JPS63291911A - Optical resin material - Google Patents

Abstract

PURPOSE:To obtain the titled material useful as optical fibers and lenses, having excellent heat resistance and transparency and low water absorption properties and double refraction, comprising a copolymer prepared by copolymerizing an N-substituted maleimide monomer with (meth)acrylate and a specific hydrophobic monomer. CONSTITUTION:The aimed material comprising a copolymer obtained by copolymerizing (A) 3-97wt.%, preferably 10-60wt.% N-substituted maleimide monomer (preferably N-cyclohexylmaleimide or N-isopropylmaleimide) shown by formula I (R is H, 1-15C alkyl or cyclic alkyl) with (B) 3-97wt.%, preferably 40-90wt.% compound (preferably cyclohexyl methacrylate) shown by formula II (R is H or methyl; R' is >=4C alkyl or alicyclic alkyl) and (C) 0-40wt.% hydrophobic monomer except the above-mentioned monomers and an aromatic vinyl compound.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to optical resin materials suitable for optical elements such as optical lenses, information transmission bodies such as optical fibers, peripheral devices thereof, and information recording media such as optical disks. In particular, the present invention relates to an optical resin material that can constitute an optical element that has excellent optical performance such as high transparency and low birefringence, as well as excellent heat resistance and dimensional stability when absorbing moisture.

[Prior Art] Transparent resins have been actively researched for use as materials for optical elements because they are lightweight and have excellent impact resistance, processability, and productivity. Optical resin materials are attracting attention as materials for elements such as optical fibers, optical lenses, and optical disks, and demand is rapidly expanding.

Currently, such optical resin materials include transparent resins such as polymethyl methacrylate, polystyrene, and polycarbonate, and polymers using cyclohexyl methacrylate (JP-A-58-125742, JP-A-58-11).
No. 12814, JP-A-58-5318, JP-A-511
-113214), or polymers using methyl methacrylate and tri-substituted maleimide (JP-A-81-95011, JP-A-81-141715,
JP 81-171708, JP 61-25221
No. 1, and Japanese Unexamined Patent Publication No. 80-217216).

[Problems to be solved by the invention] Especially optical video discs, digital audio discs,
In optical disk memory systems such as image file disks and write-once optical data disks, extremely high precision is required for the optical disk substrates. Therefore, as a material for disk substrates, in addition to having a high degree of heat resistance and transparency, it must also have sufficiently low birefringence, low hygroscopicity, or stability when absorbing moisture (dimensional stability, It is required to have excellent stress crack resistance, etc.).

However, although polymethyl methacrylate has low birefringence and is excellent in this respect, it has high hygroscopicity, lacks stability when absorbing moisture, and has poor heat resistance, so it cannot be used under high temperature conditions. There was a problem that it could not withstand Further, the polystyrene has low hygroscopicity and is excellent in this respect, but has problems in that it has large birefringence and poor heat resistance. Furthermore, although the polycarbonate has excellent heat resistance and moisture absorption, it has a serious drawback of having too large birefringence.

Therefore, the polymers described in the above-mentioned publications are intended to solve these problems and provide a substrate material with low birefringence that has excellent heat resistance, transparency, and hygroscopicity.
No material has yet been obtained that is satisfactory in terms of the balance of physical properties.

For example, polymers using cyclohexyl methacrylate have poor heat resistance, and methyl methacrylate and N
- Substituted ileimide copolymers have problems in transparency (particularly color tone), birefringence, etc.

Therefore, an optical resin material that satisfactorily satisfies these requirements has not yet been found, and an optical disk substrate that satisfies these requirements has not yet been obtained.

[Means for Solving the Problem] As a result of intensive studies aimed at providing a material that can manufacture high-performance optical disk substrates that satisfy the above-mentioned requirements, the present inventors discovered that a specific tri-substituted maleimide and It was discovered that a material made of a copolymer obtained from a specific hydrophobic monomer can provide molded products with excellent heat resistance, transparency, low moisture absorption, and stability when moisture is absorbed, as well as low birefringence. This invention has been achieved.

That is, the present invention provides (1) (a) a tri-substituted maleimide monomer represented by the general formula 3 to 87 weight 2;
, (b) at least one compound selected from the group consisting of compounds represented by the general formula 3 to 97 weight 2, and (c) other than the above,
The optical resin material is characterized in that it is made of a copolymer obtained by copolymerizing 0 to 40% by weight of a hydrophobic monomer other than an aromatic vinyl compound.

[Detailed Description of the Invention] The optical resin material in the present invention is a resin material used for precision optics such as optical fibers, optical lenses, automotive lamp lenses, and optical discs. Among them, an optical disk is a memory system that records and/or reproduces information using light, and specifically includes optical video disks,
Digital audio disc, image file disc,
Examples include write-once optical data disks and magneto-optical disks, and the optical resin material of the present invention is particularly useful as a mounting material for these.

(a) N-2-substituted maleimide monomer component There are no particular limitations on the N-2 substituted maleimide monomer that can be used in the optical resin material of the present invention as long as it is represented by the general formula above. However, specific examples of preferred monomers include tocyclohexylmaleimide, N-methylmaleimide, N-
Ethylmaleimide, N-n-propylmaleimide, N-
Isopropylmaleimide, n-butylmaleimide, N
-sec, -butylmaleimide, N-tsr, -butylmaleimide, N-octylmaleimide, K-laurylmaleimide, etc., and can be used alone from these groups or as a mixture of two or more types as necessary. Can be done.

Among the above compounds, tocyclohexylmaleimide, N
-Isopropylmaleimide and tomo-butylmaleimide are particularly preferred in terms of improving heat resistance.However, N-
As substituted maleimide monomers, it is not preferable to use aryl group-substituted maleimides, such as tophenylmaleimide, N-o-chlorophenylmaleimide, N-o-methylphenylmaleimide, etc. The reason is that the substituent If it is a phenyl group, the increase in birefringence is large.Secondly, the monomer itself of maleimide substituted with a 7-aryl group is highly colored, so the color tone of the resulting copolymer is extremely poor. .

In the tri-substituted maleimide monomer used in the present invention, the substituent is an alkyl group or an alicyclic alkyl group, and the problems that occur with the above-mentioned aryl group substitution do not occur at all.

The aliphatic-substituted tri-substituted maleimide monomer used in the present invention has a heat resistance improvement effect that varies depending on the type of substituent. It tends to have a large effect on improving sex. Therefore, it is difficult to easily determine the amount to be used, but it is usually used in an amount of about 3 to 97 liters, preferably 5 to 80 liters, more preferably 10 to oains. If the amount used is less than 3 weight 2, the effect of improving heat resistance will not be sufficient, and if the amount used exceeds 87 weight 2.

Depending on the type of the substituted maleimide monomer, the moldability of the resin may be reduced.

Component (b) is a hydrophobic monomer represented by the above general formula.

Here, as for the hydrophobic monomer, the water absorption rate of the homopolymer is 0.25z in a 24-hour immersion test of D570 in ^ST.
One or more monomers selected from the group consisting of monomers that provide the following polymers are preferred.

Particularly preferred examples of such hydrophobic monomers include:

Component (b) includes at least one compound selected from compounds represented by the general formula.

Particularly preferred examples of the hydrophobic monomer represented by the above general formula include cyclohexyl methacrylate, 2,2,2-trifluoroethyl acrylate,
2,2.2-trifluoroethyl methacrylate, t
-Butyl cyclohexyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, inbutyl methacrylate, bornyl acrylate, bornyl methacrylate.

Isobornyl acrylate, inbornyl methacrylate, adamantyl acrylate, adamantyl methacrylate, 9. (8)-) Recyclo[5,2,1゜02
°J Decyl 7 acrylate, 9. (8)-Tricyclo(
5,2,1,02°81 decyl methacrylate, 13
．． (+2)-pentacyclo[9,2,1,1”°8,0
2°10, 4.8. Pentadecane 7 acrylate, 13.
(12)-Pentacyclo[9,2°1.13°9.02
．． 1G, 04.8. Pentadecane methacrylate, 13
．． (12)-pentacyclo[9,2,1,1”3,02
°10°04°81 Pentadecyl acrylate, +3
．． (12)-Pentacyclo[9,2,1,13°3,0
2°10, 4°8] pentadecyl methacrylate, and the like.

Among the above compounds, cyclohexyl methacrylate, t
Most preferred are -butylcyclohexyl methacrylate, t-butylcyclohexyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, and the like.

Note that it is not preferable to use esters of acrylic acid or methacrylic acid with a phenyl group attached to the side chain as the hydrophobic monomer because the phenyl group increases birefringence.

The hydrophobicity of these hydrophobic monomers (b), that is, the effect involved in reducing the water absorption rate, varies depending on each monomer, so it is difficult to unconditionally determine the amount to be used. However, the amount is usually 3 to 87 2. Preferably 20~
Preferably, about 4G-90 weight ratio is used. If the amount used is less than 3 parts by weight, there will be no effect of improving water absorption, and if it is used in excess of 97 parts by weight, problems may occur in moldability, thermal stability, etc. depending on the hydrophobic monomer used. Sometimes.

As component (c), a monomer other than component (b) and having hydrophobicity as defined above is used. Such monomers are not particularly limited as long as they satisfy the above conditions, but examples include olefins such as ethylene, propylene, and butene, and cyclic or alicyclic monomers such as cyclohexene, cyclopentadiene, and derivatives thereof. and polar monomers such as 7-crylonitrile.

The copolymer of the present invention has a very wide range of monomer combinations and ranges. This is because the effect on the monomer varies greatly depending on the individual monomer.

Therefore, the preferred monomer composition must be determined by fully considering the individual performance of the to-substituted maleimide hydrophobic monomer used. In doing so, it is useful to take into account the following points:

That is, among the T-substituted maleimide group, those that have a large effect of improving heat resistance but cause a decrease in strength are designated as the N-1 group.
Group 12 includes those that do not have a very large effect of improving heat resistance, but do not easily cause a decrease in strength.

The N-1 group includes cyclohexylmaleimide, isopropylmaleimide, etc., and the N-2 group includes butylmaleimide, octylmaleimide, etc.

When using a to-substituted maleimide corresponding to Group 11,
Relatively low Tg (glass transition point) as the partner hydrophobic monomer
In the case of using a highly substituted maleimide corresponding to group 12, by introducing a relatively high hydrophobic monomer component of 7 g, the overall balance can be improved. It can be a resin that has been removed.

In any case, it is important to select and use the optimal monomer composition by fully considering the required overall performance.

(e) Polymerization The optical resin material of the present invention is produced by copolymerizing the above-mentioned monomer components, but there are no particular restrictions on the production method, and polymerization can be carried out by ordinary radical polymerization. At this time, it is preferable to carry out the polymerization in the presence of a radical polymerization initiator.

Radical I When polymerization is carried out in the absence of a radical polymerization initiator, problems such as generation of low molecular weight substances, coloring of the resin, and low yield are likely to occur, making the resin material undesirable as an optical resin material. Examples of the radical polymerization initiator include benzoyl peroxide, lauroyl peroxide, di-t-butylperoxyhexahydroterephthalate, t-butylperoxy-
Organic peroxidants such as 2-ethylhexanoate, azobisisobutyronitrile, azobis-reef-methoxy-2,
Azo compounds such as 4-dimethylvaleronitrile, 7zobiscyclohexanone-1-carbonitrile, azodibenzoyl, water-soluble catalysts such as potassium peroxide, and redox catalysts using a combination of peroxide or persulfate and a reducing agent, etc. There is.

In addition, a molecular weight regulator may be used for the purpose of improving the melt flowability of the copolymer. In this case, the mercaptan-based molecular weight regulator is added to the monomer, the tri-substituted maleimide monomer, and the Michael addition. Because of the reaction, it may be difficult to obtain sufficient chain transfer effects due to the nature of the two. Therefore, it is desirable to use a molecular weight modifier other than mercaptan type, and methylstyrene dimer is particularly suitable.

Typical examples of such methyl styrene dimers include 2,4-diphenyl-4-methyl-1-pentene, 2,4-diphenyl-4-methyl-2-pentene, and the like.
The amount used is usually 0.01 to 3 parts by weight, preferably 0.03 to 2.0 parts by weight, per 10 parts by weight of the monomer to be polymerized.
5 parts by weight, more preferably 2 parts by weight of O,OS9
The amount and type of molecular weight modifier are determined by F! (melt flow index) value is 2 to 70 g/10 minutes, preferably <4 to 55 g/10 minutes, more preferably 7 to 45 g
It is necessary to appropriately select and use the time within the range of /10 minutes.

If the MFI value is less than 2 g/10 minutes,
Because the resulting copolymer lacks fluidity, distortion remains in the molded product, causing increased birefringence.Also, since molding requires high temperatures, thermal decomposition of the resin occurs during molding.
It has a serious adverse effect on molded products. Also, what is the value of MFI?
If it is larger than Og/lo, the molecular weight of the resin is so small that its strength is extremely reduced, making it unsuitable for use as a molded article.

Therefore, if the melt fluidity of the resulting copolymer is within the above range, it is not necessary to use a molecular weight regulator. If the amount of molecular weight regulator used is greater than the above range, the polymerization regulator should be As the amount of residue increases, the thermal stability of the resulting resin decreases, coloration increases, and the molecular weight decreases, causing the MFI value to exceed the above range, resulting in a decrease in the mechanical strength of the molded product. This is not preferable as it may cause deterioration.

Conventionally, molecular weight modifiers used to adjust the molecular weight of polymers include mercaptan, monothiocresol, thiophenol, thioglycol-2-ethylhexyl, and β-naphthalenethiol.

However, these molecular weight modifiers have a strong odor, and the obtained polymer also has a smell that is generally called a musty smell to varying degrees, which may pose a practical problem.

Furthermore, in a polymerization system in which a tri-substituted maleimide is an essential component as in the present invention, molecular weight controlling agents of the type that undergo chain transfer by abstracting hydrogen, such as the above-mentioned thiols, have little effect in controlling the molecular weight. This is because it is a substituted maleimide with a molecular weight of 21! ! The thiol of the agent is consumed in reactions other than the chain transfer reaction due to the Michael addition reaction, and it is necessary to add a large amount of thiol in order to use it as a molecular weight regulator. This is because it will cause serious defects to the However, when methylstyrene dimer is used as the molecular weight 11g1 agent, the above-mentioned defects do not occur, which is extremely advantageous.

1j≦L As the polymerization method, various polymerization methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization can be applied.
Bulk polymerization and solution polymerization methods are preferred in terms of avoiding contamination with emulsifiers and suspension stabilizers.

In the present invention, the conditions for polymerizing the monomer are as follows:
Generally at a temperature of 0 to 200°C, preferably eo to 150°C, generally 0 to 20 kg/c2, preferably 0 to I
It is carried out under a pressure of Q kg/c 2.

(d) Optical resin material A copolymer produced by a polymerization method with the above monomer, that is, an optical resin material of the present invention, generally has a molecular weight of 7.
o, ooo~1. OOO,000, preferably 10.0
00 to soo, ooo, it is a random or block copolymer of a to-substituted maleimide monomer and a hydrophobic monomer, and the structural formula of the to-substituted maleimide monomer and the hydrophobic monomer are It is represented by the following general formula in which structural formula (A) is combined randomly or in blocks.

(However, 1 and n in the formula represent the number of repeating units.)

In addition, materials suitable as optical resin materials usually have an all-party transmittance of 75 to 100! , preferably 85-100!
and the birefringence is usually 0.1 to 50 mm, preferably 0.2
~10mm, heat deformation temperature is usually 100~20G ”0
, preferably 120 to 170°C, water absorption rate usually 0.02
-0.25%, preferably 0.05-0.15%.

The optical resin material of the present invention can be molded into various molded products by conventional methods. That is, the copolymer can be used to form optical elements such as optical lenses, video discs, audio discs, and image file discs into predetermined shapes and dimensions depending on the purpose.

Molding methods for these optical elements include injection molding, compression molding, and extrusion molding, but injection molding is usually used. In the case of injection molding, the temperature of the cylinder of the injection molding machine is usually 200 to 320°C, preferably 1 L < I
t 220A-300"O, mold temperature 40-120
℃, preferably 50 to 100°C.

The optical resin material of the present invention may contain light stabilizers such as ultraviolet absorbers, heat stabilizers such as antioxidants, and the like, if necessary. Further, other polymers may be mixed and used within a range that does not impair the effects of the present invention.

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

Ryo 19 Sa 2 11 To 100 parts by weight of the monomer mixture having the composition shown in Table 1, 70 parts by weight of toluene and 0.5 parts by weight of azobisisobutyronitrile were added, and 6 parts by weight were added at 75°C. By time copolymerization, copolymers J-I NJ-5 and H-IN) 143 shown in Table 1 were obtained.

- Examples 1 to 5 Copolymers J-1 to J-5 produced by the above method were injection molded by setting the cylinder temperature of the injection molding machine to 270'O1 and the mold temperature to 70'0. Each physical property was measured using the molded product.

Table 2 shows the measurement results.

Comparative Examples 1 to 65 Copolymers produced by the method described in L)! -1,)I-2,H
-3, Styron 668 (polystyrene manufactured by Asahi Kasei ■), 0F100O (Kyowa Gas Chemical ■ polymethyl methacrylate), and S-2000-F (polycarbonate manufactured by Mitsubishi Gas Chemical ■) were tested in the same manner as in the above example. Physical properties were measured.

In addition, for S-2000-F, the cylinder temperature is 32
Molding was carried out at 0°C and a mold temperature of 80°C.

The measurement results are shown in Table-2.

In addition, each physical property was measured by the following method.

Heat distortion temperature: Measured according to STM 0-848-58.

MFI: Measured according to ASTM D-1238.

Total light transmittance, haze value: Measured according to ASTM D-1003.

Water absorption rate: Measured according to ASTM D-570.

Yellowness: Measured according to JIS Z-870.

Birefringence (optical path difference) nm: Vertical 8C by injection molding
A plate having a structure E of 1 cm and a thickness of 2.4 mm was molded, and the birefringence at its center position was measured using an automatic ellipsometer manufactured by Shoten Kogaku Kogyo.

The following is clear from the results of Examples and Comparative Examples. That is, copolymers within the scope of the present invention (J-1 to j-
The molded article consisting of 5) has excellent heat distortion temperature, transparency, and water absorption, and has low birefringence.

In contrast, polymethyl methacrylate (OFlooO)
A molded product made of polystyrene (Styron 88B) has a low heat distortion temperature and a high water absorption rate, and a molded product made of polystyrene (Styron 88B) has a poor heat distortion temperature and birefringence. Furthermore, molded products made of polycarbonate (S-2000-F) have excellent heat distortion temperature and water absorption, but have large birefringence.

In addition, when a monomer having an aromatic substituent is used or when a doarylmaleimide is used), the birefringence increases, and the yellowness increases. As a result, the color tone deteriorates (H-2).

[Effects of the Invention] As explained above, the optical resin material of the present invention has excellent properties such as excellent heat resistance and transparency, and low water absorption and birefringence, and has a good balance of physical properties. As an excellent optical element material, it is used for information transmission bodies such as optical fibers and optical lenses and their peripheral devices, optical disks such as optical video disks, digital audio disks, image file disks, write-once optical data disks, and magneto-optical disks. It is an optical resin material that can be used for optical memory systems, automotive lamp lenses, etc., and is extremely acceptable industrially.

Claims (4)

[Claims] (1) (a) General formula ▲ Numerical formula, chemical formula, table, etc. ▼: [In the formula, R represents a hydrogen atom, an alkyl group having 15 or less carbon atoms, or a cyclic alkyl group] N-substituted Maleimide monomer 3-97% by weight, (b) General formula ▲ Numerical formula, chemical formula, table, etc. ▼ [In the formula, R is hydrogen or a methyl group, and R' has 4 carbon atoms.
Indicates the above alkyl group or alicyclic alkyl group. ] Copolymerization of 3 to 97% by weight of at least one compound selected from the group consisting of compounds represented by the following and (c) 0 to 40% by weight of a hydrophobic monomer other than the above and other than an aromatic vinyl compound. An optical resin material comprising a copolymer obtained at least. (2) 0.01 to 3 parts by weight of methylstyrene dimer is present per 100 parts by weight of the mixture of the N-substituted maleimide monomer and the hydrophobic monomer during copolymerization, according to claim 1. The optical resin material described above. (3) The hydrophobic monomer has a homopolymer water absorption rate of AS
Claim 1 or 2 is at least one compound selected from the group consisting of monomers that give a polymer with a TMD570 of 0.25 or less in a 24-hour immersion test.
The optical resin material described in . (4) The optical product according to any one of claims 1 to 3, which has a melt flow index value of 2 to 70 g/10 minutes at a temperature of 100° C. added to the glass transition point. resin material.