JPS63215706A - Resin lens material having high refractive index - Google Patents

Abstract

PURPOSE:To provide the title material having a high refractive index, a low optical dispersibility and a low specific gravity and excellent in transparency, solvent resistance and surface hardness, which comprises a (castable) copolymer of two specific monomers and (alpha-methyl)styrene. CONSTITUTION:40-70wt.% monomer (A) [e.g., 2,2-bis-(4-acryloxyethoxy-3,5- dibromophenyl)propane] of formula I (wherein R<1-2> are each H or 1-2C alkyl; and m and n are each 0-4) plus monomer (B) (e.g., acryloxyethoxy-2,4,6- tribromobenzene) of formula II (wherein R<3> is R<1>; p is 1-5; and q is 1-4 representing the number of substituted bromine atoms, with (A) being 20-60wt.% and (B) being 10-20wt.%, 5-40wt.% (alpha-methyl)styrene of formula III (wherein R<4> is H or CH3) and, if desired, 0-45wt.% other monomer [e.g., isobutyl (meth)acrylate] polymerizable with them are, if desired, poured into a casting vessel having a desired shape, and copolymerized in the presence of a radical polymerization initiator.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a high refractive index resin lens material, particularly a high refractive index resin lens material that has a high refractive index, excellent low optical dispersion, and has a small specific gravity. It is something.

[Prior art]

Traditionally, inorganic glass lenses have been widely used as eyeglass lenses for vision correction or as lenses for optical equipment, but recently lenses made of resin have become more popular due to their light weight, impact resistance, workability, and stability. , dyeability, mass productivity, low cost, and other advantageous features.
It is beginning to be widely used in conjunction with inorganic glass lenses.

Materials for optical lenses are required to have various physical properties, but it is particularly important to have a high refractive index, low optical dispersion, and low specific gravity. In other words, if the lens used is made of a material with a high refractive index and low specific gravity, the lens system, which plays an important role in optical equipment such as microscopes, cameras, and telescopes, and lenses for eyeglasses, can be made compact. Not only can the weight be reduced, but also spherical aberrations can be suppressed, and if the lens material has a low degree of optical dispersion, a lens with little chromatic aberration can be obtained.

Generally, in resin lenses, there is a tendency that those with a high refractive index have high optical dispersion, and those with a low refractive index have low optical dispersion, similar to inorganic glass lenses. for example,
Diethylene glycol bisallyl carbonate (hereinafter referred to as rcI?-39J) is a lens material that is currently popular as a synthetic resin lens for eyeglasses.
Although OCR-39 has a large Abbé number of C60 (that is, low optical dispersion), its refractive index is extremely low at n=1.50. Polymethyl methacrylate, which is used as a material for some lenses, is also CR-
Similar to No. 39, the Atsbe number is large at 60, but the refractive index is low at n=1.49.

Furthermore, polystyrene, which is said to have a relatively high refractive index and low optical dispersion, has f1%ff = 1.59 and ν = 30.4, and polycarbonate has n = 1.59 and c = 29.5, but is necessary as a lens material. For example, polystyrene has poor surface hardness and solvent resistance, and has no dyeability at all.

Polycarbonate also has poor surface hardness and impact resistance. Furthermore, polynaphthyl methacrylate, which has a high refractive index, has n=1.64 and polyvinylnaphthalene has n=1.68, but the Atsube number is ν=2.
4 and ν=20, both of which are small and have high optical dispersion.

Recently, halogen-substituted bisphenol A derivatives have been used as lens materials with high refractive index, for example, in JP-A-58-28117 and JP-A-57-5490.
This has been proposed in Publication No. 1, etc. However, although the copolymers disclosed in these publications have a high refractive index, they do not necessarily have sufficiently low optical dispersion. Furthermore, the copolymer described in JP-A-58-176691 is an excellent resin lens material in terms of high refractive index and low optical dispersion, but its specific gravity is somewhat high, which limits its use in some fields. There are some problems.

[Purpose of the invention]

The present invention was made based on the above circumstances, and its purpose is to have a high refractive index, low optical dispersion, low specific gravity, high transparency, and solvent resistance. We also provide excellent resin lens materials.

The resin lens material of the present invention comprises a specific copolymer, that is, more than 20% by weight and 60% by weight or less of a monomer (I) represented by the following general formula (I), and a monomer (I) represented by the following general formula (II). 10% by weight or more and less than 20% by weight of monomer (II) represented by the following general formula (III), and 5% by weight or more and 40% by weight or less of monomer (I) represented by the following general formula (III), Special general formula (I) characterized in that it consists of a copolymer in which the total of monomer (I) and monomer (U) is more than 40% by weight and less than 70% by weight, where R1 and R'' Each of is a hydrogen atom or an alkyl group having 2 or less carbon atoms, and m and n are integers of θ to 4.

General Formula (II) In the formula, R3 is a hydrogen atom or an alkyl group having 2 or less carbon atoms, p is an integer of 1 to 5, and q is the number of substituted bromine atoms, which is an integer of 1 to 4.

General formula (I[[) In the formula, R4 is a hydrogen atom or a methyl group.

〔effect〕

The copolymer for the resin lens material of the present invention has a composition in which the total amount of the monomer (I) and the monomer is more than 40% by weight and less than 70% by weight, and a monomer with a small specific gravity. Since the proportion of monomer (III) is 5 to 1%, the properties of high refractive index and low optical dispersion due to monomer (I) and monomer (I[) are not sacrificed. monomer (
The advantage of low specific gravity according to III) is realized, and thereby a resin lens with the desired excellent characteristics can be obtained.

That is, according to the resin lens material of the present invention, it is possible to obtain a resin lens that has high surface hardness, solvent resistance, and refractive index, low optical dispersion, and low specific gravity, and has a good balance of properties as a whole. For example, if the refractive index is "W"
-1.58 or more, optical dispersion ν=30 or more, specific gravity ρ
A resin lens in which ≦1.5 is obtained can be obtained. On top of that,
The resin lens material of the present invention also has good dyeability.

In addition, the above monomer (I) is solid at room temperature, and the monomer (formerly, it is a viscous liquid at room temperature, but it is used as monomer (I[[) Since both styrene and α-methylstyrene are highly fluid liquids at room temperature, it is possible to form a monomer mixture containing this monomer (Illr) into a liquid with a low viscosity as a whole. Therefore, it is easy to handle and can be directly subjected to cast polymerization, allowing resin lenses to be manufactured easily and at low cost.

The present invention will be specifically explained below.

The copolymer for the resin lens material of the present invention comprises the following monomers (I) to (III) as essential components.

Monomer (I), which is the first component of the Kishi jL (LLLL copolymer), is a monomer of t+R' and R2, which is usually a white crystalline monomer at room temperature and is represented by the above general formula (I). Each is a hydrogen atom or an alkyl group having 1 or 2 carbon atoms.When the alkyl group has 3 or more carbon atoms, the resulting copolymer has a low refractive index.

m and n are integers from 0 to 4, and the smaller these values, the greater the surface hardness of the produced copolymer, so depending on the intended use of the resulting lens,
0m and n whose values are selected from the range 0 to 4
On the other hand, if it is 5 or more, the resulting copolymer will have low surface hardness, which is undesirable.
In H, R1 and R'' and m and n may be the same or different.

Specific examples of monomers include 2.2-bis-(4-acryloxyethoxy-3,5-dibromophenyl)propane, 2.2-bis-(4-methacryloxyethoxy-
3,5-dibromophenyl)propane, 2,2-bis-
(4-acryloxyjethoxy-3,5-dibromophenyl)propane, 2,2-bis-(4-methacryloxyjethoxy-3,5-dibromophenyl)propane, 2
,2-bis-(4-acryloxytriethoxy-3,5
-dibromophenyl)propane, 2,2-bis-(4-
Methacryloxytriethoxy-3,5-dibromophenyl)propane, 2,2-bis-(4-acryloxytetraethoxy-3,5-dibromophenyl)propane, 2
．． 2-bis-(4-methacryloxytetraethoxy-3
, 5-dibromophenyl)propane, or a mixture thereof.

Kodansei (II) The second monomer component, the monomer (II), is the above-mentioned -l'
IQ is a monomer represented by formula (II), and the value of p in the formula has an important influence on the properties of the copolymer as a lens material, and if the value is 5 or more, the formation These copolymers tend to have low surface hardness and low refractive index. Therefore, an integer between 1 and 4 must be selected as the value of p. In addition, the value of q in the formula is the factor that has the greatest influence on the refractive index of the copolymer produced, and this q
By changing the value in the range of 1 to 5, it is possible to design a resin lens with a refractive index depending on the purpose of use.

Specific examples of the monomer (U) include acryloxyethoxydibromobenzene, methacryloxyethoxydibromobenzene, acryloxyethoxy-2,4,6-dribromobenzene, methacryloxyethoxy-2,4,
6-dribromobenzene, acryloxyjethoxy-2
, 4,64 ribromobenzene, methacryloxyethoxy-2,4,6-1 ribromobenzene, acryloxyethoxy-4-bromobenzene, methacryloxyethoxy-
Examples include 4-bromobenzene, acryloxyethoxypentabromobenzene, methacryloxyethoxypentabromobenzene, and mixtures thereof.

Monomer (III), which is the third component of the 厘1''(Fu''L) copolymer, is a monomer consisting of either styrene or α-methylstyrene, or a mixture of both. (I[[)
When polymerized alone, the refractive index is nW=1.59
, gives a polymer with an Atsube number of about C29, has a lower refractive index than monomer (I) or monomer (II), and has an insufficient degree of optical dispersion. be.

However, as in the present invention, the monomer (Ill
) is combined with monomer (I) and monomer (II) within the range of 5 to 40% by weight, the following effects are produced.

(I) In the copolymer produced, for example, refractive index n2,
It is possible to reduce the specific gravity to an extremely small value of ρ≦1.5 while ensuring excellent optical properties such as O, lJ or more and an Atsbe number C of 30 or more.As a lens material, it is a lens material that has a good overall balance of physical properties. Polymers can be obtained.

(2) It becomes possible to handle the mixture of monomer (I) and monomer (II) as a liquid at room temperature,
It is extremely convenient to use the cast polymerization method.

When a mixture of styrene and α-methylstyrene is used as the monomer (III), the polymerization reaction rate decreases as the proportion of α-methylstyrene increases; The moldability of the lens obtained is improved, and excellent dimensional accuracy, surface roughness, and gloss are obtained. Therefore, by selecting the proportion of α-methylstyrene, it is possible to obtain a resin lens with characteristics depending on the intended use of the resin lens.

In the present invention, in addition to the above three monomers, a monomer copolymerizable with them can be used as a component of the above copolymer within a range of 0 to 45% by weight. .

However, it goes without saying that monomers that have an unacceptable adverse effect on the refractive index, optical dispersion, specific gravity, etc. of the resulting copolymer should not be used.

Specific examples of such monomers include alkyl esters of acrylic acid or methacrylic acid (the number of carbon atoms in the alkyl group is preferably 1 to 6) such as isobutyl acrylate, isobutyl methacrylate, n-butyl acrylate, and n-butyl methacrylate. ), polyfunctional acrylic acid or meccrylic acid esters such as ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, divinylbenzene, vinylnaphthalene, etc. Examples include aromatic vinyl compounds, allyl compounds such as allyl cinnamate, diallyl tucrate, and triallyl cyanurate, and others.

The proportion of the above-mentioned monomer (I) is set to be more than 20% by weight and less than 60% by weight of the total monomers, and preferably within the range of 40% by weight to 60% by weight. The proportion of monomer (II) is 10% by weight or more and less than 20% by weight of the total monomers, but it is particularly preferably within the range of 15 to less than 20% by weight. The total amount of monomer (I) and monomer (II) must be more than 40% by weight and less than 1% by weight of the total monomers, especially 55% by weight to 70% by weight. It is preferable that it is within the range of .

The proportion of monomer (I[[) is 5% by weight or more of the total monomers4
0% by weight or less, but especially 15 to 35% by weight
It is preferable that it is within the range of .

By using both monomer (I) and monomer (II) as essential components of the copolymer as described above, the following effects can be obtained. That is, monomer (II
), the homopolymer has low solvent resistance and low surface hardness because the monomer (II) is -functional. To improve this,
It is effective to combine monomer (II) with various crosslinkable monomers, but when ordinary crosslinkable monomers are used, monomer (II) has a high refractive index and a low The resulting copolymer will no longer have the property of optical dispersion.

However, monomer (I) is a crosslinkable monomer that is highly copolymerizable with monomer (II), and surprisingly, the resulting copolymer has a high refractive index and It has low optical dispersion, which was discovered as a result of searching for a large number of crosslinkable monomers.

Furthermore, the copolymer for the resin lens material of the present invention has the advantage of having good dyeability, and this is thought to be because it contains the monomer (II) which itself is rich in dyeability.

The proportion of monomer (I) is set to be more than 20% by weight and less than 60% by weight of the total monomers, but if the proportion of monomer (II) is too large, the monomer composition may be polymerized. This is not preferable because the surface hardness decreases and high surface hardness cannot be obtained. Further, when the sum of monomer (I) and monomer (I[) is 1% or less, the resulting copolymer has the advantage of having a high refractive index and low optical dispersion.

If the sum becomes more than 70 times,
The resulting copolymer has a high specific gravity, and the monomer composition has a high viscosity (which makes it difficult to handle).

In addition, by using the monomer CI [[) within the range of 5 to 40% by weight, the specific gravity can be reduced without impairing the characteristics of high refractive index and low optical dispersion, as described above. At the same time, it becomes easy to handle the monomer curved product, and it becomes possible to use the cast polymerization method.

Further, by using other copolymerizable monomers, the properties of the produced copolymer can be adjusted, but the proportion thereof is 45% by weight or less, preferably 40 times or less. When this ratio is large, a copolymer with good balance of properties cannot be obtained.

The copolymer according to the resin lens material of the present invention is produced by polymerizing an appropriate mixture or composition of the above monomers, and this polymerization can be carried out using a conventional radical polymerization initiator. As for the polymerization method, a method used in ordinary radical polymerization can be used. However, since the copolymer produced is crosslinked, it is virtually impossible to perform any treatment that involves melting or dissolving it, so resin lenses can be produced directly by casting polymerization using a casting container. It is desirable to do so.

As this cast polymerization method, well-known techniques can be used as they are. As the casting container, plate-shaped, lens-shaped, cylindrical, prismatic, conical, spherical, or other molds or molds designed according to the purpose are used. The material may be any suitable material such as inorganic glass, plastic, or metal.

In the case of casting polymerization, jl-mer (I) to monomer (I[l) and other monomers added as necessary are mixed into a suitable casting container. Alternatively, they may be added separately together with a polymerization initiator, and polymerization may be carried out by heating as necessary. However, it is also possible to carry out a certain degree of polymerization in a separate container, and then charge the obtained prepolymer or syrup into a casting container to complete the polymerization. Each monomer and polymerization initiator may be mixed in their entire amounts at once, or may be mixed in stages. The mixture may also contain antistatic agents, colorants, fillers, ultraviolet absorbers, antioxidants, heat stabilizers, and other auxiliary materials, depending on the intended use of the resulting lens.

Another example of an advantageous polymerization method is a suspension polymerization method in which a mixture or prepolymer of each monomer and a polymerization initiator is suspended in water and polymerization is carried out.

This method is suitable for obtaining spherical lenses of various particle sizes. When using this suspension polymerization method, two methods are possible: using well-known techniques as they are.

The resulting copolymer is heated to complete any incomplete polymerization or to increase its hardness, or to remove any strain that may exist within the copolymer using a cast polymerization method. Needless to say, annealing and other post-treatments can be performed to remove the particles.

The resin lens material of the present invention is not different from conventional resin lens materials in wood quality, except that it is made of a copolymer made of specific monomer components. Therefore, a resin lens can be obtained directly by the cast polymerization method as described above, or a resin lens can be obtained by cutting out a lump of the copolymer. By subjecting the resulting resin lens to surface polishing, antistatic treatment, and other post-treatments as necessary, the inherent properties of the resin lens can be further improved or improved. period characteristics can be assigned.

Furthermore, in order to increase the surface hardness of the resin lens, it is of course possible to coat the surface of the resin lens with an inorganic or organic hard coating agent by means such as dipping, and further to apply a non-reflective coating.

〔Example〕

Examples of the present invention will be described below, but the present invention is not limited thereto.

Example 1 2.2-bis-(4-methacryloxyethoxy-3,5
-dibromophenyl)propane...47 parts by weight 1-acryloxyethoxy-2,4,6-dribromobenzene...18m [U styrene
...20 parts α-methylstyrene
...15 parts by weight or more of the substance, 1 part by weight of lauroyl peroxide as a polymerization initiator, and 0.5 parts of ultraviolet absorber "Tinuvin 328J (manufactured by Ciba Geigy)"
parts by weight were added to obtain a mixture.

This mixture was poured into a glass container, thoroughly degassed and replaced with nitrogen gas, and then heated at a temperature of 50°C for 1 hour at a temperature of 60°C.
Polymerization was completed by changing the reaction temperature for 15 hours at 80° C., 2 hours at 110″C, and 1 hour at 110″C.

The copolymer thus obtained was almost colorless and transparent, and completely insoluble in organic solvents such as ethanol, acetone, methyl ethyl ketone, tetrahydrofuran, and toluene.

In addition, the surface hardness of this copolymer was measured according to the pencil hardness specified in JIS K-5400, the refractive index and Atsube number at a temperature of 20°C were determined by measurement using an Arahe refractometer, and the specific gravity at a temperature of 20°C was determined. automatic hydrometer DSj
(manufactured by Toyo Seiki Co., Ltd.), the following results were obtained.

Surface hardness: 2H Refractive index: n = 1.601 Atsube number = 31.1 Specific gravity: ρ = 1.431 As is clear from the above results, this copolymer has excellent optical properties. It is a well-balanced resin lens material with a low specific gravity.

Further, after the surface of the lens body made of the copolymer obtained as described above is treated with alkali, the surface of the lens body is coated with a commercially available silicone hard coating agent by a dipping method to obtain a resin lens. Ta. The surface hardness of this resin lens, determined in the same manner as above, was as high as 3H, and the adhesion of the hard coat layer to the lens body was also sufficient. No separation was allowed at all.

As described above, the resin lens material of the present invention is also excellent in terms of hard coat coverage.

Example 2 2.2-bis-(4-methacryloxyethoxy-3,5
-dibromophenyl)propane...55 parts by weight 1-acryloxyjethoxy-2,4,6-)lipromobenzene...15 parts by weight Styrene...20 parts by weight α-methylstyrene...10 parts by weight 0.5 part by weight of the ultraviolet absorber "Tinuvin 328" in the substance of Sebe and above,
0.5 parts by weight of the antioxidant "Irganox 245" (manufactured by Ciba Geigy) was added, 1 part by weight of lauroyl peroxide was added as a polymerization initiator, and this mixture was polymerized according to the method of Example 1. A copolymer was obtained.

The copolymer thus obtained was almost colorless and transparent, and completely insoluble in existing solvents such as ethanol, acetone, methyl ethyl ketone, tetrahydrofuran, and toluene.

In addition, the surface hardness, refractive index and Atsube number of this copolymer,
When the specific gravity was measured in the same manner as in Example 1, the following results were obtained.

Surface hardness = 2H Refractive index: n = 1.601 Atsube number = 31.8 Specific gravity: ρ = 1.462 As is clear from the above results, this copolymer has excellent optical properties. It is a well-balanced resin lens material with a low specific gravity.

Example 3 2.2-bis-(4-methacryloxyethoxy-3+5
-dibromophenyl)propane...40 parts by weight 1-acryloxyethoxy-2,4,6-dribromobenzene...15 parts by weight Styrene
...15 parts by weight α-methylstyrene
...15 parts by weight of isopropenylnaphthalene ...15 parts by weight or more of substances, 1 part by weight of lauroyl peroxide as a polymerization initiator, 5 parts by weight of the ultraviolet absorber Tinuvin 328J O, and an antioxidant [
5 parts by weight of Irganox 245J O was added to obtain a mixture.

This mixture was poured into a glass container, thoroughly degassed and replaced with nitrogen gas, and then heated at a temperature of 50°C for 2 hours at a temperature of 60°C.
Polymerization was completed by changing the reaction temperature for 20 hours at -80°C, 6 hours at 110°C, and 1 hour at 110°C.

The copolymer thus obtained was almost colorless and transparent, and completely insoluble in organic solvents such as ethanol, acetone, methyl ethyl ketone, tetrahydrofuran, and toluene.

In addition, the surface hardness, refractive index and Atsube number of this copolymer,
When the specific gravity was measured in the same manner as in Example 1, the following results were obtained.

Surface hardness: 2H Refractive index = n-1,61 Atsube number = 30.3 Specific gravity: ρ = 1.476 As is clear from the above results, this copolymer has excellent optical properties. It is a well-balanced resin lens material with a low specific gravity.

Comparative Example 1 2.2-bis-(4-methacryloxyethoxy-3,5
-dibromophenyl)propane...55 parts by weight 1-acryloxyethoxy-2,4,6-dribromobenzene...18 parts by weight Styrene
...15 parts by weight α-methylstyrene
...12 parts by weight or more of a substance, one part of lauroyl peroxide as a polymerization initiator, and an ultraviolet absorber [Tinuvin 3284 (manufactured by Ciba Geigy) 0.5
parts by weight were added to obtain a mixture.

This mixture was in a much more viscous liquid form at room temperature than that of Example 1, and it was difficult to directly apply it to the cast polymerization method at room temperature. The mixture was poured into a glass container in a state where the temperature was lowered, and after sufficiently degassing and purging with nitrogen gas, the mixture was heated at a temperature of 50°C for 1 hour, at a temperature of 60°C for 15 hours, and at a temperature of 80°C for 2 hours.
Polymerization was completed by varying the reaction temperature at 0° C. for 1 hour.

The copolymer thus obtained was almost colorless and transparent, and completely insoluble in organic solvents such as ethanol, acetone, methyl ethyl ketone, tetrahydrofuran, and toluene.

In addition, the surface hardness, refractive index and Atsube number of this copolymer,
When the specific gravity was measured in the same manner as in Example 1, the following results were obtained.

Surface hardness: 2 H Refractive index; n = 1.602 Atsube's number = 30.2 Specific gravity: ρ = 1.523 As is clear from the above results, this copolymer is similar to the copolymer of Example 1. Although the optical properties are comparable to those of fused resin, it has a high specific gravity and is not a well-balanced resin lens material. Moreover, when using the cast polymerization method, it is necessary to raise the temperature, so it is difficult to know how to manufacture it. 4A will be mixed and the cost will be high.

Comparative Example 2 2.2-bis-(4-methacryloxyethoxy-3,5
-dibromophenyl)propane...35 parts by weight 1-acryloquine-ethquine-2,4,6-dribromobenzene...15 parts by weight Styrene
...25 parts by weight α-methylstyrene
...25 A substance with a weight of 11B or more, a polymerization initiator containing lauroyl peroxide, and an ultraviolet absorber "Tinuvin 328J (manufactured by Ciba Geigy) 0
．． 5 parts by weight were added to obtain a mixture.

This mixture was poured into a glass container, thoroughly degassed and replaced with nitrogen gas, and then heated at a temperature of 50°C for 1 hour at a temperature of 60°C.
Polymerization was carried out by changing the reaction temperature: 15 hours at 80° C., 2 hours at 110° C., and 1 hour at 110° C.

The thus obtained copolymer was almost colorless and S-light, and was completely insoluble in 89WJ media such as ethanol, acetone, methyl ethyl ketone, tetrahydrofuran, and toluene.

In addition, the surface hardness, refractive index, and number of this copolymer,
When the specific gravity was measured in the same manner as in Example 1, the following results were obtained.

Surface hardness: HB Refractive index: n = 1.579 Atsube's number -29.8 Specific gravity: ρ = 1.395 As is clear from the above results, this copolymer is the same as the copolymer of Example 1. Although it has a lower specific gravity, it has inferior optical properties and has a lower surface hardness, so it is not a well-balanced resin lens material.

Claims (1)

[Scope of Claims] 1) More than 20% by weight of a monomer (I) represented by the following general formula (I) and not more than 60% by weight, and a monomer (II) represented by the following general formula (II) 10 5% to 40% by weight of monomer (III) represented by the following general formula (III), monomer (I) and monomer ( A high refractive index resin lens material comprising a copolymer in which the total amount of II) is more than 40% by weight and less than 70% by weight. General formula (I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ In the formula, each of R^1 and R^2 is a hydrogen atom or an alkyl group having 2 or less carbon atoms, and m and n are integers from 0 to 4. be. General formula (II) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ In the formula, R^3 is a hydrogen atom or an alkyl group having 2 or less carbon atoms, p is an integer from 1 to 5, and q is the number of substituted bromine atoms. and is an integer from 1 to 4. General formula (III) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ In the formula, R^4 is a hydrogen atom or a methyl group.