is clear that the properties have been significantly improved. Also suck
Water content is acrylic molding material Acrypet VH (Mitsubishi Rayo
(Manufactured by Nippon Gas Co., Ltd.)
Thus, it could be advantageously used as a photon for optics. Using these pellets, a lens having a center thickness of 3 mm
Formed. Refractive index η_D= 1.514, variance ν_D= 4
9.2, transparent, no coloration and little optical distortion
No mold reversibility is good.
Was tolerable. Examples 2-3 and Comparative Examples 12 Using the same apparatus as in Example 1, the dispersant components and
Other than charging the mer phase component and setting the polymerization time as shown in Table 1.
Was subjected to suspension polymerization in the same manner as in Example 1 to obtain the results shown in Table 1.
The industrial advantages of the present invention will be clear. Examples 1 to 3 and Comparative Examples 1 to2Push
Monoglyceryl stearate is used as a release agent during dispensing.
Blend 0.1 part per 100 parts of polymer beads
did. [0048] [Table 1][0049] [Table 2]Using the pellet of Example 3, 110 × 11
Make a 0x2mm injection molded plate and evaluate the grindability
Was. No adhesion of polymer was observed, and good grindability was obtained.
Also, lens processing by grinding was possible. In addition,
Resin (Acrype manufactured by Mitsubishi Rayon Co., Ltd.)
VH), polymer deposits were observed. Examples 4 to 5 and Comparative Example3 27 kg of deionized water using a pressure-resistant polymerization kettle with an inner volume of 50 l
And various dispersion components shown in Table 2
The composition was also prepared at the ratio shown in Table 2, and 18 kg was charged to 200 parts.
While stirring at rpm, nitrogen was added at a rate of 10 l / min for 20 minutes.
After bubbling for minutes, heat to 80 ° C for the time shown in Table 2.
Suspension polymerization, and then the temperature was raised to 105 ° C and kept for 15 minutes.
Carry out post-treatment, cool, wash with water, dry and polymer beads
Got. Extrusion using the polymer beads in Example 1.
Machine to obtain pellets, and then injection molded specimens
The results are shown in Table 3 below. [0051] [Table 3][0052] [Table 4]Example 4 and Comparative Example32mm thick injection molding
An accelerated exposure test was performed using a shaped specimen, but both were
Showed almost no change in the weather resistance. Example
4 and comparative example3Using a 3mm thick injection molded specimen
A boiling test was performed, and no significant change was observed in either of them.
Boiling properties were also good. Examples 4, 5 and Comparative Example3Board
The grindability was evaluated using a 2 mm thick injection molded specimen.
Was. Comparative example3Only polymer adhering to the specimen was observed,
Was not found. [0054] According to the present invention, the optical element of the present invention comprises a resin
Has high refractive index, high heat resistance, low moisture absorption, especially
Excellent surface properties and workability required for lenses
The use atmosphere for form stability is wider than that of acrylic resin.
It can be used conveniently, for example, pickup lens,
Lens for camera, lens for camera, frame for projector
It can be used as a flannel lens or the like. In addition,
It can be used as a substrate for discs or as a core or pod for optically transmitting fibers
Used.

Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08F 212: 06)

Claims (1)

(57) [Claims] The following formula (1) 98 to 60% by weight of a methyl methacrylate unit represented by the following formula (2): (Wherein R ₁ , R ₂ , and R ₃ represent hydrogen or halogen).
A copolymer comprising 1 to 10% by weight of at least one aromatic vinyl compound unit selected from the group consisting of styrene, vinyltoluene and α-methylstyrene, and the number of moles of N-arylmaleimide the ratio β / α between α and the molar number β of the aromatic vinyl monomer is in the range of 0.2 to 5, and the intrinsic viscosity measured in chloroform at 25 ° C. is 0.3 to 1.0 dl / g. , Copolymer 100% by weight
The amount of residual N-arylmaleimide in the copolymer is
0.3% by weight or less and the total amount of residual monomers is 1.5% by weight
An optical element comprising the following heat-resistant resin.